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Deepwater Horizon

BP's Gulf of Mexico response website BP's Deepwater Horizon Accident Investigation Report
Also called the "Bly Report". On September 8, 2010, BP released a report entitled "Deepwater Horizon Accident Investigation Report," an internal analysis of the April 20, 2010 blowout that killed 11 people and resulted in a massive oil spill in the Gulf of Mexico. The report was prepared by an internal investigation team selected by BP.
The report identified eight key findings related to the cause of the accident:
  1. The annulus cement barrier did not isolate the hydrocarbons.
  2. The shoe track barriers did not isolate the hydrocarbons.
  3. The negative-pressure test was accepted although well integrity had not been established.
  4. Influx was not recognized until hydrocarbons were in the riser.
  5. Well control response actions failed to regain control of the well.
  6. Diversion to the mud gas separator resulted in gas venting onto the rig.
  7. The fire and gas system did not prevent hydrocarbon ignition.
  8. The BOP emergency mode did not seal the well.
Deepwater Horizon Joint Investigation

Coast Guard and Department of Interior

The Official Site of the Joint Investigation Team

The purpose of this joint investigation is to develop conclusions and recommendations as they relate to the Deepwater Horizon MODU explosion and loss of life on April 20, 2010. The facts collected at this hearing, along with the lead investigators' conclusions and recommendations will be forwarded to Coast Guard Headquarters and BOEM for approval. Once approved, the final investigative report will be made available to the public and the media.
USCG -Report of Investigation into the Circumstances Surrounding the Explosion, Fire, Sinking and Loss of Eleven Crew Members Aboard the MOBILE OFFSHORE DRILLING UNIT DEEPWATER HORIZON In the GULF OF MEXICO April 20 22, 2010

Key investigative findings:
  • Initial flow should have been routed through the diverter line.
  • The Deepwater Horizon lacked systems to properly track its hazardous electrical equipment, some of which board was in bad condition and severely corroded.
  • Gas detectors were not set to automatically activate the emergency shutdown (ESD) system for the engines or to stop the flow of outside air into the engine rooms. The bridge crew was not trained on when to activate the ESD systems.
  • Some gas detectors were bypassed or inoperable.
  • Emergency generators were not sufficiently isolated from the main power system.
  • Blast protection was insufficient to protect the crew. Bulkheads were not sufficiently fire resistant.
  • The dual command structure on the DWH between the Master and the OIM caused confusion at a critical point in the emergency.
  • No fire pump capability (no diesel backup) once electrical power was lost.
  • Emergency evacuation procedures were not followed; drills were inadequate.
  • The presence of executives onboard was a distraction.
  • No effective barrier to shield the lifeboat launch area from intense heat.
  • The presence of the Damon Bankston standby vessel no doubt saved lives.
  • DWH was not in compliance with requirements for maintaining the watertight integrity of its internal compartments
  • Massive quantities of water were directed toward the DWH without careful consideration of the potential effects of water entering the hull.
  • Pursuant to its Search and Rescue Policy, the Coast Guard prioritized search and rescue efforts and thus did not take charge of, or coordinate, the marine firefighting effort.
  • Transocean had a history of International Safety Management Code violations.
  • The DWH BOP had not been recertified for over ten years. Key BOP components had significantly surpassed the recommended recertification period and needed to be replaced.
  • In 2008, the DWH had two significant incidents a loss of power that jeopardized the MODUs ability to maintain its position above the well and the flooding of a compartment resulting from a failure to close valves. Neither of these incidents was properly investigated and addressed.
  • Transoceans training and emergency response preparedness were deficient. The master was unaware that he could activate the critical emergency disconnect sequence (EDS).
  • The flag state, Republic of the Marshall Islands (RMI), failed to directly ensure that DWH was in compliance with all applicable requirements, including those relating to the electrical equipment in hazardous zones, degradations in watertight integrity, crew training, emergency preparedness, and others.
  • The Coast Guard conducted limited safety examinations of DWH in 2008 and 2009, but did not identify safety concerns.
  • Given the flag states oversight deficiencies, the Coast Guards regulatory scheme, which defers heavily to the flag state to ensure the safety of foreign-flagged MODUs, is insufficient.
DNV BOP Report
Oil Spill Commission Logo
National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling
The Commission's Final Report: "Deep Water - The Gulf Oil Disaster and the Future of Offshore Drilling. Report to the President."

"As a result of our investigation, we conclude:
  • The explosive loss of the Macondo well could have been prevented.
  • The immediate causes of the Macondo well blowout can be traced to a series of identifiable mistakes made by BP, Halliburton, and Transocean that reveal such systematic failures in risk management that they place in doubt the safety culture of the entire industry.
  • Deepwater energy exploration and production, particularly at the frontiers of experience, involve risks for which neither industry nor government has been adequately prepared, but for which they can and must be prepared in the future.
  • To assure human safety and environmental protection, regulatory oversight of leasing, energy exploration, and production require reforms even beyond those significant reforms already initiated since the Deepwater Horizon disaster. Fundamental reform will be needed in both the structure of those in charge of regulatory oversight and their internal decisionmaking process to ensure their political autonomy, technical expertise, and their full consideration of environmental protection concerns.
  • Because regulatory oversight alone will not be sufficient to ensure adequate safety, the oil and gas industry will need to take its own, unilateral steps to increase dramatically safety throughout the industry, including self-policing mechanisms that supplement governmental enforcement.
  • The technology, laws and regulations, and practices for containing, responding to, and cleaning up spills lag behind the real risks associated with deepwater drilling into large, high-pressure reservoirs of oil and gas located far offshore and thousands of feet below the oceans surface. Government must close the existing gap and industry must support rather than resist that effort.
  • Scientific understanding of environmental conditions in sensitive environments in deep Gulf waters, along the regions coastal habitats, and in areas proposed for more drilling, such as the Arctic, is inadequate. The same is true of the human and natural impacts of oil spills."

Chief Councel's Report

Technical Findings

The root technical cause of the blowout is now clear: The cement that BP and Halliburton pumped to the bottom of the well did not seal off hydrocarbons in the formation. While we may never know for certain the exact reason why the cement failed, several factors increased the risk of cement failure at Macondo. They include the following: First, drilling complications forced engineers to plan a ?finesse? cement job that called for, among other things, a low overall volume of cement. Second, the cement slurry itself was poorly designedsome of Halliburtons own internal tests showed that the design was unstable, and subsequent testing by the Chief Counsels team raised further concerns. Third, BPs temporary abandonment proceduresfinalized only at the last minutecalled for rig personnel to severely ?underbalance? the well before installing any additional barriers to back up the cement job.

BP missed a key opportunity to recognize the cement failure during the negative pressure test that its well site leaders and Transocean personnel conducted on April 20. The test clearly showed that hydrocarbons were leaking into the well, but BPs well site leaders misinterpreted the result. It appears they did so in part because they accepted a facially implausible theory suggested by certain experienced members of the Transocean rig crew. Transocean and Sperry Drilling rig personnel then missed a number of further signals that hydrocarbons had entered the well and were rising to the surface during the final hour before the blowout actually occurred. By the time they recognized a blowout was occurring and activated the rigs blowout preventer, it was too late for that device to prevent an explosion. By that time, hydrocarbons had already flowed past the blowout preventer and were rushing upward through the riser pipe to the rig floor.

Management Findings

The Chief Counsels team concluded that all of the technical failures at Macondo can be traced back to management errors by the companies involved in the incident. BP did not fully appreciate all of the risks that Macondo presented. It did not adequately supervise the work of its contractors, who in turn did not deliver to BP all of the benefits of their expertise. BP personnel on the rig were not properly trained and supported, and all three companies failed to communicate key information to people who could have made a difference.

Among other things:
  • BP did not adequately identify or address risks created by last-minute changes to well design and procedures. BP changed its plans repeatedly and up to the very last minute, sometimes causing confusion and frustration among BP employees and rig personnel.
  • When BP did send instructions and procedures to rig personnel, it often provided inadequate detail and guidance.
  • It is common in the offshore oil industry to focus on increasing efficiency to save rig time and associated costs. But management processes must ensure that measures taken to save time and reduce costs do not adversely affect overall risk. BPs management processes did not do so.
  • Halliburton appears to have done little to supervise the work of its key cementing personnel and does not appear to have meaningfully reviewed data that should have prompted it to redesign the Macondo cement slurry.
  • Transocean did not adequately train its employees in emergency procedures and kick detection, and did not inform them of crucial lessons learned from a similar and recent near-miss drilling incident.
What the men and women who worked on Macondo lackedand what every drilling operation requireswas a culture of leadership responsibility. In remote offshore environments, individuals must take personal ownership of safety issues with a single-minded determination to ask questions and pursue advice until they are certain they get it right.

Regulatory Findings

The Commissions full report examines in depth the history of Minerals Management Service (MMS) regulatory programs and makes specific recommendations for regulatory reform of what is now the Bureau of Offshore Energy Management, Regulation, and Enforcement (BOEMRE). The Chief Counsels team found that the MMS regulatory structure in place in April 2010 was inadequate to address the risks of deepwater drilling projects like Macondo. Then-existing regulations had little relevance to the technical and management problems that contributed to the blowout. Regulatory personnel did not have the training or experience to adequately evaluate the overall safety or risk of the project.
Committee for the Analysis of Causes of the Deepwater Horizon Explosion, Fire and Oil Spill to Identify Measures to Prevent Similar Accidents in the Future
National Academy of Engineering and National Research Council (NAE & NRC)

At the request of the Department of the Interior (DOI), a National Academy of Engineering/National Research Council (NAE/NRC) committee is examining the probable causes of the Deepwater Horizon explosion, fire, and oil spill in order to identify measures for preventing similar harm in the future. The study is organized under the auspices of the NAE and the NRCs Transportation Research Board (through its Marine Board) and the Division on Earth and Life Studies, with assistance from the Division on Engineering and Physical Sciences.
Interim Report on Causes of the Deepwater Horizon Oil Rig Blowout and Ways to Prevent Such Events, 16 Nov 2010


On the basis of its assessment of the evidence collected for this interim report, the committee has developed the following preliminary findings and observations. The sequence in which they are presented is not intended to imply a sense of priority. Additional discussion of each of these findings is presented later in subsequent sections of this report.
  1. The incident at the Macondo well and Deepwater Horizon MODU was precipitated by the decision to proceed to temporary abandonment of the exploratory well despite indications from several repeated tests of well integrity [the test type known as a negative (pressure) test] that the cementing processes following the installation of a long-string production casing failed to provide an effective barrier to hydrocarbon flow (Sections II and III).4
  2. The impact of the decision to proceed to temporary abandonment was compounded by delays in recognizing that hydrocarbons were flowing into the well and riser and by a failure to take timely and aggressive well-control actions. Furthermore, failures and/or limitations of the BOP, when it was actuated, inhibited its effectiveness in controlling the well (Sections III and IV).
  3. The failures and missed indications of hazard were not isolated events during the preparation of the Macondo well for temporary abandonment. Numerous decisions to proceed toward abandonment despite indications of hazard, such as the results of repeated negative-pressure tests, suggest an insufficient consideration of risk and a lack of operating discipline. The decisions also raise questions about the adequacy of operating knowledge on the part of key personnel. The net effect of these decisions was to reduce the available margins of safety that take into account complexities of the hydrocarbon reservoirs and well geology discovered through drilling and the subsequent changes in the execution of the well plan (Section VI).
  4. Other decisions noted by the committee that may have contributed to the Macondo well accident are as follows:
    Changing key supervisory personnel on the Deepwater Horizon MODU just prior to critical temporary abandonment procedures (Section VI);
    Attempting to cement the multiple hydrocarbon and brine zones encountered in the deepest part of the well in a single operational step, despite the fact that these zones had markedly different fluid pressures (because of the different fluid pressures, there was only a small difference between the cement density needed to prevent inflow into the well from the high-pressure formations and the cement density at which an undesirable hydraulic fracture might be created in a lowpressure zone) (Section II);
    Choosing to use a long-string production casing in a deep, high-pressure well with multiple hydrocarbon zones instead of using a cement liner over the uncased section of the well (Section II);
    Deciding that only six centralizers would be needed to maintain an adequate annulus for cementing between the casing and the formation rock, even though modeling results suggested that many more centralizers would have been needed (Section II);
    Limiting bottoms-up circulation of drilling mud prior to cementing, which increased the possibility of cement contamination by debris in the well (Section II);
    Not running a bond log after cementing to assess cement integrity in the well, despite the anomalous results of repeated negative-pressure tests (Section II);
    Not incorporating a float shoe at the bottom of the casing as an additional barrier to hydrocarbon flow (Section II); and
    Proceeding with removal of drilling mud from the well without installing the lockdown sleeve on the production casing wellhead seals to ensure the seals could not be shifted by pressure buildup under the seals (Section II).
  5. Available evidence suggests there were insufficient checks and balances for decisions involving both the schedule to complete well abandonment procedures and considerations for well safety (Section VI).
  6. The decisions mentioned above were not identified or corrected by the operating management processes and procedures of BP or those of their contractors or by the oversight processes employed by the Minerals Management Service (MMS) or other regulators (Sections VI and VII).
  7. Currently, there are conflicting views among experts familiar with the incident regarding the type and volume of cement used to prepare the well for abandonment. There are also conflicting views on the adequacy of the time provided for the cement to cure. These factors could have had a material impact on the integrity of the well (Section II).
  8. The BOP did not controlor recapture control ofthe well once it was realized that hydrocarbons were flowing into the well. Also, both the emergency disconnect system designed to separate the lower marine riser from the rest of the BOP and automatic sequencers controlling the shear ram and disconnect failed to operate (Section IV).
  9. Given the large quantity of gas released onto the MODU and the limited wind conditions, ignition was most likely. However, the committee will be looking into reports (such as testimony provided at the MBI hearings) that various alarms and safety systems on the Deepwater Horizon MODU failed to operate as intended, potentially affecting the time available for personnel to evacuate (Section V).
  10. The various failures mentioned in this report indicate the lack of a suitable approach for anticipating and managing the inherent risks, uncertainties, and dangers associated with deepwater drilling operations and a failure to learn from previous near misses (Section VI).
  11. Of particular concern is an apparent lack of a systems approach that would integrate the multiplicity of factors potentially affecting the safety of the well, monitor the overall margins of safety, and assess the various decisions from perspectives of well integrity and safety. The safety case strategy required for drilling operations in the North Sea and elsewhere is one example of such a systems approach (Section VII).
US Department of the Interior - BOEMRE

Chemical Safety Board
CSB to Investigate Root Causes of BP Deepwater Horizon Blowout Accident


NORSOK D-010, "Well Integrity in Drilling and Well Operations, Revision 3, August 2004" A free document, published by the Norwegian standards body. Comprehensive discussion of barrier systems in wells.
"Recommended Guidelines for Well Integrity"

Link to the OLF website
The OLF (Oljeindustriens Landsforening, the Norwegian Oil Industry Association) through the WIF (Well Integrity Forum) working group, have prepared this document to assist in design of well integrity management systems.
Free access to API safety and cited documents The purpose of this site is to provide the public with access to key industry standards, particularly those standards that are safety-related or have been incorporated into federal regulation. Please use this site to review standards related to process safety, refinery and chemical plant operations and equipment, offshore drilling, hydraulic fracturing and well construction, and pipeline safety on welding, and public awareness programs. These standards are available for review only, and hardcopies and printable versions will continue to be available for purchase.
API/ISO Documents - these documents can be downloaded from the API web site, ISO web site or from the IHS web site.
API 6A/ISO 10423: "Specification for Wellhead and Christmas Tree Equipment"
API 6AF: "Technical Report on Capabilities of API Flanges Under Combinations of Load" Analysis of flange loading including bolt makeup (pre-load), internal pressure, tension and bending moment. Pertinent to evaluating loads and bending moments imposed on trees.
API RP 14B/ISO 10417: "Design, Installation, Repair and Operation of Subsurface Safety Valve Systems" Note: the leak rate formula provided in API 14B for SI units is low by a factor of 100.
An errata sheet has been issued that provides the correct formula.
API RP 14C: "Recommended Practice for Analysis, Design, Installation, and Testing of Basic Surface Safety Systems for Offshore Production Platforms"
API RP 14E: "Recommended Practice for Design and Installation of Offshore Production Platform Piping Systems"
API RP 14H: "Recommended Practice for Installation, Maintenance, and Repair of Surface Safety Valves and Underwater Safety Valves Offshore"
API RP 57: "Offshore Well Completion, Servicing, Workover, and Plug and Abandonment Operations"
API RP 65: "Cementing Shallow Water Flow Zones in Deep Water Wells"
API RP 90: "Management of Sustained Casing Pressure on Offshore Wells" Guidelines on managing wells with sustained casing pressure on an annulus
TR9501, Rev A: "Specification for Stud Bolts and Tap End Studs" Association of Well Head Equipment Manufacturers, 11 June 2002. This AWHEM Recommendation establishes definite dimensions for stud bolts and tap end stud for use wth API Spec 6A flanges/studded flange connections and provides for dimensionally interchangeable stud bolts and tap end studs for API Spec 6A flanges/studded flange connections.

SPE Resources & Papers - SPE web site, "OnePetro" web site

Well Integrity Technical Section SharePoint site Technical Sections are "virtual" SPE sections that help link together SPE members with similar interests. These communities of SPE members join together to share ideas, promote competence, and develop projects related to their technical interest. Technical Sections tend to be more task-oriented than discussion-oriented. They meet virtually for the most part, but are encouraged to hold a face-to-face meeting at least once a year.
SPE Distinguished Lecturer Presentation: "Implementing a Well Integrity Management System"

Spanish-language version
This presentation was presented during the 2007-2008 SPE Distinguished Lecturer season
SPE 142854: Assessing Well Integrity Risk: A Qualatative Model For successful delivery of Well Integrity, there needs to be an understanding of the risks that can cause undesirable events such as safety hazards or loss of containment. Performing a risk assessment on a well, or type of well, will help determine and rank the potential risks and provide information that allows limited resources to be applied in the most effective manner. The main objectives of performing a risk assessment include:
Follow a formal process to assess risk consistently and to enable comparison between well barrier failure mode scenarios;
Qualitatively assess well barrier failure risk for every segment of a well;
Document suggestions that are offered by the risk assessment team for mitigating well barrier failure risk; and
Provide a report of the methodology, failure mode scenarios, risk ranking, and potential mitigation actions for use as a reference tool for managing well integrity on a routine basis.
SPE 142449: "The Seven Pillars of Well Integrity Management": The Design and Implementation of a Well Integrity Management System Today and industry wide, management of well integrity is a common issue, and relates to both old and new producing fields. It is apparent that many fields were not designed with the concept of well lifecycle management and were probably constructed for a life of about 15 - 20 years. A producing well that is 30 years old is quite common (e.g. North Sea production started in 1975) and for wells in locations such as the Middle East some fields are more than 40 or 50 years old.

In line with its expansion and transition to becoming a major independent oil company through its recent discoveries of very large oilfields in Ghana and Uganda, Tullow Oil needed to broaden its existing well integrity policy and practices. This is to fit with a projected 4 to 5 fold increase in oil production in the next few years and increase its well count to over 500 wells.

In order to evaluate the processes in-place, the Seven Pillars of Well Integrity Management were defined as the fundamental requirements of an ideal system. These were used to identify gaps in existing practices which were systematically and thoroughly addressed by Tullow.
SPE 137966: "Well Integrity Management System (WIMS) Development" Operators continuing success depends on the ability to manage its reservoirs and to exploit them in the most efficient manner to sustain production targets, while maintaining a high level of safety performance. Ensuring the integrity of wells is essential to achieve these requirements. Some of operated wells are reaching an age where an increasing frequency of integrity issues is becoming a concern. In addition, new wells may face greater threats to their integrity, for example due to the more corrosive reservoir fluids often encountered in existing and new developments. Wells operating under high annulus pressure are at risk of loss of pressure containment either in the form of releasing formation fluids to atmosphere or cross flow and charging up shallow reservoirs or aquifers. When monitoring trends of annulus pressures it should be taken into account that even with relatively low sustainable pressure there is a possibility that cross flow to shallow reservoirs could be taking place. This is especially true for C-C annulus B of most oil and water injection wells where shallow water reservoirs are straddled by one casing. Any sustainable annulus pressure on this annulus is undesirable and is to be critically reviewed.

A well may also show annuli pressure due to thermal effect and this must always be checked for when a new well is being produced for the first time or when a well is brought into production after being shut in for a long period. It should be remembered that pressure increase due to thermal effect could be considerable. One of the most key integrity challenges is the Sustained Annuli Pressure in A, B and C casings.
SPE 137630: "Risk Register and Risk Ranking of Non Integral Wells " Non-Integral Wells are common in every aged field and managing their integrity is becoming a challenging issue, particularly in large fields and for complex dual completions such as the case in ZADCO operated fields. As part of the Well Integrity Management System (WIMS), integrity concerns are identified, investigated and subsequently mitigation measures are recommended to restore the well integrity, all in a systematic approach. Well barrier integrity is given the highest priority; therefore a comprehensive Risk Register and Risk Ranking process is implemented by ZADCO Well Integrity Team.

The Risk Register process utilizes every related data and integrity investigation results to evaluate the integrity of the well primary & secondary barriers for every flow path. An individual integrity assessment is performed on the different containment sections in a well such as wellhead, inner and outer annuli and zonal isolation. Based on the severity, consequences and likelihood of a barrier failure the individual containment is given a risk rank according to ADNOC/ZADCO risk matrix. The overall risk ranking of a well reflects the highest risk rank of any of its containments. To complete the risk register, existing safeguards are addressed and appropriate short and long term mitigation actions are recommended to keep the risk at ALARP.
SPE 135907: Application of an Intellegent System to Ensure Integrtiy Throughout the Entire Life Cycle Excellence in Well Integrity is about having the necessary barriers in place, understanding and respecting those barriers, testing and verifling the barriers, and having contingencies in place should these barriers fail verification. This paper will discuss the organisational barriers throughout the well's lifecycle that typically impede creation of a proper WI system. The author also describes the methodology of how well threats can be identified, assessed, prevented and/or mitigated based on the Hazards present in the subsurface environment and the condition of the barriers in place to control those hazards.
SPE 134500: A Case History: The installation of a damaged control line replacement safety valve system in a North Sea well Interesting discussion of how to gain wellbore access through the bottom seat on the lower master valve and run a SSSV control line inside the tubing.
SPE 133056: Well integrity assessment and assurance: the operational approach for three CO2 storage fields in Italy Comprehensive discussion on the approach taken to evaluate 3 mature fields for CO2 injection. A good example of the "well integity journey" to awareness of well condition.
SPE 130395: Case Study: Shallow Surface Casing Corrosion Mitigation Evaluation
SPE-129083: Well Integrity Issues in Malacca Strait Contract Area The Malacca Straits contract area is located on the east of Sumatera Island between Sumatera and the Malaya Cape. This area started oil production in the early 1980s, and consist of 175 onshore and offshore oil wells spread over five fields, namely the Kurau, Melibur, Selatan, Lalang, and Mengkapan oil fields.

A 7.9 Richter scale earthquake occurred on 12 September 2007. The epicenter of the earthquake was 159 KM south west of Bengkulu, a province in the southern part of Sumatera. Two days later, during a snubbing unit service on the K-02 well, the 9-5/8 casing suddenly dropped down six feet. It was believed that the area had been impacted by the earthquake since another snubbing unit found lateral movement on wellhead while doing workover on nearby well. Following the incident, the well services team inspected the K-02 well and found it had an integrity problem.

This finding lead to a wider investigation, which revealed that other wells also suffered integrity problems, including unsecured wellheads, leaking wellheads and christmas trees, severe corrosion of well components, failure of cement bonding, and casing elongation / casing drop due to top soil compaction / reservoir subsidence. At this point, it was decided to initiate a comprehensive well integrity study.

The integrity problems are due to several causes: wells exceeding their design life (most wells were constructed in the mid to late nineteen-eighties), exploration wells being used as producers without improvement, environmental degradation from deforestation (drop in the water table causing top soil compaction), and more than twenty years of production (causing formation subsidence).

This paper details the well integrity study, including the well assessment, the evaluation of well operation in term of safety, environment and profitability, and recommended effective temporary remedial actions.
SPE 128688: Use of Real-Time Data in Well Integrity Management Real time data provides key information that can be used to monitor oil and gas wells to maintain well integrity and avoid costly failures. Integrity management is at the heart of BPs operating philosophy. The company uses new technologies enabled by real time data to allow continuous improvement in well integrity management. The use of real time rate calculations has provided technical assurance to maximize production within BPs deepwater subsea field development. Production has been increased by 10,000 stb/D while maintaining well integrity and process safety assurance within safe engineering operating limits. Similarly, the Na Kika fields apply advanced flux based tools and sand alarming capabilities to protect wells from sand completion failure. Additional fields are currently using BP proprietary technology to monitor and proactively alarm on wellhead annulus pressures, successfully mitigating the well integrity risk of collapsed tubing.
SPE 125712: Well Casing Integrity Excellence: A Case History of Evaluating Casing Integrity Using Modern Imaging and Corrosion Tool Logs in Ghawar Field in Saudi Aramco Ensuring good casing integrity is very important to prolong well life. Cement quality is a major element for ensuring casing integrity. Well casing integrity excellence is the key aspect that makes a well in good condition and keeps the well completion suitable to produce crude oil from an oil producer or inject water in an injector.

Recently, advances in cement and well completion practices have significantly improved the quality of wells and extended their operating life. Also, the installation of a Cathodic Protection System (CPS) on every well, and tubing packer completion in some wells, prevented external corrosion and consequently casing failure. However, casing integrity problems were discovered in three isolated cases. This paper will discuss issues related to three wells where casing leaks or behind casing channeling were detected across a high-pressure zone located above the main reservoir. A team, consisting of professionals from various engineering departments, was formed to explore remedial options and techniques, as well as employ tools and new technologies that assess well casing integrity excellence. Implementing the recommendations and findings of this team have improved well casing integrity.

As well casing is an important asset to ensure well safety, continuous operation and environmental protection; there is an ever increasing need for tools that verify wells with suspect casing integrity problems. These tools are the Cathodic Protection Evaluation Tool (CPET), Ultrasonic Inspection Tool (USIT), Ultrasonic Corrosion Inspection Tool (UCIT) and the Electro-Magnetic Imaging Tool (EMIT). The EMIT provides real images of the multiple casing strings.

CPET, USIT, UCIT and EMIT were selected and run on three wells Well-A10, Well-A20 (oil producers) and Well-B1 (water injector) with suspected casing integrity problems. These logs detected and imaged the corroded, scaled and cracked intervals before performing remedial actions to return the wells to an operating status by renovating casing integrity.
SPE 123201: A Systematic Approach to Well Integrity Management A discussion of Marathons implementation of the Expro WI management software in the North Sea. Recognising the importance of good well integrity management practices, Marathon Oil UK developed an online database in conjunction with Expro to capture their well integrity data. The database has become a focal point to help facilitate Marathons well integrity management processes and philosophies. The aim of this paper is to provide an overview of the rational for developing the system and the benefits that are being realised for both the Brae and Alvheim assets.
SPE 120978: Pressure Activated Sealant Economically Repairs Casing Leaks on Prudhoe Bay Wells Pressure activated sealant was used to repair casing leaks in two Prudhoe Bay, Alaska oil wells without the use of a rig workover. The significance of the treatments, development of job screening criteria, and job planning and execution are reviewed.

Production casing leaks are a frequent problem in mature oil fields, particularly where there is corrosion. Wells with casing leaks usually do not meet well operating criteria so they must be shut-in, causing a loss in valuable production. Casing leaks normally require a rig workover to repair since the tubing often has to be removed. Rig workovers are very expensive in offshore locations, remote areas, and harsh climates. Special pressure activated sealants, diagnostic tools, and treatment techniques have been developed to find and repair casing leaks without removing the tubing.

Case studies of three Prudhoe Bay production wells describe how pressure activated sealant successfully repaired the small casing leaks in two wells without removing the tubing. The third well was not treated because it did not meet the screening criteria. One case study was unusual because the sealant fixed four deep casing leaks with one treatment.

The case studies show how refinements in diagnostic techniques, candidate screening, and treatment planning and execution have resulted in the successful application of pressure activated sealant to repairing casing leaks in producing wells and in one case repaired four leaks with one treatment. Using pressure activated sealant to repair casing leaks can result in significant cost savings and return wells to production sooner. The treatment can be particularly useful in mature fields with corrosion problems and in offshore, remote, and arctic fields where rig workovers are expensive and rig availability is limited.

SPE 120946: Well Integrity Management: A Systematic Way of Describing and Keeping Track of the Integrity Status for Wells in Operation Talisman operates several fields on the Norwegian Continental Shelf (NCS), many of these mature fields are taken over at the end of their design life. These old fields represent challenges with respect to well integrity and overall profitability.

Talisman is a member of the Well Integrity Forum (WIF), a co-operative effort between the operating companies on the NCS to define a unified approach for handling well integrity. Using WIMS and the WIF recommendations together with internal guidelines improves Talismans ability to handle well integrity issues throughout the production phase of a well and in compliance with regulatory requirements.

This paper describes how Talisman Energy Norway (Talisman) manages well integrity for their assets, and discusses the benefits, challenges and lessons learned from implementing a well integrity management system, focusing on technical and organizational aspects.
SPE 120495: Implementing a Well Integrity Management System This discussion defines Well Integrity and presents the framework used by BP to implement and manage well integrity programs. Well integrity has received increasing attention from all aspects of the petroleum industry, from well design and construction to operations, maintenance and well abandonment. Factors driving this attention include a desire to ensure wells remain viable in fields with long lives, maintenance of company reputation and avoidance of litigation. Confusion regarding the definition of well integrity can make it difficult to create a holistic approach to implementing a management system.
SPE 117121: The Total Control of Well Integrity Management This paper describes a web-based program which provides a comprehensive approach to well integrity management covering all potential integrity threats to the whole well. This cradle-to-grave software, the Intetech Well Integrity Toolkit (iWIT), provides well information and data analysis for timely, informed, decision-making. Using its own or existing client databases, this software carries out quantitative data analysis in real-time and provides feedback to the operator about the condition of individual wells and also overviews of the whole field integrity status.
SPE 116771: Prudhoe Bay Well P2-15 Surface Casing Failure Case history of a surface casing failure due to drilling wear.
SPE 116765: Analysis of Thread Engagement Requirements for Studs and Nuts Discusses issues associated with incomplete stud-nut makeup. Presents alternatives to remediation if well safe out activities are required.
SPE 115585: A Compliance-Based Approach to Well Integrity Management This paper describes a process for actively managing well integrity throughout the development life cycle with a particular focus on the production operations / well maintenance phase. Although developed in relation to ConocoPhillips UK North Sea development wells, most of the features of the process have application to all development well operations (both onshore & offshore) under any regulatory regime.

The original well integrity management process was developed in order to demonstrate compliance with the UK Offshore Installations & Wells (Design & Construction, etc) Regulations 1996 (DCR). Since that time the original process has continued to be modified to improve effectiveness & efficiency. As well as describing the current process, this paper also describes its development and how we see that the process might evolve in the future.

DCR regulations form a part of the UK safety case regime. The safety case regime places a strong focus on the development of site-specific performance standards; it also utilises the principles of independent examination & verification in order to demonstrate compliance. The process described in this paper represents a significant new contribution to the management of major accident hazards in well operations since it focuses on the use of performance standards and independent examination in order to ensure well integrity.
SPE 114911: Real-Time Well Diagnostic Using Slick-Line Fiber-Optic Distribute Temperature Sensors: West Venezuela Applications Conventional slick-line temperature surveys enable successive temperature measurements at pre-determined depth stations along the well-bore. This method has two major drawbacks. The wellbore fluid flow dynamics impact the temperature accuracy while the uncertainty in depth leads to erroneous conclusions on spatial temperature distribution along the wellbore. Remedial actions based on these temperature measurements do not always help optimize productivity or injectivity. To overcome these measurement uncertainties and correctly evaluate the gas-lift system performance for the oil producer wells or to identify temperatures anomalies, such as flow behind casing for water injection wells, continuous temperature measurements with time and depth are needed.
SPE 112872: Trapped-Annular-Pressure Mitigation: Spacer Fluid That Shrinks - Update Discussion of a field trial in a 9,800-ft-deep gas well of a water-based polyymerization shrinks 20%, mitigating trapped annular pressure (TAP).
SPE 112535: Well-Integrity Issues Offshore Norway A number of serious well failures in recent years led to investigations of well integrity issues. The Petroleum Safety Authority Norway (PSA) performed a "pilot well integrity survey" based on supervisory audits and requested input from 7 operating companies, 12 pre-selected offshore facilities and 406 wells. The wells were a representative selection of production and injection wells with variation both in age and development categories.

The pilot project indicates that 18% of the wells in the survey have integrity failure, issue or uncertainties and 7 % of these are shut in because of well integrity issues. The selection of wells and the companies indicate that the statistics is representative.

The well incidents in the past and the results of "pilot well integrity survey" revealed that the industry needs to increase focus on the barrier philosophy. Control of barrier status is an important SHE factor to avoid major incidents caused by e.g. unintentional leaks and well control situations. Knowledge of well integrity status at all times enables the companies to take the right actions in a proactive manner and thereby prevent incidents.

The paper presents the results and the conclusions from the pilot survey. In addition a number of technical well failures will be presented, identifying critical elements such as corrosion, leaks and operational factors. In particular, the understanding of barrier regulations, standards and implementation was found inadequate.
SPE 110347: Well Integrity Management System (WIMS)A Systematic Way of Describing the Actual and Historic Integrity Status of Operational Wells It is important to be able to have an overview of the well integrity at all times. Statoil, Norsk Hydro and Total E&P UK Ltd. therefore joined forces in a JIP with ExproSoft to develop a software application for data collection, handling and reporting of well integrity. The resulting software is called WIMS, short for Well Integrity Management System. A pilot version was installed and tested by the operators spring 2007, prior to the release of the final version.
SPE 108906: "Detecting Ultra-small Leaks With Ultrasonic Leak Detection-Case Histories From the North Slope, Alaska" An ultrasonic leak detection logging tool conveyed on electric line, and recently on wireline in memory mode, has been introduced which can detect leaks as small as 1/2 cup per minute. This revolutionary tool has been used to accurately identify leaks in tubing and behind pipe. Wells that otherwise would immediately be slated for a rig workover (RWO) have been repaired with non-rig solutions.
SPE 108698: "Well Integrity Assurance: A Successful Method for External Corrosion and Damage Detection on Outer and Middle Concentric Strings of Casing"

SPE Presentation.pdf
As well integrity is of utmost importance for personnel safety and environmental interests there is an ever increasing need for tools and systems that verify and confirm the status of wells with suspect integrity. Recent near-surface, outer casing failures caused by external corrosion on relatively new wells in the Kuparuk Field of Alaska prompted research for a non-invasive predictive method to foresee failure and aid repair prioritization. There are a variety of tools and methods available to locate leak points and corrosion inside of tubulars, but very little literature exists concerning external corrosion and damage detection on outer and middle concentric strings of casing. The following method is a valuable qualitative approach used to determine existence and severity of shallow external surface casing corrosion before leaks occur.
SPE 108195: "Locating and Repairing Casing Leaks with Tubing in Place - Ultrasonic Logging and Pressure-Activated Sealant Methods " When operators are faced with issues involving casing leaks, a typical course of action is to pull the tubing and make efforts to identify and locate the source of the leak by logging or other mechanical means. If the leak source can be successfully located, a mechanical method is generally employed to patch the leaking casing. This methodology is time consuming and expensive.

Locating casing leaks with the tubing in place using conventional logging techniques has historically been difficult. Where some tools, such as temperature tools, may provide an indication of an anomaly in annuli, the data may be subjective or the leak may be too small to measure. When active, a leak will produce a spectrum of sonic frequencies that may be either audible, ultrasonic or both. Ultrasonic energy will pass through steel but travels relatively short distances. A tool developed around these principles has been successful in accurately locating casing leaks behind tubing.

Pressure-activated sealants have been used for a number of years to cure a wide variety of leaks in casing, tubing, control lines, and well heads as well as micro-annulus leaks in cement. For the purpose of repairing a casing leak behind tubing, the liquid sealant may be pumped into the annulus and displaced to the leak site. The liquid sealant will not polymerize until it is exposed to the differential pressure through the leak site. Knowing the leak rate, pressure and precise location of the leak aids in the selection of the sealant formulation and deployment method. This helps to reduce overall repair cost as well as increase the probability of a successful repair.

This paper will describe the ultrasonic method of leak detection and the method of curing leaks with pressure activated sealant with tubing in place. Case histories will be presented where these methods were employed to repair casing leaks without removing the tubing.
SPE 106533: "Rigless Installation of Safety Valves To Implement a Well-Integrity Campaign and Return Wells to Production" Protecting the environment and health of the people by ensuring the integrity of all wells is one of the must-obey policies in Shell Petroleum Development Company of Nigeria Limited (SPDC). SPDC has been the leading producer of crude oil in Nigeria for more than 50 years. SPDC produces from many brown fields. SPDC currently has an inventory of producing wells that have been shut in because of one form or another of wellbore integrity problems. In some cases, these wells were completed decades ago when HSE requirements were considerably less stringent than they are today and wells were completed without sub-surface or downhole safety valves.

In 2003, a more stringent policy on non-integrity wells was introduced and led to an investigation of service providers for a more reliable rigless installation of safety valves or a more cost effective rig workover. However, most of the brown fields that encompass these wells are predominantly located in the Niger Delta both in the shallow waters offshore and in land locations including swamp areas. Many of the wells are located on small-unmanned production jackets which do not have the structural integrity to support even an electric line unit let alone a workover rig. In addition the current geopolitical situation in the Niger Delta is such that bringing in any heavy-duty equipment can be extremely difficult and highly uneconomical in most of these low producing wells.

It was against this background that SPDC carried out a well integrity management campaign to examine the feasibility of some kind of economic intervention to bring these wells back onto production.

In this paper the authors will examine in detail the prevailing situation, present details of the alternative solutions that were considered and describe a highly economic campaign that was put in place to rehabilitate some 40 wells and make available some 30,000 bopd of oil production, all without the use of major workover equipment.
SPE 105319: "A Comprehensive Approach to Well-Integrity Management in ADMA-OPCO" The last few years have seen a renewed emphasis on Well Integrity (WI) worldwide, and ADMA-OPCO in particular.
ADMA operates, more than 600 wells, in two offshore fields, which include oil producers, water injectors, gas producers/injectors and observation wells. A dedicated team was setup to focus entirely on WI and related issues. The team was given the objective to achieve the following.

- Determine the Well Integrity Status of the entire well stock through risk review and ranking.
- Recommend appropriate action plan for each well with unacceptable level of risk.

The team used a comprehensive and novel approach for handling this project. This paper is a case study of the methodology adopted by the team to achieve this task.

Since the main objective was to risk review and rank the entire well stock, a dedicated risk-ranking process was designed, which served as an automatic guide to risk review and ranking of wells. The industry Risk Ranking matrix was modified to make it more objective and easy to use.

It soon became obvious that risk evaluation of wells was only possible based on availability of good data organized in a user-friendly format. A dedicated database was setup in parallel with other activities. The web-based database was designed to contain all the data required for WI review of any well and is capable of tracking well integrity related tasks automatically.
Well Integrity data included well construction, annuli pressures, production, well intervention, etc. The data existed in the office files were promptly transferred into the database.
SPE 102815: "Applied Ultrasonic Technology in Wellbore-Leak Detection and Case Histories in Alaska North Slope Wells" When operators are faced with well integrity problems, a variety of methods may be used to detect the source of annular communication. Methods for detecting downhole leak points include spinners, temperature logs, down-hole cameras, thermal decay logs, and noise logs. However, many of these methods are ineffective when dealing with very small leaks and can result in collecting data that requires a significant amount of logging finesse to interpret.

Ultrasonic listening devices have been used for a number of years to effectively detect leak sources in surface production equipment. Ultrasonic energy has some properties, when compared to audible frequency energy, which make it ideal for accurate leak detection. Like audible frequency energy, ultrasonic energy can pass through steel. However, ultrasonic energy propagates relatively short distances through fluids when compared to equal energy audible frequency sound.
SPE 102524: "Well Integrity Operations at Prudhoe Bay, Alaska" This paper discusses the well integrity management system used at the Prudhoe Bay field located in Alaska. The focus is on systems and processes implemented to manage the well operations and interventions phase of a wells life.
SPE 101888: "Gate Valve Drilling/Milling Operation on the North Slope, Alaska" Milling out a gate valve is a very tedious operation and could be risky if the proper well control and procedures are not put in place. 
SPE 101398: "Restoring Well Integrity in a Critical Gas Pilot Injection Well" Appearance of abnormally high pressure in the 9 5/8 X 13 3/8 casing annulus of a pilot gas injection well located offshore Abu Dhabi, alerted staff to a potentially serious situation from both safety and economic viewpoints. The subject well is a critical component of a pilot project to test the effectiveness of gas injection towards improving oil recovery. Based on this and other data, decisions on long-term reservoir development involving considerable investment will be made. The well was drilled and completed in 1999 as dual gas injector into two, Lower Cretaceous limestone reservoirs and put under gas injection in 2001. Abnormally high pressure was observed in the 9 5/8 x 13 3/8 annulus after three months of injection. A multidisciplinary task force was formed with a mandate from senior management to locate the source of leaking gas, the communication path to surface and recommend remedial actions. A risk assessment ranked the danger to the 80 million U.S. dollar platform and personal as high. As a result, gas injection was halted and visits to the platform minimized. Evidence gathered from the well records and newly acquired diagnostic logs suggested the existence of poor or no cement behind the 7 liner and 9 5/8 casing providing a conduit for gas to surface. Moreover, the existence of two abandoned holes penetrating the shallowest reservoir and located at short distance from the currently active bore hole were recognized as potential pathways for gas to surface. Extensive remedial cementing operations were performed including: (1) block squeezes behind one and two sets of production casing above the source reservoir, (2) cement circulation squeeze between production and intermediate casings through mechanically drilled holes. The high annulus pressure was thought eliminated but soon returned after injection commenced. A decision was made to convert the nearby un-perforated Gas Observer to water injection for the shallowest reservoir and continue gas injection into the deepest reservoir of the original well.
SPE 100600: "Downhole Integrity Management in October Field, Gulf of Suez, Egypt" The paper discusses historical data related to downhole scaling, corrosion and surveillance methods to identify affected wells. Efforts to minimize production impact due to increased corrosion seen late in the field life along with longer term corrosion mitigation efforts are also reviewed. Examples of how tubing was originally protected by thin film scale accumulation and emulsion flow during early field life production are also presented. Increasing Octobers completion corrosion manageability is a key challenge facing the field. Addressing issues related to predicting future well failures and their associated production loss impact rig scheduling and procurement of expensive long-lead time completion material (Cr 13%).
The approved plan is to repair six wells per year over three years considering known well problems, remaining reserves, materials and rig availability. In early 2005, six well's were worked over and visual inspection of retrieved tubing showed an excellent match with caliper log data. The most severe corrosion is typically deep in the well and is related to high CO2 partial pressures. Corrosion risk to the casing has also been identified as potential issue and wall thickness assessments have been performed on some workovers. The paper reviews these items in greater detail and proposes forward plans for the remaining life of field.
SPE 98739: "The Snorre A Incident 28 November 2004: Lessons Learned"

PSA Investigation of Snorre Blowout
Statoil has carried out a comprehensive analysis of the underlying causes after a gas seabed blow-out on the Snorre field in the North Sea. On 28 November 2004, an uncontrolled gas blow-out took place on the seabed under the platform. The incident occurred in connection with the preparation of well P-31A for the drilling of a sidetrack. During pulling of a 2,578 m scab liner, gas was drawn into the well and it leaked out through a known hole in the 9 5/8" casing then through an unknown damage or weakness in the 13 3/8" casing.

PSA Report: On 29 November 2004, the PSA appointed an investigation group which has identified non-conformities and improvement areas. These can be categorized as follows: Lack of compliance with governing documents, inadequate understanding and implementation of risk assessments, inadequate management involvement and violation of well barrier requirements. The non-conformities occurred at several levels in the organization on land and on the facility. The investigation shows that the number of non-conformities and improvement areas is extensive. There is nothing that would indicate that the incident was a result of chance circumstances.
SPE 97863: "Managing Well Integrity, Safety, and Production Decline Caused by Scale" This work will describe the management of scale in a United Arab Emirates offshore carbonate reservoir. Field pressure is sustained by water injection, which contributes to the formation of scale in downhole tubulars. This scaling can cause both safety and production problems, for example, by blocking a subsurface safety valve or chocking flow at downhole nipples.
ZADCO has initiated a successful strategy to manage the sulfate-scaling tendency in the completion tubing. Software is used to identify wells early on as potential scale candidates. This software uses real field measurements and analysis of injected and produced water information. The results are used to plan well monitoring and/or treatment. The identified wells are monitored using both slickline gauge measurements to measure actual scale growth and produced water surface analysis to update the software model.
SPE 97597: "A Case History of Sustainable Annulus Pressure in Sour Wells Prevention, Evaluation and Remediation" This paper describes evaluation of the possible causes of Sustainable Annular Pressure (SAP) in a sour gas field in the Middle East. It explains the diagnostic testing undertaken and describes how evidence was used to identify the cause of the SAP. The steps taken to prevent the occurrence of SAP in new wells and to remedy the problem in existing wells are described.
SPE 96337: "Want to Make Tree Operations Safer? Why Not Use the DHSV as a Barrier?" Industry practice for the design and operation of oil and gas producing wells incorporates a two-barrier policy, and defines an integrity envelope for environmental protection and safe operations. The standard practice when removing or undertaking major operations on the Xmas tree is to set one or more plugs in the production tubing to maintain two barriers between the reservoir and the environment.
This paper assesses the relative risk of using a Down Hole Safety Valve (DHSV) as a qualified barrier during such operations.
QRA has been used to assess the risks of an uncontrolled flow of fluid from the reservoir when using a qualified DHSV as a barrier as compared to the standard practice of setting one or more wireline plugs. Three representative cases have been considered in this study:
Case 1 examines changing valves downstream of the master valve on a sub sea well.
Cases 2 and 3 focus on platform wells.
Case 2: changing valves downstream of the lower master valve, and
Case 3: removing the Xmas tree.
The study shows that the major risk when using a wireline set plug as a downhole barrier arises from the blowout risk associated with wireline operations. Use of a DHSV as a qualified barrier eliminates the wireline blowout risk, and reduces the overall risk during Xmas tree operations. Hence, the study recommends the use of a qualified DHSV as a barrier, subject to a risk assessment on a case by case basis.
SPE 95813: "Enhancing Collaboration Between Engineering and Operations - A Case Study of Alaska Work Processes" This paper details the collaboration and well information system BP Exploration (Alaska), Inc. has implemented to enhance communication and data sharing between work groups operating the Prudhoe Bay field. Accessing and sharing well information and maintaining quality communication between geographically separate Operations and Engineering teams is an issue in all oilfield operations.
SPE 94427: "Northern Sahara Aquifers Protection: Casing Corrosion Problems and Defining New Well Construction Performance ObjectivesCase Study: Hassi Messaoud Oilfield in Algeria" Well construction reliability is always of great importance especially when it is about drilling in an arid region that contains strategic groundwater reserves. This is the case of Hassi Messaoud and satellite oilfields (HMDs) in Algeria where aquifers of the Northern Sahara System (NSAS) Spread out. Problems closely related to well construction such as casing corrosion, cementing lack and also those of post-abandonment are encountered by Sonatrach and partners there.
SPE 91399: "Microannulus Leaks Repaired with Pressure-Activated Sealant" Sustained casing pressure is a serious problem that is prevalent in most of the oil producing regions of the world. Annular pressure can be a significant safety hazard and, on a number of occasions, has resulted in blowouts. Sustained casing pressure results from the migration of fluids in the annulus. The most common path for migration of fluids is through channels in the annular cement. To safely and economically eliminate sustained casing pressure on a well in the Gulf of Mexico, W&T Offshore, Inc. utilized an injectable pressure-activated sealant technology to seal channels in the annular cement of their well and eliminate the casing pressure. The mechanical integrity of the well was restored, saving over $1,000,000 compared to a conventional rig workover.
SPE 88934: "Well Integrity Management System in Shell Nigeria" Well Integrity is a vital aspect of well design, construction, operation, maintenance and abandonment. As put by SPDC, all wells shall be designed, constructed, operated, maintained and abandoned in a manner that safeguards their integrity, minimize Health, Safety and Environmental risks and ensure their planned availability throughout their life-cycle. As a consequence of this policy, all wells are monitored to ensure their integrity is guaranteed at all times. By implication all wells that fall short of standards are secured or closed-in unless a short-term deviation or waiver is granted.
Well integrity problems may occur in producing and non-producing wells, especially older wells that were completed as per the prevailing completion standard of their completion dates. The completion standards have changed over time with respect to safety requirements (e.g. wells without top packers, wells without SCSSVs). There may also be some wells that meet current safety standards but still have some integrity-related problems (e.g. leaking packer or silted well slots-swamp locations).
SPE 88696: "Well Integrity Management System (WIMS)" ZADCO owns more than 500 wells operating in UZ, UA & ST fields to contribute in achieving the production targets as set by the Shareholders. To ensure that wells operate as designed for their assigned life (or greater) with all risks kept as low as reasonably practicable or as mentioned, it is important to insure individual well's integrity. Hence, ZADCO developed an in-house Well Integrity Management System (WIMS), which defines & provides the operating standards & guidelines for maintaining the well integrity parameters, ensuring safe well operations and securing well potential availability during its life cycle so that return on investment is maximized without the sacrifice of safety and environment.
The implementation of ZADCO's well integrity process follows the cycle assurance testing, preventive measures, monitoring, evaluation / assessment, control & remedy, audit / verification.
SPE 87198: "Remediating Sustained Casing Pressure by Forming a Downhole Annular Seal with Low-Melt-Point Eutectic Metal" Described are proof-of-concept developments to form a seal for mitigating sustained casing pressure caused by annular pressure buildup. Annular pressure can result from numerous sources, including tubing leaks, loss of isolation potential within the cement column because of poor mud displacement, free water-induced channels, stress fractures, and failure of the cement to cover all potential sources of annular pressure. In most cases, annular pressure is not observed at the wellhead until the well is placed on production, making it difficult to identify, access, or remediate the pressure source. A new and novel approach to remediation has been tested in which a low-melt-point alloy metal is dropped down the backside of the casing where annular pressure has been observed. The metal is allowed to accumulate at the top of cement or other physical barrier, melted with an induction-heating tool, and allowed to cool and solidify. This process forms an annular seal to stop fluid communication between the formation and wellhead.
SPE 84556: "Improved Techniques to Alleviate Sustained Casing Pressure in a Mature Gulf of Mexico Field" The objective of this paper is to highlight the techniques used during a recent workover program to alleviate sustained casing pressure in a Gulf of Mexico field. Discussion will include cement and workover fluid programs, hole preparation before milling and cementing operations, and improved milling procedures.
SPE 81002: "Acoustic Signal Analysis for Sand Detection in Wells with Changing Fluid Profiles" Discusses results of a study to predict sand production using acoustic meters.
SPE 67194: "Diagnosis of Sustained Casing Pressure from Bleed-off/Buildup Testing Patterns" When the casing pressure can not be permanently bled off through needle valves at wellhead, the casing is said to exhibit Sustained Casing Pressure (SCP). Since high values of SCP may threaten worker safety and environmental protection, MMS regulations require remedial treatment. Testing of SCP could provide information on parameters causing gas migration and SCP.
A mathematical model for testing SCP buildup has been developed. The objective of the model to identify the flow mechanism of external leak leading to SCP. The model also determines critical parameters of the leak to be used in selecting some remedial actions. Also presented in the paper are two examples of using this model to analyze actual SCP field tests. The analysis gives acceptable estimates of the depth of gas invasion zone, formation pressure, cement conductivity, and expected maximum value of casing pressure.
SPE 36913: "Risk Assessment of Hydrocarbon Releases during Workover and Wireline Operations on Completed Wells on Offshore Platforms " Safety Regulations in the UK require operators to demonstrate that the risks to workers from well operations on offshore platforms have been reduced to the lowest level that is reasonably practical. Each offshore platform in the UK has a safety case which includes a quantified risk assessment of well operation hazards with the potential to cause a major accident.
Assessment of the safety cases by the UK Health and Safety Executive (HSE) showed that few operators have specifically analysed risks resulting from well workover or wireline operations, regarding such risks as subsumed within general blowout risks. where workover/wirelining have been considered separately, the risk estimates have been determined from average worldwide historical hydrocarbon release frequencies and not by analysis of particular operations being carried out on a specific platform. The prevalent conclusion from such risk analyses is that the contribution of workover/wireline risks to the total platform risk levels is very small. In order to evaluate whether such a conclusion is necessarily valid in all cases, HSE undertook a study to establish a method for estimating workover/wirelining risks for a number of different types of platform.
SPE 23136: "The Occurrence of Annulus Pressures in the North West Hutton Field: Problems and Solutions" This paper discusses the occurrence of annulus pressures in the North West Hutton oilfield, offshore UK, and how the problems associated with these pressures have been addressed. Several wells have experienced annulus pressures in this field, where production is exclusively via gas lift. The causes of annulus pressures are discussed in the context of the mechanical configuration of the wells. An evaluation of the safety aspects and concerns associated with these pressures is then presented.
SPE 22871: "How to Design for Annulus Fluid Heat-up" Existing single-string analysis methods are inadequate for solution of heat-up problems, which require a global analysis of the whole well system (all casings together). This paper presents a method for such a technique, termed global service life analysis, and describes an FE program (ADHOC) developed to implement it. The formulation is fully general, and is applicable to a wide range of casing design problems.

Introduction: An earlier paper co-written with BP described a recent study into annulus heat-up stresses in subsea production wells. A new and rigorous theoretical model was developed, and used for the computer analysis of several case studies. The results showed that:
- annulus heat-up causes high burst/collapse stresses; - conventional design methods were inadequate for predicting these stresses.
However, limited space prevented any attempt to explain the analysis method. This paper presents the theoretical basis for the earlier work, and explains how this theory is applied in practice.
SPE 21727: "Methods of Detecting and Locating Tubing and Packer Leaks in the Western Operating Area of the Prudhoe Bay Field" Evaluation methods have been developed to detect cases of tubing/annulus communication. Temperature, spinner and noise logs, as well as fluid level detection equipment, are used under a variety of flow conditions. Step-wise procedures are provided.
SPE 178: "Helical Buckling of Tubing Sealed in Packers" Most gas wells and flowing oil wells are completed and treated through a string of tubing and a packer. Changes in temperature and in pressure inside or outside the tubing will: (1) if free motion of the tubing inside the packer is permitted, increase or decrease the length of the tubing; or (2) if free motion is prevented, induce forces in the tubing and on the packer. If pressure inside the tubing is greater than outside, the tubing may buckle helically even in the presence of a packer-to-tubing tension.
IPTC-13405-MS: Well Integrity Management Systems; Achievements versus Expectations Managing well integrity is essential to economically develop oil and gas resources while preserving the environment and assuring safety to personnel.

The industry accepted definition of well integrity management is the application of technical, operational and organizational solutions to reduce the risk of uncontrolled release of formation fluids over the entire lifecycle of the well. (NORSOK-D010)
Well Integrity assurance on the other hand is to ensure the availability and functionality of at least two well barriers during its drilling, production and abandonment phases.

The current worldwide focus is on the development of systems and processes to manage the well operations and interventions to assure well integrity with many claims to have a workable system that verifies and confirms the status of wells with suspect integrity.

The basis for well integrity management systems can be categorized as:
  • R & D oriented systems that are built around the development of technical solutions to well construction and operational problems. For example, the development of new inspection logs, cements, materials, equipment and techniques.
  • Statistically driven, those are based on the study of the historical failure frequencies and the assessment of associated risk.
  • Well pressure monitoring and assessment and wellhead maintenance.
  • Reservoir model based system that takes into consideration the reservoir development to ensure well integrity throughout the field development and production life.
In this paper different well integrity management systems were reviewed against worldwide industry expectations for a system that can manage well integrity that starts at the exploration phase and continues through its abandonment.

IPTC-12624-MS: Optimizing Well Integrity Surveillance and Maintenance Managing well integrity is essential to economically develop oil and gas resources while preserving the environment and assuring safety to personnel. ExxonMobil Exploration & Production Malaysia Inc. (EMEPMI) operates 17 offshore oil and gas fields in the Malay Basin. EMEPMI performs well integrity operations and maintenance on 37 platforms involving 781 wells with 1215 completions (single and dual wells). There are about 350 wells on gas lift, 1215 surface controlled subsurface safety valves (SCSSV), with 6943 tree and wellhead valves. The fields produce approximately 150,000 bopd and 1.2 BCFD of gas.
In this mature asset, many wells were previously un-competitive or uneconomic to flow. In todays higher-price environment, all wells are being re-evaluated for their production contribution. This paper describes the issues and actions taken for these moth-balled idle wells to ensure that they comply with the EMEPMI well integrity surveillance and maintenance standards for offshore platform facilities. At the same time, the effort was broadened to check and ensure the integrity of all active completions. The EMEPMI well integrity surveillance and maintenance standards are based on API and industry standards, as well as the global ExxonMobil well integrity standards.
IPTC-11678: "Design and Early Implementation of a Well Integrity Management System in an Offshore Brownfield Operation" A well integrity safety management system was developed and methodically implemented during 2005-07 in the Gulf of Suez, Egypt. The system is fit-for-purpose to meet the unique needs and capabilities of the organization. Methodical execution of the system was strategically planned and prioritized based on safety risks and business needs.
This paper provides a summary of the Gulf of Suez well integrity system development and deployment. Critical well integrity requirements were evaluated in a comprehensive well integrity study during 2005. Many existing well integrity practices were documented and formalized. Other outstanding requirements were identified and assigned a priority for implementation.
Existing Gulf of Suez wells were found to be in various conditions on well integrity, ranging from high to relatively low operating risk. Criteria for defining a high risk well were established and communicated throughout the organization. High risk wells were documented in a public register and shut-in if necessary to reduce operating risk. Also, a dedicated well services team was established to control and/or repair high risk wells on a full-time basis.
"Annular pressure buildup: What it is and what to do about it" Deepwater Technology, August 2000, by Bob Moe and Peter Erpelding. When tubing heated by hotformation fluids contacts colder fluids entrapped in the annulus, the result is fluid heating and pressure buildup. Proper well design is critical in subsea wells.
OTC 11029: "Sustained Casing Pressure in Offshore Producing Wells" /td>

MMS Studies

"Risk Assessment of Temporarily Abandoned or Shut-in Wells", Project 99041, October 2000 An MMS sponsored study of the risk relating to temporarily abandened and shut-in wells.
"A review of sustained casing pressure occurring on the OCS" Report submitted to Minerals Management Service. Downloadable from MMS website, www.mms.gov/TubingStudy.


Aker Solutions Leak Metering SystemAker Leak Measurement System Background:
Failure in downhole barriers such as completion, tubing, casing or cement is a growing problem in the North Sea mainly due to the increasing number of ageing wells. Such failures need to be addressed at an early stage to reduce the risk to personnel, equipment and the environment. If a leak is allowed to develop the potential of an uncontrolled situation will increase and the chances of a successful and cost-effective repair will be reduced. The risks associated with barrier failures are defined considering annulus pressure value. Allowable leak rate for oil, gas and water are regulated by Norsok D-010 and API RP 14B.

The Leak Metering System (LMS) provides the following measurements:
Direct leak rate measurements up to 5000 psi
Leak rate in accordance with API RP 14B
Detailed composition and physical properties of the leak
Measurement of leak depth/possible leak path
Measurement of gas volume contained in annuli
Pressure development with respect to Maximum Allowable Annular Surface Pressure (MAASP)
Level of toxic components
Levels of corrosive components
Communication test between wellbores
Pressure build-up testing for leak rate calculations
Real-time and historical pressure and temperature measurements
Baker Tubing patches
Canada Tech Pressure Gauges photos Our Surface Logger is a surface pressure gauge which displays data in real-time. The Surface Logger operates as a memory recorder or a real-time, short-range wireless pressure transmitter.

With regular usage, a battery has a life of 1 to 2 years. Sample rates are programmable and the Surface Logger displays pressure and temperature in various units as determined by the user.

The use of Canada Techs Firmware version 1.6 or greater will allow the Radio Surface Logger to function as a memory recorder and a wireless pressure transmitter when set to Log Mode. The Radio Surface Logger is able to independently turn off the radio in a radio-free environment. Built using our proven Piezo-Resistive sensor and acquisitions electronics, the Surface Logger produces near- quartz quality data in a reliable and economical package. Ambient temperature compensation ensures the long term accuracy of the data, day or night.
Echometer Well sounding devices for determining fluid levels
PDS Memory logging tools - calipers & spinners
Pioneer Petrotech Services Inc. (PPS) is a global leader in the development and manufacturing of high quality pressure and temperature gauges for oil and gas industry. Our innovative electronic technology has enabled us to offer robust 200 deg.C gauges for assisting oil companies to explore oil reserves in deep water areas. The easy to use software has made gauge operator's job a lot more productive and simpler. Our mission is to help world wide customers acquire accurate reservoir pressure and temperature data in all different well conditions. PPS 31 - Wellhead Pressure Logger The PPS31 is a wellhead digital pressure and temperature monitoring gauge. The application of radio transmission allows operators to receive real-time data which is also stored in the memory chip in the logger. Pressure and temperature can also be directly read from the LCD (liquid crystal display). The intrinsically safe design permits the logger to be used in critical environments.
Schlumberger Logging services
SeaWell (formerly TecWell) Seawell's ground-breaking Point diagnostics suite uses innovative, high definition, ultrasound technology for fast, accurate fault location and greater operator confidence
The "Point" system includes four powerful diagnostic tools
- LeakPoint: identifying the precise location of leaks in tubing, casing and well components
- FlowPoint: revealing the exact source and flow paths of annular fluids
- SandPoint: accurately locating the entry points of damaging sand
- EntryPoint: bringing much higher resolution to production profiles
Spidr Gauges Self-contained pressure and temperature recording device
ThinJack What is ThinJack?
  • ThinJack is a TIG-welded 2mm thick grade 316L steel envelope.
  • ThinJack works by inflating the envelope with hydraulic oil pressure.
  • ThinJack expands by up to 10-15 mm by inflation and exerts hundreds of tonnes of force.
  • ThinJack is the ideal solution to separating and jacking problems in hazardous, difficult to access or restricted areas
Wachs On-site machining, casing and wellhead cutting and valve turning equipment & services.
Weatherford Tubing patches
WellCut Decommissioning Services Engineering services, hot tap machines and field machining services.
Wellube - Unique Marine Group Engineering services, hot tap machines and field machining services.


Brinker-Technology At Brinker Technology we offer a unique brand of innovative technical solutions to promote integrity management to the pipeline industry worldwide. Based around our patented Platelet Technology we deliver these solutions through:
Implementation of novel leak locating and sealing products and engineering systems
Expert consultancy
Ongoing research and development
We are a dynamic and creative company who are focused on implementing our unique technology to the advantage of the pipeline industry worldwide. We are based in Aberdeen, Scotland but have a truly global presence having completed projects in the UK, Norway, Australia, Azerbaijan and Alaska.
CSI Technologies
Subsidiary of Suprior Energy and Wild Well Control
UltraSeal, an epoxy well sealant designed to create seals over a wide range of well conditions.

CSI Technologies provides research, engineering and oilfield product development for the energy industry.

CSI Technologies solves challenging problems ranging from high-pressure, high-temperature cementing to effective stimulation techniques to lost circulation. The company has a long history of developing new oilfield methods and products using its applied engineering capabilities.
Furmanite Leak-sealing technology and onsite service. Since 1929, weve created groundbreaking and patented leak sealing technology; and we consistently provide these solutions with the highest level of service to customers around the world.
Loctite When something breaks, "Repair, don't Replace" it! Replacing household items that break or show wear can become expensive. Any repair - from small to large - can be accomplished with just three Loctite products: Loctite Ultra Gel Super Glue, Loctite 1 Minute Instant Mix Epoxy, or Loctite Power Grab Construction Adhesives. All are Solvent Free making the air nice to breathe, feature easy to use applicators, and are recloseable to allow for multiple uses. For over 55 years, Loctite Adhesives have delivered Trusted Performance and Proven Results. You can tackle any repair with the performance of Loctite.
M & D Industries - "Ultra Seal" Ultra Seal R Sealant Ultra Seal R Sealant is a special epoxy resin. The materials viscosity has been lowered to provide easy mixing and placement. The lowered viscosity is accomplished without the volumetric shrinkage that usually accompanies the thinning of epoxy resin. Applications include micro annular gas migration, mechanical isolation valve, casing leaks, well bore stability, and loss circulation.
Oil Center Research Distributes:
GX Safety Seal (711-714), used to plug leaks in DHSV lines
Hyposeal (527 & 528), used to plug tubing and casing leaks.
Sandaband Sandaband consists of concentrated sand made into a pumpable slurry with water and brines. Sandaband has a particle fraction in excess of 75% by volume. The particle size distribution controls the rheology, permeability and porosity of the slurry. Sandaband characteristics:
  • Behaves as a true Bingham Plastic material
  • It is pumped like a liquid, sets up like a solid mass when in place, but without becoming rigid
  • Sandaband is non polluting and chemically inactive.
SealMaker International SEALMAKER International specializes in engineered leak repair solutions. Uses liquid pressure activated sealants to repair troublesome leak problems associated with oil and gas production onshore and offshore.
Seal-Tite Seal-Tite International has a line of pressure activated sealants designed to seal tubing hanger, casing hanger and wellhead leaks; production tubing and casing leaks; microannulus, sustained casing pressure and salt dome storage cavern leaks; control line, safety valve and packer leaks; as well as umbilical, flowline and subsea leaks. After the sealant has reached the leak site, the sealant begins to plate out on the edges of the leak, and simultaneously bridges across the leak to seal it.

Software, Well Examination and Audit Services

Expro - SafeWells www.wellintegrity.com. A software system for managing well integrity related information.
Exprosoft - WIMS Supply "WIMS" - Well Integrity Management System. Software application that will contribute to a uniform and structured approach for handling of well integrity during the lifetime of a well. WIMS will ensure that the information necessary for handling well integrity is available through one system, and with a clear indication of the well barrier status at all times.
Halliburton Halliburton's cementing design software: "Using our programs, operators can complete a range of related tasks, from analyzing the casing and cement sheath, to surveying the surrounding formation to determine the best mechanical properties for an optimum sealant."

Also provides a link to the popular "eRedbook" software.
Intetech - iWIT A software system for managing well integrity related information. Their brochure.
OA Tools A free site with web-based calculators. Includes tubing movement, casing burst, DHSV leak rate calculators.
NRG Well Management Ltd

NRG Well Examination and Management Systems Ltd
NRG Well Management Ltd is focused on the cost effective delivery of Project Management for Drilling and Well Operations. In addition we carry out Well Engineering and Field Development Studies which range in size from simple one day technical reviews through to detailed multi disciplinary studies lasting many months, for a wide variety of Clients.

NRG Well Examination & Management Systems Ltd, in addition to providing independent well examination services, specialises in the delivery of workable management systems for upstream Operating Companies and Service Providers. Our Systems assist the client to both manage health, safety and environmental hazards as well as enable them to demonstrate compliance with all the applicable licence and statutory requirements without the need for extensive Management Systems. Apart from satisfying the statutory requirements our Systems contribute towards lowering the cost of operations by ensuring that Clients Management focus their attention on their defined responsibilities, whilst enabling them to effectively delegate responsibilities to contractors where necessary.
Peloton - WellView, RigView, SiteView, ProdView Drilling and Well Data Software Solutions
- Peloton is 'well focused' on developing the world's best drilling and well data software solutions.
- Peloton started developing WellView in 1991 for well operations and schematic visualization. Today, Peloton has evolved to provide a full well lifecycle data management solution for Operations, Drilling and Construction/Reclamations.
- Peloton's comprehensive data model and software technology improves morning reporting, well and site visualization and data quality.
PetEng Calculators A free site with web-based calculators for a variety of petroleum engineering calculations.
Well Integrity Tracking System (WITS) A free web site to demonstrate the ability to track the well integrity status of wells. Allows setup of new wells, tracking of barrier status, entry of well intervention and annulus bleed events, etc.
WellEz WellEz.NET for field operations reporting WellEz provides the most convenient and easy-to-use field reporting solution available today. Designed for integrated field reporting for the lifecycle of a well, WellEz.NET leverages web-based technology to manage all well data from initial planning to a variety of reporting functions such as Drilling, Completion, Work-over , Facilities, and Plugging and Abandoning (P&A). In the office, bottom-hole assembly (BHA), drilling mud, well costs and a range of other critical data, can be captured and analyzed using custom Multi-Day and Multi-Well Reports. Wellbore schematics can be automatically created from the field data.

Wellbore Schematic Programs

Completions Manager - Petrofocus Completions Manager provides a fast and highly visible improvement in well completion information. Within a month of an order, a client can have: 100 diagrams of their wells in Completions Manager format, Completions Manager software installed at their offices, All users trained how to maintain their drawings and create new ones. The software allows engineering teams to design and maintain high quality well completion diagrams in a controlled and standardized manner. Using the software's comprehensive symbol libraries, internal database and automated drawing features, engineers can create drawings quickly and easily without compromising on quality.
Completion Services Completion Services is a Well Completion Diagram Quality Assurance and Software Solution business, working with small, medium and large oil companies throughout the world that are looking to centralize and quality assure their completion schematics, resulting in easy access to what is actually downhole and the most up to date drawings.
VIPR - Parallinx VIPR (owned by Parallinx) is a well bore installation schematic aid that enables the user to expedite well installation schematics in an efficient and user-friendly manner. The software has 17 categories, runs in Microsoft Excel and is extremely easy to use, such that any employee can input the information and prepare a basic diagram in less than five minutes. The program has over 700 Icons to choose from for building wellbore schematics. Visual Wellbore software (http://www.parallinx.net) is directed at the oil and gas industry, and is ideal for those with completions and drilling backgrounds.
WellBarrier Well Barrier Schematics
A comprehensive library is available which covers:
Drilling Activities
Testing Activities
Completion Activities
Production Activities
Sidetrack, Suspension & Abandonment Activities
Wireline Operations
Coiled Tubing Operations
Snubbing Operations
Under Balanced D&C Operations
Pumping Operations
for any type of well and installation.
WellView - Peloton WellView is a complete corporate well file. From well planning to abandonment, WellView tracks all changes and operations throughout the well's lifecycle. With its powerful schematics, reports, and analysis tools, WellView puts information in the hands of the people who need it most. Working with Pelotons MasterView, WellView is part of an integrated well lifecycle analysis and visualization solution.
XTREE Schematic - DRILLINGSOFTWARE Xtree Schematic for Office 2007
A complete system for building a land based Well Head with a library of hi-resolution Drilling Spools, Flanges, Valves and Chokes, simply click on a component and drag it into place on your Well Head Sketch.

Tree-Wellhead Services

Cameron Trees and Wellheads
RS Clare The Clare range of Valve Lubricants for the Oil & Gas Industry has been developed in conjunction with Original Equipment Manufacturers and Production, Drilling and Service operators.
  • Valve Lubricant 501, an Extended Low Temperature Range valve lubricant has been developed to provide comparable performance to 601 within a temperature range of -75F to 250F.
  • Valve Lubricant 601 is a fully synthetic lubricant, ensuring long term lubricating and sealing qualities within a temperature range of -20F to 350F.
FMC Trees and Wellheads
Vetco-Gray Trees and Wellheads
PTC - Petroleum Technology Company PTC has a variety of speciality tools:
  • Telescopic VR lubricators
  • SealCure for damaged seal bores

Regulatory Agencies

Interstate Oil & Gas Compact Commission This links to a very comprehensive list of all states regulations.
Alabama Oil and Gas Board Alabama
Alaska: AOGCC - Alaska Oil and Gas Conservation Commissions Alaska regulatory agency. Link to the AOGCC report, "Investigation of Explosion and Fire at Prudhoe Bay Well A-22".
California State Lands Commission, Mineral Resources Management Division California
Federal: MMS - Minerals Management Service U.S. Federal
Louisiana Department of Natural Resources Louisiana
Texas: The Railroad Commission of Texas Texas
Wyoming: Wyoming Oil and Gas Conservation Commission Texas
Alberta, Canada Alberta Energy Board Alberta


Yahoo "Well Integrity" Group - http://finance.groups.yahoo.com/group/Well-Integrity/ A Yahoo discussion group with a well integrity theme. Does not get much usage.
Wikipedia article on Well Integrity It's currently pretty sparse, but could be a good place to put best practices.
Southwest Research Institute Southwest Research Institute is an independent, nonprofit applied research and development organization. The staff of 3,000 specializes in the creation and transfer of technology in engineering and the physical sciences. The Institute occupies more than 1,200 acres in San Antonio, Texas, and provides nearly two million square feet of laboratories, test facilities, workshops and offices.
Stress Engineering Services We offer extensive design, testing, and analysis experience in both the upstream and downstream segments of the industry in virtually all phases of operations. Services we provide includes: Riser and Mooring Design & Analysis, Floating Production Systems, Vessel Load / Motion Analysis, Crane Testing and Design Review, Subsea Engineering, Field Instrumentation and Monitoring, Fitness for Service Evaluation, Tubular Testing and Analysis, Component and Tool Design, Full-Scale Component and Systems Testing, Coil Tubing Evaluation for Oilfield Applications, Failure and Finite Element Analysis, Materials Engineering and Metallurgy, Forensic Engineering.
John Wright Company's Technical Library on Blowout Control An outstanding primer on well control operations
Lone Star Steel Casing Reference
Bolting Info
ExproBase Textbooks The textbooks describe basic knowledge suitable to be presented as textbooks. Each textbook aims to give a general and practical insight into selected subject. The reader will not become an expert by reading the textbooks, but gain improved understanding of the subjects described and thus being able to ask more relevant questions to the experts.
iHandbood  Schlumberger, www.slb.com

Contact: Joe Anders, jlanders@hotmail.com
Revised: 24 April 2011