Integrity and corrosion assessment for successful slot recovery and plugging & abandonment (P&A) applications Article featured in Oilfield Technology   For all plug and abandonment applications, either permanent or for slot recovery, the sealing performance of well system components needs to be assured, and remain intact.    Well systems are complex and need to work perfectly to perform safely, cleanly, and productively. Understanding the condition and sealing performance of well system barriers can be challenging once the well has been brought onstream and access to these elements and components is restricted.     Current mainstream technologies only provide partial answers, leading to an incomplete assessment. However, through-barrier diagnostics look at the well system in a far more holistic and uncompromising way. These technologies have the capability of seeing through multiple barriers to provide a more complete picture of the condition of the metal tubulars and the flow around them to see if the seals are holding, prior to plug and abandonment.     In the case of permanent abandonment, natural barriers that prevent the movement or migration of downhole fluids, must be restored. And the performance of the well system barriers  must remain intact indefinitely.     In the case of slot recovery, the well components must be in good enough condition to be used again for the upcoming production cycle.   A comprehensive integrity assessment is required for either scenario.  Optimising P&A operations Planning and executing a flawless plug and abandonment requires prior knowledge of the integrity of the well barriers, and the precise position of all downhole completion elements. Operators armed with this information can determine the location of the permanent plugs and the best depths for the casing cuts for an optimised retrieval procedure.     During the productive life of a well it may experience several operator changes, perhaps after concessions expire or following divestment decisions. This can often lead to historical data being lost which, when it comes to well decommissioning, can increase the potential for making decisions without knowing all the facts about the well system, particularly the position of the casing collars, fins, centralisers or other components that impede successful decommissioning.     Using a simple multifinger caliper or an ultrasound survey, the location of the first-barrier casing collars can be determined, but the locations of the collars in the subsequent casing strings remain unknown. This approach contains an element of risk and may result in a cut planned directly in line with a thick section of metal, like a casing collar, or fin. Cutting across a collar or a fin, would mean an increase in the rig and intervention time of several hours, or potentially days.    TGT’s Multi Tube Integrity product uses the Pulse electromagnetic sensing platform to provide accurate barrier-by barrier assessment of up to four concentric tubulars (up to 20” diameter) in one single through-tubing deployment. Pulse can also pinpoint to within 1ft the location of completion elements.    The ‘electromagnetic signature’ of each tube or metal completion component, contains information about its wall thickness. The Pulse platform harnesses this information and through 3D modeling, can decipher metal loss as well as metal gain, in multiple casing strings throughout the entire well system.     Pulse can identify the location of known completion elements, but also identify new ones, not expected including welded fins on the outer casing string, often inaccessible to other evaluation technologies.     If Multi Tube Integrity is used prior to the P&A planning, the diagnostic results would remove the uncertainty allowing operators to confirm the optimum cutting window location in all casings, thus minimising the intervention time and reducing rig time and costs.  Integrity & corrosion assessment for slot recovery Slot recovery offers operators a way of capitalising on existing assets, by providing a new means of extending a well’s productive life.     It is a robust solution which utilises the existing surface and downhole infrastructure, to create a “new” offshoot well, which would reduce the costs associated with drilling. However, before this can become a reality, the inspection of downhole completion elements such as surface casing and its cemented annulus are a must.     Limitations in current technologies have meant that barrier verification is performed while the rig is in place, and once the tubulars (production and intermediate casings) have been retrieved.     Key input parameters, such as the cement condition and the integrity of the casing are obtained at the last stage of the planning. The late arrival of this critical information results in a complex well intervention plan, with several contingent scenarios based on a range of potential outcomes from the downhole integrity assessment.     The industry is calling for a new solution. One which can determine the condition and sealing performance of the cement and the metal barriers, prior to planning the slot recovery.  Pulse data showing wall thickness, collars and completion elements in 5 ½ in., 9 5/8 in., 13 3/8 in. and 20 in. tubulars. A powerful diagnostic combination TGT’s Multi Tube Integrity product used together with the Multi Seal Integrity product is the answer. This powerful combination utilises TGT’s Pulse electromagnetic platform, the Chorus acoustic platform and the Indigo multisense platform, and it can be deployed in one through-tubing deployment.   Pulse is used to evaluate the metal thickness of multiple tubulars, including the surface casing. It also has the unique capability of being able to confirm the position of critical completion components, including collars, centralisers, and casing shoes.   Chorus is used to assess the hydraulic seal integrity of the cement barrier to determine where the cement is sealing and where it is not. Fluid flow in the well system creates a rich spectrum of acoustic energy that penetrates the surroundings. This acoustic wave is encoded with information that Chorus can convert into acoustic spectra that can locate leaks and flowpaths throughout the well system, from the wellbore to the outer annuli.   The Pulse, Chorus and Indigo platforms are part of TGT’s True Integrity System which provides a clear diagnosis of integrity dynamics throughout the well system. The key to success It is critical that before slot recovery can be executed, there is an understanding of the collective integrity of the tubes, seals and barriers of the mother well. Only in doing this can there be a guarantee of the secure passage for pressurised fluids.   The key to success for any P&A or slot recovery operation is knowing all the facts about the integrity of the well system prior to planning and execution. This delivers the potential to reduce costs, minimise schedule overruns, and ensures the integrity of the final outcome.

Did you miss out? Due to an overwhelming response to our first series of #TechTalks came back for series 2!   Once again the topics were diverse and  revealed a range of powerful well system diagnostics that would help you to maintain safe, clean and productive well operations.   If you missed the sessions, they are available to watch again by clicking the links below. The series was a resounding success, so have planned a second series covering different topics. To find out more click here. #TechTalk No. 4 – Pulse1 diagnostics Enabling "no compromise" integrity management for primary tubulars   Pulse1 is the newest addition to our Pulse electromagnetic platform. It is the industry’s first slimhole tube integrity technology capable of delivering ‘true wall thickness’ measurements of production tubing in eight sectors, with complete ‘all-around’ sensing of tube wall condition.   Multifinger calipers and conventional electromagnetics are a popular choice to assess the integrity of production tubulars. They are tried and tested, but each technique has its drawbacks.   In this #TechTalk, Ken Feather uncovers how a new diagnostic resource delivers five times the accuracy of conventional techniques, enabling operators to assess the condition of production tubulars more accurately than previously possible, helping the industry to ensure safe, clean and productive well operations. TechTalk No. 4 – Pulse1 diagnosticsDOWNLOAD PRESENTATION #TechTalk No. 5 – Multi Tube Integrity Diagnosing the integrity of multiple tubulars, accurately and efficiently   The miles of metal tubulars that form the backbone of every well system and are fundamental to its integrity. Tracking the condition and wall thickness of these tubulars is essential to maintaining a secure well.   In this #TechTalk, Asiya Zaripova and Natalya Kudryavaya reveals how TGT’s Multi Tube Integrity product provides an accurate barrier-by-barrier assessment of up to four concentric tubulars from a single through-tubing deployment. Multi Tube Integrity #TechTalkDOWNLOAD PRESENTATION #TechTalk No. 6 – Get the most from your fracturing resources with "Fracture Flow"   Effective hydraulic fracturing requires careful planning and a huge fleet of pumps, equipment and people. Knowing how these costly resources can deliver maximum impact is literally the million-dollar question.   In this #TechTalk, Remke Ellis reveals how our new ‘Fracture Flow’ product can be used pre- or post-fracturing to evaluate actual reservoir flow profiles, so fracturing can be targeted, assessed and optimised to deliver maximum efficiency—without the million-dollar price tag. Get the most out of your fracturing resourcesDOWNLOAD PRESENTATION If you have any questions, please don’t hesitate to email us. Or, if you have a suggestion for a #TechTalk you would like us present, please email: communications@tgtdiagnostics.com.

The oil and gas industry is continually raising well integrity standards and moving closer to a ‘no compromise’ approach. Article in Harts E&P   Mechanical “multifinger” calipers have been used routinely by integrity managers for decades as the primary diagnostic method to evaluate production tubulars, partly because they offer a broad range of benefits, but partly because there was no viable alternative. There is now another option.     The miles of metal tubulars that form the backbone of the well system are fundamental to its integrity. Chief among these are the production tubing and production casing, often referred to as “primary tubulars” or “primary barriers” because of their special role in keeping wells safe, clean and productive. Primary tubulars are the central conduits that transport fluids between reservoirs downhole and the wellhead. Collectively, primary tubulars form the wellbore and, from an integrity perspective, their main task is one of containment—keeping pressurized fluids safely inside the well system permanently—protecting and producing 24/7 for the entire life of the well.     But primary tubulars have their work cut out for them; they need to unfailingly withstand the rigors of downhole conditions. Well systems are dynamic and can be hostile environments for man-made materials, even steel. Extremes and variations of pressure and temperature can cause mechanical stresses, well fluids can potentially corrode and erode the steel tubes, and mechanical interventions can cause additional wear over time. Regular inspection is therefore important to ensure continued safe, clean and productive operations. Tube Diagnostics Tube inspection tends to focus on three main attributes: tube wall thickness, tube wall defects and tube geometry. And although tube geometry or profiling is important, wall thickness and defect sensing are typically the two main objectives from an integrity perspective.     With these applications in mind, the industry has developed a number of diagnostic technologies and methods aimed at tracking the condition of primary tubulars. Each has its strengths and drawbacks in terms of accuracy, resolution, coverage, efficiency and cost, when measured against their ability to assess wall thickness, defects and geometry. In a recent industry survey of 100 well integrity management professionals conducted by TGT, mechanical “multifinger” calipers were identified as the most prolific diagnostic method used to evaluate production tubing. For production casing, electromagnetic and ultrasound techniques were the most popular, but calipers were still prominent.     Mechanical calipers offer a broad mix of attributes that make them suitable for tube diagnostics. They are widely available to suit all sizes of production tubing and casing, they are relatively inexpensive and easy to deploy, and can provide comprehensive assessment in all three areas of wall thickness, defect sensing and tube geometry. However, calipers have several application-specific drawbacks, mainly in terms of accuracy in determining actual wall thickness in some scenarios, and sensing small defects.     According to the industry survey of integrity managers, the most important attributes experts consider when selecting diagnostic methods to evaluate production tubing are: the accuracy and sectorial coverage of wall thickness measurements, and the completeness and resolution of defect sensing. Geometry assessment is a lesser priority. Furthermore, the experts required a wall thickness accuracy of at least ±3% and a defect resolution of approximately 3 mm.     To track tube wall thickness, calipers measure internal diameter (ID) and estimate thickness by assuming a nominal outside diameter (OD). Variations in the actual OD or external corrosion, both invisible to calipers, can invalidate the thickness value. Also, scale or wax deposits on the inner surface can mask internal defects and lead to further false thickness computations. And while the accuracy of caliper ID measurements is approximately ±5% (±0.5 mm), the total system error for wall thickness can reduce to ±10% (±1 mm), or worse if there is scale or external corrosion. This accuracy is far below the ±3% level currently required by integrity managers.     For defect sensing, calipers offer highly precise radial measurements via 24, 40 or 60 fingers spaced azimuthally around the inner tube surface. Thin, 1.6 mm fingertips can sense the smallest defects provided the defect lies in the path of the finger passing over it. Practically, there are gaps between fingers that vary according to tube size and finger density. For example, the gap between 24 fingers in 3-1/2 inch, tubing is about 7 mm. This means that the fingers only sense about 10%-30% of the inner wall surface and it is possible for small defects or holes to pass undetected between fingers. A new alternative Despite the drawbacks, mechanical calipers have been used routinely by integrity managers for decades as the primary diagnostic method to evaluate production tubing, partly because they offer a broad range of benefits, but partly because there was no viable alternative.     In an effort to provide an alternative, TGT has developed a new diagnostic platform that can be used independently, or together with calipers or other techniques to provide a more accurate and comprehensive evaluation of tube integrity. Pulse1 is the industry’s first slim tube integrity technology capable of delivering “true wall thickness” measurements of production tubing in eight sectors, with complete all-around sensing of tube wall condition.     Unlike calipers that measure ID to estimate thickness, Pulse1 uses electromagnetic energy to measure actual metal wall thickness directly. This can translate into greater accuracy, especially if the tube wall is coated with scale or has external corrosion. Pulse1 delivers eight sectorial wall thickness measurements up to an accuracy of ±2% in all common tubing sizes, and up to ±3.5% in production casings. This meets or exceeds new industry requirements and represents about a five-fold improvement on caliper accuracy.     In terms of defect sensing, Pulse1 can sense localized metal loss defects equivalent to 7-10 mm diameter holes in the most common production tubing sizes. Calipers offer greater resolution, and Pulse1 provides greater coverage, so combining both delivers a more comprehensive assessment then previously possible. The graph depicts primary tube integrity utilizing Pulse1 to evaluate 6-5/8-in. casing, and a comparison with XY caliper. Overall metal loss measured from Pulse1 is greater than that estimated by XY caliper. The caliper will only detect internal loss, whereas Pulse1 will measure actual metal thickness and assess both internal and external loss. (Source: TGT Diagnostics) Efficiency, versatility and chrome Corrosion-resistant chrome alloy completions provide protection from corrosive and toxic fluids, and the inner wall surfaces are often coated with an additional thin protective film. Many operators prefer not to use calipers to inspect such completions because the millimeter-thin tips of caliper fingers might scratch the inner surface, exposing the alloy and leaving it vulnerable to attack. It’s a dilemma because regular inspection is essential, and previous electromagnetic methods only provided an average non-sectorial thickness measurement. Pulse1 provides eight thickness measurements and is deployed with soft-touch roller centralizers with less point-pressure on the tube wall, minimizing the risk of scoring. This makes it a safer alternative for inspecting chrome completions. And because Pulse1 utilizes ultra-fast sensing technology and time-domain techniques, it is as effective in chrome alloys as in conventional steel tubulars.     In terms of efficiency, diagnostic interventions cost time and money. The Pulse1 tool OD is 48 mm slim and delivers accurate sectorial wall thickness in tube sizes from 2-7/8 inch to 9-5/8 inch. This means operators can survey production tubing and the casing below the tubing shoe in a single deployment, saving rig time and intervention costs. Combining Pulse1 with Pulse4 enables multi-barrier assessment, and both can be deployed rigless on slickline improving efficiency. Enhancing integrity management The oil and gas industry is continually raising integrity standards and moving closer to a “no compromise” approach, and this development is helping the industry to achieve that goal. For applications where accurately tracking wall thickness is the main priority, Pulse1 can be considered as a reliable and practical alternative to mechanical calipers. And if the well is prone to scale, wax or external corrosion, Pulse1 can deliver significantly improved accuracy. If the diagnostic objective is a more comprehensive no compromise evaluation, then combining Pulse1 with caliper will offer the best results.

Article featured in Oil and Gas Middle East   Well systems vary in complexity and cost, but they all share one fundamental duty – to transport pressurised fluids between the subsurface and surface safely, productively and profitably. And they must do so unfailingly, whilst exposed to extreme working conditions for many years, often decades.   This article will look at some of the key issues surrounding integrity management, including threats to well system integrity such as corrosion and new diagnostic strategies that are addressing them in the Middle East.   Maintaining the integrity of a well system is critical for its long-term future. Integrity failures vary in severity but in most cases can prevent the well system from functioning properly. An article by R.J. Davies contains integrity statistics from 25 different studies that reveal failure proportions around the world from 2% to 75% in more than 380,000 wells. Other frequently quoted statistics refer to alarming failure proportions in major producing areas such as 45% in the Gulf of Mexico and 34% in the UK North Sea. Integrity failures at these levels would never be tolerated by other industries, such as the airline or chemical processing sectors – so we clearly have a responsibility to improve integrity performance in ours.   Technically, well integrity depends on the collective performance of multiple ‘barriers’ that are designed to ensure that the right well fluids consistently travel to and from the right places – without compromise. Such barriers include steel tubulars, cement, valves, wellheads and a plethora of other components that form and protect precise fluid flowpaths.   To achieve this, well barriers need to have two fundamental properties – they need to be in good mechanical ‘condition’, and they need to ‘seal’. Surprisingly, despite the intimate relationship between these properties, satisfying one doesn’t imply that the other is also satisfied. A barrier may appear to be in good condition, but may not be sealing, or a barrier may be in poor condition yet still be sealing. The latter condition may be temporarily fortuitous, but poor barrier condition will eventually lead to seal failure.   This strangely inconsistent relationship between condition and seal becomes more pronounced when we try to evaluate each properly using industry-accepted diagnostic methods.   Take acoustic ‘cement bond’ or imaging techniques – used for decades to infer the success of a ‘cement job’ and annulus integrity. Advanced ultrasound scanning systems can reliably assess the strength and annular extent of the cement but cannot confirm if the cement is sealing. Similarly, multifingered calipers provide an accurate means of measuring the internal diameter of ‘primary tubulars’ and is often used to infer ‘wall thickness’ and condition – but this assumes that the outside surface diameter is ‘nominal’ or unscathed, and this may not be the case. Other examples of imperfect diagnostic techniques include using stand-alone temperature measurements or ‘spinners’ to locate primary tubular leaks. These work in certain circumstances, but not all. Effective surveillance These factors point to the need to follow three key surveillance principles in the quest for effective integrity management: firstly, evaluate both the condition and sealing performance of critical well barriers; secondly, monitor these properties routinely and proactively; finally, use the right diagnostic system for the task.   One area where these principles particularly apply is in the surveillance of ‘tubular condition’ – sometimes referred to as ‘tube integrity’ or ‘corrosion’ monitoring.   The most prolific barriers in the well system and the backbone of its integrity are the steel tubulars, casings and cement that fuse together with the subsurface to form the well system. Often operating in extreme conditions, tubulars must be in good condition to ensure containment and provide mechanical support. But many factors conspire against the integrity of the tubes making integrity management extremely challenging.   The first is accessibility. Most well tubulars exist behind the primary tubing, making them difficult to access for remediation. The second is surveillance. The hidden nature of outer casings means that corrosion and even failure is particularly insidious and challenging to detect. The third is that whilst steel barriers are strong, they are vulnerable to one fundamental weakness – they can corrode. The fourth is the environment within which tubulars need to perform. Heat, pressure, mechanical loading, aquifers and corrosive fluids such as carbon dioxide, hydrogen sulphide (H2S) and brine play havoc with steel. Lastly, the fifth factor is time. Well systems are expected to endure extreme conditions for decades. Aquifer issues The Middle East has more than its fair share of corrosion challenges. Amplifying the factors listed above are region-wide aquifers, such as the Umm er Radhuma, which inevitably corrode well systems from the outside, and high-H2S production, which can corrode from the inside. Operators in the region use several methods to combat this, including chrome completions that are resistant to attack. Some Middle East operators are also leading the way in adopting at least two of the surveillance principles above – namely, implementing proactive tube integrity surveillance, and using the most appropriate diagnostic system for the task.   TGT is a specialist in ‘through-barrier diagnostics’ for the oil and gas industry and is at the forefront of tube integrity surveillance. The company has designed and engineered a diagnostic system which harnesses electromagnetic [EM] energy to assess the condition of multiple tubulars from within the production tubing. This in-house design combines features with advanced 4D modelling to deliver impressive accuracy across multiple barriers.   Notably, the system also works in chrome completions – prolific in the Middle East and a hostile environment for ordinary EM devices. The system is being used across the region to evaluate existing corrosion issues, and proactively to track and predict tube failures before they happen.   Maintaining well system integrity is a persistent challenge, but with the correct approach in evaluating barrier condition and seal proactively, and by using reliable diagnostic systems, operators can maintain well performance – without compromise.

Well systems vary in complexity and cost, but they all share one fundamental duty – to transport pressurised fluids between the subsurface and surface safely, productively and profitably. And they must do so unfailingly, whilst exposed to extreme working conditions for many years, often decades.   This article will look at some of the key issues surrounding integrity management, including threats to well system integrity such as corrosion and new diagnostic strategies that are addressing them in the Middle East.   Maintaining the integrity of a well system is critical for its long-term future. Integrity failures vary in severity but in most cases can prevent the well system from functioning properly. An article by R.J. Davies contains integrity statistics from 25 different studies that reveal failure proportions around the world from 2% to 75% in more than 380,000 wells. Other frequently quoted statistics refer to alarming failure proportions in major producing areas such as 45% in the Gulf of Mexico and 34% in the UK North Sea. Integrity failures at these levels would never be tolerated by other industries, such as the airline or chemical processing sectors – so we clearly have a responsibility to improve integrity performance in ours.   Technically, well integrity depends on the collective performance of multiple ‘barriers’ that are designed to ensure that the right well fluids consistently travel to and from the right places – without compromise. Such barriers include steel tubulars, cement, valves, wellheads and a plethora of other components that form and protect precise fluid flowpaths.   To achieve this, well barriers need to have two fundamental properties – they need to be in good mechanical ‘condition’, and they need to ‘seal’. Surprisingly, despite the intimate relationship between these properties, satisfying one doesn’t imply that the other is also satisfied. A barrier may appear to be in good condition, but may not be sealing, or a barrier may be in poor condition yet still be sealing. The latter condition may be temporarily fortuitous, but poor barrier condition will eventually lead to seal failure.   This strangely inconsistent relationship between condition and seal becomes more pronounced when we try to evaluate each properly using industry-accepted diagnostic methods.   Take acoustic ‘cement bond’ or imaging techniques – used for decades to infer the success of a ‘cement job’ and annulus integrity. Advanced ultrasound scanning systems can reliably assess the strength and annular extent of the cement but cannot confirm if the cement is sealing. Similarly, multifingered calipers provide an accurate means of measuring the internal diameter of ‘primary tubulars’ and is often used to infer ‘wall thickness’ and condition – but this assumes that the outside surface diameter is ‘nominal’ or unscathed, and this may not be the case. Other examples of imperfect diagnostic techniques include using stand-alone temperature measurements or ‘spinners’ to locate primary tubular leaks. These work in certain circumstances, but not all. Effective surveillance These factors point to the need to follow three key surveillance principles in the quest for effective integrity management: firstly, evaluate both the condition and sealing performance of critical well barriers; secondly, monitor these properties routinely and proactively; finally, use the right diagnostic system for the task.   One area where these principles particularly apply is in the surveillance of ‘tubular condition’ – sometimes referred to as ‘tube integrity’ or ‘corrosion’ monitoring.   The most prolific barriers in the well system and the backbone of its integrity are the steel tubulars, casings and cement that fuse together with the subsurface to form the well system. Often operating in extreme conditions, tubulars must be in good condition to ensure containment and provide mechanical support. But many factors conspire against the integrity of the tubes making integrity management extremely challenging.   The first is accessibility. Most well tubulars exist behind the primary tubing, making them difficult to access for remediation. The second is surveillance. The hidden nature of outer casings means that corrosion and even failure is particularly insidious and challenging to detect. The third is that whilst steel barriers are strong, they are vulnerable to one fundamental weakness – they can corrode. The fourth is the environment within which tubulars need to perform. Heat, pressure, mechanical loading, aquifers and corrosive fluids such as carbon dioxide, hydrogen sulphide (H2S) and brine play havoc with steel. Lastly, the fifth factor is time. Well systems are expected to endure extreme conditions for decades. Aquifer issues The Middle East has more than its fair share of corrosion challenges. Amplifying the factors listed above are region-wide aquifers, such as the Umm er Radhuma, which inevitably corrode well systems from the outside, and high-H2S production, which can corrode from the inside. Operators in the region use several methods to combat this, including chrome completions that are resistant to attack. Some Middle East operators are also leading the way in adopting at least two of the surveillance principles above – namely, implementing proactive tube integrity surveillance, and using the most appropriate diagnostic system for the task.   TGT is a specialist in ‘through-barrier diagnostics’ for the oil and gas industry and is at the forefront of tube integrity surveillance. The company has designed and engineered a diagnostic system which harnesses electromagnetic [EM] energy to assess the condition of multiple tubulars from within the production tubing. This in-house design combines features with advanced 4D modelling to deliver impressive accuracy across multiple barriers.   Notably, the system also works in chrome completions – prolific in the Middle East and a hostile environment for ordinary EM devices. The system is being used across the region to evaluate existing corrosion issues, and proactively to track and predict tube failures before they happen.   Maintaining well system integrity is a persistent challenge, but with the correct approach in evaluating barrier condition and seal proactively, and by using reliable diagnostic systems, operators can maintain well performance – without compromise.