Challenge A routine field survey discovered gas bubbling in the cellar of the subject well, right behind the conductor. None of the annuli in the well exhibited sustained pressure, complicating the task of locating the source and flowpath of the gas. The operator needed reliable diagnostic information to plan and target a remedial workover.   Analysis of cement bond and variable density logs (CBL/VDL) indicated a very poor cement bond behind the 9⅝ in. casing and, in the 9⅝ in. × 13⅜ in. pipe section overlap, there was no cement at all. After performing a pressure test of the annular space between the production tubing and the casing, and analysing samples of the bubbling gas, it was determined that the gas was coming from both the producing formation and a shallower formation. Multi Seal Integrity example well sketch. Multi Seal Integrity evaluates the seal performance of multiple barriers, locating leaks and flowpaths throughout the well system, from the wellbore to the outer annuli. Delivered by our True Integrity system with Chorus technology, Multi Seal provides a clear diagnosis of leaks and rogue flow paths so the right corrective action can be taken. Multi Seal is used in a targeted fashion to investigate a known integrity breach anywhere in the well system. Barriers can also be validated proactively to confirm integrity. Either way, Multi Seal provides the insights needed to restore or maintain a secure well. Solution The operator selected TGT’s Multi Seal Integrity product using the Chorus (acoustic) platform and the Indigo high-precision temperature modules to perform a leak detection survey that would reveal both the source and the flowpath of the gas bubbling at surface.   In contrast to traditional production logging methods, the Chorus acoustic system can identify minor fluid or gas migration behind multiple steel and cement barriers. The system’s sensitive hydrophones can capture and characterise acoustic signatures associated with fluid flow through micro-annuli, cement channels and leaks in completions, or filtration through pores in the formation. Figure 1: The final confirmation survey (left) showed that the source of the migrating gas had been sucessfully isolated. The cellar of the well still shows signs of bubbling due to remnant gas present in the well system, but this had cleared approximately one month after the workover. Result The complex flowpath started in the active reservoir, with gas moving up behind the 9⅝ in. casing, with further contributions from two shallower formations. The gas continued up behind 9⅝ in. casing to the 13⅜ in. casing shoe, then up behind the 13⅜ in. casing and finally behind the 20 in. casing to the surface. The operator developed a remediation plan based on this detailed understanding. The accuracy of the leak determination made it possible to avoid unnecessary workover-related activities and enabled the operator to minimise nonproductive time.   Several validation surveys were deployed to assess the effectiveness of the workover operations (Figure 1). After completion of the last corrective cementing job, the final survey showed that the source of gas migration had been successfully isolated, although the cellar still showed signs of bubbling. The cause of this bubbling was that gas present in the system was still travelling through the well to reach the surface. This remnant gas left the system approximately one month after intervention, and the well showed no further signs of gas migration at surface.   TGT’s Multi Seal Integrity product enabled the field operator to identify the gas source and shut it off. Methane is 80x more potent as a greenhouse gas (GHG) than carbon dioxide and it constitutes roughly 20% of all global GHG emissions. Eliminating fugitive methane emissions from the well helped to restore integrity and reduce the carbon intensity of energy production.

The company’s vision and motivator is the thirst for a greater knowledge of the well system, which combines the well completion and reservoir TGT Oilfield Services, the market leader in through-barrier diagnostics for the oilfield, has grown year-on-year even during the downturn and the company expects to see an improvement in both activity levels and pricing as the industry stabilises further.   "Despite the drop in oil price, the demand for TGT diagnostic services grew significantly. Our focus on technology and applications that diagnose the performance and integrity of existing wells is exactly what our clients needed during the tough budget years.   "We expect that need to continue. We protect our market share and growth by continuing to fund technology development despite the market climate. Customers recognise the depth of our technical and sub surface knowledge, which has been built up over the last 20 years," says Maged Yassin, business unit manager, TGT Saudi Arabia. The company’s vision and motivator is the thirst for a greater knowledge of the well system, which combines the well completion and reservoir. This speaks for itself when one considers that more than a third of its headcount is dedicated to R&D and technology development, says Yassin.   Recently, TGT migrated its sensors to a custom-built ‘low-noise’ hardware – Indigo – designed to operate at ‘low noise’ so not to interfere with its acoustic-based ‘spectral’ and electromagnetic-based ‘EmPulse’ diagnostic systems.   Additionally, the company added a real-time capability to its fleet of through-barrier diagnostic systems. The new real-time technology enables well data to be viewed and analysed at surface during the execution of well diagnostic programmes without compromising on measurement fidelity. "We never stop, continuously improving our services and our offerings," says Yassin.   TGT provides a wide range of through-barrier diagnostics. Patented technologies are deployed on any conveyance and sense beyond the well bore to answer multiple reservoir flow and well integrity questions. The company offers these services in Saudi Arabia via in-country assets, geoscience and advanced interpretation as well as business development and field operations. TGT was founded on research and development. "Our technologies include advanced flow profiling deep into the reservoir, unconventional and fracture flow, multi annuli leak detection and multi barrier corrosion among others. We pride ourselves not only on equipment technology but also advanced geoscience and interpretation capabilities," he says.   "Saudi Arabia represents one of our most significant markets," he says. TGT has in place a stringent Saudisation development plan and technical knowledge transfer through academia alliances. Referring to Saudi Aramco’s In-Kingdom Total Value Add (IKTVA) plan, he says the published target is 35 per cent by 2020. "TGT will comply with or exceed these targets on all fronts (equipment, human capital, safety and environment) as we establish ourselves further in the kingdom," he asserts. On the company’s relationship with Saudi Aramco, he says Aramco is a highly sophisticated organisation, with a strong emphasis on strategic planning to optmise operations.   "Our relationship, like with all our customers, is built on a foundation technical competence, respect for the accuracy of the results we provide and our service delivery. We ensure we understand the customer’s challenges before designing a bespoke programme to determine the answers they seek," he says.   Referring to business growth, Yassin says business has gradually improved in the last two years in terms of activity.   Pricing of services remains a challenge. The significant rebound of oil price will soon cascade to the market to ensure continued technology development and growth.   "TGT Saudi Arabia is one of our key dedicated business units, supported by a solid global infrastructure. While we continue to expand our global footprint, we will ensure we stay focused on our customers, proving the quality of our diagnostic results, striving to set ourselves apart from our competition," he says.

The company’s vision and motivator is the thirst for a greater knowledge of the well system, which combines the well completion and reservoir TGT Oilfield Services, the market leader in through-barrier diagnostics for the oilfield, has grown year-on-year even during the downturn and the company expects to see an improvement in both activity levels and pricing as the industry stabilises further.   "Despite the drop in oil price, the demand for TGT diagnostic services grew significantly. Our focus on technology and applications that diagnose the performance and integrity of existing wells is exactly what our clients needed during the tough budget years.   "We expect that need to continue. We protect our market share and growth by continuing to fund technology development despite the market climate. Customers recognise the depth of our technical and sub surface knowledge, which has been built up over the last 20 years," says Maged Yassin, business unit manager, TGT Saudi Arabia. The company’s vision and motivator is the thirst for a greater knowledge of the well system, which combines the well completion and reservoir. This speaks for itself when one considers that more than a third of its headcount is dedicated to R&D and technology development, says Yassin.   Recently, TGT migrated its sensors to a custom-built ‘low-noise’ hardware – Indigo – designed to operate at ‘low noise’ so not to interfere with its acoustic-based ‘spectral’ and electromagnetic-based ‘EmPulse’ diagnostic systems.   Additionally, the company added a real-time capability to its fleet of through-barrier diagnostic systems. The new real-time technology enables well data to be viewed and analysed at surface during the execution of well diagnostic programmes without compromising on measurement fidelity. "We never stop, continuously improving our services and our offerings," says Yassin.   TGT provides a wide range of through-barrier diagnostics. Patented technologies are deployed on any conveyance and sense beyond the well bore to answer multiple reservoir flow and well integrity questions. The company offers these services in Saudi Arabia via in-country assets, geoscience and advanced interpretation as well as business development and field operations. TGT was founded on research and development. "Our technologies include advanced flow profiling deep into the reservoir, unconventional and fracture flow, multi annuli leak detection and multi barrier corrosion among others. We pride ourselves not only on equipment technology but also advanced geoscience and interpretation capabilities," he says.   "Saudi Arabia represents one of our most significant markets," he says. TGT has in place a stringent Saudisation development plan and technical knowledge transfer through academia alliances. Referring to Saudi Aramco’s In-Kingdom Total Value Add (IKTVA) plan, he says the published target is 35 per cent by 2020. To celebrate, TGT invited employees, customers, and business partners to an evening which relived the company’s scientific breakthroughs using acoustic, thermal and electromagnetic energy to reveal unique answers within and beyond the well bore.   Dr. Arthur Aslanyan, TGT’s Co-Founder commented, “It gave me great pride to attend the event and celebrate the company's 20th anniversary. We have come a long way since we first started the business. We are very excited about our future as the company continues to thrive”.   The event was attended by Saad Bargach, TGT Chairman and LimeRock Partners -private equity investors.   Hegazi continued, “Looking to our future, TGT is releasing several lines of new technologies and applications in coming months to further cement our position as pioneers of Through-Barrier Diagnostics. Our patent technology developments coupled with our unrivalled Geoscience organisation and global footprint, provide unique and reliable diagnostic services to our customers. This has been key in maintaining our fast growth trend and industry reputation. I am confident this foundation along with our excellent teams, will continue to fuel our growth for many years to come. "TGT will comply with or exceed these targets on all fronts (equipment, human capital, safety and environment) as we establish ourselves further in the kingdom," he asserts. On the company’s relationship with Saudi Aramco, he says Aramco is a highly sophisticated organisation, with a strong emphasis on strategic planning to optmise operations.   "Our relationship, like with all our customers, is built on a foundation technical competence, respect for the accuracy of the results we provide and our service delivery. We ensure we understand the customer’s challenges before designing a bespoke programme to determine the answers they seek," he says.   Referring to business growth, Yassin says business has gradually improved in the last two years in terms of activity.   Pricing of services remains a challenge. The significant rebound of oil price will soon cascade to the market to ensure continued technology development and growth.   "TGT Saudi Arabia is one of our key dedicated business units, supported by a solid global infrastructure. While we continue to expand our global footprint, we will ensure we stay focused on our customers, proving the quality of our diagnostic results, striving to set ourselves apart from our competition," he says.

Challenge The gas-lift producer in this case study had been shut-in due to sustained annulus pressure (200 bar) and excessive volumes of H2S that could not be handled by the production facilities. The operator wanted to assess primary barrier integrity and guide a workover programme. Traditional diagnostics methods, such as production logging tools (PLT) and temperature logs, were deemed inefficient because they could scan only the production tubing and were unable to confirm the integrity of the packer and production casing. Identifying and shutting off the source of the water with high H2S content would protect the environment and deliver a production gain of 2,050 barrels of oil per day (BPD). Eliminating the production of highly toxic H2S and ensuring its containment within the well system would also deliver important environmental and safety benefits. Figure 1: Failures in the gas-lift mandrels (or gas-lift valves) were indicated by Chorus spectral acoustic diagnostics. Conventional production logging tools failed to identify any of these leaks. Solution TGT’s True Integrity system with Chorus technology uses spectral acoustic methods to assess barrier sealing performance. The system offers a large scanning radius and the sensitivity to detect even small leaks. The ability to indicate failures in the tubing, in the casing behind the tubing, and in key completion components such as the production packer and gas-lift mandrels makes this technology highly effective at establishing the best approach for remediation when barrier failures occur.   High precision surveys across the reservoir zone characterised the flow and its content, thereby guiding operations for shutting off the water zone with high H2S content. Traditional PLT methods would not have been enough to make this identification as the water source may be above or below the perforated interval. The diagnostics also revealed the effectiveness of cement sealing across the reservoir zones. Figure 2: Reservoir crossflow under shut-in and bleed-off conditions. The zone at 13,440 ft shows flow upwards and downwards and charges the wellbore with water. This zone was isolated using a straddle packer. Result The Multi Seal Integrity product with Chorus technology revealed leaks in all four of the well’s gas-lift mandrels (Figure 1). Having confirmed that the failures were only in the mandrels, the operator changed them using the slickline, thereby eliminating the issue of sustained annulus pressure. Traditional sensors, such as spinner, resistivity and capacitance had not identified an issue in the mandrels, which indicates that the leaks were below their detection thresholds.   TGT’s diagnostics solution also identified an active crossflow between the perforated intervals in this well (Figure 2). The direction and content of the crossflow were determined, indicating which zone had to be isolated. Verifying cement integrity behind the casing enabled the operator to select a cost-effective isolation programme that involved running straddle packers across the interval that was producing the water containing H2S.   After the workover, the well returned to H2S-free production with oil rate increased by 2,050 BPD and reduction in water cut from 96 to 80%. Increased oil production at a reduced water cut boosts recovery efficiency, enabling the operator to extract hydrocarbons in a shorter time period, and to reduce energy consumption and carbon- per-barrel over the life of field. In addition, having less water to manage and treat at surface reduces the energy requirement and emissions associated with these processes.

Diagnostics Behind the Barriers A wide range of tubulars are tested in the EmPulse characterization facility at TGT Oilfield Services’ technology center in Kazan, Russia, to ensure accurate metal wall thickness measurements. Wall thickness is an indicator of barrier condition.   A wide range of tubulars are tested in the EmPulse characterization facility at TGT Oilfield Services’ technology center in Kazan, Russia, to ensure accurate metal wall thickness measurements. Wall thickness is an indicator of barrier condition.   Alongside those efforts, companies are increasingly recognizing the value of using diagnostic systems to detect issues that compromise well barriers. “Because most well integrity problems occur in the outer periphery of the well, behind barriers such as tubulars and cement, a process for sensing and locating leaks, or flow paths along the annulus, is crucial,” said Ken Feather, Chief Marketing Officer, TGT Oilfield Services. The company provides “through-barrier” diagnostics using thermal, electromagnetic (EM) and acoustic energy.   The EmPulse multi-tube imaging system produces tube integrity diagnostics. Measurements performed from within the 3 1/2-in. production tubing show significant corrosion in the 13 3/8-in. casing, quantifying metal loss of 34% and 44% in the third barrier.   The EmPulse multi-tube imaging system produces tube integrity diagnostics. Measurements performed from within the 3 1/2-in. production tubing show significant corrosion in the 13 3/8-in. casing, quantifying metal loss of 34% and 44% in the third barrier.   “Barriers, such as tubulars, cement, elastomers, packers and valves must be in good condition and must have good sealing performance,” he noted. “A barrier may look to be in good condition but not sealing. The mechanical properties of cement, for example, may be robust and provide coverage around the annulus, but it may not be sealing properly because of invisible micro-annuli or cracks that cause unwanted flow paths.” Additionally, cement, tubulars and other zonal isolation components experience degradation over time.   EmPulse multi-tube imaging, in its fourth generation, combines electromagnetic sensors with proprietary measurement and modeling techniques to measure the wall thickness of metal tubulars in well systems. “Wall thickness is an indicator of barrier condition and is used to quantify corrosion, which is progressive over time. Severe corrosion can lead to seal failures, leaks and unwanted flow paths, so routine surveillance is important,” Mr Feather said. In the Middle East, known for highly corrosive aquifers, the system has quantitatively recorded the individual tubular thickness of up to four concentric barriers. Pulse characterisation lab The acoustic-based spectral cement channel detection system records and analyzes the sound spectrum in the wellbore to detect the presence of fluid flow in otherwise undetectable micro-cracks or channels within annular cement that can result in leaks along the annulus after the well is put on production.   “From a production standpoint, this capability is important, particularly where one reservoir is communicating with another in a producing well,” he noted. “In water injection wells, the technique can confirm if the injected water is reaching the target reservoir or being diverted elsewhere.” Integrity failures resulting in sustained annulus pressure are often visible at the surface before problems escalate, so operators are embracing diagnostics as a proactive method for preventing zonal isolation issues, particularly in the Middle East, he said. “Historically, the industry has been reactive, but we believe there are significant benefits in conducting surveillance regularly and routinely to monitor the tube integrity and seal integrity of wells barriers.”

Diagnostics Behind the Barriers A wide range of tubulars are tested in the EmPulse characterization facility at TGT Oilfield Services’ technology center in Kazan, Russia, to ensure accurate metal wall thickness measurements. Wall thickness is an indicator of barrier condition.   A wide range of tubulars are tested in the EmPulse characterization facility at TGT Oilfield Services’ technology center in Kazan, Russia, to ensure accurate metal wall thickness measurements. Wall thickness is an indicator of barrier condition.   Alongside those efforts, companies are increasingly recognizing the value of using diagnostic systems to detect issues that compromise well barriers. “Because most well integrity problems occur in the outer periphery of the well, behind barriers such as tubulars and cement, a process for sensing and locating leaks, or flow paths along the annulus, is crucial,” said Ken Feather, Chief Marketing Officer, TGT Oilfield Services. The company provides “through-barrier” diagnostics using thermal, electromagnetic (EM) and acoustic energy.   The EmPulse multi-tube imaging system produces tube integrity diagnostics. Measurements performed from within the 3 1/2-in. production tubing show significant corrosion in the 13 3/8-in. casing, quantifying metal loss of 34% and 44% in the third barrier.   The EmPulse multi-tube imaging system produces tube integrity diagnostics. Measurements performed from within the 3 1/2-in. production tubing show significant corrosion in the 13 3/8-in. casing, quantifying metal loss of 34% and 44% in the third barrier.   “Barriers, such as tubulars, cement, elastomers, packers and valves must be in good condition and must have good sealing performance,” he noted. “A barrier may look to be in good condition but not sealing. The mechanical properties of cement, for example, may be robust and provide coverage around the annulus, but it may not be sealing properly because of invisible micro-annuli or cracks that cause unwanted flow paths.” Additionally, cement, tubulars and other zonal isolation components experience degradation over time.   EmPulse multi-tube imaging, in its fourth generation, combines electromagnetic sensors with proprietary measurement and modeling techniques to measure the wall thickness of metal tubulars in well systems. “Wall thickness is an indicator of barrier condition and is used to quantify corrosion, which is progressive over time. Severe corrosion can lead to seal failures, leaks and unwanted flow paths, so routine surveillance is important,” Mr Feather said. In the Middle East, known for highly corrosive aquifers, the system has quantitatively recorded the individual tubular thickness of up to four concentric barriers.   The acoustic-based spectral cement channel detection system records and analyzes the sound spectrum in the wellbore to detect the presence of fluid flow in otherwise undetectable micro-cracks or channels within annular cement that can result in leaks along the annulus after the well is put on production.   “From a production standpoint, this capability is important, particularly where one reservoir is communicating with another in a producing well,” he noted. “In water injection wells, the technique can confirm if the injected water is reaching the target reservoir or being diverted elsewhere.” Integrity failures resulting in sustained annulus pressure are often visible at the surface before problems escalate, so operators are embracing diagnostics as a proactive method for preventing zonal isolation issues, particularly in the Middle East, he said. “Historically, the industry has been reactive, but we believe there are significant benefits in conducting surveillance regularly and routinely to monitor the tube integrity and seal integrity of wells barriers.” Pulse characterisation lab