Challenge A high gas–oil ratio leads to unnecessarily high carbon emissions, lower oil production and increased carbon-per-barrel rates. Managing and processing excess gas requires substantial energy and capital expenditure for surface infrastructure and facilities. In this case, the aim was to identify zones for gas shut-off that would enable the operator to optimise surface infrastructure capacity, maximise oil production and minimise carbon footprint.   Well A-1 features a 7 in. x 4-1/2 in. cemented liner across several commingled oil and gas-bearing zones. Developing compartmentalised multi-stacked reservoirs using simplified well completions makes it challenging for diagnostics to determine production allocation, reveal flow assurance issues, understand reservoir connectivity, monitor individual well performance, and forecast total field production.   Gas production had already exceeded the limit of surface processing facilities for well operation with existing production rates, which meant the operator had to choke back production. In addition, the unwanted gas was taking up part of the operator’s pipeline quota and creating other transportation and flow assurance issues. The well contains at least five clastic reservoir zones, each with multiple layers, that are perforated across an interval of more than 1,500 ft. This level of complexity meant that conventional production logging tools were unable to adequately characterise flow or confidently distinguish the main gas-contributing layers. Total Flow example well sketch. Total Flow locates and quantifies wellbore and reservoir flow, and reveals the relationship between the two. Delivered by our True Flow system with Chorus and Cascade technology, Total Flow provides the clarity and insight needed to manage well system performance more effectively. Total Flow is commonly used to diagnose unexpected or undesirable well system behavior, but it can also be used proactively to ensure the well system is working properly. Solution The operator selected TGT’s Total Flow product, with Cascade, Chorus and Indigo as the main technology platforms chosen to perform the well system diagnostic survey. This would reveal which zones were contributing to the production of oil and gas, diagnose wellbore and reservoir flows, and help identify potential well integrity issues such as annulus sealing problems due to poor cement. The solution combines the sensitive, fast-response temperature sensor of the Indigo platform with high-definition acoustic sensing from Chorus that reveals active flow in the well system.   Comprehensive temperature and flow modelling with Cascade enabled TGT analysts to assess and allocate production distribution and provide accurate oil and gas flow profiles across the reservoir zones. The survey also identified active flow layers and recorded characteristic acoustic signals generated by liquid and gas flowing through reservoir media and the wellbore. Pre- and post-workover survey results illustrate the effectiveness of the gas zone isolation programme and resulting decrease of gas production, which enabled surface infrastructure to stay within its operating envelope. Result Total Flow diagnostics quantified the contribution of reservoir layers from five different zones and identified the main gas producing layers, providing a comprehensive flow profile. The operator was able to define active flow units and differentiate between flows through the reservoir matrix, the behind-casing channels and the wellbore completion components.   This enabled the operator to target and conduct an effective remediation plan. The workover involved a 200-ft-long 2-⅞- in. straddle installed to isolate the zone with the highest gas contribution. A post-workover Total Flow survey was conducted to evaluate the effectiveness of the isolation job. The straddle had isolated 83% of the gas production. This delivered a reduction of 7.9 MMscf per day at surface (equivalent to 2.8 Bscf per year).   Overall, the isolation job was considered highly successful. Identifying the main gas shut-off zones played a crucial role in optimising surface infrastructure, maximising oil production, and minimising carbon footprint for this well.

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.

Challenge The subject well was not reaching its planned gas production rate, so the field operator wanted to investigate the issue and identify the root cause. The assumption was that both the hydraulically fractured reservoir zones were contributing to production, thus the first task was to assess the relative contributions of gas from each layer. Water production was also an issue and can be a critical problem in a gas well. The second challenge was, therefore, to identify where water was entering the well in order to plan a workover operation.    The tubing installed in this gas producer well extends below the bottom perforation interval, which means that conventional production logging tool surveys cannot help with evaluation. Total Flow is commonly used to diagnose unexpected or undesirable well system behavior, but it can also be used proactively to ensure the well system is working properly. Solution The subsurface team of reservoir and petroleum engineers at AGL Energy Ltd selected TGT’s Total Flow product to locate and quantify wellbore and reservoir flow and reveal the relationship between the two. Delivered by the True Flow system with Chorus and Cascade technology, Total Flow provides the clarity and insight operators need to manage well-system performance more effectively. Total Flow is commonly used to diagnose unexpected or undesirable well-system behaviour, but it can also be used proactively to ensure that a well system is working properly.   In this case, the combination of Cascade flow modelling and Chorus acoustic sensing enabled TGT analysts to generate an accurate multiphase flow profile for the well and provide the operator with a clear picture of what was happening behind the casing and below the survey interval. The maximum survey depth during the flowing regime was X204 m, which means that the bottom perforated interval (X207–X209 m) was not surveyed. The TFM curve shown in the TEMPERATURE track is the modelled flowing temperature profile. It is matched with TEMP_F1D1 down to the maximum surveyed depth and shows the assumed temperature behaviour below this depth. Result The temperature simulation and flow modelling results from TGT’s Cascade platform identified the main inflow zones and showed that 48% of total gas and 44% of total water were entering the well from the bottom perforated interval. This indicated that about 93% of the total gas flow rate and 100% of the water was from the bottom-zone Wallabella Sandstone Formation. The upper fractured zone (the Tinowon reservoir) was not making a significant contribution to gas production, thus the well could not reach its planned production performance.   The operators can apply these insights to develop an effective plan for future workover and stimulation tasks.   The small volume of gas produced from the Lower Tinowon Sandstone Formation is the result of behind-casing channelling, which would not have been identified by conventional production logging tools.

Dubai, UAE – 1 June 2021 TGT announced today that its ‘Pulse1’ brand won Gold for “Best visual identity from the energy and utilities sector”, Bronze for “Best internal communication during a brand development project”, and Bronze for “Best development of a new brand within an existing brand portfolio”, at last week’s eighth annual Transform Awards MEA 2021.   This is the second cluster of brand accolades in the space of only 12-months, following its Gold and Silver success at last year’s Transform Awards for the total brand transformation of its ‘TGT Diagnostics’ parent brand.   This is a tremendous achievement for the company and a credit to our talented brand team”, commented Ken Feather, Chief Marketing Officer, TGT. “We engineered and produced all aspects of the Pulse1 brand completely in-house, from consumer research to positioning, developing brand codes, sales collateral, media content and executing an ambitious communications campaign. To win alongside so many iconic brands and professional brand agencies is an outstanding result. I’m very proud of the team”, continued Ken.   Pulse1 is the newest addition to TGT’s family of diagnostic platforms, and a key ingredient in its ‘True Integrity’ products. Powered by advanced electromagnetics, Pulse1 technology was created to deliver “no compromise” integrity management to oil and gas producers globally. This industry-first development overcomes the drawbacks of current technologies to enable a more accurate assessment of well integrity, helping energy producers keep wells safe, clean and productive.   “Our research revealed that consumers weren’t happy with current diagnostics and were willing to pay a premium for something better. Our Technology Centre team did an amazing job perfecting the technology, giving us just the right ingredients to work with, and we needed an equally powerful brand that would resonate with our clients and stand out in a competitive market. We launched Pulse1 last summer and uptake has been phenomenal”, added Ken. Established in 2009, the annual Transform Awards recognise the most innovative, creative and successful brand work across the world. Covering seven regions, this prestigious awards programme focuses on specific aspects of the branding process and provides a platform to benchmark and showcase exemplary work in brand strategy and development.   Andrew Thomas, publishing editor of Transform magazine and founder of the Transform awards, says, “Over the past eight years, the work we have seen entered in the awards programme has been consistently good, both here and globally. Everyone who has won this year should be proud of their accomplishments.”   Commenting on the Pulse1 brand, Andrew added, “It’s a clever, visually straightforward yet adaptable brand that allows for a breadth of communication to be delivered within a consistent brand strategy. Judges praised the way TGT was able to simplify the complex communications in the industry.”   With its brand transformation efforts successfully implemented, TGT continues to focus on providing diagnostic solutions that help the oil and gas industry reduce emissions and achieve carbon-zero targets, enabling a sustainable energy future for everyone. Transform Awards MEA 2021 winners

New fracture flow diagnostics help operators elevate fracture performance (in the Permian) Article featured in Harts E&P   In recent years, the Permian basin is been the most prolific shale play in the US. Production in this area increased to 3.8 million barrels by 2019, representing almost 70% of the whole US production growth from 2011 to 2019 according to International Energy Agency (IEA). The impressive aspect of this achievement is that the growth has not stopped. On the contrary, the Permian is expected to continue growing and is estimated to achieve up to 5.8 million barrels by the end of 2023.   Such impressive growth doesn’t come easy. Significant advances in drilling, completing and multi-stage fracturing will continue to drive production increases. But evaluating the performance of fracturing programmes and the wells they deliver is key to optimising resources and ensuring maximum return on investment. Conventional diagnostics [such as production logging tools or ‘PLT’s’] can’t provide all the insights required to ensure the operator is achieving the best returns. This article focuses on the challenges faced when assessing unconventional reservoirs in terms of production, and features a new diagnostic capability introduced by TGT to evaluate the flow performance of hydraulically fractured wells, stage-by-stage. The new diagnostic product is aptly called ‘Fracture Flow’.   Operators have been drilling aggressively and pushing the boundaries of hydraulic fracturing beyond conventional standards compared to other plays. The drilled length of lateral sections has been constantly boosted, adding more footage as well as more production stages. The ultimate objective is to penetrate deep into the target formation increasing the area of contact with the specific reservoir or formation making the well, its completion and the reservoir one dynamic production system. Piezo crystals used in the Chorus tools and sensorThrough barrier diagnostics Champions of this approach include a Houston-based operator that recently drilled such a well at the Wolfcamp. The completion included a lateral section of more than 17,900 ft running through the Spaberry formation. The completed well had a total measured depth exceeding 24,500 ft with a customised completion design and fracking treatment. The completion included more than 50-stages and sand was pumped along more than 2,200 ft of reservoir to increase the well productivity.   These extended laterals have been engineered to optimise production performance and leverage improvements in drilling, fracking treatments and completion designs. The operators have overcome the number of well construction challenges and have quickly moved up a steep learning curve.   Like the challenges encountered with well construction, the Permian basin faces its own challenges. Following such an extensive multistage hydraulic fracturing programme, the wells are brought onstream at high initial production rates. But most of these extended-lateral producers tend to decline dramatically over a very short period. To help combat this challenge, and many others, TGT has developed a number of application-specific diagnostic products using its ‘True Flow System’ to quantitively evaluate flow dynamics throughout the entire well system – from reservoir to the wellbore, and the dynamic interplay between the two.   When talking about a hydraulic fracturing job, we all know the importance of the programme design prior to execution. During this phase, sophisticated software is utilised to model and optimise the fracturing programme, taking into consideration multiple variables. These variables include formation properties, lithology, depth, mechanical stresses and other parameters that can affect the final outcome. Another important consideration is the formulation of the hydraulic fracturing fluid. This fluid is normally comprised of sand (or proppant), gels (foam or sleek-water) and additives that are pumped downhole following the job design to prop open the induced fractures and maximise the extension of the fracture in terms of length, height and aperture as well as the integrity of the fractured conduit itself, so hydrocarbons can flow unabated.   TGT’s diagnostic ‘Fracture Flow’ product is able to locate and evaluate fracture inflows and quantify inflow profiles in hydraulically fractured wells. The product is delivered by our analysts using the ‘True Flow System’, which combines several technology platforms – Chorus (acoustic), Cascade (thermal), Indigo (multisense) and Maxim (digital workspace), to acquire, interrogate and analyse the acoustic spectra and temperature changes generated by the hydrocarbons or any other fluid flowing from the reservoir through active fractures and into the completion. This diagnostic capability goes beyond conventional flow measurement techniques that generally stop sensing at the wellbore and are therefore unable to quantify flow within the reservoir itself.   The Fracture Flow product extract shown in figure-1 represents the diagnosis of a hydraulically fractured oil producer with >80 degrees deviation. The reservoir has a gross thickness of approximately 1,200 ft and is fully cased. ‘Fracture Flow’ diagnostics compare fractured intervals [blue] to main producing intervals [green] at different choke sizes in order to evaluate the true effectiveness of hydraulic fracturing programmes and maximise well performance. The operator’s objectives in this case were to evaluate the post-fracture performance of three zones, and in particular: Compare the effectiveness of fractured stages by assessing the production contribution from each fractured interval Identify crossflow or behind-casing communication Increase production efficiency by identifying the optimum production choke for this well system.   The results revealed by the Fracture Flow analysis clearly revealed that the fractured intervals (figure-1 – blue coding) were not contributing fully to production in their entirety. Furthermore, it identified exactly the active zones and where the main production was coming from (figure-1 green coding). Fracture Flow revealed that only 62%, 59% and 56% of each zone was actually producing at the outset.   The Fracture Flow analysis also indicated that there were no crossflows among the three zones which was another key finding from an integrity perspective.   Thirdly, the Fracture Flow diagnostic programme helped to determine the optimal choke size required to ensure that the fractured zones were contributing at maximum rate.   TGT work in close collaboration with operators using Fracture Flow to help them reach their frac evaluation objectives; locate effective fracture inflows; quantify inflow profiles; and assess the effectiveness of fracture programmes, helping to optimise future programmes and maximise return on investment. TGT is an international diagnostics company that specialises in ‘through-barrier diagnostics’ for the oilfield. Our Houston-based operation provides unique ‘True Flow’ and ‘True Integrity’ diagnostics to operators throughout the United States, including the Permian. We are also working actively in deep water Gulf of Mexico, Latin America and other major basins around the globe.

Challenge Multistage fracturing is an effective stimulation technique for heterogeneous, low-permeability oil reservoirs. However, after a fracturing campaign, there may be a risk of increased communication between the water-bearing formation, which may cause a high water cut in the stimulated well.   In this case from the Volga-Ural region of Russia, the operator wanted to identify unexpected water sources in a horizontal well in a low-permeability carbonate reservoir. The well had been subjected to a multistage acid fracturing job and it was necessary to determine the most effective strategy for a workover to shut off the water producing zones. Well sketch shows flow scenarios before and after fracturing that Fracture Flow can evaluate. Fracture Flow provides the clarity and insight needed to manage well system performance more effectively. Solution The operator selected TGT’s Fracture Flow product to understand the flow dynamics of the well system and identify the water sources. Fracture Flow is delivered by the True Flow diagnostic system. TGT’s diagnostic systems combine several proprietary technology platforms that share a common structure and workflow comprising programs and methods; tools and measurements; processing and modeling; and analysis and interpretation.   The Chorus (acoustic) platform records and analyses the acoustic energy produced by fluid flow; its role in this case was to help pinpoint unexpected flow activity behind casing. The Fracture Flow product uses a multi-sensor tool, adopts a unique data acquisition programme and utilises a processing and modelling software plugin which varies from the other True Flow products.   In combination, the technique is able to identify the location and determine the distance of the acoustic signal from the receiver. It is therefore able to distinguish reservoir flows from those generated by completion leaks. Integrated logging suite results: Acoustic signal source identification Result An acoustic signal was recorded in a narrow interval above the target reservoir. This signal had a broadband spectrum that could have been generated by reservoir flow or by a completion leak (see Line A in Figure 1).   Taking into consideration the well design and the acoustic wave propagation in the wellbore and rocks, TGT’s Chorus diagnostics determined that the location of the acoustic source extended beyond the wellbore. It was deduced that the signal was generated by turbulent flow from an unexpected fracture above the target reservoir. The inflow fluid from this unwanted fracture flowed back down the well completion, entering the wellbore through the topmost perforation. It was this rogue fracture that was the cause of water in the well production.   Thanks to Fracture Flow’s diagnostic results, the operator changed the hydraulic fracturing design programme, to optimise production while preventing the reoccurrence of rogue fractures in the future.