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This paper discusses the effective application of a Combination Technologies and Processes that allowed successfull abandonment of wells with Sustained casing pressure (SCP), on the Karachaganak field. The planning and execution processes of SCP elimination are examined. Previous experience in the abandonment of wells with SCP using existing procedures and methodologies for cement and bridge plug placement, on the Karachaganak field, has not always been successful. In some instances sustained casing pressure reappeared, resulting inadvertently in re-entry for intervention. In 2015 several SCP wells were successfully abandoned using a combination of technologies. The processes will be described in detail in this paper, including: Image log to enable selection of the interval for section milling Section milling - removal of a section of casing Under reaming to remove remaining cement sheath from the wall of the outer casing Inflatable Bridge Plug - mechanical barrier for placement in the opened window interval. Karachaganak is a giant gas-oil condensate field with presence of H2S and CO2. Due to that, during well abandonment SCP issue must be eliminated to comply with Republic of Kazakhstan regulation and oil industry standards. SCP, regardless of its value can pose hazards not only to the environment but also be a source of formation of man-made deposits. To ensure industrial safety, environmental expediency and to meet regulatory requirements, the wells with SCP require regular monitoring. The above mentioned technologies and processes were successfully implemented in wells abandonment and elimination of SCP on wells in the Karachaganak field. All wells were monitored throughout the year, considering the huge variance in the severe ambient weather conditions throughout, and it was proved that no issues with SCP have reoccurred so far. This paper provides well construction and integrity teams’ information on a solution that could be used in many other wells around the world. The benefits achieved by the Kazakhstan operator open up opportunities to solve SCP problems and prevent future intervention.

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Re-exploration of the existing oil fields is one of the main projects for many oil and gas companies operating in West Kazakhstan. As a part of one of such campaign carried out in 2015, the optimum logging suite was designed to acquire more detailed information about static and dynamic properties of the clastic shaly sand reservoir. It included standard logging suite, nuclear-magnetic tool and wireline formation tester. The studies were conducted in the exploration wells drilled in three different fields with different reservoir properties in order to obtain the most complete information about the formation and locate bypassed reservoirs. Wireline formation tester, in addition to standard solutions such as formation pressure and mobility profiling, downhole fluid sampling, allowed to clearly identify the reservoir saturation in the zones, where it was not possible to do with standard logging suite. Fluid analyzers integrated into the formation tester toolstring helped to clearly identify fluid type, hydrocarbon composition and vital physical and chemical properties of the formation fluid. All measurements were carried out in real-time; the decisions about acquiring downhole samples were taken situationally, not prescriptively. Study mainly focuses on thinly laminated complex clastic reservoirs with high shale content that have high uncertainty in formation water salinity estimates. As the result of this work: new oil reservoir was discovered in Middle Jurassic deposits in first field, heavy oil downhole samples were acquired in unconsolidated Lower Cretaceous sands and highly depleted gas reservoir was discovered at a depth of 400 m in the second field. In the third field, a few oil bearing intervals discovered in sub-salt low permeability Permian-Triassic formation and the most promising intervals were tested with wireline formation tester, based on this information the decision was made to drill another wells in this area to better characterize the reservoir. The integration of wireline formation tester, standard and nuclear-magnetic logging suite data, and the results of formation fluid laboratory analysis allowed to create 3-d single well simulation model to estimate the well productivity and optimize well completion design. The results of this analysis were compared with real well test data. The study shows a modern approach to the planning of additional exploration activities in producing fields fined-tuned to locate and evaluate bypassed hydrocarbon intervals, and confirm their productivity. Integrating the results of different logging suites with single well predictive modeling allowed to understand better the total well productivity. Moreover, it can further be used to optimize the completion of future wells.

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