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Kelasu gas field in Tarim Basin is characterized by ultra-deep (6500-8000m), ultra-high temperature (160-19°C) and ultra-high reservoir pressure (110-136MPa). The wellhead pressure during production is also as high as 80-100MPa. Rigless well intervention is always difficult to perform because of the high well control risks. Slickline testing, electric line testing and optical fiber monitoring have all been tried, but problems like breaking of slickline, loss of signal, falling of instruments into well, etc. were encountered. A slickline fishing technology has been used for bottom hole well surveillance in this area with many optimizations on the instruments. Grease injection sealing assisted by packing sealing is used to reduce friction of slickline and to guarantee well safety during operation; a choke tube stabilization device is invented to deal with the eccentric wearing of slickline and choke tube; self-supporting lever together with 8 anchor ropes are used to stabilize the blowout prevention tube assembly to withstand the high wind in the mountainous area; grease collection device is used to avoid the discharge of grease into the environment. The technology has been successfully used in more than 70 wells in Kelasu gas field. The interventions include production testing, pressure built up (PBU) testing and well interference test. The maximum setting depth of the manometer reaches 7189 m. The highest wellhead pressure during testing reaches 90 MPa. Longest pressure survey time comes up to 52 days. No surface or downhole problems have been encountered and all the required data have been acquired. The wells were not killed during the intervention so the reservoir is well protected. Well interference tests were conducted in Keshen 8 block using this technology. The results showed very good interwell connectivity and suggested that well spacing should be enlarged. The development program of this block was adjusted accordingly and it turned out that the expected production rate was achieved with 4 less wells. Besides, the drilling thickness of the target formation was reduced from 200m to 130m and the same well productivity was also obtained. Now the slickline fishing bottom hole pressure survey technology has been extensively used in the ultra-deep HTHP wells in Kuqa Foreland Area. It has been field proven for simple operating, less cost and formation protection. It can be used anytime in the life cycle of a well to evaluate the reservoir dynamic data, to deploy new wells and to optimize the production system of existing wells.
Kelasu gas field in Tarim Basin is characterized by ultra-deep (6500-8000m), ultra-high temperature (160-19°C) and ultra-high reservoir pressure (110-136MPa). The wellhead pressure during production is also as high as 80-100MPa. Rigless well intervention is always difficult to perform because of the high well control risks. Slickline testing, electric line testing and optical fiber monitoring have all been tried, but problems like breaking of slickline, loss of signal, falling of instruments into well, etc. were encountered. A slickline fishing technology has been used for bottom hole well surveillance in this area with many optimizations on the instruments. Grease injection sealing assisted by packing sealing is used to reduce friction of slickline and to guarantee well safety during operation; a choke tube stabilization device is invented to deal with the eccentric wearing of slickline and choke tube; self-supporting lever together with 8 anchor ropes are used to stabilize the blowout prevention tube assembly to withstand the high wind in the mountainous area; grease collection device is used to avoid the discharge of grease into the environment. The technology has been successfully used in more than 70 wells in Kelasu gas field. The interventions include production testing, pressure built up (PBU) testing and well interference test. The maximum setting depth of the manometer reaches 7189 m. The highest wellhead pressure during testing reaches 90 MPa. Longest pressure survey time comes up to 52 days. No surface or downhole problems have been encountered and all the required data have been acquired. The wells were not killed during the intervention so the reservoir is well protected. Well interference tests were conducted in Keshen 8 block using this technology. The results showed very good interwell connectivity and suggested that well spacing should be enlarged. The development program of this block was adjusted accordingly and it turned out that the expected production rate was achieved with 4 less wells. Besides, the drilling thickness of the target formation was reduced from 200m to 130m and the same well productivity was also obtained. Now the slickline fishing bottom hole pressure survey technology has been extensively used in the ultra-deep HTHP wells in Kuqa Foreland Area. It has been field proven for simple operating, less cost and formation protection. It can be used anytime in the life cycle of a well to evaluate the reservoir dynamic data, to deploy new wells and to optimize the production system of existing wells.
OBJECTIVE/SCOPE Artificial lift systems, such as electrical submersible pumps (ESPs), need to be placed as close to the reservoir as possible to maximize their performance and increase longevity. Horizontal wells require setting of the ESP packer in a highly deviated section, where installation of temporary barriers to facilitate the setting of such a packer is a challenge. A feasible solution to this challenge has been identified in a robotic e-line (tractor) intervention technique. METHODS, PROCEDURES, PROCESSES The problem can be addressed in several ways:–Revise the well trajectory plan to have the ESP tangent section with a lower deviation close to the reservoir so it can be accessed by standard intervention methods.–Run new tools, such as dissolvable balls or plugs to create a temporary pressure barrier.–Access the deviated section via coiled tubing.–Access the deviated section via robotic intervention tools on e-line (Tractor). All these methods will be reviewed in this paper with an economic and operational comparison based on experiences from various oil fields. RESULTS, OBSERVATIONS, CONCLUSIONS All the methods stated above have implications not only in drilling and completion processes, but further into the life of the well. For example, drilling the well with greater deviation leads to an increase in complexity of the drilling process, where higher dogleg severity is required to land the well, and moreover, creates additional challenges to deploy the openhole completion and to achieve the well objectives. Additionally, ESP placement requires a 200 ft tangent section, which will increase the short radius trajectory complexity. The use of dissolvable plugs and balls often adds uncertainty to the timing of a completion process, where any delay in procedures can lead to loss of the barrier; and additional safety factors related to dissolution timing may otherwise lead to preventable non-productive time. Coiled tubing is a robust solution, but it is less mobile and swift in comparison to robotic intervention solutions together with nippleless high expansion plugs. The combined use of a self-anchoring stroker tool with a conveyance tractor enables a toolstring to reach highly deviated sections of the well, offering great flexibility in well design and efficiency during completion the stage, which is attractive economically. The stroker tool offers large push and pull force available in-situ resulting in effective plug retrieval and contingency options. NOVEL/ADDITIVE INFORMATION The paper provides an overview and comparison (operational and economic, with attention to long-term effect) of possible solutions to oilfield challenges as stated above and describes how it has in practice been resolved practically. It should be of interest to a wide range of drilling and workover engineering professionals.
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