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Managing sand production has been a common problem and one of the most difficult challenges within the oil and gas industry. Various techniques are available to control sand production such as downhole sand screens. More than half of the wells in Malaysian fields are completed with downhole primary sand control or require sand management throughout their lifetime. To further aggravate the issue, most primary sand controls installed have suffered from failure after an extended period of production due to unacceptable high pressure drop in the near wellbore area which causes the screen to lose the ability to retain the formation sand particles. There are four (4) common mechanisms that can lead to the screen failure which include plugging, corrosion, erosion, and mechanical deformation. Erosion occurs when the formation particles hit the screen surface with high velocity or by continuous production through the screen openings. Operators are often compelled to rely on thru-tubing metallic sand screen to reactivate the idle wells back into production. However, most metallic sand screens suffer from sustainability issue due to excessive erosion especially for gas wells. Most operators have shifted their focus to maximize the screen lifetime against erosion, which consequently leads to the development of a novel sand screen design where an inventive coating consists of ceramic or hard metal amalgamation was applied by plasma spraying technique on the screen (i.e., outside surfaces facing the formation) to reinforce its resistance against severe erosive environment. An extensive development and verification program was conducted to select over 50 possible coating combinations, guarantee predefined slot size, assess corrosion resistance, and ascertain mechanical integrity of both the coating and screen. The technology has been considered and applied in Field A, offshore Borneo Island as remedial sand control due to its superior durability and resistance compared to metallic sand screen. Extensive technology hunting had been conducted by the operator to identify new erosion resistant thru-tubing sand screen for gas well application. As part of the overall project requirement, test facility was built by the Service Partners that consists of a flow loop testing designed to simulate accelerated erosive downhole condition with the combination of high flowrate and volume-controlled particle coalesced into an acceleration tube. The screens were tested for 60 hours at maximum velocity of 18 m/s during liquid erosion test and for 48 hours at maximum velocity of 80 m/s during gas erosion test. Rigorous analysis was conducted focusing on among others optical criteria, mass loss and sand retention tests (SRT) before and after the erosion test to verify the functionality and validate its performance prediction prior to the actual field application. Velocity calculation was also conducted using in-house and commercial software to adjudicate the design limit, to set the target gas rate for the pilot wells and establish the well unloading procedure as guidance for offshore personnel. Pilot field trials have been designed to demonstrate screen installation, risk mitigation and sustained production. Dual-pot sand filter (DPSF) and online sand sampler (OSS) was deployed as additional assurances to safeguard topside integrity, to closely monitor the sand production at surface and collect any sand grains larger than the screen slot sizing throughout the well unloading sequence. Close inspection on both erosion tests indicated no significant wear or slot size widening of the coated screen samples as compared to the uncoated screen samples that show severe erosion with slot size increases more than doubled in some places. The coated screen samples show the equivalent sand retention capabilities before and after the erosion tests, while the uncoated screen sample subjected under the same conditions lost its ability to retain sand. During field trial, the screen was successfully installed using nipples plug via slickline to revive the idle wells back to production at a lower total cost without HSE related issue and production gain beyond the initial target. Actual field results supported by the extensive laboratory testing presented herein, demonstrate the inherent benefit of plasma spray coatings ensuring mechanical integrity and durability of sand screen in highly erosive environment. Teardown analysis will be conducted to investigate the performance prediction, authenticate erosion resistance of the sand screen bottomhole assemblies (BHA) and document the findings for future improvement. |
