Maximizing Slim Hole Well Deliverability: First Installation of 3.5" Alternate Path Open Hole Screen in Indonesia and Implementation of Erosional Velocity Analysis

Abstract

This paper presents the case history of a successful application of slim open hole completion as a cost-effective solution for sand control in a subsea gas well and the optimization of production by implementing erosion velocity analysis method beyond conventional erosion limitation set by API 14RP standard. Soon after production start-up, solid production and subsequent reduction in production rate were observed in subsea gas wells at "B" field through a shape memory polymer screen completion. The company thus decided to perform a workover, sidetrack the well from 9-5/8" casing and recomplete the well in 6" × 8" Open Hole using open hole gravel pack. Due to the presence of shale, the well was drilled with oil-based drill-in fluid (DIF) to ensure open hole integrity. The DIF was displaced to low-solid oil-based mud prior to running screens and later displaced to water-based once the screen was on depth prior to pumping gravel pack fluid. In order to achieve efficient fluid displacement, thorough simulation and analysis were run. For sand control strategy, open hole alternate path system was selected in combination with Visco-elastic Surfactant (VES) gravel carrier technology to allow bypassing potential sand bridges in the annulus. Extensive fluid compatibility tests were also performed in the field to avoid incompatibility during each phase of the operation. Downhole gauges were installed in drill pipe and wash pipes to allow post-job analysis and confirm packing efficiency post-gravel pack. They also enabled identification of downhole events during job execution. The result of the analysis was then used as lesson learned for subsequent well operation. After gravel pack execution in the first well, post-job downhole gauge analysis showed premature fracture occurred during gravel packing which caused some proppant to go into the fracture. Further analysis showed that the lower section of the screens could have been plugged prior to gravel-packing, which contributed to high friction during the gravel pack which led to premature fracture. Several changes were proposed for the second well. One of them was to perform open hole displacement prior to setting packer to minimize the amount of fluid going through the screens during displacement. Gel loading and proppant concentration were also optimized to promote bridging within the open hole, activating the shunt tubes. The second well was gravel packed successfully with a positive screen-out indication. Downhole gauge data analysis also showed very little indication of screen plugging compared to the first well and good packing indication across the screen annular. Due to slim hole, there was a concern regarding erosion limitation of the completion accessories if the well is to be produced as per target rate. As a solution, an in-house erosion velocity simulation analysis was proposed. This more advanced analysis was based on fluid dynamics simulation and capable of predicting erosion more accurately than conventional method based on API RP14. It predicts erosion impact based on a set of parameters known as erosion constants belonging specifically to certain material. It also takes into account profile geometry of the equipment and predicts impact angle of incoming particles resulting in more accurate results. As a result, this fluid-dynamics-based analysis shows less conservative erosional limit than the API RP14 standard and thus allows the completion components to withstand higher production rate than initially expected. The successful application of slim hole gravel pack in combination with implementation of erosion velocity analysis based on fluid dynamics demonstrates that despite limited flow area through the completion components, gas production rate can still be maximized without risking erosion to the downhole equipment. More importantly, both wells have been producing sand-free and are currently delivering at targeted production rate.