Shiyou shiyan dizhi (May 2024)
Safety and accelerated drilling technologies for deep shale gas in Weirong of Sichuan Basin
Abstract
The Weirong shale gas in the Sichuan Basin, buried at depths of 3 600-3 850 m, represents a prototypical deep shale gas reservoir. Drilling operations face challenges such as a complex pressure system, developed fault-dissolved bodies in certain areas of the Maokou Formation, poor drillability of formations, and high strata temperatures in the Longmaxi Formation. To address these complex geological conditions, this study focused on the safe and accelerated drilling. By combining mature technologies with pilot testing, continuous efforts were made to advance drilling engineering techniques. Through deepening the understanding of the geology of the passing strata sections, targeted solutions for each section were implemented to enhance the precision of engineering techniques. The Weirong shale gas field had gone through three stages: exploration and evaluation, development phaseⅠ, and Ⅱ. This led to the development of safe drilling technologies that emphasize optimization of well structure, track designs avoiding fault-dissolved bodies, wellbore pressure control, and synchronized drilling andfracturing to prevent interference between wells. Additionally, accelerated drilling technologies were cultivated, focusing on a "2D + small 3D" three-dimensional track profile, integrated geological guidance, optimal rock-breaking tools, and enhanced drilling parameters. Applied to over 150 well drillings in the Weirong shale gas field, these technologies increased the rate of penetration from 6.32 m/h at the start of development to 9.12 m/h, reduced the drilling cycle from 106.68 days to 68.75 days (a reduction of 35.56%), achieving the goal of acce-lerated and cost-effective deep shale gas drilling in Weirong area. These technologies provide significant reference value for the development of similar gas reservoirs.
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