Geosteering Drilling Techniques of Horizontal Sidetracking Well JA, Southeast Sichuan

Geosteering drilling through shale formations at Jiaoshiba and outside in Southeast Sichuan are characterized by technical difficulties such as the obvious contradiction and poor correlation between logging and seismic data, poor representativeness of cuttings, and larger deviation between geological designs and drilled formations. To solve these technical difficulties, pre-drilling geosteering models were first established based on seismic data and offset well data to predict the formations to be drilled. At the geosteering stage prior to entering the target, MWD and mud logging data were used for in-depth comparison of the formations, and subsequent modification the geosteering model and adjustment of the target depth to ensure safe and efficient landing of the horizontal well. At the geosteering stage for the horizontal section, MWD, gas logging, drilling time, lithology and other data were employed to accurately determine the position of the bit and correct the geosteering model in real-time to keep the bit in the target zone all the time, which is applicable to the geosteering drilling technology of horizontal shale wells in the area. The technology was applied to the horizontal sidetracking Well JA outside Jiaoshiba. The rate of drilling through gas formations for Well JA was 100% and the high quality rate of gas formation drilling was 85.5%, which showed a good application effect. The application results showed that the geosteering drilling technology is suitable for horizontal shale drilling in Southeast Sichuan. It could effectively improve the rate of gas formation drilling and could be also taken as a reference for geosteering drilling in other similar shale gas blocks in China.