Key Technologies for Deep Marine Shale Gas Drilling in Southern Sichuan

Deep marine shale gas in the southern Sichuan Basin has a deep burial depth, high formation temperature and formation pressure, poor rock drillability and thin high-quality reservoirs. Further, the contradictions between fast drilling and borehole quality, shale collapse and drilling cost, time-controlled drilling and the variable probability of encountering high-quality reservoirs have hindered its effective development. To this end, based on the experience of conventional shale gas development, through the differentiated casing program and borehole trajectory design, by adopting bent-housing mud motor BHA, optimization of drilling parameters, conducting vertical drilling and gas drilling technical tests, development of high-performance water-based drilling fluid and the borehole trajectory control, a set of key drilling technologies suitable for the effective development of deep shale gas in the Southern Sichuan were formed. Those technologies were applied in 27 deep marine shale gas wells in the Southern Sichuan, resulting in the fact that the the drilling cycle was shortened by 46.0% and the rate of high-quality encountering economic reservoirs reached 93.17%. The results indicated that those key drilling technologies could sustain the effective development of deep marine shale gas in southern Sichuan, and they could provide references for the development of similar shale gas reservoirs at home and abroad.