Drilling practice of marine shale gas in Permian Wujiaping Formation in Hongxing area of eastern Sichuan

Permian Wujiaping Formation in Hongxing area of eastern Sichuan is rich in high-quality shale, and multiple wells have achieved high productivity of industrial gas. It is an important replacement block for the natural gas production capacity of the Jianghan Oilfield. However, due to the complex structure and lithology, deep burial depth of the target layer, and large fluctuations in the attitude of thin reservoirs, complex situations such as well leakage and collapse occuring frequently, low mechanical drilling speed, long drilling cycles, and difficulty in ensuring the drilling rate of high-quality reservoirs seriously restrict the benefit development. Based on the summary of previous data, the drilling difficulties were analyzed, the optimal design of drilling engineering was carried out, and some key rock breaking tools were selected to optimize the density and sealing performance of drilling fluid. The "three opening" wellbore structure with three different diameters, "irregular tooth PDC and mixed drill bits + high torque equal wall thickness screw + reinforced parameter drilling", simple pressure control by a rotary control head, and low density and strong sealing drilling fluid technology for "both leakage and collapse treatment" were formed. We have established a geological engineering integrated guidance technology based on "vertical depth prediction, segmented slope control, and five charts and one table", and proposed the direction for further improvement. The on-site application shows that: (1) the "three opening" wellbore structure with three different diameters meets the safety drilling requirements in Hongxing area, laying the foundation for drilling speed increase. The parameter drilling was enhanced by high-performance PDC, and the mechanical drilling speed of each opening is significantly improved. The drilling speed of the third opening section in the Permian formation increased by 15%, and the horizontal section increased by 22%; (2) The density reduction and nano sealing drilling fluid technology effectively reduced the number and time of complex treatments, and the time for complex treatments was reduced by 20.5% compared to the early implementation of wells; (3) The penetration rate of high-quality reservoirs significantly increased to 93.27%, an increase of 19.85% compared to the previous period.