Application of Managed Pressure Drilling in Shale Gas Wells in Southern Sichuan

The shale gas wells in Zigong, southern Sichuan have a long open-hole interval, a wide range of formation pressure system, high risk of lost circulation and well control. To deal with the formation abnormal high pressure, the high-density drilling fluid is generally used, which results in high solid content and high temperature problem during drilling, which causes frequent instrument failures and other chain reactions downhole. In view of the above difficulties, the application of managed pressure drilling was carried out in two wells on the Z205H58 platform. A targeted density reduction drilling optimization plan and supporting well control measures were formulated pertinently. During the drilling period, combined with the characteristics of formation pressure, the density of drilling fluid was reduced by 0.22g/cm 3 . Compared with the adjacent wells in the platform, the bottom hole temperature decreased by 5∼8 centigrade, the penetration rate increased by more than 80%, the daily average footage increased by 130%, and the drilling cycle was shortened by 60%, achieving the design well depth with ‘zero lost circulation, zero complexity’. Practice proves that the fine pressure control technology fully guaranteed the maximum utilization of downhole tools and technical potential, providing technical support for the efficient, low-cost and fast drilling of deep shale gas.