Lost Circulation Prevention and Plugging Technologies for the Ultra-Long Horizontal Section of the Horizontal Shale Oil Well Hua H90-3 in Changqing Oilfield

Well Hua H90-3 is an ultra-long horizontal well deployed in the Longdong National Shale Oil Demonstration Area in Changqing Oilfield. Due to geological migration, the horizontal section of the well has a discontinuous reservoir with faults in it. The pores of sand bodies are well developed, and the pressure-bearing capacity of the formation is low. In addition, formation fluids are active, and the plugging fluid cannot be retained or solidified after dilution, which increases the difficulty in plugging. In view of the above technical difficulties, the equivalent circulating density (ECD) monitoring technology was applied to prevent lost circulation in advance, and the plugging while drilling technology was incorporated to improve the efficiency of plugging. Moreover, curable and water-blocking fibrous working fluids for lost circulation control were developed to achieve the one-time sealing of the thief zone in combination with the precise positioning technology, so that the key technologies of lost circulation prevention and plugging were formed for the ultra-long horizontal sections of shale oil. The on-site application of the technologies made possible the successful drilling of Well Hua H90-3, with a horizontal section length of 5 060 m, which set a new record for the longest horizontal section of onshore horizontal shale oil wells in Asia. The research showed that the technologies could provide a technical reference for the drilling of horizontal shale oil wells with ultra-long horizontal sections in China.