Leakage Prevention and Plugging Technology for Qaidam Basin Ganchaigou Shale Oil E32 Formation

The reasons of salt rock development, high reservoir pressure, narrow density window and formation fracture development in the E32 formation of the Ganchaigou Shale Oil Qaidam Basin lead to frequent occurrence of induced fracture type leakage, resulting in long drilling cycle and low exploration and development efficiency, to solve the problem. In this paper, by deepening the understanding of formation pressure, phased optimization of the wellbore structure, testing a new consolidation and plugging technology, the application of fine pressure control technology and other measures. The results show that: (1) the four pressure profiles in ganchaigou area are established, the necessary sealing points and risk points of formation are defined, (2) the wellbore structure is optimized in three stages, and finally the conventional three-open wellbore structure is adopted, the annulus pressure loss is obviously reduced; (3) forming the consolidation and Plugging technology, the acid solubility of plugging reaches 66.87%, the system loses all in less than 15 s, rapidly forming the sealing layer, and the pressure bearing capacity of the plugging system reaches more than 15.1 Mpa, it can effectively block up the fracture channel below 7 mm, completely meet the requirements of E32 formation for plugging lost circulation, 4 well applications, 100% success rate of once plugging lost circulation, 1.5–3.2 Mpa increase of formation pressure bearing capacity, (4) application of precision pressure control drilling, reasonable control of ECD in the bottom hole can effectively reduce the complexity of lost circulation in narrow density window of E32. Three wells were used in the field, the ECD in the bottom hole was controlled within 2.30 g/cm3, and the lost circulation was greatly reduced, loss volume and loss time of single well decreased by 64% and 73% respectively. Finally, the leak-proof and leak-plugging technology for E32 fractured formation in Ganchaigou block was formed, which solved the field technical problems and made a great contribution to the rapid increase and stable production of Ganchaigou block.