Plugging while Drilling Technology Using Oil-Based Drilling Fluid in Fuling Shale Gas Field

The horizontal interval in the 3rd Section drilled by using oil-based drilling fluids during the development of the Jiaoshiba Block in Fuling Shale Gas Field was susceptible to low success rates in plugging operations and the reoccurrence of lost circulation due to incompatibility of lost circulation materials (LCM) and drilling fluids.Accordingly,lost circulation systems for oil-based drilling fluids were developed.Based on working principles characterized by "Joint application of rigidity and flexibility,plugging through deformation and filling by fine particles",lab tests were conducted to select JHCarb rigid LCM,HIFlex deformation particles and H-Seal elastic plugging additives to prepare plugging while drilling systems for oil-based drilling fluids.Highly compatible with oil-based drilling fluids and with outstanding performances in oil and temperature resistance,the newly developed systems may be circulated for prolonged periods in drilling fluids to eliminate the possibility of lost circulation.With pressure-bearing capacities over 7 MPa,the system could be deployed to plug fractures with widths below 3.0 mm.The system has been deployed during drilling of the horizontal well interval for shale gas development in Jiaoshiba Block by using oil-based drilling fluids.The system was proved to be capable of effectively eliminating lost circulation with velocities around 10.0 m3/h during drilling.Research results showed the plugging while drilling system of oil-based drilling fluids could effectively enhance the pressure-bearing capacities of formations and protect shale formations from lost circulation.Eventually,the system might facilitate execution of well cementation operations.