Main pump start-up pressure limitation control system when using thixotropic drilling fluids

Abstract

Everyday drilling operations in the Norwegian Continental Shelf become more challenged. They include drilling of highly inclined long wells in depleted reservoirs within narrow geo-pressure margins. In addition, drilling in unstable formations can cause serious problems which can increase non-productive time. In order to solve these problems there is a need to develop an automated mud-pump management system with purpose to minimize the possibility of formation fracturing during start-up of the mud pump or fluid circulation. Thixotropic drilling fluids enhance a hole cleaning in a wellbore during connections, avoiding cutting settings and packoffs. On the other hand, they bring challenges when starting the mud pump. Pressure peaks are typically seen when starting the pump manually after a connection. The theoretical results found in this thesis where pressure peaks are significantly reduced during pump start-ups, indicate that automations of pump start-up should be implemented in real rig operation at the field in the near future.