Research on the Drilling Fluid Technology for High Temperature over 240oC

The hole depth of China continental scientific drilling project will be over ten thousand meters, and the bottom-hole temperature can approach 300oC. The performance of drilling fluid would be seriously damaged by the high temperature and high pressure (HTHP) downhole environment, then affect the stability of hole's wall, the rock cuttings transporting, well-construction safety and cost, etc. Based on the laboratory results of additives selection, a new kind of ultra-HTHP drilling fluid formula containing high temperature resistant fluid loss agent DDP and assorted viscosity adjusting agent DESCO is achieved: 4% Sodium bentonite + 2% HPS + 4% SMP-I + 4% JSSJ + 4% SPNH + 4% JSJ-1 + 4% LQT + 1% JNJ + 1% GBJ + 0.5% DDP. Laboratory experiments shows that: the formula has good high temperature stability and rheology at a temperature of 240 oC, HTHP water loss is low.