Abstract:
A new high performance water base drilling fluid, XZ, has been developed for use in drilling the costly deep wells in the Junggar Basin. The formulation of the drilling fluid, based on "plugging, inhibiting, solidifying, duel repellent, and lubricating" principles, was conducted with several additives, such as a bionic inhibitive agent XZ-YZJ, a bionic plugging agent XZ-FDJ, a lubricant XZ-RHJ, a solidifying filming agent XZ-CMJ and a duel repellent agent XZ-SSJ etc. This drilling fluid has good rheology and is resistant to long-term aging and to contamination. After being aged for 3 d or being contaminated with 2% CaSO4 or 10% bentonite, the mud still maintains good rheology. Swelling test with the drilling fluid on Na-bentonite cores showed that the rate of swelling of the cores was reduced by more than 95%, and roller oven test with drilled cuttings from a well site showed that cuttings recovery was greater than 95%, indicating that the drilling fluid has satisfactory inhibitive capacity. Good plugging performance, lubricity, inhibitive capacity and low surface tension of the drilling fluid are beneficial to borehole stabilization, lubricity, pipe sticking prevention and reservoir protection, rendering the drilling fluid adaptability to the drilling of deep well and deep extended-reach well which are characteristic of more downhole troubles. Field application demonstrated that the new drilling fluid is able to help in reducing downhole troubles, minimizing rate of well enlargement, and reducing time needed for well construction. The application of this drilling fluid has satisfied the needs for safe, efficient and environmentally friendly drilling operations, indicating that the drilling fluid has a bright future in finding wide applications.