High Performance Water Base Drilling Fluid for Shale Gas Drilling

High performance drilling fluids used in conventional drilling are not able to satisfy the needs for long horizontal section shale gas drilling, and the use of oil base drilling fluids, on the other have, always means high cost and pollution to environment. A high performance shale inhibitor (dark brown liquid), a particles of nano/micro meter in diameter, a filming filter loss reducer, and a lubricant have been developed to formulate a high performance water base drilling fluid. The evaluation of this fluid has rheology, filtration control, lubricity and inhibitive capacity that are comparable to those of oil base drilling fluid, meaning that this drilling fluid is suitable for shale gas drilling. A drilling fluid of 2.05 g/cm³ has its friction coefficient reduced by 26% after treatment with the lubricant. This drilling fluid can form a thin layer of film around the surface in contact with it, thereby sealing off the micro-fractures and cutting of the channels through which pressure are transmitting. Shale cores rinsed for 10 h in this drilling fluid still retains high strength, meaning that this fluid has good inhibitive capacity. This drilling fluid has been used in the drilling of the Well YS108H4-2 in Huangjinping, Zhaotong, and the drilling operation encountered no downhole troubles and difficulties, and the wireline logging is successful. No hole enlargement was found, and the ROP was 11.74 m/h.