The Application of Strongly Flocculent Drilling Fluid in Sulige Gas Field

As the environment protection requirements are becoming more stringent, mud pits for surface circulation of drilling fluid will be completely replaced by mud tanks with which the drilling fluid is circulated at the surface. To clean the mud effectively and efficiently with mud tank circulation, and maintain good drilling fluid properties to ensure safe drilling, a strong flocculent for fast flocculation used in Sulige gas field has been developed, and the formulation of a drilling fluid containing the flocculent is determined. In laboratory experiments, the formulated drilling fluid can effectively flocculate a 100 kg/m³ bentonite slurry in 20 s, finally separating the solids with the liquid. This drilling fluid was tried in the well S47-8-66H2. The length of the well using this drilling fluid is 1800 m, and the average ROP is 27.42 m/h. Compared with the average ROP, 23.00 m/h, obtained in drilling the vertical sections of horizontal wells in Sulige in 2014, an increase in average ROP of 19.22% has been realized. This drilling fluid can be well cleaned through surface tank circulation, providing successful experiences for environment protection through "no drilled cuttings on the ground" at the drilling site in Sulige gas field.