The Performance Evaluation of Potassium Drilling Fluid System

The basic prescription of the potassium sulfate drilling fluid is: 5% bentonite+0.4%Na2CO3+5.0%K2SO4+1000ppmDCL+200ppmDesco+100ppmAlcome+500ppmSAP+1000ppmLT+1000ppmKEL. The content of K+ is 50000mg/L. The drilling fluid has appropriate viscosity, gel and filter loss. The shale rolling recovery rate is bigger than 85%. The static swelling rate is smaller than 2%. The corn damage is less than 20%. The mechanism of protect formation is the K+ ability of preventing the clay from hydrating and swelling, the adsorption ability of formation protecting agent and the cooperating role of K+ and formation protecting agent. The potassium sulfate drilling fluid was used in fang-3 outer section of the Song-fang-tun oilfield. It was shown that the drilling fluid could meet the drilling demand in this oilfield.