新型无土相油基钻井液研究与现场试验

The Development and Application of a Clay-Free Oil-Based Drilling Fluid

针对常规有土相油基钻井液因有机土及沥青降滤失剂等黏度效应较大、不利于流变性控制和低密度白油油基钻井液适用范围窄的问题,以自主研发的增黏提切剂、乳化剂和聚合物降滤失剂为基础,通室内试验考察了其配伍性并优选了其加量,形成了无土相油基钻井液。室内试验结果表明,无土相油基钻井液在油水比为70∶30~100∶0、温度为80~160℃、密度为0.9~2.2kg/L时,塑性黏度可控制在55mPa·s以内、破乳电压在450V以上,API滤失量小于2mL,抗钻屑污染达30%,抗水污染达20%,加重材料对润滑性能影响非常小。焦石坝区块4口页岩气水平井的现场试验表明,无土相油基钻井液原材料少,维护处理简单,流变性易于控制,固相含量低,具有良好的剪切稀释性,有利于降低循环压耗,提高机械钻速。

Conventional oil-based drilling fluids are characterized by their significant viscosity effects due to the content of organic clay and asphalt filtration loss controller.So it is difficult to control their rheological properties and the limited low-density oil-based drilling fluids application.Under such circumstances,a clay-free oil-based drilling fluid has been developed by using an independently developed viocosifier,strength-enhancing additives,an emulsifier and polymer filtration loss reducer.Compatibility and optimal volumes of such additives have been determined through experimental study.Research results show that the newly developed clay-free oil-based drilling fluid may have controlled plastic viscosity within55mPa·s,an emulsion-breaking voltage above 450 V,an API filtration losses less than 2 mL,cutting pollution resistance up to 30% and water pollution resistance up to 20% under oil/water ratios 70∶30to100∶0,temperature 80-160 ℃ and densities 0.9-2.2kg/L.At the same time,the impact of weighting materials on lubrication performance are negligible.The newly developed drilling fluids have been applied in four horizontal shale gas wells in Jiaoshiba Block.Test results show that the innovative clay-free oilbased drilling fluids involve minor raw materials,simplified maintenance requirement,controllable rheological properties and low solid contents.With desirable shear thinning behaviors,the drilling fluid may effectively minimize circulation pressure losses and enhance ROP.