莺琼盆地高温高密度水基钻井液流变性调控方法

南海莺琼盆地高温高压地层钻井安全密度窗口窄，对钻井液流变性要求苛刻，而高密度钻井液因固相含量高其流变性调控难度大，因此研究高密度钻井液流变性的影响因素和调控方法对确保该地区高温高压钻井安全至关重要。本文提出通过控制钻井液处理剂液相粘度来调节水基高温高密度钻井液流变性新方法，并通过毛细管黏度法评价了莺琼盆地两套高温高压水基钻井液体系的流变性能以及液相黏度，对高密度水基钻井液流变性影响因素进行了评价和分析。结果表明，钻井液的液相黏度和固相含量是影响高密度钻井液的关键因素，钻井液体系的液相黏度由处理剂液相黏度决定，而固相含量主要由加重材料的品质决定。进一步评价结果表明，磺化类降失水剂液相黏度最低，其次为改性天然高分子降失水剂，合成类的聚合物型降失水剂液相黏度最高；钻井液在相同组成和密度条件下，重晶石品质越高，即密度越高，粒径越小，所配制的高密度钻井液流变性越优。由研究结果可得出，选择低液相黏度处理剂、低剂量膨润土和优质重晶石是高密度水基钻井液流变性调控的主要技术手段。

Research on Rheology Control Method of High-temperature and High-density Water-based Drilling Fluid in Yingqiong Basin

South China Sea is one of the three high-temperature and high-pressure offshore oil and gas regions in the world. Because of the narrow drilling fluid density window, performance requirements of drilling fluid were very strict in this area. It is difficult to adjust rheological properties of high density drilling fluid because of high solid phase content. Rheological properties of two water-based high density drilling fluids, which were used in HTHP well in Yingqiong basin, were evaluated. Influencing factors of rheological properties of high density drilling fluid were researched including liquid viscosity of additives, density and particle size of barite. Test results show that rheological properties of high density drilling fluid depend on liquid viscosity of additives and solid content, viscosity of high density drilling fluid increased with the increase of liquid viscosity of additive, meanwhile viscosity of high density drilling fluid increased with the particle size increase and density decrease of barite. It was very important to select additives having low liquid viscosity, low addition bentonite and high quality barite to maintain excellent rheological properties of high density drilling fluid.