莺琼盆地抗高温高密度水基钻井液

莺琼盆地地温梯度高，压力系数大，安全密度窗口窄，抗高温高密度钻井液技术是其高温高压地层钻井面临的主要技术难题之一。对该区块现用水基钻井液进行性能分析，通过对钻井液性能进行优化，构建了莺琼盆地高温高压段水基钻井液。该钻井液体系在200℃热滚16 h后的黏度为39 mPa·s，动切力为7 Pa，高温高压（200℃、3 MPa）沉降因子为0.512，高温高压滤失量为8.6 mL，高温高压砂床滤失量为14.4 mL，在4 MPa被CO₂污染后黏度为43 mPa·s，动切力为9 Pa，API滤失量为4.5 mL，高温高压滤失量为13.6 mL。研究结果表明，该体系的流变性、沉降稳定性、高温高压滤失性、封堵性及抗酸性气体CO₂污染性能均优于莺琼盆地现有高温高压段水基钻井液体系。 

High Temperature High Density Drilling Fluid Technology for Drilling in Ying-Qiong Basin

Formations in the Ying-Qiong Basin have high temperature gradient, high pressure coefficient and narrow safe drilling window. High temperature and high mud density are two key factors for drilling in this HTHP environment. A drilling fluid formulation suitable for drilling the HTHP formations has been developed recently based on the analyses and optimization of the performance of the water base drilling fluids in use. This drilling fluid, after hot rolling at 200℃ for 16 h, has viscosity of 39 mPa·s, yield point of 7 Pa, HTHP (200℃, 3 MPa) settlement factor of 0.512, HTHP filter loss of 8.6 mL, HTHP filter loss through sand bed of 14.4 mL. After contamination with 4 MPa of CO2, the properties of the mud are as follows:viscosity of 43 mPa·s, yield point of 9 MPa, API filter loss of 4.5 mL, HTHP filter loss of 13.6 mL. Laboratory study shows that the properties of this mud, such as rheology, settlement stability, HTHP filtration property, plugging capacity and resistance to acid gas (CO2) contamination are all better than those of the drilling fluids presently in use.