密度减轻剂在中国南海超深水钻井液中的应用

南海西部永乐区块某井水深1 893 m，泥线温度2.3 ℃，安全密度窗口极窄，其中目的层静态压力窗口只有0.1 g/cm3。为解决窄密度窗口水基钻井液安全钻进与水合物抑制的矛盾，在不影响钻井液流变性的情况下，利用乙烯基三甲氧基硅烷、乙烯基三乙氧基硅烷及固化剂等对玻璃微珠表面进行改性，制备了一种密度为0.4 g/cm3左右的新型密度减轻剂。室内实验结果表明，该密度减轻剂抗压能力能够达到40 MPa，对HEM钻井液体系流变性能影响小，能够有效降低钻井液密度0.4~0.6 g/cm3，室内相关钻井液性能测试与现场实测数据相吻合，现场应用结果表明该密度减轻剂有效拓宽了现场安全密度窗口，现场作业顺利并且易维护，无复杂情况出现。

Application of density reducer to the drilling fluid used in the ultra deep water of South China Sea

A certain well in the Yongle Block of western South China Sea has the water depth of 1 893 m and the mud line temperature of 2.3 ℃. Its safety density window is quite narrow, and the static pressure window of the target layer is only 0.1 g/cm3. In order to resolve the contradiction between the hydrate inhibition and the safe drilling of water-based drilling fluid in the formation with narrow density window, a new kind of density reducer was prepared by modifying the surface of glass bead by virtue of vinyl trimethoxysilane, vinyl triethoxysilane and hardener, without influencing the rheological property of drilling fluid. The laboratory experimental results show that this new kind of density reducer has the compressive strength of 40 MPa, less influences the rheological property of HEM drilling fluid system and can effectively reduce the drilling fluid density by 0.4-0.6 g/cm3. And the laboratory performance test results of the drilling fluid are in line with the field measurement data. The field application results indicate that thanks to the application of this density reducer, the field safety density window is broadened effectively, the field operation is smooth and maintained easily and no complex situations occurs.