Abstract: Reservoirs in well block Fudong5 are typical of highly water-sensitive channel sand bodies. The target Toutunhe Formation has a structure of sand-in-mud. With a clay mineral content as high as 27%～31% and a montmorillonite content as high as 56%～82%，the formation is highly water sensitive. Due to the strong water sensitivity，there is a high requirement for wellbore stability during drilling. Because of the high montmorillonite content，the rocks are very likely to become hydrated and swell，causing wellbore sloughing or collapse. The formation is likely to absorb water and swell，which changes the overall strength of mudstone，and causes wellbore instability. In the early stage of drilling，water-based drilling fluid was used，mudstone was very likely to swell，collapse，which caused sticking，backfilling，sidetracking and other drilling troubles many times. In this paper，the technical problem that has restricted the horizontal well drilling in the highly water-sensitive channel sand bodies in well block Fudong5 is solved by using such technogies as oil-based mud，borehole cleaning，real-time optimization and analysis of drilling parameters，and safe running of drillstring，which is of certain reference significance for accelerating the high-efficiency evaluation and massive development of water-sensitive channel. 

Key words: water-sensitivity; oil-based drilling fluid, wellbore instability, borehole cleaning, rotary steering, high-efficiency PDC bit

摘要： 阜东5井区油藏是典型的强水敏性河道砂体油藏，目的层头屯河组为“泥包砂”结构，黏土矿物含量高达27%～31%，其中蒙脱石含量高达56%～82%，为强水敏性地层。因水敏性较强，在钻井过程中对井壁稳定性要求较高，岩层蒙脱石含量高遇水易水化膨胀造成井壁剥蚀掉块或坍塌，改变泥岩整体强度，引发井壁失稳。前期应用水基钻井液，泥岩遇水易膨胀，易坍塌，卡钻，造成多次回填侧钻等钻井复杂情况。通过油基钻井液技术、井眼清洁技术、钻井参数实时优化分析技术以及管柱安全下入技术解决了制约阜东5井区强水敏性河道砂体油藏水平井钻井技术难题。对加快水敏性河道砂体油藏高效评价、规模开发具有一定借鉴意义。

关键词: 水敏性, 油基钻井液, 井壁失稳, 井眼清洁, 旋转导向, 高效PDC钻头