满深1井奥陶系桑塔木组高性能防塌水基钻井液技术

满深1断裂带奥陶系桑塔木组为泥岩、泥灰岩地层，裂缝发育，井壁坍塌风险极高，给安全钻井带来了极大挑战。满深1井钻进至井深7 392.54 m（桑塔木组）时钻遇走滑断裂带，发生坍塌卡钻，处理难度大，最终选择回填侧钻。为此，分析了桑塔木组地层特点，研究应用了高性能防塌水基钻井液技术:选择合理的钻井液密度，强化对井壁的力学支撑，并采用复合降滤失措施降低水敏性泥岩地层的水化；在引入多氨基井壁抑制剂的同时，提高K+质量浓度，实现多元抑制防塌；提高钻井液的抗温能力、润滑性能及封堵性能，以满足桑塔木组对抑制、封堵防塌及抗高温稳定性的要求。现场应用表明，该井侧钻过程中钻井液性能稳定，K+质量浓度保持在35 000 mg/L左右，150 ℃温度下的高压滤失量由11.3 mL降至8.0 mL，桑塔木组钻进过程中未发生井眼失稳情况，顺利钻至三开中完井深，套管一次下到设计位置。这表明，高性能防塌水基钻井液防塌效果显著，达到了预期目标。 

High Performance Anti-Sloughing Water Based Drilling Fluid Technology for Well Manshen 1 in the Ordovician Sangtamu Formation

The lithology of Ordovician Sangtamu Formation in Manshen 1 fault zone is composed of mudstone and marl with well developed fractures and high risk of wellbore collapse, which brings great challenges to safe drilling. When Well Manshen 1 was drilled to the depth of 7 392.54 m (Sangtamu Formation), a strike slip fault zone was encountered, resulting in well collapse and sticking of drill tools, which was difficult to deal with. Backfill sidetracking was thus implemented. To solve this, the formation characteristics of Sangtamu Formation were analyzed, and the high-performance anti-sloughing water based drilling fluid technology was developed. Reasonable drilling fluid density was selected to mechanically support the borehole wall, compound fluid loss control measures were adopted to reduce the damage caused by filtrate on the water sensitive mudstone formation, and multi-amino borehole wall inhibitors was introduced while increasing K+ content to achieve a multiple anti-sloughing effect. At the same time, the temperature resistance, lubrication property and plugging performance of drilling fluid were improved to meet the requirements of inhibition, plugging, anti-sloughing and high temperature stability of the Sangtamu Formation. The application in the sidetracked borehole of the Well Manshen 1 showed that the drilling fluid performance was stable during sidetracking, the K+ content was maintained to be at around 35 000 mg/L, and the high temperature and high pressure filtration rate was reduced from 11.3 mL to 8.0 mL at 150℃. During the whole construction, no borehole instability occurred in the Sangtamu Formation. The well was successfully drilled to the total depth of the third spud, and the casing was set in place in one run. This showed that the anti-sloughing effect of high performance water based drilling fluid was remarkable, and it achieved the expected goal.