顺北油田破碎地层井壁稳定钻井液技术

针对顺北油田多口井钻遇破碎地层时发生坍塌掉块、阻卡频繁的技术难题，开展了地质研究、钻井液对策和室内优化研究及现场应用。研究发现，破碎地层岩性为非黏土矿物，钻井液或滤液侵蚀后使自发育孔缝网易增压连通，使层理界面黏合力降低，单元变得松散，进而诱发大规模剥落掉块和坍塌卡钻等。在岩性组成无黏土矿物但应力集中且地层破碎的基础上，实现亚微米-微米级（0.1～100 μm）全面有效封堵，遏制钻井液或滤液侵入井周地层孔缝，保证钻井液具有高效携岩性，是破碎地层钻井液稳定井壁的关键。以原四开抗高温聚磺钻井液为基础，进行室内配方优化，研发了适合破碎地层的井壁稳定钻井液。四开应用全程未出现掉块阻卡等钻井事故，安全顺利钻达设计井深8014 m，创该区块储层段钻时最短记录。顺北Y井现场应用表明，井壁稳定钻井液性能优异，可防止破碎地层坍塌失稳，推广意义重大。 

Study and Application of Drilling Fluid Technology for Stabilizing Fractured Formations in Shunbei Oilfield

Geological study, drilling fluid measure and optimization study and field application of the research results were conducted to resolve the problems such as wellbore instability, pipe sticking and drags encountered in drilling the fractured formations in several wells in Shunbei oilfield. It was found in the studies that the lithology of the fractured formations was non-clay minerals, and invasion of the mud filtrates into the fractured formations makes the in-situ pore- and fissure-network communicated with each other and produce induced pressure inside the pores and fissures, reducing the cementation strength between bedding plains. The formations with mud filtrate invasion are thus becoming loosened, hence resulting in large-scale caving, sloughing and even pipe sticking. To drill this non-clay fractured formations with stress concentration, effective plugging of the formations with submicron-micron (0.1-100 μm) sized particles to contain the invasion of mud and/or mud filtrates into the formations is necessary, and the drilling fluid should also have good cuttings carrying capacity. Laboratory optimization of the drilling fluid previously used to drill the fourth interval of the well gave birth to a drilling fluid suitable for drilling the fractured formations. In the whole process of drilling the fourth interval, no sloughing or caving, drag and over-pull have ever happened, and the well was successfully drilled to the designed depth of 8014 m in a record-setting short time of reservoir drilling in this area. Filed application of the optimized drilling fluid on the well Shunbei-Y showed that the borehole wall stabilizing drilling fluid had excellent properties. It can be used to stabilize the fractured formation during drilling, and is worth popularizing.