塔里木盆地深部煤层失稳机理及防塌钻井液技术

针对塔里木盆地深部煤层钻井过程中钻井液漏失和井壁垮塌等井下复杂问题，采用镜质体反射率分析、X射线衍射、扫描电镜等方法测试了煤的微观结构和理化性能。明确了煤层的失稳机理:煤中固定碳质量分数平均超过60%，镜质体反射率大于1.0%，煤化程度高、性脆、易破碎；黏土矿物总的体积分数低于25%，黏土中不含强水敏性矿物蒙脱石；煤层割理呈网状分布，其宽度主要集中在1~10 μm，易漏失。综合判定煤层失稳类型为力学失稳。以煤层微观结构为目标，结合钻井液材料粒度分布，优选沥青类封堵剂，设计出适用于煤层的沥青质聚磺防塌钻井液体系，其性能测试结果表明:沥青质聚磺防塌钻井液滤失量低、泥饼薄，能有效封堵煤的绝大部分割理，减少钻井液侵入量，防止煤层垮塌。研究成果一定程度上为塔里木盆地深部煤层的安全高效钻井提供技术保障。 

Instability mechanism and anti-sloughing drilling fluid technique for deep coal seam of Tarim basin

In view of the complicated problems of drilling fluid leakage and hole collapse during the drilling of deep coalbed in Tarim basin, the microstructure and physical and chemical properties of coal were tested by vitrinite reflectance analysis, X ray diffraction and scanning electron microscope, and the mechanism of coal seam instability was confirmed. The fixed carbon content of the coal exceeds 60%, the vitrinite reflectance is greater than 1.1%, and coal have high degree of coalification, is brittle and easy to break. The total amount of clay mineral is less than 25%, and there is no strong water-sensitive mineral montmorillonite in clay. The cleat of coal is reticulated, whose width is mainly concentrated in 1-10 μm, easy to leak off. The instability type of coal and rocks was judged comprehensively as mechanical instability. Taking the microstructure of coal as the object and combining with the size distribution of drilling fluid materials, the asphaltic blocking agent was optimized and the asphaltic polysulfonate anti-collapse drilling fluid for coal seam was designed. Its performance test shows that the asphaltic polysulfonate anti-collapse drilling fluid has low filtration loss and thin mud cake, can effectively block most of coal cleats, reduce drilling fluid invasion, and prevent coal seam collapse. The research results can provide technical support for safe and efficient drilling in the deep coal seam in Tarim basin.