页岩油钻井漏失机理及防漏堵漏技术

针对页岩油钻井过程中漏失频发的问题，以济阳坳陷页岩油开发为例，分析了页岩油钻井油基钻井液的漏失机理。分析发现，页岩油藏天然断裂系统发育，容易发生漏失；页岩脆性强，表面油润湿，长水平段压耗大，易产生诱导裂缝漏失；油基钻井液使堵漏材料摩擦系数降低，防漏堵漏难度大。基于页岩油油基钻井液的漏失机理，对弹性孔网材料进行了表面改性处理，优选了填充材料，研制了一袋式堵漏剂，并开展了室内长裂缝封堵评价实验和现场试验。结果表明，研制的一袋式堵漏剂封堵效果好，2 mm×1 mm长裂缝承压强度达10 MPa，现场堵漏一次成功，较好地解决了页岩油油基钻井液漏失难题，为保障页岩油藏的优质快速钻井提供了技术支持。 

Mechanisms of Lost Circulation and Technologies for Mud Loss Prevention and Control in Shale Oil Drilling

Mechanisms of loss of oil based drilling fluids were analyzed taking the shale oil development in the Jiyang Depression as an example to solve the frequent occurrence of mud losses in shale oil development. The analytical results have shown that natural fractures are highly developed in shale oil reservoir formations, and this is one reason why the mud is easy to lose in shale oil drilling. The shales drilled are very brittle, and their surfaces are oil wet, pressure losses in long horizontal sections are therefore high, resulting in induced fractures into which the mud is lost. Lost circulation materials (LCM) in oil based drilling fluids have low friction coefficients, making it difficult to control the mud losses. Based on the studies on the mechanisms of mud losses occurred in shale oil drilling, a one-bag lost circulation material made from a surface-modified elastic mesh material and an optimized filling material. Laboratory long-fracture sealing and plugging experiment and field application have shown that the one-bag LCM has good sealing and plugging capacity; fractures of 2 mm × 1 mm has pressure bearing capacity of 10 MPa after being plugged with the LCM. Mud losses in field operations were brought under control in the first try of the LCM. The application of the one-bag LCM helped solve the losses of oil based drilling fluids in shale oil drilling, providing a technical support to the safe and fast drilling in shale oil reservoirs.