中文摘要：

塔里木油田塔中地区碳酸盐岩奥陶系储层地质条件复杂，储层裂缝发育，裂缝开度为20～400μm的小裂缝和徽裂缝所占比例在50％左右，钻井过程中井漏溢流频发，气侵现象严重，增加了井控风险。由于地层微裂缝兮布复杂．n温度高（180℃），导致架桥粒子、充填粒子级配难度大，钻井液封堵效果不理想，而采用常规钻井液封堵评价方法在模拟裂缝形态和效果评价方面与现场实际存在着较大的差距。为此，提出了有针对性地封缝堵气评价方法：利用天然/人造岩心制作出微裂缝岩心模型，微裂缝开度介于20～400μm之间，缝面粗糙度与天然裂缝接近；自主设计了封缝堵气实畦计价装置，建立了微米级裂缝的封缝堵气评价方法。室内初步优选出抗高温的颗粒、纤维、可变形材料等纳微米封堵材料，并形成封堵配方，封堵配方与聚磺钻井液体糸、ENVIROTHERMNT体系配伍性好，且酸溶率高于70％，不易污染储层。

英文摘要：

The Ordovician carbonate rock reservoirs drilled in Tazhong area （Tarim Basin） have complex geology and developed fractures, 50% of which with widths between 20 gm and 400 μm. These fractures have led to frequent lost circulation, well kick and severe gas cut, which in turn resulted in well control risks. Complex distribution of fractures and high formation temperatures （180 ℃） make bridging with sized particles less effective in controlling mud losses. In laboratory experiment, commonly used testing methods for evaluating the performance of plugging drilling fluids are unable to effectively simulate the real fractures, and hence there is a big discrepancy between the laboratory evaluation and practical performanceof the plugging agents. To solve this problem, a new method has been presented based on the idea of plugging micro-fractures to prevent gas-cut. In this method, natural/artificial cores are used to make test cores with fractures of 20 μm-400 μm in width and roughness that is closely simulating the fractures encountered in the reservoirs drilled. Included in the new method are a device used to evaluate the performance of a drilling fluid in plugging micron fractures, and an evaluation procedure. With this method, particle, fiber and deformable LCMs sized in microns and nanometers were selected and an LCM formulation compatible with polymer sulfonate drilling fluid and ENVIROTHERM NT drilling fluid developed. This plugging PCM formulation, having acid solubility of greater than 70%,does not render contamination to reservoir.