关键词: 塔里木盆地, 依奇克里克区块, 煤层, 坍塌机理, 井壁稳定性, 钻井液, 钻井技术

Abstract: The complicated formation in Yiqikelike area of Tarim Basin contains mudstone,sandstone and coalbed.The instability of borehole wall during drilling mainly occurred in coalbed of the Jurassic and Triassic systems.The synthetic sloughing mechanism of coalbed in the Jurassic and Triassic systems was studied by chemical analysis and mechanical methods.The test results show that the coal samples have the properties of more hydrophilic groups,big specific surface areas,low density and powerful moisture-absorbing.The strength of coal samples is very low and decreases greatly after the water-absorbed.The type of immersed liquids and magnitude of confining pressure have a great effect on the strength of coal.According to the sloughing mechanism,the optimum drilling technique and the optimum formulation of polyalcohol-KCl drilling fluid for coalbed were achieved.The field test in coalbed of Tarim Basin demonstrates that the borehole wall was stable,and no other complex trouble occurred during drilling by the optimum techniques and drilling fluid.

Key words: Tarim Basin Yiqikelike area coalbed sloughing mechanism borehole wall stability drilling fluid drilling technique