塔里木盆地依奇克里克区块煤层钻井技术研究

塔里木盆地依奇克里克区块地层复杂,钻遇的岩性主要有泥岩、砂岩和煤层,井壁失稳主要发生在侏罗系和三叠系的煤层井段.利用化学分析和力学研究方法,探讨了侏罗系和三叠系煤层的坍塌机理和防塌钻井技术对策.实验结果表明,侏罗系和三叠系煤岩含有较多的亲水基团,煤化程度低,密度低,比表面积大,相对吸水量和比吸水量都很高;煤岩自身的强度较低,吸水后强度会进一步下降,浸泡液类型和围压对煤岩强度有很大的影响.根据煤层坍塌机理,探讨了煤层钻井的防塌技术,优选了适合于煤层的多元醇/KCl钻井液配方.现场应用表明,所确定的防塌钻井技术及多元醇/KCl钻井液能有效地防止煤岩井壁失稳和其他井下复杂情况的发生,确保了钻井安全,提高了钻井时效.

Drilling techniques for coalbed in Yiqikelike area of Tarim Basin

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.