乌鲁木齐矿区大倾角地层煤层气钻井井壁稳定性研究

Study on Wall Stability of CBM Borehole in Large Dip Strata in the Urumqi Mining Area

准南煤田乌鲁木齐矿区是新疆煤层气勘探开发的有利区,地层倾角大,地质构造复杂,井壁稳定性是钻井工程首先需要解决的一个难题。井壁的张性破裂(井漏)和剪切垮塌是钻井过程中经常遇到的井壁稳定性问题,严重影钻井的速度、质量与成本,同时井壁稳定性也是决定套管层次的重要因素之一。可根据不同情况,优选钻井液体系与安全密度窗口,保障井壁稳定性。

The Urumqi Mining Area in Zhunnan Coalfield is a favorable area for CBM exploration and development in Xinjiang. The Area is featured with large stratigraphic dip and complex geological structure, and the wall stability of the boreholes is a difficult problem needed to be solved first for drilling engineering. The tensile fracture(circulation) and shear collapse of the wall are the problems of wall stability which often encounter in the process of borehole drilling and have severely influence on the drilling speed, quality and cost. The wall stability is also one of the important factors to determine the casing levels. According to different situations, the selection of drilling fluid system and safety density window can be optimized to guarantee the wall stability y of boreholes.