库车北部构造侏罗系煤层井壁稳定对策研究

为解决塔里木盆地库车北部构造带侏罗系煤系地层井段井壁稳定问题,采用X射线衍射、扫描电镜等方法对煤岩理化性能和微观结构进行分析,明确了煤系地层井壁失稳机理;建立考虑多割理面影响的煤层井段坍塌压力模型,评价了煤系地层地质力学参数和井壁稳定性,并优化了煤系层段井眼轨迹;根据煤岩微观结构特征,开展了钻井液封堵材料优选,形成煤层段水平井井壁稳定对策。结果表明,煤系地层主要为力学失稳,推荐煤层沿最大主应力方位、井斜45°～80°钻井,钻井液密度1.70～1.74 g/cm³,钻井液封堵复配体系为3%磺化沥青+3%乳化沥青+3%超细钙;应用发现煤系层段定向钻井无复杂事故,煤层斜井段井壁稳定防治效果好。研究成果对塔里木盆地库车北部构造带侏罗系油气安全高效开发具有重要指导作用。

A Study on Stabilization Strategy of Jurassic Coal Strata in Northern Kuche Structural Belt

This research aims to solve the problem of the poor wellbore stability in Jurassic coal strata in the northern Kuche structural belt of Tarim Basin. The microstructure and physical and chemical properties of coal samples were analyzed by means of X-ray diffraction and scanning electron microscopy, and the mechanism of coal seam instability was determined. Then the prediction model of coal seam collapse pressure considering the influence of multiple cleat surfaces is established. According to the model, the geomechanical parameters of coal and wellbore stability are evaluated and the horizontal well trajectory optimization is carried out. Meanwhile, based on the microstructure of coal, the optimization of drilling fluid blocking material is carried out to form the stabilization strategy of horizontal wall in coal seam. The results show that the Jurassic coal strata in the northern Kuche structural belt are unstable. The well inclination and drilling fluid density are 45°～80ånd 1.70～1.74 g/cm³, the blocking material system of the horizontal well borehole stabilization strategy is 3% sulfonated asphalt+3% emulsified asphalt+3% calcium carbonate. The research is instructive for the safe and development of petroleun of the Jurassic coal seam in the northern kuche structural belt of Tarim Basin.