靖边气田煤层地应力及井壁稳定研究

煤层地应力测量难度很大,煤层垮塌失稳力学机理的研究还无法深入.针对这一现状,利用含煤层系中硬岩层的地应力实测结果,以组合弹簧模型为基础,反求出构造作用引起岩层水平方向的应变量,以此来确定后续地应力有限元模拟的边界条件,将硬岩层的地应力实测、理论模型计算以及有限元数值模拟三者有机结合起来,反演得到煤层地应力状态,从而建立起一套含煤岩系等软岩层地应力研究新方法.利用该方法对靖边气田某区块LP-1井煤层井壁稳定进行了研究,结果表明:沿最小水平地应力方向钻井井壁稳定性最好,沿最大水平地应力方向钻井井壁稳定性最差,而沿最大和最小水平地应力角角平分线方向钻井井壁稳定性介于前两者之间.

Research on in-situ stresses and borehole stability of coal seam in Jingbian gas field

It is difficult to study instability mechanism of coal seam because the traditional methods are mostly questioned. In view of present situation, the strain magnitude in horizontal direction due to tectonic action has been calculated based on in-situ stress measurement in hard rocks combined with spring model. Taking the strain magnitude in horizontal direction as boundary condition for in-situ stress finite element analysis, a finite element model is set up to invert in-situ stress field of coal seam. Combining the in-situ stress measurement in hard rocks, theoretical model and finite element numerical simulation, a new method for research on in-situ stress in coal-bearing seam has been developed. The borehole stability of coal seam of well LP-1 in Jingbian gas field has been studied with the method, and the results show that the borehole stability is good when drilling along the direction of minimal horizontal in-situ stress, and it is bad when drilling along the direction of maximum horizontal in-situ stress; and the borehole stability when drilling along the bisecting lines ranged from the maximum to the minimal horizontal in-situ stresses falls in above two cases.