库车坳陷克拉A气田储层裂缝走向异常成因

针对库车坳陷克拉A气田中部分井点储层裂缝的实际走向与理论走向不一致的异常现象,结合气田的地质特征,对可能造成这种异常的原因进行了探讨.分析认为,裂缝走向异常成因有应力因素及非应力因素2种可能性.岩层在弯曲变形时会派生出张应力,与区域地应力场叠加后,使主应力的方向发生改变,最终导致裂缝走向产生变化.非应力因素包括温压条件的影响和上覆盐构造的影响.处于较大埋深的地层,温度和压力值较高,同时地层中的高泥质含量和上覆盐岩层的强烈塑性流动,使目的层岩石的韧塑性增强,发生韧性变形,出现最大主应力位于共轭剪裂缝钝夹角平分线上的现象.此外,目的层处于上覆盐构造层和下伏地层的交界处,应力分布复杂,也在一定程度上影响着裂缝的走向.两种可能性都能比较合理地解释储层裂缝走向的异常,但哪种因素起决定性作用尚需进一步的验证.

Genesis of abnormal reservoir fracture strike in Kela-A Gasfield,Kuqa Depression

Genesis of abnormal reservoir fracture strike in the studied area is analyzed according to the geological characteristics of the area.It is held that there are two possible types of causes,one is stress factor,and the other is non stress factors.The overlying of the tensile stress derived by the bending deformation of rock with original regional formation stress makes the directions of principal formation stresses changed,which causes the change of formation fracture strike.Non stress factors include temperature-pressure condition and overlying salt structure.The high temperature and high pressure,the high formation clay content and the strong plastic flow of the overlying salt layer in deep formation make the plasticity of the objective reservoir strengthen and make the objective reservoir produce plastic deformation,and the state that maximum principal stress is in the angular bisector of conjugate shear fractures leads to the change of formation fracture strike.In addition,because the objective reservoir is between overlying salt layer and underlying formation,the complicated stress distribution in the reservoir may also influence reservoir fracture strike.The two types of causes can all reasonably explain the abnormality of reservoir fractures,but which is decisive needs to be verified further.