鄂北低渗致密砂岩应力敏感性实验研究

分别按部颁标准和定内压变外压开展了鄂北低渗致密气田储层砂岩渗透率应力敏感性实验,并对其进行了应力敏感性评价.定围压变内压实验包含三个循环,每个循环是在孔隙流体压力不变或降低和增加围压下完成的.根据部颁标准测定的实验结果表明,渗透率随有效应力的变化幅度较大;由定内压变外压的实验结果表明,孔隙流体压力影响渗透率随围压的变化关系,内压较大时渗透率随围压的变化幅度很大.采用了4种方法对来自鄂北气田的岩样进行应力敏感性评价,四种评价方法得到的结果各不相同.部颁标准得到的敏感性最强,为极强应力敏感;基于本体有效应力评价方法得到的敏感性最弱,为弱应力敏感;基于Terzaghi有效应力和模拟地层条件的评价方法得到的结果都属于强应力敏感.与其他三种评价方法相比,模拟地层条件的评价方法是符合实际生产过程的,因此更具有参考价值.

LABORATORY STUDY ON THE STRESS SENSITIVITY IN EB TIGHT SANDSTONE ROCK

Laboratory study on the stress sensitivity for lowpermeability tight sandstone reservoir in the EB gas field has been completed with two designs,which included the Ministry Standard and the modified factorial design,and the stress - sensitivity eval-uation of tight sandstone has also been carried out.The modified factorial design contained three cycles and each cycle was run at constant pore pressure through decreasing and increasing confining stress.The results from the Ministry Standard showed permeability varied with effective stress and the relationship between permeabil-ity and the effective stress was power relation.The results form the modified factorial design indicated that pore pressure influences the relationship between permeability and confining pressure and when high pore stress,the changes of the permeability with confi-ning stress was very severe.In this paper,the stress - sensitivity evaluation was carried out by four methods,and the evaluation re-sults were different from each other.The method based on the Ministry Standard reveals the stress sensitivity is ultra - strong,but the stress sensitivity is weak by the method based on the body ef-fective stress,the sensitivity is strong by the other two methods on the base of the Terzaghi effective stress and simulating reservoir conditions respectively.However,compared with the other three methods,the method based on simulating reservoir conditions is consistent with the practical development process of gas field.