唐巨鹏,齐桐,路江伟
TANG Jupeng,QI Tong,LU Jiangwei

• 1:辽宁工程技术大学力学与工程学院

摘要(Abstract)：

页岩气吸附膨胀作用和滤失附加应力是影响煤系页岩储层水力压裂后水平井应力分布重要因素,不可忽略。考虑页岩气吸附膨胀作用和滤失附加应力,基于各向异性材料理论,建立了煤系页岩横观各向同性储层水平井井壁应力模型,分析了煤系页岩储层水平井井壁应力分布特征,考察了井筒方位角对井壁周向应力分布影响,得到了有效应力、地应力和各向异性程度对井壁起裂压力的影响规律。研究表明:井壁周向应力近似椭圆形分布,拉应力与压应力同时存在,拉应力区有效应力对井壁周向应力影响较大,方位角为90°和270°时最大,30°、150°、210°和330°时无明显影响,有效应力作用下最大井壁周向应力随井筒方位角增大近似线性增加,增加程度先降后增;吸附膨胀作用使井壁起裂压力降低,不利于井壁稳定性,高孔隙压力下吸附膨胀作用对井壁起裂压力影响更为明显;起裂压力随各向异性系数增大而减小,两者呈二次函数关系,各向异性系数越大,煤系页岩层理及其基质强度越低,天然裂缝越发育,越不利于井壁稳定性,井壁起裂压力随侧压系数增大而减小,两者呈线性递减关系。研究成果为煤系页岩气有效开发提供了科学参考。
Adsorption-expansion actions and filtration additional stress of the shale gas are the significant influencing factors on the horizontal well stress distribution after the hydraulic fracturing of the coal-measure shale reservoirs, so they are can not be neglected. Considering of the actions and additional stress, based on the anisotropic material theory, the horizontal well stress distribution model of the transversely isotropic reservoirs of the coal shale was established, the distribution characteristics of the horizontal well stress in the coal shale reservoirs were analyzed, the influences of the wellbore azimuth on the circumferential stress distribution were observed, the influencing laws of the effective stress, earth stress and anisotropic degree on the crack initiation pressure of the borehole were obtained. The study shows that the circumferential stress distribution of the wellbore is the approximate elliptical distribution, and both the tensile stress and the compressive stress coexist, the influence of the effective stress on the wall circumferential stress is greater in the tensile stress zone, when the azimuth angle is 90° and 270°, the influences are greatest, while the azimuth angles are 30°, 150°, 210° and 330°, the influences are none. The maximal circumferential stress of the well wall increases approximately and linearly with the increase of the well wall azimuth under the action of the effective stress, and the degree of the increase decreases first and then increases;the wellbore crack initiation pressure will decrease under the adsorption and expansion, which is not conducive to the wellbore stability, under the high pore pressure, the effects of the adsorption and expansion actions are more obvious on the wellbore crack initiation pressure; the crack initiation pressure will decreases with the increase of the anisotropy coefficient, the relationship between the two factors stated above is quadratic function, the bigger the anisotropy coefficient is, the lower the strengths of the coal shale bedding and its matrix will be, the more well-developed the natural fractures are, the more disadvantageous to the wellbore stability, the crack initiation pressure decreases with the increase of the lateral pressure coefficient, and there is a linear decrease between them. The study achievements can provide the scientific references for the effective development of the coal shale gas.

关键词(KeyWords)： 吸附膨胀作用;有效应力;横观各向同性;井壁稳定性;水平井
adsorption-expansion action;effective stress;transverse isotropy;wellbore stability;horizontal well

Abstract:

Keywords:

基金项目(Foundation): 国家重点研发计划“煤矿深井建设与提升基础理论及关键技术”(2016YFC0600901);; 国家自然科学基金项目“煤系页岩瓦斯吸附解吸渗流与变形耦合作用多尺度联动机制研究”(51374119)

作者(Author): 唐巨鹏,齐桐,路江伟
TANG Jupeng,QI Tong,LU Jiangwei

DOI: 10.19597/j.issn.1000-3754.201810034

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