摘要
页岩储层水平方向上的层理性结构导致了页岩较强的非均质性和各向异性。基于岩石横向各向同性本构关系以及渗流与变形耦合数值方法,建立了页岩水平井裂缝起裂的三维有限元数值模型,对射孔方位角、弹性力学各向异性以及地应力各向异性对水力裂缝起裂压力的敏感性进行了研究。研究结果表明:随射孔方位角的增加,起裂压力增大,起裂压力应力分布云图呈部分"椭圆状"且倾向于最大水平主应力方向;弹性模量各向异性较大和泊松比各向异性较小时,岩石表现出在水平方向上较强的刚性特征,裂缝起裂的可能性较大;弹性模量各向异性较小和泊松比各向异性较大时,岩石表现出在垂向方向上较强的刚性特征,岩石不易起裂。研究结果可以为页岩气井裂缝起裂压力预测提供参考依据。
Horizontal bedding architectures in shale lead to strong heterogeneity and anisotropy of reservoir formations. The 3D finite- element numerical model for fracturing in horizontal wells in shale has been established on the basis of isotropic features and numerical modeling of coupling of seepage and deformation. In the course,the sensibility of perforation azimuth,elastic mechanics anisotropy and geo- stress anisotropy to fracturing pressure of hydraulic fractures is tested. The results show that fracturing pressure increases with increase of perforation azimuth,while cloud atlas for distribution of stress related to fracturing pressure are characterized by partial 'elliptical'configuration and inclined to the direction of maximum horizontal principal stress; given significant anisotropy of elastic modulus and small anisotropy of Poisson ratio,rocks may display high rigid features horizontally,which may correspond to higher possibility of fracturing; for minor elastic modulus anisotropy and significant anisotropy of Poisson ratio,rocks may display high rigid features vertically,which means less possibility of fracturing. The research results can provide necessary references for prediction of fracturing pressure in shale gas wells.
出处
《特种油气藏》
CAS
CSCD
北大核心
2014年第6期133-137,148,共5页
Special Oil & Gas Reservoirs
基金
国家自然科学基金重点项目"控压钻井测控理论及关键问题研究"(51334003)
国家自然科学基金面上项目"基于模型预测控制理论与状态机架构的控压钻井压力控制方法研究"(51374223)
中国石油科技创新基金"面向页岩气体积压裂的分簇射孔技术研究"(2012D-5006-0303)
关键词
页岩
渗流与变形耦合
弹性各向异性
射孔方位角
起裂压力
shale
coupling of seepage and deformation
elastic anisotropy
perforation azimuth
fracturing pressure
