页岩断层摩擦滑动引发套管变形的概率

Probabilities of Shale Fault Friction and Slip on Inducing Casing Deformation

摘要:

以四川盆地长宁区块N平台为研究对象，开展页岩断层泥在高温高压条件下的剪切实验，旨在揭示页岩断层的摩擦力学特性，并结合定量风险分析（QRA）方法，评估多因素耦合作用下断层的滑动趋势。实验结果显示，页岩断层的摩擦系数介于0.50~0.75之间，且随着黏土矿物含量的增加，摩擦系数呈下降趋势，同时表现出显著的位移弱化特征。QRA结果表明，在注入流体诱发的孔隙压力扰动达到15 MPa时，与套管变形井段相交断层的滑动概率超过64%。断层滑动概率随摩擦系数降低和孔隙压力扰动增大而显著上升。因此，建议压裂施工应尽量规避黏土矿物含量高于30%的断层（对应摩擦系数<0.6），或通过控制压裂施工压力（孔隙压力扰动<10 MPa）降低断层滑动风险，从而有效预防套管变形。

Abstract:

Taking the N Pad in the Changning Block as a case study， friction experiments were conducted on shale fault gouges to investigate the frictional behavior of shale faults， followed by quantitative risk assessment （QRA） to evaluate the potential for fault slip. The experimental results indicate that friction coefficients of shale faults range from 0.50 to 0.75. The friction coefficient decreases with the increase of clay content and exhibits a progressive weakening trend with shear displacement. QRA results reveal that under a pore pressure perturbation of 15 MPa induced by hydraulic fracturing， the minimum fault slip probability reaches 64%. The fault slip probability increases significantly with the decrease of friction coefficient and the increase of pore pressure perturbation. To mitigate the risk of casing deformation， hydraulic fracturing operations should avoid faults with clay content exceeding 30% （friction coefficient<0.6） or maintain the injection pressure such that the pore pressure perturbation remains below 10 MPa， thereby reducing the likelihood of fault slippage.