Casing damage caused by shear stress has been detected in several areas of the Daqing oilfield. Such damage can be caused by marker bed slip in mud shale sections. However, the mechanism of slippage stress in mud shale horizontal sections is currently not well understood. Based on the effect of differences in interregional pore pressure, we have established a mechanical model of a cracked horizontal plane and obtained analytical solutions for the formation stress and displacement. In order to quantitatively characterize the relative slip distance in a horizontal section, the fault stick-slip and sliding weakening theories have been used. In this paper, based on a stick-slip theory, we propose a model to calculate the slip of a mud shale horizontal section under differing interregional pore pressures. The results show, that under the influence of differing formation pore pressure between the regions, the upper layer of the horizontal section intermittently slips towards the high-pressure center. When the pore water enters the formation, the friction between the sections decreases, causing a decrease in the weakened slip phenomenon. Consequently, the slippage of the formation section will increase under the conditions. The results of the study can provide useful background for preventing casing failures in mud shale marker beds.

大庆油田多个地区已检测到由剪应力引起的套管损坏。这种损坏可能是由泥页岩部分的标记床滑移造成的。然而，泥页岩水平剖面的滑移应力机制目前还不是很清楚。基于区域间孔隙压力差异的影响，我们建立了裂缝水平面的力学模型，并获得了地层应力和位移的解析解。为了定量表征水平截面的相对滑动距离，使用了断层粘滑和滑动减弱理论。在本文中，基于粘滑理论，我们提出了一种计算不同区域间孔隙压力下泥页岩水平截面滑移的模型。结果显示，在区域间地层孔隙压力不同的影响下，水平段上层间歇性地向高压中心滑动。当孔隙水进入地层时，各段之间的摩擦力减小，从而减弱滑移现象。因此，在该条件下地层段的滑移量将增加。研究结果可为防止泥页岩标记层中的套管失效提供有用的背景。条件下地层滑移量会增加。研究结果可为防止泥页岩标记层中的套管失效提供有用的背景。条件下地层滑移量会增加。研究结果可为防止泥页岩标记层中的套管失效提供有用的背景。