This paper introduced a numerical simulation study on disturbance of stress/ strain induced by mudstone soaking during injection and production activities in the Xingshugang area of the Daqing Anticline, Songliao Basin, China. The variations of stress and strain in different water contents of mudstone layers are researched in this paper. The relationships between formation pressure and stress and strain pre and post mudstone soaking are also investigated, so as to offer an evidence for a reasonable design of injection and production technique. Results indicate that different horizons have different stress responses to the soaking of mudstone. Besides, the different stress responses of different horizons, weakening of mechanical property of rocks due to the mudstone soaking, difference of pore pressure in a layer or between layers, difference of property and permeability between mudstone and sandstone,and reducing of effective stress as a result of high pressure injection giving rise to the concentration of shear strain along SI-SII mudstone layer. And, then it results in shearing casing damage of mudstone layers. Shear strain is rising with the increase of water contents of mudstone layers, and its shear strain rising rate is proportional to the increase of water contents. So, reducing the water injection pressure and formation pressure of reservoirs close to mudstone layers is needed to relieve shearing casing damage after mudstone soaking.