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以大庆油区杏树岗南部开发区为例,对注采过程中泥岩浸水软化引起的应力应变局部扰动进行了数值模拟研究,探讨了泥岩浸水对应力应变的扰动,以及对地层压力与应力应变关系的影响。结果表明,泥岩浸水对不同层位应力的扰动情况各不相同,造成了层间应力状态的差异。层间应力状态的差异、泥岩层浸水后自身力学性质的弱化、注采引起的层内及层间孔隙流体压差、泥岩层与砂岩层之间渗透率和岩性的差异以及高压注水引起的有效应力降低等因素综合作用,导致萨尔图油层组的萨Ⅰ—萨Ⅱ泥岩夹层附近剪切应变高度集中,进而引起泥岩夹层套管的剪切变形与错断。萨Ⅰ—萨Ⅱ泥岩夹层的剪切应变增量随泥岩含水率的增大而增大,且其随地层压力增大而增大的速率在泥岩浸水后明显增大。因此,在泥岩浸水后,应适当降低泥岩夹层毗邻储层的注水压力和地层压力,从而缓解泥岩夹层的剪切套损。
Taking the Xingshugang southern development zone in Daqing Oil Region as an example, the numerical simulation of stress and strain perturbation caused by muddy water softening in the process of injection and production was carried out. The disturbance of stress and strain caused by muddy water immersion was discussed, and the influence of formation pressure and stress strain The impact of the relationship. The results show that mudstone flooding has different disturbance to stress in different layers, resulting in differences in interlayer stress states. Differences in interlaminar stress state, weakening of mechanical properties of mudstone after soaking in water, pressure difference of pore fluid and interlayer fluid caused by injecting and extraction, permeability and lithology difference between mudstone and sandstone, and high pressure water injection Effective stress reduction and other factors, leading to a high concentration of shear strain near Sa Ⅰ-Sa Ⅱ mudstone interlayer in the Salto Formation, which in turn leads to shear deformation and fault of the mudstone interlayer casing. The shear strain increment of Sa Ⅰ-Sa Ⅱ mudstone interlayer increases with the increase of mudstone moisture content, and its rate of increase with formation pressure increases obviously after mudstone immersion. Therefore, after mudstone immersed in water, the injection pressure and formation pressure of adjacent reservoirs of mudstone should be reduced appropriately, so as to relieve the shearing damage of mudstone interlayer.