流体损害对页岩储层应力敏感性的影响

Influence of Fluid Damage on Shale Reservoir Stress Sensitivity

非常规油气资源正在发挥越来越重要的作用,页岩气以其巨大的资源量及在美国开发的成功事实,促使其成为当前研究的热点。页岩储层富含粘土矿物,流体敏感性损害和应力敏感性损害是损害泥页岩储层的2种重要因素,两者耦合将极大地降低储层的渗透率,制约着开发页岩气工程技术的效果。以泥页岩储层的流体敏感性实验为基础,开展了应力敏感性评价研究,对比流体损害前后的应力敏感性差异。结果表明,储层为中等偏强的水敏性、强的碱敏性和中等偏强的酸敏性;流体损害后的储层应力敏感性系数较损害前增大30%,为强应力敏感程度。粘土矿物微粒分散运移、水化膨胀、流体润滑作用导致岩石强度降低,并使渗流通道更易变窄,加剧了应力敏感性损害。因此,工程作业中减少不配伍流体的侵入对页岩气储层的保护和开发具有特殊意义。

Unconventional oil and gas resources are playing an increasingly important role. Shale gas has become a hot spot and frontier in current research due to huge resources and successful exploitation in the United States. Since shale reservoir is rich in clay mineral, the damages of fluid sensitivity and stress sensitivity are two important damage factors. The coupling action of two damages will greatly decrease the permeability of reservoir and restrict the engineering effect on developing shale gas. Based on fluid sensitivity of clay shale reservoir,we carried out the stress sensitivity,in comparison with difference of stress sensitivity before and after fluid damage. The results show that the stress sensitivity coefficients after fluid damage in- crease by 30 ~ for the three type reservoirs with medium-strong degree water sensitivity, strong degree alkali sensitivity and medium-strong degree acid sensitivity, indicating the strong stress sensitive degree. The discrete migration of clay mineral particle,hydrate expansion, fluid lubrication cause the decrease of rock strength, make the seepage channel become narrow, and increase the stress sensitivity damage. Therefore,it is a special significance for the protection and economic development of gas shale reservoir to reduce the in- vasion of incompatible fluid in the well operation.