再谈岩石本体变形的孔隙度不变原则

油藏岩石的本体变形中,骨架颗粒形状不变的假设认为岩石在压缩过程中孔隙度保持不变,然而,岩石骨架颗粒的形状并非严格保持不变.为研究骨架颗粒形状变化对孔隙度的影响,基于弹性变形模型,采用有限元数值模拟方法,研究了多孔介质本体变形过程中的骨架颗粒变形及其对孔隙度的影响机制.结果表明,加载过程中骨架颗粒在约束方向(颗粒接触位置...

Re-discussion on principle of constant porosity during primary deformation of rock

In the primary deformation of reservoir rocks,the assumption that the shape of the skeleton particles remains unchanged assumes that the porosity of the rocks remains unchanged during the compression process.However,the shape of the skeleton particles does not strictly remain unchanged.In order to study the influence of the shape change of skeleton particles on porosity,based on the elastic deformation model,finite element numerical simulation method was used to study the deformation of skeleton particles and its influence mechanism on porosity during the primary deformation of porous media.The results show that the displacement of skeleton particles is small in the constraint direction(particle contact position),and it is larger in the unconstrained direction(pore position),which changes the shape of the particles,reduces the porosity of rock.However,the young's modulus of rock minerals is larger,and the constraint conditions of the rock skeleton particles are more demanding than those in numerical experiments.Therefore,the effect of skeleton particle deformation on porosity is very weak.In the numerical experiments,rigid epidermis has only a certain effect on the initial porosity value.However,the flexible skin in the core gripper has a great influence on the measurement process,which is the direct cause of the great change of porosity in the experiment.Therefore,in the process of reservoir production,the deformation process of rock can still be considered to follow the“porosity invariance principle”.