有效应力对裂缝型低渗透砂岩油藏压力响应的影响

Effect of effective stress on fractured low-permeability sandstone reservoir pressure response

为了研究裂缝孔隙型低渗油藏中流体在双重介质之间的渗流规律及其影响,建立了双重介质间流体窜流的数学模型,并利用拉氏变换数值反演方法给出近似解析解;通过数值计算,研究窜流压力的动态特征,分析储容系数及窜流系数对压力响应的影响;通过压敏试验研究了有效应力对双重介质低渗油藏渗流能力的影响。研究结果表明:储容系数主要决定双重介质之间发生窜流现象的早晚,储容系数越大,发生窜流的时间越晚;储容系数越小,发生窜流的时间越早。窜流系数主要决定双重介质之间发生窜流压力的大小,窜流系数越大,发生窜流的压力越小;窜流系数越小,发生窜流的压力越大。有效应力对裂缝型低渗透油藏的渗流能力影响很大,有效应力的增加能够大大降低裂缝型油藏渗透率和孔隙度,以致降低储层的储容系数和窜流系数,从而影响双重介质间窜流压力的动态特征。因此,在裂缝型低渗透砂岩油藏开采中,保持压力、防止储层伤害是非常重要的。

In order to study the seepage law and influential factors of flow in double porosity medium in the pore-fractured low-permeability reservoir,the dual-media cross-flow mathematical model is established and its solution is given.By numerical solution,the pressure dynamic characteristics and effects of storage coefficient and interporosity flow coefficient on pressure response are researched.By pressure-sensibility experiment,the effect of effective stress on percolation ability of double porosity medium low-permeability reservoir is studied.The study shows that the larger storage coefficient is and the later happening interporosity flow time is,the smaller interporosity flow coefficient is the larger interporosity flow pressure is.Permeability and porosity decrease when effective stress increases,which changes storage coefficient and interporosity flow coefficient and effects pressure dynamic characteristics.So keeping pressure and protecting reservoir are important for developing the pore-fractured low-perm eability reservoir.