低速非线性是低渗油藏的流动机制

Low Velocity Nonlinearity is the Flow Mechanism of Low Permeability Reservoir

由于早期设备精度低,因此基于低渗样品的实验室测量数据表现出启动压力梯度特征;由于含启动压力梯度的渗流方程是非线性的,因此基于叠加原理得到的关井压力双对数曲线上翘,与实测数据一致,二者误导了启动压力梯度是低渗透储层渗流的特征。然而,随着设备精度的提高,更多实验揭示出低渗样品的非线性渗流特征。更为重要的是,数值解表明,启动压力梯度使得关井段的压力导数曲线下掉,揭示了叠加原理不适应性所导致的误差,改变了试井曲线的后期形态;低速非线性流动模型使关井压力导数曲线上翘,低速非线性渗流模型才是低渗油藏的流动机理。生产动态数据进一步验证了低速非线性是低渗油藏的流动机制。

Due to the low precision of the early equipment,the laboratory measurement data based on the low permeability samples show the characteristics of threshold pressure gradient.Because the flow model incorporating the threshold pressure gradient is nonlinear,the log-log curve obtained based on superposition principle is upward,which is consistent with the measured data.Both of them mislead that the threshold pressure gradient is the characteristics of flow mechanism in low permeability reservoir.However,with the improvement of equipment accuracy,more experiments reveal the nonlinear seepage characteristics based on low permeability samples.More importantly,the numerical solution shows that the threshold pressure gradient leads to drop-down of the pressure derivative curve of buildup pressure,which shows that the inadaptability of applying superposition principle to solve flow model with threshold pressure gradient,changes the later shape of well test curve.It further shows that low-speed nonlinear flow model leads to the upward pressure derivative curves,and the low-speed nonlinear seepage model is the flow mechanism of low-permeability reservoir.The verification of production performance data,further verifies that low-speed nonlinearity is the flow mechanism of low-permeability reservoirs.