页岩油压裂水平井变导流能力试井模型研究

致密油气、页岩油气等非常规油气资源由于其储层渗透率低，在开采过程中往往采用水平井多级压裂技术来提高单井产量，实现经济开采。基于渗流力学，建立了考虑应力敏感、变裂缝导流能力的裂缝性油气藏多段压裂水平井试井数学模型，通过Laplace和Fourier变换等方法求得模型在Laplace空间下的无因次井底压力解；用Stehfest数值反演计算了实空间无因次井底压力。研究表明，当所有无因次裂缝导流能力之和不变时，如果井筒两端裂缝导流能力高于中部裂缝导流能力，早期阶段生产压差小，压力曲线低；当无因次裂缝导流能力沿裂缝方向减小时，无因次裂缝导流能力变化梯度越大，生产压差越大，早期阶段无因次压力曲线越高；应力敏感系数越大，无因次压力及压力导数曲线上翘幅度越大；裂缝储容比越小，窜流段压力导数曲线“凹子”越深；窜流系数越大，窜流发生越早。

Well Test Analysis of Multi-stage Horizontal Well with Varying Conductivity in Naturally Fractured Shale Oil Reservoir

Because of low-permeability property,horizontal well multi-stage fracturing technology is widely used to improve oil well production,and achieve economic value,such as tight and low-permeability oil and gas reservoirs.Based on the seepage mechanics,a mathematical model of multi-stage fractured horizontal well is stablished with consideration of stress sensitivity and varying conductivity.The model is solved by employing Laplace and Fourier integral transformation,pressure drop superposition principle and fracture discrete coupling method in Laplace domain.The Stehfest numerical inversion algorithm is used to calculate dimensionless wellbore pressure in real space and dimensionless pressure and its derivative log-log curve is drawn.The results show that if hydraulic fracture conductivity located at wellbore end-node fracture is higher than that of hydraulic fracture located at wellbore middle fracture,dimensionless pressure curve is lower during early bilinear flow and linear flow stage and production pressure difference is smaller.When the dimensionless conductivity decreases along the direction of the hydraulic fracture,the bigger the gradient is,the higher the dimensionless pressure curve is during the early stage,and the bigger the production pressure difference is.The larger the stress sensitive coefficient,the larger the creep amplitude of the dimensionless pressure and its derivative curve;the smaller the reservoir-capacity ratio,the earlier the cross-flow occurs,the longer the cross-flow duration.The larger the cross-flow coefficient,the earlier the channeling occurs.The results can provide guidance for well test data interpretation in fractured reservoirs.