低、特低渗透油藏压裂水平井产能计算方法

考虑低、特低渗透油藏裸眼压裂水平井流体从基质-裂缝-水平井筒及基质-水平井筒的耦合流动,以等值渗流阻力法及叠加原理为基础,将裸眼压裂水平井渗流区域划分为三个流动区域:流体在水平井压裂裂缝内的达西线性流动区域、水力压裂裂缝泄流引起的非达西椭圆渗流区域和流体在地层中的径向渗流区域.建立裸眼水平井水力压裂多条横向裂缝相互干扰的非达西产能预测模型,分析水力裂缝参数对产能影响,揭示裸眼压裂水平井开采变化规律.模拟结果表明:裂缝条数越多,裂缝干扰越强,水平井压裂存在一最优裂缝条数;裂缝沿水平井筒排布靠近两端、中间相对较稀,且两端长、中间短的开发效果最好. 

A method to predict the production of fractured horizontal wells in low/ultra-low permeability reservoirs

In consideration of the matrix-crack-wellbore coupling flow and matrix-wellbore coupling flow in an open-hole fractured horizontal well in low/ultra-low permeability reservoirs, mathematical models were derived on the basis of the equivalent flowing resistance method and the superposition principle. For an open-hole fractured horizontal well, the flow field was divided into three regions according to the different flow mechanism:Darcy flow in artificial fractures, low-velocity non-Darcy elliptical flow in the matrix around artificial fractures, and low-velocity non-Darcy plane radial flow in the peripheral matrix. A non-Darcy analytical productivity equation for an open-hole fractured horizontal well was obtained considering mutual interference between multi-transverse fractures. The influences of hydraulic fracture parameters on oil production were analyzed, which reveals the variation in development of an open-hole fractured horizontal well. Numerical results show that the more the artificial fractures, the stronger the interference of artificial fractures, and consequently there exists an optimal quantity of artificial fractures. It is suggested that the artificial-fracture distribution should be dense at two ends of the wellbore and sparse in the middle of the wellbore; in addition, the length of artificial fractures at the two ends should be larger than that in the middle.