特低渗透油藏压裂水平井产量递减规律

基于考虑启动压力梯度和压敏效应综合影响的广义达西定律，以椭圆渗流理论和平均质量守恒定律为基础，分别建立了无限导流垂直裂缝井和有限导流垂直裂缝井的不稳态渗流理论，进而通过叠加原理建立了带有任意裂缝条数的压裂水平井产量递减模型，分析了压裂水平井不稳态时期的产量递减规律。结果表明，压裂水平井初期产量比较高、递减比较快，但是产量很快进入缓慢递减、平稳变化阶段。启动压力梯度、变形系数越大，压裂水平井单井产量越低；当启动压力梯度大于0.01 MPa/m以后，对产量及其递减规律的影响显著。压裂缝条数越多、裂缝越长、导流能力越大，压裂水平井产量也越高，递减速度也越快，但随着压裂缝条数、长度和导流能力的增加，产量增幅逐渐变小。

Production decline laws of fractured horizontal wells in ultra-low permeability reservoirs

Based on the generalized Darcy’s law that considers a comprehensive influence of the threshold pressure gradient and the pressure-sensitive effect,we proposed transient seepage theories on infinite-and finite-conductivity vertically fractured wells respectively,which follow the elliptic seepage theory and average mass conservation law.A production decline model for fractured horizontal wells with arbitrary numbers of transverse hydraulic fractures was then established on the basis of the superposition principle,and accordingly production decline laws of fractured horizontal wells at unsteady-state periods were investigated.The results show that the initial production of multi-fractured horizontal wells(MFHW) is relatively high but soon followed by a sharp decline.Then,the production keeps in a relatively stable state and declines slowly.The greater the threshold pressure gradient and the deformation coefficient,the lower the per-well production of MFHW will be.Furthermore,the threshold pressure gradient will influence the production and decline laws of MFHW remarkably when it exceeds 0.01 MPa/m.The more the hydraulic fracture numbers the longer the fracture length and the bigger the flow conductivity,and then the higher the production of MFHW and the faster the decline rate will be.However,the increase amplitude will be getting smaller and smaller along with the increase of hydraulic fracture numbers,fracture length and flow conductivity.