油气藏改造时因地层非均质性的影响可能形成垂直裂缝不关于井筒对称,而关于不对称垂直裂缝对油井产量影响研究较少。因此,针对低渗油藏经压裂后产生的不对称垂直裂缝,基于稳定流理论,利用保角变换方法,推导了考虑启动压力梯度影响的低渗油藏有限导流不对称垂直裂缝井产能的预测模型,通过实例分析了多种因素对不对称垂直裂缝油井产量的影响。研究表明:油井产量随着启动压力梯度增大呈近似线性下降,且在相同的启动压力梯度下,油井产量下降幅度随压差增大而减小;当裂缝导流能力较小时,不同裂缝长度或裂缝非对称率对油井产量影响程度差异较大,当裂缝导流能力较大时,不同裂缝长度或裂缝非对称率对油井产量影响程度差异较小;裂缝长度越长,裂缝非对称率越小,裂缝非对称率对油井产量影响程度越大;裂缝非对称率在(0.6,1)范围时,可以忽略其对油井产量的影响。

In view of the low permeability reservoir after fracturing development that can cause the asymmetrical vertical fracture, the productivity of this oil well is little information. Thus based on the steady seepage theory, with the aid of conformal transformation method, a prediction model for the finite-conductivity asymmetrical vertical fracture wells was established, and the various factors on the productivity of oil well were analyzed, under the influence of the start-up pressure gradient in the low-permeability oil reservoirs. The result shows that the decrease of productivity decreases is caused by start-up pressure gradient. In the same start-up pressure gradient, the productivity decreases with the increase of the production pressure. When the conductivity capacity of fracture becomes small, there is obviously difference for the productivity of fracture oil well in the crack length and fracture asymmetry factor. And when the conductivity capacity of fracture becomes big, there is little difference for the productivity of fracture oil well in the crack length and fracture asymmetry factor. The longer is the crack length and the less is the fracture asymmetrical factor, the greater is the productivity of the fracture oil well.