基于压敏效应的变启动压力梯度面积井网产量计算模型

特低渗透油藏流体呈非线性流动,受压敏效应影响显著,渗透率随地层压力的变化而变化,从而导致启动压力梯度变化,严重制约油田生产。目前已有的特低渗透油藏面积井网产量计算模型未同时考虑压敏效应和变启动压力梯度问题,导致计算结果与实际情况偏差较大,适用性较差。针对这一问题,文中基于特低渗透油藏渗流理论及压敏效应公式,分析了压敏效应对渗透率和启动压力梯度的影响,建立了变启动压力梯度模型,推导了考虑压敏效应和变启动压力梯度的五点法、四点法和反九点法井网产量计算模型以及启动系数计算模型。实例结果表明,模型计算结果更接近实际情况,可用于评价不同井网条件下储层动用状况,为特低渗透油藏开发调整方案编制提供理论依据。

Production calculation model of areal well pattern with variable start-up pressure gradient based on pressure sensitive effect

The fluid flow of the ultra-low permeability reservoir is non-linear and affected by the pressure sensitive effect significantly.The permeability varies with formation pressure,which leads to changes of start-up pressure gradient and seriously restricts the oilfield production.The existing production calculation model of areal well pattern of ultra-low permeability reservoir does not consider the pressure sensitive effect and the variable start-up pressure gradient at the same time,which results in a large deviation between the calculation result and the actual situation,and the applicability is poor.To solve this problem,based on the seepage theory and the pressure sensitive effect formula,this paper analyzes the impact of pressure sensitive effect on permeability and start-up pressure gradient,establishes the variable start-up pressure gradient model.Considering the pressure-sensitive effect and the variable starting pressure gradient,the production calculation model and start-up coefficient calculation model of five-spot,four-spot and inverted nine-spot well pattern was derived.The results of the example show that the model calculation results are closer to the actual situation and can be used to evaluate the reservoir producing status under different well patterns,which provides theoretical guarantee for designing development adjustment scheme of ultra-low permeability reservoir.