基于数值模拟方法的水力压裂分支裂缝产能预测研究

Study on Productivity Prediction of Hydraulic Fracturing with Branch Fractures Based on Numerical Simulation Method

水力压裂是开发低孔、低渗/特低渗油气储层无可替代的技术.而在重复压裂、转向压裂和体积压裂中均可能产生分支裂缝,对于水力压裂后形成分支裂缝的储层进行产能预测是非常必要的一项工作.建立了数学模型对具有分支裂缝系统的储层进行了产能模拟.首先,通过定量化描述裂缝的起点位置、角度和长度,实现了裂缝系统的描述.其次,采用二维单相可压缩液体不稳定渗流,将带有分支裂缝的储层视为各向异性的非均质储层,建立了数学模型.并根据数学模型,采用中心差分法建立差分方程组,给出了计算步骤和流程.最后,对实际的一口井进行了拟合并进行了敏感性参数分析,效果较好.数学模型和方法可作为分支裂缝产量预测的有效工具.

Hydraulic fracturing is an irreplaceable technology for the development of low porosity,low permeability and ultra-low permeability reservoirs.Branch frectures may occur in repeated fracturing,steering fracturing and volume fracturing.It is very necessary to predict the productivity of reservoirs with branch fractures after hydraulic fracturing.This paper establishes a mathematical model to simulate the productivity of reservoirs with branch fracture system.Firstly,the description of the fracture system is achieved by quantifying the starting position,angle and length of the fractures.Secondly,the mathematical model is established by using two-dimensional seepage model and treating the reservoir with branch fractures as anisotropic heterogeneous reservoir.According to the mathematical model,the difference equations are established by the central difference method,and the calculation steps and flow chart are given.Finally,the actual well was fitted and sensitivity studies to quantify the key parameters affecting the well performance were performed.The effect was satisfactory.The mathematical model and method can be used as an effective tool for predicting the production rate of branch fractures.