分形煤层气藏有限导流多翼压裂直井试井模型

Fractal well test model for multi-wing fractured vertical well with finite conductivity in the coal bed methane reservoir

煤层气藏储层中孔隙裂缝分布杂乱、无序,传统欧几里得空间试井模型无法对其进行描述。考虑储层应力敏感性,建立分形煤层气藏有限导流多翼压裂直井试井模型。利用数值离散和叠加原理等方法求解模型,得到井底压力解;绘制井底压力动态曲线并划分流动阶段,对相关参数进行敏感性分析。结果表明:考虑分形特征的压力图版与传统图版存在一定差异;质量分形维数和反常扩散指数对压力动态曲线影响较大,人工裂缝条数、长度、角度和导流能力主要影响中期曲线,应力敏感因子主要影响后期曲线。该结果更好地反映多翼压裂直井的煤层气流动特征,为研究分形煤层气藏提供一种参数反演方法。

The well test model in the traditional Euclidean spatial cannot describe the complexities and randomness of the coalbed methane(CBM)reservoir.A fractal well test model for multi-wing fractured vertical well with finite conductivity in CBM reservoir is established which takes the stress sensitivity into account.Through discretization and superposition principle,the solution of bottom hole pressure is obtained by solving the established model.The bottom hole pressure curve is drawn and the flow regimes can be divided,then sensitivity analysis is conducted.The results show that after considering the fractal characteristics,there is a certain difference from the traditional curves.The mass fractal dimension and the anomalous diffusion index have a great effect on the overall pressure and production curves.The main effect on the number,length,angle and conductivity of artificial fractures is reflected in the middle period.The main effect of the stress sensitivity factor is reflected in the later period.Relevant knowledge can better reflect the flow characteristics of CBM in multi-wing fractured vertical well and provide a theoretical method for parametric inversion.