两区复合煤层气藏多分支水平井压力动态分析

Transient Pressure Analysis of Multilateral Horizontal Well in Coal Bed Methane Reservoir with Two Regions

在综合考虑渗透率应力敏感效应的情况下,建立了一种两区复合煤层气藏多分支水平井的半解析模型。基于点源解、Laplace变换、Pedrosa变换、摄动变换、有限余弦变换、数值离散以及叠加原理,求解得到井底压力解,利用Stehfest数值反演的方法绘制了双对数坐标下的无因次试井动态曲线图并将流动形态划分为13个阶段;进行了敏感性参数分析,包括渗透率模量、多分支水平井的形状参数(分支井的长度、分支井距离和分支井个数)、内外区窜流系数和吸附系数、内区半径以及内外区流度比对压力动态曲线的影响。该半解析模型以及相关的结果分析对于更好地理解两区复合煤层气藏多分支水平井的流动特征具有指导意义。

Considering the stress sensitivity effect of permeability,a semi-analytical model for MLHWs in CBM reservoir with two regions is established.Bottom hole pressure is obtained by solving the semi-analytical model based on the point sink solution,Laplace transformation,Pedrosa transformation,Perturbation transformation,finite cosine transformation,element discretization and superposition principle.By using Stehfest numerical inversion method,the dimensionless well test dynamic curve under the double logarithmic coordinate is drawn and it is can be divided into thirteen flow regimes.Then,the influences of permeability modulus,shape parameters of multilateral horizontal well(branch length,branch distance and branch number of multilateral horizontal well),the channeling coefficient and adsorption coefficient of internal and external zones,the radius of internal zone and the mobility ratio of internal zone to external zone on the pressure dynamic curve are analyzed.The semi analytical model and the related analysis results are of guiding significance to better understand the flow characteristics of multilateral horizontal wells in the two-zone composite coalbed methane reservoir.