煤层气井解吸区预测模型研究

The predictive models of desorption region for coalbed methane wells

为跟踪了解煤层气开发动态,实现煤层气藏储量动用程度评价、井网优化等目标,建立煤层气解吸区扩展预测方法.基于煤层气两相流阶段生产气水比特征,运用稳态逐次替换法,建立不同生产阶段两相流稳态压力分布模型;结合物质平衡方程,提出并建立煤层气直井、压裂直井解吸区扩展预测模型.研究结果表明:该模型预测解吸区范围与数值解吻合较好.在韩城煤层气小井组应用、直到生产525d后,A井解吸区椭圆长短半轴范围分别为150.5～188.0m,138.0～178.0m;B井分别为170.0～215.0m,159.0～206.5m,此时A,B两井解吸区已干扰或接近干扰,而C,D两井投产后解吸区很快与A井干扰.

In order to follow and understand the developing dynamic of coalbed methane,a predictive model of desorption region expanding for coalbed methane well is established for the purpose of realizing the goal of reservoir evaluation and well pattern optimization.Based on the characteristics of gas-water ratio during the production of coalbed methane（CBM） well,the method of ＂continuous succession of steady states＂ is used to establish the pressure distribution model at different production stages.Combining with material balance equation,the predictive model of desorption region is proposed and established for vertical wells and hydraulically-fractured vertical wells.The results show that the scope of desorption region predicted by this model fits well with the numerical solutions.Furthermore,the model is applied on CBM well group in Hancheng field and it shows that the shape of desorption region is elliptical.After producing for 525 days,the major semi axis of ellipse in the desorption region for well A ranges from 150.5 to 188.0 m,minor semi axis from 138.0 to 178.0 m.For well B,the major semi-axis ranges from 170.0 to 215.0 m,and the minor semi-axis from 159 to 206.5 m.At the moment,desorption regions of well A and well B have almost or already interfered with each other.And well C and well D will interfere with the desorption region of well A once they are put into production.