洞穴完井煤层中渗流场的数值研究

Numerical Study on Seepage Field in Coalbed With Cavity Well

提出了煤层气井洞穴完井的物理模型,将完井洞穴看成一个在煤层气井井底附近渗透率远大于外区煤层的高渗区域,并假定该区域中的流体流动仍然符合Darcy流动。在此基础上建立了煤层气井洞穴完井的渗流数学模型,通过有限元求解方法得到了洞穴完井煤层气井在圆形煤层和任意四边形煤层中的渗流场分布。为了与裸眼完井煤层气井的渗流场进行对比,模拟了圆形存在一口洞穴完井煤层气井和一口裸眼完井煤层气井及一口洞穴完井煤层气井和两口裸眼完井井的渗流场,明显看出了洞穴完井煤层气井渗流场与常规裸眼完井井的差异。该研究成果对更好地了解洞穴完井煤层气井的流体流动规律及压力分布状态有积极的意义。

Physical model of fluid flow in coalbed with CBM cavity well is described in this paper at the first time.Near the wellbore there exists a high permeability region whose permeability is far greater than that of the coalbed far from the CBM well.The fluid flow in this region also obeys Darcy's flow.Based on the description of physical model,mathematic model for fluid flow in coalbed wih CBM cavity well is developed in this paper.Seepage field in coalbed with CBM cavity well is obtained under circular and arbitrary quadrilateral outer boundary by using finite element method.In order to compare seepage field in coalbed with CBM cavity wells with that of open hole completion well,seepage is simulated about one cave completion,one open hole completion and one cave completion,two open hole completions.So the difference of seepage between cave completion and open hole completion is visible.The results of this research is significant important to comprehend fluid flow mechanics and pressure distribution in coalbed with CBM cavity wells.