煤层气水平井井周围岩热流固耦合数值分析

Numerical Analysis of Fluid-solid-heat Coupling of Surrounding Rock Around Coalbed Methane Horizontal Wells

煤层气井壁失稳是影响煤层气产业化开采的重要原因之一,以宁武盆地9#煤层的煤层气水平井为研究对象,运用有限元软件分析了2种条件(不考虑热流固耦合作用的影响和考虑热流固耦合作用的影响)下井周的应力分布和变形情况。模拟结果发现:考虑热流固耦合作用时,结果与工程实际更加吻合;水平井井周围岩所受的Tresca应力、第一、第二和第三主应力均存在应力波动区域,该区域容易产生新生裂隙,降低了井周围岩的强度,容易产生井壁失稳事故;在AB弧长上,井周围岩大于8.0 cm的井段上,井周变化率大于5.0%,容易产生井壁失稳事故。

The well wall instability is one of the important reasons that affect the industrial exploitation of coalbed methane.In this article,the coalbed methane horizontal well of No.9 coal seam in Ningwu basin was taken as the research object.We analyze the stress distribution and deformation around the well under the influence of fluid-solid-heat coupling and without fluid-solid-heat coupling by the finite element software.The simulation results from fluid-solid-heat coupling are in good agreement with the engineering practice.The Tresca stress,the first,the second and the third principal stresses in the surrounding rock of horizontal well are in the region of stress fluctuation,so it is easy to produce new fractures,and reduce the strength of surrounding rock,which causes instability accidents of well wall easily.In the arc length of AB,in the well section of surrounding rock around the wall（larger than 8.0 cm）,the change rate of surrounding rock around well is more than 5%,which is easy to produce well wall instability accidents.