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

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.