Hydroelectric simulation test of coalbed methane in symmetric multi branch horizontal wells

Since multi-branch horizontal wells are wells with complex structures, the seepage law of underground fluids can’t be described accurately by conventional numerical simulation methods and mathematical analysis. In order to observe the flow of coal bed methane(CBM) more intuitively under complex conditions, hydropower simulation experiment platform is designed and built on base of the theory of porous media to comprehensively study the influence of borehole structural parameters such as branch number, branch length, branch angle, etc. on the distribution of coal-bed pressure, total productivity and productivity per unit length, and analyze to verify whether there is branch interference between multi branch horizontal wells. The results show that the influence of borehole structure parameters on the pressure curve of CBM mainly includes that the value of isobars of pressure distribution of CBM decreases continuously with the increase of the number and length of branches corresponding to the same coordinate points and isobars of pressure distribution become sparse on the whole, which means that the isobars of pressure distribution of CBM and the pumping range increase with the increase of the number of branches;When the branch angle is 30°, 45° and 60°, the deformation amplitude of 45° branch angle is the most obvious; The pressure curve of coalbed methane is greatly affected by the fingertip effect of branches. There is interference between symmetric multi-branch horizontal wells and its branches. The key to control the interference is to reasonably control the relationship of branch number, branch length and branch angle by adjusting the comprehensive shape parameters. The optimization level among the branch number, branch length and branch angle is branch number>branch length>branch angle; When the test parameters are 4 branches, 200 mm branch length and 45 ° branch angle, the borehole structure parameters can control the branch interference extremely, the production efficiency and production cost of CBM can reach the best state. 