Practice and understanding of multi-layer drainage of CBM wells in Liupanshui area

To improve the effect of drainage and extraction of coalbed methane wells, it is necessary to divide the drainage and production stages reasonably and formulate corresponding control measures. Based on the previous exploration and trial production of coalbed methane in Liupanshui area, this paper analyzed the geological characteristics of coalbed methane and the development characteristics of coal reservoirs in the area, and studied the drainage effect of the combined layers of two wells comparatively. The research shows that the area has several basic characteristics, including many coal seams, thin single-layer thickness, high gas content, high reservoir pressure, low coal seam permeability, and local developed tectonic coal, which leads to the pressure-sensitive effect and obvious Jiamin effect in the drainage process, so it caused serious reservoir damage, short production time and low production of coalbed gas wells. Therefore, it is preferable to perform perforating fracturing for a native structure with excellent media and good gas-bearing properties. During the combined mining and drainage process, the phases of combined mining and drainage was clearly divided, and it was pointed out that according to the drainage and mining stage, the flow pressure, casing pressure, flow pressure drop, sleeve pressure drop and liquid height should be controlled to reduce reservoir damage such as pressure sensitivity effect, Jiamin benefit, and speed sensitivity effect; The steady rise in gas production should be controlled, and long-term stable production and high production of coalbed gas wells should be achieved.