Optimization of coal-bed methane multi-layer co-production layer combination in Xiaotun Wellfield of western Guizhou Province

Abstract

The coal measures of Longtan Formation in Xiaotun well field, Guizhou Province have the characteristics of large number of coal seams, small spacing of coal seams and thin thickness of coal seams. Compared with single thick layer coal seam, multi-seam co-mining is prone to inter-layer interference, which affects co-mining effect and resource utilization degree. Based on the analysis of the lithology and gas content of the borehole in Xiaotun well field, three types of coal-rock seam combinations, namely favorable, more favorable and unfavorable, were identified, the thickness, depth of burial and gas content of each coal seam were examined, the coal-bed methane resource conditions of each coal seam were compared, the storage combination, gas content, permeability, reservoir pressure, ground stress and other factors were considered, and three sets of stacked coal-bed methane systems, I (6 upper coal + 6 middle coal + 6 lower coal), II (7 coal) and III (33 coal + 34 coal), were divided. On the basis of this, we optimize the combination of production seams, and determine the orderly development mode to give priority to the upper production seam combination (6 upper coal + 6 middle coal + 6 lower coal), followed by the lower combination (33 coal + 34 coal), and finally consider the economic and time cost to determine whether to develop 7 coal alone. The optimized idea of coal-bed methane joint mining in multi-thin seam development area is established by analyzing the resource conditions, classifying the gas-bearing system and optimizing the production layer combination.

Keywords

• stacked coal bed methane system
• combined mining of multiple coal seams
• desorption pressure
• production layer combination
• reservoir physical properties