Study on physical property characteristics and main controlling factors of coalbed methane reservoir in northern Hancheng Mine Area

Abstract

Based on the comprehensive collection of geological exploration data and experimental test results of coal seam and coalbed methane in the study area, we adopt quantitative analysis method to systematically analyze the change law of adsorption capacity, gas content, in-situ stress, porosity and permeability of coal seam, and emphatically discuss the main controlling factors and development geological conditions affecting the occurrence of coalbed methane in the area. The study shows that the gas content of coal seam in this area is generally controlled by the burial depth, which is high in the west and low in the east. Longitudinally, the metamorphic degree of coal increases with the increase of buried depth. When the burial depth is less than 1 000 m, the positive effect of pressure plays a dominant role. The gas content, gas saturation and permeability increase with the burial depth increasing, while the porosity decreases with the burial depth increasing. When the burial depth is more than 1 000 m, the negative effect of temperature plays a dominant role. The gas content and gas saturation decrease with the increase of the burial depth, the porosity gradually rebounds, and the permeability gradually decreases. The transitional burial depth of both is from 750 m to 1 000 m. The buried depth is less than 750 m, the horizontal stress is the main stress field, and it is a compressive in-situ stress field. The buried depth is between 750 and 1 000 m, and the vertical stress is predominant in part, showing tensile in-situ stress field, which is conducive to the development of fracture, and the permeability is better, and the permeability increases with the increase of the buried depth. When the buried depth is greater than 1 000 m, it is transformed into compressive in-situ stress field again, and the permeability decreases greatly with the increase of buried depth.

Keywords

• coalbed methane
• burial depth
• gas content
• permeability
• in-situ stress