Hydrological control mode and production characteristics of coalbed methane field in Shouyang Block

The relationship between groundwater replenishment, runoff and discharge to the coal seam affects not only the degree of coalbed methane (CBM) enrichment, but also the gas production characteristics of CBM wells. In order to identify the influence of hydrogeological conditions on CBM enrichment and gas production, the No. 15 coal seam in Shouyang block was used as the research object, and based on the ion test data of drainage water and underground water potential, the relationship between chemical characteristic parameters of drainage water, underground water potential and gas content was analyzed, combined with the hydrological control gas effect, and three types of reservoir control models were proposed. According to the water production, gas production curve shape and genetic mechanism of CBM wells under different reservoir control modes, six production control characteristics are divided, and corresponding development suggestions are put forward. The results show that: hydrochemical characteristic parameters and groundwater potential are significantly correlated with gas content. That is, the greater the mineralization and metamorphic coefficient, the smaller the sodium-chloride coefficient, carbonate equilibrium coefficient, and groundwater potential, the higher the gas content. Hydrodynamic force controls the escape and accumulation of coalbed methane by hydrodynamic dissipation, plugging and sealing. In the reservoir area controlled by hydrodynamic dissipation, low gas content is the main controlling factor of low production of CBM wells, and the development risk is high. In hydrodynamic plugging control areas, the water production of coalbed methane wells is generally large. Among them, strong hydrodynamic, low permeability prone to high water production and low production gas wells, not recommended for development; strong liquid supply capacity and low permeability are prone to medium water production and low production gas wells, the effect of reservoir reconstruction determines the feasibility of development. High production of water and gas is easy to occur in areas with high permeability, so the continuity of drainage should be pay attention. In hydrodynamic closed reservoir-controlling areas the water production of coalbed methane wells is generally small. Among them, low permeability reservoirs are prone to low water production and low gas production wells, so attention should be paid to the effectiveness of reservoir reconstruction; in the areas of high permeability reservoir, there are generally medium-high-yield gas wells. The continuity of drainage and production should be maintained as much as possible to reduce reservoir damage. The research results can provide theoretical guidance for the deployment of CBM wells.