Determination of reasonable reduction in single-phase water flow stage of coalbed methane wells in Wulihou Mine Field

In order to determine the reasonable reduction of the single-phase water flow stage of coalbed methane wells, the water pressure propagation distance of coalbed methane wells is ensured to the maximum. Taking Wulihou coalbed methane well as the research object, the groundwater potential in the study area is calculated, and the relationship between the groundwater potential and the average daily water volume is obtained by fitting. Based on the average value of groundwater potential in the study area, the groundwater potential in the study area is divided into high groundwater potential and low groundwater potential, and the difference of water production characteristics of coalbed methane wells in high and low groundwater potential areas is analyzed. Based on the relationship between groundwater potential, formation liquid supply index and flow back rate of fracturing fluid in the single-phase water flow stage, a mathematical model of reasonable drop in the single-phase water flow stage is established. The accuracy of the model is verified by the production data in the study area. On this basis, according to the difference of groundwater potential in the study area, the reasonable reduction range of the corresponding single-phase water flow stage is predicted. The results show that there is a positive correlation between groundwater potential and average daily water volume in the study area. The water production characteristics of coalbed methane wells in different groundwater potential areas are obviously different. In the high groundwater potential area, the daily water output of coalbed methane wells increase rapidly in the early stage of production and decrease significantly in the middle and later stages of production. In the low groundwater potential area, the daily water volume of coalbed methane wells increase slowly in the early stage of production, and there is no significant change in the middle and later stages of production. In the single-phase water flow stage, with the increase of groundwater potential, the formation liquid supply index and fracturing fluid flowback rate also increase. The reasonable drop range of the single-phase water flow stage is different in different groundwater potential areas. In the northeastern and central part of the study area, the reasonable reduction range of the single-phase water flow stage is 0.018-0.024 MPa/d. In the northwest and south of the study area, the reasonable reduction of the single-phase water flow stage ranges from 0.007 to 0.017 MPa/d. The research results provide reference and guidance for the formulation of the single-phase water flow stage production system of coalbed methane wells in unproduced areas and similar geological conditions.