| Most single wells in Qinshui Basin have entered the stable production period.With the continuous exploitation of single wells,some wells have gradually entered the decline period.Due to the coal mining in the coal-bed methane development area,with the continuous development of coal mining,the influence of coal mining on coalbed methane wells is further deepened,and the gas volume will be greatly reduced.In view of this problem,this paper selects Fanzhuang block of coalbed methane field in the south of Qinshui Basin as the research object,adopts two methods of negative pressure pumping and micro positive pressure to carry out field test research on coalbed methane well in Fanzhuang block,and analyzes the applicability of depressurization pumping technology from two aspects of equipment and geology(1)The pressure expansion in coal reservoir propagates to the distance in the form of pressure drop funnel.By reducing the bottom hole flow pressure,the pressure drop propagation range can be increased.After coal mining,the permeability of coal seam will be greatly improved,so that the development of coalbed methane is easy to form high yield.However,if it is too close to the mining area,the surface coalbed methane well will appear the phenomenon of back suction,which may cause the decline of gas production.(2)The geological adaptability of depressurization and drainage technology is clear,which is most suitable for the wells in 100-150 m,gentle structure area,high gas content and good permeability area within the influence range of coal mine;for the non coal mine affected wells affected by too high system pipe pressure,the operation parameters need to be optimized according to the actual situation;for some wells in the area with high recovery degree(recovery degree > 70%),the applicability is poor.(3)The equipment adaptability of depressurization pumping and drainage technology is evaluated.The water ring pumping and drainage pump has some technological problems,such as large vibration and poor mechanical seal.The next step is to optimize the mechanical vibration,reduce the damage caused by vibration to the components,enhance the sealing of the equipment at high temperature,and improve the drainage stability of the equipment.The research results of this paper have important guiding significance for improving the gas production of coalbed methane wells in the areas affected by coal mining.It reveals the transmission law of pressure in coal reservoir and the influence of coal mining on the pressure transmission law.It analyzes the geological and equipment adaptability of depressurization and drainage technology,and forms an innovative depressurization and drainage method for coal mine affected wells. |
