Prediction Of Multi-layer Commingled Production Of Coalbed Methane Wells

Due to the influence of sedimentary and structural factors,the coal seam presents the characteristics of multi-layer and small thickness.The coal seam is usually buried shallow,and the shallow layer is prone to gas escape,which leads to the decrease of pressure and the difference of pressure between layers.There will have gas and water two phase flow during commingled production process which will cause the layers have different pressure in the wellbore due to the water level height.The existing commercial software without fully considering the stress differences between layers,commingling production forecasting has a big problem.This paper introduces the geological characteristics and development history of the B CBM field,studies the current status of commingled production in the gas field,and analyses and researches the scope of the whole gas field for the commingled production effect,the number of layers for the single well,the drop and the velocity reduction of the wellbore water level.This paper studies the mechanism of CBM reservoir and migration and analyzes the mechanism of multi-layer combined production.In order to solve the problem of inaccurate characterization of commingled open-layer pressures,a multi-layer coalbed methane production capacity model using dynamic surface data and considering stratified pressure was established,and the method for obtaining parameters in the model was described in detail.And with the help of Python computer language,a detailed calculation process was designed to solve the complex problem of solving the model.Comparing with the existing commercial software Eclipse、FAST,the reliability of the multi-layer combined production capacity model was verified through a single-layer case;the degree of influence of the liquid surface declining speed on the production capacity was investigated through multi-layer cases,and the multi-layer combined production capacity was demonstrated.Model accuracy,superiority.On this basis,the multi-layer commingled production capacity model was applied to the historical fitting of two typical commingled wells in B gas field.The production capacity was forecasted for the three new wells,and the development indicators for each layer of individual wells were obtained to facilitate the system evaluation and provide some guidance or advice on the production of coal seam gas wells.