Numerical Simulation Of Coalbed Methane In The Southern Block Of Shizhuang In The Southern Qinshui Basin

Shizhuang South Block located in the southern Qinshui basin, which has abundant reserves. Effective development of Shizhuang South Block is important to complete the capacity construction of Qinshui basins and ease the growing contraction between energy supplies and demands. The paper is one of the topics of major national projects, selecting typical well group to carry out numerical simulation of coalbed methane, aimed to achieve the production capacity of Shizhuang South Block.Based on the CBM desorption, diffusion and percolation mathematical model, the paper establish a Dual Porosity model in numerical simulation software, using the Langmuir adsorption isotherm and Fick's first law to describe the processes of desorption and diffusion, considering the influence of the stress sensitivity and coal matrix shrinkage on the dynamic changes of permeability, replacing the coal seam hydraulic fracture model by branch horizontal well model to realize the numerical simulation. Based on dynamic drainage law, coalbed methane wells will be divided into five drainage stages and achieve production capacity rating according to the gas production of stable gas phase, analyzing the dynamic production of different drainage characteristics of coalbed methane wells on the basis of history matching and dynamic distribution of reservoir parameters from both the horizontal direction and the vertical direction of fracture, analyzing the productivity influence factors which including the reservoir conditions, adsorption-desorption characteristics, fracturing and drainage technology, evaluating the production potential of the typical well groups and proposing reasonable advise of ECBM finally.The research results show that consider the influence of stress sensitivity and contraction of coal matrix during the coalbed recovery in the numerical models, it could reduce the capacity calculation errors of CBM in the middle and late period of gas extraction. The main causes for low yield are the pressure cannot be effectively spread, small gas desorption radius and poor drainage effect. Although it's positive relation between half-length of compression crack and production capacity of CBM, when the roof of coal seam contains aquifer, long fracturing fracture could result in too much leaky supply, Prolonged the drainage stage, void draining of the well, increase drainage difficulty, and a smaller pressure drop funnel. Also, the well spacing of the research area is too large, which need to use the local well network encryption technology; If the depletion development mode is adopted in the current well pattern, the CBM recovery would be low; Using the negative pressure gas extraction and gas injection technology could increase the recovery ratio, and it's an effective measure to increase production.