Qinshui Basin Coalbed Methane Well Production Prediction

Coalbed methane is an unconventional gas resources, as the world's attention on environmental protection and energy demand increases, the rapid development of coalbed methane extraction. As coal field structure in China is complex and morphological diversity, generally with the "three lows" feature, there is a unique regular of coalbed methane production, the research of coalbed methane production pattern and determine deliverability is not perfect. To resolve this problem,this paper studied the law of CBM production and production forecasting by theoretical analysis and numerical simulations,in the hope of providing advice to the development of CBM in Qinshui Basin.First, this paper analyzed the structural characteristics, deposition mechanism and transport mechanism of coal, use adsorption isotherm analyzing the three stages of coalbed methane wells production, and considering permeability changes in the process of mining coal reservoir, derived permeability change models which was effected by multiple adsorption matrix. Validation result shows that the model is accurate and reliable. Established flow balance equation of single-phase gas output and gas, water two-phase output. Utilizing flow balance equation and the flow law of diminishing can achieve real time dynamic analysis on the coalbed methane well. Then use the data of Qinshui Basin CBM wells which have been put into practice as the historical data to predict productivity, based on the best fitting parameters determine the main controlling factor of coalbed gas wells in Qinshui Basin is reservoir permeability, reservoir thickness of coal and gas contents per tons of coal. Aiming at the high rank coal, low permeability characteristics of Qinshui Basin, this paper carried out CO2 injection enhanced oil recovery simulation, the results show that injecting CO2 can significantly increase the CBM recovery rate of multi-lateral horizontal wells. Finally, proposed some appropriate technical measures to the development of Qinshui Basin CBM.