Study On Prediction Model For The Capacity To The Undermine Coalbed-gas Drainage Production

The coalbed-gas drainagement is not only the fundamental safety measure for the coalmine gas management, but also the important style of coalbed-gas development. In 2007, the amounts of coalbed gas drainaged from undermines has reached 4.4×10¹⁰m³, but the gas development is not stable and large-scale industry chain. It depends on the stability of the gas production. So the coal and coalbed gas resource reserved is very important. In china, though the coal and coalbed gas resource is abundant, the prediction before the coal development should be determinated ahead.1)How much gas deserved in the coal in the certain time.2)How many borehole, drainagement time and the way of the borehole layout is decided with the national gas drainagement standard.The problem above is solved in the gas development capacity prediction. It is helpful to coalbed gas ordered development in the certain area and the base of the gas development and benefits on the borehole layout, enhance the effect of gas drainagement, shorten the drainaging time and protect the coal mine safety.The theory of coalbed gas flow has much developed, many of scholar have researched in this field, but rarely in the coalbed gas development capacity prediction.1)Much research in single borehole drainagement prediction, little in mul-borehole drainagement prediction.2)The classical coalbed drainagement model is fund on the unchanged permeability, but in fact, the permeability is variable with the gas drainaging, so it is not satisfied the practical drainagement.3)Much research on the factors of range of the gas drainagement, but there is not a metrizable way to measure the law in the drainaging process.In this article, to solve the problem in the coalbed gas development, on the basis of Darcy law, the gas production prediction model with the permeability changing on the process of the drainaging, and the numerical simulation is adopted to predict the coalbed gas production with mul-borehole in the coal seam.The major work and conclusion in the article as follow:1)Set up the model of drainage radius and permeability rate variation law in the process of gas drainagment;2)On the basis of the Darcy Law, the model of gas flow is set up and to be applied;3)The numerical simulation analyzer is built for undermine gas producting;4)The prediction which is the capacity of the multi-drainage borehole is completed.