注气驱替煤层气数值模拟研究

Research on Numerical Simulation of Enhanced Coalbed Methane Recovery by Injecting Gas

注气增产法是一种新兴的提高甲烷抽放率和单井产量的增产技术,其原理是注入的气体与甲烷竞争吸附和降低甲烷有效分压,使甲烷解吸。其优点是保证煤层的能量,有利于甲烷产出,可大幅度提高煤层气的产量和采收率,延长煤层气田的开采期,提高经济效益,加速成本回收。通过研究注气增产法的机理,考虑了气组分和流体组分出现和消失的可能性,建立了注气驱替煤层气的完整的三维拟稳态非平衡吸附数学模型和数值模型,并根据所建立的模型开发了注气驱替煤层气的计算机程序。实例证明,该模型是可靠的,可为注气增产技术在我国煤层气开采中的推广应用起到指导作用。

Enhanced coalbed methane recovery by injecting gas is a new technology of enhanced coalbed methane recovery. The theory of the technology is that injected gas competes with methane for sorption, decreases effective partial pressure of methane, and then methane desorbs. The technology helps to sustain coalbed energy, increase coalbed methane production and recovery, prolong production time, effectively increase coalbed methane reserves and benefit, and quicken return on investment. Through studying the mechanism of exploiting coalbed methane by injecting gas, the mathematical model and numerical model of integrated 3D quasi steady state non-equilibrium sorption are built in this paper. The possibility of gas composition and water composition appearance and disappearance is considered. According to the built model, computer program of exploiting coalbed methane by injecting gas is developed. With the computer program, the built model is proved to be credible by example. This is useful for the technology spread in China and coalbed methane recovery.