考虑气水分布的煤层气解吸模型

Desorption model considering gas-water distribution for coalbed methane reservoir

为明确煤储层基质孔隙中液相水对煤岩解吸过程的影响,从煤储层基质特征及热演化过程出发,建立简化的基质串联毛管束模型,并由此获得基质中受液相水影响的孔隙所占的比例,进而通过固—气界面Langmuir吸附理论和固—液界面理论获得不同基质含水条件下的储层解吸模型。计算结果表明液相水的存在会大幅降低煤储层的解吸能力,分析认为这是由于液相水的存在一方面通过影响固—液界面解吸所占比例影响气体解吸量;另一方面通过形成毛管力,圈闭微纳米孔隙中已解吸出的气体。研究成果为完善煤层气解吸开发理论、优化开发技术政策奠定了基础。

In order to clarify the influence of liquid in matrix pore of coal reservoir on desorption process,a capillary bundle model has been established based on matrix characteristics and coalification.From this model,the proportion of pore affected by liquid in matrix is obtained.Then,Langmuir adsorption theory of solid-gas interface and solid-liquid interface theory are used to obtain different water conditions in matrix.The result shows that the existence of liquid water will greatly reduce the desorption capacity of coal reservoir,which is attributed to the existence of liquid water.On one hand,liquid will affect the gas desorption volume by affecting the proportion of solid-liquid interface desorption;on the other hand,liquid will trap the desorbed gas in micro-nano pore by forming capillary force.The research results lay a foundation for perfecting the theory of desorption and development of coalbed methane and optimizing the policy of development technology.