摘要
煤层气主要以吸附状态在承压水作用下赋存在煤基质孔隙中,排水降压是其主要开采方式。煤层气藏和低渗透天然气藏相比,其初始含水饱和度往往较高。在开发过程中气水两相始终同时存在,即使是在开发的第3阶段,产水量很小,但水相饱和度还是较高。地层水的存在使得多孔介质通道狭窄,造成低渗含水气藏毛管压力普遍很高,严重影响气体的渗透率。通过对沁水盆地部分煤岩样品渗流特征的研究,将排采曲线归纳为上凸型、下凹型和复合型3种代表类型。分析结果表明,含水饱和度越大,启动压力梯度越大。这些认识对于正确制订排采工作制度、提高排采效果具有重要意义。
Coalbed methane（CBM） exists in pores of coal matrix mainly in adsorption state under an artesian condition,it can not be exploited until draining water and dropping pressure.Compared with low-permeability natural gas reservoirs,coalbed methane reservoirs usually have a higher level of the initial water saturation.During gas exploitation,two phases of gas and water always co-exist even at the third stage of exploitation,in which the aqueous saturation still maintains a higher level though the water production rate is very low.The presence of formation water usually makes porous channels narrow,resulting in the capillary pressure of low-permeability water-bearing gas reservoirs universally high,which can significantly affect gas permeability.The present paper investigated seepage characteristics of some coal rocks sampled from the Qinshui Basin and categorized curves of the water drainage and gas exploitation into three representative types,namely upward-protruding,downward-concaving and composite types.It was found that the higher the aqueous saturation,the greater the gradient of the start-up pressure,which is of great significance not only in making a proper procedure of the water drainage and gas exploitation but also in improving effects of water drainage and gas production.
出处
《石油学报》
EI
CAS
CSCD
北大核心
2011年第3期500-503,共4页
Acta Petrolei Sinica
基金
国家科技重大专项(2008ZX05018)资助
关键词
沁水盆地
煤层气
渗流特征
扩散
临界压力
Qinshui Basin
coalbed methane
seepage characteristics
diffusion
critical pressure
