中国低煤阶煤层气地质特征_王勃

文章编号:100020747(2009)0120030205

中国低煤阶煤层气地质特征

王勃1,李景明1,张义1,2,王红岩1,刘洪林1,李贵中1,马京长1

(1.中国石油勘探开发研究院廊坊分院;2.中国石油大学(北京))

基金项目:国家重点基础研究发展规划(973)项目(2002CB211705)

摘要:低煤阶煤层气是中国煤层气勘探开发一个相当重要的潜在接替领域。中国含煤盆地的地质构造背景复杂,多数煤田经历了不同期次、不同性质构造及其组合以及应力2应变对煤储集层的改造,煤层气的富集成藏有自身的特点:厚度大、层数多、含气量低、渗透性较好、煤层气资源量和资源丰度大,厚度大而分布广泛的煤层及巨大的煤炭资源弥补了含气量小的缺点,使得低煤阶煤层气具有良好的勘探开发前景。低煤阶煤层气藏开发过程中解吸引起的基质收缩效应造成储集层渗透率增大,从而有利于低煤阶煤层气的开发,易形成工业性气流。低煤阶煤层气成藏过程简单,多为一次沉降,一次调整,如果构造、成煤环境及水文地质等主控因素能够有利匹配,有可能形成煤层气高产富集区。图1表1参18

关键词:煤层气;低煤阶;渗透性;水文;成藏过程

中图分类号:TE122.2 文献标识码:A

G eological characteristics of low rank coalbed methane,China

Wang Bo1,Li Jingming1,Zhang Yi1,2,Wang Hongyan1,Liu Honglin1,

Li Guizhong1,Ma Jingzhang1

(1.L ang f ang B ranch,Pet roChina Research I nstitute of Pet roleum Ex ploration&Development,

L ang f ang065007,China;2.China Universit y of Pet roleum,B ei j ing102249,China) Abstract:Low rank coalbed methane is a very important and potential field of coalbed methane exploration and exploitation in China.The geological structure backgrounds of coal2bearing basins are complicated,and many coalbeds are reconstructed by multi2period and multi2property structures and combinations,as well as stress2strain.The accumulation and enrichment of coalbed methane have the following characteristics:big thickness,multiple beds,low gas content,preferable permeability,great resource and abundance.The thick and widely distributed coalbeds and huge coal resources off set the shortcoming of low gas content,probably leading to the good prospect of exploration and exploitation.Matrix shrinkage effect induced by desorption causes high permeability in exploitation of low rank coalbed methane reservoirs,which is good for coalbed methane exploitation,and prone to form industrial gas flow.Low rank coalbed methane reservoirs have a simple forming process,including one deposition and one adjustment.If the main controlling factors,such as structure,coal2 forming environment and hydrologic geology,are matched well,the enriched coalbed methane zone with high production would be formed.

K ey w ords:coalbed methane;low coal rank;permeability;hydrological condition;reservoir formation

0引言

低煤阶煤层气是指赋存于褐煤(R o值小于0.50%)与长焰煤(R o值为0.50%～0.65%)及其围岩中以甲烷为主要组分的煤层气[1]。中国低煤阶煤层气资源为16×1012m3[225],约占煤层气总资源量的27.2%。随着美国、澳大利亚等国外低煤阶煤层气藏商业开发的成功和国内高煤阶煤层气勘探开发规模的逐渐形成,低煤阶煤层气成为中国煤层气勘探开发一个相当重要的潜在接替领域。但中国含煤盆地的地质构造背景要比美国复杂得多,煤层气的富集成藏有其自身的特点,而且多数煤田经历了不同期次、不同性质构造及其组合以及应力2应变对煤储集层的改造,从而造成了中国低煤阶煤层气成藏的特殊性。因此,研究低煤阶煤层气成藏条件、成藏过程及成藏的主控因素,对于指导中国低煤阶煤层气勘探开发具有重要意义。

1低煤阶煤层气特点

1.1煤层厚度大、层数多、资源量丰富

中国典型的低煤阶含煤盆地煤储集层展布具有煤层厚度大、层数多的特点,煤层最大累计厚度近200m,单煤层最大厚度逾100m,煤层层数超过50层[6]。厚

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石　油　勘　探　与　开　发

2009年2月 PETROL EUM EXPLORA TION AND DEV ELOPM EN T Vol.36　No.1