摘要
通过核磁共振(NMR)与气水两相相对渗透率实验,描述黔西比德-三塘盆地煤储层NMR T2谱与气水相渗特征,并结合压汞、最大镜质体反射率以及煤物质组成等基础测试,从煤级、显微组分、孔隙结构等角度分析主要控制因素,最后通过与沁水盆地高煤阶煤储层、美国中-低煤阶煤储层相关结论进行对比,揭示本区煤层气开发潜力.研究结果表明:本区煤储层以无烟煤为主,NMR T2谱呈双峰态分布,不可动峰明显而可动峰微弱,揭示束缚水饱和度高,有效孔隙度较低,两峰相互分离,截止值T2c为10ms,对应孔隙直径约为100nm,表明扩散孔(<100nm)和渗流孔(>100nm)之间连通性差.T2谱特征与压汞孔隙结构具有良好的匹配性,即微小孔发育、中大孔不发育,中孔比例极低,孔隙类型以半封闭孔为主,连通性较差,说明煤级控制之下的孔隙结构决定了T2谱的形态特征.气水相渗特征受控于孔隙结构、煤级、显微煤岩组分等因素,本区相渗条件总体优于沁水盆地南部,但相比于美国中-低阶煤储层,仍然表现出残余水饱和度高、残余水条件下气体相对渗透率低、气水两相流区间窄等特点,揭示本区煤层气开发面临着我国高煤阶煤储层普遍存在的解吸与渗流瓶颈问题.
Based on the nuclear magnetic resonance （NMR） and gas-water relative permeability measurements, this study described the coal reservoir NMR T2 spectrum and gas-water relative permeability characteristics as well as their indication for CBM development, and further dis- cussed their controlling factors from aspects of coal rank, coal maceral and pore structure by the methods of mercury intrusion porosimetry （MIP）, maximum vitrinite reflectance （R ） and coal petrography and quality measurements. By contrast with high rank coal reservoir of Qinshui Basin in China and medium-low rank coal reservoir of the U. S. , this study revealed the CBM development potential of the research area. The results show that. this area is domi-nated by coal rank of anthracite, and NMR T2 spectrum presents bimodal distribution; the non-movable peak is remarkable while the movable one is very weak, indicating high irreducible water saturation and low effective porosity. Two peaks are separated from each other; the T2 cutoff value is 10 m, and the corresponding core diameter is 100 nm, indicating seepage pore （~100 nm） and diffusion pore （~100 nm） have poor connectivity. Pore structure characteris- tic revealed by MIP matches well with NMR T2 spectrum, the micropore content is high while the meso-and macropores content is relatively low, especially the mesopore content is extreme- ly low and pore type is dominated by semi-closed pore with poor connectivity. The above phe- nomenon illustrates that pore structure controlled by coal rank determines NMR T2 spectrum characteristics. Gas-water relative permeability is also controlled by pore structure, as well as coal rank and coal maeeral. The gas-water relative permeability condition of the research area is superior to Southern Qinshui basin, but inferior to the U.S. medium-low rank coal reservoir, presenting higher residual water saturation, lower gas permeability under residual water satu- ration and narrow two phase flow region, revealing that the research area CBM development is faced with desorption and seepage bottleneck, which is a general problem of high rank coal res- ervoir in China.
出处
《中国矿业大学学报》
EI
CAS
CSCD
北大核心
2014年第5期841-852,共12页
Journal of China University of Mining & Technology
基金
国家自然科学基金重点项目(U13612031)
国家科技重大专项项目(2011ZX05034)
江苏省普通高校研究生科研创新计划项目(CXZZ13_09)
关键词
比德一三塘盆地
NMR
T2谱
气水相渗
孔隙结构
煤层气开发
Bide-santang basin
NMR T2 spectrum
gas-water relative permeability~ porestructure
CBM development
