库拜煤田中低阶煤中孔-大孔发育控制因素

Control factors of mesopore-macropore development in medium-and low-rank coal in Cubey Coalfield

库拜煤田是新疆煤层气勘探的重点目标区之一。中孔、大孔为煤储层主要渗流孔隙,其发育程度是决定煤层气是否具有开发价值的重要因素。为厘清库拜煤田中低阶煤中孔-大孔发育控制因素,采集库拜煤田9口煤层气井取芯样品,开展了45次高压压汞试验、31次煤岩组分分析、32次煤岩成熟度测试以及45块取芯样品煤体结构特征描述,提取了库拜煤田中孔、大孔孔隙体积,并分析了控制其发育的地质因素。结果表明:①镜质组含量与成熟度对中孔、大孔的体积控制作用较弱;②原生结构煤、碎裂煤、碎粒煤中孔、大孔体积接近,糜棱煤中孔、大孔体积明显高出;③镜质组含量大于70%时,随镜质组含量增大,中孔和大孔结构的复杂程度趋于增大;④煤体结构对中孔结构的复杂程度影响微弱,但与大孔结构的复杂程度呈正相关关系;⑤成熟度对中孔的复杂程度控制作用较明显,对大孔的复杂程度控制作用微弱。研究成果可为库拜煤田高渗煤储层的科学评价提供理论支撑。

The Cubey Coalfield is one of the key targets for coalbed methane(CBM)exploration in Xinjiang Uygur Autonomous Region.The meso-pores and macro-pores are the main seepage channels in coal reservoir and their development degrees are key factors determi⁃ning coal reservoir development potential.In this paper,in order to clarify the factors controlling the development of mesopore and macro⁃pore in the medium and low-rank coals of the Cubey Coalfield,coal samples drilled from nine CBM wells were collected,and experiments including high-pressure mercury intrusion porosimetry tests(forty-five samples),coal maceral analyses(thirty-one samples),and matu⁃rity tests(thirty-two samples)were carried out.In addition,coal structural characteristics of forty-five samples were described.Based on the analyses above,the volumes of meso-pore and macro-pore were extracted,and the geological factors controlling their development de⁃grees were discussed.The results showed that:①the vitrinite content and maturity of coal had a weak influence on the development of me⁃so-pores and macro-pores;②the meso-pore and macro-pore volumes of primary structural coal,cataclastic coal and pulverized coal were close,while those of mylonitized coal were relatively greater;③the complexities of meso-pore and macro-pore structure tended to in⁃crease with the increased of vitrinite content when vitrinite content was greater than 70%;④the coal structure had a slight influence on the complexity of meso-pore structure,while it was positively correlated with the complexity of macro-pore structure;⑤maturity had an obvi⁃ous controlling effect on the complexity of meso-pore structure,while its effect on the structural complexity of macro-pore was weak.Re⁃sults of this study can provide theoretical support for the scientific evaluation of high permeability coal reservoir in the Cubey Coalfield.