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煤变质程度是控制煤储层物性的关键因素,不同煤阶煤储层孔裂隙发育特征存在较大差异。以鄂尔多斯盆地东缘山西组煤层为例,基于SEM、荧光显微观察、压汞、低温液氮吸附、低场核磁共振和X-CT扫描三维重构等实验技术手段,研究不同煤阶煤储层物性特征及变化规律,揭示煤变质程度对孔裂隙发育的控制作用规律。研究表明:随着变质程度增高,煤中植物组织孔、粒间孔等原生孔隙减少而气孔等次生孔隙增加;孔隙度呈“减小—增大—减小”的波状变化,大中孔比例先减小后趋于稳定,微小孔比例变化趋势与之相反;吸附孔孔径增大,BJH总孔体积和BET比表面积减小,孔隙结构趋于均一而孔隙表面先变粗糙后逐渐光滑;煤中裂隙先减少后增加,裂隙性质逐渐变好,裂隙排列逐渐规则化。
The degree of coal metamorphism is the key factor to control the physical property of coal reservoirs. There are big differences in the development characteristics of pore fissures in different coal rank coal reservoirs. Taking the coal seams of Shanxi Formation in the eastern margin of Ordos Basin as an example, the coal reserves of different coal rankings were studied based on SEM, fluorescence microscopy, mercury intrusion, cryogenic liquid nitrogen adsorption, low field nuclear magnetic resonance and X-ray CT three- Layer characteristics and changes in law, to reveal the degree of coal metamorphism on the development of pore fissures control law. The results showed that with the increase of the degree of metamorphism, the number of primary pores in the pores and intergranular pores of the plant tissue in coal decreased while the secondary pores such as pores increased; the porosity showed a wavy change of “decrease-increase-decrease” The proportion of mesopores decreases first and then tends to be stable, while the proportion of micropores changes with the opposite trend. The pore diameter of adsorbent increases, the total pore volume and BET specific surface area of BJH decreases, the pore structure tends to be uniform and the pore surface first becomes coarse and gradually becomes rough Smooth; the fissures in coal decrease first and then increase, the fissure properties become better gradually, and the fissure arrangement gradually regulates.