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中国南方主要富有机质海相页岩寒武系牛蹄塘组和志留系龙马溪组是当前页岩气勘探的重要目标地层,但演化程度普遍偏高,孔隙结构复杂。为加深对这种复杂性的认识,通过场发射扫描电镜、高压压汞实验与低温低压吸附实验(CO_2与N_2),对页岩全孔径孔隙结构特征进行对比研究。研究发现,牛蹄塘组孔体积与龙马溪组页岩的孔体积分别介于0.0202~0.0402 m L/g与0.0255~0.0310 m L/g之间,介孔在两套页岩孔体积中所占比例最大。两套页岩比表面积分别介于13.74~41.26 m~2/g与21.42~27.82 m~2/g之间,微孔与介孔几乎提供了两套页岩全部的比表面。孔隙结构的差异主要表现为牛蹄塘组页岩内溶蚀孔和粒间孔较为发育,有机质孔隙发育不均匀;而龙马溪组页岩内粒内孔、粒间孔和有机质孔隙均较为发育;牛蹄塘组在微孔范围内的孔体积与比表面积占有优势,而介孔与宏孔范围内的孔体积与比表面积均小于龙马溪组。根据实验数据结果与文献的调研,两套页岩孔隙结构差异的主要原因主要是成熟度与埋深的不同影响而形成的。
The Cambrian Niutatang Formation and Silurian Longmaxi Formation, the major organic-rich marine shale in southern China, are currently the important target stratigraphy for shale gas exploration. However, the evolutionary level is generally high and the pore structure is complex. In order to deepen the understanding of this complexity, pore-size characteristics of shales were compared by field emission scanning electron microscopy, high pressure mercury intrusion experiments and low temperature and low pressure adsorption experiments (CO_2 and N_2). It was found that the pore volume of Niutitang Formation and that of Longmaxi Formation were between 0.0202-0.0402 m L / g and 0.0255-0.0310 m L / g, respectively. The average pore volume of mesopores in the two shale pore volume The largest proportion. The specific surface area of the two sets of shale ranges from 13.74 to 41.26 m 2 / g and 21.42 to 27.82 m 2 / g, respectively. The micropores and mesopores provide almost all the specific surface area of two sets of shale. The difference of pore structure mainly shows that the pores and intergranular pores in the Niutitang shale are well developed and the pores of the organic matter are unevenly developed, while the pores, intergranular pores and organic matter pores in the Longmaxi shale are well developed. The pore volume and specific surface area of the pond group are dominant in the micropore range, while the pore volume and specific surface area in the mesopore and macropore range are smaller than that of the Longmaxi Formation. According to the investigation of experimental data and literature, the main reason for the difference in pore structure of two sets of shales is mainly due to the different effects of maturity and burial depth.