STUDY ON HYDROCARBON GENERATION AND GAS-STORAGED CAPACITY OF DIFFERENT COALBEDS IN SAME RANK IN HUAINAN COALFIELD
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摘要: 本文从煤岩学、有机地球化学及煤的储气性原理出发,研究了淮南煤田同变质程度不同煤层煤(B11b、B10)在成烃母质、富烃特征、成烃作用和储气性等方面的差异性。B11b煤层中含有较多的似石油物质、渗出体、显微组分等的荧光浸渍现象、油滴和油膜、微粒体等,它们是煤成烃作用的直接光学标志。B11b煤层的地化参数指出较强的还原环境将有利于成烃作用。B11b煤层的孔隙性(孔容、孔径分布、孔隙结构)说明它不仅有较好的储气性能,而且还具有较有利于煤层气体运移的物性条件。而上述特征是B10煤层所不具备的。Abstract: Coalbeds B11b and B10 from the lower Shihezi formation of Permian are a pair of adjacent coalbeds at Xiejiaji coal district in Huainan Coalfield. Both coalbeds are of same rank ( Ro= 0. 80-0. 82% ) and under the same geological conditions. However, their gas-bearingness and gas-compositions are quite different. B11b is rich in coalbed gas and heavy hydrocarbon compositions, whereas B10 is poor. According to their coal petrology and organic geochemistry, the reasons on gas- bearingness and strong coal- generated hydrocarbon are studied in this paper. 1. Under optical and fluorescence microscopy, there exist many kinds of hydrocarbon-rich macerals and microindicators in coal-generated hydrocarbon in B11b, such as bituminite-filling, resinite-filling, exudatinite, suberinite, oil drops and oil film, and micrinit.es with many shapes and occurences. Some of these macerals are also the microindicators in migration of coal-generated oil and gas. 2.The information in organic geochemistry shows that both coal beds might form in different sedimentary evironments. Their OEP parameters are roughly same, i.e. they are in the same maturity. However, the parameters, such as Pr/Ph, Pr/nC17, Ph/nC18, are quite different. These parameters show that the reducibility of B11b is stronger than that of B10. The author has considered that B11b is mainly composed of herbaceous plant and hydrophyte and form in an environment of "open waters" or "swamp water land", while B10 is maed up of wood plant and form in an environment of "forest swamp". The thermal analysis shows that B11b is of higher thermal weight-loss than B10 and greater potential in coal-generated hydrocarbon. 3.The porosity and gas-storing capacity of both the coal beds has also been studied by author. The theory and experiments have indicated that the porosity in B11bis favourable for gas storage, diffusion and migration.
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