鄂尔多斯盆地东南缘上古生界煤储层非均质性及其意义

鄂尔多斯盆地东南缘陆续发现一批高产井,显示了上古生界煤层气资源勘探开发的潜力。然而,受煤储层非均质性影响,同一区块相邻井组甚至同一井组不同单井的产气效果表现出较大差异,因此深化对煤储层非均质性的认识是实现高效勘探开发的客观途径。该文从岩石学、物性、吸附性、含气性等特征方面对煤储层非均质性进行了研究,结果显示,区内3号、5号、11号煤层分布稳定,厚度较大,是煤层气勘探与开发的主要目的层;煤层以半亮煤和半暗煤为主,镜质组含量较高,具有较好的可压裂性;以低灰-中灰的瘦煤、贫煤为主,部分地段发育少量无烟煤,煤级较高;煤岩孔隙度和渗透率均较低,吸附性强,吸附时间较短且解吸率较高,有利于煤层气的产出,但需要加强煤储层改造措施研究;含气量平均在11 m~3/t以上,最高可达19.73 m~3/t,含气饱和度平均在61%以上,表明资源密度较大且具有较高的地层能量,有利于煤层气解吸产出。

Heterogeneity and Significance of Coal Reservoir of Upper Paleozoic in Southeast Margin of Ordos Basin

A number of high-yield wells has emerged in the southeast margin of Ordos Basin, which showed the potential of the UpperPaleozoic exploration and development of coalbed methane resources. However, owning to the coal reservoir heterogeneity, greatdifferences of individual gas wells were observed in adjacent block groups and sometime even in the same block. Therefore, a deeper understanding of reservoir heterogeneity is needed for efficient exploration and development. Systematic studies were conducted on coal reservoir in terms of rock characteristics, physical characteristics, adsorption characteristics, and gas characteristics. The results showed that the 3, 5, 11 coal seam, with stable distribution and large thickness, is the main target for exploration and development of coalbed methane. Half-bright coal seam and semi-dark coal with high vitrinite content has better fracture resistance, whereas a low ash-lean coal was also found, with anthracite and a small amount of high grade coal identified in some sections. We found that coal rock porosity and permeability are low, showing strong adsorption, short adsorption time and the higher desorption rate. This is conducive to CBM output, however, coal measures of reservoir stimulation need to be strengthened. The average gas content is about 11 m3/ t or more, with a maximum of 19.73 m3/ t, and the average gas saturation is above 61%, indicating a greater resource and a high density of formation energy, in favor of CBM desorption output.