鄂尔多斯盆地上古生界深层煤层气资源量评价与战略意义OA

Serving as an important strategic replacement resource of unconventional natural gas in China,deep coalbed methane is still in the early stage of exploration and development evaluation overall,and faces major challenges including insufficient understanding of gas enrichment patterns,limited geological characterization of coal reservoirs,and uncertainty in resource assessment,all of which seriously hinder its large-scale development planning.Focusing on 10 deep coal seams of the Upper Paleozoic in the Ordos Basin,this paper systematically investigates their thickness and structural characteristics based on extensive drilling data.Then,a resource assessment method for deep coalbed methane is established to evaluate the total resources of deep coalbed methane in all Upper Paleozoic coal seams across the basin.In addition,the development potential,development strategy,and strategic significance of deep coalbed methane are discussed.The following results are obtained.First,the deep coal reservoirs in the study area exhibit the high-quality hydrocarbon accumulation characteristics,including low water saturation,high gas saturation,and the coexistence of free and adsorbed gas.The No.8 coal seam is the primary development target,and the No.5 coal seam is the secondary one,whereas the remaining coal seams do not yet overall meet the economic conditions for independent development.Second,the coal-seam structures of both the No.8 and No.5 coal seams are dominated by the non-interlayer type,followed by the single-interlayer type,while the multi-interlayer type is less developed.Third,the total deep coalbed methane resources of the Upper Paleozoic coal seams(No.1-No.10)at depths below 1 500 m in the Ordos Basin are estimated to be approximately 44.745×1012 m3,including 21.342×1012 m3 in the No.8 coal seam,7.712×1012 m3 in the No.5 coal seam,and 15.691×1012 m3 in the remaining 8 coal seams.Fourth,the basin has enormous potential for deep coalbed methane development.The high-quality resource areas of the No.8 coal seam are capable of supporting a long-term annual production capacity exceeding 50×109 m3/a,indicating that deep coalbed methane may become one of the most promising unconventional natural gas resources after tight sandstone gas and shale gas.In conclusion,the research findings clarify the distribution patterns and differentiated development paths of deep coalbed methane resources in the Ordos Basin,and identify the key uncertain factors for resource assessment,providing an important geological basis and technical support for the large-scale efficient development,reserve growth and production increase of deep coalbed methane in this area and for the exploration evaluation of similar basins in China.