鄂尔多斯盆地东南部上古生界海陆过渡相页岩储集性与含气性

The reservoir property of the Upper Paleozoic marine-continental transitional shale and its gas-bearing capacity in the Southeastern Ordos Basin

鄂尔多斯盆地上古生界海陆过渡相页岩是重要的页岩气富集层系,但是含气性及其控制因素研究薄弱,制约了对该地区页岩气的勘探和研究。论文通过对鄂尔多斯东南部本溪和山西组大量页岩样品开展有机地球化学、矿物组成、页岩孔隙及分布的研究,评价了海陆过渡相页岩的储集性;通过含气量现场解吸和等温吸附实验,分析了页岩含气特征和影响因素。结论认为研究区海陆过渡相页岩有机质丰度高（TOC含量0.5%~11%）,主要发育III型干酪根,有机质成熟度较高（1.0%~3.0%Ro）;矿物组成以富黏土页岩为特征,黏土矿物含量可高达60%以上。总孔隙度分布在2%~8%,部分样品微裂缝发育。孔隙类型以平行板状的狭缝型孔隙介孔为主,在岩石孔隙比表面积和孔体积的贡献占90%以上;TOC含量与孔隙比表面积及孔隙总体积具有密切的相关性,有机质孔隙对岩石总孔隙构成具有重要贡献。现场解吸含气量为0.591~4.05m3/t,兰氏体积从0.05m3/t到14m3/t都有分布,页岩实测含气量与气体吸附能力差异大。TOC含量是控制海陆过渡相页岩含气量和含气能力的重要因素,富黏土矿物的吸附作用可使样品含气能力显著增加。

The Upper Paleozoic marine-continental transitional shale is important gas-rich shale in the Ordos Basin.A series of studies have been carried out on the gas generation and resource potential,but it lacks of detailed reservoir characterization and its impact on the gas content.This constrains the shale gas exploration and exploitation.A large number of shale samples were collected from the Upper Paleozoic Benxi Formation and Shanxi Formation to investigate the geochemical and mineral composition,pore type and distribution.Field canister gas desorption and isothermal adsorption experiments were performed to measure gas content and gas bearing capacity of shale samples.The results show that the Upper Paleozoic shale contains high TOC（0.5%-11%）and high thermal maturity（1.0%-3.0% Ro）,and its organic matter belongs to type III kerogen.These shale samples are characterized by high level of clay mineral（up to 60%）and low porosity（2%-8%）.Some samples are relatively microfracture-developed.The pore is dominated by meso-pore,which accounts for over 90% of all pore surface area and volume.TOC content also has close relationship to the pore surface area and volume,suggesting the organic matter pore makes significant contribution to all pore in the shale.The canister adsorption shows the gas content varies in a wide range from 0.591m3/t to 4.05m3/t,isothermal adsorption measurement shows the Langmuir gas volume ranges from 0.05m3/t to 14m3/t,both of which were seriously impacted by the TOC content.Besides,the clay mineral content might also contribute to the gas bearing capacity of shales.