Helium in China highly depends on import at present,so the most practical way to change the situation is searching for medium-to-large natural gasfields with high helium content.Therefore,the hydrocarbon accumulation ...Helium in China highly depends on import at present,so the most practical way to change the situation is searching for medium-to-large natural gasfields with high helium content.Therefore,the hydrocarbon accumulation mechanism and the helium origin of the Weiyuan high-helium natural gas reservoir have been analyzed tofind out the feasibility offinding natural gasfield with high helium content in the Presinian strata of the Sichuan Basin.Based on twelve outcrop sections and drilling data of four wells encountering the Presinian strata,the petrological features,sedimentary facies and source rocks of Presinian strata were systematically analyzed,which shows that the sedimentary formation developed in the Presinian is the Nanhua system,and the stratigraphic sequence revealed by outcrop section in the eastern margin includes the Nantuo,Datangpo,Gucheng and Liantuo Fms,and it is inferred that the same stratigraphic sequence may occur inside the basin.The Nantuo,Gucheng and Liantuo Fms are mainly glacial deposits of glutenite interbedded with mudstone;the Datangpo Fm is interglacial deposits of sandstone and shale,the lower part shale,rich in organic matter,is fairly good source rock.Further study showed that the Nantuo coarse-grained clastic reservoir,Datangpo source rock and the intruded granite“helium source rock”make up a good high-helium gas system.Controlled by the early rift,the thick Presinian sedimentary rocks occur primarily inside the rift.The distribution of sedimentary rocks and granite in the basin was predicted by use of the seismic data,which shows that the feasibility offinding high-helium gas reservoirs in Ziyang area of the Sichuan Basin is great.展开更多
Helium is an irreplaceable strategic mineral resource, and commercial helium-rich gas fields(He>0.1%) worldwide are typically discovered serendipitously during hydrocarbon exploration efforts. According to an analy...Helium is an irreplaceable strategic mineral resource, and commercial helium-rich gas fields(He>0.1%) worldwide are typically discovered serendipitously during hydrocarbon exploration efforts. According to an analysis of 75 helium-rich gas fields and 1048 natural gas samples worldwide, helium in natural gas generally exhibits “scarce”, “accompanying”, and“complex” properties, and helium-rich gas fields often occur at depths <4500 m. Helium concentrations in He-CH_(4) and He-CO_(2) gas fields are notably lower than those in He-N_(2)gas fields(He>1%). However, geological reserves in the former two types of gas fields are mainly in the range of 10^(7)–10^(11)m^(3), whereas in the latter, they are only in the range of 10^(5)–10^(7)m^(3). There are nevertheless notable disparities in the genesis and migration patterns between helium and gaseous hydrocarbons. Helium necessitates carriers(such as formation water, hydrocarbon fluids, N_(2), mantle-derived fluids, etc.) during both accumulation and long-distance migration processes, where migration conduits are not confined to sedimentary strata, and may extend to the basin's basement, lower crust, and even lithospheric mantle. However, the accumulation conditions of both helium and gaseous hydrocarbons are generally considered equivalent. The presence of gaseous hydrocarbons facilitates both the rapid exsolution of helium within helium-containing fluids and subsequent efficient aggregation in gaseous hydrocarbons, while both reduce helium diffusion and diminish escape flux. In terms of caprock, gypsum, salt, and thick shale as sealing layers contribute to the long-term preservation of helium over geological timescales. Large helium-rich gas fields, predominantly crust-derived gas fields, are primarily concentrated in uplifted zones of ancient cratonic basins and their peripheries. Based on a diagram of the He concentration versus He/N_(2) ratio, crust-derived helium fields can be categorized as basement, combined basement-sedimentary rock, and sedimentary rock helium supply types. Comprehensively given China's helium grade, helium resource endowment,natural gas industrialization process, and current helium purification processes, the foremost deployment zones for the commercial production of helium should be the helium-rich gas fields located in the Ordos, Tarim, Sichuan, and Qaidam Basins in western and central China. In addition, certain(extra) large helium-containing gas fields serve as important replacement zones.展开更多
文摘Helium in China highly depends on import at present,so the most practical way to change the situation is searching for medium-to-large natural gasfields with high helium content.Therefore,the hydrocarbon accumulation mechanism and the helium origin of the Weiyuan high-helium natural gas reservoir have been analyzed tofind out the feasibility offinding natural gasfield with high helium content in the Presinian strata of the Sichuan Basin.Based on twelve outcrop sections and drilling data of four wells encountering the Presinian strata,the petrological features,sedimentary facies and source rocks of Presinian strata were systematically analyzed,which shows that the sedimentary formation developed in the Presinian is the Nanhua system,and the stratigraphic sequence revealed by outcrop section in the eastern margin includes the Nantuo,Datangpo,Gucheng and Liantuo Fms,and it is inferred that the same stratigraphic sequence may occur inside the basin.The Nantuo,Gucheng and Liantuo Fms are mainly glacial deposits of glutenite interbedded with mudstone;the Datangpo Fm is interglacial deposits of sandstone and shale,the lower part shale,rich in organic matter,is fairly good source rock.Further study showed that the Nantuo coarse-grained clastic reservoir,Datangpo source rock and the intruded granite“helium source rock”make up a good high-helium gas system.Controlled by the early rift,the thick Presinian sedimentary rocks occur primarily inside the rift.The distribution of sedimentary rocks and granite in the basin was predicted by use of the seismic data,which shows that the feasibility offinding high-helium gas reservoirs in Ziyang area of the Sichuan Basin is great.
基金supported by the National Natural Science Foundation of China(Grant Nos.42203027,42141021,U2244209,U20B6001,42172149,and 42311530064)the China Postdoctoral Science Foundation(Grant No.2023M730039)the China National Petroleum Corporation Limited-Peking University Basic Research Program(Grant No.JTGS-2022-JS-327)。
文摘Helium is an irreplaceable strategic mineral resource, and commercial helium-rich gas fields(He>0.1%) worldwide are typically discovered serendipitously during hydrocarbon exploration efforts. According to an analysis of 75 helium-rich gas fields and 1048 natural gas samples worldwide, helium in natural gas generally exhibits “scarce”, “accompanying”, and“complex” properties, and helium-rich gas fields often occur at depths <4500 m. Helium concentrations in He-CH_(4) and He-CO_(2) gas fields are notably lower than those in He-N_(2)gas fields(He>1%). However, geological reserves in the former two types of gas fields are mainly in the range of 10^(7)–10^(11)m^(3), whereas in the latter, they are only in the range of 10^(5)–10^(7)m^(3). There are nevertheless notable disparities in the genesis and migration patterns between helium and gaseous hydrocarbons. Helium necessitates carriers(such as formation water, hydrocarbon fluids, N_(2), mantle-derived fluids, etc.) during both accumulation and long-distance migration processes, where migration conduits are not confined to sedimentary strata, and may extend to the basin's basement, lower crust, and even lithospheric mantle. However, the accumulation conditions of both helium and gaseous hydrocarbons are generally considered equivalent. The presence of gaseous hydrocarbons facilitates both the rapid exsolution of helium within helium-containing fluids and subsequent efficient aggregation in gaseous hydrocarbons, while both reduce helium diffusion and diminish escape flux. In terms of caprock, gypsum, salt, and thick shale as sealing layers contribute to the long-term preservation of helium over geological timescales. Large helium-rich gas fields, predominantly crust-derived gas fields, are primarily concentrated in uplifted zones of ancient cratonic basins and their peripheries. Based on a diagram of the He concentration versus He/N_(2) ratio, crust-derived helium fields can be categorized as basement, combined basement-sedimentary rock, and sedimentary rock helium supply types. Comprehensively given China's helium grade, helium resource endowment,natural gas industrialization process, and current helium purification processes, the foremost deployment zones for the commercial production of helium should be the helium-rich gas fields located in the Ordos, Tarim, Sichuan, and Qaidam Basins in western and central China. In addition, certain(extra) large helium-containing gas fields serve as important replacement zones.
