Distribution and gas-bearing properties of Permian igneous rocks in Sichuan Basin, SW China
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摘要
Based on the analysis of outcrop, seismic, logging and drilling data, combined with exploration practice, the characteristics,distribution, reservoir performance and gas-bearing properties of Permian igneous rocks in Sichuan Basin are studied. The study shows that central volcanic eruptive facies are developed in Sichuan Basin, and their lithological assemblages and distribution characteristics show obvious differences. The igneous rocks are mainly distributed in three regions: the southwestern part of the basin has dominantly largescale overflow facies basalts; the central and western part of the basin, Jianyang-Santai area, develop intrusive rocks, volcanic lavas(basalts)and pyroclastic rocks; and the eastern part of Sichuan, Dazhou-Liangping area, only develop diabase and basalts. Five aspects of understandings are achieved:(1) The Upper Permian igneous rocks can be divided into intrusive rocks and extrusive rocks, with the extrusive rocks as the main body. The chemical compositions of the extrusive rocks are characterized by both alkaline basalt and tholeiitic basalt, and belong to the subalkaline type of transitional basalt magma eruption.(2) There are obvious rhythmic structures vertically among overflow facies basalt, and the single rhythmic layer consists of, from bottom up, pyroclastic rocks(undeveloped), gray and dark gray porphyritic basalts(unstable), dark gray and purple microcrystalline-cryptocrystalline basalts, dark greyish green porous and amygdaloid basalts; the central volcanic eruption shows the rhythm and the vertical sequence of volcanic clastic rocks(agglomerates and breccias), volcanic lava, tuffaceous lava from bottom to top.(3) The pore types of basalt and pyroclastic rocks are diverse, mainly dissolution pore and de-vitrification micropore, but their physical properties are different. Basalt is characterized by ultra-low pore permeability, small reservoir thickness, and reservoirs are distributed in the upper and middle parts of the cycle, with poor lateral comparability. Volcanic clastic rocks are medium to high porous reservoirs(Well YT1: porosity: 8.66%?16.48%, average 13.76%) with large thickness and good reservoir quality.(4) Natural gas in basalts in southwestern basin mainly comes from Middle Permian, and natural gas in volcanic clastic rocks in central and western basin comes from Cambrian Qiongzhusi Formation.(5) Analysis of igneous reservoir-forming conditions in different areas shows that there are relatively insufficient gas sources and great differences in preservation conditions in southwestern basin.Reservoirs are poorly developed and gas-bearing is complex. The Jianyang-Santai area in the central and western part of Sichuan Basin has abundant hydrocarbon sources, developed reservoir, favorable preservation conditions and favorable gas geological conditions, and it is a favorable area for gas exploration.
Based on the analysis of outcrop, seismic, logging and drilling data, combined with exploration practice, the characteristics,distribution, reservoir performance and gas-bearing properties of Permian igneous rocks in Sichuan Basin are studied. The study shows that central volcanic eruptive facies are developed in Sichuan Basin, and their lithological assemblages and distribution characteristics show obvious differences. The igneous rocks are mainly distributed in three regions: the southwestern part of the basin has dominantly largescale overflow facies basalts; the central and western part of the basin, Jianyang-Santai area, develop intrusive rocks, volcanic lavas(basalts)and pyroclastic rocks; and the eastern part of Sichuan, Dazhou-Liangping area, only develop diabase and basalts. Five aspects of understandings are achieved:(1) The Upper Permian igneous rocks can be divided into intrusive rocks and extrusive rocks, with the extrusive rocks as the main body. The chemical compositions of the extrusive rocks are characterized by both alkaline basalt and tholeiitic basalt, and belong to the subalkaline type of transitional basalt magma eruption.(2) There are obvious rhythmic structures vertically among overflow facies basalt, and the single rhythmic layer consists of, from bottom up, pyroclastic rocks(undeveloped), gray and dark gray porphyritic basalts(unstable), dark gray and purple microcrystalline-cryptocrystalline basalts, dark greyish green porous and amygdaloid basalts; the central volcanic eruption shows the rhythm and the vertical sequence of volcanic clastic rocks(agglomerates and breccias), volcanic lava, tuffaceous lava from bottom to top.(3) The pore types of basalt and pyroclastic rocks are diverse, mainly dissolution pore and de-vitrification micropore, but their physical properties are different. Basalt is characterized by ultra-low pore permeability, small reservoir thickness, and reservoirs are distributed in the upper and middle parts of the cycle, with poor lateral comparability. Volcanic clastic rocks are medium to high porous reservoirs(Well YT1: porosity: 8.66%?16.48%, average 13.76%) with large thickness and good reservoir quality.(4) Natural gas in basalts in southwestern basin mainly comes from Middle Permian, and natural gas in volcanic clastic rocks in central and western basin comes from Cambrian Qiongzhusi Formation.(5) Analysis of igneous reservoir-forming conditions in different areas shows that there are relatively insufficient gas sources and great differences in preservation conditions in southwestern basin.Reservoirs are poorly developed and gas-bearing is complex. The Jianyang-Santai area in the central and western part of Sichuan Basin has abundant hydrocarbon sources, developed reservoir, favorable preservation conditions and favorable gas geological conditions, and it is a favorable area for gas exploration.
Based on the analysis of outcrop, seismic, logging and drilling data, combined with exploration practice, the characteristics,distribution, reservoir performance and gas-bearing properties of Permian igneous rocks in Sichuan Basin are studied. The study shows that central volcanic eruptive facies are developed in Sichuan Basin, and their lithological assemblages and distribution characteristics show obvious differences. The igneous rocks are mainly distributed in three regions: the southwestern part of the basin has dominantly largescale overflow facies basalts; the central and western part of the basin, Jianyang-Santai area, develop intrusive rocks, volcanic lavas(basalts)and pyroclastic rocks; and the eastern part of Sichuan, Dazhou-Liangping area, only develop diabase and basalts. Five aspects of understandings are achieved:(1) The Upper Permian igneous rocks can be divided into intrusive rocks and extrusive rocks, with the extrusive rocks as the main body. The chemical compositions of the extrusive rocks are characterized by both alkaline basalt and tholeiitic basalt, and belong to the subalkaline type of transitional basalt magma eruption.(2) There are obvious rhythmic structures vertically among overflow facies basalt, and the single rhythmic layer consists of, from bottom up, pyroclastic rocks(undeveloped), gray and dark gray porphyritic basalts(unstable), dark gray and purple microcrystalline-cryptocrystalline basalts, dark greyish green porous and amygdaloid basalts; the central volcanic eruption shows the rhythm and the vertical sequence of volcanic clastic rocks(agglomerates and breccias), volcanic lava, tuffaceous lava from bottom to top.(3) The pore types of basalt and pyroclastic rocks are diverse, mainly dissolution pore and de-vitrification micropore, but their physical properties are different. Basalt is characterized by ultra-low pore permeability, small reservoir thickness, and reservoirs are distributed in the upper and middle parts of the cycle, with poor lateral comparability. Volcanic clastic rocks are medium to high porous reservoirs(Well YT1: porosity: 8.66%?16.48%, average 13.76%) with large thickness and good reservoir quality.(4) Natural gas in basalts in southwestern basin mainly comes from Middle Permian, and natural gas in volcanic clastic rocks in central and western basin comes from Cambrian Qiongzhusi Formation.(5) Analysis of igneous reservoir-forming conditions in different areas shows that there are relatively insufficient gas sources and great differences in preservation conditions in southwestern basin.Reservoirs are poorly developed and gas-bearing is complex. The Jianyang-Santai area in the central and western part of Sichuan Basin has abundant hydrocarbon sources, developed reservoir, favorable preservation conditions and favorable gas geological conditions, and it is a favorable area for gas exploration.
引文
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[4]HUANG Yong,HAO Jiaxu,DENG Guibiao,et al.The discovery of terrestrial extrusive basalt of Permian Woniusi Formation in Shidian area,western Yunnan Province.Geological Bulletin of China,2012,31(2):314-320.
[5]XUAN Li,LI Jun.Geological characteristics of Emei Mountain basalt in the border of Yunnan and Guizhou province and its relationship with copper mineralization.West-China Exploration Engineering,2014,26(1):156-160.
[6]LI Qi.The characteristic and genesis of mineral assemblages in the amygdaloidal structure in basalt of Sichuan and Yunnan province.Guilin:Guilin University of Technology,2015.
[7]XIAO Long,XU Yigang,MEI Houjun,et al.Geochemistry of Emeishan flood basalts at Binchuan Area,SW China:Rock types and temporal evolution.Scientia Geologica Sinica2003,38(4):478-494.
[8]CAO Changlei,MEI Hongbo,HU Guangdao,et al.Division and implications of Emeishan basalt volcanic cycles in Guanting of Jianshui in Yunnan.Journal of Geology,2014,38(3):352-358.
[9]PAN Xingnan,ZHAO Jixiang,ZHANG Xuanyang,et al.Tectonics and rifting in Kangdian region.Chongqing:Chongqing Publishing Group,1987.
[10]MA Yongsheng,CHEN Hongde,WANG Guoli,et al.Sequence stratigraphy and paleogeography of southern China.Beijing:China Science Publishing and Media Ltd,2009.
[11]ZHANG Ruoxiang,WANG Xingzhi,LAN Daqiao,et al.Reservoir evaluation of Emeishan basalts in Southwest Sichuan.Natural Gas Exploration and Development,2006,29(1):17-20.
[12]HE Songlin.Basalt reservoir characteristics and gas source analysis:Taking the Upper Permian Emeishan basalt in southwest Sichuan Basin as an example.Nonferrous Metals Abstract,2016,31(1):1-5.
[13]DU Jinhu,WANG Zecheng,ZOU Caineng.Discovery of intra-cratonic rift in the Upper Yangtze and its coutrol effect on the formation of Anyue giant gas field.Acta Petrolei Sinica,2016,37(1):1-16.
[2]LUO Zhili.A discussion of taphrogenesis and hydrocarbon distribution in China.Bulletin of the Chinese Academy of Geological Sciences,1984,6(3):99-107.
[3]SHEN Junhui,WANG Lansheng,XU Linsheng,et al.The lithofacies and the rock mass structure of Emei Mountain basalt rock mass.Hydrogeology and Engineering Geology,2001,28(6):1-4.
[4]HUANG Yong,HAO Jiaxu,DENG Guibiao,et al.The discovery of terrestrial extrusive basalt of Permian Woniusi Formation in Shidian area,western Yunnan Province.Geological Bulletin of China,2012,31(2):314-320.
[5]XUAN Li,LI Jun.Geological characteristics of Emei Mountain basalt in the border of Yunnan and Guizhou province and its relationship with copper mineralization.West-China Exploration Engineering,2014,26(1):156-160.
[6]LI Qi.The characteristic and genesis of mineral assemblages in the amygdaloidal structure in basalt of Sichuan and Yunnan province.Guilin:Guilin University of Technology,2015.
[7]XIAO Long,XU Yigang,MEI Houjun,et al.Geochemistry of Emeishan flood basalts at Binchuan Area,SW China:Rock types and temporal evolution.Scientia Geologica Sinica2003,38(4):478-494.
[8]CAO Changlei,MEI Hongbo,HU Guangdao,et al.Division and implications of Emeishan basalt volcanic cycles in Guanting of Jianshui in Yunnan.Journal of Geology,2014,38(3):352-358.
[9]PAN Xingnan,ZHAO Jixiang,ZHANG Xuanyang,et al.Tectonics and rifting in Kangdian region.Chongqing:Chongqing Publishing Group,1987.
[10]MA Yongsheng,CHEN Hongde,WANG Guoli,et al.Sequence stratigraphy and paleogeography of southern China.Beijing:China Science Publishing and Media Ltd,2009.
[11]ZHANG Ruoxiang,WANG Xingzhi,LAN Daqiao,et al.Reservoir evaluation of Emeishan basalts in Southwest Sichuan.Natural Gas Exploration and Development,2006,29(1):17-20.
[12]HE Songlin.Basalt reservoir characteristics and gas source analysis:Taking the Upper Permian Emeishan basalt in southwest Sichuan Basin as an example.Nonferrous Metals Abstract,2016,31(1):1-5.
[13]DU Jinhu,WANG Zecheng,ZOU Caineng.Discovery of intra-cratonic rift in the Upper Yangtze and its coutrol effect on the formation of Anyue giant gas field.Acta Petrolei Sinica,2016,37(1):1-16.
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