0 引言
1 地质背景
表1 四川盆地长兴组—飞仙关组气层潜在烃源岩地球化学参数Table 1 Geochemical parameters of potential source rocks of the Changxing-Feixianguan formations gas reservoirs in the Sichuan Basin |
层位 | 沉积相 | 岩性 | 厚度/m | TOC/% | 有机质 类型 | 干酪根碳同位素/‰(PDB) | R O/% | 生气强度 /(108 m3/km2) | 文献来源 |
---|---|---|---|---|---|---|---|---|---|
大隆组 | 深水陆棚 | 泥岩 | 10~30 | (2.5~8.96)/4.99 | II1 | —29~—24.9 | 1.6~2.2 | 0~5 | [17-18] |
龙潭组 | 滨岸沼泽、潟湖 | 泥岩 | 40~120 | (2~4)/3.0 | III—II2 | —24~—23 | 2.0~2.6 | 20~40 | [16];本文 |
滨岸沼泽、潟湖 | 煤 | 2~20 | (41.8~81.5)/60.0 | III | —24~—23 | 2.0~2.6 | [8, 19-20];本文 | ||
吴家坪组 | 混积陆棚、开阔台地 | 灰岩 | 40~120 | (0.5~2.1)/0.9 | II1—II2 | —28~—26 | 2.2~3.1 | 20~40 | [16] |
深水陆棚 | 泥岩 | 50~120 | (0.5~5.0)/2.63 | 主要为II1,部分为I | —27.8~—26 | 2.2~3.1 | [8] | ||
茅口组 | 中缓坡—深缓坡 | 泥灰岩 | 30~220 | (0.5~3.0)/0.90 | II1 | —31~—25 | 2.1~2.7 | 10~40 | 本文 |
龙马溪组 | 深水陆棚 | 泥岩 | 100~600 | (0.5~8.9)/1.95 | I—II1 | —37~—30 | 2.4~4.4 | 20~125 | [21] |
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2 天然气地球化学特征
表2 四川盆地龙岗气田二叠系长兴组—三叠系飞仙关组天然气地球化学组成Table 2 Geochemical composition of the natural gas reservoired in the Permian Changxing Formation-Triassic Feixianguan Formation of the Longgang Gas Field, Sichuan Basin |
井号 | 层位 | 深度/m | 主要组分/% | δ13C/‰(VPDB) | δ2H /‰ (VSMOW) | 干燥 系数 | |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
CH4 | C2H6 | C3H8 | H2S | CO2 | N2 | He | H2 | CH4 | C2H6 | CO2 | CH4 | ||||
LG1 | P3 ch | 6 202~6 204 | 91.85 | 0.06 | n.d | 2.44 | 4.02 | 0.68 | n.d | n.d | -29.8 | -23 | n.d. | -125 | 0.999 3 |
LG6 | P3 ch | 5 305~5 339 | 85.23 | 0.04 | n.d | 0.09 | 11.19 | 0.4 | 0.03 | 0.02 | -28.4 | -23.4 | 1.5 | -125 | 0.999 5 |
LG39 | P3 ch | 6 459~6 490 | 89.02 | 0.08 | n.d | 4.5 | 5.2 | 1.48 | 0.01 | n.d | -29.8 | -24.2 | 0.6 | -130 | 0.999 1 |
LG63 | P3 ch | 6 988.1~7 045 | 81.02 | 0.04 | 0.01 | 2.78 | 14.35 | 0.45 | 0.02 | 0.1 | -29.9 | -25.6 | 0.7 | -124 | 0.999 4 |
LG62 | T1 f | 6 220~6 285 | 84.25 | 0.05 | 0.01 | 1.98 | 10.1 | 1.23 | 0.01 | 0.01 | -28 | -22.5 | 2.1 | -130 | 0.999 3 |
LG001-11 | T1 f | 5 946.7~6 088 | 95.32 | 0.07 | 0.01 | 1.65 | 2.5 | 0.65 | n.d | n.d | -28.9 | -23.4 | 1.5 | -131 | 0.999 2 |
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2.1 天然气组分
图3 川东北地区石炭系—三叠系烷烃气甲烷碳同位素—干燥系数以及甲烷—乙烷碳同位素相关图((a)δ13C1vs. 干燥系数;(b)δ13C1vs.δ13C2;川东北石炭系—三叠系数据来源于文献[2,4,7,10,23-24]及本文;萨拉门托盆地据文献[25];尼日尔三角洲和特拉华/范弗德盆地据文献[26])Fig.3 Correlation diagram of methane carbon isotopes with drying coefficient,and methane-ethane carbon isotopes of Carboniferous-Triassic in northeastern Sichuan Basin((a)δ13C1 vs. drying coefficient;(b)δ13C1 vs. δ13C2 data of the Carboniferous-Triassic of northeastern Sichuan Basin from Refs.[2,4,7,10,23,24] and this paper; Sacramento Basin from Ref.[25]; Niger delta and Delaware/Val Verde Basin from Ref.[26]) |
2.2 烷烃气和二氧化碳碳同位素
2.3 甲烷氢同位素
图4 川东北地区二叠系—三叠系甲烷氢同位素vs.C1/(C2+C3)对比(底图据文献[31];川东北二叠系—三叠系数据来源于文献[4,7,10,23]及本文;鄂尔多斯盆地C—P数据来源于文献[22,32-33];四川盆地西部T3 x数据来源于文献[4,22])Fig.4 Plot of hydrogen isotopes of methane vs. C1/(C2+C3) of the Permian- Triassic gases in the eastern Sichuan basin (diagram after Ref.[31]; data of the Carboniferous- Triassic of northeaster Sichuan Basin from Refs.[4,7,10,23] and this paper; data of the C-P strata in the Ordos basin fromRefs.[22,32-33]; data of the T3 x in the western Sichuan Basin from Refs.[4,22]) |