The structural evolution of the middle section of the West Sichuan Depression in the Sichuan Basin controlled the hydrocarbon accumulation in the Middle Triassic Leikoupo Formation
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摘要: 中三叠统雷口坡组在四川盆地川西坳陷中段的金马—鸭子河构造提交探明储量千亿立方米,新场、马井地区同样也获得了工业气流并提交控制、预测储量,但区内构造演化过程及油气成藏配置关系还不明确。通过对周缘露头、盆地内钻井样品的镜质体反射率、扫描电镜及流体包裹体等分析,并结合构造解释,明确了川西坳陷中段的局部构造最早形成于印支早期,对雷口坡组油气成藏起关键作用的构造演化时期为早—中侏罗世;通源断层或“接力式”断层输导系统可作为良好的天然气运移通道,有利于油气富集成藏;局部古构造高点以及储层、输导系统等关键成藏要素配置关系良好且后期构造形变破坏弱的地区为最有利勘探区。Abstract: The Middle Triassic Leikoupo Formation of Jinma-Yazihe structure in the middle section of Western Sichuan Depression has submitted over 100 billion cubic meters of proved natural gas reserves. An industrial gas flow has also been obtained in Xinchang and Majing area, and the controlled and predicted reserves have been submitted. However, the relationship between structural evolution process and hydrocarbon accumulation configuration is still unclear. Through the analysis of vitrinite reflectance, scanning electron microscopic observation, analysis of fluid inclusion of peripheral outcrop and drilling samples, and combined with structural interpretation, the following results have been indicated. It is clear that the local structure in the middle section of Western Sichuan Depression was formed in the early Indosinian, and the Early-Middle Jurassic was a critical tectonic evolution period for hydrocarbon accumulation in the Leikoupo Formation. Meanwhile, the faults connected to sources or "contact" fault migration system provided pathways for natural gas migration, which was conducive for hydrocarbon enrichment. The local paleo-structural high points with a good configuration of key accumulation factors such as reservoirs and transport systems and weak structural deformation are the most favorable exploration area.
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图 2 龙门山前金马—鸭子河构造地震剖面
剖面位置见图 1。
Figure 2. Seismic profile of Jinma-Yazihe structure in Longmen Mountain front, western Sichuan Basin
图 3 四川盆地川西坳陷新场构造地震剖面
剖面位置见图 1。
Figure 3. Seismic profile of Xinchang structure, Western Sichuan Depression, Sichuan Basin
图 4 四川盆地川西坳陷马井构造地震剖面
剖面位置见图 1。
Figure 4. Seismic profile of Majin structure, Western Sichuan Depression, Sichuan Basin
表 1 川西地区二叠系露头样品镜质体反射率Ro测试数据统计
Table 1. Ro test data of Permian outcrop samples, western Sichuan
样品编号 岩性 剖面位置 层位 Ro/% Rb/%1) 测点数量 自然演化序列Ro/%2) M12 灰岩 上寺 P2m 0.86 32 0.90 JP30 灰岩 江油—平武 P2m 0.58 22 0.72 SD30 灰岩 什邡—金河 P2m 0.85 26 0.90 SD31 灰岩 什邡—金河 P2m 0.79 14 0.86 BP-23 灰岩 宝兴—大邑 P2m 5.35 31 3.85 BP-34 灰岩 宝兴—大邑 P2m 4.73 26 3.44 DP-12 灰岩 宝兴—大邑 P2m 2.10 14 1.72 JP27 泥岩 江油—平武 P2m 0.46 21 0.64 JP33 生物泥灰岩 江油—平武 P2m 0.54 26 0.69 JP34 生物泥灰岩 江油—平武 P2m 0.85 4 0.85 JP35 生物泥灰岩 江油—平武 P2m 0.57 11 0.71 M10 灰岩 上寺 P2q 0.75 21 0.83 DP3 灰岩 宝兴—大邑 P2q 2.27 23 1.83 DP-8 灰岩 宝兴—大邑 P2q 2.10 20 1.72 BP-13 灰岩 宝兴—大邑 P2q 5.04 18 3.65 JP15 泥灰岩 江油—平武 P2q 0.67 50 0.78 SP-D20 生物灰岩 什邡—金河 P2q 0.98 13 0.98 JJP2 碳质泥灰岩 江油—平武 P2q 0.51 23 0.67 JJP1 碳质页岩 江油—平武 P2q 0.70 16 0.70 TK-8 深灰色白云质灰岩 北川—通口 P2q 0.76 16 0.84 TK-11 灰黑色灰岩 北川—通口 P2q 0.84 23 0.89 TCX-3 灰黑色碳质泥岩 天池乡 P3l 0.79 17 0.85 SD50+1 灰岩 什邡—金河 P3l 0.95 31 0.96 SD74 灰岩 什邡—金河 P3l 0.87 50 0.91 DP-24 灰岩 宝兴—大邑 P3l 1.79 13 1.79 M5 煤 上寺 P3l 0.65 50 0.77 M14 泥灰岩 上寺 P3l 0.69 50 0.79 JP46 泥岩 江油—平武 P3l 0.80 15 0.86 JP51 生物灰岩 江油—平武 P3l 0.58 17 0.72 SD73 生物灰岩 什邡—金河 P3l 0.87 50 0.91 BP-42 碳质灰岩 宝兴—大邑 P3l 5.07 15 3.67 BP-44 碳质灰岩 宝兴—大邑 P3l 5.16 15 3.72 M6 碳质泥岩 上寺 P3l 0.66 50 0.66 SD60 碳质页岩 什邡—金河 P3l 1.01 50 1.01 SD61 碳质页岩 什邡—金河 P3l 1.11 50 1.11 1)Rb为沥青反射率;2) 自然演化序列Ro=0.656 9Rb+0.336 4,计算公式参考丰国秀等[11]。 -
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