Petroleum systems of the oldest gas field in China: Neoproterozoic gas pools in the Weiyuan gas field, Sichuan Basin
Petroleum systems of the oldest gas field in China: Neoproterozoic gas pools in the Weiyuan gas field, Sichuan Basin
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DOI：
10.1016/j.marpetgeo.2008.01.009
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发表时间：
2008-04
影响因子：
4.2
通讯作者：
G. Wei;Ge Chen;Shangming Du;Lin Zhang;Wei Yang
中科院分区：
文献类型：
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作者：
G. Wei;Ge Chen;Shangming Du;Lin Zhang;Wei Yang
威远气田是中国最古老的气田，是新元古代巨型气藏的罕见范例。该气田位于四川盆地西南部，震旦系灯影组储层已探明天然气储量约400亿立方米(Bcm)或1.41万亿立方英尺(Tcf)。该气田目前已接近枯竭，累计产气量为144亿立方米，采收率约为36%。新元古代气藏与下二叠统茅口组气藏在地理上也有重叠，另有探明天然气储量约0.861亿立方米或30.2bcf。震旦系气藏天然气中氮、CO_2、H_2S、氦、Ar相对丰富，气态烷烃表现为δ~(13)C_1；δ~(13)C2和δ~(13)C_1&l；−~(31)‰。这些天然气可能来源于上覆下寒武统九老洞组页岩中有机质的热裂解。在灯影油气藏中发现了三种类型的固体沥青和油气流体包裹体，反映了加里东期、海西期-印支期、燕山期和喜马拉雅期的早期油气充注、早期天然气充注、晚期天然气充注和天然气再分配阶段的多重油气运聚作用。最近对已建立的气藏上方寒武系层位的勘探，导致在玉仙寺组和西相池组发现了大量天然气，从而延长了这一成熟气田的生产寿命。
Weiyuan, the oldest gas field in China, is a rare example of the giant Neoproterozoic gas pools. This field is located in southwestern Sichuan Basin, with a proven in place gas reserve around 40 billion cubic meters (bcm) or 1.41 trillion cubic feet (tcf) in reservoirs of the Sinian Dengying Formation. This field is almost depleted now, with a cumulative gas production of 14.4bcm and a recovery factor of around 36%. The Neoproterozoic gas pools are also geographically overlapped by gas pools in the Lower Permian Maokou Formation, with an additional proven in place gas reserve about 0.861bcm or 30.2bcf. Gases in the Sinian reservoirs are relatively rich in nitrogen, CO2, H2S, helium and argon, with gaseous alkanes showing δl3C1<δ13C2and δl3C1< −31‰. These gases were likely derived from thermal cracking of organic matter in shales of the overlying Lower Cambrian Jiulaodong Formation. Three types of solid bitumens and hydrocarbon fluid inclusions have been identified in the Dengying reservoirs, suggesting multiple petroleum migration and accumulation events, including an early oil charge, an early gas charge, a late gas charge and a gas redistribution phase during the Caledonian, Hercynian-Indosinian, Yanshanian and Himalayan orogenies, respectively. Recent exploration of the Cambrian horizons above the established gas pools has led to significant gas discoveries in the Yuxiansi and Xixiangchi formations, thus extending the production life of this mature field.