Occurrences of the highly productive, yet complex oil and gas‐ bearing Oligocene–Miocene buried carbonate platforms of the South China Sea and adjoining onshore equivalents necessitates understanding the form, timing and pathways of hydrocarbon migration plays. Here, we report the occurrence of structural‐stratigraphic controls on relict seepage and evaluate the hydrocarbon generation and migration pathway in the exposed Subis carbonate platform. Our results show that the seepages occur essentially along a post‐depositional fault plane located along the flank of a Miocene reef. The samples (n: 3) contain 0.14–1.42% of total organic carbon (TOC). The Hydrogen Index (HI) varies between 72 and 147 Mg HC/g TOC and the Oxygen Index (OI) from 32 to 234 mg CO₂/g TOC. Similarly, the Production Index (PI) varies between 0.11 and 0.26. The source rock potentials are poor (n = 2) and good (n = 1). The studied samples show the T_max uniformly as 433°C and PI values >0.1 and are therefore thermally immature. The occurrence of seepages sampled along the eastern flank of Subis buildup falls in the autochthonous field, indicating that the hydrocarbon was produced within the indigenous formation (Subis Limestone). This indicates absence of migration from deeper and older layers. However, occurrence of this seepage along a fault plane probably reactivated immediately after lithification of the Oligocene–Miocene carbonate bioherm and affected the matrix of the rocks, suggest that the hydrocarbon generated might have moved upward along this fault plane, assimilated into the host rock, especially in the finer matrix portions of the carbonates. The presence of CO₂ at temperatures between 300–550°C is also suggestive of an organic matter origin or solution seams of the Subis Limestone and this inference obviates migration from deep‐seated faults and any connectivity and/or openness of the petroleum system between the subsurface and the atmosphere.

中文翻译：

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马来西亚渐新世-中新世苏必斯碳酸盐岩台地中的遗留烃渗漏：对页岩气刨的烃生成和运移途径以及潜在的封闭作用的影响

南海的高产而复杂的含油气的渐新世—中新世潜伏碳酸盐岩台地及其附近的陆上等价物的发生，需要了解碳氢化合物运移的形式，时间和途径。在这里，我们报告了遗留渗流的结构地层控制的发生，并评估了裸露的Subis碳酸盐台地中的碳氢化合物生成和运移途径。我们的结果表明，渗流基本上沿着中新世礁侧面的沉积后断层发生。样品（n：3）占总有机碳（TOC）的0.14–1.42％。氢指数（HI）在72至147 Mg HC / g TOC之间变化，氧指数（OI）在32至234 mg CO _{2之间变化}/ g TOC。同样，生产指数（PI）在0.11和0.26之间变化。源岩势差（n = 2），好（n = 1）。所研究的样品显示出T _max均匀地在433°C且PI值> 0.1时处于热不成熟状态。苏比斯堆积物东翼采样的渗漏属于土生土层，这表明碳氢化合物是在原生地层（苏比斯石灰岩）中产生的。这表明没有从较深层和较旧层进行迁移。但是，渐新世-中新世碳酸盐岩生物层岩化后，沿着断层平面的渗漏可能立即被重新激活，并影响了岩石的基质，这表明所产生的碳氢化合物可能已经沿着该断层平面向上移动，并被吸收到了主体岩石中，特别是在碳酸盐的较细基质部分。CO ₂的存在 在300–550°C的温度范围内，也暗示了Subis石灰岩的有机物起源或溶液接缝，该推论消除了深部断层的迁移以及地下和大气之间石油系统的任何连通性和/或开放性。