十万大山盆地下二叠统生物礁古油藏剖析及其地下隐伏礁的分布预测
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摘要
广西宁明亭亮茅口组生物礁古油藏为十万大山盆地已暴露破坏的礁古油藏之一。亭亮生物礁为大新(崇左)台地边缘发展起来的大型堤礁。礁的主要造架生物为海绵、水螅、苔藓虫及藻类等,其沉积组合具礁基、礁核、礁盖、礁间滩及礁前等亚相。该古油藏的含沥青储层主要位于礁体的上部和顶部,含沥青礁灰岩厚达98m 以上。礁储层次生溶孔的形成与分布主要受控于深埋有机溶蚀作用,同时在空间上还与礁顶部古风化壳和不整合面密切相关。烃源岩以下二叠统为主,油源丰富,上覆巨厚的中—下三叠统泥页岩为区域性盖层,为油气聚集和古油藏的形成提供了最有利的条件和场所。据地震和电法资料,在盆地东北部几十条地震测线上反映出的透镜状“礁”异常体达31个,其中较典型的有11个。这些“礁”异常体与电法剖面圈定的9个“礁”异常体均分布于同一地区并相互重叠,表明预测结果的一致性。地面露头礁与可能存在的隐伏“礁”均处于同一岩相古地理部位上,展示了该盆地在上英至太安一带可能存在一个以茅口组为主的台地边缘型隐伏礁发育带。盆地北部的礁古油藏及广泛分布的长达150km 的油气显示带提示我们要注重研究地下隐伏礁的分布及含油气性,它们有可能是十万大山盆地油气勘探的一个新领域。
A destroyed reef oil pool of Maokou Fm.located in Tingliang Ningming Guangxt is one of exposed and destroyed reef oil pools in Shiwandashan Basin.Tingliang reef is a large scale of barrier reef developed from Daxin platform margin.The main reef-building organisms are Porifera, Hydrozoa,bryazoom and algae etc.The bitumen-bearing reservoir in this destroyed oil pool lies at top and upper part of the reef.The thickness of the bitumen-bearing limestone may be over 98m.The overlying Middle-Lower Triassic shale as a resional cap rock is very thick.There are 31 Ienticular anomaly bodies(reefs),including 11 typical ones,could be recognized in decades of seismic lines taken from the northeast of the basin,which is overlapping of 9 anomaly bodies(reefs)identified in MT section.Both the outcrop reefs and possible hidden reefs lie at the same part of lithofacies paleogeography,which shows that a platform marginal hidden-reef developing zone,predominant Maokou Fm.,may occur from Shangying to Taian of the basin.The destroyed reef oil pool located in the northern part of the basin as well as oil-gas shows up to 150km long indicate that more attention has to be paid to the hidden-reef distribution and its hydrocarbon potential, which may be a new area of oil-gas exploration in the basin.
A destroyed reef oil pool of Maokou Fm.located in Tingliang Ningming Guangxt is one of exposed and destroyed reef oil pools in Shiwandashan Basin.Tingliang reef is a large scale of barrier reef developed from Daxin platform margin.The main reef-building organisms are Porifera, Hydrozoa,bryazoom and algae etc.The bitumen-bearing reservoir in this destroyed oil pool lies at top and upper part of the reef.The thickness of the bitumen-bearing limestone may be over 98m.The overlying Middle-Lower Triassic shale as a resional cap rock is very thick.There are 31 Ienticular anomaly bodies(reefs),including 11 typical ones,could be recognized in decades of seismic lines taken from the northeast of the basin,which is overlapping of 9 anomaly bodies(reefs)identified in MT section.Both the outcrop reefs and possible hidden reefs lie at the same part of lithofacies paleogeography,which shows that a platform marginal hidden-reef developing zone,predominant Maokou Fm.,may occur from Shangying to Taian of the basin.The destroyed reef oil pool located in the northern part of the basin as well as oil-gas shows up to 150km long indicate that more attention has to be paid to the hidden-reef distribution and its hydrocarbon potential, which may be a new area of oil-gas exploration in the basin.
引文
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2 王立亭等.中国南方二叠纪岩相古地理与成矿作用.地质出版社.1994
3 陈学时.江西玉山大山脚晚奥陶世层孔虫-珊瑚点礁.石油与天然气地质,1996,17(4) :326-332
4 陈学时.黔南二叠纪生物礁成岩作用特征及储集性.沉积学报,1986,4(4) :53-63
5 覃建雄译.Saller A H 等著.碳酸盐岩地层不整合面及孔隙发育.地质科学译丛,1995,12(1) :49-57
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