广西十万大山盆地下二叠统生物礁古油藏及隐伏礁预测

Reef Palaeopool and Prediction of Buried Reefs in the Lower Permian Series from Shiwandashan Basin of Guangxi Province

广西宁明县亭亮下二叠统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。该古油藏的含沥青储层主要分布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。论文深入探讨了礁古油藏形成的主要成岩作用类型及其埋藏-构造发展史、有机质演化史及成岩孔隙演化史三者的配置关系和成藏机理。另据地震和电法资料,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。地面露头礁的分布与可能存在的隐伏“礁”均处于同一个岩相古地理部位上,展示了该盆地上英至太安一带有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150 km的油气显示带,提示我们要十分注重研究地下隐伏礁的分布及含油气性,它有可能是十万大山盆地油气勘探的一个新领域。

The Tingliang reef palaeopool of the lower Permian Maokou Formation is one of the destroyed oilpools in the Shiwandashan basin of Guangxi province,and its bitumen-bearing reservoir (above 98 meters in the thickness) occurs mainly in the upper part and at the top of the reef body. The formation and distribution of the secondary solution porosity of this reef are mainly controlled by organic solution. and they are also spatially related to the weathering palaeocrust of the unconformity. This paper describes the burial history, thermal history, diagenetic porosity evolution history and their relations with this reef. The diagenetic types and the oil pool-forming mechanism of this reef are also discussed. Seismic profiling reveals 31 'reef' anomalous bodies in the northeastern basin and 9 are found by electrical prospecting. They occur in the same region and overlap one another. The exposed reefs and the buried 'reefs' lie in the same palaeolitho-geographic zone, suggesting that there may be a buried reef zone of the lower Permian platform margin type in the Shangying-Tai'an area. We also found that the zone of oil and gas extends for 150 km in the northern basin. Therefore, we should pay more attention to the study of buried reef oil pools, because they might be a promising new field in petroleum prospecting of the Shiwandashan basin.