叠合盆地成藏流体源类型、演化及控藏意义——以中国南方中、古生界海相地层为例

Types,Evolution and Pool-Controlling Significance of Pool Fluid Sources in Superimposed Basins: A Case Study from Palaeozoic and Mesozoic Marine Strata in South China

中国南方经历了多阶段构造演化的历史,具有典型叠合盆地性质,海相地层以次生油气藏为主,成藏流体源成为首要控藏要素。结合中国南方8个典型油气藏的实例,总结了叠合盆地成藏流体源类型,分析了其随时空的演化规律及其对油气分布的控制作用。认为中国南方海相地层的成藏流体源包括烃源岩热解烃、原油裂解气、二次生烃、水溶气、无机气及混合气等多种。在印支期之前以烃源岩热解烃为主,印支-燕山期主要形成原油裂解气和水溶气,燕山-喜马拉雅期主要形成由各种气源构成的混合气。受成藏流体源控制,混源型气藏主要分布于上扬子区(四川盆地);原生型油(气)藏主要形成于江南等古隆起区,但大多已演化为古油藏;二次生烃型气藏主要分布于下、中扬子白垩系-古近系覆盖区,及楚雄盆地、十万大山、南盘江等地;无机型气藏形成于张性构造区。

With multiple stages of tectonic evolution, South China belongs to superimposed basin in nature, dominated by secondary gas pools in its marine strata. Hence, the pool fluid sources are the most important pool-controlling factors. Based on eight typical oil and gas pools, this paper summarizes the types of pool fluid sources, and analyses the time-space evolution and its control over the petroleum distribution of pool fluid sources. The pool fluid sources in marine strata of South China include hydrocarbon generated primarily from source rocks, gas cracked from crude oil, hydrocarbon generated secondarily from source rocks, gas dissolved in water, inorganic gas and mixed gas. The primary hydrocarbon was the main source of pools prior to Indo-China period. Whereas the secondary hydrocarbon gas and gas dissolved in water were formed during Indo-China to Yenshan period. The mixture of above various gases was main pool fluid source during Yenshan to Himalayan period. Controlled by pool fluid sources, the pools with mixed gas sources are mianly distributed in upper Yangtze block, especially in Sichuan basin; and the pools with primary hydrocarbon sources are found in Jiangnan palaeo-uplifts. However,most of these pools became fossil pools. The pools with secondary hydrocarbon source are distributed in the areas covered by Cretaceous and Eogene System in middle and lower Yangtze blocks, as well as Chuxiong basin, Shiwandashan basin and Nanpanjiang basin. The pools with inorganic gas source are mainly formed and distributed in tensional structure areas.