中国南方海相生烃成藏研究的若干新进展(三) 南方四套区域性海相烃源岩的沉积相及发育的控制因素

南方研究区下寒武统、上奥陶统—下志留统、下二叠统、上二叠统四套区域性古生代海相烃源岩可划分为7种有利沉积相:即深水泥质陆棚相、深水热水陆棚相、深水碳酸盐岩陆棚相、深水硅磷质台凹相、海湾澙湖相、近海湖盆沼泽相、前三角洲相。四套海相烃源岩的沉积—生物相图反映出这些相都不同程度与大洋相通。从早寒武世到晚二叠世,烃源岩的相类型向多样化发展。受都匀、东吴运动影响,有利相带的分布范围由大到小出现两个旋回。南方海相烃源岩的发育受板块运动、板内活动、三大古隆起、四个转换期、沉积—生物相等五个因素的控制。南方海相优质烃源岩的形成模式可概括为深水陆棚—底栖藻席模式,其特点是底栖藻类发育,沉积表面氧化而埋藏环境还原,并以此区别于已有的三种形成模式。研究区北面的秦岭洋,南面的华南洋(Pz1)、八布洋(Pz2)伸入扬子克拉通内部形成的不同时期"海湾体系",是海相烃源岩发育的摇篮,可作为南方海相油气勘探的一个重要领域。

Some Progresses on Studies of Hydrocarbon Generation and Accumulation in Marine Sedimentary Regions,Southern China (Part 3):Controlling Factors on the Sedimentary Facies and Development of Palaeozoic Marine Source Rocks

There are 4 suites of Paleozoic marine source rocks, including the Lower Cambrian,the Upper Ordovician- Lower Silirian, the Lower and the Upper Permian ones, in the studied area of South China. These source rocks can be divided into 7 favorable depo-biofacies: namely deep-water argillaceous shelf facies, deep-hot-water shelf facies, deep-water carbonate shelf facies, deep-water silicophosphatic platform-seg facies, bay lagoon facies, offshore lake-basin swamp facies and prodelta facies. The 4 suites of depo-biofacies diagrams of regional marine source rocks indicate that all of these facies are connected to some extent with oceans. These facies of source rocks repre- sented to diversify from Early Cambrian to Late Permian periods. Influenced by the Douyun and Dongwu Movements, the distribution area of favorable facies zones varied from broadness to narrowness in two cycles. The development of marine source rocks in South China has been controlled by five factors, such as plate movements, intraplate activities,the three big palaeohighs, the four transform periods and depo-biofacies. The formation pattern of marine source rocks in South China consists of the deep-water shelf and benthonic algal mats characterized by the upgrowth of benthonic algae, the oxidation of depositional surface but reduction of burial settings. This pattern differs in these characters from the other three formation patterns that have already occurred. In the studied area, the Qingling Ocean in the north, the Huanan Ocean in the south(Pz1)and the Babu Ocean (Pz2) intruded into the Yangtse Craton to form "bay systems"at different times,which are cradles for the development of marine source rocks and significant targets to explore marine oils and gases in Southern China.