中国华南地区下寒武统烃源岩沉积环境、发育模式与分布预测

早寒武世是地史中生命爆发的重要时期，海侵作用导致全球广泛发育富含有机质的黑色页岩，将其成就为全球油气最为重要的勘探层系之一。中国华南地区虽然也广泛发育下寒武统黑色页岩，但是由于受古地貌、沉积相、后期构造变动等因素影响，导致烃源岩空间分布差异大、非均质性强，给油气勘探带来风险。在前人大量基础研究工作的基础上，通过对华南地区11个露头剖面和3口钻孔资料的调研收集、以及新观察采集1个剖面的样品测试分析，综合运用主微量元素、铁组分、有机碳含量、古生物等分析资料，系统研究了华南地区寒武系烃源岩的地质地球化学特征与成因机制。发现下寒武统烃源岩在纵向上具有自下而上水体从硫化到还原再到弱氧化、TOC逐渐降低、烃源岩质量逐渐变差的特点，微量元素和铁组分数据揭示了古海洋环境演变对优质烃源岩形成的控制作用；平面上自西向东烃源岩质量变好、TOC逐渐增高、厚度增大，表明沉积相对烃源岩分布具有控制作用，揭示了斜坡相和台地相裂陷槽内烃源岩的质量最好。基于大量分析资料和剖面对比，认为烃源岩厚度和质量明显受控于古裂陷和沉积环境。结合露头和钻井资料，对华南地区下寒武统烃源岩厚度分布开展预测，明确了深层油气和页岩气富集的有利地区。

Sedimentary environment,development model and distribution prediction of Lower Cambrian source rocks in South China

The Early Cambrian was an important life explosion period in geological history. Because of marine transgression, the black shale rich in organic matter are widely developed, and thus has become the most important hydrocarbon exploration strata in the whole world. Although the Lower Cambrian black shale is widely developed in South China, due to such factors as paleo-geomorphology, sedimentary facies, and late tectonic deformation, the source rocks have a large difference in spatial distribution and strong heterogeneity. This will bring risks to hydrocarbon exploration. Based on plenty of previous basic research work, we collect geochemical data of 11 outcrop sections and drilling data of 3 wells, as well as analyze the newly observed and collected samples from a section in South China. This paper systematically studies geological and geochemical characteristics and genetic mechanism of the Cambrian source rocks in the study section through the comprehensive use of major and trace elements, iron components, total organic carbon (TOC), and paleontology. It is found that the Lower Cambrian source rocks are characterized by the sulfuration, reduction and weak oxidation of water bodies from bottom to top, a gradual decrease in TOC, and gradual deterioration of source rock quality. The data of trace elements and iron components reveal the control of the paleo-ocean environment evolution on the formation of high-quality source rocks. Horizontally, the quality of source rocks becomes better from west to east, TOC gradually increased, and the thickness also increases, indicating that sedimentary facies have a controlling effect on the distribution of source rocks, discovering the highest quality source rocks in the rift trough of slope facies and platform facies. Based on plenty of analysis data and comparison of sections, it is believed that the thickness and quality of source rocks are obviously controlled by ancient rift and sedimentary environment. In combination with outcrop and drilling data, this paper predicts the thickness distribution of the Lower Cambrian source rocks in South China, and determines the favorable areas for the accumulation of deep oil and gas and shale gas.