无机地球化学参数与有效烃源岩发育环境的相关研究

CORRELATIVE STUDY ON PARAMETERS OF INORGANIC GEOCHEMISTRY AND HYDROCARBON SOURCE ROCKS FORMATIVE ENVIRONMENT

探索海相有效烃源岩判识指标仍是我国油气勘探中尚待解决的重要科研任务之一。古生产力及氧化还原条件是研究全球变化和海洋环境的重要内容,也是重塑有效烃源岩发育环境的主要参数。Si、Ba是古生产力的替代指标,Cd对古营养盐的反演具良好前景。过渡金属及其相关比值是缺氧环境的有效判识指标,可用其推断有机质保存条件。δ13Ccarb正偏移指示有机质埋藏量增加,是底部水体缺氧的响应。过渡金属同位素(δ65Cu、δ66Zn、δ97Mo)受生物活动及氧化还原条件的影响发生较大分馏,示踪环境变化具灵敏、高效性。将这些无机参数对古环境的示踪意义引入油气地质研究,从环境角度分析某一套地层能否发育有效烃源岩,进而探讨高演化海相有效烃源岩的判识,就更具特殊意义。

The accurate evaluation of validity for marine hydrocarbon source rocks is one of pending important problem in oil and gas exploration and developments. Paleo-productivity and redox conditions are key variables of marine environment, global changes and paleo-environment of effective hydrocarbon source rocks(EHSR). Organic Si and Ba enrichments are evidence for enhanced productivity in marine sediments, especially, Ba enrichments can use to further investigate EHSR. Cd was used an indicator of paleo-nutrient levels, however, some limitations are visualized when it is intended as a contrast parameters of EHSR. Transitional elements, especially trace metals have been used as geochemical tools to understand anoxic depositon of recent sediments and ancient rocks, which can conclude the preservative conditions of organic matter. Positive δ^(13)C excursions are explained generally by elevated rates of organic carbon burial. It is also the response to anoxic bottom waters that are propitious to preservation of organic matter, and organic carbon isotopic trends towards depletedδ^(13)C values under such condition. The transition metal isotopes(δ^(65)Cu、δ^(66)Zn、δ^(97)Mo)can also be taken as a tracers of peleoredox conditions and biogeochemical processes for marine environments and global change researchs, which have high efficiency, sensitive, and have formed currently a new frontier in earth sciences. The trace meaning of above inorganic parameters combination to developable environment of EHSR are used for reference in oil and gas geochemical studies, whether had existed as EHSR are explored in high evolutive marine sedimentary beds, accordingly, which offer a new way for the accurate assess of EHSR during high-over mature stage.