沉积盆地深部流体的地球化学特征及油气成藏效应初探

以济阳坳陷东营凹陷和塔里木盆地塔中地区为例，在前人深部流体研究的基础上，应用同位素地球化学、有机地球化学及热力学定量模型，对沉积盆地深部流体的活动特征及其油气成藏效应进行了初步的探讨。研究表明，在东营凹陷不仅存在着幔源富二氧化碳流体（H2O＋CO2）的活动，而且还存在着幔源富氢流体（H2O＋CH4＋H2）的活动。塔里木盆地塔中地区也发现了幔源富二氧化碳的活动。深部流体上升过程中热能传递的定量研究表明，幔源流体是良好的热能载体。东营凹陷和塔中地区的有机质异常热变现象证实了深部流体的热效应。有机质热演化生烃不仅需要热，而且是个缺氢的过程，富氢流体注入沉积盆地势必对油气的生成产生影响。加氢热模拟实验结果表明，加氢可大幅度提高烃源岩的产烃率；对腐泥型干酪根而言，加氢生烃效应最显著的阶段是在生烃高峰之后，产率可增加147％以上；腐植型干酪根的加氢生烃效应在各个阶段都较显著。在东营凹陷和塔中地区分别发现了深部流体促进烃源岩生烃的现象。因此，深部流体在能量上和物质上对油气的生成均可构成重要的影响。

Primary Study of Geochemical Features of Deep Fluids and Their Effectiveness on Oil/Gas Reservoir Formation in Sedimental Basins

This paper focuses on geochemical features of deep fluids (mainly mantle-derived fluid) and their effect on oil/gas reservoirs formation in Dongiyng sag, Jiyang depression and Central Tarim basin, by using isotopic geochemistry, organic geochemistry and thermodynamics. It is found that both CO_2- (H_2O+CO_2) and H- (H_2O+CH_4+H_2) rich fluids from the mantle are injected into Dongying sag and CO_2-rich fluid in Central Tarim basin. The quantitative study of heat transformation of deep fluid ascendance shows that the mantle is an effective heat carrier. The evidence of thermal anomalies in Dongying sag and Central Tarim basin proves the existence of heat effect of deep fluids. Hydrocarbon generation from kerogen degragation not only needs heat but also actually requires hydrogen. It is known that mantle-derived, hydrogen-rich fluid may increase hydrocarbon production when the fluid meets source rocks in basins. Experimental hydrogenation simulation shows that hydrogen addition increases the production greatly. For sapropelic kerogen, the effect of hydrogenation becomes evident after fastigium of hydrocarbon generation and the production can increase up to 147%. While for humic kerogen, hydrocarbon production by hydrogenation can be increased at every stage of thermal evolution. It is found that deep fluids increase production rate of the source rocks in Dongying sag and Central Tarim basin. Hence it can be concluded that the mantle-derived fluids have great influence on hydrocarbon generation from source rocks in both energy and substance supply.