渤海海域深部热流体存在的证据及其对油气成藏意义——以秦皇岛29-2/2E油气田为例

Evidence of deep fluid and its influence on gas reservoiring in Bohai Sea:Case study of QHD29-2/2E Oilfield

深部热流体被越来越多证实参与油气成藏的全过程。通过岩心、岩石学、流体包裹体及有机地球化学等资料,系统探讨了研究区(秦皇岛29-2/2E油气田)深部热流体活动的详细证据及其对油气成藏的意义。研究表明:古近系储层流体包裹体测温见异常高温包裹体;天然气藏中发现CO_(2)为火山幔源无机成因气;方解石脉体氧同位素测试值远高于围岩且受高温热液影响;沉积物中发现立方体、五角十二面体黄铁矿,Co/Ni值大于1,为热液成因。热流体对该区油气成藏包括生排烃和储层改造两方面:热流体促进该区烃源岩演化,提升生烃量;热流体对储层物性改造既有溶蚀改造的积极建设作用,又有热液方解石和晚期白云石胶结充填破坏作用。

Deep fluid was increasingly identified involved in all processes of hydrocarbon accumulation. Based on data from drilling core,petrology,fluid inclusions and organic geochemistry,we discussed the detailed evidences of the activities of the deep fluid as well as its effect on hydrocarbon accumulation. The evidences include:(1)Abnormal high-temperature fluid inclusions in Paleogene reservoir;(2)CO_(2) gas in discovered reservoir being inorganic origin from volcanic mantles;(3)Oxygen isotopic values in calcite filled veins much higher than surrounding rock;(4)Cubic and pyritohedron pyrite found in sediments with Co/Ni ratio more than 1 indicating hydrothermal origin. These all showed that there might be deep fluid participated in the reservoir accumulation,the affection of which includes hydrocarbon generation and expulsion as well as reservoir reconstruction. The deep fluids promoted the evolution of source rocks in this area and increased hydrocarbon generation volume. As for reservoir quality,it has the constructive role of hydrothermal corrosion and the destructive role of hydrothermal calcite and late dolomite cement and filling.