东营凹陷热液流体活动及其油气地质意义

Hydrothermal fluid activity and its hydrocarbon geological significance in Dongying depression

为了明确含油气盆地中热液流体活动的发育特征及其油气地质意义,以渤海湾盆地东营凹陷古生界和新生界古近系为研究对象,通过岩心、薄片、激光拉曼、岩石热解、同位素、微量元素、稀土元素、黏土矿物X射线衍射、扫描电镜和高压压汞等手段,识别了含油气盆地中热液流体的活动标志,并对其油气地质意义进行了探讨,认为东营凹陷中热液流体活动较为发育并具有重要的油气地质意义.研究结果表明:东营凹陷中发育多种热液流体活动的指示标志,包括多种热液矿物及其组合类型;特殊的岩石颜色和结构;幔源成因的CO2气藏;具有异常高Tmax或S1与S2值的泥岩;硫同位素表现为深源或有深源硫参与的特征;具有热液成因的碳酸盐脉;泥岩中Co,Ni,Zn和Mo等微量元素出现异常高值;灰岩的稀土元素具有Eu正异常;凹陷中浅层砂岩中伊利石质量分数超过40%或者绿泥石质量分数超过25%.热液流体活动可以促进湖水分层的形成,有利于优质烃源岩的发育;热液流体的高温高压效应有利于烃源岩的生排烃和油气的运移;热液流体可以溶蚀岩石中的不稳定组分从而形成次生孔隙,同时热液流体通过促进绿泥石的发育来抑制次生石英加大的形成,从而改善砂岩储层的孔隙结构.

To clarify the development characteristics of hydrothermal fluid activity and its geological significance in petroliferous basins,the Paleozoic and Cenozoic Paleogene in Dongying depression of Bohai Bay basin was taken as the research object.Based on the data of core,thin sections,laser Raman,rock pyrolysis,isotope,trace element,rare earth element,clay mineral X-ray diffraction,SEM and high pressure mercury injection,the indicators of hydrothermal fluid activity were studied and its hydrocarbon geological significance were discussed.It is considered that hydrothermal fluid activity is well developed in Dongying depression and has important hydrocarbon geological significance.The results show that there are many indicators of hydrothermal fluid activity in Dongying depression,including a variety of hydrothermal minerals and their combinations;special rock color and structures;CO2 gas reservoirs with mantle source;mudstone with abnormally high Tmax or S1 and S2 values;sulfur isotope exhibiting deep source or the participation of deep source sulfur;carbonate veins with hydrothermal genesis;the abnormally high characteristics of trace elements such as Co,Ni,Zn and Mo in mudstone;the rare earth elements in limestone with Eu positive anomaly;the illite content of more than 40%in shallow sandstone of depression or the chlorite content exceeding 25%.Hydrothermal fluid activity can promote the stratification of lake water and facilitate the development of high quality source rocks.The high temperature and high pressure effect of hydrothermal fluid is beneficial to the hydrocarbon generation and hydrocarbon migration.Hydrothermal fluid can dissolve unstable components and form secondary pores in rocks,and hydrothermal fluid inhibits the formation of secondary quartz by promoting the development of chlorite,thereby improving the pore structure of sandstone reservoirs.