关键词: 烃源岩, 埋藏史, 生油史, 初次运移, 类型

Abstract: Based on three case studies of soure rock's burial,oil generation and expulsion models,it is suggested that burial oil genera ting history is the key to oil primary migration.The initiation and degree of oil expulsion from a source rock(SR) greatly depends upon its burial oil generating history.Five types of burial oil generation expulsion of SRs are classified with their characteristics of oil primary migration from varions burial oil generating histories.The first is deep burial high maturity favoring oil expulsion.This type of the SR undergoes a continued burial to a great depth over 3000m,resulting in speedily organic matter cracking to a high level of maturity(Ro≥1.0%).Therefore,overpressure within the SRs is probably developed,in favour of fracturing and then initiating oil expelling.The second is deep burial uplift high maturity favoring oil expulsion.This type of SRs is buried to a depth over 3500m,resulting in high maturity(Ro>1.0%) before they are tectonically up lifted to a shallower depth.Oil expelling from these SRs mainly occurs prior to the event of the elevation.The third is medium burial medium maturity retarding oil expulsion.This group of the SRs is early buried down to a level of approximately 2500m or less,and from then on,the SRs experience a tectonically stable period,being prevented from successively subsidence or greatly uplift.Nearly by the end of early burial process,the organic matter reaches oil generating stage and hold the organic matter cracking in a slowly rate due to being exposed to relatively low temperature.Although these SRs can reach oil saturation threshold of oil expulsion(OSTOE),oil primary migration hardly ever happens due to absence of overpressure due mainly to stopping of sedimentation,slowly organic matter cracking and medium depth.The fourth is medium burial uplift low maturity obstacling oil expulsion.As the SRs are buried down to a medium depth(<2500m) at which kerogen begins to decompose into oil,there follows tecotonically uplift,causing sharp decrease in temperature,SRs are exposed to.Therefore,the reactions of kerogen cracking into oil slow down,even stop when the temperature decreases in 15℃ more than maximum temperature,SRs have been exposed to before,resulting in low maturity and without reaching OSTOE.Primary oil migration of this type of SRs could never occur because of low maturity(Ro<0.8%) and never reaching OSTOE(<10%) for oil movement.The last type is shallow,medium burial low maturity favoring immature oil expulsion.The principal zone of immature oil formation occurs during the burial of shallow,medium depth(<2500m;corresponding to Ro:0.35-0.7%).And So,these low maturity SRs capable of formation of immature oil can reach OSTOE in the early stage of burial,compared to those SRs generation mature oil only.Moreover,it is very often in the early burial stage that expulsion of immature oil can be enhanced by SR disrupting due to growth faults,especially in fault basins,for instance,those basins of eastern China with widespread occurrence in immature oil.These five types of burial oil generation expulsion of SRs,which we have classified will have significance in early appraisal of "oil kitchen".

Key words: source rock, burial history, oil generation, primary migration, classification