Study On Foming Models Of Deep Condensate Gas Pool In Dongpu Depression

Basing on the exploration experiences in Dongpu depression,by analyzingcondensate gas pool-forming characteristics and gas reservoir characteristics,this paperstudys hydrocarbon generation, charging history, structure evolution,and petroleumaccumulation ,the dynamic model of condensate gas migration and accumulation inDongpu depression is also established by studying the whole process ofgeneration,migration,and accumulation of condensate gas.The main achievement ofthis paper is as follows.This paper studies the distinct geological conditions for the enrichment ofcondensate gas in Dongpu depression:deep burried depth,unusual high pressure,andhigh quality seals.In this area,condensate gas is of deep,large amount,widelyspread,surrounding sags.Condensate reservoirs have complicated conditions,e.g,hightempratures,high pressures,varied fluid properties,and a few reservoirs have higherparaffin contents.Study on the hydrocarbon generation strength of source rocks shows thathydrocarbon generation strength at 4000-5000m is not less than that of the peak oilgeneration stage,and the condensate gas window expend downward because of highpressure inhibition.During both gas generation stages,high maturation condensate gasis predominately generated,this is why condensate gas distributes widely.Thermal evolution of Cenozoic shows that ES3 source rocks in central parts of sagsproduced a large amount of gas at the end of later tertiary,Qianliyuan sag,Haitongjisag,and Gegangji sag are the profitable areas of secondary gas generation,and all ofthe condensate gas pools found as of today locate surrounding them.Condensate gas is of compounded generation characteristics,oringinal generationand subsequent formation can be classified according to the phases and process duringtheir genenration,multi-forming factors accounts for an important reason why thereservoir characteristics are complicated.Illite dating and fluid includes analysis show that condensate gas pools in typicalQiaokou-Baimiao condensate gas areas formed in three times of charging duringDongying member depositing period,erosion of Dongying member,and late tertiaryabout 7 to 5Ma respectively,which proves that Qiaokou-Baimiao condensate gas poolsare of multi-period charging and late period charging.Pure condensate gas pool and gas-cap condensate gas pool are recognizedaccording to their occurrence,and their distribution and pool-forming models are studiedby integrating studies on hydrocarbon generation,structure evolution,charginghistory,and petroleum migration and accumulation. Gas-cap condensate gas poolsmainly formed in a single time during ES1-Ed periods in early tertiary,those poolsdistribute at shallow-middle depth at northern part of the central uplift with betterpreservation conditions mainly controlled by structures with less multi-period damage.Deep condensate gas pools are of multi-period charging and late periodcharging,shorter distance migration,and self-generation and self-reserving,mainly locatesurrounding sags,and controlled by structures and lithologies ,and have a highexploration potential because of the sustainable late period gas supply,goodpreservation afterwards,and large prospective area near the sags.Three major deep condensate gas exploration profitable areas in Dongpudepression are made clear,i.e.,north gas area surrounding Qianliyuan sag, south gasarea surrounding Gegangji sag,and west gas area surrounding Haitongji sag.This paper is the first time to conduct a specialized and detailed research oncondensate gas pools in Dongpu depression, which has real significance to establishdifferent condensate gas pool-forming models, enriching recognition of gas pool-formingin Dongpu depression, and condensate gas exploration.