| Huizhou sag,one of the richest hydrocarbon generation sag in Zhu I depression,has found more than ten big oil and gas fields in neogene strata.Due to the restriction of deep-sea exploration,the exploration of paleogene strata doesn't have major breakthrough.Recently,there are oil and gas reservoirs found in Huizhou 25 area of which the physical property are poor and vary horizontally.With the oil,water and dry formation coexist and lacking of unified oil-water interface,the distribution law of oil and gas is complicated.Thus,the geological feature and mechanism of hydrocarbon accumulation should be studied further.To learn more specifically of the paleogene Huizhou 25 reservoir has significant meaning of further study of deep hydrocarbon exploration of paleogene reservoir in south China sea.Under the guidance of petroleum geology,the static and dynamic geological characteristics of hydrocarbon accumulation of Huizhou 25 reservoir are analyzed and they enrich the study of deep paleogene reservoir of Huizhou25 area.1.Collect the basic geological data of Huizhou 25 area and the area surrounding it,including the single-well lithology data,logging data,well test data,hydrocarbon source rock pyrolysis data,seismic data,etc.On the basis of these data,this article analyzes the source rock,reservoir,cap rock,trap and oil-water distribution rule of the static geological features of Huizhou 25 reservoir.There are two sets of hydrocarbon source rocks in the study area,shore and shallow lake-deep lake facies dark mudstone of source rock of Wenchang formation and shallow lake facies-limnetic facies,delta plain swamp-fluvial facies coal-bearing mudstone of source rock of Enping formation.It is confirmed that the source rock of Wenchang formation is the main source rock of the study area.Today,the physical property of reservoir is poor,the average porosity is about 12%and the average permeability is above 0.1Md.On the top of Wenchang formation,there is a set of front delta facies regional cap rocks.The sandstone reservoir under the regional cap rocks and the cap rocks form well reservoir-cap assemblages.The oil-bearing structure of Wenchang formation of Huizhou25-7 area is a stratigraphic overlap trap developed on a big nose shaped high.There are two main oil bearing stratum called N10 and N56.Oil and gas gathered in high part of reservoir,and oil stays on upper part of reservoir while water stays in lower part.2.According to the analysis of the source of hydrocarbon,the hydrocarbon accumulation period,the path of hydrocarbon migration and the relation between hydrocarbon accumulation period and the reservoir dense period of Huizhou25-7 reservoir,the dynamic features of hydrocarbon accumulation mechanism is made clear.The oil and gas of N10 and N56 oil bearing stratum are from the source rock of Wenchang formation.To be more specific,the hydrocarbon of N10 mainly came from the deep lacustrine deposits of Wenchang formation and the hydrocarbon of N56 mainly came from the shallow lacustrine-semi lacustrine deposits of Wenchang formation.To use the hydrocarbon-generated potential method and the fluid inclusions testing technique,the main controlling factors of effective reservoir are advantageous sedimentary facies and low potential areas.The oil and gas of Huizhou25-7 reservoir is accumulated before the reservoir became tight.Facture and continuous sandstone are the main migration pathway of oil and gas in the study area.The fluid potential map of different oil bearing formation is constructed and the advantageous directions of hydrocarbon migration are clear.3.Through the analysis of the static and dynamic features of hydrocarbon accumulation of the study area,the evolution characteristics of reservoirs and the analysis of characteristics of hydrocarbon reservoirs,the hydrocarbon accumulation mechanism of Huizhou25-7 reservoir is clear.The reservoir had good physical properties during its developing time and the hydrocarbon is sealed in high part of reservoir.And the reservoir was formed under high pressure. |
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