Tide-influenced Delta Sediment Of Neogene In HuiZhou Depression,Pearl River Mouth Basin

The Pearl River Mouth Basin is the most potential petroleum bearing basin in north of South China Sea.After decades of exploration and exploitation,it is more and more difficult to find large structural traps with great economic benefits,subtle reservoirs have become the key for exploration.The research area from zhujiang formation to Yuehai formation are marine facies,with the barrier affect of south uplift and centre uplift belt,there are developing tide-influenced deposit in part of history time.While it is rather difficult to recognize the distribution of sedimentary facies and favorable sand bodies,for reason that there is a wide area but few wells and the 3D seismic data is limited.So it is very critical to enhance sedimentological research for this area.Make definite of the tide affect and then to analyse the rule of sand distribution,has become very important to research the exploration of strata-lithology hydrocarbon reservoir.This theme make the bace of lithology description to find out the character of tide-influenced delta,then to make analyse the lithofacies combination and sedimentary microfacies.Combinate facies?sand thickness and others of responding sea level fluctuate and the result of the investigation river mouth,to research the relationship between tide action?wave action?river action.According to the background of sedimentary,under the sedimentology direction,associate the log response character of tide-influenced formation,utilize seismic reflection character to divide the affect area by tide influenced.Make the tide-influenced delta formation in the 3D seismic area as the research target,to analyse the developing of sand affect by tide action.According to research fruit?exert sequence stratigraphy theory to direct,combination the way of seismic sedimentology,to confirm the locate of favorable area,launch the identification of strata-lithology trap.The analysis of flake data contain four aspects,such as sand component character?mineral maturity?light mineral combination?debris content variety,and think that there are three provenances such as northwest?northeast and south.The distal provenances are northwest provenance and northeast provenance,south provenance is the proximate provenance,K22 formation only exist in the northwest provenance.According to the investigation of tide deposition in modern times of South China coastal,tide action is so common,and have various types.When tide action?wave action?river action happen together,it will form various deposition models and sand distribution.In the Oligocene and Miocene of Pearl River Mouth Basin,tide plays an important role in the deposition process,it has influenced sand distribution and physical property.This research will have a profundity significance to explore strata-lithology trap.The observation and description of cores,show that 22 types of lithofacies developed in the reserch interval,they are:conglomerate with massive bedding facies(Cm),glutenite with massive bedding facies(Gm),glutenite with trough cross stratification facies(Gcs),glutenite with tabular cross bedding facies(Gt),sandstone with massive bedding facies(Sm),,sandstone with tabular cross bedding facies(St),siltstone-fine sandstone with low angle cross bedding facies(Silc),sandstone with wedge cross bedding facies(Sw),sandstone with swash cross bedding facies(Ss),sandstone with parallel bedding facies(Sp),siltstone with horizontal bedding facies(Sih),sandstone with ripple bedding facies(Sr),siltstone with ripple bedding facies(Sir),siltstone with mixed bedding facies(Sim),siltstone-fine sandstone with deformed bedding facies(Sid),sandstone with lebensspur facies(S1),mudstone with burrow pore facies(Mb),sandstone with bioclast facies(Sb),glutenite with graded beds facies(Gg),glutenite with tindanan facies(Gt),dark mudstone facies(Md)and grey mudstone facies(Mg).According to the lithofacies character,the research area has identified delta deposition system.shoreland deposition system.continental shelf deposition system?tidal flat deposition system.Delta facies contains delta plain?delta interfront?delta outsidefront.Shoreland facies contains shoreface and foreshore.Continental shelf facies contains transition zone and ffshore shelf.Tidal flat contains intertidal and subtidal zone.After multidisciplinary analysis of lithologic character and sedimentary structure,tide-influenced delta deposition has been identified in research formation of Pearl River Mouth Basin.Tide-influenced delta interfront contains tide-influenced underwater distributary channel and interchannel.Tide-influenced delta outsidefront contains tide-influenced river mouth bar.distal bar and sand sheet.In different formations,the area and grade of tide-influenced deposition are different.In Zhuhai formation and Zhujiang formation,tide-influenced deposition character is obviously stronger than up strata.This phenomenon is mutually related with sea level fluctuation and sedimentary palaeotopography.With the rising of sea level and the affect of backfill,Pearl River Mouth Basin tend to level and smooth,the tide action will diminish than before.