Research On Sequence Stratigraphy And Depositional System Of The Paleogene-Neogene Niger Delta Basin

The Niger Delta Basin is rich in oil and gas resources,and the exploration degree of shallow structural traps(traps)in the basin has been continuously improved in recent years.However,most of the previous oil and gas geological studies have focused on oil and gas production,and the existing research results on sequence and deposition are complete.Consequently,this provides poor guiding significance for the study of sequence stratigraphy and sedimentary system at the whole basin level.The thesis is guided by the theory of sequence stratigraphy and sedimentology.Through comprehensive analysis of drilling/logging,seismic,and core data,the sequence stratigraphy and sedimentary system have been developed for the Paleogene-Neogene stratigraphic classification in the Niger Delta Basin.The advantageous areas,favorable horizons and targets of subtle oil and gas reservoir exploration in the study area have been therefore made.Based on qualitative-quantitative analysis of drilling / logging and seismic data,14 secondary sequence interfaces and 13 secondary sequence sequences were identified in the Paleogene-Neogene strata of the Niger Delta Basin.The 2nd-3rd sequence division scheme on the whole basin level was determined,and the isochronous sequence stratigraphic framework was established.Based on the core data,the study of sedimentary system was carried out,the type of sedimentary facies development and filling evolution characteristics under the constraints of sequence lattice were clarified,and the delta-gravity flow accumulation development model in the study area was established.In this paper,high-frequency sequence stratigraphic studies on key areas and anatomical areas were conducted,and a high-frequency(three-fourth-level)sequence stratigraphic division scheme in the A block was established.The developmental positions of the deposition centers of different sequences in the block are affected by tectonic activity and delta migration at the same time.Vertically,the(SQ2)sequence is thick and the top and bottom(SQ1,SQ3)sequences are thin.Horizontally,the strata are characterized by the distribution of "thin in the north and thick in the south,and thin in the east and west".Using logging,seismic and core data,etc.,the sedimentary facies of the A block under high-frequency sequence constraints was studied.It is believed that in addition to the development of large-scale delta front sediments,the A block develops largescale gravity flow channels and turbidite fan deposits.Studies suggest that large-scale turbidite fans and gravity flow channels are developed at the bottom of SQ3 and SQ1,respectively.At the same time,the plane distribution range of gravity flow channels and turbidite fans in the LST + TST system domain is determined.According to the guiding ideology of hierarchical research,the hierarchical sequence stratigraphy and sedimentary system were studied in the Niger Delta Basin,and new ideas for the exploration of hidden oil and gas reservoirs in the study area were proposed.It is believed that the oil and gas exploration targets in the study area should be transformed into stratigraphic-lithological traps in offshore and landward areas.It indicates that the study of A should focus on the subtle traps related to gravity flow deposition.Prediction of the stratigraphic-lithologic trap exploration advantage zone,favorable stratum system and target in the study area.