Study On Sedimentary System Of Pliocene In BN-HM Basin

With the rapid development of society,the demand for oil and gas resources in the world is increasing day by day.The exploration and development of traditional oil and gas reservoirs can no longer meet the needs of people.With the development of technologies of oil and gas exploration,people have turned their attention to the sea.The exploration of deep-water sandstone reservoirs has become a hot spot nowadays and many large deep-water sandstone reservoirs have been discovered in the world.The BN-HM basin,located in the northern part of the XT continental shelf in the northwest of PLZ,is a hot area for oil and gas exploration.A large scale oil and gas fields have been discovered in the central and southern part of the HM basin,while the deep water area below the continental shelf margin at the boundary of BN basin and HM basin has a relatively low degree of exploration.Domestic and foreign scholars have carried out a series of basic geological studies in this area,which prove that this area has good geological conditions for forming and storing oil and gas.However,due to the lack of sedimentary system research,the effective reservoir can not be found.And the oil and gas exploration in this area has not been a major breakthrough.Therefore,the study of sedimentary system of Pliocene at the boundary of BN basin and HM basin carried out in this paper in order to find the distribution of favorable reservoir facies zone.The study of sedimentary system based on seismic data is mainly to obtain a large type of sedimentary environment by seismic facies analysis,and then combine the lithofacies information revealed by drilling data to realize the transformation from environment to sedimentary facies.But the research area of this study lacks the drilling data so that we cannot realize the transformation from seismic facies to sedimentary facies.In order to solve this problem,we use the method ? sedimentary environment + framework lithofacies + flow path = sedimentary system?.We use traditional seismic facies analysis to confirm sedimentary environment and use seismic lithofacies analysis to confirm the distribution of framework facies.And then combining the control of provenance of sedimentary facies to get the distribution of sedimentary system in Pliocene.Through the above work,the following aspects of understanding have been achieved:1)Recovering the original shape of the sedimentary layer by using the seismic line drawing technology.And then realizing the way that the stratigraphy stacked.And confirm the sedimentary environment initially.2)Using the traditional seismic facies analysis to divide the study area into shallow-bathyal continental shelf environment,bathyal continental slope environment and deep-sea basin environment.We can also find delta lithosomic body,deep-water fan lithosomic body and clastic flow lithosomic body.3)Through seismic lithofacies analysis,combined with the large types of environment and sedimentary bodies obtained by traditional seismic facies analysis,the framework lithofacies of the study area are obtained: the delta plain distributary channel sand body,the delta front estuary bar sand body,the delta front sand sheet.shallow sea shelf facies sand,continental slope facies sand,deep-water fan sand,deep-sea basin mudstone and deep-sea basin clastic flow sediment.4)Superimposing large types of sedimentary environments and framework lithofacies and combining the control of provenance of sedimentary facies can obtain the distribution of sedimentary systems of sequences in Pliocene in the study area.The continental margin delta-deep-water fan sedimentary system is developed in the western part of the study area,while the middle-outer shelf delta-continental shelf margin mud-rich precession sedimentary system is developed in the eastern part of the study area.5)According to the distribution of sedimentary system in the study area and the oil and gas geological conditions in the study area,the distribution of favorable reservoir facies zones of each sequence of the Pliocene in the study area is divided.