Sedimentary System Study On The Oilocene-miocene In The Western Depression Of The TX Basin

The TX Basin is located in a certain sea area of China.It is one of the petroliferous basins which have the lowest degree of exploration in the China sea.The study area of this paper is the Western Depression of the TX Basin,and the study and cognition degree of this depression is relatively low.And whether exist oil and gas resources is an urgent problem to be solved.The target horizons of this research are Oilgocene series and Miocene series,and the content of this study is the distribution of depositional system in the sequences.Previous research results show that the sedimentary system of the research section are mainly marine sediments.The interior of the section developed high quality sandstone reservoir and it provided better conditions of generation,reservoir and cap for the whole petroleum system of the basin with the lower deep lacustrine source rock and the upper regional cap.Therefore,characterizing the distribution of sand bodies within the Miocene-Oligocene sequences in the study area and recovering the corresponding depositional system are of great significance to the study of the petroleum geological conditions in the Western Depression of the TX Basin.For this purpose,on the basis of full understanding of previous research results,we started from the previous studies on the geological tectonic setting,stratigraphic and sedimentary characteristics and structural features of the Western Depression of the TX Basin.According to contrast seismic characteristics,strata and sequences of nearby region and basing on seismic data,we can reconstruct the sedimentary basin of the original structure and confirm sedimentary environment through the method of Seismic Line Drawing.Then based on this,we can select typical seismic profiles in the study area to depict the internal sand body of the sequences of the target strata in the study area,and we can characterize and delineate dominant seismic facies and the development and distribution of high quality sand bodies from the plane.After that,we use method of source control and phase control to establish the depositional system relationship between delta,slope and deep-water fan.Then combined with the sedimentary environment and water system,realized the comprehensive analysis of the sedimentary system in the study area.On the basis of the sedimentary system,a certain degree of oil and gas geological conditions are studied.Through the research of this paper,the following aspects are obtained:(1)According to the analysis of seismic data,a preliminary investigation to determine the area of Cenozoic has 8 main seismic reflection interface,including T3,T6,T8-1,T9,Tg five major regional unconformities.And based on the analysis,third structural sequences of I-1,I-2,II-1,II-2 and II-3 were identified in the study area.(2)Based on careful interpretation of seismic profile,according to Seismic Line Drawing to rebuild original structure of sedimentary basin,confirming that the sedimentary environments of Oligocene series of the study area are shallow shelf and bathyal intrashelf sag and the sedimentary environment of Miocene series is continental margin shelf.Through the recognition and classification of seismic reflection characteristics,a total of 6 dominant seismic facies are identified and classified in the study area.Then analyzed the geological significance of each seismic facies and confirmed the distribution of dominant sedimentary facies in the study area.All these provides an important basis for the analysis of sedimentary environment.(3)Through the waveform analysis,combined with the examples of nearby region which have been verified to determine the waveform characteristics of lithofacies of framework sand body.Taking sand body scanning in the target horizons of the study area and confirming temporal and spatial distribution of different types of sand bodies.Then combined with the distribution of sedimentary facies and sedimentary environment analysis to determine the sedimentary system of Oligocene series and Miocene series which are the purpose layers of the study area and divided into delta,neritic shelf,slope facies and so on and confirm contextual relationship of delta—Deep-water fan.