Research On The Sedimentary Characteristics Of The Glutenite In Lower Cretaceous Of The Western Slope Of The Southern Sag In Bayindulan Depression,Erlian Basin

In recent years,glutenite reservoirs have been discovered of the western slope of the southern sag in Bayindulan Depression,Erlian Basin,and many industrial flow wells have been obtained here,which shows a good prospect for exploration and development.Therefore,in the process of oil and gas exploration and development of the western slope in Bayindulan Depression,how to effectively search for and discover high-quality reservoirs becomes extremely important.This article is based on previous studies,and mainly conducts in-depth research on the Lower Cretaceous glutenite body in the western slope of the southern sag.Through the macroscopic and microscopic recording and description of the cores of the western slope of the Nansag,combined with the theoretical knowledge of related disciplines,the stratigraphic framework is judged and calibrated of the western slope of the southern sag in the Bayindulan Depression,and then a comprehensive analysis of the sedimentary characteristics and the control and influence of the developed sediments relative to oil and gas are carried out.By combining the seismic,the logging and the core data,2 first-level marker layers(top of Tenger Formation and top of Alshan Formation),3 second-level marker layers(top of Alshan 4th section,top of Tenger 1st section and top of Tenger 2nd section),and 8 third-level marker layers are identified from the Aershan Formation to Tenger Formation of Lower Cretaceousin of the western slope of the southern sag in Bayindulan Depression.The Tengger Formation is divided into Teng-1 and Teng-2 sections.The Tenger 1st section is subdivided into 5 sand groups and the Tenger 2nd section is subdivided into 4 sand groups.With the help of the recording and description data of the core and the specific logging facies and seismic facies,the fan delta plain formed in the west slope of the depression,gray-green glutenite is the main lithology,and scouring surfaces,parallel bedding and massive bedding can been seen.Light gray sandy conglomerate is the main lithology of fan delta facies that appeared and formed,and the toothed box shape is the appearance on the spontaneous potential curve,and most of the erosion surface,parallel bedding and massive bedding are formed.The lithology of the sublacustrine fan facies is mainly a large set of variegated glutenite,and slumping deformation structures can be seen.The lithology of coastal shallow lake-deep lake subfacies is mainly green and gray mudstone,mainly developed wavy bedding,lenticular bedding and scouring structures.Combining the exploration and sorting of the single-well facies and continuous-well facies profiles of the main wells in the western slope,the study and summary of the plane distribution characteristics of the different types of sedimentary facies formed in the Lower Cretaceous of the western slope of the southern sag have been completed.Analysis shows that during the Arshan Formation,depressions slowly expanded and evolved into lake basins,which was the initial stage of lake basin formation,and fan delta facies widely appeared and developed;during the period of Tenger 1st section,the stratum is in the depression period of the lake basin,the lake basin is extremely developed,and the water depth increases.During the middle period of Tenger 1st section,the lake basin reached its maximum flooding surface;during the period of Tenger 2nd section,the lake basin shrank further,the east subsidence intensity was high,semi-deep lake facies developed,the sediment supply in the western gentle slope increased,and fan delta subfacies developed.Combining the relationship between sedimentary facies and oil-bearing grades,it can be seen that the fan delta front has the best oil-bearing capacity,followed by the sublacustrine fan,and the coastal shallow lake-deep lake subfacies has extremely poor oil-bearing capacity.