The Cenozoic Sedimentary Facies Study In Dong Ping Area Of Qaidam Basin

Based on the project of ancient ecological and geological characteristics of oil and gas research of Dongping area,Qaidam basin in Cenozoic,and combined with previo us data,data from the outcrops,trench,and drilling core,the dissertation mainly finds out types of sedimentary facies in the study area and their distribution characteristics.It also compiles the lithofacies paleogeographic map since Cenozoic.The main conte-nts of the dissertation are as follows:1.Through analysis and study of paleogeographic background,section sedimentary characteristics and well logging data,a fan delta-lake depositional system was believ-ed developed in the study area.There was no braid river delta found in this area.Also,th-e fan delta-lake depositional system can be divided into 5 sedimentary subfacies and 8 microfacies.Results from analysis and comparison of wells suggest an early pro v-ennce from the north Altun Mountains.The sedimentary facies turns from fan delta in the north area to lake in the south area with diameters of the sediment particles app e-ars to be progressively smaller from the north to the south.2.Based on compare of sections and logging,the essay analyzes plane distributionrule of sedimentary facies from Paleocene to Oligocene by epoch,and compiles the distri-bution map of sedimentary facies.It is believed that a fan delta-lake sedimentary syst-em developed from Paleocene to Early Eocene(Lulehe formation)with lots of fan de-ltas and lake basin development.From Middle Eocene to Late Eocene,the basin deve-loped with a fast speed and came to its peak in Late Eocene.In Oligocene,the basin development slowed down with great number of alluvial fans and fan deltas appearan ce,and finally came to its end with basin filling.3.An analysis of different reservoir physical parameters in different sedimentary faci-es was conducted based on section sedimentary facies analysis and previous research achievements.It is believed that reservoir physical parameter is better in fan delta tha-n in lake,and physical parameter of front sheet sands and underwater branching channel are the best.Because its good porosity and permeability,and gre-at amount of fan delta front appearance,Xiaganchaigou formation in Dongping area belongs to I-A class reservoir.