Sedimentary characteristics and controlling factors of the Ba 66 fan in Bayindulan Sag

Abstract

Based on the data of core, thin sections, logging and 3D seismic, the sedimentary characteristics, controlling factors and sedimentary model of Ba 66 fan are studied systematically to determine the types and characteristics of the fan.The study shows that Ba 66 fan is a fan delta rapidly deposited by torrent after short-distance transport, and the hydrodynamic force of the fan is mainly driven by gravity.The extension distance of the fan is short on the plane.The fan is lobate as a whole and has the facies feature of " large plain, small front".The main characteristics of the fan are as follows: the maturity of the rock is low, and the disorderly massive glutenite is the typical lithofacies; The fan has the logging characteristics of high amplitude, odonation and abrupt contact.The fan bodies can be divided into plain, front (including proximal, middle and distal), pre-delta or lacustrine facies according to the characteristics of seismic facies, such as random hills, front accumulations, and sheets.The analysis shows that the development of fan delta in the slope belt is mainly controlled by the background environment of the depression and paleogeomorphology: ①The background conditions such as source of uplift area, narrow lake basin (no gentle slope) and wide lake surface ensure the supply of source and short-distance transportation conditions for the formation of fan delta; ②Grooves provide space for sand body development. The slope break changes the slope, divides the accommodation space, and controls the distribution of facies, and the low bulge under the water affects the plane distribution of the fan.Finally, the deposition model of Ba 66 fan is constructed