Study On Sedimentary Facies Of Bi304 Block In Zhaoao Oilfield

Biyang depression is one of the typical Cenozoic oil-rich depressions developed in the Qinling fold belt,The area is small,only 1000km²,and the resource abundance is good.The Bi-304 block in the study area is located in the south of Biyang depression and mainly distributed in the southern steep slope belt.In order to further fine reservoir research and efficient exploration and development,it is necessary to conduct in-depth research on the sedimentary distribution characteristics of the first and second sections of the core in the Bi-304 block.In this paper,the comprehensive utilization of high resolution sequence stratigraphy,well logging curves combining with core facies analysis technique,the types of sedimentary facies and sedimentary characteristics of study on the system research,on the basis of the representatives has been clear about the location in the vertical change of lithology and feature,and on this basis,it is concluded that the single well logging characteristics,sedimentary facies and sedimentary distribution characteristics,summarizes the sedimentary facies model,the objective interval in Bi-304 block in the studied area sedimentary evolution are expounded.The comprehensive analysis includes sedimentary facies markers such as rock color,grain size,sedimentary structure and logging curve response characteristics,so as to determine the sedimentary characteristics of different sedimentary facies and logging curve response characteristics,as well as the types of single well sedimentary facies.At the same time,combining with stratigraphic correlation division,single well logging facies analysis,profile facies analysis,sedimentary sand body distribution analysis and sedimentary distribution analysis,it is determined that H₁-H₂ in Bi304section is underwater-fan.Four sedimentary microfacies,including braided channel,interchannel and channel edge,front fan diffuse current and fan end,were mainly developed.The lithology of braided channel is mainly sandy conglomerate and mostly block stratification;The lithology of the interchannel and the edge of the channel includes mudstone,argillaceous siltstone and argillaceous fine sandstone,and the sedimentary structures such as horizontal bedding and parallel bedding are developed;The lithography of the diffuse microfacies in front of the fan includes mud-fine sandstone,mud-siltstone and mud-fine sandstone,which develop sedimentary structures of parallel bedding and sand-grain cross-bedding;The petrology of fanduan lacustrine facies is dark gray and gray mudstone,mudstone siltstone and silty mudstone.The sedimentary structure is characterized by the development of horizontal bedding and block bedding.By means of core-logging-geology comprehensive research and analysis,the sand body thickness values of each small layer were read.By means of the analysis of the thickness isolines of each small layer of H₁-H₂ oil group with coring well constraints,the plane distribution rules of each small layer of H₁-H₂ sand body in the section of Bi-304 were defined,and the sedimentary evolution in the study area was further analyzed.Based on the above research,the following conclusions are drawn:the lithology of the reservoir in Bi-304 area is complex,coarse and varied.The study area is located in the phase zone from the leading edge of the underwater fan to the end of the fan,and braided channel,interchannel and the edge of the channel,the diffusive flow in front of the fan,and the lake facies at the end of the fan are developed.From the object source to the lake basin,the distribution of sedimentary facies is braided channel?between and at the edge of the channel?-fan front diffuse-fan end lacustrine facies.In the longitudinal evolution,the sedimentary development of the target interval in the study area has experienced three periodic changes from progressive to regressive.According to the analysis of lateral evolution,there are three major provenance systems:south provenance,south provenance and south east provenance.