Reservoir Architecture Anatomy Of Typical Sandy Braided River Reservoir

Braided river sediments are generally "pan-connected" with large grain size,high porosity and permeability,which are important reservoir sand bodies in continental basins,and also one of the hot spots of sedimentary scholars at home and abroad.At present,the production and development of oilfields in our country generally enter the stage of medium and high water cut.It is of great significance to study the internal structure of braided river sand body and the distribution of remaining oil.In recent years,scholars at home and abroad have carried out a lot of research on braided river sediments and put forward many sedimentary models,but the research on braided river reservoir sand body reservoir architecture is not deep enough,its results and understanding are basically in the qualitative or semi-quantitative stage,and it is difficult to study the distribution of remaining oil.Taking L62 formation sandy braided river deposit of Guantao Formation in P oilfield of Bohai as an example,this paper studies the internal structure of sandy braided river reservoir and residual oil distribution by selecting sedimentary model,establishing geological knowledge base by sedimentary analogy,reservoir configuration research and residual oil analysis.Mainly carries on the analysis from the following aspects:Based on the analysis of sedimentary background and basic data in the study area and the previous research results in the oilfield,the sedimentary model of architecture unit of sandy braided river reservoir is selected.The braided river mainly develops braided channel,core beach bar and overbank deposits,which are characterized by braided channel deposits with obvious boundary,and braided channel and heart beach bar are characterized by "wide dam and narrow channel" in plane.Through Google Earth software platform,the geometric shape and size of braided flow zone,braided channel and core beach bar sand bodies of 5-level architecture elements,4-level architecture elements of modern braided river sediments are statistically analyzed.At the same time,the fine anatomical results of Braided River reservoirs in other layers in the study area are measured and counted,and the correlation between different data is established.Geological knowledge base of structural style of braided river reservoir provides guidance and constraints for the description of sand boundary in the next structural anatomy of reservoir,and makes the research of braided river enter the stage of quantitative analysis.Based on the core of "dynamic evolution process analysis" and sedimentary process analysis,using the analytic hierarchy process(AHP)in reservoir research,the sandstone bodies of L62 small sandy braided river reservoir are studied step by step according to "composite braided zone-single braided zone-heart beach bar,braided channel",and a set of methods and processes for the structural anatomy of sandy braided river reservoir are formed.This method not only makes the anatomical results coincide with the single well,but also gives a clear interpretation of the sedimentary process,so it has a higher reliability.On the basis of reservoir structure,according to the seepage mechanism and seepage difference of remaining oil formation,the corresponding relationship between injection and production is analyzed,and the distribution range of remaining oil is predicted.Three types of residual oil are summarized through the analysis of residual distribution law: shielding residual oil in high permeability channel,non-permeability shielding residual oil and low permeability buffer residual oil.