The Quantitative Evaluation Of Water-flooded Zones And Prediction Of Remaining Oil Distribution In F Block

The reservoir in F Block is a layered sandstone reservoir with fault-controlled anticline structure and certain natural water energy,and it has high porosity and high permeability.After producing,the reservoir has long been developed by natural energy.The oil field has entered the mid-high water cut stage,and the edge water and bottom water flooding is widespread.Therefore,it is necessary to carry out quantitative interpretation and evaluation for water flooded zones and prediction of remaining oil distribution in F Block.In this paper,core data,well logging data,and dynamic production data are used to study the relationship among reservoir lithology,physical properties,oiliness,and electrical properties.It was found that the reservoir lithology is mainly medium sand,porosity and permeability are mainly distributed between mid to high,oil-bearing description is almost good,and typical oil zones have characteristics of low shale content,high porosity,high resistivity,low density,and high interval transit time.By comparative analysis of log response characteristics of lithology and physical properties of reservoirs,it can be found that the difference between neutron porosity and density porosity is the best parameter to reflect the variation of shale contents,the formation density log is the best logging response to reflect the variation of porosity,and the porosity is the best parameter to reflect the variation of permeability in the block.On the basis of the results,the methods of calculating the shale content,porosity and permeability of the reservoir are established,and the irreducible water saturation is determined by the J-function method with the measured capillary pressure data.Considering the effect of shale on the conductivity of reservoirs,the Indonesian equation and the effective medium symmetric resistivity equation for high-shaly reservoirs are selected to calculate the water saturation of reservoirs.By comparing the calculated water saturation of the high-shaly oil zone,it is indicated that the calculated saturation from the two equations is better than that from Archie equation.Since the Indonesian equation has the advantages of simple form and a few indetermination parameters,the Indonesian equation is chosen to calculate the water saturation of reservoirs finally.The log data for core analysis wells and flooding wells in the block are processed with the proposed quantitative interpretation method for water-flooded zones.The results show that the precision of the calculated reservoir parameters is accurate and the determined water-flooded grades valid.By combining with the analysis of the production performance of the well and adjacent wells,the quantitative comprehensive evaluation for the flooded zones of 141 wells has been done in the study area.Based on the logging interpretation results of water-flooded zones and combined with dynamic development data,flooding modes and characteristics,remaining oil types,and their main control factors are summarized.In F Block,it can be determined that there are two flooding modes: bottom water propulsion and edge water propulsion: the oil zone is in direct or indirect contact with the water zone in bottom water propulsion mode longitudinally,and water-flooded zones are distributed in a point-like manner on the plane.Water-flooded zones with different flooding degree are unevenly spaced in edge water propulsion mode longitudinally,and flatly distributed on the plane.The degree of development and physical properties of reservoirs are considered as the most important factors influencing the flooding degree.Flooding degree distribution maps for 6 layers are completed.And it is determined that the remaining oil exists in the non-flooded area and the flooded area.Well pattern control degree and physical properties of reservoirs are the most important factors to control the distribution of remaining oil.Remaining oil in the non-flooded area is usually contiguous,with poor well pattern control and large distribution area,and remaining oil in the flooded area is scattered,with poor regularity and small area,which is mainly controlled by the physical properties of reservoirs,and the remaining oil in reservoirs with poor physical properties is enriched.Remaining oil(thickness)distribution prediction maps for 6 layers are given.The research results of this paper can enhance the accuracy of quantitative log evaluation of shaly sand flooded zone in F Block and the accuracy of remaining oil distribution prediction,and will have guiding significance for ensuring the continuous and efficient development of oil fields.