Study On Distribution Characteristics Of Remaining Oil And Optimization Of Polymer Flooding Scheme Of Oil Layer Group B In Block A Of Songliao Basin

The oil layers of B oil layer group in the pure oil area of the development area have all been put into polymer flooding development,and good oil displacement results have been achieved.However,the B oil layer group in Block A of the C transition zone in this development area is in the state of water drive exploitation in the ultra-high water cut stage,with the comprehensive water cut reaching 96.94%.In 2021,258 new wells were drilled to optimize the well pattern in block A.But after the completion of the new wells,research on the sedimentary characteristics and remaining oil distribution characteristics using the new well data has not yet been carried out.The reservoir sedimentation characteristics and the distribution characteristics of reservoir physical properties need to be further understood.After 58 years of water drive development,the remaining oil potential and distribution characteristics need to be further researched and for further tapping the potential the injection parameters of polymer flooding need to be optimized.Taking advantage of the favorable opportunity of well pattern thickening,the logging facies model is established by the comprehensive application of well logging data and coring well data.The identification of single well facies and the analysis of the across well facies are carried out.On this basis,the plane microfacies distribution maps are drawn through the plane microfacies combination.Using 3D geological modeling technology and facies controlled random simulation method,the reservoir geological model of the study area is established to characterize the planar distribution characteristics of permeability,porosity and effective thickness of the B oil layer group in block A.On the basis of three-dimensional facies controlled geological modeling,relying on numerical simulation technology,coring well data,dynamic monitoring data and water flooded layer interpretation data are comprehensively applied to determine the plane and vertical remaining oil distribution characteristics of the target layer in the study area and the main enrichment types of remaining oil.According to the comparison results of numerical multi-plan simulation,combined with the indoor core test results,reservoir engineering methods,and referring to the existing polymer flooding development experience in the development zone,the injection parameters of polymer flooding in oil layer group B of block A in transition zone C are optimized and the development indexes are predicted.The research results show that:(1)The 6 sedimentary units of B oil layer group in block A are divided into 3 types of sedimentation.B2 and B3 are flood plain subfacies and develop meandering river sand bodies;B1 is delta distributary plain subfacies and develops distributary channel sand bodies.And the B4,B5,and B6 are delta front subfacies and develop underwater distributary channel sand bodies.Sand body development and reservoir physical properties of B2 are the best,followed by sand body development and reservoir physical properties of B1,sand body development and reservoir physical properties of B3 and B4 are medium,and sand body development and reservoir physical properties of B5 and B6 are poor.(2)B1～B6 sedimentary units still have a certain potential for tapping,and the current recovery percent is 42.24%.On the plane,there are four types of remaining oil enrichment: remaining oil formed by barrier of abandoned river channel,remaining oil of river channel edge,remaining oil of interfluvial thin and poor layer,and remaining oil formed by incomplete well pattern;Vertically,there is positive rhythm top type remaining oil on the top of positive rhythm channel sand.The B2 and B1 sedimentary units are the main potential layers for remaining oil enrichment,accounting for 67.39% of the total remaining reserves.(3)The final polymer flooding parameters are as follows: The polymer molecular weight of polymer flooding in this block is 12～16 million medium molecular weight;Concentration of polymer solution is 1100mg/L;Polymer dosage is 1500 PV · mg/L;And polymer injection rate is 0.16～0.20PV/a.It is predicted that polymer flooding will improve oil recovery ratio by12.29 percentage points.The research results of the above three aspects have important reference value for guiding the development and adjustment of the B oil layer group in the study area.