Study On Genetic Model And Potential Tapping Method Of Remaining Oil In L Oilfield

After the waterflooding oilfield enters the"double high"stage of high water cut and high recovery degree,the remaining oil shows the characteristics of"overall high dispersion and local relative enrichment".The main controlling factors of remaining oil are unclear and the distribution of remaining oil is unknown.The situation of adjusting and tapping potential is becoming more and more serious.Based on L oilfield,this paper uses three methods:three-dimensional physical simulation experiment,reservoir engineering and numerical simulation to summarize the enrichment law of remaining oil,determine the genetic model of remaining oil,give the reserves of the remaining oil enrichment area,and put forward efficient potential tapping schemes.Taking full account of the gravity effect of thick oil layers,large-scale three-dimensional physical simulation experiments are used to analyze and summarize the remaining oil enrichment laws in different development stages of early polymer injection thick oil reservoirs under the influence of rhythm,permeability ratio,distribution and scale of impermeable strata and intercalated beds,reservoir thickness,water injection rate and well pattern change.The remaining oil is mainly concentrated in the high positions and low permeability layers near the production well end.With the increase of permeability ratio,the larger the remaining oil enrichment area is,the higher remaining oil the enrichment degree is.The impermeable strata and intercalated beds play a certain role in controlling the distribution of remaining oil,and a certain amount of remaining oil is enriched in its lower part.With the increase of water injection rate,the remaining oil enrichment area gradually transits from the top of the model near the production well end to the model production well end.With the change of well pattern,the enrichment form of remaining oil changes from"similar to diamond"to"chessboard line".Reservoir thickness has little effect on remaining oil enrichment.Using the reservoir engineering method,taking time as the main line,the formation coefficient,distribution position and connectivity are considered in the plane,and the relationship between recovery degree and oil-water relative permeability,stimulation measures and their validity period are considered in the vertical.The oil and water production are distributed and calculated to the direction and small layers step by step.A set of mathematical models for qualitative and quantitative evaluation and calculation of remaining oil potential are deduced and established.The calculation results are verified by production test profiles,and the accuracy can reach 90.56%,with high coincidence.The remaining oil is distributed in an inverted triangle as a whole.The higher the enrichment degree of the remaining oil,the lower the water flooding degree and the higher the recovery degree towards the upper part of the reservoir.The remaining reserves of II-1 are 892×10~4m~3,accounting for 34.46%.However,each small layer is dominated by strong water flooding,accounting for 83.33%,and there are no non-waterflooding and low-waterflooding layers.Based on logging,seismic,well completion,core,production performance and other data,the numerical model is established and the history fitting is completed.The remaining oil enrichment areas are searched according to well areas and sublayers.Seven genetic models of remaining oil are determined,including remaining oil in gas cap areas with low development degree,remaining oil in imperfect injection and production areas,remaining oil in fault shielding areas,remaining oil controlled by rhythm and gravity,remaining oil controlled by impermeable strata and intercalated beds,remaining oil of thin and poor layers and remaining oil at the edge.The potential tapping methods of drilling adjustment wells are given respectively.Based on the water cut rise mode,A-type water flooding law curve is selected to predict the recovery of 54.35%.Combined with economic benefits,it is determined that the limit of geological reserves for drilling a new adjustment well is 9.20×10~4m~3.Based on the research results and the potential tapping methods of remaining oil,three potential tapping schemes of remaining oil are designed.Compared with the basic scheme,the average oil increase of single well in different schemes is 6.68×10~4m~3,6.65×10~4m~3,8.00×10~4m~3 respectively,with good development effect.