| At present,block G has entered the late stage of high water cut,with poor water drive development effect and low recovery degree.There are two specific manifestations:first,the well pattern has low control over the reservoir;second,it is difficult to tap the potential of water drive.It is difficult to tap the potential with the conventional water drive method,and the remaining oil in the thick reservoir can be further excavated with the method of polymer injection.In the actual production,many factors will affect the oil displacement effect of polymer.This paper mainly considers the slug size,injection speed,polymer concentration,polymer dosage and slug combination,applies reservoir numerical simulation technology to predict the development effect of block g,and selects a reasonable polymer injection scheme through score analysis,so as to achieve better development effect and economic benefits,The research results provide technical support and scientific guarantee for the formulation of polymer flooding scheme in block g,and better guide the implementation of field polymer flooding test.Therefore,firstly,this paper applies petrel software to establish the phase controlled geological model of block G,including porosity,permeability,saturation and effective thickness model.Eclipse numerical simulation software is used to fit the history of water drive stage.By the end of August 2021,the actual cumulative oil production is 8.74×10~4t,and the calculated cumulative oil production is 9.09×10~4t,the relative error is 4.01%,less than 5%,the actual recovery degree of the block is 39.48%,the calculated recovery degree is39.25%,the absolute error is 0.23%,the actual comprehensive water cut in the simulation area is 97.41%,the calculated comprehensive water cut is 97.10%,and the average fitting error of water drive comprehensive water cut is 0.48%,all of which meet the requirements of fitting accuracy.On the basis of historical fitting,the remaining oil reserves of each layer are predicted,the distribution of remaining oil is studied,and the distribution map of remaining oil saturation is given.Based on the above research results,firstly,13 different development schemes were designed to optimize the injection rate,polymer dosage and polymer concentration of 7 million molecular weight salt resistant polymer;Then consider the case of step concentration reduction slug combined polymer flooding,high concentration polymer blocks the high permeability layer,and low and medium concentration polymer can better displace the remaining oil in the low and medium permeability layer.Then,3 different development schemes are designed for 7 million molecular weight salt resistant polymer.According to the numerical simulation results,through the analysis and Research on the development effect and economic benefit,scheme 14 is determined to be a reasonable scheme of different slug combined polymer flooding,That is,the injection volume of the first section is 0.025 PV,the injection speed is 0.08 PV/a,the injection concentration is 1200 mg/L,the injection volume of the second section is 0.375 PV,the injection speed is 0.10 PV/a,the injection concentration is 1000mg/L,the injection volume of the third section is 0.24 PV,the injection speed is 0.08 PV/a,the injection concentration is 800 mg/L,the polymer flooding in the test area is to the end of January 2029,and the subsequent water flooding is to the end of November 2031.The water content in the test area is 98%,the lowest point of water content is89.99%,and the stage recovery degree is 9.15%,It is predicted that the recovery factor of polymer flooding is 48.40%,and the economic benefit is the best.Compared with conventional water flooding,the enhanced recovery factor is 8.23%,and the cumulative oil increase is 37.13×10~4t. |
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