Evaluation And Adjustment Of Waterflooding In H-Block Of Jiyuan Oilfield

H-Block of Jiyuan oilfield is a typical type of the structural and lithological reservoir with low permeability.Waterflooding was adopted to improve oil recovery rate.At present,the average watercut of H-Block is 34.35%,which is still in the development stage of low watercut.Due to the poor physical property of the reservoir and serious heterogeneity,the watercut of some wells rise quickly and the comprehensive recovery rate is low,which causes the development effect to get worse year by year.Therefore,it is necessary to recognize the geological characteristics of reservoir,to evaluate the effect of waterflooding and to work out adjustment strategy to improve the development effect.The sedimentary microfacies research was carried out and the horizontal distribution diagram of sand body was obtained.And then,the effect of waterflooding was evaluated via reservoir method and the decline law of waterflooding was analyzed by the decline curve method.Finally,the reasonable strategy was determined based on the prediction of the development effect of the adjustment strategy by means of numerical simulation.This study provides a guidance for H-Block to work out the adjustment strategy of waterflooding.The results show that Chang 1 is the main oil production formation and develops the subfacies of the delta plain that consists of the distributary channel,the distributary mouth dam,the land natural dike,the final fan,the river and the swamp.The distributary channel among these subfacies is the main oil and gas reservoir area.The dynamical characteristics of this block are the unevenness of the formation pressure distribution and the different response time of producers due to the serious heterogeneity of reservoir and the faultiness of well pattern and the relationship between injectors and producers.The effect of waterflooding control of H-block is well because the degree of waterflooding control is 0.84;while the effect of water drive is poor because the degree of water drive is only 59.37%.The comprehensive watercut of this block is 34.35% at present.However,the volume sweep efficiency is low with a value of 8.9% and the final production recovery is low because the prediction recovery is 22.47%.Finally,the perforations adding and the stimulation measures such as fracturing are determined to adjust the development effect of waterflooding,by which the recovery is predicted using numerical simulation to increase by 2.3% by the end of 2020.Therefore,this study can provide a useful basis for the adjustment of waterflooding strategy and the effect improvement of the waterflooding in H-Block.