Evaluation Of Water Injection Development Effect And Potential Analysis For Qian 3 Reservoir In JZ Oilfield

The JZ oilfield is located in the Qianjiang Sag of the Jianghan Basin,the main oil-bearing formation of JZ oilfield is the Paleogene Qianjiang Formation,which is a medium-porosity and medium-high permeability reservoir.The reservoir is heavily heterogeneous and has many oil-bearing formations.As of December 2018,the comprehensive water cut in the study area is85.72%,which is at the high water cut development stage,problems such as accelerated water content increase and accelerated oil production decline have occurred.This paper takes the Qian 3 section of the study area as an example for water injection development effect evaluation and potential analysis.The reservoir engineering methods were used to analyze and evaluate water injection development effect of the study area and analyze the existing problems in development from five aspects:reserves producing status,formation energy maintenance level,water flooding status,production decline and recovery efficiency.As of December 2018,the recovery percentage of the study area Qian 3 reservoir has reached40.56%,the degree of waterflood reserves control is only 34.6%,the degree of waterflood reserves utilization is 69%,the formation pressure maintenance level remains at 78.4%but tends to decline,and the comprehensive water cut is 88.55%,the water cut increase rate is 5%,the water preservation rate is negative,the water drive index is 0.15,total annual oil production decline rate is 10.44%,These indicators shows the low reserves producing status in the Qian 3section of the study area,low formation energy retention level and low utilization ratio of injecting water,so the water injection development effect is poor,and the oil production declines rapidly.It is necessary to strengthen water injection and improve the well pattern on the basis of the remaining oil distribution in the study area to improve the water flooding effect.Based on the geological data of the study area,the Petrel geological modeling software was used to establish a three-dimensional geological model of the Qian 3 section of the study area.On this basis,the CMG software was used to carry out history matching for reservoir performance and reservoir numerical simulation studing.The study showed that:under the influence of formation structure?faults?reservoir heterogeneity and well pattern,the remaining oil in the study area mainly includes the following 6 types:remaining oil in high structural parts,remaining oil in the interwell zone of the non-mainstream line,remaining oil in the area with imperfect well patterns,remaining oil in the fault surrounding area,and remaining oil in the edge of oil sand body.From a longitudinal perspective,they are mainly distributed in six layers:Qian 3₃¹,Qian 3₃⁴,Qian 3₃⁶,Qian 3₃⁸,Qian 3₄¹,and Qian 3₄⁴,which can be used as the main target for further measures to develop the remaining oil.Taking the Z10Xie-7 well group as an example,the development mechanism remaining oil in the non-mainstream line inter-well zone and imperfect well pattern area were studied.The flow direction of the injecting water was changed by means of perforations adding,producing wells transform to injecting wells and plugging,thereby changing the seepage field,enlarge the water flooding sweep volume to increase the recovery percentage.Combined with the distribution of remaining oil in the main reservoir and the distribution of well positions,adjustment schemes in the study area Qian 3reservoir were formulated:drilling 2 newly producing wells and 3 njecting wells,other methods such as perforations adding,producing wells transform to injecting wells,plugging and fracturing were adopted to form a staggered array of well patterns in each main oil layer.It is predicted that after fifteen years of development,the cumulative oil increase of the study area Qian 3 reservoir will be 250,500 tons,the cumulative increase of recovery percentage will be6.88%.Which is higher than the existing development scheme,cumulative increase oil production 124,300 tons,cumulative increase recovery degree 3.41%,and the water cut is greatly reduced.The study area still has strong potential for remaining oil producing.