Analysis Of Factors Affecting Development Effectiveness And Optimization Of Injection Parameters

This article focuses on how to further tap into the potential of water flooding and improve water flooding recovery efficiency in an economically effective manner,considering that high water cut old oil fields are still the main body of China’s crude oil reserves and production,and their production accounts for a significant proportion of the total domestic production.Firstly,the correct evaluation of the remaining recoverable reserves in the reservoir is the foundation for improving the effectiveness of water drive development,and the technology must be further improved,including reservoir description,quantitative characterization of remaining oil,and other aspects;Secondly,it is necessary to adjust the injection production structure,optimize the injection production correspondence between potential layers,expand the coverage range of water flooding,and effectively transform thin and poor oil layers with low utilization levels to achieve precise water injection;Finally,based on the potential of the oil reservoir,key blocks for governance will be selected,and the injection production system will be adjusted according to local conditions to improve the control of water drive reserves and the utilization of thin and poor oil layers,thereby improving water drive recovery efficiency.Taking Block D as an example,a three-dimensional geological model and reservoir numerical model were established,and historical fitting and remaining oil analysis were completed.A study was conducted using orthogonal experimental design to investigate the factors affecting the development effectiveness of two or three types of oil reservoirs,and the injection parameters in the experimental area were adjusted.The final plan was determined to be:step-by-step perforation in the western area and synchronous perforation in the eastern area;The injection strength of Class III sandstone in the eastern area is 5.5m~3/d·m,the injection strength of Class II sandstone in the western area is 4.0m~3/d·m,and the injection strength of Class III sandstone is 5.5m~3/d·m;The injection rate in the eastern area of the experiment is 0.34PV/a,and the injection rate in the western area of the experiment is 0.32PV/a.The simulated production recovery rate for 10 years is 66.78%.The research results indicate that the weight of geological factors affecting the development effect of second and third types of oil reservoirs is in the order of oil layer thickness>permeability gradient>formation rhythm.As the oil layer thickness increases,the gravity differentiation phenomenon within the layer is obvious,and the volume sweep coefficient gradually decreases.For second type oil reservoirs,the smaller the permeability gradient,the better the production effect;The weights of factors affecting the development of Class II oil reservoirs are as follows:crack permeability>crack width>crack half length>crack spacing.The weights of factors affecting the development of Class III oil reservoirs are as follows:crack permeability>crack width>crack spacing>crack half length.The fracturing parameters suitable for Class II oil reservoirs are crack width36mm,crack half length 80m,and crack spacing 100m.Class III oil reservoirs have crack width 38mm,crack spacing 110m,and crack half length 75m.This study has certain guiding significance for improving water drive recovery in high water cut old oilfields.