中低渗油藏极限井距及波及系数变化规律研究

Study on the limit spacing and sweep efficiency variation patternin medium and low permeability reservoir

注入水有效驱替是提高油田注水开发效果和最终采收率的核心。基于稳定渗流模型,建立了考虑启动压力梯度和储层应力敏感的极限半径公式,并结合油藏数值模拟方法,研究了多层合采油藏不同井距波及系数变化规律,首次明确了渗透率级差、注采井距和波及系数的关系。结果表明,启动压力梯度对极限半径影响较大,对部分中低渗储层的影响不能忽略。对于多层合采油藏,受渗透率级差影响,井距对注入水波及系数存在较大影响。缩小井距可以有效提高中低渗油藏波及系数,确保注水有效性,提高油田采收率。现场应用效果良好,可为油田加密调整提供借鉴与参考。

For medium and low permeability reservoirs,establishing effective displacement can improve the development effect of water injection and ultimate recovery.Based on the stable seepage model,the limit radius formula considering start-up pressure gradient and reservoir stress sensitivity is established,and combined with reservoir numerical simulation method,the variation pattern of sweep efficiency with different well spacing is studied.The relationship between permeability difference,injection-production well spacing and sweep efficiency is defined for the first time.The results show that the start-up pressure gradient has a great influence on the limit radius,which cannot be ignored for some medium and low permeability reservoirs.For multi-layer co-production reservoirs,the initial sweep efficiency and the final sweep efficiency differ greatly under the influence of permeability difference.Reducing well spacing can effectively improve sweep efficiency of medium and low permeability reservoir and ensure water injection efficiency,which finally improve oil recovery.Based on the research results,the oilfield infill adjustment is guided and better results are achieved,which provides reference for oilfield encryuption adjustment.