采油速度影响因素及理论值研究

Research on Influence Factors and Theoretical Value on Recovery Rate

采油速度是决定油田开发效果好坏的重要开发指标之一,采油速度太高或者太低都将影响油田的最终开发效果,因此研究理论采油速度及影响因素对于油田生产决策至关重要。前人主要基于油藏数值模拟及数理统计方法来研究油藏采油速度,但是无论在理论还是应用角度上都存在一定的局限性。基于含水率分流方程,建立了采油速度与油藏属性、含水率及含水上升速度之间的关系表达式,分析了各因素对采油速度的影响。理论分析表明,油水相对渗透率比值与含水饱和度之间回归的系数b值对采油速度为负相关影响;对于含水率,当fw<50%时为负相关影响,当fw>50%时为正相关影响;而不同含水率阶段,含水上升速度越快,则采油速度越大。该方法可用于具体油藏不同开发阶段的理论采油速度的评价。

Recovery rate is one of the key development index which can affect the ultimate development effect of oilfields whether it remains high or low, therefore, the researches of reasonable recovery rate and influence factors play an important role in production decision of oilfields. Previous authors researched the recovery rate mainly based on reservoir numerical simulation and mathematical statistics, however, the certain limitation is both theoretic and applied aspects. Based on the flow fraction equation, we create the relation expression among recovery rate and reservoir properties, water cut and annual ascending velocity of water cut, and analyze the influence of individual factor on recovery rate. The theoretical analysis result shows that coefficient b by regression between ratio of oil to water relative permeability and water saturation is negative correlation to recovery rate. Water cut is negatively correlated to recovery rate when fw〈50%, and positively correlated when fw〉50%. At different stages of water cut, the faster the velocity of water cut ascends, the higher recovery rate could be. The method discussed in this paper could be applied to the evaluation of theoretical recovery rate of certain reservoir at different development stages.