水驱油田产量演变模式与开发阶段划分方法

Production evolution patterns and development stage division of waterflooding oilfields

考虑到注水开发油田可采储量不断增长对产量演变规律产生重大影响,对广义“翁旋回”模型进行了改进,建立了新的产量演变模型,明确了产量递减期与储采失衡的统计对应关系,研究了含水率与可采储量采出程度对应关系,为油田开发阶段划分与老油田定义提供了定量的油藏工程依据。中国东部油田开发统计数据表明,储采平衡系数陡然降低至小于1的年限与产量开始出现递减的年限具有较好的匹配关系,其陡降起始点可以作为递减期起始点。研究表明,在高含水阶段,含水率与可采储量采出程度具有良好的统计学意义上的匹配性,将递减期起始点与含水率90%(或可采储量采出程度80%)“双标准”作为老油田的判据更为合理。产量演变模式可以概括为产量上升—峰值稳产—台阶递减、产量上升—台阶稳产—台阶递减、产量上升—台阶稳产—快速递减、产量上升—峰值稳产—快速递减和产量上升—持续递减等5种模式。

The continuous growth of recoverable reserves in a waterflooding oilfield has a significant impact on the patterns of production evolution.A new production evolution model is established by improving the Weng Cycle model.With the new model,the statistical correspondence between the production decline stage and the reserve-production imbalance is clarified,and the correlation of water cut with the recovery percent of recoverable reserves is discussed,providing quantitative basis of reservoir engineering for dividing development stages of oilfield and defining mature oilfields.According to the statistics of oilfields in eastern China,the time point corresponding to the reserve-production balance coefficient dropping to less than 1 dramatically is well correlated the beginning point of production decline,thus the time when the reserve-production balance coefficient drops dramatically can be taken as the initiation point of production decline stage.The research results show that the water cut and the recovery percent of recoverable reserves have a good statistical match in the high water cut stage,and it is more rational to take both the start point of production decline stage and the water cut of 90%(or the recovery percent of recoverable reserves of 80%)as the critical criteria for defining a mature oilfield.Five production evolution patterns can be summarized as follows:growth–peak plateau–stepped decline,growth–stepped stabilizing–stepped decline,growth–stepped stabilizing–rapid decline,growth–peak plateau–rapid decline,and growth–continuous decline.