一种非均质油藏高含水期调堵效果的简易测算方法

Simple calculation method for water plugging effect of heterogeneous reservoirs during high water cut stage

具有优势水侵通道的注水开发油藏在油井高含水期仍存在大量剩余油,可通过对水淹大孔道的调堵,实现对该类油藏的挖潜。然而,目前仍难以定量描述和表征注采井之间的大孔道对注水开发的影响情况,因此对调堵效果的预测具有较大的不确定性。文中将注采井之间的油藏流动区域视为相对均质的油藏与大孔道的并联,分别采用渗流和管流模型计算油井的无因次采液指数与含水率,通过生产数据的拟合,建立快速测算图版,确定大孔道的等效孔径,进而计算大孔道封堵后油藏的流动能力及油井再次达到特高含水期的驱油效率。实例分析表明,该方法所需参数较少,能够实现非均质油藏大孔道调堵效果的快速测算。

A large amount of oil remains in heterogeneous reservoirs during high water cut and water flooding stage. Oil development can be facilitated by plugging the flooded channels. However, it is difficult to characterize the channel path between the injection and production wells as well as the effects of flooding; great uncertainty exists for the prediction of plugging effect. This paper presents a parallel flow model for the region between the injection and production wells, which is characterized as a homogeneous reservoir and a channel path with infinite conductivity. The development index is calculated from seepage and pipe flow. Subsequently, the equivalent radius of the channel path is determined by fitting historical production data. Finally, the flow capacity of the reservoir and the oil recovery efficiency are calculated before and after channel path blocking when the high water cut stage is reached. A case study of a fault block reservoir in the eastern part of China shows that this method requires few parameters and can quickly forecast the plugging effect in heterogeneous reservoirs with water flooding.