基于单砂体的特高含水期剩余油精细表征

Fine characterization of remaining oil based on a single sand body in the high water cut period

以葡北油田葡I油组窄、薄砂体特高含水期注水开发油藏为例,提出了基于单砂体的剩余油分布规律、挖潜单元以及相对应的挖潜技术对策。所指单砂体是地质上具有成因联系、开发上相对独立的砂体单元,既是地质上的成因单元,也是与剩余油分布有关的渗流单元,既反映了砂体的沉积成因,也决定了剩余油分布特征和注水开发特征。单砂体成因类型可以划分为多期河道叠加型、分支河道型、单一河道型和席状砂型4个大类;结合注水开发特点,每种类型具有高注高采、高注低采、低注低采和低注高采4种注采方式。剩余油潜力评价的结果表明:多期河道叠加型单砂体潜力最大,剩余油主要为注水下窜型、顶部型、段塞式和欠注型4种类型,可以分别采用厚注薄采、油水井调剖堵水、井网调整和加密井网等措施进行剩余油挖潜;其次是席状砂型单砂体,剩余油表现为"蜂窝状",建议利用注水井调剖和油层压裂来优化注水效果,进行剩余油挖潜。

Taking a narrow and thin sand body, extra-high water cut flooding reservoir of the Pu I oil group in the Pubei oilfield as an example, the distribution law, tapping unit and potential tapping measures of remaining oil were propsed based on a ＂single sand body＂, which referred here is a unit of the same geological genesis and a single sand body relatively independent in waterflood development. In other words, it has a genetic link in geology and forms a percolation unit related with remaining oil distribution, there- fore, it can not only reflect geological genesis of the single sand body but also determine both the distribution and waterflood development characteristics of remaining oil. Types of a single sand body can be divided into four broad categories, including＂multi-stage river channel overlay type＂, ＂branch channel type＂ ,＂single channel type＂ and ＂sheet sand type＂. Based on characteristics of water- flood development, each type has four development effects, i.e. high flooding and high mining, high flooding and low mining, low flooding and low mining, and high flooding and low mining. The potential evaluation of remaining oil demonstrated that the single sand body of multi-stage river channel overlay type has the greatest potential and its remaining oil is mainly characterized by four types, such as＂downward cross flow of injected water＂, ＂top enrichment＂, ＂slugging＂ and ＂under-injection＂, whose tapping measures respectively of remaining oil should be the injection in thick sand while recovery in the thin, water plugging by profile control in oil/water wells, well-pattern adjustment and density increase. Secondly, the sheet single sand body is characterized by a honeycomb distribution of remaining oil, for which the utilization of profile control and formation fracturing is suggested to optimize waterflood effects on trapping measures of the remaining oil.