Practical Streamline Method for Quantitatively Characterizing Waterflooding in Narrow Channel Reservoirs

In waterflooding development of narrow channel reservoirs, the water cut rises quickly, and the reservoir becomes nearly fully flooded, yet oil recovery remains low. The narrow strip sand body and long-term water injection create a complex oil and water distribution, making it difficult to evaluate the degree of reservoir utilization during waterflooding. This paper establishes a practical streamline method to quantitatively characterize the waterflooding mobilization degree of narrow channel reservoirs. The streamline method, based on the boundary element method, first characterizes the narrow channel reservoir with complex morphologies and calculates the pressure field. Then, the velocity field is determined, and the streamlines are tracked using the Euler method. The characteristic line method is adopted to solve the saturation equation along each streamline, resulting in the overall saturation distribution of the model. Compared to the stream-tube and numerical simulation methods, the practical streamline method has several advantages, including the automatic generation of flow paths, low calculation dimensions, fast calculation speed, and high calculation accuracy. The method accurately describes the complex boundaries of the channel, realizes the quantitative characterization of waterflooding mobilization degree partitioning, and clarifies the streamline patterns and oil-water flow processes. Finally, the method was applied to a typical narrow channel reservoir to quantitatively evaluate the waterflooding mobilization degree of a well group, resulting in reasonable development and adjustment suggestions. These findings provide guidance for development adjustments in similar types of narrow channel reservoirs.