3D streamlines with water (blue) displacing oil (red).
The distinguishing feature of streamline simulation is that fluids are transported over a time step (t to t+Δt) along streamlines rather than from cell-to-cell as in conventional FD methods. Anything assumed to move with the total velocity field will follow the streamlines until the velocity field is updated to account for its changing behavior in time. The geometry of the streamlines and the velocity at which components travel along each individual streamline results directly from the spatial distribution of the static petrophysical properties (permeability, porosity, relative permeability regions, etc.) and the volumes produced/injected at the wells. The ability of streamlines to visualize flow is unmistakable, even to the untrained eye.
The most striking advantage of SLS compared to other simulation approaches is the information provided by the streamlines themselves. There are two particularly useful sources of data: first, streamlines can outline the drainage and irrigation volumes associated with producers and injectors respectively. It is possible to know which grid blocks are associated with which well—injector or producer—at any particular time. These regions can be used in well-level assisted history matching workflows to decide how to modify static grid properties in order to improve the match between simulated and historically observed volumes. Another use can be as a metric to establish the effectiveness of upscaling methodologies. The second powerful data source comes from summing the volumetric flow rates associated with all the streamlines connecting an injector/producer pair. Doing so allows determining the well rate allocation factors (WAFs), the percentage of flow from one well to each offset well it communicates with. Streamlines thus offer an attractive solution to the challenging problem of trying to associate produced and injected volumes. Well allocation data is critical to workflows based on pattern analysis and to manage floods effectively.