A steam injection reservoir simulator was developed with the objective of improving the resolution of the information concerning the flow around a well and between wells. To accomplish this objective, it was necessary to develop the contiguous hyperhybrid grid refinement method.
With better well region representation, it has been shown that hyperhybrid grid refinement is useful in studying well operating changes and well interactions, particularly when the regions are made contiguous. Local well effects, interwell interference, multiwell cyclic steaming and conversion to steamflood were examined using hyperhybrid grid refinement. The results of these studies are presented in a separate paper.
It is recommended that contiguous hyperhybrid grid refinement be used for analyzing problems where the local well region behavior is important in the context of a field simulation. Furthermore, it is recommended that this refinement technique be used to study interwell interactions where near-well effects are important and the communication path between the wells requires better representation.
At the present time, there are steam injection simulators that may be satisfactory if there are no sharp fronts for steamflood simulation. When it comes to cyclic steaming, simulators are suited best for single well modeling, but multiwell modeling is possible only with difficulties arising from the necessary adjustments of relative permeability, hysteresis, formation compressibility and grid size. Some adjustments may also be required for single wells; however, a radial grid system is better suited for representing a well.
Effective fieldwide cyclic steam stimulation simulation is still in the future, when the next generation computers become available. It is recognized in the industry that computational hardware/software allow for the inclusion of a limited number of wells in a thermal simulator. Recent work1 illustrates this point well-their study contained 4,500 rectangular grids blocks and up to only eight wells. Even at present, a fieldwide cyclic steam stimulation simulation requires a tremendous amount of computer storage and computation time. Yet, such a simulation customarily employs a rectilinear grid that is inadequate for simulating radial flow-an essential flow feature of cyclic steam stimulation-near the wells. In recognition of the fact that the next generation computers are nearby, the objective of this work is to develop a tool that will provide an effective fieldwide simulation. The existence of the next generation computers will not eliminate the need to have radial geometry around the wells.
This is the first model to use hyperhybrid grids in thermal simulation. A hybrid grid is defined as a cylindrical grid system embedded into a single fundamental rectilinear grid block and a hyperhybrid ∗ grid is defined as a cylindrical grid system embedded into several contiguous fundamental rectilinear grid blocks. These grids are illustrated in Figure 1. Regions 1, 3 and 5 are hybrid while Regions 2, 4 and 6 are hyperhybrid grids. In addition, this is the first model, black oil or thermal, to offer hybrid and hyperhybrid grid regions that can be contiguous.