Page 157 - Principles of Applied Reservoir Simulation 2E

Chapter 15

Fundamentals of Reservoir Simulation

Previous chapters describe much of the data that is needed by a reservoir
simulator. Our goal here is to outline the physical, mathematical and computa-
tional basis of reservoir flow simulation. For a more detailed technical presenta-
tion, consult one of the many sources available in the literature [for example,
see Aziz and Settari, 1979; Bear, 1972; Mattax and Dalton, 1990; Peaceman,
1977; and Thomas, 1982]. The set of equations used in WINB4D is derived in
Chapter 32.

15.1 Conservation Laws

The basic conservation laws of reservoir simulation are the conservation
of mass, energy, and momentum. Mass balance in a representative elementary
volume (REV) or gridblock is achieved by equating the accumulation of mass
in the block with the difference between the mass leaving the block and the mass
entering the block. The set of equations used in WINB4D are derived from the
mass conservation principle in Chapter 4. A material balance is performed for
each block. What makes a simulator different from a reservoir engineering
material balance program is the ability of the simulator to account for flow
between blocks.
A material balance calculation is actually a subset of the simulator cap-
ability. This is an important point because it means a reservoir simulator can be
used to perform material balance work. The advantage of using a simulator
instead of a material balance program is that the simulation model can be

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