Page 105 - Principles of Applied Reservoir Simulation 2E

90 Principles of Applied Reservoir Simulation

10.2 Prerequisites

Several prerequisites should be satisfied before a model study is under-
taken [Coats, 1969]. The most important, from a business perspective, is the
existence of a problem of economic importance. At the very least, the objectives
of a model study should yield a solution to the economically important problem,
Once the objectives of a study are specified, the modeler should gather
all available data and reports relating to the field. The term "modeler" is used
in the remainder of the text as a synonym for "modeling team" unless an explicit
distinction must be made. If necessary data is not available, the modeler should
determine if the data can be obtained, either by analogy with other reservoirs
or by correlation. Values for all model input data must be obtained because the
simulator will not run without a complete set of data. In some cases, simplifying
assumptions about the reservoir may have to be made because there is not
enough data available to quantitatively represent the system in greater detail,
In addition to clearly defined objectives, another prerequisite that must
be satisfied before committing to a simulation study is to determine that the
objectives of the study cannot be achieved using simpler techniques. If less
expensive techniques, such as decline curve analysis or the Buckley-Leverett
waterflood displacement algorithm [Collins, 1961; Craig, 1971; and Dake, 1978],
do not provide adequate results, then more sophisticated and costly methods are
justified.

10.3 Computer Modeling

A comprehensive reservoir management model can be thought of as four
interacting models: the reservoir model, the well model, the wellbore model, and
the surface model. The spatial relationship between these models is illustrated
in Figure 10-1. The reservoir model represents fluid flow within the reservoir.
The reservoir is modeled by subdividing the reservoir volume into an array, or
grid, of smaller volume elements (Figure 10-2). Many names are used to denote
the individual volume elements: for example, gridblock, cell, or node. The set
of all volume elements is known by such names as grid or mesh.