Page 116 - Principles of Applied Reservoir Simulation 2E

Part II: Reservoir Simulation 101

field. In practice, the frequency of model updates depends on the importance
of the resource being modeled to the enterprise.

11.3 Geostatistical Case Study

The process of characterizing a reservoir in a format that is suitable for
use in a reservoir simulator begins with the gathering of data at control points
such as wells. Once this occurs, the data can be contoured and digitized. The
resulting set of digitized maps becomes part of the input data set for a reservoir
simulator.
The contouring step in the process outlined above is changing. Contouring
is the step in which reservoir parameters such as thickness and porosity are
spatially distributed. The spatial distribution of reservoir parameters is a
fundamental aspect of the reservoir characterization process. Two methods for
spatially distributing reservoir parameters are emerging: geostatistics and
reservoir geophysics.
Many modelers view geostatistics as the method of choice for sophisti-
cated reservoir flow modeling [for example, see Lieber, 1996; Haldorsen and
Damsieth, 1993; and Rossini, et al, 1994], even though the resulting reservoir
characterization is statistical. By contrast, information obtained from reservoir
geophysics is improving our ability to "see" between wells in a deterministic
sense. Are these methods competing or complementary? This section presents
a case study that demonstrates several points about geostatistics. A reservoir
geophysical case study is presented in the next chapter. A review of these studies
can help you decide whether either method is appropriate for a particular
application.
An example of a ftill field model study using a geostatistical reservoir
realization is the reservoir management study of the N.E. Nash Unit in Oklahoma
[Fanchi, et al., 1996]. The goal of the study was to prepare a full field reservoir
model that could be used to identify unswept parts of the field. We knew, based
on the history of the field, that water was breaking through at several wells. The
study was designed to look for places where an additional production well could
be economically drilled.