Page 207 - Principles of Applied Reservoir Simulation 2E

192 Principles of Applied Reservoir Simulation

These points underscore the need to recognize that the history match process
does not yield a unique solution. Forecasts of reservoir behavior depend on the
validity of the history match.
Despite the uncertainty associated with simulator-based forecasts,
reservoir simulation continues to be the most reliable method for making
performance predictions, particularly for reservoirs that do not have an extensive
history or for fields that are being considered as candidates for a change in
reservoir management strategy. Other methods, such as decline curve analysis
and material balance analysis, can generate performance forecasts, but not to
the degree of detail provided by a reservoir model study. As Saleri [ 1993] noted,
4 "While a 10% to 40% forecast uncertainty may appear alarming in an
absolute sense, the majority of reservoir engineering decisions require
choices based solely on comparative analyses (for example, peripheral
vs. pattern flood). Thus, in selecting optimum management strategies,
finite-difference models still offer the most effective tools."
Saleri's view is similar to that of Oreskes, et al. [1994], Even though
models are non-unique representations of nature, they still have many uses. In
summary, models can be used to
4 corroborate or refute hypotheses about physical systems;
4 identify discrepancies in other models; and
4 perform sensitivity analyses.
Part IV integrates the ideas presented above in the context of a case study.

Exercises

Exercise 19.1 Data set EXAM4.DAT is a 2D areal model of an undersaturated
oil reservoir undergoing primary depletion. (A) Run EXAM4.DAT and
determine oil recovery at the end of the run. (B) Set the bottomhole pressure
(BMP) in well P-l ofEXAM4.DAT to 150 psia and run the model. How much
oil is recovered in the modified model?

Exercise 19.2 Beginning at the end of year one, add a water injection well in
each of the four corner gridblocks in data set EXAM4.DAT with the BHP