Page 195 - Principles of Applied Reservoir Simulation 2E

180 Principles of Applied Reservoir Simulation

The seismic history matching process includes steps for incorporating
time-lapse seismic monitoring information. Time-lapse seismic monitoring is
the comparison of two or more 3-D seismic surveys over the same region at
different points in time. WINB4D includes algorithms for providing information
that can facilitate all of the tasks shown in Figure 18-1. This has been made
possible by the inclusion of a petrophysical model in the flow simulator,

18.2 Key History Matching Parameters

A fundamental concept of history matching is the concept of a "hierarchy
of uncertainty." The hierarchy of uncertainty is a ranking of model input data
quality that lets the modeler determine which data is most and least reliable.
Changes to model input data are then constrained by the principle that the least
reliable data should be changed first. The question is: which data are least
reliable?
Data reliability is determined when data are collected and evaluated for
completeness and validity [Raza, 1992; Saleri, et al., 1992]. This is such an
important step in establishing a feel for the data that the modeler should be
closely involved with the review of data. Relative permeability data are typically
placed at the top of the hierarchy of uncertainty because they are modified more
often than other data. Relative permeability curves are often determined from
core floods. As a consequence, the applicability of the final set of curves to the
rest of the modeled region is always in doubt.
Initial fluid volumes may be modified by changing a variety of input
parameters, including relative permeability endpoints and fluid contacts. Model-
calculated, original fluid volumes in place are constrained by independent
techniques like volumetrics and material balance studies.
Attempts to match well data may require changing the producing interval
or the productivity index of a perforation interval. If it is difficult to match well
performance in a zone or set of zones, the modeler needs to look at a variety of
possibilities, including unexpected completion and wellbore problems. In one
study, for example, an unexpectedly high GOR from a perforation interval that
was known to be below the gas-oil contact was due to gas flow in the annulus