The Estimation of Reservoir Pore Volume from Tracer Data

Abstract

Two methods for estimating the pore volume of a
geothermal reservoir based upon tracer return-curve
data are demonstrated. The first method uses a first-moment
analysis of tracer return-curve data. It
calculates the volume swept by a tracer between an
injection region and a production region. For
reservoirs with multiple regions of injection and
production, the respective interwell volumes are
calculated and simply added together to obtain an
overall reservoir pore volume. The second method of
estimating reservoir pore volume involves an analysis
of the long tailing portion of a tracer return curve.
Tracer data from the Beowawe, NV and Dixie
Valley, NV geothermal reservoirs were analyzed by
the two methods and compared. A numerical
simulation study was conducted in order to
investigate the effect of interwell spacing on
calculated volumes and to compare reservoir pore
volumes calculated by the two methods. Application
of both methods may serve to indicate the relative
magnitude of an untapped resource adjacent to the
exploited reservoir volume.