Chapter from:
AAPG Memoir 67: Seals, Traps, and the Petroleum System, Edited by R. C.
Surdam
Publication Subject: (Oil Methodology, Concepts)
Memoir 67: Seals, Traps, and the Petroleum System. Appendix: Evaluating Seal Facies Permeability and Fluid
Content from Drill-Stem Test Data, by H.W. Reid, p. 299-312
Copyright © 1997 by The American Association of Petroleum Geologists. All rights reserved
Appendix
Evaluating Seal Facies Permeability and Fluid
Content from Drill-Stem Test Data
H.W. Reid
Hugh W. Reid & Associates, Ltd.
Calgary, Alberta, Canada
ABSTRACT
Many facies assumed to act as seals contain stringers of sand
and silt that are potential low-grade reservoir units. The drill-stem tests (DSTs) from
these formations generally show them to be "tight," but many of the wells in
these "barrier" facies ultimately become commercial producers after completion.
Calculation of the permeability and fluid content of these facies from DSTs has not been a
common practice because the facies often do not produce oil or gas when tested, making
them unattractive to operators, and because the analysis of DSTs from tight formations can
be problematic. However, knowing the permeability of seal facies helps operators determine
which of these "barriers" are the leakiest and, hence, are the best potential
exploration targets. In this study, the shape of the shut-in curve on pressure charts and
other subtle indications are used to more accurately assess the reservoir quality of these
neglected formations. This paper will attempt to demonstrate that a good approximation of
the leakage potential of these facies can be made using published empirical correlations
if the permeability, as from a DST, is known.
