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

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.