Chapter from:
AAPG Memoir 70: Abnormal Pressures in Hydrocarbon Environments
Edited by B.E. Law, G.F. Ulmishek, and V.I. Slavin
Copyright ©1998 by The American Association of Petroleum Geologists. All rights
reserved.
Memoir 70, Chapter 4: Shale Porosities from
Well Logs on Haltenbanken (Offshore Mid-Norway) Show No Influence of Overpressuring, by C.
Hermanrud, L. Wensaas, G.M.G. Teige, H.M.
Nordgard Bolas, S. Hansen, and E. Vik, Pages 65 - 85
Chapter 4
Shale Porosities from Well Logs on Haltenbanken (Offshore
Mid-Norway) Show No Influence of Overpressuring
C. Hermanrud
L. Wensaas
G.M.G. Teige
H.M. Nordgard Bolas
S. Hansen
Statoil Research Centre, Trondheim, Norway
E. Vik1
Geologisk Institut, Arhus Universitet, Denmark
1Present
Affiliation: Norsk Hydro, E&P Research Centre, Bergen, Norway
Abstract
Fluid pressure detection and porosity evaluation from well logs are largely based
on an assumed relationship between high fluid pressures and high porosities due to
undercompaction. However, few data have been presented which demonstrate to what extent
porosities are higher in overpressured than in normally pressured shales of similar type,
and how this porosity difference is detected by the responses from standard logs. Jurassic
intra-reservoir shales on Haltenbanken (offshore mid-Norway) are particularly well-suited
for such an investigation because (a) the area is subdivided into two, major, distinctive
pressure regimes (one normally pressured, the other highly overpressured) and (b) the
lithology, depositional environment and present burial depth do not vary significantly
across the area.
