Subsurface Waters, Upper Cook Inlet, Alaska, Part II - Hydrodynamics

Zhiyong He, Stephen G. Franks

Recent exploration wells have encountered fresh water in the deep (>3000 m) sections of the Cook Inlet basin. A second, more saline water type is also found within the non-marine Tertiary section Given the permeability and sedimentation rate in the Upper Cook Inlet Basin, Genesis 2D models show that meteoric water cannot recharge beyond depths of about 650 m. Over 700 DST records are used to construct fluid flow patterns in the basin. The Results show that fresh waters encountered in deeper parts of the basin are Tertiary depositional waters while the more saline waters are from the underlying Mesozoic sections. The interpreted fluid flow patterns from pressure data show that the distribution of pressures is controlled by distribution of sedimentary facies and compacti n. The pressure compartment described in Hunt (1991) for the Cook Inlet basin does not explain the pressure data. This more detailed analysis of distribution of pressures in the basin shows that compaction disequilibrium is responsible for the over pressures observed.

The interpreted fluid flow patterns a) explains the distribution of the different water types, b) suggests migration fairways for both oil and water, and c) is also compatible with interpretations, based on petroleum geochemistry, of a Mesozoic oil source.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995