ABSTRACT: Prediction of Reservoir Quality and Porosity Basement in Sandstones of the Pakawau and Kapuni Groups, Taranaki Basin, New Zealand--Preliminary Results

S. Bloch, K. P. Helmold

Vitrinite reflectance porosity and porosity permeability relationships were established in 12 wells during a preliminary investigation of arkosic sandstones of the Pakawau and Kapuni groups (Late Cretaceous through Eocene) in the Taranaki basin of New Zealand. These relationships were used in conjunction with geohistory analysis to determine the economic basement and to predict porosity and permeability in the sandstones prior to drilling.

Medium- to coarse-grained Kapuni and Pakawau sandstones, at vitrinite reflectance values of 0.65-0.70% R_o and higher, are not expected to have porosities and permeabilities greater than 10% and 1 md, respectively. Results obtained from a subsequently drilled well confirmed the validity of this approach.

Meaningful reservoir quality predictions can be obtained only if (1) the lithological characteristics of the sandstones are accurately predicted from facies analysis, (2) the realistic input parameters, based on seismic stratigraphy and regional geologic interpretations, are used in basin modeling, and (3) the sandstones were not affected by hydrothermal activity associated with regional volcanism.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990