Abstracts: Permeability-Porosity Relationships in the Midway Sunset Field as a Function of Pore Geometry

BRITTON, ALLEN W., JEFFRY L. SMITH

Permeability and porosity information is fundamental in the evaluation of any reservoir. Use of the classic porosity-permeability crossplot has generally been ineffective as a predictive tool for permeability values due to large amounts of scatter in the data sets. Using pore geometry type as a discriminating tool allows for vastly improved permeability predictions.

Producing horizons in the Midway-Sunset Field exhibit a wide range of porosity and permeability values which are a function of the mineralogical and textural characteristics of the sediment and the flow regime in which the sediment was deposited. The identification of unique pore geometries within these horizons is the key to interpretation of porosity and permeability relationships. While unique pore geometries can be related to depositional facies, they need not coincide with fades boundaries. Therefore, individual facies can be comprised of more than one pore geometry type.

Using a modified Kozeny-Carman relationship a unique term has been derived to describe the pore geometry of conventional core samples. This term, Flow Zone Indicator (FZI), is a function of pore shape, tortuosity and surface area per unit grain volume. Conventional core samples with similar pore geometries will have similar FZI values. Using calculated FZI values, one can zone a porosity-permeability crossplot by pore geometry type resulting in clear porosity-permeability relationships.

Search and Discovery Article #90945©1997 AAPG Pacific Section Meeting, Bakersfield, California