Pore Type Analysis Using Bore Hole Electrical Images with New Sonic and Dielectric Measurements
Mohamed Watfa, Roy Nurmi
In carbonates and some complex sandstone reservoirs the determination of pore types is critical for an accurate reservoir analysis (saturation, permeability, effective porosity, producibility). Until recently, it has been necessary to retrieve rock samples of a reservoir formation to determine which types of pores are present. However, a well-log approach has been developed which permits both the recognition and quantitative interpretation of pore types. The approach is an integration of the newly developed electrical bore-hole imagery with dielectric and sonic measurements, geological sequence modeling, and a thorough formation evaluation analysis. This approach permits routine mapping of pore types and their respective volumes within reservoir zones.
The reservoirs studied have included carbonates and sandstones with complex pore systems (mixtures of both primary and secondary pore types) in the San Andres and Smackover Formations in the U.S.A. and the Pre-Khuff, Khuff, Arab, Shuaiba, and Mishrif formations on the Arabian Peninsula.
The analysis of electrical images and Archie
equation exponent m variations
in common carbonate depositional sequences generally permit the interpretation
of both rock and pore types. The electrical images allow a direct analysis of
rock fabric, porosity heterogeneity, and large individual pores such as vugs,
channels, and fracture. Dielectric measurements, combined with more traditional
analysis of porosity and fluid saturations, permit a level-by-level calculation
of the exponent m, which is valuable in analyzing the smaller but more abundant
pores, whereas the dielectric and sonic (shear, compressional, Stoneley) data
provide additional quantification of pore types when related to total pore
volume.
AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.