The Impact of Primary and Effective Porosities on the Permeability of the Kurra Chine Formation Successions (Late Triassic) in Selected Wells - Northern Iraq

Abstract

This paper highlights of calculating the permeability by using primary and secondary
porosities for carbonate successions of Kurra Chine Formation in Ain Zalah-29, Butmah-
15, and Alan-1 wells. It has been based on a relatively modern method specially designed
for carbonate rocks which proposed by Lucia (1995). Rather than dependence on the
porosity and water saturation values in calculating permeability, this method uses the rock
fabric and its relationship to the primary porosity that calculated from the sonic log. Since
the sonic log only senses porosity between the interparticle, the presence of a percentage
of the vuggy porosity may lead to inaccurate results. Where the permeability is affected by
the size, distribution, and interconnection of pores more than by the total porosity values
of the rock. Therefore, the current research is suggested to evaluate the permeability the
use of the effective porosity that calculated from the neutron and density logs instead of
the primary porosity (interparticles) that calculated from the sonic log. It appears from
comparing the results for both permeability curves (i.e. that was calculated from the
primary and effective porosities) that there is a clear contrast in the limestone rocks of
Kurra Chine Formation, especially those rich with vuggy porosity. The reason for this is
that many of these pores are connected to each other by micro-channels that was formed
by dolomitization of the surrounding matrix as in Butmah well or as a result of
recrystallization as in Ain Zalah and Alan wells. While the dolomitic rocks have
convergent permeability values because the intercrystalline porosity are the basic pores in
these rocks.