Analysis of Pore Architecture and Correlation to Sonic Velocity Values in Silurian (Niagaran) Reefs of the Michigan Basin
Amy Kathryn Noack1,2 and G. Michael Grammer2
1EOG Resources, Midland, TX
2Michigan Geologic
Repository for Research and Education.
Western Michigan University, Kalamazoo, MI
The relationship between porosity and permeability in carbonate rocks
is complex due to variability in pore type and architecture. Porosity/permeability
transforms are of limited value when evaluating carbonate reservoirs because
permeability is controlled by pore type. Middle Silurian (Niagaran) Reef
reservoirs of the Michigan Basin are being evaluated to better understand pore
types
and related permeabilities. In addition, pore
types
and associated
geometries are thought to have direct correlation with sonic velocity values. As a
result, Niagaran reef wells with both core and sonic logs were evaluated.
Petrophysically significant facies and related pore
types
were identified through
core analysis. Key facies were made into thin sections and photomicrographs
were imported into an image analysis program where pore abundance and
geometries were determined. Facies and related pore geometries were compared
to sonic velocity values to identify the relationship of velocity and pore
architecture. Facies with greater rigidity contain more rounded pores and have
higher velocities whereas facies with less rigidity contain more irregular shaped
pores and have slower velocities.
To confirm the relationship between pore architecture, permeability,
and acoustic impedance, x-ray computerized tomography will be used on key
facies to visualize three-dimensional pore networks. Creating an integrated study
that incorporates evaluation of the relationship of pore types
, facies, and
recognizing the affect of pore geometry and connectivity on rock acoustics,
makes it possible to determine permeability. As a result, understanding rock and
well
log data relationships allows for better prediction of reservoir quality with
logs in the absence of rock data.
AAPG Search and Discovery Article #90089©2009 AAPG Southwest Section Meeting, Midland, Texas, April 26-29, 2009