The Buda Formation in the Maverick Basin, South Texas; a Petrophysical Laboratory

Bruce C. Gates

The Buda formation is a 100 – 150 foot thick very fine grained limestone with thin clay interlaminations. Because the thicker carbonate layers are 95% and greater carbonate, petrophysical resistivity measurements are very close to the actual conductivity of the pore fluids. In other words Resistivity ≈ Rt. As a result conventional petrophysics, i.e. Archie’s equation, can be used to accurately calculate water saturation.

In areas where the Buda is at irreducible water saturation (at Ø = 6% then Sw = 20%) bulk volume water calculations from petrophysical logs can be used to estimate permeability variations both vertically and laterally. Thin sections, SEM, capillary pressure data, among the information derived from whole core and calibrated to the petrophysical data indicates that grain size is the main driver to the permeability variations. 

The evaluation not only reveals where the Buda is adequately saturated with hydrocarbons, but also indicates relative permeability variations in areas that the Buda is at the defined irreducible water saturation.

ACADEMICS:
    
Bruce Gates received his bachelor and master degrees in geology from the University of Texas at Austin.

PROFESSIONAL:

Mr. Gates’ professional career began in 1987 as a Petroleum Geologist working for Bright & Company, an established family oil and gas exploration and production company. Subsequent to Bright & Company he managed U.S. Enercorp, Ltd for 20 years until he did an ownership restructuring and formed Ageron Energy, LLC in 2015. Throughout his career he has been involved in oil and gas exploration in the tertiary trends along the gulf coast, cretaceous and devonian in the Rockies, and most recently the Austin Chalk, Eagle ford and Buda trends in S. Texas. Mr. Gates has a little knowledge of many things and is an expert on nothing.