Thermal Maturity And Porosity Development During Catagensis In The Barnett Shale, Fort Worth Basin, Texas

Abstract

Unconventional resource plays are typified by significantly recoverable volumes of thermally mature hydrocarbons (oil, condensate and/or gases) trapped within a low permeability shale formation acting as source, reservoir and seal. These systems pose a scientific and engineering challenge to produce recoverable hydrocarbons from, chiefly due to their low permeabilities. There is growing evidence that secondary porosity in organic gas bearing shales is created during the thermal maturation of kerogen. A better understanding of porosity development during maturation of mobile organics during catagenesis may yield new insight on how we view these systems. A comparative analysis of the gas phase(s), peak gas generation and porosity trends could be used as a screening/diagnostic tool for assessing unconventional hydrocarbon systems. By comparing regional formation porosity trends against known variations in basin hydrocarbon maturity a relationship might be established. This study focuses on regional porosity trends in the Barnett Shale of the Fort Worth Basin with respect to constrained variations of known thermal maturity ranges of organic hydrocarbons. Density and neutron porosity well log data from Barnett Shale intervals in selected wells are compared with vitrinite reflectance values and Barnett Shale organic maturation data. The results of this study indicate that there is a low correlation with measured Barnett Shale formation porosity and areas of increased thermal maturity as determined by vitrinite reflectance.