Hydrous Pyrolysis and Kerogen Conversion

Science Center Objects

Vitrinite suppression/retardation, and the misidentification of solid bitumen as vitrinite, can lead to large variance in measurements of reflectance, cause trends with respect to depth that are difficult to explain by any known geologic phenomena, and cause problems in evaluation of thermal histories and timing of petroleum generation. Accordingly, experimental identification and characterization of the conditions that cause anomalous reflectance values are broadly applicable to the resource assessment process and would be a key improvement to understanding geologic history in petroleum systems worldwide. In addition, identifying in situ differences in the chemical compositions of solid bitumen, vitrinite, and oil-prone kerogen, and correlating the evolution of their reflectance and composition with increasing thermal maturity and/or hydrocarbon expulsion would be a valuable tool in deciphering the chemistry of hydrocarbon generation in unconventional petroleum systems. The USGS is currently working to develop hydrous pyrolysis test to reveal reflectance suppression and to characterize chemical transformation of kerogen conversion to hydrocarbons via microspectroscopy approaches.

Objectives:

  • Build on previous work by Mike Lewan and others, determine maturation kinetics of vitrinite, suppressed vitrinite, and solid bitumen through hydrous pyrolysis experiments
  • Develop a hydrous pyrolysis test to reveal reflectance suppression
  • Characterize the in situ chemical transformation of kerogen conversion to hydrocarbons via microspectroscopy approaches, i.e., micro-FTIR and micro-Raman

Key Findings and Accomplishments

Key Findings:

  • Results from this work showed that the kinetics of solid bitumen maturation are slower than vitrinite, potentially explaining the commonly reported 'vitrinite reflectance suppression' effect as simple misidentification of solid bitumen as vitrinite.

Accomplishments:

  • The significance of this work was recognized with bestowment of the 2018 Ralph Gray Award for Best Refereed Paper in Coal and Organic Petrology from The Society of Organic Petrology.