Thermal Maturity Modeling of Organic-Rich Mudrocks in the Delaware Basin Using Raman Spectroscopy of Carbonaceous Material
Date
2018-08-01
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Abstract
Raman spectroscopy of carbonaceous material (RSCM) is an emerging tool to investigate the peak temperature organic-rich sediments experience during burial and exhumation. Previously, peak temperature and maturity have been commonly determined using vitrinite reflectance (%Ro), but results may be affected by user bias, organic material composition, hydrogen-index, and pressure suppression. Thermal maturity of organic material is an important factor in determining source rock viability, and RSCM presents an alternative technique to constrain peak temperatures that is not affected by issues that may alter %Ro results. This study investigated the viability of RSCM thermometry against %Ro and pyrolysis on well cuttings retrieved from Permian through Ordovician intervals of the Delaware Basin in West Texas, assessing peak temperatures and paleogeothermal gradients. New RSCM results from this study demonstrate that the western portion of the basin experienced higher peak temperatures than equivalent depths in the eastern portion of the basin by up to 100oC, which is consistent with existing vitrinite reflectance measurements. This study also reconstructs the paleogeothermal gradient profile of the basin center by incorporating 11 wells in Reeves and Loving County, including wells which have intersected igneous intrusions. Geothermal gradients at times of peak temperature are 40-45oC/km in the east and up to 72.5oC/km in the west. Higher geothermal gradients in the west correspond to areas with poor agreement between RSCM and vitrinite reflectance. Reconciling the differences between methods requires elevated heat flow, which may
have been supplied by mid-Cenozoic intrusions and regional heat flow associated with the Rio Grande Rift.
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Keywords
Geology, Delaware Basin, Permian Basin, Thermal Maturity, Raman, RSCM, Vitrinite,