Organic petrography of Leonardian (Wolfcamp A) mudrocks and carbonates, Midland Basin, Texas: The fate of oil-prone sedimentary organic matter in the oil window

Evaluation of Shale Source Rocks and Clay Mineral Diagenesis in the Permian Basin, USA: Inferences on Basin Thermal Maturity and Source Rock Potential

“…Furthermore, Tmax values stay rather consistent throughout the stratigraphic interval uniformly, further indicating early to middle oil conditions and maturation due to loss of HI (Figure 12). Tmax from Rock-Eval pyrolysis along with OM petrography have been used to develop empirical formulas for calculating %Ro for when more sufficient data is unavailable [30,43,85]. Additionally, peak burial temperature equations have also been established using %Ro [85] to provide useful tools for insights into the thermal evolution and source rock generation potential of different lithofacies and sedimentary basins for oil and gas exploration [20,24].…”

“…Additionally, peak burial temperature equations have also been established using %Ro [85] to provide useful tools for insights into the thermal evolution and source rock generation potential of different lithofacies and sedimentary basins for oil and gas exploration [20,24]. Jarvie, 2018 [84] developed an equation for calculated %Ro (calculated %Ro = (0.0165 × Tmax) − 6.5143) using Rock-Eval pyrolysis data sets from the Barnett Formation Tmax from Rock-Eval pyrolysis along with OM petrography have been used to develop empirical formulas for calculating %R o for when more sufficient data is unavailable [30,43,85]. Additionally, peak burial temperature equations have also been established using %R o [85] to provide useful tools for insights into the thermal evolution and source rock generation potential of different lithofacies and sedimentary basins for oil and gas exploration [20,24].…”

“…However, Tmax must be cautiously considered as a thermal maturity indicator due to factors, such as (i) small amount of organic matter in the sample, (ii) deterioration of organic matter, and (iii) varying types of organic matter at the maximum of their thermal maturity [22][23][24][25][26]. Vitrinite reflectance (%R o ) observations through organic petrography, especially in shale, has become the standard evaluation tool for thermal maturity [27][28][29][30][31]. Vitrinite reflectance is useful due to its systematic increase with increased organic matter maturation and burial depths as well as preferred arrangements in structure due to overlying stress from load pressure [27].…”

“…However, %R o interpretations can be time consuming, relying heavily on the experience of the organic petrographer [29]. Calculated vitrinite reflectance conversion values using Rock-Eval pyrolysis data have been theoretically developed for several source rocks within a number of sedimentary basins [23,30] and can be further adjusted with the incorporation of mineral maturation indices [31].…”

“…The ability to constrain different maturation techniques at times in which only some data are available or when techniques must be modified (calculated %R o by Rock-Eval pyrolysis [30,31]) can prove helpful during the development of unconventional shale reservoirs. The Wolfcamp, and to a lesser extent Barnett, unconventional shale plays within the Midland Basin, a small sub-basin of the Permian Basin, are some of the largest producing shale plays in the world [39].…”