Petroleum Geochemistry of the Cenomanian–Turonian Eagle Ford Oils of South Texas

Measurement of compound‐specific carbon isotope ratios (δ13C values) via direct injection of whole crude oil samples

“…Figure shows the light n‐ alkane and toluene/benzene results from a series of samples collected from the Eagle Ford Oils in South Texas, USA. Previous geochemical studies of these samples (including API gravity, GC/MS of whole oil, δ 13 C values of isolated saturate and aromatic fractions, etc.) indicated that there was a maturity trend across the region (SW to NE).…”

“…(A)). These oils were selected for this study due to the considerable amount of geochemical information which already exists for them and because the maturity trend in the five samples selected is well established. As such, these oils are ideal for comparing the established geochemistry and thermal history with the compound‐specific isotope results (Fig.…”

“…(B) Plot of δ 13 C results for C15+ saturate and aromatic fractions on the Eagle Ford Oils with the defined maturity trend shown. All samples fall below the Sofer Line and are marine in origin …”

“…All the whole crude oil samples were also spiked with the in‐house hexene and octadecene standards (which eluted immediately prior to the n‐ C 6 and n‐ C 18 peaks in the whole oils) as an internal check on the reproducibility of the results. Compounds in the GC/IRMS chromatograms were identified by comparison with the previously reported whole crude GC results and the GeoMark library (GeoMark Research, Houston, TX, USA) of known oil peaks. IonOS software (Isoprime Ltd) was used to process GC/IRMS data; ‘peak mapping’ functionality was used to systematically designate specific analyte compounds across multiple injections for robust data collation across a large number of target peaks within complex chromatograms.…”

Resolved stress analysis, failure mode, and fault-controlled fluid conduits in low-permeability strata

“…The Cretaceous Eagle Ford Formation has become an important self-sourced unconventional oil and gas reservoir in south Texas, U.S.A. (Robinson, 1997;Martin et al, 2011;Cusack et al, 2010;Bodziak et al, 2014;Breyer et al, 2016), and an organic rich source rock for migrated oil produced out of other formations including the directly overlying Austin Chalk and underlying Buda Limestone (Edman and Pitman, 2010;Zumberge et al, 2016;Kornacki, 2018). In up-dip regions closer to the Eagle Ford outcrop belt along the Balcones fault zone, the Eagle Ford is an aquitard that forms a barrier to 55 communication between aquifers including the overlying Austin Chalk, underlying Buda Limestone, and the deeper Edwards Aquifer (Livingston et al, 1936;Maclay and Small, 1983;Maclay, 1989;Ferrill et al, 2004Ferrill et al, , 2019b.…”