Recognition of Petroleum-bearing Traps by Unusual Isotopic Compositions of Carbonate-cemented Surface Rocks

Structural and diagenetic control of fluid migration and cementation along the Moab fault, Utah

“…Concretionary cement growth around oil nuclei (Figure 3d, e) indicates a strong seed effect for cement nucleation, which can be explained by the localized microbial activity on the oil-water contact of residual oil globules in the porous sandstone, conditions similar to those found in microseeps and oil spills. Donovan (1974) and Donovan et al (1974) described systematic carbon isotopic trends around microseeps, with d 13 C values of carbonate increasing from −40‰ PDB close to the migration conduits to as high as −5‰ PDB at the periphery. A similar zonation in isotopic composition of inorganic carbon dissolved in groundwater surrounding an oil spill was described by Baedecker et al (1993), with d 13 C values ranging from −22‰ to as high as −4‰ PDB within the anoxic zone surrounding the spill.…”

“…Carbonate cementation in response to microbial oxidation of hydrocarbons is well documented and includes pore-filling carbonate along contacts of petroleum reservoirs (Macaulay et al, 2000), fault cements (Eichhubl and Boles, 2000a;Boles et al, 2004), cements associated with natural hydrocarbon microseeps (Donovan, 1974;Donovan et al, 1974;Gunatilaka, 1989), and cements associated with hydrocarbon spills (Tuccillo et al, 1999). These cements are generally understood to be frequently highly depleted in 13 C, reflecting the isotopically light carbon pool in the oil and gas phase.…”

Fracture-controlled paleohydrogeology in a basement-cored, fault-related fold: Sheep Mountain Anticline, Wyoming, United States

“…Two processes can together explain the isotopic shift observed between the Paleogene meteoric fluids and the fluids precipitated in Laramide fractures: (1) a minimal isotopic equilibration between fluids and host rocks (Figure 4b) and (2) the mix of meteoric fluids with basinal fluids (Figure 6). The wide range in δ 13 C values of all vein cements is likely related to a local contamination with hydrocarbons [e.g., Hathaway and Degens , 1969; Donovan et al , 1974; Boles et al , 2004], and thus supports a mix with basinal fluids.…”

Ground-water quality assessment of the central Oklahoma aquifer, Oklahoma: results of investigations

“…The effect of hydrocarbon migration on 813CPDB of carbonates within Permian rocks of Oklahoma has been described by Donovan, Friedman, and Gleason (1974) and Lilburn and Al-Shaieb (1984). In contrast to results of these studies, dolomite samples in the aquifer have relatively uniform 813CPDB values (-8 to -10 per mil).…”