Fordoche oil field: sandstone and mudstone cores
South-central Louisiana, Pointe Coupee Parish, United States
Sediments
- Type
- Sediment
Oil and gas field in sandstones of the Wilcox Formation (Eocene), stacked reservoirs W-12, W-8 and Sparta B between 3500 and 4350 m, fed through a regional fault; source rock below the reservoirs (mudstone at 4334 m). Approximate coordinates of the village of Fordoche. Pore-filling clays of the sandstones around -2 ‰ whatever the depth, illite-smectite clays of the mudstones around -19 ‰ (200 to 300 ppm fixed B), source rock kerogen at 140 ppm B.
δ11B in ‰ (per mil) Values of the same system
Standard : NIST SRM 951
| Value | Range | n | Mineral or matrix | Source |
|---|---|---|---|---|
| −2.5 ± 0.7 ‰ | −3.4 / −1.3 ‰ | 8 | pore-filling clays of the shallowest reservoir sandstone (LNB 11614, 3540 m) Mean and standard deviation recalculated from 8 analyses, -3.4 to -1.3 (-2.2; -2.7; -2.2; -2.9; -2.2; -3.4; -1.3; -3.3). Mannitol-washed section, 228 ppm B; published mean -2.5 ± 0.2 ‰ (standard error). | Williams et al. (2001), The influence of organic matter on the boron isotope geochemistry… |
| −2.2 ± 4.2 ‰ | −8.1 / 2.6 ‰ | 6 | pore-filling clays of the deepest reservoir sandstone (Holloway 13820, 4212 m) Mean and standard deviation recalculated from 6 analyses, -8.1 to +2.6 (-0.5; -1.3; -6.5; -8.1; +0.9; +2.6). Mannitol-washed section, 157 ppm B; two spots on a new pore (+0.9 and +2.6 ‰); published mean -2.1 ± 1.7 ‰ (standard error). | Williams et al. (2001), The influence of organic matter on the boron isotope geochemistry… |
| −18.8 ± 3.5 ‰ | −23.4 / −9.3 ‰ | 13 | mudstone clays at 3536 m (LNB 11607) Mean and standard deviation recalculated from 13 analyses, -23.4 to -9.3 (-19.3; -17.7; -20.9; -17.6; -16.5; -19.7; -18.6; -9.3; -20.9; -17.4; -22.3; -23.4; -21.3). Section soaked 72 h in mannitol, 258 ppm B, published mean -18.9 ± 3.5 ‰; before treatment +6.6 ± 2.9 ‰ with adsorbed boron. Repolished and remeasured without further washing: -17.3; -19.1; -19.8 ‰ (mean -18.7 ‰). Clay with 44 % kaolinite, 30 % smectite, 15 % chlorite and 11 % illite-smectite. | Williams et al. (2001), The influence of organic matter on the boron isotope geochemistry… |
| −18.7 ± 3.9 ‰ | −23.7 / −15.5 ‰ | 5 | mudstone clays of the source rock at 4334 m (Kimball 14220) Mean and standard deviation recalculated from 5 analyses, -23.7 to -15.5 (-16.8; -23.7; -15.6; -22.1; -15.5). Mannitol-washed section, 196 ppm B. | Williams et al. (2001), The influence of organic matter on the boron isotope geochemistry… |
| −2.2 ± 2.2 ‰ | −6.9 / 0.8 ‰ | 12 | kerogen extracted from the source rock at 4334 m (NTIMS) Mean and standard deviation recalculated from 12 analyses, -6.9 to +0.8 (-6.9; -2.4; -0.5; -3.6; -3.5; -2.4; +0.8; -3.8; +0.5; -2.6; +0.2; -2.5). Kerogen isolated with HF-HCl then burnt in a Parr bomb, 140 ppm B; Table 3, twelve measurements. The table computes δ11B with 4.0377 for the standard instead of the measured 4.0337: with the latter each value would be about 1 ‰ higher. Published mean -2.2 ± 2.2 ‰; Table 1 gives -2 ‰ for the same kerogen. | Williams et al. (2001), The influence of organic matter on the boron isotope geochemistry… |
| −4.6 ± 4.1 ‰ | −12 / −1 ‰ | 7 | kerogen in thin section of the source rock at 4334 m (SIMS) Mean and standard deviation recalculated from 7 analyses, -12.0 to -1.0 (-2.1; -12.0; -8.4; -3.9; -1.6; -1.0; -3.5). Defocused 5 nA beam, instrumental fractionation taken at -48 ‰; published mean -4.7 ± 4.1 ‰. Confirms the negative sign of the extracted kerogen. | Williams et al. (2001), The influence of organic matter on the boron isotope geochemistry… |
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Cite this page
IsoFind Atlas (2026). Fordoche oil field: sandstone and mudstone cores, isotope signatures. https://www.isofind.tech/isotopes/en/sites/champ-petrolier-de-fordoche-carottes-de-gres-et-d-argilites/ (accessed 2026-10-20).
@misc{isofind2026fordocheoilfieldsandstoneandm,
title = {Fordoche oil field: sandstone and mudstone cores, isotope signatures},
author = {{IsoFind Atlas}},
year = {2026},
url = {https://www.isofind.tech/isotopes/en/sites/champ-petrolier-de-fordoche-carottes-de-gres-et-d-argilites/},
note = {Accessed 2026-10-20}
}Updated : 2026-10-20