Geochemical Evaluation of Paleocene Source Rocks in the Kohat Sub-Basin, Pakistan
Notice bibliographique
Résumé
High Resolution Image Download MS PowerPoint Slide The Kohat sub-basin is one of the main hydrocarbon-producing sedimentary basins located in the northwest extension of the Indus Basin in Pakistan. It contains numerous proven and potential petroleum from the Cambrian to the Miocene. Conventional petroleum resources have been depleting rapidly over the last couple of years. Therefore, unconventional resources should be explored using a variety of geochemical and geophysical techniques to address the energy demands. Geochemical techniques, including total organic carbon (TOC) assessment, Rock-Eval pyrolysis, organic petrography, and biomarker studies, are essential for evaluating the potential of shale gas reservoirs to delineate future prospects in a basin. The source rock potential of the Paleocene rocks, including the Patala, Lockhart, and Hangu formations of the sub-basin, is evaluated using geochemical analyses on well cuttings from the Tolanj-01 well. The analyses include estimation of total organic carbon (TOC), Rock-Eval pyrolysis, and organic petrography (vitrinite reflectance) to evaluate the organic richness, thermal maturity, kerogen type, hydrocarbon type, and environment of deposition. Other techniques for extractable organic matter (EOM) include solid–liquid chromatographic separation of fractions, gas chromatography (GC-FID)/whole oil chromatography, and gas chromatography–mass spectrometry (GC-MS). The organic matter (TOC, wt %) analysis reveals that 18 (18) samples of the Hangu formation (0.08–1.8 wt %) show poor values, 12 (12) samples of the Lockhart formation (0.05–0.5 wt %) have poor to fair content, and 26 (26) samples of the Patala formation have poor to fair (0.08–0.19 wt %) TOC content. Rock-Eval pyrolysis studies including hydrogen index, oxygen index, T max, quantities of free hydrocarbons (S 1, mg/g), and hydrocarbons produced from pyrolysis (S 2, mg/g) are determined for the well-cut samples (56) of the Paleocene rocks. The hydrogen index values for the Hangu formation are lower than 200, and those for the Lockhart and Patala formations range between 100 and 250. A maceral analysis is also conducted on these samples, which reveal that the majority of the samples of the Paleocene units present in the basin belong to kerogen types II/III. The thermal maturity of the Hangu and Lockhart formations falls in the late-stage oil window, while that of the Patala formation falls in the peak to late oil window. The genetic potential (GP) for these rock units is also determined based on S 1 and S 2 values, which reveals that it is generally poor except for a few samples of the Hangu and Lockhart formations, which show fair GP values. For the organic petrography (vitrinite reflectance, R 0 ), one sample from each unit is selected, which shows that the Hangu, Lockhart, and Patala formations fall in the category of the mature oil window with their R 0 (%) values being 0.95, 0.89, and 0.82, respectively. The extracts (EOM) from these rock units are also analyzed to assess the depositional settings, biological source input, biodegradation, thermal maturity, etc. The greater values of pristine to phytane (Pr/Ph > 1) ratios for Hangu (1.33), Lockhart (1.23), and Patala (1.8) indicate an intermediate condition (suboxic), while a cross-plot of Pr/ n -C 17 –Ph/ n -C 18 shows that the organic matter is deposited in a transitional setting. The ratios between C 19 TCT/C 19 TCT + C 23 TCT and C 24 TeCT/C 24 TeCT + C 23 TCT biological source inputs are mainly of marine origin. Similarly, the ternary diagram of regular steranes (C 27 –C 28 –C 29 ) shows a greater marine input. Lower values of the carbon preference index (CPI1) for Hangu (0.95), Lockhart (0.91), and Patala (1.04) indicate higher thermal maturity of the Paleocene rocks. Similarly, the methylphenanthrene index (MPI-1) values, Moretane index, and Pr/ n -C 17 vs Ph/ n -C 18 plots also show higher thermal maturity for these rock extracts.
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Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».