Application of U-Pb detrital zircon geochronology to drill cuttings for age control in hydrocarbon exploration wells: a case example from the Rukwa Rift Basin, Tanzania

Hilbert-Wolf, Hannah, Roberts, Eric, Downie, Bob, Mtelela, Cassy, Stevens, Nancy J., and O'Connor, Patrick (2017) Application of U-Pb detrital zircon geochronology to drill cuttings for age control in hydrocarbon exploration wells: a case example from the Rukwa Rift Basin, Tanzania. AAPG Bulletin, 101 (2). pp. 143-159.

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Abstract

Precise dating and correlation of drilled wells through continental successions is challenging for hydrocarbon exploration, especially where preservation and recovery of age-diagnostic fossils is poor. As a complement or alternative to biostratigraphic dating we demonstrate the effectiveness of U–Pb geochronology via laser ablation–inductively coupled plasma–mass spectrometry on detrital zircon from well cuttings. In basins with syndepositional volcanic input, the youngest zircons in a stratigraphic interval can refine and serve as a proxy for the age of deposition. We demonstrate the reliability of this technique when applied to hydrocarbon exploration wells by analyzing drill cuttings through a continental interval of the Galula-1 well in the Rukwa Rift Basin, East African rift system, Tanzania, which previously yielded conflicting biostratigraphy results. The lower third of the well section reveals a late Miocene to Pliocene up-hole younging trend in the youngest detrital zircon populations, which matches new radioisotopic ages on volcanic tuffs from a correlative outcrop section. This is followed by an interval with recycled young zircons, followed by a zircon-free interval, interpreted to correspond to changes in magma composition of the nearby Rungwe volcanic province. This study provides the first radioisotopic age constraints for the Lake Beds in the Rukwa rift and demonstrates that sedimentation in the basin began by 8.7 Ma, critical for burial and thermal history modeling and establishing the probability of a working hydrocarbon system. Correspondence in age and zircon preservation between well and outcrop samples from the same intervals provides strong support for applying U–Pb detrital zircon geochronology to well cuttings, as a rapid, inexpensive approach for hydrocarbon exploration.

Item ID: 47295
Item Type: Article (Research - C1)
ISSN: 1558-9153
Funders: Heritage Oil Rukwa Tanzania Ltd. (HORT), US National Science Foundation (NSF), National Geographic Society's Committee for Research and Exploration (NGS-CRE), AAPG Suzanne Takken Memorial Grant, AAPG Grants-in-Aid
Projects and Grants: NSF BCS_1127164, NSF EAR_1349825
Date Deposited: 22 Feb 2017 02:16
FoR Codes: 04 EARTH SCIENCES > 0403 Geology > 040301 Basin Analysis @ 50%
04 EARTH SCIENCES > 0402 Geochemistry > 040203 Isotope Geochemistry @ 50%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970104 Expanding Knowledge in the Earth Sciences @ 50%
85 ENERGY > 8501 Energy Exploration > 850103 Oil and Gas Exploration @ 50%
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