Modeling petroleum expulsion in sedimentary basins: The importance of igneous intrusion timing and basement composition

Abstract

The concept of a critical moment in a petroleum system (the time of highest probability of entrapment and preservation of oil and gas) has underlain petroleum exploration for over 25 years. However, one area where understanding the critical moment is challenging is the Faroe-Shetland Basin (FSB; offshore UK). Isotopic dating of oils suggests that petroleum generation began between ca. 68 and 90 Ma; however, most basin models invoke an earlier generation beginning in the mid-Cretaceous at ca. 100 Ma, predating deposition of Paleocene and Eocene reservoirs. This time discrepancy has previously been explained by remigration from intermediary accumulations ("motel" hypothesis) and/or overpressure retardation of kerogen maturation. The FSB is characterized by a thick Cretaceous stratigraphic package (up to 5 km) that includes a large net thickness (up to 2 km) of Paleogene igneous material. In our model, separating sedimentary and igneous material and adding the igneous material at the correct time between ca. 58 and 55 Ma shallows the modeled burial depth of the Upper Jurassic source rocks during the Cretaceous sufficiently to delay maturation by 17 m.y. in comparison to results of previous studies. Additionally, previous studies have invoked crustal radiogenic heat production (RHP) based on the Phanerozoic crust averaging ∼2.8 μW/m 3 in the North Sea (300 km to the east). However, the FSB basement is composed of significantly older, colder Neoarchean orthogneisses (ca. 2.7-2.9 Ga), reducing RHP by up to 50% to ∼1.6 μW/m 3 (σ = 0.74). For the first time, our model unifies geological, geochronological, and geochemical observations, delaying the onset of petroleum expulsion by up to 40 m.y. in comparison to previous models.

Regional correlation and seismic stratigraphy of Triassic Strata in the Greater Barents Sea: Implications for sediment transport in Arctic basins

“…Gac et al, 2014), this effect has hitherto not been taken into account (cf. Gardiner et al, 2019) in the GBSB. Accounting for the intrusions leads to an ca.…”

Analysis of deformation bands associated with the Trachyte Mesa intrusion, Henry Mountains, Utah: implications for reservoir connectivity and fluid flow around sill intrusions

“…Malthe-Sørrenssen et al, 2004;Hansen and Cartwright 2006); West of Shetland (e.g. Rateau et al, 2013;Gardiner et al, 2019); and the southern and north-western margins of Australia (e.g. Holford et al, 2012;Mark et al, 2020).…”

“…Brooks Hanson, 1995;Rodriguez-Monreal et al, 2009;Senger et al, 2014;Aarnes et al, 2015;Gardiner et al, 2019), as too has been the hydrothermal fluid flow associated with their emplacement (e.g. Rossetti et al, 2007;Scott et al, 2015).…”

Analysis of deformation bands associated with the Trachyte Mesa intrusion, Henry Mountains, Utah: implications for reservoir connectivity and fluid flow around sill intrusions

“…Aydin, 1978;Underhill and Woodcock, 1987;Shipton and Cowie, 2001;Wibberley et al, 2007). Numerous studies have shown that deformation bands can have a significant influence on fluid flow Aydin, 1994, 1995;Gibson, 1998;Sigda et al, 1999;Fossen and Bale, 2007;Ballas et al, 2015). Due to their mode of formation (i.e.…”