Petroleum Systems Modelling in a Fold‐and‐thrust Belt Setting: The Inverted Cameros Basin, North‐central Spain

Abstract

The Mesozoic Cameros Basin, northern Spain, was inverted during the Cenozoic Alpine orogeny when the Tithonian – Upper Cretaceous sedimentary fill was uplifted and partially eroded. Tar sandstones outcropping in the southern part of the basin and pyrobitumen particles trapped in potential source rocks suggest that hydrocarbons have been generated in the basin and subsequently migrated. However, no economic accumulations of oil or gas have yet been found. This study reconstructs the evolution of possible petroleum systems in the basin from initial extension through to the inversion phase, and is based on structural, stratigraphic and sedimentological data integrated with petrographic and geochemical observations. Petroleum systems modelling was used to investigate the timing of source rock maturation and hydrocarbon generation, and to reconstruct possible hydrocarbon migration pathways and accumulations. In the northern part of the basin, modelling results indicate that the generation of hydrocarbons began in the Early Berriasian and reached a peak in the Late Barremian – Early Albian. The absence of traps during peak generation prevented the formation of significant hydrocarbon accumulations. Some accumulations formed after the deposition of post‐extensional units (Late Cretaceous in age) which acted as seals. However, during subsequent inversion, these reservoir units were uplifted and eroded. In the southern sector of the basin, hydrocarbon generation did not begin until the Late Cretaceous due to the lower rates of subsidence and burial, and migration and accumulation may have taken place until the initial phases of inversion. Sandstones impregnated with bitumen (tar sandstones) observed at the present day in the crests of surface anticlines in the south of the basin are interpreted to represent the relics of these palaeo‐accumulations. Despite a number of uncertainties which are inherent to modelling the petroleum systems evolution of an inverted and overmature basin, this study demonstrates the importance of integrating multidisciplinary and multi‐scale data to the resource assessment of a complex fold‐and‐thrust belt.

Fluid migration recorded by fluid inclusions in crack-sealed quartz veins and sandstone host rock; Cameros Basin, Spain

“…The lower Albian tar sandtones outcropping in the southern part of the basin (asterisk in Fig. 1; Mas et al, 2003;Omodeo-Salé et al, 2019) are another indication of the hydrocarbon migration.…”

“…Sedimentological and petrological evidence has suggested that a petroleum system was activated during the evolution of the Cameros Basin (Mas et al, 2002(Mas et al, , 2003(Mas et al, , 2019Omodeo-Salé et al, 2019). Solid hydrocarbon remains predating quartz syntaxial overgrowths in the sandstones of the Urbión Group have been found (Ochoa, 2006;Ochoa et al, 2007), testifying to the migration of hydrocarbons through these deposits during a relatively early diagenetic stage.…”

“…In addition, sealed fractures represent discontinuity planes which may strongly control the fluid circulation. Furthermore, hydrocarbons accumulated in rocks affected by hydrothermal metamorphism may be destroyed, as demonstrated in the Cameros Basin (Ochoa et al, 2007;Omodeo-Salé et al, 2019). Therefore, understanding the circulation of hydrothermal fluids in a sedimentary basin can be the key in exploration when evaluating exploitable hydrocarbons resources.…”

Petroleum System Modeling of a Fold and Thrust Belt: A Case Study from the Bannu Basin, Pakistan

“…In contrast, geochemical analyses, in addition to kinetic parameters, are important for quantifying the source rock properties, which can aid in understanding the potential for hydrocarbon generation in any sedimentary basin [19][20][21]. Furthermore, the migration pathways of the hydrocarbons can be constructed by incorporating the permeabilities of the lithological units and their geometric variations through time [22]. The integration of subsurface modeling, heat flow analysis, and geochemical analysis are incorporated into basin modeling simulations to understand the generation of hydrocarbons and the expulsion and migration scenarios for different source rocks within the basin [23].…”

Inversion tectonics: a brief petroleum industry perspective

“…During the last 30 years many facets of inversion tectonics were addressed, including physical modeling (e.g., Mc-Clay, 1989, 1995Buchanan and McClay, 1991;Mitra and Islam, 1994;Eisenstadt and Withjack, 1995;Keller and Mc-Clay, 1995;Yamada and McClay, 2004;Panien et al, 2005;Amilibia et al, 2005;Bonini et al, 2011;Granado et al, 2017;Roma et al, 2018;Ferrer et al, 2017), numerical modeling (e.g., Panien et al, 2006;Buiter et al, 2009;Granado and Ruh, 2019 ), basin modeling (e.g., Neumaier et al, 2016Neumaier et al, , 2017Omodeo-Salé et al, 2019) and crustal-scale geodynamics (e.g., Ziegler et al, 1995;Cloetingh et al, 2008). Obviously, as 3D seismic reflection data became frequently used by the petroleum industry, more subsurface case studies addressed inversion tectonics quantitatively (e.g., Davies et al, 2004;Jackson and Larsen, 2008;Jackson et al, 2013;Reilly et al, 2017;Phillips et al, 2020).…”