Seismic analysis of igneous systems in sedimentary basins and their impacts on hydrocarbon prospectivity: examples from the southern Australian margin

Abstract

The increasing availability of 3D seismic data from sedimentary basins at volcanic and non-volcanic continental margins has provided fundamental new insights into both the storage and transport of magma in the continental crust. As global hydrocarbon exploration increasingly focuses on passive margin basins with evidence for past intrusive and extrusive igneous activity, constraining the distribution, timing and pathways of magmatism in these basins is essential to reduce exploration risk. Producing and prospective Australian passive margin basins where igneous systems have been identified include the Bight, Otway, Bass, Gippsland and Sorell basins of the southern margin. This paper reviews both the impacts of volcanic activity on sedimentary basin hydrocarbon prospectivity (e.g. advective heating, reservoir compartmentalisation and diagenesis), and the styles, distribution and timing of late Cretaceous-Recent extrusive and intrusive igneous activity along basins of the southern Australian margin, providing illustrative examples based on 2D and 3D seismic reflection data. KEYWORDSAustralia, sedimentary basins, volcanics, intrusives, seismic reflection, petroleum systems. INTRODUCTIONThe past few decades have witnessed a progressive shift of focus in the quest for new conventional hydrocarbon resources, away from the onshore and shallow-water regions that dominated production throughout the 20th century, and towards the submerged and often deep-water (>500 m below sea level) continental margins that fringe the deep ocean basins (White et al, 2003). Although exploration of all hydrocarbon basins is subject to problems (Doré et al, 2002), exploration of continental margins poses major risks due to the significant geological uncertainties that stem from sparse data coverage and their poorly understood formation and evolution. An important geological risk associated with exploration in almost all continental margins is the presence of igneous rocks. Volcanic activity is a key outcome of lithospheric stretching processes (Planke et al, 2000), and thus all extensional sedimentary basins located along continental margins witness some degree of intrusive and extrusive activity during their life spans. This includes basins that are located along margins considered to be 'cold ' , or 'nonvolcanic' (White et al, 2003).Hydrocarbon exploration has traditionally overlooked or avoided basins containing igneous rocks (Schutter, 2003; Rohrman, 2007). This is mainly because of the difficulties associated with seismic imaging of sedimentary sequences beneath basalt covers, and the detrimental short-term and long-term impacts on petroleum systems, including reservoir degradation and compartmentalisation (Schutter, 2003; Planke et al, 2005; Rohrman, 2007). The depletion of reserves in traditional hydrocarbon provinces, however-coupled with improvements in seismic acquisition and processing methods in basins containing problematic high-impedance layers (e.g. basalts)-has led to increasing exploration activity, with some not...

Lateral Magma Flow in Mafic Sill‐complexes

“…8-12 and 14;Thomson and Hutton, 2004). These inclined sheets transfer magma from deeper sills to shallower stratigraphic levels and are thus integral to facilitating magma ascent in sedimentary basins (Thomson and Hutton, 2004;Cartwright and Hansen, 2006;Holford et al, 2012;Muirhead et al, 2012;Magee et al, 2013cMagee et al, , 2014. Within the volcanological literature, studies of inclined sheet emplacement have primarily focused on the formation of cone sheets, i.e., swarms of concentric, inwardly inclined sheet intrusions that dip toward and are inferred to emanate from a central magma chamber (e.g., Anderson, 1937;Gautneb et al, 1989;Schirnick et al, 1999;Klausen, 2004;Geshi, 2005;Bistacchi et al, 2012;Burchardt et al, 2013).…”

Unravelling intrusion-induced forced fold kinematics and ground deformation using 3D seismic reflection data

“…Reeckmann and Mebberson 1984;Smallwood and Maresh 2002;Schutter 2003;Schmiedel et al 2017]; (ii) intrusion-induced faulting and fracturing, which may accompany folding, can increase local permeability and potentially breach traps or compartmentalise reservoirs [e.g. Reeckmann and Mebberson 1984;Holford et al 2012;Holford et al 2013]; and (iii) inelastic deformation processes involving porosity reduction (e.g. compaction and fluidization) can inhibit hydrocarbon migration and reduce reservoir quality [Schofield et al 2015].…”

Characterising extrusive and intrusive magmatism at the Kipper Field, Gippsland Basin, using 3D seismic data

“…The presence of igneous rocks in such basins represents a key uncertainty that must be quantified due to the detrimental effects that magmatic activity poses to source and reservoir rock quality and the possibility for increased maturation, trap formation and compartmentalisation (e.g. Holford et al (2012); Meeuws et al (2016)). To date our understanding of magmatic processes in sedimentary basins has generally been restricted to field and geochemical studies of exhumed basins with limited exposure, though the increasing availability of 3D seismic data has provided a powerful means by which the processes that transport magma through sedimentary basins, and the impacts of these processes on petroleum systems, can be better understood.…”