Subseismic pathway prediction by three-dimensional structural restoration and strain analysis based on seismic interpretation

Abstract

For both modeling and management of a reservoir, pathways to and through the seal into the overburden are of vital importance. Therefore, we suggest applying the presented structural modeling workflow that analyzes internal strain, elongation, and paleogeomorphology of the given volume. It is assumed that the magnitude of strain is a proxy for the intensity of subseismic scale fracturing. Zones of high strain may correlate with potential migration pathways. Because of the enhanced need for securing near-surface layer integrity when CO2 storage is needed, an interpretation of three-dimensional (3-D) seismic data from the Cooperative Research Centre for Greenhouse Gas Technologies Otway site, Australia, was undertaken. The complete 3-D model was retrodeformed. Compactionplus deformation-related strain was calculated for the whole volume. The strain distribution after 3-D restoration showed a tripartition of the study area, with the most deformation (30%–50%) in the southwest. Of 24 faults, 4 compartmentalize different zones of deformation. The paleomorphology of the seal formation is determined to tilt northward, presumably because of a much larger normal fault to the north. From horizontal extension analysis, it is evident that most deformation occurred before 66 Ma and stopped abruptly because of the production of oceanic crust in the Southern Ocean.Within AUTHORS Jennifer Ziesch ~ Leibniz Institute for Applied Geophysics, Hannover, Germany; present address: State Authority for Mining, Energy and Geology, Hannover, Germany; [email protected] Jennifer Ziesch received her B.Sc. degree in 2007, her diploma in geosciences in 2010 at University of Göttingen, Germany, and her Ph.D. at Technical University of Berlin in 2016. Her research focuses on seismic interpretation, fault analysis, and structural restoration. She is now head of the Cartography and ThreeDimensional Modeling Department at the State Authority for Mining, Energy and Geology in Hannover, Germany. David C. Tanner ~ Leibniz Institute for Applied Geophysics, Hannover, Germany; [email protected] David Tanner earned a B.Sc. degree in geology from Liverpool University, United Kingdom; an M.Sc. degree from Imperial College, London, United Kingdom; and a doctorate fromGiessen University, Germany. His interests lie in structural geology. He specializes in threedimensional kinematic modeling of complexly deformed terrains. He is presently coordinator for topical research on terrestrial sediment systems and researcher in the Seismic Gravimetry, and Magnetics section at the Leibniz Institute for Applied Geophysics. Charlotte M. Krawczyk ~ Leibniz Institute for Applied Geophysics, Hannover, Germany; Technical University of Berlin, Berlin, Germany; Helmholtz Centre Potsdam, Research Centre for Geosciences (GFZ), Potsdam, Germany; [email protected] Charlotte Krawczyk is the director of the Geophysics Department at GFZ Potsdam and is a professor of geophysics at Technical University of Berlin. Her scientific interests comprise seismic methods and technical developments in applied geophysics, subseismic deformation analysis, and geophysical imaging of deformation and mass transport. She currently serves as the executive editor of Solid Earth, and she is a member of Acatech and AcademiaNet. Copyright ©2019. The American Association of Petroleum Geologists. All rights reserved. Gold Open Access. This paper is published under the terms of the CC-BY license. Manuscript received August 24, 2015; provisional acceptance September 28, 2015; revised manuscript received October 20, 2015; revised manuscript provisional acceptance April 14, 2016; 2nd revised manuscript received June 15, 2017; 2nd revised manuscript provisional acceptance September 12, 2017; 3rd revised manuscript received November 8, 2017; 3rd revised manuscript provisional acceptance August 31, 2018; 4th revised manuscript received September 21, 2018; 4th revised manuscript provisional acceptance October 9, 2018; 5th revised manuscript received October 18, 2018; final acceptance January 30, 2019. DOI:10.1306/0130191516517255 AAPG Bulletin, v. 103, no. 10 (October 2019), pp. 2317–2342 2317 the seal horizon, various high-strain zones and therefore subseismic pathways were determined. These zones range in width from 50 m (164 ft) up to 400 m (1312 ft) wide and do not simply follow fault traces, and—most importantly—none of them continue into the overburden. Such information is relevant for reservoir management and public communication and to safeguard near-surface ecologic assets.