Tuesday, March 21, 2017 GSA Luncheon

"A Geologic Interpretation of the Chukchi Sea Petroleum Province: Offshore Alaska, USA"

Noon Luncheon 11:30-1:00 pm

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Ongoing exploration is targeting potential hydrocarbon reservoirs that were deposited downdip of mixed carbonate-siliciclastic shelves (e.g. Mesozoic reservoirs in Atlantic margins). Deep-water depositional sys-tems for pure carbonate and siliciclastic systems have been broadly studied but the stratigraphic complexity and variability of a shelf margin linked to shallow-marine, mixed depositional systems are still poorly known. We use extensive 2D and 3D seismic reflection data (peak frequencies 30-50 Hz), combined with data from exploration wells, over a large area (20,000 square kilometers) of the Browse Basin, Northwest Shelf of Australia, to interpret the spatial and temporal variability of Eocene-Oligocene carbonate and siliciclastic depositional systems from shallow to deep water. Detailed 3D seismic mapping reveals 1) the topset region was dominated by a combination of predominantly heterozoan carbonate shelf sediments, carbonate plat-forms, and wave-dominated siliciclastic shorelines, 2) two deep-water depozones with different slope relief, and 3) a variety of deep-water depositional geometries, including channel-levee systems and lobes, suggest-ing active turbidity currents downdip of the mixed carbonatesiliciclastic shallow marine systems. Deep-sea drilling in the outboard Argo abyssal plain sampled Oligocene mixed and pure silliclastic turbidites. A firstorder control on along-strike variability in this area is the relative position of the advancing shelf margin to underly-ing norteast-southwest oriented Paleozoic structures. The two distinct deep-water depozones are related to inflections in the slope profile overlying the Paleozoic and Jurassic structures. Elements influencing sediment dispersal and deep-water deposition along a complex slope profile include basement tectonic and antecedent topography, shelf physiography and distribution of carbonate accumulations. The combination of those factors produced a complex seismic-stratigraphic pattern that might be common in analogous mixed systems with a strong overprint of preceding tectonic basin configuration.


Speaker: Carla Sanchez Phelps, Anchorage

Carla earned a BE degree in Geophysics from Universidad Simon Bolivar (Caracas, Venezuela) in 2001. Shortly after graduation, she joined Petroleos de Venezuela (PDVSA) as an exploration geophysicist and worked in seismic processing and seismic interpretation for prospect maturation. In 2004 she moved to Texas to start a Masters program in Geological Sciences with The University of Texas at Austin. Her MS thesis char-acterized fluvial-deltaic channel reservoirs in offshore Louisiana through seismic geomorphology and well-log calculated shale volumes. In 2006 she started the doctoral program at The University of Texas at Austin. Her PhD research focused on the 3D stratigraphic architecture of shelf-edge deltas and their influence on the ad-jacent deep-water slope. In 2011 she earned her PhD degree and joined ConocoPhillips as a Senior Geolo-gist with the Geological Technology group. During her time with ConocoPhillips Technology, she primarily worked on reservoir presence prediction in 10 different basins around the world. Since 2016 Carla has been collaborating with the University of Texas Bureau of Economic Geology as a Research Fellow; she has been using large seismic datasets over the Browse Basin in the Northwest Shelf of Australia to investigate the stratigraphic architecture of mixed carbonate-siliciclastic systems. She moved to Alaska in December 2016 and since then has volunteered with the Alaska Geological Society as treasurer.


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