Date of Award

Spring 1-1-2018

Document Type

Thesis

Degree Name

Master of Science (MS)

First Advisor

Paul Weimer

Second Advisor

David Budd

Third Advisor

Carmen Fraticelli

Abstract

The Falkland Plateau Basin, including the Fitzroy sub-basin, is a frontier petroleum exploration area, which records a unique tectonic and stratigraphic evolution. Interpretation of a 6000 km2 3D, time-migrated seismic data set focused on the Cretaceous section, which is the most prospective in the area. The sequence stratigraphic architecture is defined, in detail, with emphasis on the evolution of the marginal marine depocenters and their downdip deepwater deposits.

Five second-order Cretaceous megasequences were defined, each comprising multiple third-order sequences. Each megasequence varies in terms of its structure, time-thickness, systems tracts, seismic facies, and their linkage between coeval shelf and basin-floor strata. The Cretaceous strata consist of a series of shallow marine deltaic systems that prograded to the southeast and delivered sediment to deepwater. At both the sequence and megasequence scale, sediments preferentially accumulated in either the shelf, slope or basin-floor settings, rather than being evenly distributed across the depositional profile. Variations in the depositional patterns are interpreted to be caused by a changing balance between sediment supply, relative changes in sea level, and tectonic events.

Megasequences 1 and 2 are overall aggradational, indicating a balance in sediment supply and basin subsidence. The extensive base-of-slope channel-levee systems in Megasequence 3 are the most favorable reservoirs. An extended relative lowstand in sea level associated with a second-order sequence boundary was the likely control on these thick deposits. Megasequence 4 consists of thick sigmoidal clinoforms that prograded 20-40 km basinward. Megasequence 5 is an entirely onlapping package whose sediment was sourced from a different direction than the underlying megasequences.

The presence of reservoir quality sand (Lower Cretaceous) and organic-rich source rocks (Lower Cretaceous and Upper Jurassic) has been documented by six exploration wells drilled on the Falkland Plateau, as well as DSDP sites 311 and 511. These wells confirm a working petroleum system in the region. The lack of structure in the basin means stratigraphic traps are the most prospective. The highest risk is the presence of source rock within the study area, as the nearest penetrations are over 100 km away.

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