Structural controls on the seismic sequence stratigraphy of the Ben Nevis, Avalon, and Eastern Shoals formations, Terra Nova field, Jeanne D'Arc Basin, offshore Newfoundland

Gollop, Alison (2003) Structural controls on the seismic sequence stratigraphy of the Ben Nevis, Avalon, and Eastern Shoals formations, Terra Nova field, Jeanne D'Arc Basin, offshore Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

The structural controls on the seismic sequence stratigraphy of the lower Cretaceous succession in the Terra Nova oil field, Grand Banks of Newfoundland, is studied using a digital 3-D seismic database and wireline log data from 11 offshore wells. Three seismic sequences (Units A, B, and C) were mapped in the Terra Nova area, roughly corresponding to the Eastern Shoals, Avalon, and Ben Nevis formations, respectively. Each sequence is bounded by distinct unconformities. The development of these sequences and their boundaries was controlled by an interplay of sediment input, changes in sea level, tectonism, accommodation space, and climate. However, tectonism (i.e., fault-block subsidence and rotation) is interpreted to be the principal cause for the sedimentary patterns and development of the major unconformities in the Terra Nova field; global eustatic sea-level variations had only a minor influence on unconformity generation. -- The N-S-trending fault system in the Terra Nova field was active during the Tithonian to mid-Valanginian, as evidenced by fault growth within the Hibernia and Rankin formations. The E-W-trending fault system was previously interpreted to have been formed during mid-Aptian to Albian extensional phases; however, growth-strata patterns within the Eastern Shoals Formation suggest instead that the E-W-trending fault system in the Terra Nova field was initiated by at least the late Barremian and was active until late Albian. Also, the N-S-trending fault system in the Terra Nova field was reactivated at this time. This fault system terminates upward against the Albian unconformity, so that by late Albian the active rifting in the Terra Nova field is interpreted to have ceased. -- A "pop-up" feature immediately west of the Voyager Fault in the Terra Nova field has been previously interpreted to have formed by transpressional stresses induced by oblique-slip movement. However, geometries similar to those presented in the model of Jackson and Vendeville (1992 and 1994) suggest that a large salt diapir may lie in the footwall of the Voyager Fault. Therefore, an alternative interpretation is proposed for this "pop-up" feature, as a localized contractional feature related to diapirism. -- The lower Cretaceous succession in the Terra Nova field does not contain hydrocarbons, but forms reservoirs in other oil fields such as Hibernia and White Rose. It is proposed that the reservoir facies represented by the Ben Nevis and Avalon formations in the Terra Nova field were charged with hydrocarbons at some point but were subsequently breached, allowing oil to escape from the traps. This scenario is consistent with published fluid-inclusion studies.

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