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AAPG Bulletin

Abstract

AAPG Bulletin, V. 95, No. 1 (January 2011), P. 105-146.

Copyright copy2011. The American Association of Petroleum Geologists. All rights reserved.

DOI:10.1306/06301009107

Seismic architecture of a Lower Cretaceous platform-to-slope system, Santa Agueda and Poza Rica fields, Mexico

Xavier Janson,1 Charles Kerans,2 Robert Loucks,3 M. Alfredo Marhx,4 Carlos Reyes,5 Francisco Murguia6

1Bureau of Economic Geology, University of Texas at Austin, University Station Box X, Austin, Texas 78713-8924; [email protected]
2Department of Geological Sciences, University of Texas at Austin University Station C1100 Austin, Texas 78712-0254
3Bureau of Economic Geology, University of Texas at Austin, University Station Box X, Austin, Texas 78713-8924
4Pemex Exploracion y Produccion, Poza Rica, Mexico
5Pemex Exploracion y Produccion, Poza Rica, Mexico
6Pemex Exploracion y Produccion, Poza Rica, Mexico

ABSTRACT

Two three-dimensional seismic data sets over the Albian western Golden Lane margin and time-equivalent basinal deposits of Poza Rica field allowed us to investigate the linked architecture of a steep-sided carbonate platform (El Abra Formation) and a thick accumulation of redeposited carbonate sediment at the toe of the slope and in the basinal area (Tamabra Formation). Regional seismic cross sections show that the most aggrading Albian platform has an eroded platform top, a scalloped margin, and a channelized slope that are equivalent to a 20-km (12.4-mi)-wide, westward-thinning, thick toe-of-slope apron made of chaotic, contorted, mounded, moderate- to high-amplitude reflections. Detailed reflection geometries in the Albian toe-of-slope and basinal deposits consist of chaotic to short, discontinuous, low-amplitude reflection at the toe of the slope of the Golden Lane platform, laterally changing to a discontinuous mounded, shingling reflection, which ultimately turns into high-amplitude parallel reflections. We interpret this lateral change to reflect the seismic signature of the change from the block- and debris-flow–dominated toe-of-slope area, to debris-flow and concentrated density flow deposits in the basin that ultimately grade laterally into pelagic deposits. On a flattened seismic slice, mounded reflections correspond to lobate to fan-shaped seismic events several kilometers wide that are interpreted as a carbonate basin-floor fan. Comparison between core and seismic data shows a dominance of debris flows in the lower two Albian sequences (Albian 1 and Albian 2) that grade vertically into more lobate concentrated density flows and turbidites in the upper two Albian sequences (Albian 3 and Albian 4). Seismic data used in this study, combined with core observations, do not support the interpretation of the Albian Tamabra Formation being of shallow-water origin. Seismic features identified as basin-floor fan, channel, and debris-flow deposits have a shape and size that are similar to those of other redeposited basinal carbonate deposits elsewhere. The seismic architecture shows that the Poza Rica field is a typical example of thick accumulation of grainy porous carbonate deposits in a basinal setting. This example shows the potential of a large hydrocarbon accumulation in a tectonically modified stratigraphic trap around shallow-water carbonate platforms.

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