Bureau of Economic Geology, The University of Texas at Austin (www.beg.utexas.edu).
American Association of Petroleum Geologists Annual Meeting, Dallas, April 18-21, 2004
Stratigraphic Patterns and Controls on Reservoir Quality of the Giant Poza Rica Field, Albian, Cretaceous, Mexico
Charles Kerans, Robert Loucks, Xavier Janson, Alfredo Marhx, and Carlos Reyes
Characterization of the giant Poza Rica field using more than 800 wells, descriptions from 35 cored wells, and 3-D seismic covering the field and adjacent Tuxpan Platform margin affords a new look at this unique reservoir. Poza Rica is a carbonate slope reservoir having >1.5 Bbbl cumulative production since discovery in 1930. It produces from the Albian Tamabra Formation, the slope wedge equivalent of the Tuxpan Platform. This reservoir is an anomaly in the worlds portfolio of carbonate reservoirs, being at least two orders of magnitude larger than the mean cumulative production for carbonate slope settings. Critical factors are (1) high average phi/H for a carbonate slope deposit at average burial depth of 2,400 m, (2) the near-uninterrupted coarse turbidite and debris-flow deposition throughout the 13.3 m.y. of the Albian, though at an average paleowater depth of 1.2 km and at a distance of 10 to 15 km from the platform margin, (3) the aggradational nature of the sourcing Tuxpan Platform, with a progradation/aggradation ratio of near 1 during a greenhouse period, suggesting that shallow-water accommodation limitations were not the driving factor controlling source sediment. The Albian Tamabra is divided into four third-order sequences that show partitioning of coarse debris flows and mud-rich turbidites in transgressive systems tracts, widespread blanketing of grain-rich turbidites during highstand systems tracts, and introduction of siliciclastics and organic-rich carbonate mudstones during lowstand. This partitioning sets up a distinct reservoir zonation that requires integration of core, log, and seismic data for accurate reservoir model construction.