AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
The Pony Discovery, Green Canyon Block 468, U.S. Gulf of Mexico: Depositional Facies and Reservoir Architecture of Miocene Turbidite Reservoirs
(1) Hess Corporation, Houston, TX.
Interpretation of depositional facies and reservoir architecture of Miocene submarine fan reservoirs of the Gulf of Mexico are challenged by the relative lack of seismic resolution in subsalt settings. This is especially true for the greater Pony area of Green Canyon GOM, where interpretations rely chiefly upon core sedimentology, e-log analysis, dipmeter data, well-log stacking pattern analysis, sequence stratigraphic correlation methodology and biostratigraphic analysis. Despite the great complexity and technical challenges, a successful reservoir characterization effort was carried out using an integrated, multidisciplinary work flow and new technology.
Middle Miocene (Serravallian) 3rd-order composite sequences, made up of submarine fan deposits make up the basin fill. Individual reservoirs represent 4th-5th order packages. Sands of the oldest composite sequences are comprised mainly of unconfined lobe-dominated facies and those of the younger sequences contain a greater abundance of partially confined channel-fill and overbank facies. From core studies, we recognize nine depositional elements representing axial to marginal/distal portions of a ponded submarine fan system. These include channel axis to channel margin, levee-overbank, debrites, channelized lobe, amalgamated lobe, marginal to distal lobe, slumped muds and heterolithics, and pelagic/hemipelagic muds.
Collaborative workflows between sedimentology and petrophysics led to predictive electrofacies solutions to uncored wells. Stacking pattern recognition, dipmeter logs, biostratigraphic identification of nannofossil-rich flooding surfaces, and an understanding of the general shapes, dimensions and lateral continuity of depositional elements helped guide the stratigraphic correlations. Geocellular models were constructed for reservoir simulation. Features of the depositional model which were considered important to replicate in the static geocellular model were (1) channel dimensions and density, (2) spatial relation of channel axis, channel margin and debrites, (3) spatially varying abundances of different types of depositional elements, and (3) varying azimuth of the variograms. A multi-truncated Gaussian approach was used to generate the expected stratigraphic character of the facies model, while matching specific target facies fractions in the simulation results.