Reducing Reservoir Architecture Uncertainty for the Wilcox (Late Paleocene) Turbidite Trend in the Deep-Water Gulf of Mexico: The Value of Outcrop Analogs
Larry Zarra1, Morgan D. Sullivan2, and Tom R. Mooney2
1Chevron North America Exploration & Production Company, Houston, TX
2Chevron Energy Technology Company, Houston, TX
The Wilcox lowstand trend is an exciting new play in the deep-water Gulf of Mexico. Two dozen wildcats drilled since 2001 have had a 70 % success rate, with 2.5 BBO reserves likely, in discoveries ranging from 100 - 600 MMBO. This basin-floor turbidite fan play exceeds 34,000 mi2 in area, and wildcat wells are widely spaced (10-80 mi). Unfortunately, most of the trend is sub-salt, precluding seismic reservoir characterization. There is excellent core coverage, however, which enables calibration of depositional systems for appraisal decisions. Regional stratigraphic analysis suggests that the Wilcox 2 reservoir is channelized and the overlying Wilcox 1 reservoir is dominated by sheets.
The Lower Permian Skoorsteenberg Formation in Tanqua Karoo is composed of stacked turbiditic sandstones and mudstones deposited in a basin-floor fan setting. It is interpreted as an excellent analog for the Wilcox 1 & 2 reservoirs, based on grain size, lithofacies, net-to-gross and sandbody architecture. The Wilcox 2 and the proximal outcrops of Skoorsteenberg Formation are interpreted to contain numerous channel elements which cut into each other to produce relatively continuous flow units.
Dominating the channelized deposits are amalgamated, high-concentration turbidites, with local shale clast lags, interpreted as channel axis deposits. Thin-bedded heterolithic facies with evidence of cut and fill and slumping represent channel margin deposits. The Wilcox 1 reservoir and medial to distal outcrops of the Skoorsteenberg are made up of extremely continuous sheets.
Although they are extremely continuous, vertical connectivity is thought to be much lower. Due to the interpreted similarities between the Wilcox turbidites and the Skoorsteenberg Formation, dimensional and architectural data from these outcrops can be used to help constrain key reservoir uncertainties.
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