Print this pageAAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Reservoir Characterization of the Big Foot Deepwater Confined Sheet System
(1) ETC - Clastic Stratigraphy, Chevron Corporation, Houston, TX.
(2) DWEP - Gulf of Mexico, Chevron Corporation, Houston, TX.
(3) Clastic Stratigraphy R&D, Chevron Corporation, Houston, TX.
Big Foot was discovered in 2005 in Walker Ridge Block 29, 225 miles south of New Orleans. The discovery well was drilled in approximately 5,000 feet of water and reached a total depth of 25,127 feet. The target was the Middle Miocene “Maroon Sand”. The sub-salt location of the Middle Miocene reservoir made seismic imaging difficult, and posed a major challenge to decipher the reservoir characteristics. Whole core, OBMI, and wireline log data were integrated to reduce uncertainty related to reservoir heterogeneity and architecture. Analyses of the core, OBMI and wireline log data revealed sediment gravity flows with thick, amalgamated, structureless turbidite sandstones (Bouma Ta) that are capped in places by minor amounts of low concentration Bouma Tb-Te turbidite beds. The core facies suggested rapid deposition in a relatively confined environment. Based on the analysis of these data, the depositional setting for the Big Foot reservoir was interpreted as an intra-slope sub-basin containing structurally confined sheet sands. While a channelized depositional setting initially could not be completely ruled out, the confined sheet interpretation predicted specific reservoir geometry and continuity that were tested and supported in subsequent wells. An appraisal well was planned to test the OW contact as well as confirm or refute our interpretation of a confined sheet. This well encountered a similar reservoir section to that found in the discovery well and also revealed the extent of the oil over the structure. The analyses of the core and correlation between the wells at Big Foot supported the interpretation that the Big Foot turbidites were deposited as a confined sheet in an intra-slope sub-basin. Big Foot is a success story that underlines the importance and value of conventional core data in reservoir characterization and reducing geologic uncertainty.