Josephine Prospect, Cognac Field, MC195 A "Typical" Shelf Deep Pool Discovery

Robert Rooney, Tim Bourgeois, Christina Davis, Michiel deGroot, Dave French, Machelle Johnson, John Leftwich, Brian O'Neill, and Keerthi McIntosh
Shell Exploration and Production, New Orleans, Louisiana

The Josephine Prospect was a deep pool test in the Cognac Field in Mississippi Canyon Block 195. The well was drilled in 2002 to 13,101 feet true vertical depth and found 112 net feet of gas in a channel-levee sand in the late Miocene PM5 (Textularia tatumi) biostratigraphic zone. Prior to this test, Cognac production was limited to Pliocene deltaic reservoirs that have produced over 170 million barrels of oil and 700 billion cubic feet of gas since 1979. The Josephine prospect was generated ahead of a field re-development program in 2001 and was mapped as an amplitude-supported 3-way fault closure up-thrown to the Cognac "E" fault. It was within an acoustically "invisible" chaotic seismic sequence that precluded the use of seismic geomorphology to predict sand presence. Sub-regional mapping of bounding seismic events and seismic-to-well ties of surrounding field wells, and wildcat wells indicated Upper Miocene slope deposition. Biostratigraphic data from the Upper Miocene in these wells identified a north-to-south facies gradation from outer neritic to bathyal conditions. Interestingly, the Upper Miocene paleo-bathymetric interpretation is almost identical to the present-day bathymetry in the greater Cognac area. Based on this relationship, the present-day shelf to slope-break seafloor morphology was used as the depositional analog for sand prediction at the Josephine Prospect. Amplitude analysis was used as a direct hydrocarbon indicator. The positive confirmation of the pre-drill geologic model suggests that the shelf margin in northern Mississippi Canyon can be used as an analog to other areas of the Louisiana Shelf and onshore where shelf to slope-break channel sands are targeted for oil and gas exploration.

AAPG Search and Discovery Article #90080©2005 GCAGS 55th Annual Convention, New Orleans, Louisiana