Reservoir Potential of Thin-Bedded Turbidites: Prospect Tahoe

Abstract

Abstract Geological/Petrophysical modeling, production testing and pressure transient analysis have demonstrated that thin-bedded turbidites can be very productive and have large connected volumes at Prospect Tahoe. This offshore Alabama field (water depth = 1,500 ft) occurs as a northwest-southeast trending turbidite channel/levee complex and is predominantly a gas reservoir with a thin oil rim. There is a relatively large volume of geological and engineering data for this thin-bedded turbidite deposit. In addition to a 3-D seismic survey, there are seven exploratory penetrations (three with whole core), a production test, and PVT analyses from several samples. The hydrocarbon accumulation exhibits a proven hydrocarbon column height in excess of 700 feet over an area greater than 4,000 acres. The reservoir depth at Tahoe is about 10,000 feet subsea, and initial reservoir pressure is about 5,000 psia. A 100 foot cored interval was completed and production tested, attaining a stabilized rate of 29 MMCFPD for three days. The subsequent five-day downhole shut-in exhibited persistent radial flow, indicating permeability-thickness of 1,700 md-ft and a connected area in excess of 520 acres. In the production test interval, over 1,400 individual beds were identified from whole core. The average sand bed thickness is less than 0.5 inches, and no sand bed exceeds three inches in thickness. This interdisciplinary study demonstrated that thin-bedded turbidites can be successfully tested, be very productive, and have large connected volumes. This work may have analog application elsewhere.