Sable Sub Basin Near Field Exploration Prospectivity

Abstract

Abstract Exploration in the Sable Sub-basin shelf is relatively immature and still holds surprising near-field exploration prospectivity around the Sable Offshore Energy Project (SOEP) infrastructure. Shell and partners have drilled 19 exploration wells on the current Shell interest leases in the Sable Sub-basin from 1969 to 2001 and have discovered nearly 1BBOE. Exploration proceeded in 3 phases, an early phase of hydropressure exploration, a main phase of deep geopressure exploration, and a later phase of exploration in geopressures. The early phase of exploration in hydropressures involved 5 wells from 1969 to 1975. Onondaga E-84, Triumph P-50, Thebaude P-84, Citnalta I-59, and Intrepid L-80 tested reservoir objectives ranging from the Late Jurassic MicMac Formation to the Early Cretaceous Upper Missisauga Formation. The discovered volume totaled 1.2 Tcf and 36MMBC. Drilling was suspended at the top of geopressures. Success at the top of geopressures in the Thebaude well encouraged deeper drilling in geopressures. Discovery of the 1.5 Tcf Venture field in 1978 kicked off a phase of successful deep exploration in geopressures. Another 11 deep wells were drilled through 1985 and discovered another 2.65 Tcf in a series of moderate sized gas fields ranging from 130 to 437 Bcf. These fields include Arcadia, Glenelg, Olympia, Venture, South Uniacke, Alma, Chebucto, Venture West, and Triumph North. Hydrocarbons, primarily gas, were found in both geopressured and hydropressured reservoirs that ranged in age from the Late Jurassic to the Early Cretaceous. The final phase of exploration resulted in only two wells since 1985, Sable South B-44 and Onondaga B-84, both resulted in discoveries. Most of the industry exploration in the basin since 1985 has focused on carbonate, not clastic plays. The next phase of exploration remains to be tested by the drill bit. Fifty-five leads have been defined in the Sable Sub-basin around the Sable Offshore Energy Project (SOEP) infrastructure. All the leads are downthrown fault closures with shelf margin delta complexes as reservoirs. The combined factors of rapid subsidence, high sediment input from a large river, and proximity to the shelf margin result in thick geopressured reservoirs with multiple intra-formational seals and thick top seals. Fault closure traps occur along faults with large throw with potentially long columns. Several geopressured traps in the discovered fields have fault dependent columns ranging from 100m to 205m. In conclusion, considerable scope for near field exploration is present in the Sable Sub-basin in conventional plays that have not been extensively explored since 1985.