Fluvial-Deltaic Heavy Oil Reservoir
, San Joaquin Basin
Donald D. Miller, John G. McPherson, Thomas E. Convington
Unconsolidated arkosic sands deposited in a fluvial-deltaic geologic setting
comprise the heavy oil (13° API gravity) reservoir
at South Belridge field. The
field is located along the western side of the San Joaquin basin in Kern County,
California. More than 6,000 closely spaced and shallow wells are the key to
producing the estimated 1 billion bbl of ultimate recoverable oil production.
Thousands of layered and laterally discontinuous
reservoir
sands produce from
the Pleistocene Tulare Formation. The small scale of
reservoir
geometries is
exploited by a high well density, required for optimal heavy oil production.
Wells are typically spaced 200-500 ft (66-164 m) apart and drilled to 1,000 ft
(328 m) deep in the 14-mi2 (36-km2) producing area.
uccessful in-situ combustion, cyclic steaming, and steamflood projects have
benefited from the shallow-depth, thick, layered sands, which exhibit excellent
reservoir
quality. The fundamental criterion for finding another South Belridge
field is to realize the extraordinary development potential of shallow, heavy
oil reservoirs, even when an unspectacular discovery well is drilled.
The trap is a combination of structural and stratigraphic mechanisms
plus
influence from unconventional fluid-level and tar-seal traps. The depositional
model is interpreted as a braid delta sequence that prograded from the nearby
basin-margin highlands. A detailed fluvial-deltaic sedimentologic model
establishes close correlation between depositional lithofacies,
reservoir
geometries,
reservoir
quality, and heavy oil producibility. Typical porosity is
35% and permeability is 3,000 md.
AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.