October 31, 1975 - Gerald R. Ford Presidential Library and Museum

The Hawkins oil field is located in southeast Wood County, Texas. in
the East Texaa Basin.
The principal producing formation at Hawkins is the Woodbine Sand of
Cretaceous age which occurs at 4,200 feet. The Woodbine is composed
of the Lewisville and Dexter units which are divided into 10 highly
porous and permeable intercommunicative sands. The Dexter (lower 3
of the 10 sands) has 80 percent of the reservoir volume.
Hawkins is a complexly faulted anticline which is underlain by a
deep seated salt mass. Except for a major N-S fault, which separated
the field into the West and East Segments, the 42 fault segments of
the field are intercommunicative. In addition to structure, the
accumulation is controlled by a common water table at the base. The
Eagle Ford Shale, and sometimes the Austin Chalk provides the upper
seal. At the base of the West Segment, there is a heavy asphalt
layer ranging in thickness from 50 feet on the north to 100 feet in
the south. The productive area is 10,600 acres (17 square miles).
The hydrocarbons originally in place at Hawkins were calculated using
the volumetric method. There are considerable core data. The field
was heavily studied and reported on prlor to unltlzation.
The crude oil at Hawkins was originally saturated and a large original
gas cap existed. The asphaltic layer in the Western Segment has
restricted watp.r encroachment into the oil reservoir. The absence
of this layer in the Eastern Segment probably accounts for the 15
percent reduction in the original pressure there, which has been
attributed to heavy withdrawals from the East Texas field (14 miles
away and discovered 10 years earlier). The primary recovery mechanisms
include solution gas drive, gas cap drive with gravity
drainage, and water drive. In the Western Segment, water drive is
limited and the gravity drainage mechanism is considered more
important. The opposite situation may prevail to some extent in
the Eastern SeQment. The field was unitized on January 1, 1975.
The operating plan is to inject inert gas near the gas/oil contact
to maintain pressure and to prevent migration of oil into the gas
cap area (which has occurred to some extent in the past). Even in
the Western Segment, a high pressure differential between the oil
reservoir and the aquifer can prompt water influx through the
thinner portions of the asphaltic 1ayer.
The consulting firm has adopted the oil recovery efficiency which was
developed in the operating plan by the engineering unitization
committee. This efficiency is 70 percent of the oil originally in
place and is reported by the consultant to result from gas cap
expansion and gravity drainage recovery mechanisms. At this pOint
in the producing life of the field, the portion of the secondary
recovery volume that should be defined as "proved" or as "indicated"
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