Oil & Natural Gas Projects
Exploration and Production Technologies
Improved Oil Recovery from Upper Jurassic Smackover Carbonates (Class II
Reservoir) Through the Application of Advanced Technologies at Womack Hill Oil
Field, Choctaw and Clarke Counties, Alabama, Eastern Gulf Coastal Plain
The goal of the project is to adress technologies to extend the economic life
of Womack Hill field's Smackover reservoir through improved understanding of
the reservoir, recovery processes and producibility constraints and to transfer
this technology to domestic operators with analogous reservoirs or similar production
University of Alabama
Pruet Production Co.
Mississippi State University
University of Mississippi
Wayne Stafford and Associates
Texas A&M University
College Station, TX
These reservoirs occur in vertically stacked, heterogeneous depositional and porosity cycles. The cycles consist of lime mudstone/wackestone at the base and ooid grainstone at the top. Porosity has been enhanced through dissolution and dolomitization. Porosity is chiefly interparticle, solution-enlarged interparticle, grain moldic, intercrystalline dolomite and vuggy pores. Reservoir performance analysis and simulation indicate that the unitized western area has less than 1 MMSTB of oil remaining to be recovered, and that the eastern area has 2 to 3 MMSTB of oil to be recovered. A field-scale reservoir management strategy that includes the drilling of infill wells in the eastern area of the field and perforating existing wells in stratigraphically higher porosity zones in the unitized western area is recommended for sustaining production from the Womack Hill field.
The drilling and testing of the 13-10 well showed that the eastern part of the field continues to have a strong water drive; and therefore, there is no need to implement a pressure maintenance program in the eastern part of the field at this time, and the drilling of this well did not provide information that would be useful in modifying the existing water flood project in the western part of the field or in initiating an advanced oil technology application. Pruet decided not to drill a second infill well in the Womack Hill Field; therefore, an evaluation of the feasibility to use lateral/multilateral well completion technology was not undertaken.
Because of the highly complex nature of carbonate reservoirs, cost-effective
development of these reservoirs requires the implementation of an integrated
reservoir management strategy. The Smackover reservoir characterization and
modeling at Womack Hill field can be used to assess the current field-scale
reservoir management practices in this field.
The unit operator is integrating the information from the reservoir characterization,
3-D geologic modeling, reservoir performance analysis, and reservoir simulation
into a field-scale reservoir management strategy to improve operations in the
Womack Hill field Unit. The project identified the field areas with the highest
potential for oil recovery in both the western and eastern portions of Womack
Hill field. The reservoir performance, multiwell productivity analysis, and
reservoir simulation studies indicate that water injection continues to provide
stable support to maintain production from wells in the unitized western area
and that the strong water drive present in the eastern area of the field presently
is adequate to sustain production in this part of the Womack Hill field.
Womack Hill field, producing from the Jurrasic Smackover in southwest Alabama,
was discovered in 1970. The petroleum trap was originally interpreted as a salt
pillow anticline. With increasing oil production rates, the reservoir pressure
declined rapidly on the west end of the field. Because of this decline in reservoir
pressure in the western area of the reservoir, this portion of the field was
unitized in 1975, and a fresh and salt water injection program for pressure
maintenance was initiated. Ultimate oil recovery was estimated to be 17.1 MMSTB
from the unitized western area.
Ultimate primary oil recovery from the entire Womack Hill field was estimated
at 25.2 MMSTB or 29% of the original oil in place (87 MMSTB). The estimated
oil recovery from secondary operations was 40% or 34.8 MMSTB of oil from the
field. As a result of the modeling, it was concluded that a fluid-flow barrier
Thirty-seven (37) wells have been drilled within the field area. Overall, the
Womack Hill Field has produced 31.2 MMSTB of oil, 15.4 BSCF of gas, and 51.7
MMSTB of water from the Upper Jurassic Smackover Formation from 27 wells. The
unitized western area of Womack Hill field has produced 17.0 MMSTB of oil and
9.3 BSCF of gas.
The principal problem at the field is productivity and profitability. With time,
there has been a decrease in oil production, while operating costs continue
to increase. The major producibility problems are related to cost-effective,
field-scale reservoir management; reservoir connectivity due to carbonate rock
architecture and heterogeneity; pressure communication due to carbonate petrophysical
and engineering properties.
Geologic reservoir characterization has shown that the upper part of the Smackover
Formation in Womack Hill field is productive from carbonate shoal reservoirs
that occur in vertically stacked, heterogeneous depositional and porosity cycles.
The cycles typically consist of lime mudstone/wackestone at the base and ooid
grainstone at the top. The lime mudstone/wackestone lithofacies has been interpreted
as restricted bay and lagoon sediment, and the grainstone lithofacies has been
described as beach shoreface and shoal deposits. Dolomitizied cycles occur across
the field, but they are laterally heterogeneous in depositional texture and
diagenetic fabric. Porosity consists chiefly of depositional interparticle,
solution-enlarged interparticle, grain moldic, dolomite intercrystalline and
vuggy pores. Dolostone pore systems and flow units dominated by intercrystalline
and vuggy pores have the highest reservoir potential.
Engineering characterization and analysis has shown that the reservoir fluid
in Womack Hill field is conventional black oil. Pressure transient test data
support the interpretations that the Womack Hill field reservoir is compartmentalized
and that a fault bounds the field reservoir to the south. Reservoir performance
analysis indicates good volumetric correlation for high producing wells, and
that low producing wells correlate with lower reservoir continuity. Reservoir
performance studies have shown that 10% of the recoverable 34.6 MMSTB of oil
remains to be produced from the field. The undrained oil is concentrated in
structural highs associated with footwall uplifts in the unitized western area,
and along an elongated west-east anticline in the eastern part of the field.
Water injection in the field should be continued and conducted downdip and focused
towards areas of the field that are structurally low.
A 3-D geologic model has been constructed for the Womack Hill field structure
and reservoir. It shows that the petroleum trap is more complex than originally
interpreted. The trapping mechanisms include a fault trap (footwall uplift with
closure to the south against a major west-southeast trending, high-angle normal
fault) in the western area, a footwall uplift trap associated with a possible
southwest-northeast trending, high-angle normal fault in the south-central area,
and a salt-cored anticline with four-way dip closure in the eastern area. The
pressure difference between wells in the unitized western area of the field
and wells in the eastern area of the field may be attributed to a flow barrier
due to the presence of a possible southwest-northeast trending fault and a change
in porosity and/or permeability in Smackover facies. Reservoir characterization
and geologic modeling have shown that four areas in the Womack Hill field have
potential for the recovery of undrained oil.
Current Status (May 2006)
The project is on schedule and will be concluded on May 29, 2006. Pruet will continue to monitor and report the production of oil, gas and water from the infill well without DOE funding support.
Anticipated DOE Contribution: $2,875,122
Performer Contribution: $4,324,480 (60% of total)
Project Start: May 1, 2000
Project End: May 29, 2006
Anticipated DOE Contribution: $2,875,122
Performer Contribution: $4,324,480 (60% of total)
NETL - Chandra Nautiyal (firstname.lastname@example.org or 918-699-2021)
U. of Alabama - Ernest Mancini (email@example.com or 205-348-4319)
Hopkins, T.L., 2002, Integrated petrographic and petrophysical study of the Smackover Formation, Womack Hill Field, Clarke and Choctaw Counties, Alabama, M.S. thesis, Texas A&M University, 96 p
Mancini, E.A., Blasingame, T.A., Archer, R., Panetta, B.J., Llinas, J.C., Haynes, C.D., and Benson, D.J., 2004, Improving recovery from mature oil fields producing from carbonate reservoirs: Upper Jurassic Smackover Formation, Womack Hill Field (eastern Gulf Coast U.S.A): American Association of Petroleum Geologists Bulletin, v.88, p. 1639 – 1651.
Mancini, E.A., et al., 2004, Improved oil recovery from Upper Jurassic Smackover carbonates through the application of advanced technologies at Womack Hill Oil Field, Choctaw and Clarke Counties, Alabama, eastern Gulf Coast Plain, Phase I Final Report, DE-FC26-00BC15129, U.S. Department of Energy, 300 p.
Tedesco, W.A., 2002, Dolomitization and reservoir development of the Upper Jurassic Smackover Formation, Womack Hill Field, eastern Gulf Coastal Plain, Ph.D. dissertation, University of Mississippi, 251 p.
Tedesco, W.A., and Major, R.P., 2002, Stratigraphic and diagenetic controls on production from Smackover Formation reservoirs, Womack Hill Field, eastern Gulf Coastal Plain, Am. Assoc. Petroleum Geologists 2002 Abstract Volume, p. A174.
3-D geologic model of Womack Hill field.