Oil & Natural Gas Projects
Exploration and Production Technologies
Integrated Geological-Engineering Model for Reef and Carbonate Shoal Reservoirs
Associated with Paleohighs: Upper Jurassic Smackover Formation, Northeastern Gulf
This project was selected in response to DOE's Oil Exploration and Production
solicitation DE-PS26-01NT41048 (focus area: Critical Upstream Advanced Diagnostics
and Imaging Technology). The goal of the solicitation was to promote cross-cutting
technologies for imaging and quantifying reservoir rock and fluid properties
for improved oil recovery.
To increase the profitability, producibility, and efficiency of the recovery
of oil from existing and undiscovered Upper Jurassic Smackover reservoirs and
fields characterized by reef and carbonate shoals associated with pre-Mesozoic
University of Alabama
Texas A&M University
College Station, TX
Longleaf Energy Group
Strago Petroleum Corporation
Paramount Petroleum Company
Geoscientific reservoir property, geophysical seismic attribute, petrophysical
property, and engineering property characterization have shown that reef and
shoal reservoir lithofacies developed on the flanks of high-relief crystalline
basement paleohighs (Vocation field) and on the crest and flanks of low-relief
crystalline basement paleohighs (Appleton field). Geologic modeling and reservoir
simulation indicate that little oil remains to be recovered at Appleton field
and a significant amount of oil remains to be recovered at Vocation field through
a strategic infill drilling program.
The complex nature of carbonate reservoirs makes the design of successful exploration
strategies and of cost-effective development scenarios difficult for these rocks.
The understanding of the rock and fluid characteristics that affect the reservoir
properties of these rocks serves to improve techniques for reservoir detection,
characterization, and development.
The completion of this project has resulted in an improved understanding of
the geological, geophysical, petrophysical, and engineering properties of reef-shoal
reservoirs emphasizing Appleton and Vocation fields in southwest Alabama. An
integrated geological model based on these properties has been developed to
facilitate exploration for reef-shoal reservoirs and to enhance development
of reef-shoal reservoirs in existing fields. This information has been transferred
to the operators of Appleton and Vocation fields and to other independents operating
in the eastern Gulf Coastal Plain area through technology workshops. The findings
of this project have the potential to result in increased oil producibility
from existing and newly discovered fields similar to Appleton and Vocation fields.
The Upper Jurassic Smackover Formation is one of the most prolific hydrocarbon
reservoirs in the northeastern Gulf of Mexico. Although production from Smackover
fields totals 1 billion barrels of oil and 4 trillion cubic feet of natural
gas, much of the oil in these fields remains unrecovered because of a lack of
a complete understanding of the rock and fluid characteristics that affect reservoir
architecture, heterogeneity, quality, fluid flow, and producibility. This problem
is compounded because of inadequate techniques for reservoir detection and the
characterization of rock fluid interactions, as well as imperfect models for
fluid flow prediction.
In addition, independent operators dominate the development and management of
these fields in the Eastern Gulf Coastal Plain. These companies do not have
the financial resources and/or staff expertise to improve substantially the
understanding of the geoscientific and engineering factors affecting the producibility
of Smackover carbonate reservoirs, which makes research and application of new
technologies for reef-shoal reservoirs all that more important.
Among the project's accomplishments:
- Geoscientific reservoir property, geophysical seismic attribute, petrophysical
property, and engineering property characterization have shown that reef (thrombolite)
and shoal reservoir lithofacies developed on the flanks of high-relief crystalline
basement paleohighs and on the crest and flank of low-relief crystalline basement
- Reef thrombolite lithofacies have higher reservoir quality than shoal lithofacies
due to overall higher permeabilities and greater interconnectivity.
- Reef thrombolite dolostone flow units, which are dominated by dolomite intercrystalline
and vuggy pores, are characterized by a pore system comprising a higher percentage
of large-sized pores and larger pore throats.
- Rock fluid interactions (diagenesis) studies have shown that although the
primary control on reservoir architecture and geographic distribution of Smackover
reservoirs is the fabric and texture of depositional lithofacies, diagenesis
(dolomitization) is a significant factor that preserves and enhances reservoir
- Geologic modeling, reservoir simulation, and testing and applying the resulting
integrated geologic-engineering models have shown that little oil remains
to be recovered at Appleton field and a significant amount of oil remains
to be recovered at Vocation field through a strategic infill drilling program.
- The water-drive mechanisms for primary production in Appleton and Vocation
fields remain effective; therefore, the initiation of a pressure maintenance
program or enhanced recovery project in these fields is not required at this
- The integrated geologic-engineering model developed for a low-relief paleohigh
was tested for three scenarios involving the variables of present-day structural
elevation and the presence or absence of potential reef thrombolite lithofacies.
The predictions based upon the model were correct.
- From the integrated modeling, the characteristics of the ideal prospect
in the basement ridge play include a low-relief paleohigh associated with
a thrombolite doloboundstone and dolostone that has sufficient present-day
structural relief so that these carbonates rest above the oil-water contact.
The findings from these projects are being used to characterize and model the
thrombolite and shoal reservoirs at Little Cedar Creek field, a recent Smackover
discovery in southwest Alabama.
High-relief paleohigh and associated microbial reef facies model (Vocation field).
Low-relief paleohigh and associated microbial reef facies model (Appleton field).
Four annual DOE Project Technical Reports.
Morgan, D., Mapping and ranking flow nits in reef and shoal reservoirs associated
with paleohighs: Upper Jurassic (Oxfordian) Smackover Formation, Appleton and
Vocation fields, Escambia and Monroe Counties, Alabama, M.S. thesis, Texas A&M
University, 157 p., 2003
Parcell, W.D., Evaluating the development of Upper Jurassic reefs in the Smackover
Formation, eastern Gulf Coast, U.S.A., through fuzzy logic computer modeling,
JSR, Volume 71, p. 498-515, 2003
Tebo, J.M., Use of volume-based 3-D seismic attribute analysis to characterize
physical property distribution: a case study to delineate reservoir heterogeneity
at the Appleton field, S.W. Alabama, M.S. thesis, McGill University, 169 p.,
Mancini, E.A., Llinas, J.C., Parcell, W.C. Aurell, M., Bedenas, B., Leinfelder,
R.R., and Benson, D.J., Upper Jurassic thrombolite reservoir play, northeastern
Gulf of Mexico, AAPG Bulletin, Volume 88, pp. 1573-1602, 2004
Project Start: September 1, 2000
Project End: December 31, 2003
Anticipated DOE Contribution: $754,000
Performer Contribution: $542,000 (42% of total)
NETL - Virginia Weyland (email@example.com or 918-699-2041)
University of Alabama - Ernest Mancini (firstname.lastname@example.org or 205-348-4319)