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Three-Dimensional Seismic Imaging and
Reservoir
Modeling of an Upper Paleozoic “Reefal” Buildup, Reinecke Field, West Texas,
United States*
By
Arthur H. Saller1, Skip Walden1, Steve Robertson2, Robert Nims2, Joe Schwab2, Hiroshi Hagiwara3, and Shigeharu Mizohata4
Search and Discovery Article 20044 (2006)
Posted December 20, 2006
*Adapted from article published in AAPG Memoir 81, Seismic Imaging of Carbonate Reservoirs and Systems, edited by Gregor P. Eberli, Jose Luis Masaferro, and J. F. Rick Sarg. This publication may be purchased from AAPG Bookstore.
1Unocal Corporation, Sugar Land, Texas, U.S.A. Currently, Chevron, Houston, Texas ([email protected])
2Pure Resources, Midland, Texas, U.S.A.
3Japan Oil Development Company, Abu Dhabi, United Arab Emirates; formerly, Japan National Oil Company, Chiba, Japan.
4Japan National Oil Company, Chiba, Japan
Abstract
Reinecke field is an upper Pennsylvanian to lowest Permian carbonate buildup in
the southern part of the Horseshoe Atoll, west Texas, United States. The field
and surrounding areas have been imaged with three 3-D seismic surveys and
penetrated by many wells. Although Reinecke is commonly referred to as a reefal
reservoir
, deposition occurred in stratified sequences, 50-100 ft (15-30 m)
thick, dominated by wackestones, packstones, and grainstones. Boundstones
(mainly rich in phylloid algae) constitute only 16% of the buildup. Seismic
reflectors within the buildup parallel sequence boundaries and are truncated at
the margins of the buildup. Three-dimensional seismic surveys show that the top
of the Reinecke buildup is highly irregular with more than 470 ft (143 m) of
relief. Deep-marine shales overlie the
reservoir
and act as a seal for this
stratigraphic trap. Reinecke's irregular, mounded morphology is the result of
localized carbonate growth and erosional truncation. Much of the erosional
truncation probably occurred in a deep-marine environment.
Reinecke's south dome acts a single continuous
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uAbstractuIntroductionuFigures 1-3uTextuSeismic datauFigures 4-7uTextuFacies/stratigraphyuFigures 8-9uTextuDepositional historyuFigure 10uTextuPorosity, permuFigure 11-12uTextuProduction historyuFigures 13-15uTextuConclusionsuReferencesuAcknowledgments
uAbstractuIntroductionuFigures 1-3uTextuSeismic datauFigures 4-7uTextuFacies/stratigraphyuFigures 8-9uTextuDepositional historyuFigure 10uTextuPorosity, permuFigure 11-12uTextuProduction historyuFigures 13-15uTextuConclusionsuReferencesuAcknowledgments
uAbstractuIntroductionuFigures 1-3uTextuSeismic datauFigures 4-7uTextuFacies/stratigraphyuFigures 8-9uTextuDepositional historyuFigure 10uTextuPorosity, permuFigure 11-12uTextuProduction historyuFigures 13-15uTextuConclusionsuReferencesuAcknowledgments
uAbstractuIntroductionuFigures 1-3uTextuSeismic datauFigures 4-7uTextuFacies/stratigraphyuFigures 8-9uTextuDepositional historyuFigure 10uTextuPorosity, permuFigure 11-12uTextuProduction historyuFigures 13-15uTextuConclusionsuReferencesuAcknowledgments
uAbstractuIntroductionuFigures 1-3uTextuSeismic datauFigures 4-7uTextuFacies/stratigraphyuFigures 8-9uTextuDepositional historyuFigure 10uTextuPorosity, permuFigure 11-12uTextuProduction historyuFigures 13-15uTextuConclusionsuReferencesuAcknowledgments
uAbstractuIntroductionuFigures 1-3uTextuSeismic datauFigures 4-7uTextuFacies/stratigraphyuFigures 8-9uTextuDepositional historyuFigure 10uTextuPorosity, permuFigure 11-12uTextuProduction historyuFigures 13-15uTextuConclusionsuReferencesuAcknowledgments
uAbstractuIntroductionuFigures 1-3uTextuSeismic datauFigures 4-7uTextuFacies/stratigraphyuFigures 8-9uTextuDepositional historyuFigure 10uTextuPorosity, permuFigure 11-12uTextuProduction historyuFigures 13-15uTextuConclusionsuReferencesuAcknowledgments
uAbstractuIntroductionuFigures 1-3uTextuSeismic datauFigures 4-7uTextuFacies/stratigraphyuFigures 8-9uTextuDepositional historyuFigure 10uTextuPorosity, permuFigure 11-12uTextuProduction historyuFigures 13-15uTextuConclusionsuReferencesuAcknowledgments
uAbstractuIntroductionuFigures 1-3uTextuSeismic datauFigures 4-7uTextuFacies/stratigraphyuFigures 8-9uTextuDepositional historyuFigure 10uTextuPorosity, permuFigure 11-12uTextuProduction historyuFigures 13-15uTextuConclusionsuReferencesuAcknowledgments
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Reinecke field is a stratigraphic trap for
oil in a “reefal” buildup. Reinecke field is part of the Horseshoe
Atoll, a northward-opening arc of upper Pennsylvanian carbonate buildups
in the Midland Basin of west Texas, United States (Figures
1and
2). Horseshoe Atoll fields are a series of stratigraphic traps that
have produced more than 2 billion bbl of oil and are characterized by
high permeability and high recovery efficiencies (near 50% of original
oil in place [OOIP] after waterflooding) (Galloway et al., 1983). Fields
on the eastern side of the Horseshoe Atoll have stratified porosity with
permeability barriers to vertical flow. Reinecke and other fields on the
south and west sides of the Horseshoe Atoll have vertical permeability
pathways that allow the top of the Approximately 83 million bbl of oil have been
produced from Reinecke field (approximately 3 mi2 [8 km2];
Figure 3) since its discovery in 1950. The south dome of Reinecke
field (approximately 1 mi2 [2.6 km2]), the focus
of this chapter, has produced 46 million bbl of oil. The carbonate
This joint Unocal-Japan National Oil Company
Three-Dimensional Seismic Data
Three 3-D seismic surveys have been acquired
at Reinecke. The first survey was shot in 1993 to locate possible
undrilled pinnacles within Reinecke field and undrilled structures away
from the main field. That initial, more regional survey (Figure
3) covered approximately 28 mi2 (72 km2) and
helped in the discovery of one small nearby field. A second survey was
shot in 1997 to image the south dome (approximately 5 mi2 [13
km2]) for The top of the Reinecke carbonate is shown
regionally by the 1993 3-D seismic survey (Figure
3). Middle and upper Pennsylvanian Two main factors have made lateral variations
in Depositional Facies and Stratigraphy
The main Deposition of these sequences occurred during “ice-house” times, and hence were subjected to high-amplitude sea level fluctuations (Veevers and Powell, 1987). Sequences typically have a thin basal part, a thick middle part, and upper part with variable thickness (Figures 8 and 9). Basal parts generally contain thin shale and/or bioclastic packstone-grainstone. The middle of sequences is dominated by fossiliferous wackestone (commonly phylloid algal wackestone) and phylloid algal boundstone. Grainstone is common in the upper part of sequences (Figures 8 and 9). Crinoidal grainstone occurs in the upper part of the two uppermost Pennsylvanian sequences. Oolitic grainstone is also common in the upper part of the two lower sequences (Figure 9). Nine main carbonate depositional facies are present, and boundstone comprises only 16% of this “reefal” buildup (Table 1).
Interpretation of Depositional History
Although the south dome of Reinecke field has a mounded or “reefal” morphology, it is composed of fairly stratiform sequences that apparently formed in response to variations in relative and probably eustatic sea level. Sequence boundaries are identified by soil- and exposure-related features (fractures, root traces, caliches, and brecciation) observed in core. Abrupt decreases in bulk-rock stable carbon and oxygen-isotope ratios below those surfaces support subaerial exposure (Figure 8). A depositional model for typical sequences is shown in Figure 10. The uppermost carbonate (lower Wolfcampian; above “100” marker) in the Reinecke buildup contains a no petrographic, cathodoluminescent, or stable isotopic evidence of freshwater diagenesis or subaerial exposure (J.A.D. Dickson, personal communication, 1999), suggesting that the last stage of erosion was not associated with subaerial exposure. Relief on the Reinecke carbonate structure is probably the result of differential carbonate growth, subaerial karstification, and deep-marine erosion following deposition and drowning of the Reinecke buildup. As the 3-D seismic data show (Figures 3, 6, 7), the upper surface of the Reinecke carbonate buildup is very irregular. Several sequences (Wolfcampian and parts of two Pennsylvanian) are truncated by that surface (Figures 3, 6, 7), suggesting that the top of carbonate is, at least in part, erosional. Strata overlying Reinecke and other Horseshoe Atoll fields are deep-water shales and carbonate sediment gravity flows (Vest, 1970; Galloway et al., 1983). The apparent seismic onlap of basinal strata (Figures 6 and 7) is really downlap or baselap of the distal toes of Wolfcamp sequences whose shelf margin is 50-100 km to the east (Figures 1 and 2). The Reinecke area remained in a deep-marine environment from drowning in the earliest Wolfcampian (earliest Permian) through much of the Leonardian (middle Permian) (Figure 2). During that time, lowstand clastic and carbonate slope strata prograded from the east and north and largely filled the Midland Basin. Final filling of the basin occurred during deposition of the San Andres Formation (upper Leonardian and lower Guadalupian; Figure 2). Shallow-marine carbonate and evaporite deposition dominated the Reinecke area during the rest of the Guadalupian and Ochoan (middle and Late Permian; above San Andres Formation). Distribution of Porosity, Dolomite, and Permeability
Most porosity at Reinecke occurs in sequences
subjected to subaerial exposure and meteoric diagenesis. Meteoric
diagenesis associated with subaerial exposure apparently helped preserve
intergranular porosity and microporosity in micrite by creating a
lithified framework that resisted compaction during subsequent burial.
Porosity is widespread in Excluding lime mudstones, depositional facies that are still limestone have similar average porosities (9.3-12.9%; Table 1). Permeability is highly variable depending on pore types within facies. Phylloid algal boundstone generally has the highest permeability. Lime wackestone and packstone with intercrystalline microporosity have lower average permeabilities (Table 1). Bioclastic grainstone with significant intergranular porosity has moderate permeability. Dolomite is a later diagenetic phase that replaced parts of many different depositional facies during moderately deep burial (J.A.D. Dickson, personal communication, 1989). Dolomite has generally lower porosity (average of 8.3%) and higher permeability (average horizontal and vertical permeabilities of 894 and 334 md, respectively) than limestones (average porosity of 11.2%; average horizontal and vertical permeabilities of 165 and 11 md, respectively) (Table 2; Figure 10). Dolomites with substantial vuggy and coarse intercrystalline porosity have very high permeability (>500 md). Shale is present in small amounts (<1%); however, it is locally important as a barrier to vertical fluid flow. Although porosity and
permeability are variable,
Production History
Reinecke field was discovered in 1950 at
depths of approximately 6700 ft (-4300 ft, 1310 m subsea). The oil was
42o API with a gas-oil ratio of 1266 ft3/bbl.
Coning of bottom water was recognized as a problem early in the
development of the field. Consequently, most wells were completed open
hole after penetrating only a few feet of porosity in the upper part of
the This As the model in
Figure 14C shows, much residual oil (oil that will not naturally
flow and is trapped in pores) remains in the Reinecke ConclusionsThe References Cited
Crawford, G.A., G.E. Moore, and W. Simpson, 1984,
Depositional and diagenetic controls on Galloway, W.E., T.E. Ewing, C. M. Garrett, N. Tyler, and D. G. Bebout, 1983, Atlas of major Texas oil reservoirs: Texas Bureau of Economic Geology, 139p.
Saller, A.H., A.W. Walden, S. Robertson, M. Steckel, J.
Schwab, H. Hagiwara, and S. Mizohata, 1999, Veevers, J.J., and C.McA. Powell, 1987, Late Paleozoic glacial episodes in Gondwanaland reflected in transgressive-regressive depositional systems in Euramerica: Geological Society of America Bulletin, v. 98, p. 475-487. Vest, E.L., 1970, Oil fields of Pennsylvanian-Permian, Horseshoe Atoll, west Texas, in M.T. Halbouty, ed., Geology of giant petroleum fields: AAPG Memoir 14, p.185-203. Acknowledgments
This
chapter describes part of the results of a joint Unocal-Japan National
Oil Company |