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Exploration
Play Analysis from a Sequence Stratigraphic Perspective
By
John W. Snedden1, J. F. (Rick) Sarg1, and Xudong (Don) Ying2
Search and Discovery Article #40079 (2003)
1ExxonMobil
Exploration Company, P.O. Box 4778, Houston, Texas 77210-4778
([email protected];
[email protected])
2ExxonMobil Upstream Research Company, P.O. Box 2189 · Houston, TX. 77252-2189 ([email protected]).
Abstract
Examination of
exploration drilling histories for many different global basins indicates a
counter-intuitive temporal and spatial pattern
in the way hydrocarbons are sometimes discovered.
Conventional wisdom holds that for any given basin or play, a plot of cumulative
discovered hydrocarbon volumes versus time or number of wells drilled usually
show a steep curve (rapidly increasing volumes) early in the play history and a
later plateau or terrace (slowly increasing volumes). Such a plot is called a
creaming curve, as early success in a play is thought to inevitably give way to
later failure as the play or basin is drilled-up. It is commonly thought that
the "cream of the crop" of any play or basin is found early in the drilling
history.
By examining plays or basins with sufficiently long drilling histories and range of reservoir paleoenvironment and trap types, one actually finds two or three "terraces" to the creaming curve. The first string of successes in a given basin usually corresponds to exploitation of the highstand systems tract or sequence set reservoirs developed in updip structural traps. These reservoirs are typically marginal to shallow marine "shelfal" deposits, laterally continuous but lacking internal sealing facies and are seldom self-sourcing. The second or third terrace in the creaming curve usually involves the lowstand reservoir component (systems tract or sequence set), which is often developed in downdip deepwater or slope paleoenvironments. Transgressive (systems tract or sequence set) reservoirs, typically shallow marine shelfal sandstones that are sometimes self-sourced, are variably developed and may or may not occupy the second terrace of the creaming curve. These trends hold true for both 2nd-order (3-10 my) and/or third-order (1-3 my) stratigraphic cycles, depending upon the scale of the basin or play.
This analysis fits well
with the definition of an exploration play provided by Magoon and Sanchez
(1995): a fully developed play is the simple volume difference between the
petroleum system capability and the current discovered hydrocarbon volumes
(commercial or not). Where the difference is large, either the petroleum system
has significant leakage problems (e.g., Barents Sea Mesozoic play) or the
lowstand systems tract or sequence set has not been fully exploited.
Examples supporting these ideas
are drawn from several global basins (Gulf of Mexico Miocene, Norway Upper
Jurassic, Mahakam Delta, Texas Wilcox). Case studies demonstrate how critical
elements of exploration risk shift from trap and seal in highstand plays to
reservoir and source in lowstand components of these plays.
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uWilcox play, Lower coastal zone, Texas uPlio-Miocene play, Kutei Basin, Indonesia uCreaming curve as predictive tool
uWilcox play, Lower coastal zone, Texas uPlio-Miocene play, Kutei Basin, Indonesia uCreaming curve as predictive tool
uWilcox play, Lower coastal zone, Texas uPlio-Miocene play, Kutei Basin, Indonesia uCreaming curve as predictive tool
uWilcox play, Lower coastal zone, Texas uPlio-Miocene play, Kutei Basin, Indonesia uCreaming curve as predictive tool
uWilcox play, Lower coastal zone, Texas uPlio-Miocene play, Kutei Basin, Indonesia uCreaming curve as predictive tool
uWilcox play, Lower coastal zone, Texas uPlio-Miocene play, Kutei Basin, Indonesia uCreaming curve as predictive tool
uWilcox play, Lower coastal zone, Texas uPlio-Miocene play, Kutei Basin, Indonesia uCreaming curve as predictive tool
uWilcox play, Lower coastal zone, Texas uPlio-Miocene play, Kutei Basin, Indonesia uCreaming curve as predictive tool
uWilcox play, Lower coastal zone, Texas uPlio-Miocene play, Kutei Basin, Indonesia uCreaming curve as predictive tool
uWilcox play, Lower coastal zone, Texas uPlio-Miocene play, Kutei Basin, Indonesia uCreaming curve as predictive tool
uWilcox play, Lower coastal zone, Texas uPlio-Miocene play, Kutei Basin, Indonesia uCreaming curve as predictive tool
uWilcox play, Lower coastal zone, Texas uPlio-Miocene play, Kutei Basin, Indonesia uCreaming curve as predictive tool
uWilcox play, Lower coastal zone, Texas uPlio-Miocene play, Kutei Basin, Indonesia uCreaming curve as predictive tool
uWilcox play, Lower coastal zone, Texas uPlio-Miocene play, Kutei Basin, Indonesia uCreaming curve as predictive tool
uWilcox play, Lower coastal zone, Texas uPlio-Miocene play, Kutei Basin, Indonesia uCreaming curve as predictive tool
uWilcox play, Lower coastal zone, Texas uPlio-Miocene play, Kutei Basin, Indonesia uCreaming curve as predictive tool
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Introduction
One of the most
critical tasks faced by petroleum industry geoscientists relates to the
decision to enter into an
Explorationists use
a variety of methods to evaluate oil and gas plays. One of these is the
“creaming curve”, basically a graph of cumulative discovered hydrocarbon
volumes versus time or number of wells drilled (Figure 1). This type of
plot, formalized by Meisner and Demirmen (1981), is used to forecast
future
One example of the
diminishing effectiveness of However, this simple creaming pattern of a rising limb (immature phase) and a long, final plateau (mature phase) is not universal. Some plays exhibit more complex histories of drilling success, with multiple rising limbs and plateaus, suggesting that other factors are at work (Figure 3).
One could explain more complex play histories from a sequence
stratigraphic standpoint. In fact, the sequence stratigraphic model
predicts that an ideal creaming curve for an
The sequence stratigraphic paradigm (Figure 4) would also explain or
predict a second set of paired rising limb and plateau as
The second or third pair of rising limbs and plateaus (Figure 4) often
come from discoveries in lowstand systems tract (LST) or lowstand sequence
set (LSS) reservoirs and traps. There are several reasons for this
observed pattern.
After providing definitions of key terms, this paper will describe several
Definitions
The creaming curve method of analysis focuses upon a petroleum province
in a given geographic area with known commercial accumulations. The
petroleum province being analyzed need not have distinct geologic,
tectonic, or oil-accumulation properties or boundaries (Meisner and
Demirmen, 1981). In practice, the creaming method is typically applied to
In relatively large
petroleum provinces like the U. S. Gulf of Mexico Basin, one could argue
that Many of the plays discussed in this paper cover thick stratigraphic intervals where interpretations are made at the 2nd-order level, as per the definitions of Mitchum and Van Wagoner (1991). In these thick successions, stacked packages of sequences make up individual highstand, transgressive, or lowstand sequence sets (Figure 5). Embedded within these sequence sets and sequences are the individual systems tracts where stacked reservoirs form the main field pay zones. For example, the lowstand systems tract in progradational (highstand) sequence sets often contains a high percentage of the net reservoir thickness (e.g., Hentz et al., 2002). These lowstand systems tract reservoirs (incised valley-fill, slope channels, etc) are often located within the shelf domain for the lower-order sequence set, giving rise to some confusion when discussing the depositional position on the shelf to basin profile (Figure 5). The vertical stacking patterns of these successions give some hint as to the long-term trend of relative sea level and accommodation. These criteria are used to define the sequence sets and systems tracts in the cases described. In some cases, global charts (e.g., de Gracianksy et al., 1999) can used to define the sequence sets, where biostratigraphic data is convincing. Miocene Play, Gulf of Mexico, USA
The Miocene play of the
Gulf of Mexico clearly meets the criteria for creaming curve analysis
as it has a sufficiently long Stratigraphic subdivisions of highstand, transgressive, and lowstand systems tracts or sequence sets are easily delineated from available published statistics and classifications. The most complete database is that of the Bureau of Economic Geology (Seni et al., 1994, 1995). While this published database did not use precise sequence stratigraphic terminology, their architectural terminology is easily translated into the sequence stratigraphy nomenclature: · Progradational: highstand systems tract (HST) or highstand sequence set (HSS) · Retrogradational: transgressive systems tract (TST) or transgressive sequence set (TSS) · Submarine Fan: Lowstand systems tract (LST) or lowstand sequence set (LSS) · Aggradational: HST-HSS or LST-LSS While the aggradational classification spanned several sequence stratigraphic divisions, it did not represent significant volumes in comparison to other groupings. The Gulf of Mexico Miocene play spans about 15 to 18 million years of geologic time, thus it encompasses at least one 2nd-order cycle. While the play can be discussed from the perspective of the sequence set on the gross scale, clearly smaller components (sequences and systems tracts) contain the actual reservoirs at the individual field and discovery scale.
The Miocene play displays the pattern expected from progressive
The Miocene TSS has not really yielded significant hydrocarbon volumes in the Miocene, as it is normally quite shale-prone in all stratigraphic levels in the high subsidence regime of the Gulf of Mexico (Armentrout, 1991; Diegel et al., 2001). Thinning landward in these passive margin settings often makes the embedded TST's look eroded, though this apparent truncation is clearly a function of the seismic resolution (Mitchum et al., 1994). However, the cumulative discovery curve for the Miocene play shows an abrupt increase beginning in the 1980’s as the deepwater sandstones of the LSS were penetrated. Beginning in the early 1980’s, there is a pronounced increase in discovered volumes as reservoirs of the paleo-deepwater slope channels, and basin floor amalgamated channels and sheets were drilled in progressively deeper water (Lawrence, 1997). With the Thunder Horse field discovery in 1999, cumulative discovered volumes for the LSS component of the Miocene play now exceeds that of the HSS component.
Thus, the suggested pattern of multiple rises and plateaus is quite
apparent in the creaming curves for the three stratigraphic components of
the Gulf of Mexico Miocene. The HSS plateau is followed by the LSS rising
limb, which apparently is still in the “immature” phase of
It is illuminating to consider the causes for the mid-1980’s jump in
Upper Jurassic Play, NorwayThe Upper Jurassic of the Horda Platform and adjacent Norwegian Sea of Norway is a well-established producer of both oil and gas (Figure 7). Hydrocarbons in the Upper Jurassic were identified initially in 1975, but giant accumulations of gas were found with the discovery of Troll West in 1978 and Troll East in 1983 (Gray, 1987). Hydrocarbons in the Upper Jurassic of the Troll Field (West and East) are trapped in a large fault-bounded, horst structure (Figure 8). A large gas column and smaller oil column extends across a stacked series of HST and TST shallow marine sandstone reservoirs of the Sognefjord and Fensfjord Formations (Gibbons et al., 1993). This composite succession of HST’s and TST’s forms a classic Highstand Sequence Set (HSS), with an overall progradational stacking pattern. Thus, the first portion of the creaming curve for the Upper Jurassic follows the expected early pattern for play development: discoveries in the highstand component of the 2nd order cycle (sequence set) in large structural closures (Figure 4). Reservoirs of the Sognefjord and Fensfjord do extend laterally a considerable distance and thus would not trap hydrocarbons without a significant structural closure (Van der Zwan, 1989). A smaller (by comparison) discovery came a few years later in 1984 at the Draugen Field, which reservoired in similar age sandstones on the Trondelag Platform much further north (Figure 7). Unlike Troll Field, Draugen Field does not exhibit a large pronounced structural closure. A stratigraphic component for entrapment is provided by the lateral pinchout of the sandstone reservoirs (Provan, 1993). Sandstones are also shallow marine in origin, with obvious shelfal indicators like ammonite shells and marine dinocysts (Van der Zwan, 1989). The Draugen Field thus represents the second of the three sequence stratigraphic tiers: transgressive shallow marine sandstones in stratigraphic traps (c.f. Figure 4). The third tier to the Upper Jurassic Play came over twenty years later in 1996, with discovery of the Fram Field in Block 35/11 (Figure 7). Initial tests of the Sognefjord Formation reservoirs yielded over 4400 BOPD with associated oil (AAPG Explorer, 1996). Sandstone reservoirs are interpreted to be paleo-deepwater high-density turbidites deposited in a lowstand submarine fan system (S. Setterdahl, personal communicaton). The discovery was made with the eighth well drilled in the block. Fram is currently waiting on field development, with first oil expected in 2003. The discovery of the Fram Field proved that a third component to the Upper Jurassic play exists and additional drilling has pursued this component. Thus, this play fits the sequence stratigraphic prediction for 1) highstand structural component (Troll); 2) transgressive stratigraphic (Draugen); and 3) lowstand deepwater (Fram). Wilcox Play, Lower Coastal zone, Texas, USA
The Wilcox Play of
Texas also has a long The second set of discoveries in the Wilcox play of Texas began in the mid-1960’s with discovery of the Laredo Field (1.0 TCFG OGIP) in South Texas. Laredo and other fields in the immediate area produce from a transgressive succession of shallow marine sandstones known informally as the “Lobo” series. Lobo sandstones harbor gas in a combination structural-stratigraphic trap with small scale faults and sealing by unconformities at the upper and lower Lobo levels (Figure 11). These subtle traps are typical of the second tier or “transgressive” component of the creaming curve. The third tier of the Wilcox came over 15 years later as the downdip (lowstand) Wilcox component began to be exploited by South Texas majors and independents (Figure 9). Deeper drilling and higher gas prices in the late 1970’s led to discoveries in the Seven Sisters, East (Duval County) and Fandango Fields (Zapata County). These fields are different in terms of structural style: thick growth wedges developed on the downthrown side of major listric faults (Edwards, 1981). Structural closure is provided by rollover into the faults (Stricklin, 1994). However, detailed stratigraphic analysis of the Wilcox in South Texas area reveals that conventional log correlation sometime fails to discern the presence of lowstand packages of older Wilcox Group sandstone reservoirs (Figure 12). Assumptions about growth in younger Wilcox strata are sometimes refuted by biostratigraphic information and sequence stratigraphic correlations (Snedden et al., 1991; Snedden et al., 1996b). In the East Seven Sisters Area of Duval and McMullen counties, for example, this information confirms the presence of thick, Paleocene-age, lowstand wedge prograding complexes which pinchout updip onto a coeval sequence boundary, forming a bypass surface (Figure 13). The sequence stratigraphic model predicts that detached sandstone packages (lowstand wedge prograding complex) will sometimes be located downdip of coeval unconformities due to bypass during relative sea level lowstands (Posamentier et al., 1993). Follow-up to the downdip Wilcox discoveries occurred in the middle 1990’s with major gas finds like the Bob West Field in Zapata and Starr Counties (Jones, 1994), but these basically follow the same trap and reservoir type as the Seven Sisters East Field. Since the first plateau in the 1950’s, about 6.0 TCFG (OGIP) has been discovered in the Wilcox play. One key difference between the Wilcox play and other examples discussed thus far is the fact that Wilcox reservoirs, even in the lowstand sequence set, do not develop significant deepwater reservoir elements (Stricklin, 1994). Reconstructions suggest that the Wilcox Group in South Texas represents a progradation of shallow water siliciclastics into a major depocenter seaward of the Cretaceous shelf margin, an area of massive accommodation due to collapse of an autochthonous Mesozoic salt massif (Diegel et al., 2001). Sediment supply kept pace with subsidence, thus limiting bypass to basinal paleoenvironments and accommodating most sediment in lowstand, shelf-margin deltaic complexes (Edwards, 1981). Retrogradational failure of the shelf margin has also created accommodation in this strike-trending depocenter (Edwards, 2001). The few, well-documented deepwater sandstones encountered in fields like Northeast Thompsonville in Jim Hogg County have been relatively poor producers due to low net/gross and limited reservoir quality (Snedden et al. 1996b). Plio-Miocene Play, Kutei Basin, Indonesia
A final example of an
However, With limited well data and a detailed geochemical and stratigraphic model as support, the authors postulated a pre-drill model that these LSS reservoirs would be: 1) present in economic thickness; and 2) sourced by a series of “lowstand kitchens” (Snedden et al., 1996a). Lowstand kitchens were described as areas where terrestrial organic matter had been transported by lowstand bypass, collected, matured, and expelled oil and gas into the LSS reservoirs (Figure 14; Peters et al., 2000). Following completion of detailed studies and recommendations to drill, and in partnership with a new operator (Unocal), a series of wells were drilled in deepwater regime of the Kutei Basin and adjacent Makassar straits. Recent successes in the Merah-Besar, Seno, and West Seno in the Makassar PSC have proven the presence of both adequate transported terrestrial organics (Dunham et al., 2000) and reservoir in the lowstand component of the Plio-Miocene play (Saller et al., 2000). Using the Creaming Curve as a Predictive Tool
As the Kutei Basin
example superbly demonstrates, there is some utility to recognizing the
potential for a second or third “tier” to a given One way to identify an under- or unexplored play is to compile field statistics by systems tracts or sequence set-type. For example, analysis of the Texas lower coastal province (onshore) reveals that the HST (HSS) components contains the bulk of gas reserves discovered to date in 32 onshore plays (inset, Figure 15). This predominance of fields developed in structural traps in thick, laterally continuous shallow water sandstones of the HST or HSS accounts for such a disparity (Kosters et al., 1989). Examination of the same 32 onshore plays indicates that in less than a third of these produce from more than two systems tracts or sequence sets, with an additional 30% limited to one systems tract or sequence set (Figure 16). While there may be good reasons for such differences (e.g., burial diagenesis in deeper, more basinward components, stratigraphic trap failure, low sand content in the TST-TSS), the trend in all 32 onshore plays is suspicious, suggesting underexplored plays. In fact, Kosters et al. (1989) has estimated that 20 TCFG of undiscovered, recoverable gas reserves remains in the Lower coastal province of Texas. A rough estimate of the partitioning of reserves suggests that most of the future potential lies in the lowstand systems tracts or sequence sets of these 32 existing plays (Figure 15).
Understanding the
natural progression of an Summary and Conclusions
The creaming curve
method has proven to be a useful tool in Of course, caveats should be offered in any case. Some plays do not develop the full range of sequence stratigraphic components, simply because natural conditions do not allow it. The Wilcox play of South Texas has failed to exhibit a significant paleo-deepwater reservoir play because of the high accommodation of shelf margin deltaics and limitations on bypass and deep burial diagenesis of the relatively finer grained, isolated slope channels. Some plays fail completely because critical elements are never de-risked to a sufficient level to warrant additional drilling (e.g., Barents Shelf Jurassic play due to seal failure; Berge, 1997).
AcknowledgementsThe authors would like to acknowledge technical input and discussions with Jeff Brown, Pete Rose, Stephen Setterdahl, Kenneth Petersen, John Armentrout, John Suter, Jeff Faber, and Art Saller. Reviews by Jory Pacht, Hongliu. Zeng, Jeanne Phelps, and John Armentrout are greatly appreciated. ReferencesAhlbrandt, T.S., 2000, U.S. Geological Survey World Petroleum Assessment 2000: Multi-Volume CD-ROM set, United States Geological Survey Digital Data Series, DDS-60. Antosh, N., 2001, Deeper than the ocean/Gulf canyons hide strange creatures and topography, plus huge supply of oil, gas: Houston Chronicle Archives, 8/12/01, http://www.chron.com/content/archiv. Armentrout, J.M., 1991, Paleontologic constraints on depositional modeling: examples of integration of biostratigraphy and seismic stratigraphy, Plio-Pleistocene, Gulf of Mexico, in, Weimer, P., and M.A. Link, eds., Seismic Facies and Sedimentary Processes of Submarine Fans and Turbidite Systems, Elsevier, Amsterdam, p. 137-170. Bartek, L R., P.R. Vail, J.B. Anderson, P.A. Emmet, and S. Wu, 1991, Effect of Cenozoic ice sheet fluctuations in Antarctica on the stratigraphic signature of the Neogene: Journal of Geophysical Research, v. 96, no. B4, p. 6753-6778. Bebout, D.G., B.R. Weise, A.R. Gregory, and M.B. Edwards, 1982, Wilcox sandstone reservoirs in the deep subsurface along the Texas Gulf Coast, their potential for production of geopressured geothermal energy: The Univ. of Texas at Austin, Bureau of Economic Geology Report of Investigations, no. 117, 125 pp. Berge, G. 1997, Discoveries on the Norwegian continental shelf: Norwegian Petroleum Directorate, 32 p. Bourgeois, T.M., D.G. Godfrey, M.J. Bailey, 1998, Race on for deepwater acreage, 3,500 meter depth capability: Offshore, October, 1998, p. 40-41. Brown, P.J., and P.R. Rose, 2002, Plays and concessions—a straightforward method for assessing volumes, values, and chance: Search and Discovery website, http://searchanddiscovery.com/documents/brown/index.htm., 10 p. Diegel, E.A., D.C. Schuster, J.F. Karlo, R.C.Shoup, and P.R. Tauvers, 2001, Cenozoic structural evolution and tectono-stratigraphic framework of the northern Gulf Coast continental margin: Search and Discovery website, http://searchanddiscovery.com/documents/97021/index.htm., 34 p. Dunham, J.B., T.J. Brown, R. Lin, R.B. Redhead, H.F. Schwing, and S.H. Shirley, 2000, Transport and concentration of gas- and oil-prone kerogens into deepwater sediments of the Kutei Basin, East Kalimantan., Indonesia: AAPG International Meeting, Oct. 15-18, 2000 (abstract). Duval, B.C., C. de Janvry, and B. Loiret, 1992, Detailed geoscience reinterpretation of Indonesia's Mahakam delta scores: Oil and Gas Journal, p. 67-72. Edwards, M.B., 1981, Upper Wilcox Rosita delta system of south Texas: growth-faulted shelf-edge deltas: AAPG Bulletin, v. 65, p. 54-73. Edwards, M.B., 2001, Origin and significance of retrograde failed shelf margins; Tertiary northern Gulf Coast Basin: Search and Discovery website, http://searchanddiscovery.com/documents/edwards/index.htm., 15 p.
George, D., 1996, Remote and deepwater frontier areas seeing more
Gibbons, K., T. Hellam, A. Kjemperud, S. Nio, and K. Vebenstad, 1993, Sequence architecture, facies development, and carbonate-cemented horizons in the Troll Field reservoir. Offshore Norway, in, A. Hurst. ed., Advances in Reservoir Geology: Geological Society of London Special Publication, no. 69, p. 1-31. de Graciansky, P.C. , J. Hardenbol, T. Jacquin, P.R. Vail, 1998, Mesozoic and Cenozoic Sequence Stratigraphy of European Basins: SEPM Special Publication no. 60, 783 pp. Gray, D.I., 1987, Troll, in, A.M. Spencer,., ed., Geology of the Norwegian Oil and Gas Fields: Graham and Trotman, London, p. 389-401. Greenlee, S.P., W.J. Devlin, K.G. Miller,G.S. Mountain, and P.B. Flemings,., 1992, Integrated sequence stratigraphy of Neogene deposits, New Jersey continental shelf and slope: comparison with Exxon model: Geological Society of America Bulletin, v. 104, p. 1403-1411. Halbouty, M.T., A.A. Meyerhoff, R.E. King, R.H. Dott, Sr., H. Douglas Y. Klemme, and T. Shabad, 1970, World’s giant oil and gas fields, geologic factors affecting their formation, and basin classification [Part 1], in, M.T. Halbouty, ed., Geology of Giant Petroleum Fields: AAPG Memoir 14, p. 502-528. Hentz, T.F., H. Zeng, L.J. Wood,., 2002, Sequence stratigraphy and hydrocarbon distribution of Miocene plays: a case study from Starfak and Tiger Shoal Fields, Offshore Louisiana: AAPG Annual Meeting, Houston, Texas, March 10-13, 2002 (abstract). Huffington, R.M., and H.M. Helmig, 1980, Discovery and development of the Badak Field, east Kalimantan, Indonesia: AAPG Giant Fields, p. 441-458. Imbert, P., J.L. Pittion, and A.K. Yeats, 1996, Heavier hydrocarbons, cooler environment found in deepwater: Offshore, April, 1996, p. 47-55. Johannessen, E.P., R. Mjos, D. Renshaw, A. Dalland, and T. Jacobsen, 1995, Northern limit of the “Brent Delta” at the Tampen Spur—A sequence stratigraphic approach for sandstone prediction, in, Steel, R.J., V.L. Felt, E.P. Johannessen, and C. Mathieu, eds., Sequence Stratigraphy on the Northwest European Margin: Elsevier, Amsterdam, p. 213-256. Jones, W.E., 1994, Bob West Field-Zapata and Starr Counties, a developing giant: South Texas Geological Society Bulletin, v. 34, no. 5, p. 13-33. Kosters, E.C. et al., 1989, Atlas of Major Texas Gas Reservoirs: Gas Research Institute, University of Texas at Austin, Bureau of Economic Geology, 161 p.
Lawrence, D.T., 1997, Gulf of Mexico shelf, Magoon, L.B., and W.G. Dow, 1994, The petroleum system, in, Magoon, L.B., and W.G. Dow, eds, The Petroleum System-from Source to Trap: AAPG Memoir 60, p. 3-24. Magoon, L.B., and R.M.O. Sanchez, 1995, Beyond the petroleum system: AAPG Bulletin, v. 79, no. 12, p. 1731-1736. Meisner, J. and F. Demirmen, 1981, The creaming method: a
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H.W., G.P. Allen, D.P. James,., and M. Tesson, 1993, Forced regressions in
a sequence stratigraphic framework: concepts, examples, and Provan, D.M.J., 1993, Draugen oil field, Haltenbanken Province, Offshore Norway: in. M.T. Halbouty, ed., Giant Oil and Gas Fields of the Decade 1978-1988, AAPG Memoir 54, p. 371-382. Saller, A., T. Brown, R. Redhead, H. Schwing, and J. Inaray, 2000, Deepwater depositional facies and their reservoir characteristics, West Seno Field, Offshore East Kalimantan, Indonesia: AAPG International Meeting, Oct. 15-18, 2000 (abstract). Seni, S.J., Tremblay, T.T., and D.A. Salazar, 1994, Atlas of Northern Gulf of Mexico Gas and Oil reservoirs: GIS Files and Tabular data: Bureau of Economic Geology and Minerals Management Service CD-ROM. Seni, S., J. Brooke, D. Marin, and E. Kazanis, 1995, Chronostratigraphic hydrocarbon plays and depositional styles in the northern Gulf of Mexico: GCAGS Transactions, v. 45, p. 519-528. Snedden, J.W., J.C. Cooke, R.K. Johnson, and K.T. Conrad, 1991, Sequence stratigraphy and sedimentology of a shelf-margin lowstand wedge in the deep Wilcox Flexure Trend of South Texas: American Association of Petroleum Geologists, Bulletin, v. 75, p. 673 (abstract). Snedden, J.W., J.F. (Rick) Sarg, M.J. Clutson, M. Maas, T.E. Okon, M.H. Carter, B.S Smith, T.H. Kolich, and Md. Y. Mansor, 1996a, Using sequence stratigraphic methods in high-supply deltas: examples from the ancient Mahakam and Rajang-Lupar deltas: Proceedings, Indonesian Petroleum Association, 25th Annual Convention, p. 281-295.
Snedden, J.W., Sarg, J.F., Faber, J.A., and J. Brown, 1996b, Downdip
plays: highstand versus lowstand Steinshouser, D.W., J. Qiang, P.J. McCabe, and R.T. Ryer, 1999, Maps showing geology, oil and gas fields, and geologic provinces of the Asia Pacific Region: United States Geological Survey, Open File report 97-470F, CD-ROM. Stricklin, F.L., 1994, Genetic variations in a growth-fault system: downdip Wilcox trend of south Texas: Transactions Gulf Coast Association Geological Societies, v. 44, p. 717-723. Van der Zwan, C.J., 1989, Palynostratigraphic principles as applied in the Jurassic of the Troll and Draugen Field areas, offshore Norway: in, Collinson, J., ed., Correlation in Hydrocarbon Provinces: Graham and Trotman, London, p. 357-365. Wilgus. C.K., et al., 1988, Sea-level Changes, An Integrated Approach: SEPM Special Publication No. 42, 400 p. About the AuthorsJohn W. Snedden
John W. Snedden is currently Stratigraphy
skill area advisor with ExxonMobil J.F. 'Rick' Sarg
Rick Sarg is Stratigraphy Coordinator, ExxonMobil Don X. Ying Don Ying is a senior research
geologist in ExxonMobil Upstream Research Company. He joined Mobil
His petroleum career started
with Research Institute of Petroleum His current research interests
are developing processes and workflows that enable geosciensts to build
realistic geologic models during different business stages of petroleum
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Figure 1. Idealized simple
creaming curve (cumulative discovered volumes versus time).
Figure 2. Creaming curve for the Middle Jurassic Play, United Kingdom,
Norway, and Denmark. Data from Berge (1997). MMBOE=million barrels oil
equivalent.
Figure 3. Creaming curve for
the Kutei Basin. Data from Ahlbrandt (2000), Petroconsultants (1998), and
Steinshouser et al. (1999). MMBOE=million barrels oil equivalent.
Figure 4. Idealized creaming curve from a sequence stratigraphic
perspective.
Figure 5. Idealized succession of lowstand, transgressive, and highstand
sequence sets, each made up of sequences with embedded third-order
lowstand, transgressive, and highstand systems tracts.
Figure 6. Creaming Curve for Miocene Play, Gulf of
Mexico, with individual components plotted separately.
Figure 7. Creaming curve for the Upper Jurassic Play, Norway.
Figure 8. Cross-section through
Troll West Field, Norway. Modified from Gibbons et al. (1993). 
Figure 9. Creaming curve,
Wilcox Play, Texas. OGIP=original gas in place, Trillion cubic feet.
Figure 10. A) Lake Creek structure map, top of Wilcox P zone; B) Well-log
showing thick sandstones of the overlying G and H zones; C) Lateral
continuity of braided fluvial channels and incised valley-fills in the G
and H zones.
Figure 11. Idealized Wilcox
Lobo transgressive combination structural-stratigraphic trap type.
Figure 12. Alternative models
for Wilcox growth wedges. A. Conventional, well log (lithostratigraphic)
correlation holds that expansion across major growth faults is limited to
Upper Wilcox Group and overlying Queen City Formations. B. Queen City and
Upper Wilcox growth is more limited. Model provides for inclusion of an
older Wilcox wedge on the downdip side of fault and a coeval updip
unconformity. 
Figure 13. Sequence stratigraphic correlation of Wilcox sandstones in the
East Seven Sisters area of Duval and McMullen counties, Texas.
Figure 14. Stratigraphic model
for the Plio-Miocene play of the Kutei basin, Indonesia. Modified from
Peters et al. (1998). 
Figure 15. Future potential by sequence stratigraphic package, onshore
Gulf of Mexico, Lower coastal province, Texas (n=32 plays). 
Figure 16. Systems tract/sequence sets with significant hydrocarbon
content in 32 onshore plays, Lower Coastal of Texas.