The Impact of Parasequence Stacking Patterns on Vertical Connectivity Between Wave-Dominated, Shallow Marine Parasequences, Book Cliffs, Eastern Utah

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The Impact of Parasequence Stacking Patterns on Vertical Connectivity Between Wave-Dominated, Shallow Marine Parasequences, Book Cliffs, Eastern Utah MALCOLM J. ARNOT and TIMOTHY R. GOOD* MALCOLM J.

Department of Petroleum Engineering, Heriot-Watt University Edinburgh, EH14 4AS, Scotland malcolm_arnot@pet.hw.ac.

uk/tim_good@pet.hw.ac.uk Within shallow marine reservoirs, the vertical connectivity between shoreface sandstones in adjacent parasequences may have a significant impact on reservoir flow.

of vertical connectivity between adjacent parasequences.

1 The Impact of Parasequence Stacking Patterns on Vertical Connectivity Between Wave-Dominated, Shallow Marine Parasequences, Book Cliffs, Eastern Utah MALCOLM J. ARNOT and TIMOTHY R. GOOD* MALCOLM J. ARNOT and TIMOTHY R. GOOD Department of Petroleum Engineering, Heriot-Watt University Edinburgh, EH14 4AS, U.K. Department of Petroleum Engineering, Heriot-Watt University Edinburgh, EH14 4AS, Scotland Within shallow marine reservoirs, the vertical connectivity between shoreface sandstones in adjacent parasequences may have a significant impact on reservoir flow. The lateral extent of marine flooding surface shales and updip coastal plain coals/lagoonal shales, which overlie parasequence boundaries, is likely to be the critical factors controlling the degree of vertical connectivity between adjacent parasequences. The upper Campanian Blackhawk Formation, exposed along the Book Cliffs in east-central Utah, can be traced for approximately 160 miles (260 km) from near Helper City to the Utah-Colorado border. The Blackhawk Formation comprises six lithostratigraphic units: the, Aberdeen Member, Kenilworth Member, Sunnyside Member, and Desert Member (Young, 1957 and Balsley, 1980), which comprise predominantly marine sandstone bodies that prograded into the Western Interior Seaway. More recently, eight high frequency sequences have been defined in the Blackhawk Formation by Van Wagoner et al. (1990), Taylor and Lovell (1991) and O'Byrne and Flint (1995). The lower sequences are characterized by aggradational parasequence stacking patterns. In contrast, higher sequences are characterized by more progradational parasequence stacking patterns (O'Byrne and Flint, 1995). Outcrop studies were undertaken on the and Spring canyon Member to collect data on the lateral extent of shales and coals overlying parasequence boundaries. These studies show that marine flooding surface shales do not have simple updip terminations but may pass laterally into a zone of discontinuous shales overlying shoreface sandstones of the underlying parasequence. It was also found that, within the, which occurs in the upper part of the Blackhawk Formation and has a strongly progradational stacking pattern, the zone of vertical connectivity between parasequences is on the order of 1000's of meters. In contrast, within the Spring Canyon Member, which has a more aggradational parasequence stacking pattern, the zone of vertical connectivity is only on the order of 100's of meters. The results from this study highlight the importance of applying sequence stratigraphic concepts to shallow marine reservoirs. Perhaps more importantly, it suggests that developing quantitative sequence stratigraphic frameworks at outcrop may enable predictive relationships to be developed between parasequence stacking patterns and the expected vertical connectivity between adjacent parasequences. Application of these relationships in reservoir modelling studies may then improve predictions of fluid flow in subsurface cases. Presented at: 1998 AAPG Annual Convention, Salt Lake City May 17th -20th Session: Quantifying Stratigraphy and Sedimentology for Reservoir Modeling Acknowledgments This work was undertaken as part of the Genetic Units Project at Heriot-Watt University. The authors would like to thank the following sponsoring companies for their support: British Gas PETRO-CANADA STATOIL * Tim Good is now at Mobil Technology Company, Dallas, Texas 75244

2 OUTCROP ANALOGUE LOCATION AND STRATIGRAPHY The upper Campanian Blackhawk Formation, exposed along the Book Cliffs in eastern Utah, can be traced for approximately 160 miles (260km) from near Helper City to the Utah- Colorado border. These exposures enable the architecture and stacking patterns of shoreface parasequences to be examined in detail. UPPER CRETACEOUS PALAEOGEOGRAPHY CANADA UNITED STATES UPLANDS SHELF BASIN STUDY AREA Uplands COASTAL PLAIN STUDY AREA: BOOK CLIFFS UTAH Shelf Study Area N Utah Study Area UNITED STATES MEXICO After Swift et al., (1987) Basin Helper Price Book Cliffs km 0 10 km BLACKHAWK FORMATION STRATIGRAPHY Study Area Green River Campanian Blackhawk Fm. Price River Fm. Buck Tongue Castlegate M. Desert M. Grassy M. Sunnyside M. Kenilworth M. Aberdeen M. Spring Canyon M. Outcrop data for this study have been collected from the Spring Canyon Member and of the Blackhawk Formation. Both the and the Grassy Member can be traced along depositional dip for approximately 30 km. Star Point Fm. Storrs Tongue Panther Tongue The Blackhawk Formation comprises a progradational succession of shoreface sandstones which advanced eastwards into the Western Interior Basin. The Spring Canyon Member is the lowest progradational sandstone of the Blackhawk Formation and the is one of the upper progradational sandstones. SPRING CANYON MEMBER STRATIGRAPHY GRASSY MEMBER STRATIGRAPHY SCPS1 SCPS2 SCPS3 SCPS4 SCPS5 SCPS6 Desert Member Desert Sequence 2 Desert Sequence 1 GSB3 Grassy Sequence 2 GSB2 Grassy Sequence 1 (GPS2) (GPS1) (GPS2) (GPS3) (GPS4) Outcrop Data Collection SCPS7 GSB1 Sunnyside Member Highstand:Coastal plain/lagoonal- Marine Shale (Mancos Shale) After Kamola and Van Wagoner (1995) Lowstand: Fluvialestuarine Incision Highstand:Coastal plain/lagoonal- Marine Shale (Mancos Shale) Modified from O'Byrne and Flint (1995) The comprises at least 7 progradationally stacked shoreface parasequences. The upper 4 parasequences (SCPS1-4) are exposed along the Book Cliffs near the town of Helper. The flooding surface shales and coastal plain coals/lagoonal shales that mark the parasequence boundary between SCPS3 and SCPS4 (outlined by red box) were examined in detail for this study. The comprises two uncomformitybounded, high frequency sequences. Each sequence contains two progradational parasequences. The discontinuous shales along the parasequence boundary between and were examined in detail for this study.

DISCONTINUOUS INTER-SANDSTONE SHALES IN SHALLOW MARINE SANDSTONES Outcrop studies undertaken on the Grassy Member and show that laterally continuous flooding surface shales overlying parasequence

Further updip, the flooding surface shales may pass into discontinuous coals or lagoonal shales.

3 DISCONTINUOUS INTER-SANDSTONE SHALES IN SHALLOW MARINE SANDSTONES Outcrop studies undertaken on the Grassy Member and show that laterally continuous flooding surface shales overlying parasequence boundaries do not have simple updip terminations. Instead, they may pass updip into a zone of discontinuous shales (discontinuous inter-sandstone shales) along the parasequence boundary. Further updip, the flooding surface shales may pass into discontinuous coals or lagoonal shales. The presence of discontinuous inter-sandstone shales and correlative coals or lagoonal shales may have important implications for estimation of vertical connectivity between adjacent shoreface parasequences. Coal Plan-view of marine flooding surface shales Discontinuous Inter-sandstone shales and coal/ lagoonal shales Zone of Vertical Connectivity 100's-1000's of m s PARASEQUENCE BOUNDARY PARASEQUENCE 2 PARASEQUENCE 1 Cross-section Schematic diagram showing the updip transition from laterally continuous flooding surface shales into a zone of discontinuous flooding surface shales. These may pass updip into coals or lagoonal shales DISCONTINUOUS INTER-SANDSTONE SHALE LENGTHS W Panel 4 Panel 5 Panel 6 E GRASSY PARASEQUENCE 2 GRASSY PARASEQUENCE 1? Flooding Surface A GSB2 B C GPSB2/mfs GSB1/mfs 4.4 km GRASSY PARASEQUENCE 2 GRASSY PARASEQUENCE 1 Discontinuous flooding surface shales Flooding Surface Decreasing shale length: Increasing horizontal separation of shales Length (m) of Discontinuous Shales Mean Count 11 Minimum 4.97 Maximum Coef. Var 2.08 Range Median Horizontal Separation (m) of Discontinuous Shales Mean Count 10 Minimum 5.60 Maximum Coef.Var 1.10 Range Median The lengths of discontinuous inter-sandstone shales between and have been measured from photopanels taken along a dip-oriented section. Subsections of these photopanels are shown in the adjacent panel. These illustrate the updip change in the nature of shales overlying the parasequence boundary between GPS1 and GPS2. The 4 panels span approximately 6 km along a depositional dip section through the. Analysis of the length data collected from these panels shows: Discontinuous shales occur along the parasequence boundary between GPS1 and GPS2 for at least 4 km The lengths of discontinuous inter-sandstone shales decrease from distal to proximal locations (i.e. towards the palaeoshoreline) There is a corresponding increase in the horizontal separation of the inter-sandstone shales from distal to proximal locations along the parasequence boundary

INFLUENCE OF PARASEQUENCE STACKING PATTERN ON VERTICAL CONNECTIVITY BETWEEN ADJACENT SHOREFACE

vertical connectivity between adjacent parasequences.

Within the, the offset between GPS1 and GPS2 is approximately 12 km and the zone of potential

A 1 km In contrast, within the, the offset between SCPS3 and SCPS4 is only 7 km and the zone of

Although it is not yet possible to quantify the relationship between parasequence stacking

more strongly progradational parasequence stacking ns occur, there is likely to be a more

5 km 2 km B C Parasequence offset ~ 12 km Zone of Vertical Connectivity Sandstones?

4 INFLUENCE OF PARASEQUENCE STACKING PATTERN ON VERTICAL CONNECTIVITY BETWEEN ADJACENT SHOREFACE PARASEQUENCES This panel presents a comparison of the parasequence offset and zone of potential vertical connectivity between adjacent parasequences. Data have been collected from parasequences 1 and 2 of the and parasequences 3 and 4 of the. Within the, the offset between GPS1 and GPS2 is approximately 12 km and the zone of potential connectivity between these parasequences is at least 4 km. A 1 km In contrast, within the, the offset between SCPS3 and SCPS4 is only 7 km and the zone of potential connectivity between these parasequences is less than 1 km. Although it is not yet possible to quantify the relationship between parasequence stacking patterns (i.e. degree of parasequence offset) and vertical connectivity, this comparison suggests that, where more strongly progradational parasequence stacking patterns occur, there is likely to be a more laterally extensive zone of potential vertical connectivity between adjacent parasequences. 1.5 km 2 km B C Parasequence offset ~ 12 km Zone of Vertical Connectivity Sandstones? not observed 4 km + Discontinuous Inter-sandstone shales Plan view of parasequence boundary Zone of Vertical Connectivity Sandstones Spring Canyon Parasequence 3 (SCPS3) Spring Canyon Parasequence 4 (SCPS4) Parasequence offset ~ 7km Discontinuous shales and coal/lagoonal shale <1 km 0.25 km 2 km 1 km SCPS3 Spring Canyon Parasequence 3 (SCPS3) SCPS4 Spring Canyon Parasequence 4 (SCPS4) ~

SUMMARY AND CONCLUSIONS Discontinuous Inter-sandstone Shales Discontinuous inter-sandstone shales overlie marine flooding surfaces, updip of laterally continuous flooding surface shales The lengths

5 SUMMARY AND CONCLUSIONS Discontinuous Inter-sandstone Shales Discontinuous inter-sandstone shales overlie marine flooding surfaces, updip of laterally continuous flooding surface shales The lengths of inter-sandstone shales decrease from distal to proximal locations along a flooding surface (451 m to 4.97 m) The horizontal separation of inter-sandstone shales increases from distal to proximal locations (5.6 m to 292 m) The presence of discontinuous shales updip of laterally continuous flooding surface shales will influence the estimation of vertical connectivity between adjacent parasequences Comparison of Stacking Pattern and Vertical Connectivity The progradational offset between Grassy Parasequence 1 and Grassy Parasequence 2 is approximately 12 km. Between these two parasequences, the zone of potential vertical connectivity extends for at least 4 km. In contrast, between Spring Canyon Parasequences 3 and 4, the progradational offset is only approximately 7 km and the zone of potential vertical connectivity is less than 1 km. Comparison of progradational offset and vertical connectivity between the and Spring canyon Member suggests that in more strongly progradational parasequence stacking patterns, there is likely to be a more laterally extensive zone of vertical connectivity between parasequences. REFERENCES: Balsley, J. and Horne, J., 1980, Cretaceous wave-dominated delta systems: Book Cliffs, eastern central Utah: A field guide. Kamola, D. L. and Van Wagoner, J. C., 1995, Stratigraphy and facies architecture of parasequences with examples from the Spring Canyon Member, Blackhawk Formation, Utah, in Van Wagoner, J. C. and Bertram, G. T., eds., Sequence stratigraphy of foreland basin deposits: AAPG Memoir 64, p O'Byrne, C. J. and Flint, S., 1995, Sequence, parasequence and intraparasequence architecture of the, Blackhawk Formation, Book Cliffs, Utah, U.S.A., in Van Wagoner, J. C. and Bertram, G. T., eds., Sequence stratigraphy of foreland basin deposits: AAPG Memoir 64, p Swift, J. P., Hudelson, P. M., Brenner, R. L. and Thompson, P., 1987, Shelf construction in a foreland basin: Storm beds, shelf sandbodies, and shelf-slope depositional sequences in the Upper Cretaceous Mesaverde Group, Book Cliffs, Utah: Sedimentology, V. 34, p Taylor, D. R. and Lovell, R. W., 1995, High-frequency sequence stratigraphy and paleogeography of the Kenilworth Member, Blackhawk Formation, Book Cliffs, Utah, U.S.A., in Van Wagoner, J. C. and Bertram, G. T., eds., Sequence stratigraphy of foreland basin deposits: AAPG Memoir 64, p Van Wagoner, J. C., 1995, Sequence stratigraphy and marine to nonmarine facies architecture of foreland basin strata, Book Cliffs, Utah, U.S.A., in Van Wagoner, J. C. and Bertram, G. T., eds., Sequence stratigraphy of foreland basin deposits: AAPG Memoir 64, p Van Wagoner, J. C., Mitchum, R. M., Campion, K. M. and Rahmanian, V. D., 1990, Siliciclastic sequence stratigraphy in well logs, cores and outcrops: AAPG methods in exploration, V. 7, Pgs. 55. Young, R. G., 1957, Late Cretaceous cyclic deposits, Book Cliffs, eastern Utah: Bulletin of American Association of Petroleum Geologists, V. 41, p

OUTCROP! CHARACTERISATION! OF! TRANSGRESSIVE! SANDSTONE! RESERVOIRS:! QUANTITATIVE!COMPARISON!OF!OUTCROP!ANALOGUES!

OUTCROP! CHARACTERISATION! OF! TRANSGRESSIVE! SANDSTONE! RESERVOIRS:! QUANTITATIVE!COMPARISON!OF!OUTCROP!ANALOGUES! OUTCROP CHARACTERISATION OF TRANSGRESSIVE SANDSTONE RESERVOIRS: QUANTITATIVECOMPARISONOFOUTCROPANALOGUES OLIVER D. JORDAN 1, PETER J. SIXSMITH 2, GARY J. HAMPSON, SANJEEV GUPTA & HOWARDD.JOHNSON DepartmentofEarthScienceandEngineering,ImperialCollegeLondon,SouthKensington