Changes

===Plan-View Clinoform Geometry===

===Plan-View Clinoform Geometry===

<gallery mode=packed heights=400px widths=400px>

<gallery mode=packed heights=400px widths=400px>

BLTN13190fig3.jpg|{{figure number|3}}Generalized, first-order approximations of the plan-view geometry of clinoforms in different depositional environments: (A) Nayarit Coast, Mexico, representative of a wave-dominated strandplain (image modified after Google Earth and DigitalGlobe, 2013); (B) Nile Delta, Egypt, representative of a wave-dominated delta (image modified after Google Earth, 2013); and (C) Wax Lake Delta, Louisiana, representative of a fluvial-dominated delta (image modified after Google Earth and TerraMetrics, 2013). Solid white lines represent a first-order approximation of the shoreline at the clinoform top, whereas the dashed white lines represent first-order approximations of the likely maximum extent of the clinoform surface and its downlap termination on the underlying sea floor.

BLTN13190fig3.jpg|{{figure number|3}}Generalized, first-order approximations of the plan-view geometry of clinoforms in different depositional environments: (A) Nayarit Coast, Mexico, representative of a wave-dominated strandplain (image modified after Google Earth and DigitalGlobe<ref>[http://www.google.co.uk/intl/en_uk/earth/index.html. Google Earth and DigitalGlobe], 2013, accessed January 14, 2013.</ref>); (B) Nile Delta, Egypt, representative of a wave-dominated delta (image modified after Google Earth<ref>[http://www.google.co.uk/intl/en_uk/earth/index.html Google Earth], 2013, accessed January 14, 2013.</ref>); and (C) Wax Lake Delta, Louisiana, representative of a fluvial-dominated delta (image modified after Google Earth and TerraMetrics<ref>[http://www.google.co.uk/intl/en_uk/earth/index.html Google Earth and TerraMetrics], 2013, accessed January 14, 2013.</ref>). Solid white lines represent a first-order approximation of the shoreline at the clinoform top, whereas the dashed white lines represent first-order approximations of the likely maximum extent of the clinoform surface and its downlap termination on the underlying sea floor.

BLTN13190fig4.jpg|{{figure number|4}}(A) A user specifies the length of the top (solid line) and base (dashed line) ellipses in depositional dip and strike directions (t_s, t_D, b_s, b_D; Table 1) relative to the clinoform origin. The surface representing the clinoform is created in the volume between the top and base ellipses. (B) At a point on the clinoform, the radius relative to the clinoform origin (black arrow, ''r_c(x, y)'', the radius of the base ellipse (black arrow, ''r_max(x, y)'' and the radius of the top ellipse (black arrow, ''r_min(x, y)'' are calculated. (C) Plan view of four adjacent clinoforms. The user specifies the overall progradation direction of the clinoforms relative to north, as well as the coordinates of the initial insertion point ''P<sub>O<sub>''. (D) Conceptual depositional-dip-oriented cross-section view of clinoforms. Clinoform spacing, ''S'', is defined as the distance between the top truncation points of two adjacent clinoforms. Clinoform length, ''L'', is defined as the distance between the top and base truncations by the user-specified bounding surfaces along a single clinoform.

BLTN13190fig4.jpg|{{figure number|4}}(A) A user specifies the length of the top (solid line) and base (dashed line) ellipses in depositional dip and strike directions (t_s, t_D, b_s, b_D; Table 1) relative to the clinoform origin. The surface representing the clinoform is created in the volume between the top and base ellipses. (B) At a point on the clinoform, the radius relative to the clinoform origin (black arrow, ''r_c(x, y)'', the radius of the base ellipse (black arrow, ''r_max(x, y)'' and the radius of the top ellipse (black arrow, ''r_min(x, y)'' are calculated. (C) Plan view of four adjacent clinoforms. The user specifies the overall progradation direction of the clinoforms relative to north, as well as the coordinates of the initial insertion point ''P<sub>O<sub>''. (D) Conceptual depositional-dip-oriented cross-section view of clinoforms. Clinoform spacing, ''S'', is defined as the distance between the top truncation points of two adjacent clinoforms. Clinoform length, ''L'', is defined as the distance between the top and base truncations by the user-specified bounding surfaces along a single clinoform.

</gallery>

</gallery>

Construction and fluid-flow simulation of models based on outcrop analogs is an established method for investigating geologic controls on subsurface reservoir performance (e.g., Ciammetti et al.;<ref>Ciammetti, G., P. S. Ringrose, T. R. Good, J. M. L. Lewis, and K. S. Sorbie, 1995, Waterflood recovery and fluid flow upscaling in a shallow marine and fluvial sandstone sequence: SPE Paper 30783, 14 p.</ref> White and Barton;<ref name=WB1999>White, C. D., and M. D. Barton, 1999, Translating outcrop data to flow models, with applications to the Ferron Sandstone: SPE Reservoir Evaluation and Engineering, v. 2, no. 4, p. 341–350, doi: 10.2118/57482-PA.</ref> White et al.;<ref>White, C. D., B. J. Willis, S. P. Dutton, J. P. Bhattacharya, and K. Narayanan, 2004, [http://archives.datapages.com/data/specpubs/memoir80/CHAPTER7/CHAPTER7.HTM Sedimentology, statistics, and flow behaviour for a tide-influenced deltaic sandstone, Frontier Formation, Wyoming, United States], in G. M. Grammer, P. M. Harris, and G. P. Eberli, eds., Integration of outcrop and modern analogs in reservoir modeling: [http://store.aapg.org/detail.aspx?id=658 AAPG Memoir 80], p. 129–152.</ref> Jackson et al.;<ref name=Jckson2009 /> Sech et al.;<ref name=Sch09 /> Enge and Howell<ref name=EH2010 />). Here, the clinoform-modeling algorithm is used to build a reservoir model utilizing a high-resolution outcrop data set from the Ferron Sandstone Member, Utah, at a scale that is comparable to the interwell spacing (750 × 3000 m [2461 × 9843 ft] areally) in a typical hydrocarbon reservoir and captures several tens of clinoforms and their associated heterogeneities. Previously, Forster et al. <ref name=Frstr2004 /> constructed 2-D flow-simulation models of the same outcrop analog via data-intensive, deterministic mapping of clinoforms and facies boundaries in cliff-face exposures. In contrast, our aim is to verify that the clinoform-modeling algorithm can produce realistic 3-D stratigraphic architectures that mimic rich outcrop data sets when conditioned to sparse input data that are typical in the subsurface. The scale of the model fills the gap between detailed but sparse 2-D core and well-log data and low-resolution but extensive 3-D seismic data.

Construction and fluid-flow simulation of models based on outcrop analogs is an established method for investigating geologic controls on subsurface reservoir performance (e.g., Ciammetti et al.;<ref>Ciammetti, G., P. S. Ringrose, T. R. Good, J. M. L. Lewis, and K. S. Sorbie, 1995, Waterflood recovery and fluid flow upscaling in a shallow marine and fluvial sandstone sequence: SPE Paper 30783, 14 p.</ref> White and Barton;<ref name=WB1999>White, C. D., and M. D. Barton, 1999, Translating outcrop data to flow models, with applications to the Ferron Sandstone: SPE Reservoir Evaluation and Engineering, v. 2, no. 4, p. 341–350, doi: 10.2118/57482-PA.</ref> White et al.;<ref>White, C. D., B. J. Willis, S. P. Dutton, J. P. Bhattacharya, and K. Narayanan, 2004, [http://archives.datapages.com/data/specpubs/memoir80/CHAPTER7/CHAPTER7.HTM Sedimentology, statistics, and flow behaviour for a tide-influenced deltaic sandstone, Frontier Formation, Wyoming, United States], in G. M. Grammer, P. M. Harris, and G. P. Eberli, eds., Integration of outcrop and modern analogs in reservoir modeling: [http://store.aapg.org/detail.aspx?id=658 AAPG Memoir 80], p. 129–152.</ref> Jackson et al.;<ref name=Jckson2009 /> Sech et al.;<ref name=Sch09 /> Enge and Howell<ref name=EH2010 />). Here, the clinoform-modeling algorithm is used to build a reservoir model utilizing a high-resolution outcrop data set from the Ferron Sandstone Member, Utah, at a scale that is comparable to the interwell spacing (750 × 3000 m [2461 × 9843 ft] areally) in a typical hydrocarbon reservoir and captures several tens of clinoforms and their associated heterogeneities. Previously, Forster et al. <ref name=Frstr2004 /> constructed 2-D flow-simulation models of the same outcrop analog via data-intensive, deterministic mapping of clinoforms and facies boundaries in cliff-face exposures. In contrast, our aim is to verify that the clinoform-modeling algorithm can produce realistic 3-D stratigraphic architectures that mimic rich outcrop data sets when conditioned to sparse input data that are typical in the subsurface. The scale of the model fills the gap between detailed but sparse 2-D core and well-log data and low-resolution but extensive 3-D seismic data.

The Ferron Sandstone Member of the Mancos Shale is located in east-central Utah. The unit was deposited during the Late Cretaceous (Turonian–Coniacian) on the western margin of the Western Interior Seaway and, in the study area, records the progradation of the Last Chance delta system from southwest (paleolandward) to northeast (paleoseaward)<ref name=cttr /> ([[:File:BLTN13190fig5.jpg|Figure 5A]]). These deltaic deposits form a basinward-thinning wedge that passes eastward into the offshore deposits of the Mancos Shale. The wedge contains either seven<ref>Ryer, T. A., 1991, Stratigraphy, facies and depositional history of the Ferron Sandstone in the Canyon of Muddy Creek, east-central Utah, inT. C. Chidsey, Jr., ed., Geology of east-central Utah: Utah Geological Association Publication 19, p. 45–54.</ref><ref name=Grdnr>Gardner, M. H., 1993, Sequence stratigraphy and facies architecture of the Upper Cretaceous Ferron Sandstone Member of the Mancos Shale, east-central Utah: Ph.D. dissertation, Colorado School of Mines, Golden, Colorado, 528 p.</ref><ref>Barton, M. D., E. S. Angle, and N. Tyler, 2004, [http://archives.datapages.com/data/specpubs/study50/sg50ch07/sg50ch07.htm Stratigraphic architecture of fluvial-deltaic sandstones from the Ferron Sandstone outcrop, east-central Utah], in T. C. Chidsey, Jr., R. D. Adams, and T. H. Morris, eds., Regional to wellbore analog for fluvial-deltaic reservoir modeling: The Ferron Sandstone of Utah: [http://store.aapg.org/detail.aspx?id=655 AAPG Studies in Geology 50], p. 193–210.</ref> or eight sandstone tongues,<ref name=AndrsnRyr2004 /><ref name=GvdB2004 /> such that one tongue is equivalent to a parasequence set of Deveugle et al.<ref name=Dvgl2011 /> ([[:File:BLTN13190fig5.jpg|Figure 5B]]). A single delta-lobe deposit within the lowermost sandstone tongue is the focus of the study (bedset Kf-1-Iv[a] of Anderson et al.;<ref name=Andrsn2004>Anderson, P. B., T. C. Chidsey, Jr., T. A. Ryer, R. D. Adams, and K. McClure, 2004, [http://archives.datapages.com/data/specpubs/study50/sg50ch13/sg50ch13.htm Geological framework, facies paleogeography, and reservoir analogs of the Ferron Sandstone in the Ivie Creek area, east-central Utah], in T. C. Chidsey, Jr., R. D. Adams, and T. H. Morris, eds., Regional to wellbore analog for fluvial-deltaic reservoir modeling: The Ferron Sandstone of Utah: [http://store.aapg.org/detail.aspx?id=655 AAPG Studies in Geology 50], p. 331–356.</ref> parasequence 1h of Garrison and Van den Bergh;<ref name=GvdB2004 /> parasequence 1.6 of Deveugle et al.<ref name=Dvgl2011 />) ([[:File:BLTN13190fig5.jpg|Figure 5C, D]]). The delta-lobe deposit is fluvial dominated with low-to-moderate wave influence<ref name=Grdnr /><ref name=GvdB2004 /> Ryer and Anderson, 2004) and contains numerous, well-documented clinoforms in the exposures of the Ivie Creek amphitheater<ref>Anderson, P. B., T. C. Chidsey, Jr., K. McClure, A. Mattson, and S. H. Snelgrove, 2002, Ferron Sandstone stratigraphic cross-sections, Ivie Creek area, Emery County, Utah: Utah Geological Survey, Open File Report 390, CD-ROM.</ref><ref>Anderson, P. B., K. McClure, T. C. Chidsey, Jr., T. A. Ryer, T. H. Morris, J. A. Dewey, Jr., and R. D. Adams, 2003, Interpreted regional photomosaics and cross sections, Cretaceous Ferron Sandstone, east-central Utah: Utah Geological Survey, Open File Report 412, CD-ROM.</ref><ref name=Andrsn2004 /><ref name=Frstr2004 /><ref name=EH2010 /> ([[:File:BLTN13190fig5.jpg|Figure 5D]]). Clinoform-related bedding geometries and facies distributions imply that clinoforms mapped by previous workers, and used as input data for the models presented below ([[:File:BLTN13190fig6.jpg|Figure 6A]], after Forster et al. <ref name=Frstr2004 />), bound clinothems equivalent to mouth bars (sensu Bhattacharya<ref name=Bhttchry2006 />). Subtle, apparently cyclic variations in clinoform spacing and dip angle probably define mouth-bar assemblages (sensu Bhattacharya;<ref name=Bhttchry2006 /> “bedsets” sensu Enge et al.<ref name=Eng2010>Enge, H. D., J. A. Howell, and S. Buckley, 2010, The geometry and internal architecture of stream mouth bars in the Panther Tongue and the Ferron Sandstone Members, Utah, U.S.A.: Journal of Sedimentary Research, v. 80, no. 11, p. 1018–1031, doi: 10.2110/jsr.2010.088.</ref>). Smaller-scale lithologic variation at the scale of individual beds occurs between the mapped clinoforms and records incremental growth of a mouth bar because of varying water and sediment discharge through the feeder distributary channel. Deveugle et al.<ref name=Dvgl2011 /> used a high-resolution outcrop data set to build a reservoir-scale (7200 × 3800 × 50 m [23622 × 12467 × 164 ft]), surface-based model of the lower two tongues (parasequence sets) of the Ferron Sandstone Member. Clinoforms were not represented in the delta-lobe deposits (cf. parasequences) of the Deveugle et al.<ref name=Dvgl2011 /> model, and their surface-based model is used here as the context in which the clinoform-modeling algorithm should be applied.

The Ferron Sandstone Member of the Mancos Shale is located in east-central Utah. The unit was deposited during the Late Cretaceous (Turonian–Coniacian) on the western margin of the Western Interior Seaway and, in the study area, records the progradation of the Last Chance delta system from southwest (paleolandward) to northeast (paleoseaward)<ref name=cttr /> ([[:File:BLTN13190fig5.jpg|Figure 5A]]). These deltaic deposits form a basinward-thinning wedge that passes eastward into the offshore deposits of the Mancos Shale. The wedge contains either seven<ref>Ryer, T. A., 1991, Stratigraphy, facies and depositional history of the Ferron Sandstone in the Canyon of Muddy Creek, east-central Utah, inT. C. Chidsey, Jr., ed., Geology of east-central Utah: Utah Geological Association Publication 19, p. 45–54.</ref><ref name=Grdnr>Gardner, M. H., 1993, Sequence stratigraphy and facies architecture of the Upper Cretaceous Ferron Sandstone Member of the Mancos Shale, east-central Utah: Ph.D. dissertation, Colorado School of Mines, Golden, Colorado, 528 p.</ref><ref>Barton, M. D., E. S. Angle, and N. Tyler, 2004, [http://archives.datapages.com/data/specpubs/study50/sg50ch07/sg50ch07.htm Stratigraphic architecture of fluvial-deltaic sandstones from the Ferron Sandstone outcrop, east-central Utah], in T. C. Chidsey, Jr., R. D. Adams, and T. H. Morris, eds., Regional to wellbore analog for fluvial-deltaic reservoir modeling: The Ferron Sandstone of Utah: [http://store.aapg.org/detail.aspx?id=655 AAPG Studies in Geology 50], p. 193–210.</ref> or eight sandstone tongues,<ref name=AndrsnRyr2004 /><ref name=GvdB2004 /> such that one tongue is equivalent to a parasequence set of Deveugle et al.<ref name=Dvgl2011 /> ([[:File:BLTN13190fig5.jpg|Figure 5B]]). A single delta-lobe deposit within the lowermost sandstone tongue is the focus of the study (bedset Kf-1-Iv[a] of Anderson et al.;<ref name=Andrsn2004>Anderson, P. B., T. C. Chidsey, Jr., T. A. Ryer, R. D. Adams, and K. McClure, 2004, [http://archives.datapages.com/data/specpubs/study50/sg50ch13/sg50ch13.htm Geological framework, facies paleogeography, and reservoir analogs of the Ferron Sandstone in the Ivie Creek area, east-central Utah], in T. C. Chidsey, Jr., R. D. Adams, and T. H. Morris, eds., Regional to wellbore analog for fluvial-deltaic reservoir modeling: The Ferron Sandstone of Utah: [http://store.aapg.org/detail.aspx?id=655 AAPG Studies in Geology 50], p. 331–356.</ref> parasequence 1h of Garrison and Van den Bergh;<ref name=GvdB2004 /> parasequence 1.6 of Deveugle et al.<ref name=Dvgl2011 />) ([[:File:BLTN13190fig5.jpg|Figure 5C, D]]). The delta-lobe deposit is fluvial dominated with low-to-moderate wave influence<ref name=Grdnr /><ref name=GvdB2004 /><ref>Ryer, T. A., and P. B. Anderson, 2004, [http://archives.datapages.com/data/specpubs/study50/sg50ch03/sg50ch03.htm Facies of the Ferron Sandstone, east-central Utah], in T. C. Chidsey, Jr., R. D. Adams, and T. H. Morris, eds., Regional to wellbore analog for fluvial-deltaic reservoir modeling: The Ferron Sandstone of Utah: [http://store.aapg.org/detail.aspx?id=655 AAPG Studies in Geology 50], p. 59–78.</ref> and contains numerous, well-documented clinoforms in the exposures of the Ivie Creek amphitheater<ref>Anderson, P. B., T. C. Chidsey, Jr., K. McClure, A. Mattson, and S. H. Snelgrove, 2002, Ferron Sandstone stratigraphic cross-sections, Ivie Creek area, Emery County, Utah: Utah Geological Survey, Open File Report 390, CD-ROM.</ref><ref>Anderson, P. B., K. McClure, T. C. Chidsey, Jr., T. A. Ryer, T. H. Morris, J. A. Dewey, Jr., and R. D. Adams, 2003, Interpreted regional photomosaics and cross sections, Cretaceous Ferron Sandstone, east-central Utah: Utah Geological Survey, Open File Report 412, CD-ROM.</ref><ref name=Andrsn2004 /><ref name=Frstr2004 /><ref name=EH2010 /> ([[:File:BLTN13190fig5.jpg|Figure 5D]]). Clinoform-related bedding geometries and facies distributions imply that clinoforms mapped by previous workers, and used as input data for the models presented below ([[:File:BLTN13190fig6.jpg|Figure 6A]], after Forster et al. <ref name=Frstr2004 />), bound clinothems equivalent to mouth bars (sensu Bhattacharya<ref name=Bhttchry2006 />). Subtle, apparently cyclic variations in clinoform spacing and dip angle probably define mouth-bar assemblages (sensu Bhattacharya;<ref name=Bhttchry2006 /> “bedsets” sensu Enge et al.<ref name=Eng2010>Enge, H. D., J. A. Howell, and S. Buckley, 2010, The geometry and internal architecture of stream mouth bars in the Panther Tongue and the Ferron Sandstone Members, Utah, U.S.A.: Journal of Sedimentary Research, v. 80, no. 11, p. 1018–1031, doi: 10.2110/jsr.2010.088.</ref>). Smaller-scale lithologic variation at the scale of individual beds occurs between the mapped clinoforms and records incremental growth of a mouth bar because of varying water and sediment discharge through the feeder distributary channel. Deveugle et al.<ref name=Dvgl2011 /> used a high-resolution outcrop data set to build a reservoir-scale (7200 × 3800 × 50 m [23622 × 12467 × 164 ft]), surface-based model of the lower two tongues (parasequence sets) of the Ferron Sandstone Member. Clinoforms were not represented in the delta-lobe deposits (cf. parasequences) of the Deveugle et al.<ref name=Dvgl2011 /> model, and their surface-based model is used here as the context in which the clinoform-modeling algorithm should be applied.

===Model Construction===

===Model Construction===

==Example 2: Troll west reservoir sector model==

==Example 2: Troll west reservoir sector model==

[[File:BLTN13190fig12.jpg|thumb|400px|{{figure number|12}}(A) Paleogeographic reconstruction of gross depositional environments in the central and northern North Sea during the early-to-mid Kimmeridgian (modified from Fraser et al.<ref>Fraser, S. I., A. M. Robinson, H. D. Johnson, J. R. Underhill, D. G. A. Kadolsky, R. Connell, P. Johanessen, and R. Ravnås, 2003, Upper Jurassic, inD. Evans, C. Graham, A. Armour, and P. Bathurst, eds., The millennium atlas: Petroleum geology of the central and northern North Sea: London, The Geological Society, p. 158–189.</ref>), marked by retreat and drowning of the Troll delta system (6-series of the Sognefjord Formation; Dreyer et al.<ref name=Dryr2005>Dreyer, T., M. Whitaker, J. Dexter, H. Flesche, and E. Larsen, 2005, From spit system to tide-dominated delta: Integrated reservoir model of the Upper Jurassic Sognefjord Formation on the Troll West field, inA. G. Doré, and B. A. Vining, eds., Petroleum geology: From mature basins to new frontiers—Proceedings of the 6th Petroleum Geology Conference: Petroleum Geology Conference Series 6: London, Geological Society, p. 423–448.</ref>. (B) Simplified outline of the Troll Field, highlighting major blocks bounded by normal faults that post-date deposition of the Sognefjord Formation. The location of the modeled area and a stratigraphic cross section across Troll West ([[:File:BLTN13190fig12.jpg|Figure 12C]]) are shown. (C) Schematic cross section through the Troll delta system of the Sognefjord Formation in Troll West, from west (paleoseaward) to east (paleolandward). Major shallow-marine tongues (labeled 1-series to 6-series, using the nomenclature of Dreyer et al.<ref name=Dryr2005 />) and their component parasequences are shown (after Gibbons et al., 1993).]]

[[File:BLTN13190fig12.jpg|thumb|400px|{{figure number|12}}(A) Paleogeographic reconstruction of gross depositional environments in the central and northern North Sea during the early-to-mid Kimmeridgian (modified from Fraser et al.<ref>Fraser, S. I., A. M. Robinson, H. D. Johnson, J. R. Underhill, D. G. A. Kadolsky, R. Connell, P. Johanessen, and R. Ravnås, 2003, Upper Jurassic, inD. Evans, C. Graham, A. Armour, and P. Bathurst, eds., The millennium atlas: Petroleum geology of the central and northern North Sea: London, The Geological Society, p. 158–189.</ref>), marked by retreat and drowning of the Troll delta system (6-series of the Sognefjord Formation; Dreyer et al.<ref name=Dryr2005>Dreyer, T., M. Whitaker, J. Dexter, H. Flesche, and E. Larsen, 2005, From spit system to tide-dominated delta: Integrated reservoir model of the Upper Jurassic Sognefjord Formation on the Troll West field, inA. G. Doré, and B. A. Vining, eds., Petroleum geology: From mature basins to new frontiers—Proceedings of the 6th Petroleum Geology Conference: Petroleum Geology Conference Series 6: London, Geological Society, p. 423–448.</ref>. (B) Simplified outline of the Troll Field, highlighting major blocks bounded by normal faults that post-date deposition of the Sognefjord Formation. The location of the modeled area and a stratigraphic cross section across Troll West ([[:File:BLTN13190fig12.jpg|Figure 12C]]) are shown. (C) Schematic cross section through the Troll delta system of the Sognefjord Formation in Troll West, from west (paleoseaward) to east (paleolandward). Major shallow-marine tongues (labeled 1-series to 6-series, using the nomenclature of Dreyer et al.<ref name=Dryr2005 />) and their component parasequences are shown (after Gibbons et al.<ref name=Gbbns>Gibbons, K., T. Hellem, A. Kjemperud, S. D. Nio, and K. Vebenstad, 1993, Sequence architecture, facies development and carbonate-cemented horizons in the Troll Field reservoir, offshore Norway, inM. Ashton, ed., Advances in reservoir geology: Geological Society, London, Special Publication 69, p. 1–31.</ref>).]]

===Geological Setting===

===Geological Setting===

The clinoform-modeling algorithm is now applied to construct a model of the Upper Jurassic Sognefjord Formation reservoir in a fault-bounded sector of the Troll Field, offshore Norway ([[:File:BLTN13190fig12.jpg|Figure 12A, B]]). The Troll Field is a supergiant gas field that initially hosted about 40% of the total gas reserves on the Norwegian continental shelf and still contains ca. 1000 x 10⁹ S m³ (35 tcf) of gas (Norwegian Petroleum Directorate, 2013). The western and eastern parts of the Troll Field accumulation occur in different structures, Troll West and Troll East. The Sognefjord Formation is interpreted to record deposition in a mixed fluvial-, tide-, and wave-influenced delta system.<ref name=Dryr2005 /><ref name=Ptrno>Patruno, S., G. J. Hampson, C. A.-L. Jackson, and T. Dreyer, 2015, Clinoform geometry, geomorphology, facies character and stratigraphic architecture of a sand-rich subaqueous delta: Jurassic Sognefjord Formation, offshore Norway: Sedimentology, v. 62, no. 1, p. 350–388, doi: 10.1111/sed.12153.</ref> The formation is up to 170 m (558 ft) thick in the Troll Field and consists of five, vertically stacked regressive–transgressive successions bounded by major flooding surfaces (informally referred to as the 2-, 3-, 4-, 5- and 6-series in the reservoir; [[:File:BLTN13190fig12.jpg|Figure 12C]]).<ref name=Dryr2005 /> Each regressive–transgressive succession exhibits internal stratigraphic variability across the lateral extent of the reservoir, such that it can be interpreted as a sequence with constituent systems tracts and parasequences.<ref name=Dryr2005 /> The reservoir volume to be modeled contains seven, vertically stacked parasequences. The lower parasequences were deposited by regression of wave-dominated delta-fronts, whereas the upper parasequences comprise more tide-influenced delta-front deposits.<ref name=Dryr2005 />

The clinoform-modeling algorithm is now applied to construct a model of the Upper Jurassic Sognefjord Formation reservoir in a fault-bounded sector of the Troll Field, offshore Norway ([[:File:BLTN13190fig12.jpg|Figure 12A, B]]). The Troll Field is a supergiant gas field that initially hosted about 40% of the total gas reserves on the Norwegian continental shelf and still contains ca. 1000 x 10⁹ S m³ (35 tcf) of gas.<ref>Norwegian Petroleum Directorate, 2013, [http://www.npd.no/en/Topics/Resource-accounts-and--analysis/Temaartikler/Resource-accounts/2011/ Positive resource accounts for the Norwegian shelf in 2011].</ref> The western and eastern parts of the Troll Field accumulation occur in different structures, Troll West and Troll East. The Sognefjord Formation is interpreted to record deposition in a mixed fluvial-, tide-, and wave-influenced delta system.<ref name=Dryr2005 /><ref name=Ptrno>Patruno, S., G. J. Hampson, C. A.-L. Jackson, and T. Dreyer, 2015, Clinoform geometry, geomorphology, facies character and stratigraphic architecture of a sand-rich subaqueous delta: Jurassic Sognefjord Formation, offshore Norway: Sedimentology, v. 62, no. 1, p. 350–388, doi: 10.1111/sed.12153.</ref> The formation is up to 170 m (558 ft) thick in the Troll Field and consists of five, vertically stacked regressive–transgressive successions bounded by major flooding surfaces (informally referred to as the 2-, 3-, 4-, 5- and 6-series in the reservoir; [[:File:BLTN13190fig12.jpg|Figure 12C]]).<ref name=Dryr2005 /> Each regressive–transgressive succession exhibits internal stratigraphic variability across the lateral extent of the reservoir, such that it can be interpreted as a sequence with constituent systems tracts and parasequences.<ref name=Dryr2005 /> The reservoir volume to be modeled contains seven, vertically stacked parasequences. The lower parasequences were deposited by regression of wave-dominated delta-fronts, whereas the upper parasequences comprise more tide-influenced delta-front deposits.<ref name=Dryr2005 />

Reservoir zones in the Troll West accumulation are defined by alternating layers of fine-grained, micaceous sandstone and coarse-grained sandstone (informally referred to as m sands and c sands, respectively). The coarse-grained sandstones have higher porosity and permeability (hundreds to thousands of millidarcys) than the fine-grained, micaceous sandstones (tens to hundreds of millidarcys) (Gibbons et al., 1993; <ref name=Dryr2005 />). Each couplet of fine-grained, micaceous sandstone and overlying coarse-grained sandstones corresponds to the lower and upper part of a single delta-front parasequence.<ref name=Dryr2005 /> The 3-D seismic data image laterally extensive (up to 30 km [19 mi] along depositional strike), near-linear, north-northeast–south-southwest-trending clinoforms that dip west-northwestward at 1.5°–4°.<ref name=Dryr2005 /><ref name=Ptrno /> The structure of the Troll West reservoir is defined by two rotated fault blocks that formed after reservoir deposition, and the reservoir is further segmented by smaller postdepositional faults that trend west-northwest–east-southeast to north-northwest–south-southeast<ref name=Dryr2005 /> ([[:File:BLTN13190fig12.jpg|Figure 12B]]).

Reservoir zones in the Troll West accumulation are defined by alternating layers of fine-grained, micaceous sandstone and coarse-grained sandstone (informally referred to as m sands and c sands, respectively). The coarse-grained sandstones have higher porosity and permeability (hundreds to thousands of millidarcys) than the fine-grained, micaceous sandstones (tens to hundreds of millidarcys).<ref name=Gbbns /><ref name=Dryr2005 /> Each couplet of fine-grained, micaceous sandstone and overlying coarse-grained sandstones corresponds to the lower and upper part of a single delta-front parasequence.<ref name=Dryr2005 /> The 3-D seismic data image laterally extensive (up to 30 km [19 mi] along depositional strike), near-linear, north-northeast–south-southwest-trending clinoforms that dip west-northwestward at 1.5°–4°.<ref name=Dryr2005 /><ref name=Ptrno /> The structure of the Troll West reservoir is defined by two rotated fault blocks that formed after reservoir deposition, and the reservoir is further segmented by smaller postdepositional faults that trend west-northwest–east-southeast to north-northwest–south-southeast<ref name=Dryr2005 /> ([[:File:BLTN13190fig12.jpg|Figure 12B]]).

Troll West contains a thin oil column (11–26 m [36–85 ft]) that is exploited through the use of horizontal wells,<ref name=Dryr2005 /> the productivity of which is sensitive to the ratio of vertical-to-horizontal permeability (cf. Joshi, 1987). This ratio is predicted to be influenced by the calcite-cemented concretionary beds that are abundant in the Sognefjord Formation.<ref>Kantorowicz, J. D., I. D. Bryant, and J. M. Dawans, 1987, Controls on the geometry and distribution of carbonate cements in Jurassic sandstones: Bridport Sands, southern England and Viking Group, Troll Field, Norway, inJ. D. Marshall, ed., Diagenesis of sedimentary sequences: Geological Society, London, Special Publication 36, p. 103–118.</ref><ref>Lien, S. C., H. H. Haldorsen, and M. Manner, 1992, Horizontal wells: Still appealing in formations with discontinuous vertical permeability barriers?: Journal of Petroleum Technology, v. 44, no. 12, p. 1364–1370, doi: 10.2118/20962-PA.</ref><ref>Evensen, J. E., M. Skaug, and P. Goodyear, 1993, Production geological challenges of characterizing the thin oil rims in the Troll Field: OTC Paper 7172, Proceedings from the Offshore Technology Conference, Houston, Texas, USA, May 3–6, 1993, 12 p.</ref> These are present within delta-front parasequences, which are seismically imaged as clinoform sets, and along their bounding flooding surfaces. (Gibbons et al., 1993; <ref>Bakke, N. E., E. T. Ertresvåg, A. Næss, A. C. MacDonald, and L. M. Fält, 1996, Application of seismic data and sequence stratigraphy for constraining a stochastic model of calcite cementation: SPE Paper 35487, 13 p.</ref><ref name=Dryr2005 /><ref>Holgate, N. E., G. J. Hampson, C. A.-L. Jackson, and S. A. Petersen, 2014, [http://archives.datapages.com/data/bulletns/2014/12dec/BLTN13152/BLTN13152.html Constraining uncertainty in interpretation of seismically imaged clinoforms in deltaic reservoirs, Troll Field, Norwegian North Sea: Insights from forward seismic models of outcrop analogs]: AAPG Bulletin, v. 98, no. 12, p. 2629–2663, doi: 10.1306/05281413152.</ref><ref name=Ptrno /> The Jurassic Bridport Sand Formation, a close sedimentologic analog present onshore United Kingdom, contains similarly abundant calcite-cemented concretionary beds. These are observed at the outcrop to be laterally extensive (>80% areal coverage) along bedding planes and in a producing subsurface reservoir; their presence is marked by breaks in pressure and fluid saturation within seismically imaged clinoform sets.<ref>Hampson, G. J., J. E. Morris, and H. D. Johnson, 2014, Synthesis of time-stratigraphic relationships and their impact on hydrocarbon reservoir distribution and performance, Bridport Sand Formation, Wessex Basin, UK, inD. G. Smith, R. J. Bailey, P. M. Burgess, and A. J. Fraser, eds., Strata and time: Probing the gaps in our understanding: Geological Society, London, Special Publication 404, first published online on March 19, 2014, doi: 10.1144/SP404.2.</ref> (Morris et al., 2006) Thus it appears probable that permeability barriers and baffles in the form of calcite-cemented concretionary layers occur along clinoforms in the Troll Field reservoir and could influence drainage patterns and recovery from the thin oil zone (Gibbons et al., 1993); this may have been recognized previously and shown to impact on well test interpretations.<ref>Lien, S. C., K. Seines, S. O. Havig, and T. Kydland, 1991, The first long-term horizontal-well test in the Troll thin oil zone: Journal of Petroleum Technology, v. 43, no. 8, p. 914–973, doi: 10.2118/20715-PA.</ref>; Haug, 1992). However, to date, the heterogeneity associated with clinoforms has not been explicitly included in reservoir or flow-simulation models of the Sognefjord Formation in the Troll Field. Dilib et al.<ref name=Dlb>Dilib, F. A., M. D. Jackson, A. Mojaddam Zadeh, R. Aasheim, K. Årland, A. J. Gyllensten, and S. M. Erlandsen, 2015, Closed-loop feedback control in intelligent wells: Application to a heterogeneous, thin oil-rim reservoir in the North Sea: SPE Reservoir Evaluation and Engineering, v. 18, no. 1, 15 p., doi: 10.2118/159550-PA.</ref> created a sector model of the Sognefjord Formation (dimensions: 3200 × 750 × 150 m [10,499 × 2461 × 492 ft]) to investigate production optimization using intelligent wells for a range of uncertainty in geologic parameters and their model, extracted and refined from the existing full field geological model, was used here as the context in which to apply the clinoform-modeling algorithm.

Troll West contains a thin oil column (11–26 m [36–85 ft]) that is exploited through the use of horizontal wells,<ref name=Dryr2005 /> the productivity of which is sensitive to the ratio of vertical-to-horizontal permeability (cf. Joshi<ref>Joshi, S. D., 1987, A review of horizontal well and drain hole technology: SPE Paper 16868, 17 p.</ref>). This ratio is predicted to be influenced by the calcite-cemented concretionary beds that are abundant in the Sognefjord Formation.<ref>Kantorowicz, J. D., I. D. Bryant, and J. M. Dawans, 1987, Controls on the geometry and distribution of carbonate cements in Jurassic sandstones: Bridport Sands, southern England and Viking Group, Troll Field, Norway, inJ. D. Marshall, ed., Diagenesis of sedimentary sequences: Geological Society, London, Special Publication 36, p. 103–118.</ref><ref>Lien, S. C., H. H. Haldorsen, and M. Manner, 1992, Horizontal wells: Still appealing in formations with discontinuous vertical permeability barriers?: Journal of Petroleum Technology, v. 44, no. 12, p. 1364–1370, doi: 10.2118/20962-PA.</ref><ref>Evensen, J. E., M. Skaug, and P. Goodyear, 1993, Production geological challenges of characterizing the thin oil rims in the Troll Field: OTC Paper 7172, Proceedings from the Offshore Technology Conference, Houston, Texas, USA, May 3–6, 1993, 12 p.</ref> These are present within delta-front parasequences, which are seismically imaged as clinoform sets, and along their bounding flooding surfaces.<ref name=Gbbns /><ref>Bakke, N. E., E. T. Ertresvåg, A. Næss, A. C. MacDonald, and L. M. Fält, 1996, Application of seismic data and sequence stratigraphy for constraining a stochastic model of calcite cementation: SPE Paper 35487, 13 p.</ref><ref name=Dryr2005 /><ref>Holgate, N. E., G. J. Hampson, C. A.-L. Jackson, and S. A. Petersen, 2014, [http://archives.datapages.com/data/bulletns/2014/12dec/BLTN13152/BLTN13152.html Constraining uncertainty in interpretation of seismically imaged clinoforms in deltaic reservoirs, Troll Field, Norwegian North Sea: Insights from forward seismic models of outcrop analogs]: AAPG Bulletin, v. 98, no. 12, p. 2629–2663, doi: 10.1306/05281413152.</ref><ref name=Ptrno /> The Jurassic Bridport Sand Formation, a close sedimentologic analog present onshore United Kingdom, contains similarly abundant calcite-cemented concretionary beds. These are observed at the outcrop to be laterally extensive (>80% areal coverage) along bedding planes and in a producing subsurface reservoir; their presence is marked by breaks in pressure and fluid saturation within seismically imaged clinoform sets.<ref>Hampson, G. J., J. E. Morris, and H. D. Johnson, 2014, Synthesis of time-stratigraphic relationships and their impact on hydrocarbon reservoir distribution and performance, Bridport Sand Formation, Wessex Basin, UK, inD. G. Smith, R. J. Bailey, P. M. Burgess, and A. J. Fraser, eds., Strata and time: Probing the gaps in our understanding: Geological Society, London, Special Publication 404, first published online on March 19, 2014, doi: 10.1144/SP404.2.</ref><ref>Morris, J. E., G. J. Hampson, and H. D. Johnson, 2006, A sequence stratigraphic model for an intensely bioturbated shallow-marine sandstone: The Bridport Sand Formation, Wessex basin, UK: Sedimentology, v. 53, no. 6, p. 1229–1263, doi: 10.1111/j.1365-3091.2006.00811.x.</ref> Thus it appears probable that permeability barriers and baffles in the form of calcite-cemented concretionary layers occur along clinoforms in the Troll Field reservoir and could influence drainage patterns and recovery from the thin oil zone;<ref name=Gbbns /> this may have been recognized previously and shown to impact on well test interpretations.<ref>Lien, S. C., K. Seines, S. O. Havig, and T. Kydland, 1991, The first long-term horizontal-well test in the Troll thin oil zone: Journal of Petroleum Technology, v. 43, no. 8, p. 914–973, doi: 10.2118/20715-PA.</ref><ref>Haug, B. T., 1992, The second long-term horizontal well test in Troll: Successful production from a 13-in. oil column with the well partly completed in the water zone: SPE Paper 24943, 10 p.</ref> However, to date, the heterogeneity associated with clinoforms has not been explicitly included in reservoir or flow-simulation models of the Sognefjord Formation in the Troll Field. Dilib et al.<ref name=Dlb>Dilib, F. A., M. D. Jackson, A. Mojaddam Zadeh, R. Aasheim, K. Årland, A. J. Gyllensten, and S. M. Erlandsen, 2015, Closed-loop feedback control in intelligent wells: Application to a heterogeneous, thin oil-rim reservoir in the North Sea: SPE Reservoir Evaluation and Engineering, v. 18, no. 1, 15 p., doi: 10.2118/159550-PA.</ref> created a sector model of the Sognefjord Formation (dimensions: 3200 × 750 × 150 m [10,499 × 2461 × 492 ft]) to investigate production optimization using intelligent wells for a range of uncertainty in geologic parameters and their model, extracted and refined from the existing full field geological model, was used here as the context in which to apply the clinoform-modeling algorithm.

===Model Construction===

===Model Construction===

|}

|}

After this validation, the clinoform-modeling algorithm was applied with the same parameters (Table 4) but using the faulted parasequence-bounding flooding surfaces and the faulted facies-association boundary surfaces. The resulting surface-based model contains clinoforms with geometries and distributions that reflect present-day reservoir structure, measures approximately 3200 × 750 × 150 m (10,499 × 2461 × 492 ft), and contains 215 surfaces: the 8 top and base parasequence bounding surfaces, 100 clinoform surfaces, and 107 facies-association-boundary surfaces between clinoform pairs. A hybrid gridding method is used, because previous work shows that this approach better captures the movement of gas and water in the vicinity of a horizontal production well located in a thin oil rim (Vinje et al., 2011). The areal grid resolution of the model is fixed (50 × 25 m [164 × 82 ft]), but the vertical resolution varies. In the gas cap and aquifer, the vertical layering is stratigraphic, conforming to the flooding surfaces that bound the parasequences and with a single grid layer representing each facies association zone. In an interval of the reservoir that contains the oil column, from 3 m (10 ft) above the gas–oil contact (GOC) to 3 m (10 ft) below the oil–water contact (OWC), the grid is horizontal and regular, with finer layering (0.25–2 m [0.82–7 ft]) parallel to the initial GOC and OWC.<ref name=Dlb /> Very fine grid resolution is required to capture the geometry of clinoforms in this regular, orthogonal part of the grid. For the model to be suitable for flow simulation, it is not possible to have this level of grid resolution everywhere in the model. Petrophysical properties were assigned by facies association in a similar manner to the model of the Ferron Sandstone Member reservoir analog. Clinoform-related heterogeneity was incorporated in flow-simulation models by using transmissibility multipliers along clinoform surfaces, where a trend was used to enforce greater continuity and extent of heterogeneity in the m sands that lie above the lower part of each clinoform. A different approach was used to model the clinoform-controlled heterogeneity than for the Ferron Sandstone Member model, because part of the grid is horizontal and regular. Transmissibility multipliers representing the heterogeneity along clinoforms are placed in the cells adjacent to the clinoform surface in the orthogonal part of grid around the oil rim. As the orthogonal grid is very fine, this approach honors the geometry of the clinoform surfaces.

After this validation, the clinoform-modeling algorithm was applied with the same parameters (Table 4) but using the faulted parasequence-bounding flooding surfaces and the faulted facies-association boundary surfaces. The resulting surface-based model contains clinoforms with geometries and distributions that reflect present-day reservoir structure, measures approximately 3200 × 750 × 150 m (10,499 × 2461 × 492 ft), and contains 215 surfaces: the 8 top and base parasequence bounding surfaces, 100 clinoform surfaces, and 107 facies-association-boundary surfaces between clinoform pairs. A hybrid gridding method is used, because previous work shows that this approach better captures the movement of gas and water in the vicinity of a horizontal production well located in a thin oil rim.<ref>Vinje, J., R. Nybø, and G. Grinestaff, 2011, A new simulation grid type is demonstrated for the giant Troll oil and gas field: SPE Paper 148023, 14 p.</ref> The areal grid resolution of the model is fixed (50 × 25 m [164 × 82 ft]), but the vertical resolution varies. In the gas cap and aquifer, the vertical layering is stratigraphic, conforming to the flooding surfaces that bound the parasequences and with a single grid layer representing each facies association zone. In an interval of the reservoir that contains the oil column, from 3 m (10 ft) above the gas–oil contact (GOC) to 3 m (10 ft) below the oil–water contact (OWC), the grid is horizontal and regular, with finer layering (0.25–2 m [0.82–7 ft]) parallel to the initial GOC and OWC.<ref name=Dlb /> Very fine grid resolution is required to capture the geometry of clinoforms in this regular, orthogonal part of the grid. For the model to be suitable for flow simulation, it is not possible to have this level of grid resolution everywhere in the model. Petrophysical properties were assigned by facies association in a similar manner to the model of the Ferron Sandstone Member reservoir analog. Clinoform-related heterogeneity was incorporated in flow-simulation models by using transmissibility multipliers along clinoform surfaces, where a trend was used to enforce greater continuity and extent of heterogeneity in the m sands that lie above the lower part of each clinoform. A different approach was used to model the clinoform-controlled heterogeneity than for the Ferron Sandstone Member model, because part of the grid is horizontal and regular. Transmissibility multipliers representing the heterogeneity along clinoforms are placed in the cells adjacent to the clinoform surface in the orthogonal part of grid around the oil rim. As the orthogonal grid is very fine, this approach honors the geometry of the clinoform surfaces.

===Geologic Model Results===

===Geologic Model Results===

==References==

==References==

{{reflist}}

{{reflist}}