Changes

{| class = wikitable

{| class = wikitable

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|+ Table 3. Reservoir, Fluid, and Rock Properties Used in the Model of the Ferron Sandstone Member Reservoir Analog (after Farrell and Abreu, 2006; Deveugle et al.<ref name=Dvgl2011 />)

|+ Table 3. Reservoir, Fluid, and Rock Properties Used in the Model of the Ferron Sandstone Member Reservoir Analog (after Farrell and Abreu;<ref>Farrell, M. E., and V. Abreu, 2006, [http://www.searchanddiscovery.com/-abstracts/pdf/2006/intl_perth/abstracts/ndx_farrell.pdf Reservoir connectivity in fluvial-deltaic depositional environments: South Timbalier 26 field study (abs.)]: AAPG International Conference and Exhibition, Perth, Australia, November 5–8, 2006.</ref> Deveugle et al.<ref name=Dvgl2011 />)

|-

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! Properties || Value || Units

! Properties || Value || Units

==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., 2003), 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., 1993).]]

===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 /> Patruno et al., 2015 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 (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 />

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 />; Patruno et al., 2015). 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) (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]]).

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 (Kantorowicz et al., 1987; Lien et al., 1992; Evensen et al., 1993). These are present within delta-front parasequences, which are seismically imaged as clinoform sets, and along their bounding flooding surfaces (Gibbons et al., 1993; Bakke et al., 1996; <ref name=Dryr2005 />; Holgate et al., 2014; Patruno et al., 2015). 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 (Lien et al., 1991; 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, 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.

===Model Construction===

===Model Construction===

The stratigraphic framework of the reservoir model is defined by flooding surfaces that bound seven parasequences. The bounding surfaces are offset by two postdepositional faults that are oriented northwest–southeast across the model volume. The faulted parasequence-bounding flooding surfaces were extracted from the existing reservoir model.<ref name=Dlb /> The faulted parasequence boundaries were used to construct the final Troll West sector model but, as a quality control step for applying the clinoform-modeling algorithm, these boundaries were adjusted so that they were horizontal. Each parasequence also contains a surface that represents the facies-association boundary between m sands below and c sands above; these surfaces were extracted from the model of Dilib et al.<ref name=Dlb /> and are laterally continuous across the clinoforms modeled here, because they were extracted from a model that omits clinoforms. Consequently, facies interfingering across clinoforms is not captured here, and this may further increase the impact of modeling clinoforms on flow.<ref name=Jckson2009 /> The facies-association boundary surfaces were adjusted to remove the effects of faulting in the same way as the flooding surfaces. Additionally, where facies associations pinch out, the facies association boundary surfaces are adjusted to coincide throughout the remainder of the model volume with the top parasequence bounding surface. This procedure created flooding surfaces and facies-association boundaries in the model that mimic their depositional geometries, which were used as a reference framework to validate that the clinoform geometries and distributions applied later using the faulted parasequence-bounding surfaces are consistent with geologic concepts.

The stratigraphic framework of the reservoir model is defined by flooding surfaces that bound seven parasequences. The bounding surfaces are offset by two postdepositional faults that are oriented northwest–southeast across the model volume. The faulted parasequence-bounding flooding surfaces were extracted from the existing reservoir model.<ref name=Dlb /> The faulted parasequence boundaries were used to construct the final Troll West sector model but, as a quality control step for applying the clinoform-modeling algorithm, these boundaries were adjusted so that they were horizontal. Each parasequence also contains a surface that represents the facies-association boundary between m sands below and c sands above; these surfaces were extracted from the model of Dilib et al.<ref name=Dlb /> and are laterally continuous across the clinoforms modeled here, because they were extracted from a model that omits clinoforms. Consequently, facies interfingering across clinoforms is not captured here, and this may further increase the impact of modeling clinoforms on flow.<ref name=Jckson2009 /> The facies-association boundary surfaces were adjusted to remove the effects of faulting in the same way as the flooding surfaces. Additionally, where facies associations pinch out, the facies association boundary surfaces are adjusted to coincide throughout the remainder of the model volume with the top parasequence bounding surface. This procedure created flooding surfaces and facies-association boundaries in the model that mimic their depositional geometries, which were used as a reference framework to validate that the clinoform geometries and distributions applied later using the faulted parasequence-bounding surfaces are consistent with geologic concepts.

Table 4 shows the parameters used in the clinoform-modeling algorithm. To honor the nearly linear plan-view geometry of clinoforms observed in seismic data (figures 3, 12 in Dreyer et al.<ref name=Dryr2005 />), a width for the top-clinoform ellipse (''t_s'') that is far greater than the depositional-dip extent of the bounding surfaces in the model area (3200 m [10,499 ft]) was defined; the top-clinoform ellipse length ''t_D'' is half of ''t_s'', to give a plan-view aspect ratio of 2 (cf. wave-dominated shoreface systems in Howell et al.<ref name=Hwll2008a />). Seismically resolved clinoform dip values of 1.5°–4°<ref name=Dryr2005 />; Patruno et al., 2015) were used in conjunction with the estimated parasequence thickness to calculate clinoform length (''L'') using simple trigonometry. As there are only a small number of seismically resolved clinoforms in a few paleogeographic locations and within a few stratigraphic levels to extract clinoform length, a normal distribution based on the extracted data was generated ([[:File:BLTN13190fig13.jpg|Figure 13A]]), and values were then drawn at random from this distribution to populate the model volume ([[:File:BLTN13190fig13.jpg|Figure 13A]]). Finally, the premodeling lengths were compared with the seismically resolved clinoforms<ref name=Dryr2005 /> to validate that the algorithm-generated lengths are reasonable. Similarly, the horizontal spacing of seismically resolved clinoforms (figures 3, 12 in Dreyer et al.<ref name=Dryr2005 />) was used to generate a normal distribution of values for clinoform spacing, S ([[:File:BLTN13190fig13.jpg|Figure 13B]]), and values were drawn at random from this distribution to populate the model volume ([[:File:BLTN13190fig13.jpg|Figure 13B]]). The resulting values of clinoform length and spacing are consistent with those observed at the outcrop for other wave-dominated shorelines (e.g., Hampson;<ref name=Hmpsn2000 /> Sech et al.<ref name=Sch09 />) ([[:File:BLTN13190fig13.jpg|Figure 13]]). A value of 2 was used for the exponent in the clinoform shape function (defined by ''P'' in equation 8), as this gives a good match to the seismically resolved clinoforms; and, furthermore, it was assumed that a similar geometry is shared by clinoforms in all parasequences in all locations throughout the model volume, consistent with observations of seismically resolved clinoforms over similar-size volumes (Patruno et al., 2015). Although, ''P'' has the same value as used in the Ferron Sandstone Member example, ''L'' values in the Troll Field sector model are larger ([[:File:BLTN13190fig13.jpg|Figure 13A]], Table 4) such that clinoform dip angles are shallower, consistent with the seismically resolved clinoforms.<ref name=Dryr2005 />; Patruno et al., 2015). As a first step, the insertion point of the first clinoform (''P_o'') was arbitrarily selected in the center of the proximal model boundary, and consistent west-northwest progradation of clinoforms<ref name=Dryr2005 />; Patruno et al., 2015) was used to define a ''θ'' of 320°. The facies-association boundary surfaces extracted from the model of Dilib et al.<ref name=Dlb /> were then used to create zones of m sands and c sands within each clinothem. The application of the clinoform-modeling algorithm yields a model containing 100 clinoforms. A visual quality control check was then performed to ensure that the clinoforms produced by the algorithm are consistent with the geologic concepts of the model (e.g., clinoform spacing, dip, length) in the absence of postdepositional faults.

Table 4 shows the parameters used in the clinoform-modeling algorithm. To honor the nearly linear plan-view geometry of clinoforms observed in seismic data (figures 3, 12 in Dreyer et al.<ref name=Dryr2005 />), a width for the top-clinoform ellipse (''t_s'') that is far greater than the depositional-dip extent of the bounding surfaces in the model area (3200 m [10,499 ft]) was defined; the top-clinoform ellipse length ''t_D'' is half of ''t_s'', to give a plan-view aspect ratio of 2 (cf. wave-dominated shoreface systems in Howell et al.<ref name=Hwll2008a />). Seismically resolved clinoform dip values of 1.5°–4°<ref name=Dryr2005 /><ref name=Ptrno /> were used in conjunction with the estimated parasequence thickness to calculate clinoform length (''L'') using simple trigonometry. As there are only a small number of seismically resolved clinoforms in a few paleogeographic locations and within a few stratigraphic levels to extract clinoform length, a normal distribution based on the extracted data was generated ([[:File:BLTN13190fig13.jpg|Figure 13A]]), and values were then drawn at random from this distribution to populate the model volume ([[:File:BLTN13190fig13.jpg|Figure 13A]]). Finally, the premodeling lengths were compared with the seismically resolved clinoforms<ref name=Dryr2005 /> to validate that the algorithm-generated lengths are reasonable. Similarly, the horizontal spacing of seismically resolved clinoforms (figures 3, 12 in Dreyer et al.<ref name=Dryr2005 />) was used to generate a normal distribution of values for clinoform spacing, S ([[:File:BLTN13190fig13.jpg|Figure 13B]]), and values were drawn at random from this distribution to populate the model volume ([[:File:BLTN13190fig13.jpg|Figure 13B]]). The resulting values of clinoform length and spacing are consistent with those observed at the outcrop for other wave-dominated shorelines (e.g., Hampson;<ref name=Hmpsn2000 /> Sech et al.<ref name=Sch09 />) ([[:File:BLTN13190fig13.jpg|Figure 13]]). A value of 2 was used for the exponent in the clinoform shape function (defined by ''P'' in equation 8), as this gives a good match to the seismically resolved clinoforms; and, furthermore, it was assumed that a similar geometry is shared by clinoforms in all parasequences in all locations throughout the model volume, consistent with observations of seismically resolved clinoforms over similar-size volumes.<ref name=Ptrno /> Although, ''P'' has the same value as used in the Ferron Sandstone Member example, ''L'' values in the Troll Field sector model are larger ([[:File:BLTN13190fig13.jpg|Figure 13A]], Table 4) such that clinoform dip angles are shallower, consistent with the seismically resolved clinoforms.<ref name=Dryr2005 /><ref name=Ptrno /> As a first step, the insertion point of the first clinoform (''P_o'') was arbitrarily selected in the center of the proximal model boundary, and consistent west-northwest progradation of clinoforms<ref name=Dryr2005 /><ref name=Ptrno /> was used to define a ''θ'' of 320°. The facies-association boundary surfaces extracted from the model of Dilib et al.<ref name=Dlb /> were then used to create zones of m sands and c sands within each clinothem. The application of the clinoform-modeling algorithm yields a model containing 100 clinoforms. A visual quality control check was then performed to ensure that the clinoforms produced by the algorithm are consistent with the geologic concepts of the model (e.g., clinoform spacing, dip, length) in the absence of postdepositional faults.

{| class = wikitable

{| class = wikitable

</gallery>

</gallery>

The clinoforms incorporated into the Troll sector model show similar geometries and spacing to those that are seismically resolved in the Sognefjord Formation.<ref name=Dryr2005 />; Patruno et al., 2015). The clinoforms are linear in plan view over the small (750 m [2461 ft]) depositional-strike extent of the model ([[:File:BLTN13190fig14.jpg|Figure 14B]]), consistent with the interpreted plan-view geometries of wave-dominated shoreface systems ([[:File:BLTN13190fig3.jpg|Figure 3A]]),<ref name=Hwll2008a /> consistently prograde west-northwestward (θ = 320°), as established through 3-D seismic data,<ref name=Dryr2005 /> Patruno et al., 2015), and have the concave-upward geometry observed in seismic dip sections through the Sognefjord Formation<ref name=Dryr2005 /> Patruno et al., 2015) (Figures 14A, 15B). In depositional strike cross section, the algorithm produces near-horizontal clinoform geometries, consistent with seismically resolved clinoforms<ref name=Dryr2005 /> Patruno et al., 2015) ([[:File:BLTN13190fig15.jpg|Figure 15C]]). The stochastic component of the clinoform-modeling algorithm distributes clinoforms with cross-sectional geometries and spacings (Figures 14A, 15B) that are consistent with outcrop studies of wave-dominated deltas<ref name=Hmpsn2000>Hampson, G. J., 2000, Discontinuity surfaces, clinoforms and facies architecture in a wave-dominated, shoreface-shelf parasequence: Journal of Sedimentary Research, v. 70, no. 2, p. 325–340, doi: 10.1306/2DC40914-0E47-11D7-8643000102C1865D.</ref><ref name=Sch09 /> ([[:File:BLTN13190fig13.jpg|Figure 13]]) and honor the sparse subsurface data. In contrast to the Ferron Sandstone Member example, the Troll West sector model does not contain subtle clinoform geometries, such as onlap and downlap of younger clinoforms on to older clinoforms ([[:File:BLTN13190fig14.jpg|Figures 14A]], [[:File:BLTN13190fig15.jpg|15B]]). Such features are below the resolution of the seismic data used to extract the parameters that were used in the algorithm. The clinoforms are also faulted in the same way as the parasequence-bounding flooding surfaces (cf. [[:File:BLTN13190fig2.jpg|Figures 2A]], [[:File:BLTN13190fig15.jpg|15C]]).

The clinoforms incorporated into the Troll sector model show similar geometries and spacing to those that are seismically resolved in the Sognefjord Formation.<ref name=Dryr2005 /><ref name=Ptrno /> The clinoforms are linear in plan view over the small (750 m [2461 ft]) depositional-strike extent of the model ([[:File:BLTN13190fig14.jpg|Figure 14B]]), consistent with the interpreted plan-view geometries of wave-dominated shoreface systems ([[:File:BLTN13190fig3.jpg|Figure 3A]]),<ref name=Hwll2008a /> consistently prograde west-northwestward (θ = 320°), as established through 3-D seismic data,<ref name=Dryr2005 /><ref name=Ptrno /> and have the concave-upward geometry observed in seismic dip sections through the Sognefjord Formation<ref name=Dryr2005 /><ref name=Ptrno /> (Figures 14A, 15B). In depositional strike cross section, the algorithm produces near-horizontal clinoform geometries, consistent with seismically resolved clinoforms<ref name=Dryr2005 /><ref name=Ptrno /> ([[:File:BLTN13190fig15.jpg|Figure 15C]]). The stochastic component of the clinoform-modeling algorithm distributes clinoforms with cross-sectional geometries and spacings (Figures 14A, 15B) that are consistent with outcrop studies of wave-dominated deltas<ref name=Hmpsn2000>Hampson, G. J., 2000, Discontinuity surfaces, clinoforms and facies architecture in a wave-dominated, shoreface-shelf parasequence: Journal of Sedimentary Research, v. 70, no. 2, p. 325–340, doi: 10.1306/2DC40914-0E47-11D7-8643000102C1865D.</ref><ref name=Sch09 /> ([[:File:BLTN13190fig13.jpg|Figure 13]]) and honor the sparse subsurface data. In contrast to the Ferron Sandstone Member example, the Troll West sector model does not contain subtle clinoform geometries, such as onlap and downlap of younger clinoforms on to older clinoforms ([[:File:BLTN13190fig14.jpg|Figures 14A]], [[:File:BLTN13190fig15.jpg|15B]]). Such features are below the resolution of the seismic data used to extract the parameters that were used in the algorithm. The clinoforms are also faulted in the same way as the parasequence-bounding flooding surfaces (cf. [[:File:BLTN13190fig2.jpg|Figures 2A]], [[:File:BLTN13190fig15.jpg|15C]]).

===Production Strategy===

===Production Strategy===

# 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.

# 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.

# Google Earth, 2013, accessed January 14, 2013, http://www.google.co.uk/intl/en_uk/earth/index.html.

# Google Earth, 2013, accessed January 14, 2013, http://www.google.co.uk/intl/en_uk/earth/index.html.

#  

#  

# 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.

# 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.

#  

#  

# Joshi, S. D., 1987, A review of horizontal well and drain hole technology: SPE Paper 16868, 17 p.

# Joshi, S. D., 1987, A review of horizontal well and drain hole technology: SPE Paper 16868, 17 p.

#  

#  

# 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.

# 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.

# Norwegian Petroleum Directorate, 2013, Positive resource accounts for the Norwegian shelf in 2011, accessed January 14, 2013, http://www.npd.no/en/Topics/Resource-accounts-and--analysis/Temaartikler/Resource-accounts/2011/.

# Norwegian Petroleum Directorate, 2013, Positive resource accounts for the Norwegian shelf in 2011, accessed January 14, 2013, http://www.npd.no/en/Topics/Resource-accounts-and--analysis/Temaartikler/Resource-accounts/2011/.

#  

#  

# Ryer, T. A., and P. B. Anderson, 2004, Facies of the Ferron Sandstone, east-central Utah, inT. 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: AAPG Studies in Geology 50, p. 59–78.

# Ryer, T. A., and P. B. Anderson, 2004, Facies of the Ferron Sandstone, east-central Utah, inT. 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: AAPG Studies in Geology 50, p. 59–78.

# 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.

# 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.