Shetland Group: stratigraphic subdivision and regional correlation in the Norwegian North Sea

Nybakken, S.; Bäckstrøm, Sven A.

doi:10.1007/978-94-009-1149-9_20

Cited by 4 publications

(5 citation statements)

References 6 publications

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“…It occurs at approximately 1200 m depth at the Alpha prospect and has been recorded as having a permeability of 440–4000 mD and a porosity of 30–39% (Mondol et al, 2018; Ringrose et al, 2017; Statoil, 2016). It has a top and lateral seal from deep marine, organic‐rich mudstones of the Draupne Formation, along with deep water marl, carbonates and shaley units in the Cromer Knoll and Shetland Groups above the Base Cretaceous Unconformity (Gradstein & Waters, 2016; Isaksen & Ledje, 2001; Justwan & Dahl, 2005; Nybakken & Bäckstrøm, 1989).…”

Section: Study Areamentioning

confidence: 99%

How displacement analysis may aid fault risking strategies for CO₂ storage

Michie

Braathen

2023

Basin Research

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Developing an accurate understanding of the ways in which faults have grown within a particular region and stratigraphy can aid risk management for CO2 storage sites. Areas of fault interaction lead to differences in the stress field, resulting in an increased strain, which is often accommodated by a high intensity of deformation bands and/or fracturing, dependent on host rock properties. These structures alter the permeability surrounding faults. Hence, detecting areas of interaction of structures throughout the fault growth history allows the identification of locations where high risk may occur in terms of the hydraulic properties of a fault zone. The Vette Fault Zone (VFZ), bounding the Alpha prospect within the potential CO2 Smeaheia storage site, Northern Horda Platform, is shown to have grown from a minimum of seven fault segments. By utilising a comparison with the adjacent Tusse Fault Zone (TFZ), we can identify potential areas of high risk, where fluids may have the ability to flow across or along the VFZ. The high seal strength of the TFZ holding back a large gas column is likely to be created by shale juxtaposition and smearing with cataclastic processes. The same could be assumed for the VFZ, associated with similar tectonics and displaced stratigraphy. However, rather than membrane breaching causing fluids to flow across the fault, potential areas of high risk have been identified at locations of relict breached relay zones, where the initial displacement of the intersecting faults and area of overlap was high. These areas appear to correspond with the location of hydrocarbon contact depth (spill point) along the TFZ. Using the same assumptions for the VFZ, we can observe one potential area of high risk, which lies within the area of suggested CO2 accumulation.

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Section: Study Areamentioning

confidence: 99%

How displacement analysis may aid fault risking strategies for CO₂ storage

Michie

Braathen

2023

Basin Research

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“…These units represent stacked saline aquifers at this location. They are composed of coastal to shallow marine deposits dominated by sandstones with finer-grained interlayers (Dreyer et al, 2005;Holgate et al, 2013;Patruno et al, 2015). Of these, the Sognefjord Formation at the top of the stacked aquifer offers the best properties.…”

Section: Study Areamentioning

confidence: 99%

“…It occurs at approximately 1200 m depth in the Alpha prospect and has a permeability of 440-4000 mD and a porosity of 30 %-39 % (Statoil, 2016;Ringrose et al, 2017;Mondol et al, 2018). The Sognefjord Formation is capped by deep marine, organic-rich mudstones of the Draupne Formation, as well as deep water marls, carbonates and shaley units in the Cromer Knoll and Shetland groups above the base Cretaceous unconformity (Nybakken and Bäckstrøm, 1989;Isaksen and Ledjie, 2001;Kyrkjebø et al, 2004;Justwan and Dahl, 2005;Gradstein and Waters, 2016;Fig. 4).…”

Section: Study Areamentioning

confidence: 99%

Fault interpretation uncertainties using seismic data, and the effects on fault seal analysis: a case study from the Horda Platform, with implications for CO<sub>2</sub> storage

2021

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Abstract. Significant uncertainties occur through varying methodologies when interpreting faults using seismic data. These uncertainties are carried through to the interpretation of how faults may act as baffles or barriers, or increase fluid flow. How fault segments are picked when interpreting structures, i.e. which seismic line orientation, bin spacing and line spacing are specified, as well as what surface generation algorithm is used, will dictate how rugose the surface is and hence will impact any further interpretation such as fault seal or fault growth models. We can observe that an optimum spacing for fault interpretation for this case study is set at approximately 100 m, both for accuracy of analysis but also for considering time invested. It appears that any additional detail through interpretation with a line spacing of ≤ 50 m adds complexity associated with sensitivities by the individual interpreter. Further, the locations of all seismic-scale fault segmentation identified on throw–distance plots using the finest line spacing are also observed when 100 m line spacing is used. Hence, interpreting at a finer scale may not necessarily improve the subsurface model and any related analysis but in fact lead to the production of very rough surfaces, which impacts any further fault analysis. Interpreting on spacing greater than 100 m often leads to overly smoothed fault surfaces that miss details that could be crucial, both for fault seal as well as for fault growth models. Uncertainty in seismic interpretation methodology will follow through to fault seal analysis, specifically for analysis of whether in situ stresses combined with increased pressure through CO2 injection will act to reactivate the faults, leading to up-fault fluid flow. We have shown that changing picking strategies alter the interpreted stability of the fault, where picking with an increased line spacing has shown to increase the overall fault stability. Picking strategy has shown to have a minor, although potentially crucial, impact on the predicted shale gouge ratio.

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“…It occurs at approximately 1200 m depth at the Alpha prospect, and has a permeability of 440-4000 mD and a porosity of 30-39% (Statoil, 2016;Ringrose, 2017;Mondol et al, 2018). The Sognefjord Formation is capped by deep marine, organic-rich mudstones of the Draupne Formation, as well as deep water marls, carbonates and shaley units in the Cromer Knoll and Shetland Groups above the Base Cretaceous Unconformity (Nybakken and Bäckstrøm, 1989;Isaksen and Ledjie, 2001;Kyrkjebø et al, 2004;Justwan and Dahl, 2005;Gradstein and Waters, 2016; Figure 3).…”

Section: Study Areamentioning

confidence: 99%

Fault Interpretation Uncertainties using Seismic Data, and the Effects on Fault Seal Analysis: A Case Study from the Horda Platform, with Implications for CO<sub>2</sub> storage

Michie¹,

Mulrooney²,

Braathen³

2021

Preprint

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Abstract. Significant uncertainties occur through varying methodologies when interpreting faults using seismic data. These uncertainties are carried through to the interpretation of how faults may act as baffles/barriers or increase fluid flow. How fault segments are picked when interpreting structures, i.e. what seismic line spacing is specified, as well as what surface generation algorithm is used, will dictate how detailed the surface is, and hence will impact any further interpretation such as fault seal or fault growth models. We can observe that an optimum spacing for fault interpretation for this case study is set at approximately 100 m. It appears that any additional detail through interpretation with a line spacing of ≤ 50 m adds complexity associated with sensitivities by the individual interpreter. Further, the location of all fault segmentation identified on Throw-Distance plots using the finest line spacing are also observed when 100 m line spacing is used. Hence, interpreting at a finer scale may not necessarily improve the subsurface model and any related analysis, but in fact lead to the production of very rough surfaces, which impacts any further fault analysis. Interpreting on spacing greater than 100 m often leads to overly smoothed fault surfaces that miss details that could be crucial, both for fault seal as well as for fault growth models. Uncertainty in seismic interpretation methodology will follow through to fault seal analysis, specifically for analysis of whether in situ stresses combined with increased pressure through CO2 injection will act to reactivate the faults, leading to up-fault fluid flow/seep. We have shown that changing picking strategies alter the interpreted stability of the fault, where picking with an increased line spacing has shown to increase the overall fault stability. Picking strategy has shown to have minor, although potentially crucial, impact on the predicted Shale Gouge Ratio.

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Shetland Group: stratigraphic subdivision and regional correlation in the Norwegian North Sea

Cited by 4 publications

References 6 publications

How displacement analysis may aid fault risking strategies for CO₂ storage

How displacement analysis may aid fault risking strategies for CO₂ storage

Fault interpretation uncertainties using seismic data, and the effects on fault seal analysis: a case study from the Horda Platform, with implications for CO<sub>2</sub> storage

Fault Interpretation Uncertainties using Seismic Data, and the Effects on Fault Seal Analysis: A Case Study from the Horda Platform, with Implications for CO<sub>2</sub> storage

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Shetland Group: stratigraphic subdivision and regional correlation in the Norwegian North Sea

Cited by 4 publications

References 6 publications

How displacement analysis may aid fault risking strategies for CO2 storage

How displacement analysis may aid fault risking strategies for CO2 storage

Fault interpretation uncertainties using seismic data, and the effects on fault seal analysis: a case study from the Horda Platform, with implications for CO&lt;sub&gt;2&lt;/sub&gt; storage

Fault Interpretation Uncertainties using Seismic Data, and the Effects on Fault Seal Analysis: A Case Study from the Horda Platform, with Implications for CO&lt;sub&gt;2&lt;/sub&gt; storage

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Product

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How displacement analysis may aid fault risking strategies for CO₂ storage

How displacement analysis may aid fault risking strategies for CO₂ storage

Fault interpretation uncertainties using seismic data, and the effects on fault seal analysis: a case study from the Horda Platform, with implications for CO<sub>2</sub> storage

Fault Interpretation Uncertainties using Seismic Data, and the Effects on Fault Seal Analysis: A Case Study from the Horda Platform, with Implications for CO<sub>2</sub> storage