scholarly journals The role of pre-existing jointing on damage zone evolution and faulting style of thin competent layers in mechanically stratified sequences: a case study from the Limestone Coal Formation at Spireslack Surface Coal Mine

2020 ◽  
Author(s):  
Billy J. Andrews ◽  
Zoe K. Shipton ◽  
Richard Lord ◽  
Lucy McKay
Keyword(s):  
Fluid Flow ◽  
Internal Structure ◽  
Coal Mine ◽  
Damage Zone ◽  
Fault Rock ◽  
Surface Coal Mine ◽  
Fracture Mapping ◽  
Fault Growth

Abstract. Fault and fracture networks play an important role in sub-surface fluid flow and can act to enhance, retard or compartmentalise groundwater flow. In multi-layered sequences, the internal structure and growth of faults is not only controlled by fault throw, but also the mechanical properties of lithologies cut by the fault. This paper uses geological fieldwork, combined with fault and fracture mapping, to investigate the internal structure and fault development of the mechanically stratified Limestone Coal Formation and surrounding lithologies exposed at Spireslack Surface Coal Mine. We find that the development of fault rock, and complexity of a fault zone is dependent on: a) whether a fault is self-juxtaposed or cuts multiple lithologies; b) the presence and behaviour of shale, which can lead to significant bed-rotation and the formation of fault-core lenses; and c) whether pre-existing weakness (e.g. joints) are present at the time of faulting. Pre-existing joint networks in the McDonald Limestone, and cleats in the McDonald Coal, influenced both fault growth and fluid flow within these lithologies.

COLLABORATECOM SPECIAL ISSUE ANALYZING DISTRIBUTED WHITEBOARD INTERACTIONS

2012 ◽  
Vol 21 (03) ◽  
pp. 199-220
Author(s):  
LUTZ GERICKE ◽  
RAJA GUMIENNY ◽  
CHRISTOPH MEINEL
Keyword(s):  
Internal Structure ◽  
Team Work ◽  
Special Issue ◽  
Distributed Work ◽  
Team Members ◽  
Work Settings ◽  
Simplified Analysis ◽  
Digital Whiteboard

We present the digital whiteboard system Tele-Board, which automatically captures all interactions made on the all-digital whiteboard and thus offers possibilities for a fast interpretation of usage characteristics. Analyzing team work at whiteboards is a time-consuming and error-prone process if manual interpretation techniques are applied. In a case study, we demonstrate how to conduct and analyze whiteboard experiments with the help of our system. The study investigates the role of video compared to an audio-only connection for distributed work settings. With the simplified analysis of communication data, we can prove that the video teams were more active than the audio teams and the distribution of whiteboard interaction between team members was more balanced. This way, an automatic analysis can not only support manual observations and codings, but also give insights that cannot be achieved with other systems. Beyond the overall view on one sessions focusing on key figures, it is also possible to find out more about the internal structure of a session.

How Chosen Seismic Fault Picking Strategy Influences Subsequent Fault Analyses: A Case Study from the Horda Platform, with Implications for CO2 storage

2021 ◽  
Author(s):  
Emma Michie ◽  
Mark Mulrooney ◽  
Alvar Braathen
Keyword(s):  
Fluid Flow ◽  
Co2 Storage ◽  
Fault Analysis ◽  
Surface Generation ◽  
Storage Site ◽  
Seismic Line ◽  
Fault Stability ◽  
Line Spacing ◽  
Fault Growth

<p>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.  Seismic line spacing chosen by the interpreter when picking fault segments, as well as the chosen surface generation algorithm used, will dictate how detailed or smoothed the surface is, and hence will impact any further interpretation such as fault seal, fault stability and fault growth analyses.</p><p>This contribution is a case study showing how picking strategies influence analysis of a bounding fault in terms of CO<sub>2</sub> storage assessment.  This example utilizes data from the Smeaheia potential storage site within the Horda Platform, 20 km East of Troll East.  This is a fault bound prospect, known as the Alpha prospect, and hence the bounding fault is required to have a high seal potential and low chance of reactivation upon CO<sub>2</sub> injection.</p><p>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 simply adds further complexities, associated with sensitivities by the individual interpreter.  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 highly irregular 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 / stability as well as for fault growth models.</p><p>Uncertainty associated with the chosen seismic interpretation methodology will follow through to subsequent fault seal analysis, such as analysis of whether in situ stresses, combined with increased pore pressure through CO<sub>2</sub> injection, will act to reactivate the faults, leading to up-fault fluid flow / seep.  We have shown that changing picking strategies significantly alters the interpreted stability of the fault, where picking with an increased line spacing has shown to increase the overall fault stability, and picking using every line leads to the interpretation of a critically stressed fault.  Alternatively, it is important to note that differences in picking strategy show little influence on the overall predicted fault membrane seal (i.e. shale gouge ratio) of the fault, used when interpreting the fault seal capacity for a fault bound CO<sub>2</sub> storage site.</p>

scholarly journals 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 ◽  
Author(s):  
Emma A. H. Michie ◽  
Mark J. Mulrooney ◽  
Alvar Braathen
Keyword(s):  
Fluid Flow ◽  
Seismic Data ◽  
Growth Models ◽  
Fault Analysis ◽  
Surface Generation ◽  
Co2 Injection ◽  
Line Spacing ◽  
Fault Growth ◽  
Fault Interpretation

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.

scholarly journals 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

Solid Earth ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 1259-1286
Author(s):  
Emma A. H. Michie ◽  
Mark J. Mulrooney ◽  
Alvar Braathen
Keyword(s):  
Fluid Flow ◽  
Seismic Data ◽  
Growth Models ◽  
Fault Analysis ◽  
Surface Generation ◽  
Co2 Injection ◽  
Line Spacing ◽  
Fault Growth ◽  
Fault Interpretation

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.

Permeability of carbonate fault rocks: a case study from Malta

2019 ◽  
Vol 26 (3) ◽  
pp. 418-433 ◽  
Author(s):  
Andy P. Cooke ◽  
Quentin J. Fisher ◽  
Emma A. H. Michie ◽  
Graham Yielding
Keyword(s):  
Fluid Flow ◽  
Host Rock ◽  
Damage Zone ◽  
Fault Zones ◽  
High Porosity ◽  
Rock Permeability ◽  
Fault Rock ◽  
Fault Rocks ◽  
Diagenetic Alteration ◽  
Hydraulic Behaviour

The inherent heterogeneity of carbonate rocks suggests that carbonate-hosted fault zones are also likely to be heterogeneous. Coupled with a lack of host–fault petrophysical relationships, this makes the hydraulic behaviour of carbonate-hosted fault zones difficult to predict. Here we investigate the link between host rock and fault rock porosity, permeability and texture, by presenting data from series of host rock, damage zone and fault rock samples from normally faulted, shallowly buried limestones from Malta. Core plug X-ray tomography indicates that texturally heterogeneous host rocks lead to greater variability in the porosity and permeability of fault rocks. Fault rocks derived from moderate- to high-porosity (>20%) formations experience permeability reductions of up to six orders of magnitude relative to the host; >30% of these fault rocks could act as baffles or barriers to fluid flow over production timescales. Fault rocks derived from lower-porosity (<20%) algal packstones have permeabilities that are lower than their hosts by up to three orders of magnitude, which is unlikely to impact fluid flow on production timescales. The variability of fault rock permeability is controlled by a number of factors, including the initial host rock texture and porosity, the magnitude of strain localization, and the extent of post-deformation diagenetic alteration. Fault displacement has no obvious control over fault rock permeability. The results enable better predictions of fault rock permeability in similar lithotypes and tectonic regimes. This may enable predictions of across-fault fluid flow potential when combined with data on fault zone architecture.

Analysis of the internal structure of a carbonate damage zone: Implications for the mechanisms of fault breccia formation and fluid flow

2010 ◽  
Vol 32 (9) ◽  
pp. 1349-1362 ◽  
Author(s):  
Stefan Hausegger ◽  
Walter Kurz ◽  
Robert Rabitsch ◽  
Eva Kiechl ◽  
Franz-Josef Brosch
Keyword(s):  
Fluid Flow ◽  
Internal Structure ◽  
Damage Zone ◽  
Fault Breccia
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