Torvela T.,University of Aberdeen |
Bond C.E.,University of Aberdeen |
Bond C.E.,Midland Valley Exploration Ltd.
Journal of Structural Geology | Year: 2011
Theoretical models are often used to aid interpretation of geological data. For fold-thrust belts, structural and kinematic models have existed for over a century. While greatly contributing to our understanding of thrust systems, the usage of models can result in oversimplification and false kinematic interpretations. This paper investigates how and if experts use structural models in the interpretation of a seismic image from a deepwater fold-thrust belt. The results show that in the majority of cases experts produced interpretations that were compliant with key features in existing structural models. Those interpretations that were less compliant to existing models, better accounted for features present in natural and experimental analogues. This has implications for the general applicability of structural models in interpretation. © 2010 Elsevier Ltd.
Bond C.E.,Midland Valley Exploration Ltd. |
Lunn R.J.,University of Strathclyde |
Shipton Z.K.,University of Strathclyde |
Lunn A.D.,University of Oxford
Geology | Year: 2012
Interpretation of uncertain data is the basis for understanding many Earth processes; in particular, uncertain data underpin much of the world's hydrocarbon exploration and future carbon minimization strategies (CO2 storage and radioactive waste disposal). It is therefore crucial to develop techniques and protocols that will improve geoscientists' interpretational accuracy. We asked 184 academic and industry experts to interpret a typical oil-industry synthetic seismic reflection data set and found that just over one-third got the "right" answer. Using multivariate analyses we show that interpretational accuracy is significantly improved for experts educated to the level of a Master's degree and/or doctorate (Ph.D.) (regardless of years of experience). Furthermore, although only 18 of 184 experts validated their interpretation by checking geometric and evolutionary feasibility, these experts were almost three times more likely to produce the correct result than those that did not. These results would not have been apparent from traditional detailed expert elicitation studies, as their sample sizes are too small. Our findings strongly suggest that significant improvements in the reliability of interpretations of inherently uncertain geological data sets could be made by increasing the proportion of people recruited into industry and academia who have a Master's or Ph.D. degree, and by changes to industry workflows and quality assurance procedures to explicitly include validation techniques. © 2012 Geological Society of America.
Yielding G.,Badley Geoscience Ltd |
Lykakis N.,University of Edinburgh |
Lykakis N.,Midland Valley Exploration Ltd. |
Underhill J.R.,University of Edinburgh
Petroleum Geoscience | Year: 2011
Exploration well 50/26b-6 in the UK Southern North Sea discovered a trap containing a gas-bearing Rotliegend Group (Leman Sandstone Formation) reservoir which was a major surprise at the time of drilling in that its gas composition was approximately 50% CO 2 (with 9% N2 and the remainder methane). Christened the 'Fizzy Discovery', the accumulation was appraised by well 50/26b-8. Subsequently, another CO 2-rich discovery (Oak) was made along-strike in nearby block 54/1b. Column heights at the well locations are of the order of a few tens of metres, but at the Fizzy Discovery the column height at the trap crest is estimated to be over 200 m. Interpretation of a high fidelity PSTM 3D seismic dataset has been constrained by 33 exploration wells allowing fault geometries and stratigraphic offsets to be determined with confidence. Despite late-stage (Late Cretaceous) structural inversion, the net boundary-fault offset is sufficient in both the Fizzy and Oak discoveries to almost breach the Zechstein Group evaporite super-seal, and the CO 2-bearing Rotliegend Group in the footwall is now juxtaposed against hanging wall sediments of the uppermost Zechstein Group. Hence, these Zechstein Group units evidently act as a robust long-term side-seal for the carbon dioxide column. The Fizzy and Oak accumulations are noteworthy in providing a natural demonstration of top seal and fault side-seal integrity for carbon dioxide in a subsurface reservoir, that has remained intact over a geological timescale in what is otherwise a prolific methane-rich reservoir play fairway. © 2011 EAGE/Geological Society of London.
Johnson G.,University of Calgary |
Johnson G.,Midland Valley Exploration Ltd. |
Mayer B.,University of Calgary |
Shevalier M.,University of Calgary |
And 2 more authors.
International Journal of Greenhouse Gas Control | Year: 2011
During CO2 storage operations in mature oilfields or saline aquifers it is desirable to trace the movement of injected CO2 for verification and safety purposes. We demonstrate the successful use of carbon isotope abundance ratios for tracing the movement of CO2 injected at the Cardium CO2 Storage Monitoring project in Alberta between 2005 and 2007. Injected CO2 had a δ13C value of -4.6±1.1‰ that was more than 10‰ higher than the carbon isotope ratios of casing gas CO2 prior to CO2 injection with average δ13C values ranging from -15.9 to -23.5‰. After commencement of CO2 injection, δ13C values of casing gas CO2 increased in all observation wells towards those of the injected CO2 consistent with a two-source endmember mixing model. At four wells located in a NE-SW trend with respect to the injection wells, breakthrough of injected CO2 was registered chemically (>50mol% CO2) and isotopically 1-6 months after commencement of CO2 injection resulting in cumulative CO2 fluxes exceeding 100,000m3 during the observation period. At four other wells, casing gas CO2 contents remained below 5mol% resulting in low cumulative CO2 fluxes (<2000m3) throughout the entire observation period, but carbon isotope ratios indicated contributions between <30 and 80% of injected CO2. Therefore, we conclude that monitoring the movement of CO2 in the injection reservoir with geochemical and isotopic techniques is an effective approach to determine plume expansion and to identify potential preferential flowpaths provided that the isotopic composition of injected CO2 is constant and distinct from that of baseline CO2.. © 2011 Elsevier Ltd.
Midland Valley Exploration Ltd. | Date: 2015-09-04
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