| 1. |
- Abbaszadeh Shahri, A., et al.
(författare)
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A Novel Approach to Uncertainty Quantification in Groundwater Table Modeling by Automated Predictive Deep Learning
- 2022
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Ingår i: Natural Resources Research. - : Springer Nature. - 1520-7439 .- 1573-8981. ; 31:3, s. 1351-1373
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Tidskriftsartikel (refereegranskat)abstract
- Uncertainty quantification (UQ) is an important benchmark to assess the performance of artificial intelligence (AI) and particularly deep learning ensembled-based models. However, the ability for UQ using current AI-based methods is not only limited in terms of computational resources but it also requires changes to topology and optimization processes, as well as multiple performances to monitor model instabilities. From both geo-engineering and societal perspectives, a predictive groundwater table (GWT) model presents an important challenge, where a lack of UQ limits the validity of findings and may undermine science-based decisions. To overcome and address these limitations, a novel ensemble, an automated random deactivating connective weights approach (ARDCW), is presented and applied to retrieved geographical locations of GWT data from a geo-engineering project in Stockholm, Sweden. In this approach, the UQ was achieved via a combination of several derived ensembles from a fixed optimum topology subjected to randomly switched off weights, which allow predictability with one forward pass. The process was developed and programmed to provide trackable performance in a specific task and access to a wide variety of different internal characteristics and libraries. A comparison of performance with Monte Carlo dropout and quantile regression using computer vision and control task metrics showed significant progress in the ARDCW. This approach does not require changes in the optimization process and can be applied to already trained topologies in a way that outperforms other models.
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| 2. |
- Guntoro, Pratama Istiadi, 1993-, et al.
(författare)
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Textural Quantification and Classification of Drill Cores for Geometallurgy: Moving Toward 3D with X-ray Microcomputed Tomography (µCT)
- 2020
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Ingår i: Natural Resources Research. - : Springer. - 1520-7439 .- 1573-8981. ; 29:6, s. 3547-3565
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Tidskriftsartikel (refereegranskat)abstract
- Texture is one of the critical parameters that affect the process behavior of ore minerals. Traditionally, texture has been described qualitatively, but recent works have shown the possibility to quantify mineral textures with the help of computer vision and digital image analysis. Most of these studies utilized 2D computer vision to evaluate mineral textures, which is limited by stereological error. On the other hand, the rapid development of X-ray microcomputed tomography (µCT) has opened up new possibilities for 3D texture analysis of ore samples. This study extends some of the 2D texture analysis methods, such as association indicator matrix (AIM) and local binary pattern (LBP) into 3D to get quantitative textural descriptors of drill core samples. The sensitivity of the methods to textural differences between drill cores is evaluated by classifying the drill cores into three textural classes using methods of machine learning classification, such as support vector machines and random forest. The study suggested that both AIM and LBP textural descriptors could be used for drill core classification with overall classification accuracy of 84–88%.
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| 3. |
- Höök, Mikael, 1982-, et al.
(författare)
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Descriptive and predictive growth curves in energy system analysis
- 2011
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Ingår i: Natural Resources Research. - : Springer Science and Business Media LLC. - 1520-7439 .- 1573-8981. ; 20:2, s. 103-116
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Tidskriftsartikel (refereegranskat)abstract
- This study reviews a variety of growth curve models and the theoretical frameworks that lay behind them. In many systems, growth patterns are, or must, ultimately be subjected to some form of limitation. A number of curve models have been developed to describe and predict such behaviours. Symmetric growth curves have frequently been used for forecasting fossil fuel production, but others have expressed a need for more flexible and asymmetric models. A number of examples show differences and applications of various growth curve models. It is concluded that these growth curve models can be utilised as forecasting tools, but are do not necessarily provide better predictions than any other method. Consequently, growth curve models and other forecasting methods should be used together to provide a triangulated forecast. Furthermore, the growth curve methodology offers a simple tool for resource management to determine what might happen to future production if resource availability poses a problem. In the light of peak oil and the awareness of natural resources as a basis for the continued well-being of society and mankind, resource management should be an important factor in future social planning.
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| 4. |
- Höök, Mikael, 1982-, et al.
(författare)
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Growth rates of global energy systems and future outlooks
- 2012
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Ingår i: Natural Resources Research. - : Springer Science and Business Media LLC. - 1520-7439 .- 1573-8981. ; 21:1, s. 23-41
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Tidskriftsartikel (refereegranskat)abstract
- The world is interconnected and powered by a number of global energy systems using fossil, nuclear, or renewable energy. This study reviews historical time series of energy production and growth for various energy sources. It compiles a theoretical and empirical foundation for understanding the behaviour underlying global energy systems' growth. The most extreme growth rates are found in fossil fuels. The presence of scaling behaviour, i.e. proportionality between growth rate and size, is established. The findings are used to investigate the consistency of several long-range scenarios expecting rapid growth for future energy systems. The validity of such projections is questioned, based on past experience. Finally, it is found that even if new energy systems undergo a rapid "oil boom"-development - i.e. they mimic the most extreme historical events - their contribution to global energy supply by 2050 will be marginal.
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| 5. |
- Höök, Mikael, 1982-, et al.
(författare)
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The evolution of giant oil field production behaviour
- 2009
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Ingår i: Natural Resources Research. - : Springer Science and Business Media LLC. - 1520-7439 .- 1573-8981. ; 18:1, s. 39-56
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Tidskriftsartikel (refereegranskat)abstract
- The giant oil fields of the world are only a small fraction of the total number of fields, but their importance is huge. Over 50% of the world oil production came from giants by 2005 and more than haft of the worlds ultimate reserves are found in giants. Based on this it is reasonable to assume that the future development of the giant oil fields will have a significant impact on the world oil supply. In order to better understand the giant fields and their future behaviour one must first understand their history. This study has used a comprehensive database on giant oil fields in order to determine their typical parameters, such as the average decline rate and life-times of giants. The evolution of giant oil field behaviour has been investigated to better understand future behaviour. One conclusion is that new technology and production methods have generally lead to high depletion rate and rapid decline. The historical trend points towards high decline rates of fields currently on plateau production. The peak production generally occurs before half the ultimate reserves have been produced in giant oil fields. A strong correlation between depletion-at-peak and average decline rate is also found, verifying that high depletion rate leads to rapid decline. Our result also implies that depletion analysis can be used to rule out unrealistic production expectations from a known reserve, or to connect an estimated production level to a needed reserve base.
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| 6. |
- Höök, Mikael, 1982-, et al.
(författare)
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Trends in U.S. recoverable coal supply estimates and future production outlooks
- 2010
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Ingår i: Natural Resources Research. - : Springer Science and Business Media LLC. - 1520-7439 .- 1573-8981. ; 19:3, s. 189-208
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Tidskriftsartikel (refereegranskat)abstract
- The geological coal resource of the U.S. is abundant and proved coal reserves are listed as the world’s largest. However, the reserves are unevenly distributed and located in a small number of states, giving them major influence over future production. A long history of coal mining provides detailed time series of production and reserve estimates, which can be used to identify historical trends. In reviewing the historical evolution of coal reserves, one can state that the trend here does not point towards any major increases in available recoverable reserves; rather the opposite is true due to restrictions and increased focus on environmental impacts from coal extraction. Future coal production will not be entirely determined by what is geologically available, but rather by the fraction of that amount that is practically recoverable. Consequently, the historical trend towards reduced recoverable amounts is likely to continue into the future, with even stricter regulations imposed by increased environmental concern. Long-term outlooks can be created in many ways, but ultimately the production must be limited by recoverable volumes since coal is a finite resource. The geologic amounts of coal are of much less importance to future production than the practically recoverable volumes. The geological coal supply might be vast, but the important question is how large the share that can be extracted under present restrictions are and how those restrictions will develop in the future. Production limitations might therefore appear much sooner than previously expected.
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| 7. |
- Höök, Mikael, 1982-, et al.
(författare)
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Validity of the fossil fuel production outlooks in the IPCC Emission Scenarios
- 2010
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Ingår i: Natural Resources Research. - : Springer Science and Business Media LLC. - 1520-7439 .- 1573-8981. ; 19:2, s. 63-81
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Tidskriftsartikel (refereegranskat)abstract
- Anthropogenic global warming caused by CO2 emissions is strongly and fundamentally linked to future energy production. The Special Report on Emission Scenarios (SRES) from 2000 contains 40 scenarios for future fossil fuel production and is used by the IPCC to assess future climate change. Previous scenarios were withdrawn after exaggerating one or several trends. This study investigates underlying assumptions on resource availability and future production expectations to determine whether exaggerations can be found in the present set of emission scenarios as well. It is found that the SRES unnecessarily takes an overoptimistic stance and that future production expectations are leaning towards spectacular increases from present output levels. In summary, we can only encourage the IPCC to involve more resource experts and natural science in future emission scenarios. The current set, SRES, is biased toward exaggerated resource availability and unrealistic expectations on future production outputs from fossil fuels.
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| 8. |
- Lu, Zhaohui, et al.
(författare)
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Microseismic Monitoring of Hydraulic Fracture Propagation and Seismic Risks in Shale Reservoir with a Steep Dip Angle
- 2022
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Ingår i: Natural Resources Research. - : Springer Nature. - 1520-7439 .- 1573-8981. ; 31:5, s. 2973-2993
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Tidskriftsartikel (refereegranskat)abstract
- Hydraulic fracturing is an essential technique to increase reservoir permeability and enhance the production of shale gas. When the dip angle is steep and geological condition is complex, hydraulic fractures may behave complexly, and research on this topic is critical for the shale gas industry. This paper reports a case study of hydraulic fracturing in a shale reservoir with a steep dip angle. We monitored pump data, including the injection rate and fluid pressure. Microseismic monitoring was also used to record the seismic events and monitor the hydraulic fracture propagation. Our results validated that microseismic monitoring is a feasible technique to monitor the hydraulic fracture propagation in shale reservoirs with steep dip angles. Moreover, the variation in depth of shale reservoir induces significant alternation of local in situ stress states, in which cases the fracture propagation pathway is more complex, and where microseismic monitoring is necessary to acquire the hydraulic fracture distribution. Besides, all sound sources, including quarries and rivers, should be eliminated during microseismic station arrangement to improve accuracy of microseismic signals. Moreover, the relationship between the maximum magnitude of seismic event and fluid injection volume was validated further in this study. Finally, unexpected faults and aquifers may affect hydraulic fracture propagation due to the steep dip angle of the target shale reservoir. Thus, a comprehensive geological survey is essential for better hydraulic fracturing design. Our results provide first-hand in situ hydraulic fracturing data and provide important implications for shale gas development, especially for those shale reservoirs with steep dip angles.
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| 9. |
- Naghibi, Seyed Amir, et al.
(författare)
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Water Resources Management Through Flood Spreading Project Suitability Mapping Using Frequency Ratio, k-nearest Neighbours, and Random Forest Algorithms
- 2020
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Ingår i: Natural Resources Research. - : Springer Science and Business Media LLC. - 1520-7439 .- 1573-8981. ; 29:3, s. 1915-1933
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Tidskriftsartikel (refereegranskat)abstract
- Lack of water resources is a common issue in many countries, especially in the Middle East. Flood spreading project (FSP) is an artificial recharge technique, which is generally suggested for arid and semi-arid areas with two major aims including (1) flood mitigation and (2) artificial recharge of groundwater. This study implemented three state-of-the-art popular models including frequency ratio (FR), k-nearest neighbours (KNN), and random forest (RF) for determining the suitability of land for FSP. At the first step, suitable areas for FSP were identified according to the national guidelines and the literature. The identified areas were then verified by multiple field surveys. To produce FSP land suitability maps, several FSP conditioning factors such as topographical (i.e. slope, plan curvature, and profile curvature), hydrogeological (i.e. transmissivity, aquifer thickness, and electrical conductivity), hydrological (i.e. rainfall, distance from rivers, river density, and permeability), lithology, and land use were considered as input to the models. For the FR modelling, classified layers of the aforementioned variables were used, while their continuous layers were implemented in the KNN and RF algorithms. At the last step, receiver operating characteristic (ROC) curve was used to assess the ability and accuracy of the applied algorithms. Based on the findings, the area under the curve of ROC for the RF, KNN, and FR models was 97.1, 94.6, and 89.2%, respectively. Furthermore, transmissivity, slope, aquifer thickness, distance from rivers, rainfall, and electrical conductivity were recognized as the most influencing factors in the modelling procedure. The findings of this study indicated that the application of RF, KNN, and FR can be suggested for identification of suitable areas for FSP establishment in other regions.
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| 10. |
- Nwaila, Glen T., et al.
(författare)
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Constraints on the Geometry and Gold Distribution in the Black Reef Formation of South Africa Using 3D Reflection Seismic Data and Micro-X-ray Computed Tomography
- 2022
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Ingår i: Natural Resources Research. - : Springer. - 1520-7439 .- 1573-8981. ; 31:3, s. 1225-1244
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Tidskriftsartikel (refereegranskat)abstract
- Geological and geophysical models are essential for developing reliable mine designs and mineral processing flowsheets. For mineral resource assessment, mine planning, and mineral processing, a deeper understanding of the orebody's features, geology, mineralogy, and variability is required. We investigated the gold-bearing Black Reef Formation in the West Rand and Carletonville goldfields of South Africa using approaches that are components of a transitional framework toward fully digitized mining: (1) high-resolution 3D reflection seismic data to model the orebody; (2) petrography to characterize Au and associated ore constituents (e.g., pyrite); and (3) 3D micro-X-ray computed tomography (µCT) and machine learning to determine mineral association and composition. Reflection seismic reveals that the Black Reef Formation is a planar horizon that dips < 10° and has a well-preserved and uneven paleotopography. Several large-scale faults and dikes (most dipping between 65° and 90°) crosscut the Black Reef Formation. Petrography reveals that gold is commonly associated with pyrite, implying that µCT can be used to assess gold grades using pyrite as a proxy. Moreover, we demonstrate that machine learning can be used to discriminate between pyrite and gold based on physical characteristics. The approaches in this study are intended to supplement rather than replace traditional methodologies. In this study, we demonstrated that they permit novel integration of micro-scale observations into macro-scale modeling, thus permitting better orebody assessment for exploration, resource estimation, mining, and metallurgical purposes. We envision that such integrated approaches will become a key component of future geometallurgical frameworks.
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