Pub Date : 2019-12-01DOI: 10.1080/22020586.2019.12073089
R. Hewson, E. Chinkaka, M. Meijde, B. Baugh, N. Titus, J. P. Mubita
Summary Recent improvements in available multi-spectral satelliteborne shortwave infrared sensors and their spatial resolution opens up the opportunity for furthering surface mineralogy mapping. Their image interpretation can be augmented with regional geophysics, e.g. subsurface structural information via magnetics or fine tuning the interpretation of mineral chemistry using radioelement data. The new higher spatial resolution satellite WorldView-3 sensor is compared in this study with the ASTER satellite imagery over the Haib copper prospect in southern Namibia using published geology and airborne hyperspectral imagery control. The results show an improvement using higher spatial resolution combined with improvements in SWIR imagery for the mapping of different AlOH clays, potentially related phyllic and argillic alteration that may be associated with structurally controlled alteration and mineralisation.
{"title":"Geological investigations with high spatial resolution WV-3 satellite imagery and regional geophysics at the Haib Cu porphyry, Namibia","authors":"R. Hewson, E. Chinkaka, M. Meijde, B. Baugh, N. Titus, J. P. Mubita","doi":"10.1080/22020586.2019.12073089","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073089","url":null,"abstract":"Summary Recent improvements in available multi-spectral satelliteborne shortwave infrared sensors and their spatial resolution opens up the opportunity for furthering surface mineralogy mapping. Their image interpretation can be augmented with regional geophysics, e.g. subsurface structural information via magnetics or fine tuning the interpretation of mineral chemistry using radioelement data. The new higher spatial resolution satellite WorldView-3 sensor is compared in this study with the ASTER satellite imagery over the Haib copper prospect in southern Namibia using published geology and airborne hyperspectral imagery control. The results show an improvement using higher spatial resolution combined with improvements in SWIR imagery for the mapping of different AlOH clays, potentially related phyllic and argillic alteration that may be associated with structurally controlled alteration and mineralisation.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"53 1","pages":"1 - 5"},"PeriodicalIF":0.0,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87502594","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-12-01DOI: 10.1080/22020586.2019.12072935
G. O’Halloran, Robbie Benson, C. Dempsey
Summary A late Jurassic pulse of igneous activity occurred within the Exmouth Sub-basin, with several submarine volcanic extrusive centres evident, along with contemporaneous intrusive feeder systems that fed them. The extrusive volcanics have been mapped on 3D seismic datasets and include cone-shaped vents up to 8 km in diameter and >250 m high with flanking lava flows and volcanoclastic facies. Feeder dykes and more stratiform sill systems have also been mapped, and in some cases the former can be directly related to individual volcanic extrusive complexes. Several wells have penetrated lateral equivalents to seismically defined volcanic intervals. These wells intersected thin sequences of distal volcanic facies – invariably interpreted as “crystal tuffs” which is consistent with them being distal fall deposits from a submarine basaltic/intermediate volcanic centre. Timing of the volcanic activity has been relatively well constrained by the ages of onlapping marine sedimentary sequences. A depositional model in which mafic-intermediate volcanic extrusives were erupted into a submarine setting within intermediate water depths (~100s m) is proposed, and modern-day analogues discussed.
{"title":"Jurassic igneous activity in the Exmouth Sub-basin: Insights from new 3D seismic","authors":"G. O’Halloran, Robbie Benson, C. Dempsey","doi":"10.1080/22020586.2019.12072935","DOIUrl":"https://doi.org/10.1080/22020586.2019.12072935","url":null,"abstract":"Summary A late Jurassic pulse of igneous activity occurred within the Exmouth Sub-basin, with several submarine volcanic extrusive centres evident, along with contemporaneous intrusive feeder systems that fed them. The extrusive volcanics have been mapped on 3D seismic datasets and include cone-shaped vents up to 8 km in diameter and >250 m high with flanking lava flows and volcanoclastic facies. Feeder dykes and more stratiform sill systems have also been mapped, and in some cases the former can be directly related to individual volcanic extrusive complexes. Several wells have penetrated lateral equivalents to seismically defined volcanic intervals. These wells intersected thin sequences of distal volcanic facies – invariably interpreted as “crystal tuffs” which is consistent with them being distal fall deposits from a submarine basaltic/intermediate volcanic centre. Timing of the volcanic activity has been relatively well constrained by the ages of onlapping marine sedimentary sequences. A depositional model in which mafic-intermediate volcanic extrusives were erupted into a submarine setting within intermediate water depths (~100s m) is proposed, and modern-day analogues discussed.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"78 1 1","pages":"1 - 6"},"PeriodicalIF":0.0,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80208363","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-12-01DOI: 10.1080/22020586.2019.12073208
Karen Gilgallon, Anne Tomlinson, R. Mortimer
Summary Electromagnetic (EM) systems are often described with varying technical specifications and standards, making it difficult to directly compare and assess their application to practical field examples. Exemplar case studies provided by contractors, whilst highlighting system capabilities, do not necessarily help to refine the suitability of the system across different geological targets and environments. Test ranges provide an opportunity for direct and consistent comparison of multiple systems for objective assessment. The Forrestania and Nepean EM test ranges in Western Australia consist of readily accessible land, openly available for testing by airborne, ground and downhole EM systems. Multiple conductors at varying depths beneath 10-20 Siemens (S) conductive overburden provide challenging, real-world conductive targets. Surveying using different EM systems allows for a direct comparison of system detection and resolution capabilities in a conductive regolith environment. The conductors have been well defined by drilling and provide a large range of metrics available for measurement, varying from 60-400 m in depth, 5,000-10,000 S in conductance, and with variable lateral profiles and depth extents. Multiple airborne, ground and downhole EM systems have utilised these test ranges, and several have made their data freely available for review. These include ground methods such as moving loop EM, fixed loop EM, SAMSON, downhole EM, and helicopter systems including HeliSAM FLEM, SkyTEM, VTEM, HELITEM, HeliGEOTEM, XTEM, HoistEM and AeroTEM. The SPECTREM, and Xcite airborne systems plan to fly the test range in the near future. Comparison of the airborne results, show that most of the post-2007 systems have been adequate to good at detecting the shallow IR2 conductor at Forrestania under conductive regolith. Only the hybrid grounded loop HeliSAM system has successfully detected the deep IR4 conductor at Forrestania.
{"title":"The Forrestania and Nepean electromagnetic test ranges, Western Australia – a comparison of airborne systems","authors":"Karen Gilgallon, Anne Tomlinson, R. Mortimer","doi":"10.1080/22020586.2019.12073208","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073208","url":null,"abstract":"Summary Electromagnetic (EM) systems are often described with varying technical specifications and standards, making it difficult to directly compare and assess their application to practical field examples. Exemplar case studies provided by contractors, whilst highlighting system capabilities, do not necessarily help to refine the suitability of the system across different geological targets and environments. Test ranges provide an opportunity for direct and consistent comparison of multiple systems for objective assessment. The Forrestania and Nepean EM test ranges in Western Australia consist of readily accessible land, openly available for testing by airborne, ground and downhole EM systems. Multiple conductors at varying depths beneath 10-20 Siemens (S) conductive overburden provide challenging, real-world conductive targets. Surveying using different EM systems allows for a direct comparison of system detection and resolution capabilities in a conductive regolith environment. The conductors have been well defined by drilling and provide a large range of metrics available for measurement, varying from 60-400 m in depth, 5,000-10,000 S in conductance, and with variable lateral profiles and depth extents. Multiple airborne, ground and downhole EM systems have utilised these test ranges, and several have made their data freely available for review. These include ground methods such as moving loop EM, fixed loop EM, SAMSON, downhole EM, and helicopter systems including HeliSAM FLEM, SkyTEM, VTEM, HELITEM, HeliGEOTEM, XTEM, HoistEM and AeroTEM. The SPECTREM, and Xcite airborne systems plan to fly the test range in the near future. Comparison of the airborne results, show that most of the post-2007 systems have been adequate to good at detecting the shallow IR2 conductor at Forrestania under conductive regolith. Only the hybrid grounded loop HeliSAM system has successfully detected the deep IR4 conductor at Forrestania.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"22 1","pages":"1 - 4"},"PeriodicalIF":0.0,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72645064","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-12-01DOI: 10.1080/22020586.2019.12072917
Dragos Gavriliu, J. Batchelor
Summary This paper describes a novel approach to solving borehole rugosity for single detector gamma-gamma density logging. Modelling the space investigated by the gamma-gamma density tool provides the basis for deriving an applied rugosity correction. This paper also describes how the same correction models when applied to dual density tool detectors can increase the vertical resolution of the tool revealing otherwise hidden formation heterogeneity. Measurements made with single detector gamma-gamma density tools are accurate non-rugose (smooth) boreholes whereas measurements made in rugose (rough) boreholes are typically biased low, due to the undesirable effects of low-density borehole fluid, water or air sitting between the formation and the source or detector and in the path of gamma rays.
{"title":"Drillhole rugosity correction for gamma-gamma density tools – A space modelling approach","authors":"Dragos Gavriliu, J. Batchelor","doi":"10.1080/22020586.2019.12072917","DOIUrl":"https://doi.org/10.1080/22020586.2019.12072917","url":null,"abstract":"Summary This paper describes a novel approach to solving borehole rugosity for single detector gamma-gamma density logging. Modelling the space investigated by the gamma-gamma density tool provides the basis for deriving an applied rugosity correction. This paper also describes how the same correction models when applied to dual density tool detectors can increase the vertical resolution of the tool revealing otherwise hidden formation heterogeneity. Measurements made with single detector gamma-gamma density tools are accurate non-rugose (smooth) boreholes whereas measurements made in rugose (rough) boreholes are typically biased low, due to the undesirable effects of low-density borehole fluid, water or air sitting between the formation and the source or detector and in the path of gamma rays.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"2 1","pages":"1 - 7"},"PeriodicalIF":0.0,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75006049","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-12-01DOI: 10.1080/22020586.2019.12073009
R. Hansberry, S. Holford, R. King, N. Debenham
Summary Predicting the interconnectivity and permeability of fractures at any scale remains a fundamental challenge in structural geology. Models which predict the likelihood of fracture opening based on their relation to the stress field can be applied at scales of 100s of metres to kilometres. Increasingly however, an understanding of how networks of the smallest-scale (sub-seismic to mm) natural fractures permit fluid flow in the subsurface appears key to predicting and exploiting these pathways. Here, we apply the nascent method of network topology to natural fracture networks to a fossilised fault damage zone in the Otway Basin. Network connectivity and the potential to percolate fluids has been shown to be directly related to the topology, and intensity of fracturing. This technique is relatively straightforward, provides a range of parameters to define various aspects of a fracture network (e.g. intensity, connectivity), and is independent of the scale and geometry of the structures of interest. We integrate this technique with traditional structural analysis to illustrate the scale of fracturing around a region-scale fault and constrain spatial variation in permeability associated with the fracture network. We also illustrate how elements of this technique might be applied to existing sub-surface data.
{"title":"Using network topology to constrain fracture network permeability","authors":"R. Hansberry, S. Holford, R. King, N. Debenham","doi":"10.1080/22020586.2019.12073009","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073009","url":null,"abstract":"Summary Predicting the interconnectivity and permeability of fractures at any scale remains a fundamental challenge in structural geology. Models which predict the likelihood of fracture opening based on their relation to the stress field can be applied at scales of 100s of metres to kilometres. Increasingly however, an understanding of how networks of the smallest-scale (sub-seismic to mm) natural fractures permit fluid flow in the subsurface appears key to predicting and exploiting these pathways. Here, we apply the nascent method of network topology to natural fracture networks to a fossilised fault damage zone in the Otway Basin. Network connectivity and the potential to percolate fluids has been shown to be directly related to the topology, and intensity of fracturing. This technique is relatively straightforward, provides a range of parameters to define various aspects of a fracture network (e.g. intensity, connectivity), and is independent of the scale and geometry of the structures of interest. We integrate this technique with traditional structural analysis to illustrate the scale of fracturing around a region-scale fault and constrain spatial variation in permeability associated with the fracture network. We also illustrate how elements of this technique might be applied to existing sub-surface data.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"5 1","pages":"1 - 4"},"PeriodicalIF":0.0,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75359160","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-12-01DOI: 10.1080/22020586.2019.12073228
N. Goujon, S. Rentsch, L. Combee, F. Guizelin, K. F. Ahmad
Summary The towed streamer market is moving towards the widespread use of multicomponent streamers. This type of streamer contains hydrophones and particle motion sensors which are used to carry out receiver-side deghosting of the data. The main source of noise on the particle motion sensors is streamer transverse vibration, and it can be challenging to obtain a high enough signal to noise ratio to use this data in the de-ghosting process. In this paper, we study how the characteristics of transverse vibration noise are affected by the choice of the streamer mechanical platform. To compare the implications of design options we built different streamer sections with dense single sensor sampling, identical electronic backbones and MEMS sensors. We towed them together under different tensions in a field experiment and observed that, as expected, the transverse vibration noise was the dominant noise mode, with dispersion characteristics depending on the streamer bending stiffness. We also found that the noise amplitude and maximum frequency (under the same towing conditions) depends on the mechanical properties of the cable, and that they could be reduced by using a new type of gel optimized to dampen vibration. As a result of theoretical modelling and these field observations we propose a new approach to streamer noise attenuation which involves optimising the mechanical characteristics and using non-uniform single sensor sampling in the design of the cable. This avoids some of the compromises we incur using analog arrays and the high cost of single sensor, uniform Nyquist sampling.
{"title":"Current and future multicomponent towed streamer design","authors":"N. Goujon, S. Rentsch, L. Combee, F. Guizelin, K. F. Ahmad","doi":"10.1080/22020586.2019.12073228","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073228","url":null,"abstract":"Summary The towed streamer market is moving towards the widespread use of multicomponent streamers. This type of streamer contains hydrophones and particle motion sensors which are used to carry out receiver-side deghosting of the data. The main source of noise on the particle motion sensors is streamer transverse vibration, and it can be challenging to obtain a high enough signal to noise ratio to use this data in the de-ghosting process. In this paper, we study how the characteristics of transverse vibration noise are affected by the choice of the streamer mechanical platform. To compare the implications of design options we built different streamer sections with dense single sensor sampling, identical electronic backbones and MEMS sensors. We towed them together under different tensions in a field experiment and observed that, as expected, the transverse vibration noise was the dominant noise mode, with dispersion characteristics depending on the streamer bending stiffness. We also found that the noise amplitude and maximum frequency (under the same towing conditions) depends on the mechanical properties of the cable, and that they could be reduced by using a new type of gel optimized to dampen vibration. As a result of theoretical modelling and these field observations we propose a new approach to streamer noise attenuation which involves optimising the mechanical characteristics and using non-uniform single sensor sampling in the design of the cable. This avoids some of the compromises we incur using analog arrays and the high cost of single sensor, uniform Nyquist sampling.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"89 1","pages":"1 - 4"},"PeriodicalIF":0.0,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73658473","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-12-01DOI: 10.1080/22020586.2019.12073087
S. Matthews, E. Stolz, A. Carlton
Summary The Geological Survey of NSW (GSNSW) are the custodians of both government and company geophysical data throughout NSW. The NSW Government has acquired a suite of over 60 airborne magnetic and ground gravity surveys since the 1990s, the data from which has been merged into statewide grids that are delivered, alongside the original survey data, through our web portal ‘MinView’. These grids are available for Magnetics, Radiometric, Gravity and Digital Elevation Models. Open-file exploration and mining company data dates back over 60 years, spanning a wide range of conventions, formats, and often missing large amounts of information. GSNSW have committed to a large-scale quality assessment of these data to deliver curated open-file company data to the public via MinView and allow incorporation of good quality company data into the statewide geophysical imagery. This will improve the statewide images because the line spacing of the company surveys is typically much smaller than the regional surveys flown by the government.
{"title":"New from Old: Advancing Statewide Geophysics with Company Data","authors":"S. Matthews, E. Stolz, A. Carlton","doi":"10.1080/22020586.2019.12073087","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073087","url":null,"abstract":"Summary The Geological Survey of NSW (GSNSW) are the custodians of both government and company geophysical data throughout NSW. The NSW Government has acquired a suite of over 60 airborne magnetic and ground gravity surveys since the 1990s, the data from which has been merged into statewide grids that are delivered, alongside the original survey data, through our web portal ‘MinView’. These grids are available for Magnetics, Radiometric, Gravity and Digital Elevation Models. Open-file exploration and mining company data dates back over 60 years, spanning a wide range of conventions, formats, and often missing large amounts of information. GSNSW have committed to a large-scale quality assessment of these data to deliver curated open-file company data to the public via MinView and allow incorporation of good quality company data into the statewide geophysical imagery. This will improve the statewide images because the line spacing of the company surveys is typically much smaller than the regional surveys flown by the government.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"58 1","pages":"1 - 3"},"PeriodicalIF":0.0,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74105534","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-12-01DOI: 10.1080/22020586.2019.12073111
Megan Slade, P. Thomas
Summary Realising and protecting the value of near-field exploration and appraisal is a constant challenge, especially during the recent low oil price cycles. This paper discusses the 2015 Pyxis gas discovery, and the means by which a cost effective and value driven approach to data acquisition and optimisation drove the opportunity. The Pyxis field is situated approximately 10 km from the drilling manifold and centre of the Pluto Field. We will demonstrate how targeted studies, a carefully selected well location and data gathering programme when combined with a seismic survey synergies with the nearby Pluto Field, delivered a cost-effective, single-well discovery and appraisal. Pre-drill economic viability of Pyxis was challenged by the stratigraphic nature of the trap, significant seismic data issues, sub-tuning reservoir thickness and limited offset-well information. Opportunistic data gathering and cost-effective, detailed Quantitative interpretation (QI )work allowed these challenges to be overcome, and the prospect to be drilled. In the success case, the Pyxis-1 exploration well was planned to acquire sufficient data to obviate the need for further appraisal. Post-discovery evaluation continued the low-cost approach, using new Pluto Field seismic to assist reservoir characterisation. We conclude that this modest-sized, near-field opportunity has been optimized in terms of potential economic viability by using appropriate technology, targeted appraisal, and integration with nearby field activities.
{"title":"Pyxis – A study in cost-efficient near-field exploration, discovery and appraisal","authors":"Megan Slade, P. Thomas","doi":"10.1080/22020586.2019.12073111","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073111","url":null,"abstract":"Summary Realising and protecting the value of near-field exploration and appraisal is a constant challenge, especially during the recent low oil price cycles. This paper discusses the 2015 Pyxis gas discovery, and the means by which a cost effective and value driven approach to data acquisition and optimisation drove the opportunity. The Pyxis field is situated approximately 10 km from the drilling manifold and centre of the Pluto Field. We will demonstrate how targeted studies, a carefully selected well location and data gathering programme when combined with a seismic survey synergies with the nearby Pluto Field, delivered a cost-effective, single-well discovery and appraisal. Pre-drill economic viability of Pyxis was challenged by the stratigraphic nature of the trap, significant seismic data issues, sub-tuning reservoir thickness and limited offset-well information. Opportunistic data gathering and cost-effective, detailed Quantitative interpretation (QI )work allowed these challenges to be overcome, and the prospect to be drilled. In the success case, the Pyxis-1 exploration well was planned to acquire sufficient data to obviate the need for further appraisal. Post-discovery evaluation continued the low-cost approach, using new Pluto Field seismic to assist reservoir characterisation. We conclude that this modest-sized, near-field opportunity has been optimized in terms of potential economic viability by using appropriate technology, targeted appraisal, and integration with nearby field activities.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"2 1","pages":"1 - 4"},"PeriodicalIF":0.0,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74845366","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-12-01DOI: 10.1080/22020586.2019.12072976
M. Bates, S. Elieff, K. Kaski, David Howard, J. Brett, R. Lane
Summary Regional airborne gravity surveys are being acquired over much of the State of Western Australia by the Geological Survey of Western Australia (GSWA) and Geoscience Australia (GA) to provide coverage where existing ground gravity coverage is sparse. The acquisition and processing of these surveys poses several challenges. The data acquired by Sander Geophysics (SGL) using the AIRGrav system in Western Australia during 2018 was done so without control lines for reasons of cost efficiency, relying on the ground gravity to provide the necessary levelling corrections. Methodologies have been developed to achieve effective levelling under these circumstances, although the final result varies depending on the methodology used. Data acquired on earlier surveys with control lines are being used to compare and contrast to data acquired without them. Ongoing power spectrum analysis suggests a way in which the different methods may be judged objectively. Horizontal components of gravity are also acquired by AIRGrav. Levelling these components is a challenge under all circumstances. The relationships between the components expressed in potential field theory allow the different components data to be compared and checked for consistency. Digital elevation model (DEM) data acquired during the surveys provide a means for checking other sources of DEM typically employed for applying terrain corrections. The impact of inaccurate DEM data on the corrected gravity data overall is small but can be locally significant. Data quality of the regional surveys is high, but the end user should be aware of the limitations posed by the choices made in data acquisition and processing.
{"title":"Regional airborne gravity surveys in Western Australia: Considerations for the end user","authors":"M. Bates, S. Elieff, K. Kaski, David Howard, J. Brett, R. Lane","doi":"10.1080/22020586.2019.12072976","DOIUrl":"https://doi.org/10.1080/22020586.2019.12072976","url":null,"abstract":"Summary Regional airborne gravity surveys are being acquired over much of the State of Western Australia by the Geological Survey of Western Australia (GSWA) and Geoscience Australia (GA) to provide coverage where existing ground gravity coverage is sparse. The acquisition and processing of these surveys poses several challenges. The data acquired by Sander Geophysics (SGL) using the AIRGrav system in Western Australia during 2018 was done so without control lines for reasons of cost efficiency, relying on the ground gravity to provide the necessary levelling corrections. Methodologies have been developed to achieve effective levelling under these circumstances, although the final result varies depending on the methodology used. Data acquired on earlier surveys with control lines are being used to compare and contrast to data acquired without them. Ongoing power spectrum analysis suggests a way in which the different methods may be judged objectively. Horizontal components of gravity are also acquired by AIRGrav. Levelling these components is a challenge under all circumstances. The relationships between the components expressed in potential field theory allow the different components data to be compared and checked for consistency. Digital elevation model (DEM) data acquired during the surveys provide a means for checking other sources of DEM typically employed for applying terrain corrections. The impact of inaccurate DEM data on the corrected gravity data overall is small but can be locally significant. Data quality of the regional surveys is high, but the end user should be aware of the limitations posed by the choices made in data acquisition and processing.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"19 1","pages":"1 - 5"},"PeriodicalIF":0.0,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80807480","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-12-01DOI: 10.1080/22020586.2019.12072973
Tasman Gillfeather-Clark, E. Holden, D. Wedge, T. Horrocks, Carlie Byrne, M. Lawrence
Summary Seismic data processing and analysis focuses on identifying the arrival of seismic waves or ‘first-breaks’. The identification of the arrival of first breaks is complicated by the variance of recording quality typically found across the dataset. In an exploration setting, models need to be developed and refined multiple times. Picking these first breaks then becomes time consuming, limiting the interpreter to processing their dataset rather than considering the implications of their model. Machine Learning as a field continues to respond to many data centric issues within geoscience. However, the field as a whole continues to grapple with balancing the power of these new techniques against operator expertise and skill. This paper presents a methodology to identify the first break in seismic refraction data using a Long-Short Term Memory (LSTM) network, which is a recurrent network architecture. I propose one way to delineate between different groups of traces that the operator would intuitively pick differently, by using dynamic time warping to generate a distance matrix of the seismic traces for clustering. This clustering of trace types allows for a more targeted selection of training samples. I conclude with a proposed framework for the integration of operator skill with machine learning speed and repeatability.
{"title":"Viability of long-short term memory neural networks for seismic refraction first break detection – a preliminary study","authors":"Tasman Gillfeather-Clark, E. Holden, D. Wedge, T. Horrocks, Carlie Byrne, M. Lawrence","doi":"10.1080/22020586.2019.12072973","DOIUrl":"https://doi.org/10.1080/22020586.2019.12072973","url":null,"abstract":"Summary Seismic data processing and analysis focuses on identifying the arrival of seismic waves or ‘first-breaks’. The identification of the arrival of first breaks is complicated by the variance of recording quality typically found across the dataset. In an exploration setting, models need to be developed and refined multiple times. Picking these first breaks then becomes time consuming, limiting the interpreter to processing their dataset rather than considering the implications of their model. Machine Learning as a field continues to respond to many data centric issues within geoscience. However, the field as a whole continues to grapple with balancing the power of these new techniques against operator expertise and skill. This paper presents a methodology to identify the first break in seismic refraction data using a Long-Short Term Memory (LSTM) network, which is a recurrent network architecture. I propose one way to delineate between different groups of traces that the operator would intuitively pick differently, by using dynamic time warping to generate a distance matrix of the seismic traces for clustering. This clustering of trace types allows for a more targeted selection of training samples. I conclude with a proposed framework for the integration of operator skill with machine learning speed and repeatability.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"308 2 1","pages":"1 - 5"},"PeriodicalIF":0.0,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72949868","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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