Pub Date : 2019-12-01DOI: 10.1080/22020586.2019.12073107
C. Elders, T. Bernecker
Summary The widely used scheme of naming basins and their regional subdivisions on the North West Shelf emerged from relatively sparse data collected during the early stages of exploration. Such data allow the recognition of large-scale structures and depocentres with a broadly distinct tectono-stratigraphic framework. While that scheme has endured, the availability of extensive, high quality seismic data and stratigraphic information from numerous exploration wells means that we can define much more precisely the structural elements that comprise the margin and the stratigraphic signatures of the basin fill. This has highlighted some inconsistencies in the existing nomenclature, the presence of structural elements of different ages and the presence of boundaries between basins that sometimes can appear rather arbitrary. We present a revised map for the North West Shelf that shows the structural elements with distinct tectono-stratigraphic signatures that comprise the margin, and applies a consistent nomenclature to them. The aim is to provide a framework that will allow for the better demarcation of distinct hydrocarbon provinces and improved targeting of exploration programmes. This is a work in progress and we invite you to annotate the map shown on our poster with your own comments or to provide feedback via our blog.
{"title":"Revising the structural elements map of the North West Shelf","authors":"C. Elders, T. Bernecker","doi":"10.1080/22020586.2019.12073107","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073107","url":null,"abstract":"Summary The widely used scheme of naming basins and their regional subdivisions on the North West Shelf emerged from relatively sparse data collected during the early stages of exploration. Such data allow the recognition of large-scale structures and depocentres with a broadly distinct tectono-stratigraphic framework. While that scheme has endured, the availability of extensive, high quality seismic data and stratigraphic information from numerous exploration wells means that we can define much more precisely the structural elements that comprise the margin and the stratigraphic signatures of the basin fill. This has highlighted some inconsistencies in the existing nomenclature, the presence of structural elements of different ages and the presence of boundaries between basins that sometimes can appear rather arbitrary. We present a revised map for the North West Shelf that shows the structural elements with distinct tectono-stratigraphic signatures that comprise the margin, and applies a consistent nomenclature to them. The aim is to provide a framework that will allow for the better demarcation of distinct hydrocarbon provinces and improved targeting of exploration programmes. This is a work in progress and we invite you to annotate the map shown on our poster with your own comments or to provide feedback via our blog.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"1 1","pages":"1 - 2"},"PeriodicalIF":0.0,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89744235","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: 10.1080/22020586.2019.12073067
S. Jakica, Lucy I. Brisbout
Summary This study uses shallow passive seismic HVSR (horizontal-to-vertical spectral ratio) technique to determine the depth and extent of a Cenozoic paleochannel composed dominantly of sand and clay incised into the Proterozoic granitic basement of the Capricorn Orogen. The paleochannel contains sand-dominated intervals that host water that is presently being explored by Hastings Metals. There is some drilling data available but only a few drill cores intersect the basement. Improved understanding of the paleochannel geometry will assist with water exploration. The measured resonant frequency is related to shear wave velocity (Vs) and layer thickness. Passive seismic measurements at drill hole SWMB007 allow us to define a Vs for the regolith package overlying the basement. This Vs value is applied to 53 passive seismic measurements along Traverse 7 and the thickness of the paleochannel has been imaged in normalised H/V amplitude images. Along Traverse 7, HVSR data image a symmetrical paleochannel with a maximum depth of ~115 m. The geometry of the paleochannel imaged is broadly similar to the geometry obtained from 2.5D AEM inversion. However, the paleochannel has a greater maximum depth in AEM and some internal features of the paleochannel also differ.
{"title":"Application of passive seismic and AEM to 3D paleochannel imaging: Capricorn Orogen","authors":"S. Jakica, Lucy I. Brisbout","doi":"10.1080/22020586.2019.12073067","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073067","url":null,"abstract":"Summary This study uses shallow passive seismic HVSR (horizontal-to-vertical spectral ratio) technique to determine the depth and extent of a Cenozoic paleochannel composed dominantly of sand and clay incised into the Proterozoic granitic basement of the Capricorn Orogen. The paleochannel contains sand-dominated intervals that host water that is presently being explored by Hastings Metals. There is some drilling data available but only a few drill cores intersect the basement. Improved understanding of the paleochannel geometry will assist with water exploration. The measured resonant frequency is related to shear wave velocity (Vs) and layer thickness. Passive seismic measurements at drill hole SWMB007 allow us to define a Vs for the regolith package overlying the basement. This Vs value is applied to 53 passive seismic measurements along Traverse 7 and the thickness of the paleochannel has been imaged in normalised H/V amplitude images. Along Traverse 7, HVSR data image a symmetrical paleochannel with a maximum depth of ~115 m. The geometry of the paleochannel imaged is broadly similar to the geometry obtained from 2.5D AEM inversion. However, the paleochannel has a greater maximum depth in AEM and some internal features of the paleochannel also differ.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"14 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":"84395183","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: 10.1080/22020586.2019.12073061
W. Tan, V. Mikhaltsevitch, M. Lebedev, S. Glubokovskikh, B. Gurevich
Summary In this study we examine the effect of the boundary conditions on the laboratory measurements of the elastic properties of a fluid-saturated sedimentary rock at low frequencies. In laboratory experiments associated with studying fluid effects on elastic properties of a porous rock sample, the tested sample cannot be completely sealed due to the presence of the fluid lines connected to its pore space. These lines form a pore-fluid storage which can affect the results of the elastic moduli measurements of fluid-saturated rocks. We developed a modified version of the Gassmann model which can estimate the bulk moduli of fully saturated rocks in dependence on the capacity of the pore-fluid storage. Here, we compare the predictions of the modified Gassmann model with the moduli measured on an n-decane-saturated limestone sample with the volume of the pore-fluid storage changing from 2 ml to 260 ml. The experimental results were obtained using a low-frequency apparatus based on the forced-oscillation method at a frequency of 0.1 Hz. We demonstrate that the predictions of the modified Gassmann model are in good agreement with the experimental data.
{"title":"The sample boundary effect in the low-frequency measurements of the elastic moduli of rocks","authors":"W. Tan, V. Mikhaltsevitch, M. Lebedev, S. Glubokovskikh, B. Gurevich","doi":"10.1080/22020586.2019.12073061","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073061","url":null,"abstract":"Summary In this study we examine the effect of the boundary conditions on the laboratory measurements of the elastic properties of a fluid-saturated sedimentary rock at low frequencies. In laboratory experiments associated with studying fluid effects on elastic properties of a porous rock sample, the tested sample cannot be completely sealed due to the presence of the fluid lines connected to its pore space. These lines form a pore-fluid storage which can affect the results of the elastic moduli measurements of fluid-saturated rocks. We developed a modified version of the Gassmann model which can estimate the bulk moduli of fully saturated rocks in dependence on the capacity of the pore-fluid storage. Here, we compare the predictions of the modified Gassmann model with the moduli measured on an n-decane-saturated limestone sample with the volume of the pore-fluid storage changing from 2 ml to 260 ml. The experimental results were obtained using a low-frequency apparatus based on the forced-oscillation method at a frequency of 0.1 Hz. We demonstrate that the predictions of the modified Gassmann model are in good agreement with the experimental data.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"7 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":"87900734","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: 10.1080/22020586.2019.12073057
J. Slade
Summary The challenges in drilling a high pressure and high temperature (HPHT) well are unique to every opportunity. The key to successfully drilling an HPHT well is to utilise the appropriate people, technology and design at the appropriate time. To do this it is critical to know the questions that need solving. Knowing and answering these questions cannot be effectively achieved without accessing subject matter experts in several disciplines including drilling, petrophysics and data acquisition and integrating into a coherent plan.
{"title":"What you need to know to drill a high pressure, high temperature well","authors":"J. Slade","doi":"10.1080/22020586.2019.12073057","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073057","url":null,"abstract":"Summary The challenges in drilling a high pressure and high temperature (HPHT) well are unique to every opportunity. The key to successfully drilling an HPHT well is to utilise the appropriate people, technology and design at the appropriate time. To do this it is critical to know the questions that need solving. Knowing and answering these questions cannot be effectively achieved without accessing subject matter experts in several disciplines including drilling, petrophysics and data acquisition and integrating into a coherent plan.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"1 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":"88178751","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: 10.1080/22020586.2019.12073168
M. Hutchens
Summary The Geological Survey of South Australia (GSSA) designed the Gawler Craton Airborne Survey (GCAS) to provide high resolution magnetic, gamma-ray and elevation data covering the northern portion of the Gawler Craton. In total, 1.66 million line km were planned over an area of 295,000 km2, covering approximately 30% of the state of South Australia. The survey design of 200 m spaced lines at a ground clearance of 60 m can be compared with the design of existing regional surveys which generally employed 400 m line spacing and a ground clearance of 80 m. The new survey design results in ~2 x the data coverage and ~25% closer to the ground when compared to previous standards for regional surveys in South Australia. Due to the enormous scale of the survey, the data were acquired using four contractors who employed ten systems to fly the sixteen blocks. To standardise the data from the multitude of systems, Geoscience Australia (GA) employed a comprehensive set of technical specifications. As part of these specifications the contractors were required to fly each of the ten systems over a series of test lines termed the “Whyalla Test Lines” (Whyalla). The final GCAS data provide truly impressive high resolution regional scale products. These will allow more detailed geological interpretation of the prospective Gawler Craton. A laser altimeter was added to the list of required survey equipment. Deficiencies in the technical specifications relating to laser altimeters were identified. Standards and procedures specific to laser characteristics will need to be considered on future surveys. Analyses show that weaknesses in current standards and procedures are still evident. The weaknesses identified allow room for improvements to be made for future surveys. Gamma-ray processing results raised the most serious concerns, with repeatability not achieved. Changes to standard procedures may need to be considered.
{"title":"Learnings from the Gawler Craton airborne survey quality control","authors":"M. Hutchens","doi":"10.1080/22020586.2019.12073168","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073168","url":null,"abstract":"Summary The Geological Survey of South Australia (GSSA) designed the Gawler Craton Airborne Survey (GCAS) to provide high resolution magnetic, gamma-ray and elevation data covering the northern portion of the Gawler Craton. In total, 1.66 million line km were planned over an area of 295,000 km2, covering approximately 30% of the state of South Australia. The survey design of 200 m spaced lines at a ground clearance of 60 m can be compared with the design of existing regional surveys which generally employed 400 m line spacing and a ground clearance of 80 m. The new survey design results in ~2 x the data coverage and ~25% closer to the ground when compared to previous standards for regional surveys in South Australia. Due to the enormous scale of the survey, the data were acquired using four contractors who employed ten systems to fly the sixteen blocks. To standardise the data from the multitude of systems, Geoscience Australia (GA) employed a comprehensive set of technical specifications. As part of these specifications the contractors were required to fly each of the ten systems over a series of test lines termed the “Whyalla Test Lines” (Whyalla). The final GCAS data provide truly impressive high resolution regional scale products. These will allow more detailed geological interpretation of the prospective Gawler Craton. A laser altimeter was added to the list of required survey equipment. Deficiencies in the technical specifications relating to laser altimeters were identified. Standards and procedures specific to laser characteristics will need to be considered on future surveys. Analyses show that weaknesses in current standards and procedures are still evident. The weaknesses identified allow room for improvements to be made for future surveys. Gamma-ray processing results raised the most serious concerns, with repeatability not achieved. Changes to standard procedures may need to be considered.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"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":"87684500","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: 10.1080/22020586.2019.12073137
S. Özaydın, K. Selway
Summary The magnetotelluric method is the most sensitive geophysical tool in detecting the hydration state of the mantle. Therefore, improved interpretations of electrical conductivity distribution within the Earth is a key measure that has to be taken in order to have a better grasp on lithopsheric-scale geodynamic concepts and the nature of mineralising agents. Progress towards this goal requires detailed comparisons between MT models and xenolith data in order to understand the controls on mantle electrical conductivity. In this study, new magnetotelluric models from southern Africa were utilised to constrain the composition and hydrogen content by comparing forward models based on the experimental studies made on mantle minerals at high P-T conditions. Many relations between the experimental parameters and information from xenolith data were tested to improve the capabilities of magnetotellurics as an exploration tool in the lithospheric mantle of cratons.
{"title":"Utilising 3-D magnetotelluric models of southern African mantle to constrain hydrogen content and compositional variations.","authors":"S. Özaydın, K. Selway","doi":"10.1080/22020586.2019.12073137","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073137","url":null,"abstract":"Summary The magnetotelluric method is the most sensitive geophysical tool in detecting the hydration state of the mantle. Therefore, improved interpretations of electrical conductivity distribution within the Earth is a key measure that has to be taken in order to have a better grasp on lithopsheric-scale geodynamic concepts and the nature of mineralising agents. Progress towards this goal requires detailed comparisons between MT models and xenolith data in order to understand the controls on mantle electrical conductivity. In this study, new magnetotelluric models from southern Africa were utilised to constrain the composition and hydrogen content by comparing forward models based on the experimental studies made on mantle minerals at high P-T conditions. Many relations between the experimental parameters and information from xenolith data were tested to improve the capabilities of magnetotellurics as an exploration tool in the lithospheric mantle of cratons.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"34 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":"82444564","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: 10.1080/22020586.2019.12072960
Daniel Eremenco, R. Mortimer, Edna Mead
Summary The Carlow Castle deposit is located 40 kilometres east of Karratha, Western Australia. The deposit is shear hosted in the Ruth Well Mafic Formation, part of the Roebourne Group. It is interspersed with metagabbro intrusions and brecciated chert cataclastites. Carlow Castle contains Au, Cu and Co mineralisation. Data from a Sub-Audio Magnetic (SAM) survey was acquired in both galvanic and inductive configurations to map structural responses over known mineralisation. On-time Magnetometric Conductivity (MMC), Total Magnetic Intensity (TMI) and Off-time Galvanic Source Electromagnetic (GSEM) data were extracted from the galvanic dipole configuration. Off-time Inductive Source Electromagnetic (ISEM) data were extracted from the loop source configuration. MMC data were combined, modelled and interpreted to rank structural targets around existing Au and Cu mineralisation. This was used in conjunction with Co soil geochemistry as a vectoring tool for further cobalt mineralisation. The MMC data was successful in increasing level of detail over the project. ISEM and GSEM were also compared with previously highlighted VTEM anomalism. Five high and seven medium priority targets were identified for follow up with further drilling.
Carlow Castle矿床位于西澳大利亚州Karratha以东40公里处。该矿床位于Roebourne Group的Ruth Well Mafic组中。分布有变长岩侵入体和角砾岩碎裂岩。卡洛城堡含金、铜和钴矿化。从亚音频磁(SAM)调查中获得了电流和感应配置的数据，以绘制已知矿化的结构响应图。实时磁导率(MMC)、总磁强度(TMI)和非实时电源电磁(GSEM)数据从电偶极子结构中提取。断开时感应源电磁(ISEM)数据从环路源配置中提取。对MMC数据进行组合、建模和解释，以对现有Au和Cu矿化周围的结构目标进行排序。这与Co土壤地球化学结合使用，作为进一步钴矿化的矢量工具。MMC数据成功地提高了项目的详细程度。ISEM和GSEM还与先前突出的VTEM异常进行了比较。确定了5个高优先目标和7个中等优先目标，以便进一步钻探。
{"title":"Delineating cobalt targets from a galvanic and inductive source Sub-Audio Magnetics (SAM) at the Carlow Castle project, Western Australia","authors":"Daniel Eremenco, R. Mortimer, Edna Mead","doi":"10.1080/22020586.2019.12072960","DOIUrl":"https://doi.org/10.1080/22020586.2019.12072960","url":null,"abstract":"Summary The Carlow Castle deposit is located 40 kilometres east of Karratha, Western Australia. The deposit is shear hosted in the Ruth Well Mafic Formation, part of the Roebourne Group. It is interspersed with metagabbro intrusions and brecciated chert cataclastites. Carlow Castle contains Au, Cu and Co mineralisation. Data from a Sub-Audio Magnetic (SAM) survey was acquired in both galvanic and inductive configurations to map structural responses over known mineralisation. On-time Magnetometric Conductivity (MMC), Total Magnetic Intensity (TMI) and Off-time Galvanic Source Electromagnetic (GSEM) data were extracted from the galvanic dipole configuration. Off-time Inductive Source Electromagnetic (ISEM) data were extracted from the loop source configuration. MMC data were combined, modelled and interpreted to rank structural targets around existing Au and Cu mineralisation. This was used in conjunction with Co soil geochemistry as a vectoring tool for further cobalt mineralisation. The MMC data was successful in increasing level of detail over the project. ISEM and GSEM were also compared with previously highlighted VTEM anomalism. Five high and seven medium priority targets were identified for follow up with further drilling.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"42 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":"81169053","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: 10.1080/22020586.2019.12073122
R. Woods, T. Bothwell, B. Birt, Tim Hopper, S. Higginson
Summary Bringing a new well on-line is an expensive proposition and the need to ensure optimal performance is critical. Saturation and contamination of the drilling fluid with fines and subsequent invasion of the formation has historically resulted in hundreds of hours per well of invisible lost time during the clean-up phase of the well. New technologies, workflows and methods that can reduce costs/turnaround on projects were conducted on a large multi-well project in Perth, Western Australia, to maximise well efficiencies. Data from multiple sources were used to optimise and validate well clean-up operations with the aim to maximising production. This case study uses integration of well testing transient pressure data, Borehole Magnetic Resonance (BMR) derived transmissivity and flow logging to quantify success of clean-up/development of water wells, to reduce cost and optimise productivity. This case study demonstrates the successful implementation of an integrated approach to well clean-up using several scales of permeability data from core to wireline BMR to well test. This case study demonstrates that, in this particular setting, the use of the presented methodology was cost effective, yielded positive confirmation of asset delivery, and has led to a 90% reduction in clean-up associated time.
{"title":"A practical approach used to plan and execute, quantify and qualify an effective well clean-up strategy","authors":"R. Woods, T. Bothwell, B. Birt, Tim Hopper, S. Higginson","doi":"10.1080/22020586.2019.12073122","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073122","url":null,"abstract":"Summary Bringing a new well on-line is an expensive proposition and the need to ensure optimal performance is critical. Saturation and contamination of the drilling fluid with fines and subsequent invasion of the formation has historically resulted in hundreds of hours per well of invisible lost time during the clean-up phase of the well. New technologies, workflows and methods that can reduce costs/turnaround on projects were conducted on a large multi-well project in Perth, Western Australia, to maximise well efficiencies. Data from multiple sources were used to optimise and validate well clean-up operations with the aim to maximising production. This case study uses integration of well testing transient pressure data, Borehole Magnetic Resonance (BMR) derived transmissivity and flow logging to quantify success of clean-up/development of water wells, to reduce cost and optimise productivity. This case study demonstrates the successful implementation of an integrated approach to well clean-up using several scales of permeability data from core to wireline BMR to well test. This case study demonstrates that, in this particular setting, the use of the presented methodology was cost effective, yielded positive confirmation of asset delivery, and has led to a 90% reduction in clean-up associated time.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"7 6","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":"91441099","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: 10.1080/22020586.2019.12073001
David. Pratt, K. Blair McKenzie, A. White
Summary Most regional scale magnetic maps are dominated by the magnetic characteristics of steeply dipping basement units truncated by an unconformity surface. It is easy to demonstrate that 80 to 90% of each total field magnetic anomaly is contributed by this intersecting surface. We approach this problem by mapping the boundaries between contrasting magnetic units along each line in the magnetic survey using the full precision of the line data and 3D information from the magnetic gradient tensor. Additionally, we derive the azimuth of each boundary, depth to the unconformity and magnetic properties of the anomalous units. The segments are overlain on any image such as existing geological maps, satellite imagery, gravity or magnetic imagery to provide a new geological interpretation concept. This method provides a new way to interpret new and old magnetic surveys. Eigenvector analysis of the magnetic tensor and normalised source strength (NSS) are combined with an artificial intelligence (AI) approach to estimate the basement properties. The method is applied to full tensor magnetic survey data or a grid of the total magnetic intensity data is processed using FFT transformations to derive the magnetic gradient tensor. These data are used as input to the pre-trained AI process for calculation of depth, width, azimuth, magnetic susceptibility and magnetisation direction. The rock properties and depth information can be used for 3D visualisation of the unconformity and 2D mapping of the magnetic lithology of the unconformity surface.
{"title":"An AI approach to automated magnetic formation mapping beneath cover","authors":"David. Pratt, K. Blair McKenzie, A. White","doi":"10.1080/22020586.2019.12073001","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073001","url":null,"abstract":"Summary Most regional scale magnetic maps are dominated by the magnetic characteristics of steeply dipping basement units truncated by an unconformity surface. It is easy to demonstrate that 80 to 90% of each total field magnetic anomaly is contributed by this intersecting surface. We approach this problem by mapping the boundaries between contrasting magnetic units along each line in the magnetic survey using the full precision of the line data and 3D information from the magnetic gradient tensor. Additionally, we derive the azimuth of each boundary, depth to the unconformity and magnetic properties of the anomalous units. The segments are overlain on any image such as existing geological maps, satellite imagery, gravity or magnetic imagery to provide a new geological interpretation concept. This method provides a new way to interpret new and old magnetic surveys. Eigenvector analysis of the magnetic tensor and normalised source strength (NSS) are combined with an artificial intelligence (AI) approach to estimate the basement properties. The method is applied to full tensor magnetic survey data or a grid of the total magnetic intensity data is processed using FFT transformations to derive the magnetic gradient tensor. These data are used as input to the pre-trained AI process for calculation of depth, width, azimuth, magnetic susceptibility and magnetisation direction. The rock properties and depth information can be used for 3D visualisation of the unconformity and 2D mapping of the magnetic lithology of the unconformity surface.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"1 1","pages":"1 - 9"},"PeriodicalIF":0.0,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77168121","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: 10.1080/22020586.2019.12073213
M. Hatch, O. Batelaan, E. Banks, S. Douangsavanh
Summary Lao PDR is a poorly developed country, with a large rural population which relies heavily on agricultural production. The Vientiane Plain is one of the most important and largest agricultural production areas with plans to expand the area under irrigated agriculture. Historically, surface water has been used because of its relative abundance with limited consideration to use groundwater. Where groundwater development has occurred for irrigation there is little or no management, and what little there is, is based on very poor hydrogeological information. A lack of knowledge of where to site wells has led to well failure and poor water quality. This project was initiated through the Society of Exploration Geophysics - Geoscientists without Borders Program to: teach local scientists, both university-based, as well as from the government, about the latest in hydrogeophysical technology and how it can be used in the Lao PDR. Specifically we looked to apply hydrogeophysical techniques to characterise the hydrogeology of the Vientiane Plain; to evaluate the quantity and quality of groundwater that may be available; and to enhance the scientific knowledge of local resource users. Two field trips were undertaken in 2018 and 2019 to conduct workshops and training with in-country government department officials and students from the Laos University. Results from the project identified and mapped highly conductive zones related to saline geological features which would be unsuitable locations for well locations for groundwater irrigation.
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