Original motivation of this study was to understand important structures with a proven geothermal signature associated with high temperatures in the shallower basin and high flow rates in the aquifers. Anomalous temperatures are recorded around the Beagle Ridge and significant flow rates observed near the Urella Fault, factors important to unconventional geothermal prospects. The focus of this study was therefore a detailed geophysical investigation of several Geothermal Exploration Permits (GEPs) in the North Perth Basin. Two Magnetotelluric (MT) surveys are conducted over target areas in the North Perth Basin and adjoining tectonic domains to provide information about the electrical conductivity regime of the basin and western margin of the Yilgarn C
2 d seismic refraction tomography investigation of a sewage treatment siteAlexander Decker
This study used seismic refraction tomography to investigate subsurface layers at a sewage treatment site in Nigeria. Five seismic profiles were collected and analyzed. The results show three layers: an upper undifferentiated overburden layer with velocities from 891-1421 m/s and thicknesses ranging from 18m in the north to 55m in the south; a partially weathered middle layer with velocities from 3010-5129 m/s; and a fresh granite basement layer below with velocities from 5704-7762 m/s. One profile revealed a fracture zone in the basement at 60m depth that could allow sewage to contaminate groundwater if the lagoons are not lined. The study characterized the subsurface
The document discusses a geo-electrical imaging survey conducted in Edo State, Nigeria to characterize the subsurface geology for environmental and engineering studies. Resistivity data was collected along four lines using the Wenner array and inverted to produce 2D resistivity images. The images indicate resistivity increases with depth and identify three main layers - alluvium deposits from 0-20m underlain by laterite to 20m thick, underlain by sandstone and shale. Areas over 3500 ohm-m represent bedrock of gravel and granite, showing the area is suitable for construction. The study found no evidence of contamination or faults, but low conductivity suggests limited aquifer potential for water supply.
Ground geophysical surveys use magnetic, electrical, and gravitational measurements to map subsurface rock properties. Magnetics surveys measure the earth's magnetic field and magnetic responses from rocks to map geology and locate magnetic ore bodies. Resistivity and induced polarization (IP) surveys measure electrical properties to detect disseminated sulfides and map stratigraphy. Time-domain electromagnetics (TDEM) uses electromagnetic induction to identify conductive features like ores, groundwater, and permafrost. Geophysical methods provide non-invasive exploration techniques but their results require careful processing and interpretation.
Geophysical studies on Dahab area, South Sinai. Egyptosamaabdelraouf1
The document summarizes geophysical studies conducted on the Dahab area in southern Sinai, Egypt. Magnetic, geoelectric, and hydrological studies were performed to determine the sedimentary cover, subsurface structures, and groundwater conditions. Magnetic data showed variations in sediment thickness, with thicker deposits in northwestern grabens. Geoelectric data revealed four subsurface layers and the depth to water-bearing zones. The main aquifer is Quaternary sands and gravels, with thickness ranging from 5-60 meters.
This document proposes research to determine the groundwater table in Hawa Galan catchment, Ethiopia using vertical electrical sounding (VES) methods. The study area has a population of over 123,000 people relying on groundwater sources like hand dug wells as there are no permanent surface water sources. Previous studies in the region focused on geology and igneous petrology but not groundwater. This research will involve collecting VES data along profiles and analyzing the results to map subsurface resistivity and identify potential high-yield aquifers and drilling locations to address the need for sustainable groundwater resources in the community. A detailed work plan and budget are provided outlining field work, data analysis, and reporting over an anticipated one year
1) The document summarizes the geological and structural interpretation of Ado-Ekiti Southwest and its adjoining areas in Nigeria using aeromagnetic data.
2) Aeromagnetic data was collected and processed using various techniques including filtering, inversion, and enhancement to generate a model of the subsurface basement topography and interpret the geology.
3) Maps produced from the processed aeromagnetic data revealed the basement topography, structural lineaments and their orientations, and estimated depths to magnetic sources in the study area.
Welcome to International Journal of Engineering Research and Development (IJERD)IJERD Editor
1) Vertical electrical sounding using Schlumberger array was conducted at 40 stations to determine subsurface layers and depth to bedrock at the Centre for Energy Research and Training in Zaria, Nigeria.
2) Resistivity values and thickness were derived for three predominant layers - topsoil (2-738 ohm-m thickening 1-3.9m), weathered basement (32-1735 ohm-m thickening 0.52-23m), and fresh basement bedrock (100-6036 ohm-m).
3) Results identified areas suitable for structures and boreholes, and recommended depth of sewage systems to avoid groundwater contamination based on the subsurface resistivity and thickness parameters.
The document discusses geophysical methods for geothermal exploration. It provides an overview of basic geophysics concepts and signatures of a geothermal system that can be identified using geophysics, including the heat source, reservoir, cap rock and recharge system. Standard geophysical techniques for geothermal exploration are mentioned, such as magnetotellurics, time domain electromagnetics, and gravity surveys. Examples of geophysical surveys and their results in identifying geothermal reservoirs in Indonesia are presented.
2 d seismic refraction tomography investigation of a sewage treatment siteAlexander Decker
This study used seismic refraction tomography to investigate subsurface layers at a sewage treatment site in Nigeria. Five seismic profiles were collected and analyzed. The results show three layers: an upper undifferentiated overburden layer with velocities from 891-1421 m/s and thicknesses ranging from 18m in the north to 55m in the south; a partially weathered middle layer with velocities from 3010-5129 m/s; and a fresh granite basement layer below with velocities from 5704-7762 m/s. One profile revealed a fracture zone in the basement at 60m depth that could allow sewage to contaminate groundwater if the lagoons are not lined. The study characterized the subsurface
The document discusses a geo-electrical imaging survey conducted in Edo State, Nigeria to characterize the subsurface geology for environmental and engineering studies. Resistivity data was collected along four lines using the Wenner array and inverted to produce 2D resistivity images. The images indicate resistivity increases with depth and identify three main layers - alluvium deposits from 0-20m underlain by laterite to 20m thick, underlain by sandstone and shale. Areas over 3500 ohm-m represent bedrock of gravel and granite, showing the area is suitable for construction. The study found no evidence of contamination or faults, but low conductivity suggests limited aquifer potential for water supply.
Ground geophysical surveys use magnetic, electrical, and gravitational measurements to map subsurface rock properties. Magnetics surveys measure the earth's magnetic field and magnetic responses from rocks to map geology and locate magnetic ore bodies. Resistivity and induced polarization (IP) surveys measure electrical properties to detect disseminated sulfides and map stratigraphy. Time-domain electromagnetics (TDEM) uses electromagnetic induction to identify conductive features like ores, groundwater, and permafrost. Geophysical methods provide non-invasive exploration techniques but their results require careful processing and interpretation.
Geophysical studies on Dahab area, South Sinai. Egyptosamaabdelraouf1
The document summarizes geophysical studies conducted on the Dahab area in southern Sinai, Egypt. Magnetic, geoelectric, and hydrological studies were performed to determine the sedimentary cover, subsurface structures, and groundwater conditions. Magnetic data showed variations in sediment thickness, with thicker deposits in northwestern grabens. Geoelectric data revealed four subsurface layers and the depth to water-bearing zones. The main aquifer is Quaternary sands and gravels, with thickness ranging from 5-60 meters.
This document proposes research to determine the groundwater table in Hawa Galan catchment, Ethiopia using vertical electrical sounding (VES) methods. The study area has a population of over 123,000 people relying on groundwater sources like hand dug wells as there are no permanent surface water sources. Previous studies in the region focused on geology and igneous petrology but not groundwater. This research will involve collecting VES data along profiles and analyzing the results to map subsurface resistivity and identify potential high-yield aquifers and drilling locations to address the need for sustainable groundwater resources in the community. A detailed work plan and budget are provided outlining field work, data analysis, and reporting over an anticipated one year
1) The document summarizes the geological and structural interpretation of Ado-Ekiti Southwest and its adjoining areas in Nigeria using aeromagnetic data.
2) Aeromagnetic data was collected and processed using various techniques including filtering, inversion, and enhancement to generate a model of the subsurface basement topography and interpret the geology.
3) Maps produced from the processed aeromagnetic data revealed the basement topography, structural lineaments and their orientations, and estimated depths to magnetic sources in the study area.
Welcome to International Journal of Engineering Research and Development (IJERD)IJERD Editor
1) Vertical electrical sounding using Schlumberger array was conducted at 40 stations to determine subsurface layers and depth to bedrock at the Centre for Energy Research and Training in Zaria, Nigeria.
2) Resistivity values and thickness were derived for three predominant layers - topsoil (2-738 ohm-m thickening 1-3.9m), weathered basement (32-1735 ohm-m thickening 0.52-23m), and fresh basement bedrock (100-6036 ohm-m).
3) Results identified areas suitable for structures and boreholes, and recommended depth of sewage systems to avoid groundwater contamination based on the subsurface resistivity and thickness parameters.
The document discusses geophysical methods for geothermal exploration. It provides an overview of basic geophysics concepts and signatures of a geothermal system that can be identified using geophysics, including the heat source, reservoir, cap rock and recharge system. Standard geophysical techniques for geothermal exploration are mentioned, such as magnetotellurics, time domain electromagnetics, and gravity surveys. Examples of geophysical surveys and their results in identifying geothermal reservoirs in Indonesia are presented.
Application of vertical electrical sounding and horizontal profiling methods ...Alexander Decker
The document describes a study that used vertical electrical sounding (VES) and horizontal profiling (EP) methods to characterize the subsurface stratification at a proposed dam site on the Segen River in Tigray, Northern Ethiopia. Ten VES points were collected along two profiles, and two EP surveys were conducted along the profiles. The VES and EP results identified weak zones up to 20-30 meters deep at several locations along the profiles, indicating the need for further core drilling investigations to properly evaluate the subsurface conditions for dam construction.
Geoelectrical methods for investigating mine dumpsoilandgas24
This document summarizes the use of geoelectrical methods like direct current resistivity, electromagnetic induction, induced polarization, and ground-penetrating radar to study mine dumps. The results of these methods reflect the lithology, pore water saturation, and dissolved solids in the pore water. Conductivity maps using these methods can help indicate places where acid is being generated if the pore water pH is less than 5. Induced polarization measurements are also useful for distinguishing sulfide mineral concentrations in mine dumps.
Evaluation of sub-soil geo-electric properties in a proposed power sub-statio...IJERA Editor
This document summarizes the results of an electrical resistivity survey conducted at a proposed power substation site in Rivers State, Nigeria. The survey found that the subsurface is characterized by two main geo-electric layers: an upper layer of lower resistivity lateritic to silty sands extending to depths of 2-3 meters, and a lower layer of higher resistivity fine to coarse sands and gravels forming the major aquifers in the area. Analysis showed that the subsoil falls within the non-corrosive class, indicating that subsurface electrical installations would pose minimal hazards with basic precautions.
Nuclear Magnetic Ressonance - Water content assessment in glacier ice and ben...Fundació Marcel Chevalier
Glaciers are widely spread on polar and sub-polar regions but also on middle latitude mountains, where cold-dry type glaciers, polythermal glaciers and temperate-wet glaciers are respectively present. Assess their water content is capital to understand the ice dynamics and how is related with the climate change.
1) High-resolution seismic methods were used to map the detailed structure and thickness of coal seams in the Domeniko coal basin in Greece. 2) Reflection events attributed to coal layers could be interpreted from depths of 30-150 meters on processed seismic sections. 3) Several low-throw faults were also interpreted from the sections. 4) When combined with drillhole data using geostatistical methods, the seismic survey results clearly revealed the 3D model of the coal basin.
1) A hydrogeophysical survey was conducted on an earthen dam to investigate factors contributing to its long-term successful operation without apparent seepage issues. 2) Geophysical methods including seismic refraction, self-potential, and electrical resistivity tomography were used to map the subsurface hydrostratigraphy and groundwater flow patterns. 3) The data indicated a preferential flow pathway beneath the dam, corresponding to a sandy-gravel layer that connects the reservoir to a downstream seepage zone. This layer may explain the dam's success by providing a controlled pathway for seepage.
1) The document analyzes measurements from the DMSP satellite constellation to calculate and map Poynting flux in Earth's ionosphere and auroral boundary regions.
2) Preliminary results show concentrations of earthward flux on the poleward edge of the auroral boundary and that polar cap flux is located dawnward of noon and is consistently present, implying internal reconnection occurs regularly.
3) The study produced a useful tool for further statistical investigation of Poynting flux in this region and observed only a small difference in energy deposition between the auroral zone and polar cap, contrary to previous expectations.
Engineering geophysical study of unconsolidated top soil using shallow seismi...Alexander Decker
1) An integrated geophysical study using seismic refraction and electrical resistivity techniques was conducted to image the shallow subsurface at the University of Peshawar, Pakistan.
2) Analysis of seismic refraction data along profile AB revealed a two-layer subsurface structure, with a top layer of loose soil 0-4 meters thick having P-wave velocities of 223m/sec underlain by a layer with a velocity of 316 m/sec.
3) Electrical resistivity surveys along two profiles validated the two-layer model, detecting a top soil layer 1.1-1.3 meters thick with resistivities of 38-52 ohm-meters underlain by a more conductive clay-rich layer with resist
This document discusses various geophysical methods used to study the subsurface of the earth, including gravity, magnetic, electrical, seismic, radiometric, and geothermal methods. It explains the basic principles of each method, what physical properties are measured, how variations in those properties can provide information about subsurface features like rock types and structures. Applications are mentioned like mineral and groundwater exploration. Both advantages and limitations of each geophysical method are summarized.
1. Controlled-source electromagnetic (CSEM) and magnetotelluric profiling (MT) are two key geophysical methods that use electromagnetic waves for offshore oil exploration. CSEM works by transmitting low frequency EM waves from a source and analyzing the resistivity contrasts in the subsurface based on readings from receiver arrays. MT uses a broader range of frequencies over time to create a smooth profile of the subsurface that accounts for anisotropic properties.
2. While CSEM is better for exploring a large area due to its deep penetration, MT provides more accurate detail on the orientation and location of reservoirs due to its consideration of anisotropy. Together, the methods can complement each other in offshore oil exploration.
Research Inventy : International Journal of Engineering and Scienceinventy
Research Inventy : International Journal of Engineering and Science is published by the group of young academic and industrial researchers with 12 Issues per year. It is an online as well as print version open access journal that provides rapid publication (monthly) of articles in all areas of the subject such as: civil, mechanical, chemical, electronic and computer engineering as well as production and information technology. The Journal welcomes the submission of manuscripts that meet the general criteria of significance and scientific excellence. Papers will be published by rapid process within 20 days after acceptance and peer review process takes only 7 days. All articles published in Research Inventy will be peer-reviewed.
2 d electrical resistivity tomography (ert) survey using the multi electrode ...Alexander Decker
1) 2D electrical resistivity tomography (ERT) surveys were conducted along six radial profiles at the Bosumtwi impact crater in Ghana using a modified multi-electrode gradient array.
2) The cable take-outs of the resistivity imaging system were modified from 2m to 5m spacing, allowing investigation of the subsurface to depths of around 75m.
3) The ERT models identified three subsurface formations - low resistivity lake sediments, moderately resistive impact breccias, and highly resistive basement metamorphic rocks.
The document summarizes an electrical resistivity investigation conducted around Shika, Kaduna State, Nigeria to map subsurface geological strata and determine depth to bedrock. Vertical electrical soundings were performed at 18 locations. The data revealed 4 geological layers - topsoil, weathered basement, partly weathered basement, and fresh basement. Resistivity and thickness values varied across layers. Locations with thicker weathered zones indicate higher potential for groundwater. The study provides information useful for engineering, groundwater, and waste management.
This document summarizes an electrical resistivity study conducted around Shika, Kaduna State, Nigeria to map subsurface geology. Vertical electrical sounding was performed at 18 locations using an ABEM terrameter. Resistivity values were interpreted to identify topsoil, weathered basement, fractured basement, and fresh basement layers. Topsoil thickness ranged from 1.06-4.14m with resistivity 60-373 ohm-m. Weathered basement thickness was 1.77-33.04m with resistivity 70-708 ohm-m. Fractured basement extended 12.9-26.3m deep with resistivity 318-834 ohm-m. Fresh basement had resistivity over 1161
This document provides an overview of geophysical methods used for site investigation and laboratory measurements. It discusses various methods including electrical resistivity, seismic methods, electromagnetic conductivity, gravity geophysical methods, and geothermal methods. For each method, it describes how the technique works and how tests are conducted to collect subsurface data on properties like density, conductivity, and elastic moduli. The document aims to explain different geophysical techniques that can be employed to characterize subsurface conditions.
The conductivity structure of the Gediz Graben geothermal area extracted from...Erhan Erdogan
•Interpretation of MT data on extensional tectonic geothermal areas is examined using synthetic and field data.
•Three dimensional conductivity model of Gediz Graben geothermal area is created using seismic sections and used for producing synthetic magnetotelluric data.
•The resolving power of the two and three-dimensional inversion methods is discussed.
•Three dimensional inversion is applied to the field data and presented with real borehole results.
•New geothermal source was discovered using the MT data and three-dimensional inversion results.
Subsurface Determination Of Cavities In Limestone Rock Area By Geoelectric Me...IJERA Editor
Two Dimensional of geoelectric method can be used to find out the conductive formation in the earth surface. The purpose of this research is to give the description about the geological subsurface formation, that the high resistivity value is indicate the potential area of cave and void in the limestone rocks. The dipole dipolegeoelectric method is used in this research with the path of lines is 250 m with 10 m electrode spacing. The total lines is 7 and the azimuth is from east to west. Resistivity method is started with inject the electrical current into the earth by current electrode, then potential difference will arise and measured by potential electrode. Variation value of resistance for each layer rock can calculated by divided potential defference with current value. The existence of the cavity is known by the resistivity value is more than 2500 ohm-m, while the cracks have a resistivity of 1500 to 2500 ohm-m.
The document discusses electrical resistivity methods for groundwater exploration. It begins by explaining how resistivity surveying works, noting that it investigates variations in electrical resistance in the subsurface using electrodes connected to the ground. It then provides an overview of resistivity surveying, indicating it is useful because resistivity/conductivity of earth materials can vary significantly. The document outlines different electrical methods including DC resistivity, induced polarization, self potential, electromagnetic, and magnetotelluric techniques. It then discusses key concepts such as the difference between active and passive methods, advantages and disadvantages of different techniques, and typical resistivity ranges for common earth materials.
This document discusses seismic reflection methods and their application to shallow subsurface exploration problems. It provides an overview of seismic reflection fundamentals, including how reflections are generated at acoustic impedance contrasts and how common depth point (CDP) processing works to enhance reflection signals. The document also discusses data acquisition parameters and challenges of shallow seismic reflection, and gives examples of applications such as mapping geologic layers, faults, and cavities.
Electrical Resistivity Survey Forground Water At Eye Zheba Village, Off Bida ...iosrjce
The paper titled “Electrical Resistivity survey for ground water” at EL-HALAL Farms, covered an
area of about 10km2
, located at Eye Zheba village along Minna-Bida Road, located on latitude 60
.001
and 6
0
7
1
West and longitude 90
3
1
and 9.101 North. As a result of water problem in Bida and its environs, the people living
in this environment suffered a lot due to lack of portable drinking water and water for domestic use. A
Geophysical survey carried out, employed the schlumberger Array method in which current were sent beneath
the earth surfaces, this was done at various points and the data collected. The area revealed three lithological
formations in some places while in some place five. With the lowest resistivty found to be 6.85 Ωm and the
highest resistivity was 12,774.46 Ωm. The lithotogical formation includes the sandstones, clayey sandstones,
sandy clay and ferruginised sandstone. Since this is a sedimentary area drilling is expected to be deep down to a
depth of about 70-75m
PPT Writing A Narrative Essay PowerPoint Presentation Free ToAngela Shin
The document discusses the process for requesting an assignment to be written through the website HelpWriting.net. It outlines 5 steps: 1) Create an account with valid email and password. 2) Complete a 10-minute order form providing instructions, sources, and deadline. 3) Review bids from writers and choose one based on qualifications. 4) Receive the paper and authorize payment if pleased. 5) Request revisions until fully satisfied, with a refund option for plagiarized work. The process aims to ensure high-quality, original content that meets the customer's needs.
The Archives The College Board Essays, Part 3 SamAngela Shin
The document discusses a 102-year-old time capsule that was discovered in 2017 while workers were taking down a monument in St. Louis. It would have been difficult for people in 1915 to decide what to include in a time capsule, but finding this capsule from that era provides insight into what life was like before modern technology. To capture life in the 2000s for future generations, the document suggests including representations of fashion, technology, and pop culture fads from that time in a new time capsule.
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Application of vertical electrical sounding and horizontal profiling methods ...Alexander Decker
The document describes a study that used vertical electrical sounding (VES) and horizontal profiling (EP) methods to characterize the subsurface stratification at a proposed dam site on the Segen River in Tigray, Northern Ethiopia. Ten VES points were collected along two profiles, and two EP surveys were conducted along the profiles. The VES and EP results identified weak zones up to 20-30 meters deep at several locations along the profiles, indicating the need for further core drilling investigations to properly evaluate the subsurface conditions for dam construction.
Geoelectrical methods for investigating mine dumpsoilandgas24
This document summarizes the use of geoelectrical methods like direct current resistivity, electromagnetic induction, induced polarization, and ground-penetrating radar to study mine dumps. The results of these methods reflect the lithology, pore water saturation, and dissolved solids in the pore water. Conductivity maps using these methods can help indicate places where acid is being generated if the pore water pH is less than 5. Induced polarization measurements are also useful for distinguishing sulfide mineral concentrations in mine dumps.
Evaluation of sub-soil geo-electric properties in a proposed power sub-statio...IJERA Editor
This document summarizes the results of an electrical resistivity survey conducted at a proposed power substation site in Rivers State, Nigeria. The survey found that the subsurface is characterized by two main geo-electric layers: an upper layer of lower resistivity lateritic to silty sands extending to depths of 2-3 meters, and a lower layer of higher resistivity fine to coarse sands and gravels forming the major aquifers in the area. Analysis showed that the subsoil falls within the non-corrosive class, indicating that subsurface electrical installations would pose minimal hazards with basic precautions.
Nuclear Magnetic Ressonance - Water content assessment in glacier ice and ben...Fundació Marcel Chevalier
Glaciers are widely spread on polar and sub-polar regions but also on middle latitude mountains, where cold-dry type glaciers, polythermal glaciers and temperate-wet glaciers are respectively present. Assess their water content is capital to understand the ice dynamics and how is related with the climate change.
1) High-resolution seismic methods were used to map the detailed structure and thickness of coal seams in the Domeniko coal basin in Greece. 2) Reflection events attributed to coal layers could be interpreted from depths of 30-150 meters on processed seismic sections. 3) Several low-throw faults were also interpreted from the sections. 4) When combined with drillhole data using geostatistical methods, the seismic survey results clearly revealed the 3D model of the coal basin.
1) A hydrogeophysical survey was conducted on an earthen dam to investigate factors contributing to its long-term successful operation without apparent seepage issues. 2) Geophysical methods including seismic refraction, self-potential, and electrical resistivity tomography were used to map the subsurface hydrostratigraphy and groundwater flow patterns. 3) The data indicated a preferential flow pathway beneath the dam, corresponding to a sandy-gravel layer that connects the reservoir to a downstream seepage zone. This layer may explain the dam's success by providing a controlled pathway for seepage.
1) The document analyzes measurements from the DMSP satellite constellation to calculate and map Poynting flux in Earth's ionosphere and auroral boundary regions.
2) Preliminary results show concentrations of earthward flux on the poleward edge of the auroral boundary and that polar cap flux is located dawnward of noon and is consistently present, implying internal reconnection occurs regularly.
3) The study produced a useful tool for further statistical investigation of Poynting flux in this region and observed only a small difference in energy deposition between the auroral zone and polar cap, contrary to previous expectations.
Engineering geophysical study of unconsolidated top soil using shallow seismi...Alexander Decker
1) An integrated geophysical study using seismic refraction and electrical resistivity techniques was conducted to image the shallow subsurface at the University of Peshawar, Pakistan.
2) Analysis of seismic refraction data along profile AB revealed a two-layer subsurface structure, with a top layer of loose soil 0-4 meters thick having P-wave velocities of 223m/sec underlain by a layer with a velocity of 316 m/sec.
3) Electrical resistivity surveys along two profiles validated the two-layer model, detecting a top soil layer 1.1-1.3 meters thick with resistivities of 38-52 ohm-meters underlain by a more conductive clay-rich layer with resist
This document discusses various geophysical methods used to study the subsurface of the earth, including gravity, magnetic, electrical, seismic, radiometric, and geothermal methods. It explains the basic principles of each method, what physical properties are measured, how variations in those properties can provide information about subsurface features like rock types and structures. Applications are mentioned like mineral and groundwater exploration. Both advantages and limitations of each geophysical method are summarized.
1. Controlled-source electromagnetic (CSEM) and magnetotelluric profiling (MT) are two key geophysical methods that use electromagnetic waves for offshore oil exploration. CSEM works by transmitting low frequency EM waves from a source and analyzing the resistivity contrasts in the subsurface based on readings from receiver arrays. MT uses a broader range of frequencies over time to create a smooth profile of the subsurface that accounts for anisotropic properties.
2. While CSEM is better for exploring a large area due to its deep penetration, MT provides more accurate detail on the orientation and location of reservoirs due to its consideration of anisotropy. Together, the methods can complement each other in offshore oil exploration.
Research Inventy : International Journal of Engineering and Scienceinventy
Research Inventy : International Journal of Engineering and Science is published by the group of young academic and industrial researchers with 12 Issues per year. It is an online as well as print version open access journal that provides rapid publication (monthly) of articles in all areas of the subject such as: civil, mechanical, chemical, electronic and computer engineering as well as production and information technology. The Journal welcomes the submission of manuscripts that meet the general criteria of significance and scientific excellence. Papers will be published by rapid process within 20 days after acceptance and peer review process takes only 7 days. All articles published in Research Inventy will be peer-reviewed.
2 d electrical resistivity tomography (ert) survey using the multi electrode ...Alexander Decker
1) 2D electrical resistivity tomography (ERT) surveys were conducted along six radial profiles at the Bosumtwi impact crater in Ghana using a modified multi-electrode gradient array.
2) The cable take-outs of the resistivity imaging system were modified from 2m to 5m spacing, allowing investigation of the subsurface to depths of around 75m.
3) The ERT models identified three subsurface formations - low resistivity lake sediments, moderately resistive impact breccias, and highly resistive basement metamorphic rocks.
The document summarizes an electrical resistivity investigation conducted around Shika, Kaduna State, Nigeria to map subsurface geological strata and determine depth to bedrock. Vertical electrical soundings were performed at 18 locations. The data revealed 4 geological layers - topsoil, weathered basement, partly weathered basement, and fresh basement. Resistivity and thickness values varied across layers. Locations with thicker weathered zones indicate higher potential for groundwater. The study provides information useful for engineering, groundwater, and waste management.
This document summarizes an electrical resistivity study conducted around Shika, Kaduna State, Nigeria to map subsurface geology. Vertical electrical sounding was performed at 18 locations using an ABEM terrameter. Resistivity values were interpreted to identify topsoil, weathered basement, fractured basement, and fresh basement layers. Topsoil thickness ranged from 1.06-4.14m with resistivity 60-373 ohm-m. Weathered basement thickness was 1.77-33.04m with resistivity 70-708 ohm-m. Fractured basement extended 12.9-26.3m deep with resistivity 318-834 ohm-m. Fresh basement had resistivity over 1161
This document provides an overview of geophysical methods used for site investigation and laboratory measurements. It discusses various methods including electrical resistivity, seismic methods, electromagnetic conductivity, gravity geophysical methods, and geothermal methods. For each method, it describes how the technique works and how tests are conducted to collect subsurface data on properties like density, conductivity, and elastic moduli. The document aims to explain different geophysical techniques that can be employed to characterize subsurface conditions.
The conductivity structure of the Gediz Graben geothermal area extracted from...Erhan Erdogan
•Interpretation of MT data on extensional tectonic geothermal areas is examined using synthetic and field data.
•Three dimensional conductivity model of Gediz Graben geothermal area is created using seismic sections and used for producing synthetic magnetotelluric data.
•The resolving power of the two and three-dimensional inversion methods is discussed.
•Three dimensional inversion is applied to the field data and presented with real borehole results.
•New geothermal source was discovered using the MT data and three-dimensional inversion results.
Subsurface Determination Of Cavities In Limestone Rock Area By Geoelectric Me...IJERA Editor
Two Dimensional of geoelectric method can be used to find out the conductive formation in the earth surface. The purpose of this research is to give the description about the geological subsurface formation, that the high resistivity value is indicate the potential area of cave and void in the limestone rocks. The dipole dipolegeoelectric method is used in this research with the path of lines is 250 m with 10 m electrode spacing. The total lines is 7 and the azimuth is from east to west. Resistivity method is started with inject the electrical current into the earth by current electrode, then potential difference will arise and measured by potential electrode. Variation value of resistance for each layer rock can calculated by divided potential defference with current value. The existence of the cavity is known by the resistivity value is more than 2500 ohm-m, while the cracks have a resistivity of 1500 to 2500 ohm-m.
The document discusses electrical resistivity methods for groundwater exploration. It begins by explaining how resistivity surveying works, noting that it investigates variations in electrical resistance in the subsurface using electrodes connected to the ground. It then provides an overview of resistivity surveying, indicating it is useful because resistivity/conductivity of earth materials can vary significantly. The document outlines different electrical methods including DC resistivity, induced polarization, self potential, electromagnetic, and magnetotelluric techniques. It then discusses key concepts such as the difference between active and passive methods, advantages and disadvantages of different techniques, and typical resistivity ranges for common earth materials.
This document discusses seismic reflection methods and their application to shallow subsurface exploration problems. It provides an overview of seismic reflection fundamentals, including how reflections are generated at acoustic impedance contrasts and how common depth point (CDP) processing works to enhance reflection signals. The document also discusses data acquisition parameters and challenges of shallow seismic reflection, and gives examples of applications such as mapping geologic layers, faults, and cavities.
Electrical Resistivity Survey Forground Water At Eye Zheba Village, Off Bida ...iosrjce
The paper titled “Electrical Resistivity survey for ground water” at EL-HALAL Farms, covered an
area of about 10km2
, located at Eye Zheba village along Minna-Bida Road, located on latitude 60
.001
and 6
0
7
1
West and longitude 90
3
1
and 9.101 North. As a result of water problem in Bida and its environs, the people living
in this environment suffered a lot due to lack of portable drinking water and water for domestic use. A
Geophysical survey carried out, employed the schlumberger Array method in which current were sent beneath
the earth surfaces, this was done at various points and the data collected. The area revealed three lithological
formations in some places while in some place five. With the lowest resistivty found to be 6.85 Ωm and the
highest resistivity was 12,774.46 Ωm. The lithotogical formation includes the sandstones, clayey sandstones,
sandy clay and ferruginised sandstone. Since this is a sedimentary area drilling is expected to be deep down to a
depth of about 70-75m
Similar to A Magnetotelluric Survey Of The North Perth Basin A Technical Case Study (20)
PPT Writing A Narrative Essay PowerPoint Presentation Free ToAngela Shin
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A Magnetotelluric Survey Of The North Perth Basin A Technical Case Study
1. ASEG-PESA 2015 – Perth, Australia 1
A Magnetotelluric survey of the North Perth Basin: A technical case
study
Thomas Hoskin Klaus Regenauer-lieb Alan Jones
SEE, UWA CSIRO Dublin Institute for Advanced Studies
35 Stirling Hwy ARRC, Kensington Address
hoskit01@student.uwa.edu.au Klaus.regenauerlieb@csiro.au alan.jones@dias.cp.ie
INTRODUCTION
The Perth Basin is a rift basin, dominated by north striking
sub-basins, troughs and ridges, bounded by major normal
faults (Song & Cawood, 2000). Covering approximately 45
000 km2
onshore and 55 000 km2
offshore it is located to the
west of the Yilgarn Craton, and formed during Permo-
Cretaceous rifting between Australia and Greater India (Song
et. al. 2001). It is an established petroleum province, with
operating fields both on and offshore, hosts large mineral sand
deposits and is the source of most of Western Australia’s
ground water resources (Mory & Iasky, 1996, Song et. al.,
2001).
The Perth Basin is considered prospective for geothermal
resources. A thick sedimentary succession provides deep,
highly porous aquifers, targets for Hot Sedimentary Aquifer
(HSA) plays while regions of basement uplift, such as the
Beagle Ridge, are thought to host radiogenic granites,
potential targets for Hot Dry Rock (HDR) plays. Low
porosity successions provide thermal insulation, trapping heat
while proximity to major population centres provides a
market. In 2009, Geothermal Exploration Permits (GEPs)
were released for geothermal exploration and were acquired
by several companies to explore for both HSA and HDR
systems.
Chopra & Holgate (2005) present a nationwide analysis of
temperature data within the Australian crust, extrapolating
drillhole data to map temperature at depth, providing an
invaluable tool for geothermal exploration. Heat anomalies in
the Perth Basin are identified in several areas, particularly the
Beagle Ridge. Increased heat production and thermal
conductivity is measured in rocks of the Pinjarra Orogen,
which form the Beagle Ridge and basement to the basin
identifying the Beagle Ridge as a potential target (Hot Dry
Rocks Ltd., 2008).
As a fundamentally different resource, improved
understanding of not only the geology but also the geophysical
characteristics pertinent to geothermal resources, are essential.
Considerable geological and geophysical data exist for the
Perth Basin. Gravity, Magnetics, Seismic, Borehole logging
and some EM data are available, however distribution is
varied with areas of the basin having almost no information.
Electrical resistivity methods are sensitive to both heat and
fluid content (Archie, 1942, Llera et. al., 1990, Telford, 1990,
Zisser et. al., 2010). Conductivity of fluid phases, including
SUMMARY
Original motivation of this study was to understand
important structures with a proven geothermal signature
associated with high temperatures in the shallower basin
and high flow rates in the aquifers. Anomalous
temperatures are recorded around the Beagle Ridge and
significant flow rates observed near the Urella Fault,
factors important to unconventional geothermal
prospects. The focus of this study was therefore a detailed
geophysical investigation of several Geothermal
Exploration Permits (GEPs) in the North Perth Basin.
Two Magnetotelluric (MT) surveys are conducted over
target areas in the North Perth Basin and adjoining
tectonic domains to provide information about the
electrical conductivity regime of the basin and western
margin of the Yilgarn Craton. Existing geophysical data
in this part of the basin are sparse and electrical data for
the basin in general is limited to shallow Time Domain
Electromagnetic (TDEM) data targeting superficial
aquifers.
High-resolution MT data, acquired between 2011 and
2013, provide information on mid-deep crustal rocks. In
addition, new gravity data and joint interpretation of
these data sets are undertaken to improve the geological
model of the North Perth Basin and test some existing
hypotheses.
We present a best practice case study and workflow for
data acquisition and filtering, robust dimensionality
analysis and removal of distortion effects from
impedance tensor estimates. 1D and 2D inversions are
found to be largely sufficient for the majority of these
data while 3D modelling provides an additional tool to
verify results. Finally, modelling of gravity data and
integrated interpretation ensures robust geological models
for the area are consistent with all data available.
We conclude with several inferences about the geology in
this area. 1) Electromagnetic (EM) and gravity data does
not seem to support significant crustal thinning beneath
the basin. 2) The Dandaragan Trough appears deeper than
generally modelled and 3) extremely high conductivities
persist to depth in the basin.
Key words: Magnetotellurics, Gravity, North Perth Basin
2. Abbreviated title eg: Author1, Author2 and Author3
ASEG-PESA 2015 – Perth, Australia 2
aqueous solutions and melts, tend to be orders of magnitude
greater than that of the host rock. Even small volumes of
interconnected pore space can greatly alter the electrical
resistivity of a rock volume. Porosity and permeability play a
crucial role in geothermal application, dominating energy
recovery rates. Clay alteration halos, often associated with
geothermal reservoirs, also significantly increase conductivity
and in volcanic geothermal systems are mapped to identify
potential reservoirs.
MT is a favoured tool for deep crustal studies. As a passive
technique, source signals are high amplitude with a broad
frequency range, allowing conductivity anomalies to be
imaged at greater depth than other EM techniques. Impedance
tensors are frequency dependent providing a measure of depth
control not available with potential field techniques. The
combination of investigative depth and sensitivity to resistivity
variations, key proxies for porosity, permeability and
alteration, make MT an ideal tool for fluid delineation in the
crust at depths significant in the context of the Perth Basin and
geothermal resources.
It is essential to establish a workflow for acquisition,
processing and modelling of MT data which adequately
applies proper analysis and modelling techniques. Poor data
analysis and modelling practises are common in many
published MT case studies, leading to erroneous results and a
lower consideration of MT data. We apply a range of modern
techniques to analyse the MT impedance tensor. 1D and 2D
modelling are conducted using robust modelling algorithms
and appropriately decomposed impedance tensors.
The main aims of conducting MT surveys in the basin are to
1) map depth to basement, 2) investigate the conductivity
regime of the basin, 3) to investigate the nature of major
geological structures. Gravity, Magnetic, Seismic and
Borehole data are also used to constrain MT models and aid in
interpretation.
METHOD AND RESULTS
MT and TDEM soundings are acquired along two, east-west
traverses of the North Perth Basin and western Yilgarn. The
New Norcia (NN) traverse follows the 1992 BMR New Norcia
geo-scientific traverse (Middleton et. al., 1993) and the
Coorow-Greenhead (CGH) traverse follows pre-existing
seismic lines from the Booragoon and Dandaragan East Flank
reflection seismic surveys where possible, extending to the
east onto the Yilgarn near the town of Marchagee.
19 MT and Time Domain Electromagnetic (TDEM) soundings
are acquired along the NN traverse, with a maximum station
spacing of 2-3km, and 90 MT, 36 AMT, 9 long period MT and
48 TDEM soundings are acquired along the CGH traverse.
Nominal station spacing is 2km with extensive infill
conducted across the Darling Fault Zone (DFZ) and Beagle
Ridge, providing higher resolution across the fault and
prospective geothermal environments.
The MT method is a passive electromagnetic method which
measures temporal variations in the Earths naturally occurring
electric (E) and magnetic fields (H). For each sounding, two
horizontal components of the electric field, Ex and Ey, two
horizontal components, Hx and Hy and, where possible, one
vertical component, Hz, of the magnetic field are measured.
Electric field components are measured using non-polarising
electrodes while magnetic field components are measured with
coil magnetometers, sensitive to frequencies from 10kHz up to
2000 s.
Figure 1: Standard MT deployment for Phoenix MT
system
MT soundings were conducted over two nights, AMT
soundings over 3 hours and long period MT over
approximately 22 days. A combination of broadband Phoenix
and AuScope systems were used to acquire MT time-series
data. For long period deployments induction coils are
replaced with fluxgate magnetometers providing sensitivity
from 10s to over 10000 s. TDEM measurements were made
using the Phoenix V8 system using a standard in-loop
configuration and vertical component only, receiver coil
located at the centre of the MT station.
WORKFLOW
Time series exhibit relatively low noise, with localised, 50 Hz
power-line noise being the only consistent major contributor.
Pre-processing is applied to eliminate 50 Hz and harmonic
noise, which varies in severity from site to site.
MT data were processed using Chave & Thompson’s Bounded
Influence Remote Reference Processing (BIRRP) code,
providing robust estimates of the MT response function from
10kHz down to 10k seconds (Chave & Thompson, 2003).
Proprietary processing algorithms provided with Phoenix
recorders have also used to process time-series recorded using
Phoenix systems to compare with BIRRP results to verify
processing codes. Comparison indicate better results are
obtained at higher frequencies using Phoenix processing,
however, at longer periods BIRRP produce more robust results
characterised by smaller errors. Remote referencing is used as
standard, to reduce local station noise and improve impedance
tensor estimates.
Figure 2: Geo-electric strike directions calculated for both
the NN and CGH transects, demonstrate a general NNW
strike direction.
Dimensionality of the MT response function is characterised
using several methods. Impedance tensor rotational invariants
are used to summarise dimensionality across the data set using
the WALDIM method (Marti et. al., 2009). Caldwell, (2004)
Phase Tensors and McNeice & Jones, (2001) Strike Analyses,
Figure 2, were used to determine the dominant geo-electric
3. Abbreviated title eg: Author1, Author2 and Author3
ASEG-PESA 2015 – Perth, Australia 3
strike strike for major tectonic elements are summarised in
Table 1.
Strike Geological Feature
355-360o
Yilgarn Craton
020-040o
Pinjarra Orogen - long periods over the basin
335-010o
Basin Sediments
Table 1: Geo-electric strike for major geological features
in the study area, determined from a combination of
WALDIM, Phase Tensor and Strike Analysis.
Distortion effects, caused by inhomogeneities at scales smaller
than the resolving power of the experiment, are also known to
be particularly problematic to MT results. McNeice & Jones
(2001) show that distortion effects can be described by the
distortion tensor, C, which has several determinable elements,
Twist, Shear and Anisotropy, and an indeterminable element,
g, which is also called the static-shift (McNeice & Jones,
2001).
The McNeice and Jones tensor decomposition method allows
the determinable parts of the distortion tensor to be estimated
using either single or multiple sites. Distortion and
dimensionality effects are then removed, providing distortion
free, correctly rotated impedance tensors for 1D and 2D
modelling.
DISCUSSION
Pronounced differences in electrical characteristics of major
elements of the Yilgarn Craton allow these to be delineated.
A contrast in resistivity of 1-2 orders of magnitude, correlates
with the Yandanooka Cape-Riche lineament, the eastern
boundary of the South West Gneissic Terrane (SWGT) and the
Lake Grace Terrane, see Figure 3. An easterly dipping
resistivity contact correlates with shear zones inferred from
seismic interpretation (Middleton et. al., 1993). Previous
investigations identify a 40 mGal gravity anomaly associated
with the SWGT across this lineament, as well as decreased
seismic velocity (Everingham, 1966, Dentith, 1994).
Figure 3: NN transect 2D inversion illustrating major
tectonic elements.
While the resistivity regime of the SWGT largely
homogenous, a narrow, eastward dipping conducting anomaly
is observed in upper 2km that correlates with a second shear
zone identified from seismic data, characterising the contact
between the Chittering and Jimperding metamorphic belts
(Middleton et. al., 1993).
We find correlation between the geometry of conductive rocks
overlying the Yilgarn and a zone of lower density required to
fit observed gravity data (Long, 1996). However, there is little
evidence in EM results of the delamination and stratification
of the Yilgarn at depth (Dentith et. al., 1994).
A deep seated conductivity anomaly is identified associated
with the DFZ. While fault zone conductors have been
identified on large tectonic fault zone, these usually exhibit
seismic character, with conductivity anomalies in the upper
10-20km only. As a seismically quiescent feature,
identification of such a deep conductivity anomaly warrants
further investigation of the fault architecture and plausible
scenarios for generating these anomalies.
Current best models for depth to basement are still poorly
constrained for this part of the basin but a maximum basement
depth of 10km is interpreted (Mory & Iasky, 1996, Aitken,
2010). Depth to basement models rely primarily on gravity
data, locally constrained by seismic interpretations. Gravity
data are more regular distributed though are inherently non-
unique. Many gravity measurements are old, ~50 years with
poor elevation precision and large (~12km) station spacing.
Seismic data have limited distribution and seldom image
basement in the basin. We treat these data as unreliable and
where possible use 2D modelling of more recent gravity data
to interpret basement depth.
Basin sediments exhibit extremely low resistivity, in some
cases less than 3 Ω.m. Mapping basement topography over the
Beagle Ridge and shallower parts of the basin is easy, as
basement rocks have resistivities over 4 orders of magnitude
greater than those encountered in sediments. Unexpected high
conductivities in the basin, coupled with thick sediments, lead
to a significant reduction in depth of penetration of broadband
MT (BBMT) soundings. We rely on long period MT
soundings to increase the depth of penetration to supplement
broadband data. EM results indicate a depth to basement of
about 12km. We test this hypothesis using gravity modelling
and find we can fit a basement at 12km with limited alteration
to assumed density values for the deeper basin sediments.
Previous gravity modelling implies a fundamental change in
crustal thickness across the DFZ is required to fit gravity data,
from 27km to 45km (Middleton et. al., 1993). EM models are
more reliable in areas of shallow basement, such as the Beagle
Ridge and Cadda Terrace. Highly resistive basement blocks
are observed to depth in these areas, Figure 4. Conductivity
structure beneath the Dandaragan Trough is less reliable
however, broadly supports limited crustal thinning to the west
of the DFZ as no conductivity change, indicative of the Moho,
is observed.
Figure 4: Resistive anomaly associated with uplifted
basement blocks is observed to continue to depth.
While these findings are inconclusive, we note similar
observations from the Moho Geometry Gravity Inversion
Experiment (MoGGIE) models as well as seismic receiver
functions calculations (Revets, pers. comms., 2011).
Remodelling of gravity data we find gravity response can be
well fit by either model, again with limited alteration to
assumed densities of basin sediments.
Published models for extension during the cretaceous follow a
classic narrow rift model, as defined by Buck, (1991), Figure
SWGT
Lake Grace
Terrane
Perth
Basin
DFZ
Beagle Ridge
Dandaragan
Trough
4. Abbreviated title eg: Author1, Author2 and Author3
ASEG-PESA 2015 – Perth, Australia 4
5(a). Considering the lack of appreciable crustal thinning and
the DFZ becoming listric at depth, we propose core complex
mode of extension is a more accurate model for extension
which formed the Perth Basin, Figure 2(b).
Figure 5: Models for crustal extension (after Buck, 1991)
illustrating the classic model for rift systems (a) and the
model which better fits our observations (b)
Deep Conductivity
Accurately imaging resistors below conductors is difficult
using electric techniques as electrical energy is attenuated by
the conductor, effectively reducing the depth which can be
imaged. Basin environments are characterised by highly
conductivity sediments due to highly conductive fluids filling
pore space.
Initial analysis of BBMT data, located over the Dandaragan
Trough, indicate apparent reistivities decrease with depth,
from 10-100s of Ω.m., to <3 Ω.m. at the longest periods.
Induction logs, from proximal petroleum wells, measure
similarly low resistivities (5-70 Ω.m.) for shallow sediments.
We might expect, due to compaction of pore space and
subsequent closing of permeability pathways, to see an
increase in resistivity with depth.
Ongoing work aims to 1) correlate resistivity profiles between
MT and downhole measurements and 2) map permeability and
estimate porosity for the North Perth Basin.
CONCLUSIONS
MT models allow us to provide a new estimate of maximum
depth of basement in this area which can be shown to be
consistent with other geophysical data sets. EM results
indicate high resistivity anomalies, associated with basement
rocks, persist to depth suggesting a crustal thickness of
approximately 33 km.
We identify a deep seated conductive anomaly associated with
the DFZ, implying a more complex internal structure.
Fundamental differences in electric character between the
Yilgarn and the Pinjarra Orogen support pronounced change
in lithology across the DFZ. Finally ongoing research into
mapping porosity and permeability in the basin will provide a
useful tool for Geothermal Exploration in the Perth Basin.
ACKNOWLEDGMENTS
We would like to thank Aurore Joly, Ray Addenbrooke, Rob
Delhaye, Annie Zaino and Javier Gonzalez for their assistance
in data acquisition, Mike Dentith for his ongoing support and
expert assistance. Shane Evans at Moombarriga Geoscience,
GSWA, IESE and AuScope for equipment use and technical
expertise and New World Energy Ltd. for funding this
research.
REFERENCES
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