1983 and 1984 Alaska Division of Geological and Geophysical Surveys geothermal fluids sampling and well logging at the Makushin geothermal area:

Hot springs and igneous rocks are present widely in southeast China, influenced by the subduction of the Western Pacific and Philippine Sea Plates. This study reports on new data of chemical compositions and He–Ne–C isotopes for gas samples from representative hot springs and wells in the Guangdong and Fujian provinces to identify the origin of hydrothermal volatiles and provide insight into geothermal tectonic affinities. The primary hydrothermal volatile component from southeast China is atmospheric N2, with a volumetric percentage of 82.19%–98.29%. It indicates medium-low temperature geothermal systems where geothermal fluids suffered a shallow circulation in closed fracture systems. Low CO2 and CH4 contents and their depleted δ13C values confirmed the small number of deep-derived components in the study area. However, spatially discernible geochemical characteristics imply enhanced hydrothermal fluid convection in the adjacent area of the two provinces, including the Fengshun, Zhangzhou, Longyan, and Sanming geothermal fields. Specifically, the He–Ne isotopes from this area exhibit mantle He contribution of more than 10% and mantle heat flow accounts for more than half of the total heat flow. Moreover, according to the thermal background calculations, the highest heat flow value of 77.7 mW/m2 is indicated for the Zhangzhou geothermal area and the lowest value of 54.7 mW/m2 is indicated for the Maoming geothermal area. Given the epicenter distributions and the corresponding earthquake magnitudes, the NE-trending faults are heat-control tectonic structures and their intersections with the NW-trending faults provided expedite channels for geothermal fluids rising to the surface. Therefore, the preferred development potential of geothermal resources can be expected in the adjacent area of the two provinces where two sets of active faults crossed. This study provides critical information on understanding the geothermal distribution controlled by the tectonic structure in southeast China.

Download Full-text

Comparison robust data smoothing algorithms with wavelet filter for denoising sonic log signals

10.21203/rs.3.rs-727289/v1 ◽

2021 ◽

Author(s):

Saeed Aftab ◽

Rasoul Hamidzadeh Moghadam

Keyword(s):

Normal Distribution ◽

Well Logging ◽

Wavelet Filter ◽

Data Smoothing ◽

Log Data ◽

Smoothing Methods ◽

Sonic Log ◽

Uniform Noise ◽

Geophysical Surveys ◽

Better Than

Abstract Well logging is an essential approach to making geophysical surveys and petrophysical measurements and plays a key role to interpret downhole conditions. But, well logging signals usually contain noise that distorts results and causes ambiguous interpretations. In this paper, the wavelet filter and robust data smoothing algorithms are tested for denoising synthetic sonic log and field sonic log data. Robust data smoothing algorithms include Gaussian, RLOESS (Robust locally estimating scatterplot smoothing), and RLOWESS (Robust locally weighted scatterplot smoothing) methods. Uniform and normal distribution noise applied to synthetic model and results revealed that the wavelet filter performs better than data smoothing algorithms for denoising uniform distribution noise. However, the RLOESS removed uniform noise acceptably. But, for normal distribution noise, the wavelet filter disrupts and data smoothing algorithms, specifically RLOESS attenuated noise perfectly. Due to the noise nature of field sonic log data, wavelet filter completely disrupts, but data smoothing algorithms removed the noise of field data more efficiently, particularly RLOESS. So, we can express that RLOESS is a perfect algorithm for denoising sonic log signals, regardless of noise nature.

Download Full-text

GEOELECTRICAL SIGNATURES AND THEIR RELATIONSHIPS WITH THE LATERITIC HORIZONS: A CASE STUDY OF THE N4EN MINE’S IRON CAVE, CARAJÁS COMPLEX, BRAZIL

Brazilian Journal of Geophysics ◽

10.22564/rbgf.v37i4.2013 ◽

2019 ◽

Vol 37 (4) ◽

pp. 235

Author(s):

GUILHERME A. S. PROSDOCIMI ◽

MARCO A. DA S. BRAGA ◽

MARCELO R. BARBOSA ◽

IURI VIANA BRANDI

Keyword(s):

Electrical Resistivity ◽

Well Logging ◽

Near Surface ◽

Applied Geophysics ◽

Geophysical Surveys ◽

Iron Mine ◽

Northern Brazil ◽

Iron Formations ◽

Lateritic Profile

ABSTRACT The Brazilian speleological heritage is protected by laws, and every region where caves are present requires scientific studies to assist in environmental licensing. In the context of mining in iron formations, the near-surface geophysical studies using electroresistivity survey were performed in the cave N4E-0022, located at the N4EN iron mine, Carajás Complex, northern Brazil. The near-surface geophysical surveys generated continuous images that enhanced the lithostructural mapping of the lateritic profile, especially in places to which access by conventional methods was difficult. The electrical resistivity profiles were acquired with the dipole-dipole arrangement in the upper portion of the cave. Three sections were performed in SW-NE direction and two in SE-NW direction, totaling 435 meters of acquisition. The geoelectrical signatures were correlated with the lithologic logs of drillholes, the geophysical well logging and with the typical lateritic profile in the cave N4E-0022 surroundings. The results showed a satisfactory interpretation for the near-surface geoelectrical profiles and evolved to a comparison with the lateritic profile (lateritic crust, transition horizon, and saprolite horizon), providing inherent resistivity signatures for each modeled material.Keywords: applied geophysics, iron cave, Carajás.RESUMO O patrimônio espeleológico brasileiro é protegido por leis, e qualquer região com a presença de cavidades precisa de estudos científicos para auxiliar o licenciamento de empreendimentos. No contexto da mineração em terrenos ferríferos, estudos geofísicos rasos utilizando eletrorresistividade foram executados na cavidade N4E-0022, localizada no extremo norte da Mina de N4EN, Complexo Carajás. A geofísica rasa gerou imagens contínuas que potencializaram o mapeamento lito-estrutural do substrato rochoso, principalmente em locais de difícil acesso aos métodos convencionais. Os perfis de eletrorresistividade foram adquiridos com arranjo dipolo-dipolo na porção superior da cavidade. de modo paralelo entre si na porção superior da cavidade. Três seções foram executadas na direção SW-NE e duas na direção SE-NW, totalizando 435 metros de aquisição. As assinaturas geoelétricas das seções foram correlacionadas com as descrições litológicas de furos de sondagem, perfilagens geofísicas de furos de sonda e o mapeamento de detalhe do perfil laterítico no entorno da cavidade N4E-0022, evidenciando um resultado satisfatório para as interpretações realizadas. Os resultados evoluíram para uma comparação com o perfil de alteração típico de rochas ferruginosas (crosta laterítica, horizonte de transição e saprolito), e forneceram assinaturas de resistividades inerentes à cada material modelado. Palavras-chave: geofísica aplicada, caverna ferrífera, Carajás.

Download Full-text

Three-Dimensional Analysis of Temperature Distribution in A Geothermal Area Using Well-Logging Data Set.

GEOINFORMATICS ◽

10.6010/geoinformatics.15.15 ◽

2004 ◽

Vol 15 (1) ◽

pp. 15-24 ◽

Cited By ~ 3

Author(s):

Setsuro MATSUDA ◽

Katsuaki KOIKE

Keyword(s):

Temperature Distribution ◽

Dimensional Analysis ◽

Three Dimensional ◽

Well Logging ◽

Geothermal Area ◽

Data Set

Download Full-text

ANALYSIS OF SHALLOW SUBSURFACE STRUCTURE AT GEOTHERMAL AREA OF IE JUE USING RESISTIVITY METHOD

Jurnal Natural ◽

10.24815/jn.v18i1.9676 ◽

2018 ◽

Vol 18 (1) ◽

pp. 18-21

Author(s):

Syafrizal Idris ◽

Muhammad Syukri ◽

Muhammad Syukri Surbakti ◽

Marwan . ◽

Muchlis . ◽

...

Keyword(s):

Electrical Resistivity ◽

Imaging Method ◽

Geological Condition ◽

Geothermal Area ◽

Subsurface Structure ◽

Weak Zone ◽

Electrical Resistivity Survey ◽

Geothermal Fluids ◽

Conductive Zone ◽

Resistivity Survey

It has been conducted a geo-electrical resistivity survey at geothermal area of Ie Jue, Aceh Besar. The survey aims to measure resistivity value in the area. It is expected that the values of resistivity will image the subsurface structure in the area. In addition geological features in the area are shown after we process it. The data acquisition in this study was acquired using a SuperSting R8/IP resistivitymeter and its data processing using EarthImager 2D software to get the image of resistivity pseudosection. The two lines of measurement crossed the surface geothermal manifestation. Each line has 330 m in length, and 56 electrodes with electrode space of 6 m. The result of resistivity pseudosection model interpreted based on geological condition and observation in the area. Resistivity pseudosection model shows the study is water-saturated (<64.0 Ωm) to a depth of ±65 m and a highly conductive zone (0.6-3.5 Ωm) with a thickness of 30-50 m. This conductive layers below the embodied surface at a distance of 158-160 m on the IJ-Y1 line and at a range of 130-185 m on the IJ-Y2 line. This conductive zone is indicated as a weak zone where geothermal fluids are transported to the surface.Keywords: Geothermal, Ie Jue, geo-electrical resistivity survey, resistivityREFERENCES Bennet, J.D., Bridge, D.McC., Cameron, N.., Djunuddin, A., Ghazali, S.A., Jeffrey, D.H., Kartawa, W., Rock, M.N.S., Thomson, S.J., Whandoyo, R., 1981. PetaGeologiLembar Banda Aceh, Sumatera, Puslitbang Geologi. Bandung.Syukri, M., Saad, R., Nordiana, M., & Azwin, I. 2014. Preliminary Study of Sumatera Fault Using 2-D Resistivity Imaging Method. Electronic Journal of Geotechnical Engineering, 19.Knödel, K., Lange, G., & Voigt, H.J., 2007. Environmental geology: Handbook of field methods and case studies: Springer Science & Business Media.Telford, W. M., Geldart, L. P., Sheriff, R. E. 1990. Applied Geophysics Second Edition, Cambridge University Press, USAMarwan, M., Rusydy, I., Nugraha, G.S. and Asrillah, A., 2014. Study of Seulawah Agam’s Geothermal Source Using Gravity Method. Jurnal Natural, 14(2)Asrillah, A., Marwan, M., Rusydy, I. and Nugraha, G.S., 2014. Application of Magnetics Method to Mapping the Geothermal Source at Seulawah Agam Area. Jurnal Natural, 14(2).Ismail, N.,Ramadhan, S., 2013. Karakterisasi Struktur Dangkal pada Lapangan Panas Bumi Seulawah Agam Menggunakan Metode Very Low Frequency (VLF). Prosiding Semirata FMIPA Universitas Lampung. Lampung, Indonesia.

Download Full-text

Suitability Determination of Machine Learning Techniques for the Operational Quality Assessment of Geophysical Survey Results

Applied Computer Systems ◽

10.2478/acss-2020-0017 ◽

2020 ◽

Vol 25 (2) ◽

pp. 153-162

Author(s):

Kirill Abramov ◽

Janis Grundspenkis

Keyword(s):

Machine Learning ◽

Quality Assessment ◽

Geophysical Methods ◽

Well Logging ◽

Geophysical Survey ◽

Machine Learning Techniques ◽

Drilling Process ◽

Learning Techniques ◽

Operational Quality ◽

Geophysical Surveys

AbstractWell logging, also known as a geophysical survey, is one of the main components of a nuclear fuel cycle. This survey follows directly after the drilling process, and the operational quality assessment of its results is a very serious problem. Any mistake in this survey can lead to the culling of the whole well. This paper examines the feasibility of applying machine learning techniques to quickly assess the well logging quality results. The studies were carried out by a reference well modelling for the selected uranium deposit of the Republic of Kazakhstan and further comparing it with the results of geophysical surveys recorded earlier. The parameters of the geophysical methods and the comparison rules for them were formulated after the reference well modelling process. The classification trees and the artificial neural networks were used during the research process and the results obtained for both methods were compared with each other. The results of this paper may be useful to the enterprises engaged in the geophysical well surveys and data processing obtained during the logging process.

Download Full-text

Integration of Multi-geophysical Approaches to Identify Potential Pathways of Heavy Metals Contamination - A Case Study in Zeida, Morocco

Journal of Environmental and Engineering Geophysics ◽

10.32389/jeeg9-067 ◽

2020 ◽

Vol 25 (3) ◽

pp. 415-423

Author(s):

Ahmed Lachhab ◽

El Mehdi Benyassine ◽

Mohamed Rouai ◽

Abdelilah Dekayir ◽

Jean C. Parisot ◽

...

Keyword(s):

Heavy Metals ◽

Seismic Velocity ◽

Seismic Refraction ◽

Geophysical Methods ◽

Low Frequency ◽

Electrical Current ◽

P Wave ◽

Low Resistivity ◽

Refraction Tomography ◽

Geophysical Surveys

The tailings of Zeida's abandoned mine are found near the city of Midelt, in the middle of the high Moulouya watershed between the Middle and the High Atlas of Morocco. The tailings occupy an area of about 100 ha and are stored either in large mining pit lakes with clay-marl substratum or directly on a heavily fractured granite bedrock. The high contents of lead and arsenic in these tailings have transformed them into sources of pollution that disperse by wind, runoff, and seepage to the aquifer through faults and fractures. In this work, the main goal is to identify the pathways of contaminated water with heavy metals and arsenic to the local aquifers, water ponds, and Moulouya River. For this reason, geophysical surveys including electrical resistivity tomography (ERT), seismic refraction tomography (SRT) and very low-frequency electromagnetic (VLF-EM) methods were carried out over the tailings, and directly on the substratum outside the tailings. The result obtained from combining these methods has shown that pollutants were funneled through fractures, faults, and subsurface paleochannels and contaminated the hydrological system connecting groundwater, ponds, and the river. The ERT profiles have successfully shown the location of fractures, some of which extend throughout the upper formation to depths reaching the granite. The ERT was not successful in identifying fractures directly beneath the tailings due to their low resistivity which inhibits electrical current from propagating deeper. The seismic refraction surveys have provided valuable details on the local geology, and clearly identified the thickness of the tailings and explicitly marked the boundary between the Triassic formation and the granite. It also aided in the identification of paleochannels. The tailings materials were easily identified by both their low resistivity and low P-wave velocity values. Also, both resistivity and seismic velocity values rapidly increased beneath the tailings due to the compaction of the material and lack of moisture and have proven to be effective in identifying the upper limit of the granite. Faults were found to lie along the bottom of paleochannels, which suggest that the locations of these channels were caused by these same faults. The VLF-EM surveys have shown tilt angle anomalies over fractured areas which were also evinced by low resistivity area in ERT profiles. Finally, this study showed that the three geophysical methods were complementary and in good agreement in revealing the pathways of contamination from the tailings to the local aquifer, nearby ponds and Moulouya River.

Download Full-text