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Recent Advances in Exploration Geophysics

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A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Earth Sciences".

Deadline for manuscript submissions: 31 May 2024 | Viewed by 12670

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Dr. Jakub Ciazela

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Institute of Geological Sciences, Polish Academy of Sciences, Wroclaw, Poland
Interests: geology; geochemistry; ore formation
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Dear Colleagues,

Exploration geophysics aims at determining the mechanical, magnetic, and electric properties of rocks with the aim of conducting geological explorations of ore minerals and other resources. Scientific and technological progress has revolutionized methods of exploration geophysics.

Traditional gravimetric, seismological, magnetic, electric, and radiometric methods are now combined with remote sensing, planetary geology, and machine learning methods. The combination of geophysical methods with machine learning, and especially deep learning, helps increase the efficiency of the geophysical investigation for ore or petroleum prospecting. Exploration geophysics is being employed more and more often in newly emerging concepts such as space mining, with significant efforts being made to prepare instruments suitable for resource prospecting on Mars, the Moon, and asteroids.

This Special Issue, entitled “Recent Advances in Exploration Geophysics”, invites articles focused on resource prospecting using geophysical methods. We welcome papers from various fields across geophysics, economic geology, geochemistry, mineralogy, remote sensing, planetary sciences, and engineering.

Dr. Jakub Ciazela
Guest Editor

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Keywords

seismic methods
gravimetry
electrical conductivity
ore minerals
hydrocarbons
groundwaters
remote sensing
geology

Published Papers (11 papers)

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Research

22 pages, 9880 KiB

Open AccessArticle

Graphite Content Identification with Laboratory and Field Spectral Induced Polarization Measurements

by Tímea Katona, Adrián Flores-Orozco, Lukas Aigner and Christian Benold

Appl. Sci. 2024, 14(10), 3955; https://doi.org/10.3390/app14103955 - 7 May 2024

Viewed by 370

Abstract

Graphite, a critical raw material, prompts interest in assessing former quarries for volumetric content, driving the need for accurate prospection techniques. We explore the efficacy of spectral induced polarization (SIP) imaging at field scale for this purpose. Field measurements in a quarry with unknown graphite content underscore the need for assessment before drilling due to abrupt topography. Due to the lack of ground truth required to calibrate existing petrophysical models, we propose using SIP laboratory measurements to achieve the quantitative interpretation of the imaging results. We conducted experiments at two scales: rock plugs for material response and ground rocks of varying sizes for textural analysis. The rock plugs allow us to investigate the response of the material, while the ground samples permit us to understand changes in the SIP response for varying textural properties. Our lab work establishes power-law relationships between polarization (expressed in terms of normalized chargeability) and graphite content, as well as relaxation time and grain size. Salinity dependence is noted between chargeability, normalized chargeability, and relaxation time. Utilizing these findings, we provide a quantitative interpretation of field SIP imaging results. Full article

(This article belongs to the Special Issue Recent Advances in Exploration Geophysics)

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20 pages, 9549 KiB

Open AccessArticle

Advancing Quantitative Seismic Characterization of Physical and Anisotropic Properties in Shale Gas Reservoirs with an FCNN Framework Based on Dynamic Adaptive Rock Physics Modeling

by Xinhui Deng, Xinze Kang, Duo Yang, Wei Fu and Teng Luo

Appl. Sci. 2024, 14(4), 1469; https://doi.org/10.3390/app14041469 - 11 Feb 2024

Viewed by 515

Abstract

Quantitative seismic methods are crucial for understanding shale gas reservoirs. This study introduces a dynamic adaptive rock physics model (DARPM) designed to systematically quantify the relationship between physical parameters and elastic parameters within shale formations. The DARPM uniquely adapts to changes in formation dip angle, allowing adaptive reservoir property assessment. An innovative adaptive rock physics inversion methodology is subsequently proposed to compute values for reservoir physical and seismic anisotropy parameters. This is achieved using well log data and building upon the foundation laid by the established DARPM. We introduce the RPM-FCNN (rock physics model—fully connected neural network) framework, seamlessly integrating the DARPM with the corresponding inversion results into a comprehensive model. This framework facilitates a quantitative analysis of the nonlinear relationship between elastic and reservoir physical parameters. Utilizing the trained RPM-FCNN framework, the spatial distribution of reservoir and seismic anisotropic characteristics can be precisely characterized. Within this framework, the organic matter mixture aspect ratio indicates the continuity of organic matter, while the organic matter porosity reveals the maturity of organic matter. Simultaneously, seismic anisotropy characteristics signify the degree of stratification within the reservoirs. This method, therefore, establishes a robust foundation for identifying favorable areas within shale gas reservoirs. Full article

(This article belongs to the Special Issue Recent Advances in Exploration Geophysics)

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21 pages, 1832 KiB

Open AccessArticle

Lunar Cold Microtraps as Future Source of Raw Materials—Business and Technological Perspective

by Adam Jan Zwierzyński, Jakub Ciążela, Piotr Boroń and Weronika Binkowska

Appl. Sci. 2023, 13(24), 13030; https://doi.org/10.3390/app132413030 - 6 Dec 2023

Viewed by 681

Abstract

The article uses the Lunar QuickMap tool to analyze and select five highly promising cold microtraps on the Moon in terms of the size of the deposits they contain and their accessibility with the use of rovers and other wheeled vehicles. Since the thickness of the layer containing raw materials is subject to high uncertainty, three arbitrary scenarios for the value of this parameter were assumed: pessimistic (1 cm), nominal (5 cm), and optimistic (1 m). For the analyzed sites, a preliminary market valuation of the raw materials contained therein will be obtained at USD 74 billion; USD 370 billion; USD 7403 billion for the assumed pessimistic, normal, and optimistic scenarios, respectively. The article presents a business and technological perspective on the issue of space mining on the Moon. It is also a selected synthesis of the state of knowledge about space mining on the Moon. Full article

(This article belongs to the Special Issue Recent Advances in Exploration Geophysics)

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25 pages, 33945 KiB

Open AccessArticle

A Multidisciplinary Investigation of an Abandoned Old Mining Area Which Has Been Affected by the Combined Influences of Salt Karst and Human Exploration Activity

by Zbigniew Szczerbowski and Rafał Gawałkiewicz

Appl. Sci. 2023, 13(22), 12196; https://doi.org/10.3390/app132212196 - 10 Nov 2023

Viewed by 573

Abstract

The authors discuss a case that is full of examples of the problems faced by civil engineers whose task is to develop areas in the face of natural, technological, or post-mining hazards. The study area is in the central part of Inowrocław, a town located on a massive salt dome of Zechstein salts. A strong deformation zone expanded in its upper part; this was caused by a natural process (related to so-called salt karst) and by mining activities that occurred in the past, creating a problem with regard to any potential spatial development in the town. The authors show a combination of data obtained using gravimetric and geodetic methods, which helps us to assess the geohazard risk. These include remote sensing data, which can be used to evaluate displacements of the ground surface. The authors used an approach that they term the Elevation Difference Method. This consists of determining displacements between ground surfaces: estimated on the basis of remote sensing data and on the basis of the historical data, when mounted measurement points (and remote sensing data) did not exist. The authors discuss the results in the light of the geological background. Within the area of the study, the displacements of the positive values dominate. The displacement occurs at 6 mm/yr on average and indicates diapiric uplift movement. The results are important for the town authorities for planning and development and for infrastructure management. Full article

(This article belongs to the Special Issue Recent Advances in Exploration Geophysics)

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24 pages, 8569 KiB

Open AccessArticle

Robust 3D Joint Inversion of Gravity and Magnetic Data: A High-Performance Computing Approach

by Abraham Del Razo Gonzalez and Vsevolod Yutsis

Appl. Sci. 2023, 13(20), 11292; https://doi.org/10.3390/app132011292 - 14 Oct 2023

Cited by 1 | Viewed by 1256

Abstract

One of the fundamental challenges in geophysics is the calculation of distribution models for physical properties in the subsurface that accurately reproduce the measurements obtained in the survey and are geologically plausible in the context of the study area. This is known as inverse modeling. Performing a 3D joint inversion of multimodal geophysical data is a computationally intensive task. Additionally, since it involves a modeling process, finding a solution that matches the desired characteristics requires iterative calculations, which can take days or even weeks to obtain final results. In this paper, we propose a robust numerical solution for 3D joint inversion of gravimetric and magnetic data with Gramian-based structural similarity and structural direction constraints using parallelization as a high-performance computing technique, which allows us to significantly reduce the total processing time based on the available Random-Access Memory (RAM) and Video Random-Access Memory (VRAM)and improve the efficiency of interpretation. The solution is implemented in the high-level programming languages Fortran and Compute Unified Device Architecture (CUDA) Fortran, capable of optimal resource management while being straightforward to implement. Through the analysis of performance and computational costs of serial, parallel, and hybrid implementations, we conclude that as the inversion domain expands, the processing speed could increase from 4× up to 100× times faster, rendering it particularly advantageous for applications in larger domains. We tested our algorithm with two synthetic data sets and field data, showing better results than standard separate inversion. The proposed method will be useful for joint geological and geophysical interpretation of gravimetric and magnetic data used in exploration geophysics for example minerals, ore, and petroleum search and prospecting. Its application will significantly increase the reliability of physical-geological models and accelerate the process of data processing. Full article

(This article belongs to the Special Issue Recent Advances in Exploration Geophysics)

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17 pages, 4875 KiB

Open AccessArticle

Unveiling Accurate Seismic Imaging through the Advanced Target-Oriented Kirchhoff Migration Method

by Farah Syazana Dzulkefli, Abdul Halim Abdul Latiff, Hazwan Syahmi Hashim, Amir Mustaqim Majdi, Herurisa Rusmanugroho and Junxiao Li

Appl. Sci. 2023, 13(19), 10615; https://doi.org/10.3390/app131910615 - 23 Sep 2023

Viewed by 666

Abstract

A major challenge for the oil and gas industry is expediting the exploration geophysics activity. It is necessary to produce fast and accurate image of the targeted hydrocarbon reservoir, yet it involves extensive dataset due to the target location lies in deeper subsurface. Therefore, target-oriented oil and gas-reservoir imaging is currently seen as more attractive than conventional full-volume migration, in terms of computation efficiency. Through the integration of seismic redatuming with Kirchhoff migration, we presented a target-oriented imaging workflow that can effectively reduce computational cost while simultaneously enhancing the accuracy of the migrated image. Kirchhoff migration is renowned for being one of the simplest and flexible migration techniques, making it straightforward to implement. However, this migration approach is typically avoided in the presence of complex geology, as it tends to introduce artifacts in the images, thereby disrupting the interpretation beneath the complex overburden. Therefore, this paper highlighted the advantages of utilizing seismic redatuming to retrieve data beneath the overburden, followed by the utilization of the redatumed data as input for Kirchhoff migration. With an improved signal to noise ratio, the primary reflection events were amplified, providing clearer representation of the subsurface structure within the hydrocarbon reservoir or targeted area. Additionally, we utilized the benefits of Kirchhoff migration and explored the feasibility of performing patch-based migration in several areas of interest beneath the salt layer. This approach aimed to reduce both the turnaround time and the associated seismic migration costs. The developed workflow then was subsequently put to the test and applied to both a sub-salt SEG Advanced Modeling (SEAM) model and field data situated in East Malaysia. Based on the outcomes of the target-oriented migration, the proposed methodology demonstrated its capability to generate better quality and instant migrated images within the designated region. Furthermore, the feasibility of target-oriented imaging with Kirchhoff migration was substantiated through the integration of seismic redatuming, resulting in significant benefits towards seismic processing, imaging, and interpretation. Full article

(This article belongs to the Special Issue Recent Advances in Exploration Geophysics)

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15 pages, 5802 KiB

Open AccessArticle

An Accelerated Algorithm for 3D Inversion of Gravity Data Based on Improved Conjugate Gradient Method

by Shuai Zhou, Hongfa Jia, Tao Lin, Zhaofa Zeng, Ping Yu and Jian Jiao

Appl. Sci. 2023, 13(18), 10265; https://doi.org/10.3390/app131810265 - 13 Sep 2023

Cited by 1 | Viewed by 726

Abstract

The 3D inversion algorithm for gravity data based on a smooth model constraint has been proven to yield a reasonable density distribution. However, as the amount of observed data and model parameters increases, the algorithm experiences issues with high memory consumption and prolonged computation time. Therefore, the corresponding problem in interpreting gravity inversion lies in developing a fast inversion algorithm. The conventional smooth model constraint inversion algorithm, based on regularization theory, requires the introduction of a model weighting function with a large matrix, and involves storage and operation of a large matrix with intermediate variables during inversion iteration, contributing significantly to the prolonged computation time. In this paper, a diagonal weight matrix is represented by vectorization, and the intermediate variable of the large matrix type in the iteration is replaced with the combination of a small matrix and a vector. Additionally, the algorithm flow of the conjugate gradient method is further optimized to minimize the number of vectors that need to be stored during iteration. As a result of these optimizations, the memory consumption of the algorithm during the operation process is successfully reduced. Finally, the experiments demonstrate the successful development of a fast 3D inversion algorithm for gravity data. Specifically, for a 80 × 80 × 20 mesh number inversion, our accelerated algorithm achieves an average speed of ~0.5 s per iteration, and the iterative process speeds up by a factor of 1000, providing an effective strategy for the fast inversion of large-scale data. Full article

(This article belongs to the Special Issue Recent Advances in Exploration Geophysics)

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21 pages, 5923 KiB

Open AccessArticle

Study on Migration Monitoring Technology of Chromium-Contaminated Site Based on Dual-Frequency Induced Polarization Method

by Zhimin Liu, Kaiyao Wei and Yue Pan

Appl. Sci. 2023, 13(15), 8849; https://doi.org/10.3390/app13158849 - 31 Jul 2023

Viewed by 752

Abstract

In order to reveal the migration process of chromium-contaminated sites, COMSOL5.6 software was used to build the initial model of the chromium pollution source and analyze the migration change characteristics over time based on the rule of groundwater movement and Convection–Dispersion equation. COMSOL provides fully coupled multiphysics modeling for most engineering fields. The results show that: the permeable layer with a high permeability coefficient during the migration of chromium pollutants has a strong adsorption effect on the heavily polluted part, and it will enhance the lateral diffusion of the polluted area within a short period. Based on the migration model, the intermediate gradient and the symmetrical quadrupole sounding model are built. The variation law of apparent amplitude frequency and apparent resistivity under flat and undulating terrain is analyzed based on the dual frequency IP (Induced Polarization) method. The results show that: The intermediate gradient detection is better than the symmetrical quadrupole sounding in the correspondence between the peak value of apparent amplitude frequency and the valley value of apparent resistivity. The arrangement of the bathymetric measurement point in the center of the projected edge of the pollution field can be a better way to monitor the pollution. Monitoring with the intermediate gradient detection device and the symmetrical quadrupole sounding device creates “multiple peaks” in the curve as it passes through the valley. Arranging the power supply electrodes on the mountain frontiers on both sides of the raised peaks and synthesizes the apparent amplitude frequency and apparent resistivity curves of the pollution field, which can effectively determine the specific orientation of the heavily polluted area of the pollution field. This research makes theoretical additions to the migration characteristics of the Cr pollution field. It provides technical guidance for the real-time monitoring of the pollution field, which is of positive significance for promoting ecological and environmental protection. Full article

(This article belongs to the Special Issue Recent Advances in Exploration Geophysics)

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14 pages, 9957 KiB

Open AccessArticle

Effectiveness of Fiber Optic Distributed Acoustic Sensing (DAS) in Vertical Seismic Profiling (VSP) Field Survey

by Mohamad Hafizal Mad Zahir, Khairul Mustaqim Abdul Aziz, Ahmad Riza Ghazali and Abdul Halim Abdul Latiff

Appl. Sci. 2023, 13(8), 5002; https://doi.org/10.3390/app13085002 - 16 Apr 2023

Cited by 2 | Viewed by 3163

Abstract

The evolution of fiber optic technology in the past few decades has led to significant advancements in various fields, including high-speed and long-distance communication, big data transport, optical imaging, and sensing. However, relatively few studies have examined the use of fiber optic sensors (FOSs) as point and distributed sensors in geophysics. Distributed Acoustic Sensing (DAS) is a widely used method for subsurface imaging and monitoring in wells, specifically in Vertical Seismic Profiling (VSP) surveys. This method allows for detailed analysis of subsurface structures and properties of reservoirs. Four different strategies for deploying FOS cables in DAS VSP are evaluated and compared: cementing behind casing, cable behind inflatable liner, strapping to production tubing, and wireline deployment. Cementing the fiber behind casing is considered the most effective method for coupling with the formation. However, the other methods also have their own advantages and limitations. The fiber cable behind inflatable liner, for example, allows for accessibility to the fiber without affecting the acoustic signal, while strapping the fiber to production tubing can still record DAS signals; tubing noise and signal attenuation from the annular fluid, however, can make it difficult to differentiate from the seismic signal. Nonetheless, this method has the benefit of being simpler to deploy and replace in case of failure. Wireline deployment can pick up some acoustic signals in regions where the cable touches the well wall, but in vertical sections where the cable is not in contact with the wall, the signal is attenuated. Results from pilot tests in a field in Canada are discussed and evaluated, and suggestions for improving the VSP signal are provided. Full article

(This article belongs to the Special Issue Recent Advances in Exploration Geophysics)

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20 pages, 17393 KiB

Open AccessArticle

Direct Inversion Method of Brittleness Parameters Based on Reweighted Lp-Norm

by Yaojie Chen, Shulin Pan, Yinghe Wu, Ze Wei and Guojie Song

Appl. Sci. 2023, 13(1), 246; https://doi.org/10.3390/app13010246 - 25 Dec 2022

Cited by 3 | Viewed by 1211

Abstract

Brittleness is an important factor that indicates shale properties, as well as fracturability, and it can be well-represented using the elasticity parameter Eρ. Seismic inversion allows direct access to the Eρ ofbrittleness parameters. Seismic inversion is a typical ill-posed problem that has an enormous multiplicity of solutions. In order to invert reservoir brittleness parameters more stably and reliably, a direct inversion method for determining brittleness parameters based on a reweighted Lp-norm is proposed, and the reweighted Lp method is introduced to brittleness parameter inversion for the first time. The alternating direction method of multipliers (ADMM) is used to establish the inversion structure and to optimize the objective function in blocks, which effectively improves the convergence speed. We first introduce a reweighted Lp method and establish a pre-stack inversion objective function based on the reweighted Lp method. Then, theoretical simulation data are applied to compare the inversion outcomes of the new method with those of the traditional method, and the effect of the method in this manuscript is verified. Finally, the feasibility of this method is further verified using actual data for experimental analysis. Through an analysis of the experimental results, we find that this method can be well-applied to seismic pre-stack inversion calculation and provides a new direct inversion method for the determination of brittleness parameters for exploration geophysics. Full article

(This article belongs to the Special Issue Recent Advances in Exploration Geophysics)

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22 pages, 13356 KiB

Open AccessArticle

Arbitrary Sampling Fourier Transform and Its Applications in Magnetic Field Forward Modeling

by Shikun Dai, Ying Zhang, Kun Li, Qingrui Chen and Jiaxuan Ling

Appl. Sci. 2022, 12(24), 12706; https://doi.org/10.3390/app122412706 - 11 Dec 2022

Cited by 1 | Viewed by 1326

Abstract

Numerical simulation and inversion imaging are essential in geophysics exploration. Fourier transform plays a vital role in geophysical numerical simulation and inversion imaging, especially in solving partial differential equations. This paper proposes an arbitrary sampling Fourier transform algorithm (AS-FT) based on quadratic interpolation of shape function. Its core idea is to discretize the Fourier transform integral into the sum of finite element integrals. The quadratic shape function represents the function change in each element, and then all element integrals are calculated and accumulated. In this way, the semi-analytical solution of the Fourier oscillation operator in each integral interval can be obtained, and the Fourier transform coefficient can be calculated in advance, so the algorithm has high calculation accuracy and efficiency. Based on the one-dimensional (1D) transform, the two-dimensional (2D) transform is realized by integrating the 1D Fourier transform twice, and the three-dimensional (3D) transform is realized by integrating the 1D Fourier transform three times. The algorithm can sample flexibly according to the distribution of integrated values. The correctness and efficiency of the algorithm are verified by Fourier transform pairs. The AS-FT algorithm is applied to the numerical simulation of magnetic anomalies. The accuracy and efficiency are compared with the standard Fast Fourier transform (standard-FFT) and Gauss Fast Fourier transform (Gauss-FFT). It shows that the AS-FT algorithm has no edge effects and has a higher computational speed. The AS-FT algorithm has good adaptability to continuous medium, weak magnetic catastrophe medium, and strong magnetic catastrophe medium. It can achieve the same as or even higher accuracy than Gauss-FFT through fewer sampling points. The AS-FT algorithm provides a new means for partial differential equation solution in geophysics. It successfully solves the boundary problems, which makes it an efficient and high-precision Fourier transform approach with promising applications. Therefore, the AS-FT algorithm has excellent advantages in solving partial differential equations, providing a new means for solving geophysical forward and inverse problems. Full article

(This article belongs to the Special Issue Recent Advances in Exploration Geophysics)

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