Geophysical Prospecting最新文献

{"title":"Introduction to the special issue on ‘Advanced techniques, methods and applications for an integrated approach to the geophysical prospecting’","authors":"Raffaele Persico","doi":"10.1111/1365-2478.13423","DOIUrl":"10.1111/1365-2478.13423","url":null,"abstract":"","PeriodicalId":12793,"journal":{"name":"Geophysical Prospecting","volume":"71 9","pages":"1693-1695"},"PeriodicalIF":2.6,"publicationDate":"2023-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46882241","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Depth-based correlation analysis between the density of lineaments in the crystalline basement's weathered zones and groundwater occurrences within the Voltaian basin, Ghana","authors":"Theophilus Yaw Amponsah,&nbsp;David Dotse Wemegah,&nbsp;Sylvester Kojo Danuor,&nbsp;Eric Dominic Forson","doi":"10.1111/1365-2478.13422","DOIUrl":"10.1111/1365-2478.13422","url":null,"abstract":"<p>Geological structures have been shown by studies to have influence on the occurrence, storage and transportation of groundwater. Understanding the structural network of an area unearths a deep insight into the groundwater dynamics of the area. A geological structural analysis was carried out to reveal the geological structural network of Ghana's Voltaian basin. Using aeromagnetic data, structural density models were generated using the Center for Exploration Targeting grid analysis technique for two depth ranges (that is up to 100 m and 300 m) over the Voltaian basin. The total length of geological structures (lineaments) delineated at depths up to 100 m and 300 m were more than 5000 km and more than 8000 km, respectively. Given this, the study area was observed to be structurally dense at each of the aforementioned depths. The structural density models were discretized into five classes (very low, low, moderate, moderately high and very high regions), each of which was evaluated to determine their spatial association with known locations of groundwater occurrences within the study area using the frequency ratio technique. Frequency ratio results for both structural density models derived at 100 m and 300 m depths show the existence of a strong correlation between high structural density model classes and the known groundwater occurrences. The structural density models were further evaluated using the receiver operating characteristics curve. The area under the receiver operating characteristics curve scores indicates that, although both structural density models showed very good performance (with receiver operating characteristics scores greater than 0.7), the 300-m depth structural density model performed better than the structural density model generated at a depth of 100 m (with their receiver operating characteristics scores being 0.721 and 0.715, respectively). The obtained results corroborate with literature assertion that groundwater occurrence within the Voltaian basin is mainly associated with structural features. It is expected that the outputs of this study would guide future groundwater exploration programmes within the study area.</p>","PeriodicalId":12793,"journal":{"name":"Geophysical Prospecting","volume":"72 2","pages":"497-511"},"PeriodicalIF":2.6,"publicationDate":"2023-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46473212","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Understanding total variation regularization: Why can it recover dipping structures?","authors":"Jiajia Sun,&nbsp;Dominique Fournier","doi":"10.1111/1365-2478.13417","DOIUrl":"10.1111/1365-2478.13417","url":null,"abstract":"<p>Many geological features of scientific and/or economic interest have structural orientations that are neither horizontal nor vertical. Being able to recover such dipping structures from geophysical inversions is, therefore, important. Different regularization strategies have been proposed to help recover dipping structures. One notable example is total variation. However, there seems to be a lack of understanding within the geophysical community regarding why total variation regularization allows dipping structures to be recovered, whereas <i>L</i>₁ norm regularization does not. In this paper, we compare these two regularization strategies from an optimization point of view using two simple block models. We also perform three-dimensional inversions using a synthetic example and a field data example involving gravity gradient data to demonstrate the resolving power of total variation in potential field data inversion.</p>","PeriodicalId":12793,"journal":{"name":"Geophysical Prospecting","volume":"72 2","pages":"424-434"},"PeriodicalIF":2.6,"publicationDate":"2023-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46572757","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ultrasonic S-wave indirectly detects the very narrow gap at contact of grains: Glass beads and Ottawa sands","authors":"Guangquan Li,&nbsp;Xiang Li,&nbsp;Yuchao Wang","doi":"10.1111/1365-2478.13421","DOIUrl":"10.1111/1365-2478.13421","url":null,"abstract":"<p>Considerably different from sandstones, sands have point-like contact of grains. In contrast, sandstones have cementation between grains, which has diminished the very narrow gap at contact of grains. In this paper, ultrasonic S-wave in brine-saturated glass beads and Ottawa sands is used to detect the very narrow space at contact of grains. The data of the dry beads/sands and brine are inputted into Biot theory to yield phase velocity of the saturated beads/sands. By fitting the theoretical velocity with the ultrasonic measurement, phase velocity, the quality factor and S-wave permeability are determined as functions of frequency. The predicted ultrasonic quality factors appear to be very close to that of water-saturated Berea sandstone. Our previous study showed that for Berea sandstone, the low-frequency S-wave permeability is approximately half of Darcy permeability. However, for glass beads and Ottawa sands, the S-wave permeabilities at low frequencies are one-order magnitude lower than Darcy permeabilities. This well shows that S-wave permeability of the beads/sands is associated with the very narrow gap at contact of grains which is successfully detected by ultrasonic S-wave in the indirect way.</p>","PeriodicalId":12793,"journal":{"name":"Geophysical Prospecting","volume":"72 2","pages":"484-496"},"PeriodicalIF":2.6,"publicationDate":"2023-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47231961","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Elastic full-waveform inversion based on the double-cross-shaped discrete flux-corrected transport","authors":"Jinli Li,&nbsp;Jianggui Zhu,&nbsp;Yingming Qu,&nbsp;Zhenjie Yang,&nbsp;Zhenchun Li","doi":"10.1111/1365-2478.13420","DOIUrl":"10.1111/1365-2478.13420","url":null,"abstract":"<p>Multi-parameter elastic full-waveform inversion is a technique that utilizes both P- and S-waves of observed seismic data to produce high-resolution velocity and density models with accurate amplitude information by minimizing the discrepancy between the predicted and observed multi-component data. However, due to the nonlinear nature of the multi-parameter inverse problem, elastic full-waveform inversion is prone to local minima and ‘cycle-skipping’. To overcome these challenges, this paper proposes an elastic full-waveform inversion method that incorporates a double-cross-shaped discrete flux-corrected transport. This method additionally introduces diffusion fluxes in two diagonal directions, which helps to capture low-frequency information in the observed seismic data and maintain forward modelling stability. Multi-scale inversion is achieved by gradually decreasing the diffusion flux correction parameter. Numerical experiments on both two typical models and a field data example demonstrate the effectiveness of the proposed elastic full-waveform inversion method based on the double-cross-shaped discrete flux-corrected transport in generating high-precision velocity and density models.</p>","PeriodicalId":12793,"journal":{"name":"Geophysical Prospecting","volume":"72 2","pages":"468-483"},"PeriodicalIF":2.6,"publicationDate":"2023-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46961597","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ergodic sampling: Acquisition design to maximize information from limited samples","authors":"Mengli Zhang,&nbsp;Yaoguo Li","doi":"10.1111/1365-2478.13419","DOIUrl":"10.1111/1365-2478.13419","url":null,"abstract":"<p>Data acquisition using equal spacing has been a standard practice in geophysics. The dense uniform sampling derived from Nyquist–Shannon sampling includes redundant samples, and it is sufficient but not necessary to adequately record target signals. We propose an ergodic sampling, which avoids the redundant samples in the dense uniform sampling and possesses the ability to capture the sufficiently similar information content as does Nyquist sampling. Ergodicity means that a key part of the system can represent the average performance of the entire system. Our ergodic samples are a critical subset of dense uniform samples and can represent the full uniform Nyquist samples. To find such a critical subset, we first examine the properties of different sampling patterns, including the sampling interval distribution, sampling angle distribution, areal sample density, and resolution in the spectral domain. We define the information sampling ability of sampling patterns based on these properties. The concept of information sampling ability that we have proposed serves as the criterion to compare different sampling patterns and assess their sampling performances. The sampling patterns with the same information sampling ability have the same capability to gather information, even though the appearance of sampling patterns may be different. We formulate an optimization problem to find this critical subset of sample locations, which has the fewest number of samples but has a similar information sampling ability as that of the desired dense uniform samples. This critical subset is irregularly located, has the optimized properties and forms the ergodic sampling pattern. We define this process of sampling design and associated understanding as the ergodic sampling. Ergodic sampling can be applied to gain two major benefits in practice. First, this approach can save a significant number of samples. We demonstrate ergodic sampling using one-dimensional synthetic data and a two-dimensional field geophysical dataset. The simulations confirm that, compared with other sampling strategies, ergodic sampling can use fewer samples to acquire the same amount of information, so that we can save cost. Alternatively, with the same budget, we can use the same number of samples through ergodic sampling to acquire more information. The new ergodic sampling can lead to a new generation of economic and efficient geophysical data acquisition, which could assist in increasing the discovery rate in resource exploration, tackling more earth science problems with a limited budget and can also benefit the environment in the process by reducing the invasiveness in potentially sensitive regions.</p>","PeriodicalId":12793,"journal":{"name":"Geophysical Prospecting","volume":"72 2","pages":"435-467"},"PeriodicalIF":2.6,"publicationDate":"2023-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/1365-2478.13419","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48472530","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Gravity inversion by second order approximation applied to the Styrian Basin (Austria)","authors":"Harald Granser","doi":"10.1111/1365-2478.13418","DOIUrl":"10.1111/1365-2478.13418","url":null,"abstract":"<p>An approximative second order gravity inversion scheme by a truncated power series expansion is applied to derive the thickness of the Neogene, mostly clastic, sedimentary section of the Styrian Basins in South–East Austria, which are sub-basins of the Pannonian Basin System. These sub-basins with a derived thickness of up to 4 km are of interest for geothermal exploitation because of the increased geothermal gradient and heat flow observed in the Pannonian Basin in general and a geothermal gradient of 4°–5°/100 m measured in some wells in the Styrian Basin. The Styrian Basin also has been an area for hydrocarbon exploration in the past 50 years, with oil and gas show encountered in several exploration wells and one sub-commercial gas discovery. The Miocene and Plio–Pleistocene volcanism in the Styrian Basin caused by Miocene crustal thinning is discussed in terms of the influence to the gravity inversion taking the aeromagnetic field into account. The volcanism is of relevance for the geothermal prospectivity but poses problems for the single layer-based gravity inversion scheme. Results are discussed from a computational side comparing observed and calculated gravity fields but also the match with well data is discussed. In terms of gravity inversion methodology, the presented can be viewed as an approximative fast-track approach.</p>","PeriodicalId":12793,"journal":{"name":"Geophysical Prospecting","volume":"72 2","pages":"791-808"},"PeriodicalIF":2.6,"publicationDate":"2023-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/1365-2478.13418","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41462926","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Microseismic wavefield modelling in anisotropic elastic media using integral equation method","authors":"Ujjwal Shekhar,&nbsp;Morten Jakobsen,&nbsp;Einar Iversen,&nbsp;Inga Berre,&nbsp;Florin A. Radu","doi":"10.1111/1365-2478.13416","DOIUrl":"10.1111/1365-2478.13416","url":null,"abstract":"<p>In this paper, we present a frequency-domain volume integral method to model the microseismic wavefield in heterogeneous anisotropic-elastic media. The elastic wave equation is written as an integral equation of the Lippmann–Schwinger type, and the seismic source is represented as a general moment tensor. The actual medium is split into a background medium and a scattered medium. The background part of the displacement field is computed analytically, but the scattered part requires a numerical solution. The existing matrix-based implementation of the integral equation is computationally inefficient to model the wavefield in three-dimensional earth. An integral equation for the particle displacement is, hence, formulated in a matrix-free manner through the application of the Fourier transform. The biconjugate gradient stabilized method is used to iteratively obtain the solution of this equation. The integral equation method is naturally target oriented, and it is not necessary to fully discretize the model. This is very helpful in the microseismic wavefield computation at receivers in the borehole in many cases; say, for example, we want to focus only on the fluid injection zone in the reservoir–overburden system and not on the whole subsurface region. Additionally, the integral equation system matrix has a low condition number. This provides us flexibility in the selection of the grid size, especially at low frequencies for given wave velocities. Considering all these factors, we apply the numerical scheme to three different models in order of increasing geological complexity. We obtain the elastic displacement fields corresponding to the different types of moment tensor sources, which prove the utility of this method in microseismic. The generated synthetic data are intended to be used in inversion for the microseismic source and model parameters.</p>","PeriodicalId":12793,"journal":{"name":"Geophysical Prospecting","volume":"72 2","pages":"403-423"},"PeriodicalIF":2.6,"publicationDate":"2023-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/1365-2478.13416","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44075062","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Introduction to the special issue on “mineral exploration and mining geophysics”","authors":"Alireza Malehmir,&nbsp;Gordon Cooper,&nbsp;Musa Manzi,&nbsp;Andrei Swidinsky,&nbsp;Umair Bin Waheed","doi":"10.1111/1365-2478.13414","DOIUrl":"10.1111/1365-2478.13414","url":null,"abstract":"NoneThis article is protected by copyright. All rights reserved","PeriodicalId":12793,"journal":{"name":"Geophysical Prospecting","volume":"71 7","pages":"1073-1076"},"PeriodicalIF":2.6,"publicationDate":"2023-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48025853","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Three-axis borehole gravity monitoring for CO2 storage using machine learning coupled to fluid flow simulator","authors":"Taqi Alyousuf,&nbsp;Yaoguo Li,&nbsp;Richard Krahenbuhl,&nbsp;Dario Grana","doi":"10.1111/1365-2478.13413","DOIUrl":"10.1111/1365-2478.13413","url":null,"abstract":"<p>The field of geophysics faces the daunting task of monitoring complex reservoir dynamics and imaging carbon dioxide storage up to several decades into the future. This presents numerous challenges, including sensitivity to parameter changes, resolution of obtained results and the cost of long-term deployment. To effectively store CO₂ subsurface, it is necessary to monitor and account for the injected CO₂. The gravity method provides several advantages for CO₂ monitoring, as changes in fluid saturation correspond directly and uniquely to observed density changes. Three-axis borehole gravity has demonstrated significant promise as a next-generation tool for reliably monitoring reservoir dynamics across a range of depths and sizes. However, the gravity inverse problem is highly ill-posed, necessitating regularization that incorporates prior knowledge. To address this issue, we propose using a feed-forward neural network, a machine learning method, to invert time-lapse three-axis borehole gravity data and monitor CO₂ movement within a reservoir. By training the neural network on models that analyse changes in density and corresponding gravity responses resulting from perturbations made to the reservoir model, we can create scenarios that train the algorithm to identify unexpected CO₂ migration in addition to the normal movement of CO₂. Our method is demonstrated using reservoir models for the Johansen formation in offshore Norway. We convert reservoir saturation models into density changes and generate their corresponding three-axis gravity data in a set of boreholes. Our results show that the developed machine learning inversion algorithm has high reliability and resolution for imaging density change associated with CO₂ plumes, as demonstrated in the Johansen reservoir models utilized by the simulator. We also investigate machine learning inversion using regularization parameters and show that it is robust, with a strong tolerance for higher levels of noise. Our study demonstrates that the developed machine learning algorithm is a powerful tool for inverting three-axis borehole gravity data and monitoring the migration and long-term storage of injected CO₂.</p>","PeriodicalId":12793,"journal":{"name":"Geophysical Prospecting","volume":"72 2","pages":"767-790"},"PeriodicalIF":2.6,"publicationDate":"2023-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45664759","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}