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- Volume 71, Issue 4, 2023
Geophysical Prospecting - Volume 71, Issue 4, 2023
Volume 71, Issue 4, 2023
- ISSUE INFORMATION
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- ORIGINAL ARTICLES
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The spectral stacking method and its application in seismic data resolution increase
Authors Carlos Claudino and Wagner Moreira LupinacciAbstractPreconditioning is a practice adopted in the treatment of seismic data and, when properly applied, favours a resolution increase. However, retrieving all the frequency contents is still a challenge to overcome. Techniques to improve the seismic resolution should preserve the existing relations in the distribution of seismic events. Otherwise, it may cause undesirable situations, from the degradation of the signal‐to‐noise ratio to the creation of false events, leading to errors of interpretation. We developed a method called spectral stacking, which makes use of circular convolution in the frequency domain to extend frequency content, preserving the distribution of seismic events without adding artefacts. As an application of the spectral stacking method, we create a sharpening filter that resolves layers under Ricker's criterion. In addition, the sharpening filter preserves the amplitude using a variable‐window correction based on the local minima of the absolute values of amplitude. We validated our proposed method in synthetic and real tests. The results showed that the sharpening filter obtained a resolution increase, providing a sharper image of the seismic section.
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Steeply dipping structure imaging with prismatic waves incorporating wavefield decomposition
Authors Zheng Wu, Yuzhu Liu and Jizhong YangAbstractPrismatic waves in seismic data can effectively delineate steeply dipping subsurface structures. However, the conventional migration of prismatic wave either requires the exact location of basement reflectors embedded in the accurate migration velocity model or the explicit isolation of prismatic wave from the recorded data to avoid crosstalk artefacts caused by mistaken imaging of primary reflections. Neither of the requirements is a trivial task for field data application with complicated subsurface structures. To image steeply dipping structures with an accurate but smooth enough migration velocity and without the need to extract prismatic waves from the recorded data, we analyse the prismatic imaging condition based on wavefield decomposition. In the up‐ and down‐going wavefield decomposition, the prismatic imaging condition can effectively remove the high‐wavenumber artefacts with incorrect polarity. However, the expected steeply dipping image is buried in low‐wavenumber noises. In contrast, the prismatic imaging condition based on left‐ and right‐going wavefield decomposition can accurately isolate the artefacts induced by the mistaken migration of primary waves from the steeply dipping interfaces in the image and is free of low‐wavenumber noises. Based on this analysis, we develop a reverse time migration workflow using the modified prismatic imaging condition to depict steeply dipping structures: First, we use the primary imaging condition based on the up‐and‐down‐going wavefield decomposition to obtain an image that can approximate the basement reflectors. Then, we use the modified prismatic imaging condition based on left‐ and right‐going wavefield decomposition to recover the steep interfaces. Finally, a combined subsurface image containing both basement reflectors and faults or steeply dipping structures is generated. We verify the feasibility and robustness of the modified prismatic imaging condition based reverse time migration method for delineating steeply dipping structures using several synthetic tests.
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Seismic migration in viscoacoustic vertical transversely isotropic media using a pure qP wave equation
Authors Han Wu, Chengyu Sun and Xiaofan DengAbstractSeismic anisotropic attenuation and anisotropic velocity exist widely in the earth's interior and have a great influence on the propagation of seismic waves. Ignoring the effects of attenuation anisotropy may lead to amplitude imbalance or noise in reflection seismic imaging, thus reducing the quality of the imaging results. In order to incorporate attenuation anisotropy into imaging methods and explore its effect on imaging, based on a novel two‐way pure qP wave equation in viscoacoustic vertical transversely isotropy media, we propose the corresponding reverse time migration and least‐squares reverse time migration method. Both imaging methods can accurately obtain subsurface structure information, especially the least‐squares reverse time migration has the potential to compute accurate subsurface reflectivity. In this paper, we first introduce the pure qP wave equation in viscoacoustic vertical transversely isotropy media. As the equation is derived from the complex dispersion relation of P wave, wave propagation can be simulated without interference of SV wave and limitation of anisotropic parameters. Then, we derive the corresponding linearized wave equation and adjoint gradient for updating the imaging result. Finally, using two synthetic models, we demonstrate the effectiveness of the imaging method and discuss the effect of attenuation anisotropy on seismic imaging.
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Sandstone detection using three‐term amplitude variation with offset projection: A case study
More LessAbstractSeismic amplitude variation with offset projection is widely used in the oil and gas industry to extract information contained in amplitude variation with offset responses. Traditional two‐term amplitude variation with offset projection, based only on intercept (A) and gradient (B), has been used in various ways, including hydrocarbon detection and the estimation of target properties such as water saturation. Three‐term amplitude variation with offset projection, in which A, B and curvature (C) are blended using two projection angles (χ and ψ), can also be used for the same purposes and has some advantages over the two‐term methods. The effectiveness of the three‐term amplitude variation with offset projection in the detection of sandstone has been investigated using field data. A sandstone detection workflow is proposed, which includes (1) defining the target attribute, (2) optimizing projection angle in the χ–ψ analysis plane painted with the target attribute and (3) confirming/refining the selected projection angle using the two‐term amplitude variation with offset projection‐C cross‐plot. The impact of anisotropy is taken into consideration, and the sandstone index is introduced as the target attribute. The sandstone detection workflow was applied for both synthetic and field data, which illustrates that three‐term methods offer an important perspective on noise in the amplitude variation with offset attributes: Noise in the third term is correlated with noise in the other terms so that including C can actually suppress noise to some extent, even if C looks unusable. Moreover, two‐term amplitude variation with offset projections are a subset of three‐term amplitude variation with offset projections; therefore, if C adds no information, this fact is revealed as the worst‐case outcome in the three‐term analysis; inclusion of C will never degrade results and there is no reason to exclude C a priori.
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- REVIEW ARTICLES
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Analysis of the acoustic seismic energy flux propagated through synthetic models formed by different structures
More LessAbstractSeismic‐acoustic wavefield propagations on synthetic 2D models formed by different structural backgrounds are analysed in four test cases. These test cases were carried out employing staggered‐grid finite differences and absorbing boundaries of the convolutional perfectly matched layers type, which allowed analysing in a time of 7.0 s: (a) the seismic‐acoustic wavefield behaviour, (b) the kinetic seismic energy flux and potential seismic energy flux and (c) the energy differences (ΔKEF/ΔPEF) due to each type of proposed structure. In the first two test cases, a relationship was observed between average kinetic seismic energy flux/potential seismic energy flux values and the different structural densities ε of each synthetic model, which were formed by a similar type of structure (fractures). The average kinetic seismic energy flux values increased when ε decreased, whereas the average potential seismic energy flux values decreased when ε also decreased. The largest ΔKEF/ΔPEF values were observed for those models with more structures, reaching up to 0.2 × 108/0.21 × 108 J/m2 in the first test case and up to 1.95 × 108/1.91 × 108 J/m2 in the second test case. Meanwhile, for those models with less number of structures was 0.04 × 108/0 J/m2 in test case 1 and 0.26 × 108/0.61 × 108 J/m2 in test case 2. In the third test case, a relationship was observed between the average potential seismic energy flux values and the ε values, but not with the average kinetic seismic energy flux values, the synthetic models of which were formed by different types of structures (lobes and fractures under different shapes and sizes). The kinetic seismic energy fluxes were more affected by structures closer to each other than by those further apart. Meanwhile, the potential seismic energy fluxes were more affected by larger structures, maintaining a relationship with the seismic frequency and wavelength. The largest ΔKEF/ΔPEF values reached up to 3.42 × 108/3.24 × 108 J/m2 in model with the highest ε value, whereas up to 0.49 × 108/0.67 × 108 J/m2 in the model with the lowest ε value. In the fourth test case, similar types of structures (fractures) were analysed under different orientations in each model. The kinetic seismic energy fluxes/potential seismic energy fluxes were higher in the model formed by better‐oriented structures or parallel with respect to the propagation direction of the seismic‐acoustic wavefield. These energy differences between each test case show how not only the number of structures in a model and the ε values influenced the seismic‐acoustic wavefield and the kinetic seismic energy flux/potential seismic energy flux, but also the structural aspects, the intrinsic elastic properties (e.g. the density used in structures), location (separation between structures) and orientation of structures.
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- ORIGINAL ARTICLES
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Facies‐constrained transdimensional amplitude versus angle inversion using machine learning assisted priors
Authors Arnab Dhara, Mrinal K. Sen and Reetam BiswasABSTRACTWe present a methodology for seismic inversion that generates high‐resolution models of facies and elastic properties from pre‐stack data. Our inversion algorithm uses a transdimensional approach where, in addition to the layer properties, the number of layers is treated as unknown. In other words, the data itself determine the correct model parameterization, that is, the number of layers. The reversible jump Markov Chain Monte Carlo method is an effective tool to solve such transdimensional problems as it generates models of reservoir properties along with uncertainty estimates. However, current implementations of the reversible jump Markov Chain Monte Carlo algorithms do not account for the non‐Gaussian and multimodal nature of model parameters. The target elastic reservoir properties generally have multimodal and non‐parametric distribution at each location of the model. The number of modes is equal to the number of facies. Taking these factors into account, we extend the reversible jump Markov Chain Monte Carlo algorithm to simultaneously invert for discrete facies and continuous elastic reservoir properties. The proposed extension to the algorithm iteratively samples the facies, by moving from one mode to another, and elastic properties by sampling within the same mode. The integration of facies classification within the inversion reduces non‐uniqueness, improves convergence speed and produces geologically consistent results. The workflow uses machine learning to generate probabilistic priors for the model parameters. We validate our approach by applying it to a synthetic dataset generated from a well log with two facies and then to a complex synthetic two‐dimensional model involving three facies having overlapping elastic property distribution. Finally, we apply our algorithm to a field dataset acquired over an unconventional reservoir. Our algorithm demonstrates the usefulness of incorporating facies information in seismic inversion and also the feasibility of inverting for facies from seismic data.
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Acoustic field characteristics of seismic surveys in the shallow water environment of the Bohai Sea
Authors Dong Zhang, Zhilei Sun, Xilin Zhang, Huaishan Liu, Yunbao Sun, Hong Cao, Wei Geng, Bin Zhai, Gang Dong, Ang Li and Di LuoAbstractAir gun arrays are designed to generate strong energy pulses of less than 100 Hz for offshore oil and gas exploration. In shallow seas, due to the directivity of air gun arrays, the complex propagation conditions and the limitations of acquisition methods, it is difficult to accurately evaluate the spatial time and frequency transmission characteristics of airguns. To alleviate the existing lack of knowledge about the transmission characteristics of air gun pulses in the shallow waters of the Bohai Sea, we analysed three‐dimensional ocean bottom cable seismic data collected during a seismic survey in the Bohai Sea, China, in June 2017, which were used to evaluate the reception level, frequency domain characteristics and spatial distribution characteristics within a 5.55 × 5.575 km area. The results showed that in shallow water, multipath propagation causes downfrequency chirplike sounds and an increased sound field. Within 0.3 km, the transmission model follows a cylindrical diffusion, and the sound loss rate decreases as the transmission distance increases until reaching 8 km. Signal capture by the sound channel results in a high transmission loss frequency band, whereas multimode interference weakens the transmission loss. The gun array directivity and the transmission channel are the two main factors affecting the acoustic field. This research provides an improved understanding of the acoustic field of airguns in the Bohai Sea, which can benefit the acoustic modelling of air gun arrays, the design of future seismic exploration projects and the conservation of marine life.
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Application of deconvolution interferometry to receiver ghost reflection in vertical cable seismic survey
Authors Linfei Wang, Zhong Wang, Huaishan Liu, Jin Zhang, Quanchen Jia and Duowei MeiAbstractMarine vertical cable seismic is to probe targets near the submarine with use vertical hydrophone array suspending in deep sea water. Despite imaging of primary reflections from vertical cable seismic data can provide seismic profiles with high resolution, its submarine illumination is much narrower than that of conventional towed‐streamer seismic owing to the irregular geometry. In view of the fact that imaging of multiples can provides better subsurface illumination with fine resolution, we present a strategy for imaging of receiver ghost reflections from vertical cable seismic data, based on seismic interferometry by deconvolution. This method can convert first‐order receiver ghosts into virtual primaries from the towed‐streamer data without velocity model and source‐receiver position. We illustrate the deconvolution interferometry for the receiver ghost reflections with the real vertical cable seismic data in Shenhu area, South China Sea and further obtain virtual primary reflections. Finally, we use these virtual primaries to successfully construct a stacked image and obtain a post‐stack migration image with conventional seismic data process method. This stacked and migrated image significantly extends the submarine illumination with higher resolution and it is useful in characteristics recognition of hydrate‐bearing sediments and free gas.
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Least‐squares reverse time migration with flux‐corrected transport technique
Authors Liang Chen, Jianping Huang, Cheng Song and Jiale HanAbstractDue to high computational costs and memory requirements, it is necessary to use coarse grids for least‐squares reverse time migration when processing large‐scale field data. According to the dispersion relation, strong numerical dispersion will occur in least‐squares reverse time migration images when the migration velocity of the shallow strata is low, reducing the resolution of the migration results. To overcome this shortcoming, we propose new least‐squares reverse time migration implementation method with a modified flux‐corrected transport technique. This algorithm involves two main steps: obtain an appropriate calibration parameter for flux‐corrected transport through forward modelling and perform least‐squares reverse time migration using flux‐corrected transport. We remove the non‐linear processing from conventional flux‐corrected transport algorithm often used in computational fluid dynamics based on the assumption that the seismic wavefield is relatively continuous and smooth without strong ripples, which makes it possible to apply flux‐corrected transport to least‐squares reverse time migration without increasing too much computation complexity. To suppress the numerical dispersion more effectively, the diffusion fluxes along the diagonal direction are added to flux‐corrected transport. Numerical tests on synthetic data and field data illustrate that compared to the conventional least‐squares reverse time migration method, the proposed method produces images with fewer migration artefacts, more accurate amplitudes and faster convergence speed on the coarse grids.
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A logical error in Gassmann poroelasticity
By Leon ThomsenAbstractThe well‐known ‘Biot–Gassmann’ formula for the undrained compressibility of porous rock is in error. The error was introduced by Gassmann (implicitly revising earlier work by Biot) and results in an expression which is simpler than Biot's corresponding expression, containing only one material parameter (KS) in place of Biot's two (H and R). The error occurred when Gassmann applied a hydraulically open theorem to a hydraulically closed system, thus violating the assumptions of the undrained compressibility. Similar errors have marred the many subsequent derivations of Gassmann's result. Biot's (prior) correct formulation was subsequently rederived exactly (in different notation) by Brown and Korringa, and separately by Rice and Cleary. The inconsistency between Gassmann and these three analyses is caused by Gassmann's logical error, rather than by the issue of solid micro‐homogeneity. The additional parameter may be experimentally determined via the ‘Skempton B‐coefficient’ (the ratio of fluid pressure to external pressure in an undrained quasi‐static compression test). This correction resolves a long‐established inconsistency between Gassmann's result and effective‐medium theory. A new generation of experimentation is required to determine the systematics of the magnitude of the correction to the Gassmann result.
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A novel approach for fracture porosity estimation of carbonate reservoirs
More LessAbstractThe quality of carbonate reservoirs is linked to their rock properties and surrounding stress settings which can play a vital role in their production optimization and development programs. Imposing various stresses can increase porosity and permeability by creating joints and cracks across the rock mass. Therefore, developing methods to identify and accurately evaluate fractures in carbonate reservoirs is very significant in reservoir characterization. To deal with this necessity, we developed a fracture porosity estimation method using empirical and analytical solutions based on the wireline data considering stress conditions. The proposed methodology was applied to a carbonate reservoir as the case study. As fracture porosity is sensitive to stress, experimental tests were conducted on the core samples using triaxial hydrostatic tests. These tests are needed to simulate reservoir conditions to investigate the relationships between fracture volume fraction and the applied stress. A substantial porosity loss was observed during the hydrostatic test, which can be linked to the crack porosity closure. The reliability of our results was validated by thin section, computed tomography–scan images, velocity deviation method, elastic boundary laws, and image logs. Eventually, we introduced an equation to estimate in situ fracture porosity from the relationship between porosity and effective confining pressure. We verified the repeatability and generality of our proposed methodology using a blind well, and the results indicate a comparable level of accuracy. Our findings are applicable for estimating crack porosity for rock physics modelling purposes of detecting fracture zones in the absence of image logs and core data. Moreover, by calibrating and optimizing the constant parameters in our proposed relationship, one may further estimate crack density in any other given carbonate reservoirs.
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Estimation of seismic attenuation for reservoirs mapping and inverse Q‐filtering: An application on land seismic data
Authors Abdullah Alshangiti and Hua‐Wei ZhouAbstractSeismic attenuation values based on inverse Q‐filtering are useful in enhancing seismic data resolution for quantitative interpretation. However, as field attenuation estimations are often contaminated by noise and overburden effects, an inverse Q‐filter may reduce the signal‐to‐noise ratio. To help reservoir mapping with seismic resolution enhancement, we use well logs and surface seismic data to estimate the attenuation of a depth interval composed of several carbonate oil reservoirs onshore the Arabian Peninsula. From applying a prestack Q inversion on τ–p gathers from a large 3D seismic survey, the estimated effective attenuation values show spatially coherent patterns, likely corresponding to changes in the petrophysical and fluid properties. The patterns of the estimated effective attenuation values correlate considerably with the anticline geometry, with higher values on its crest than its flanks. The small percentage of the negative effective attenuation values indicates that the apparent attenuation and overburden effects are insignificant. At well locations, the effective attenuation values show a good correlation with the average porosity of the main reservoir, verifying that they are related to changes in petrophysical properties in the analysis interval. We propose an extended inverse Q‐filter with two additional parameters to make it more robust and flexible and test it with synthetic and field datasets. We estimate a multiple‐scattering attenuation value from well logs and use it in the proposed filter for the field dataset. The compensation for the multiple‐scattering effects suppresses the overprints of the data components unrelated to the target interval, hence benefitting the quantitative data interpretation.
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Automating seismic‐well tie via self‐supervised learning
Authors Haibin Di and Aria AbubakarAbstractAs an essential process in subsurface interpretation, seismic‐well tie aims at calibrating the well measurements in depth domain with the seismic records in time domain for reliable reservoir mapping and modelling. Such a process usually requires massive manual efforts, primarily extracting source wavelets to synthesize seismograms from well measurements and stretching/squeezing synthetic seismograms to match actual seismic signals, and thus becomes time‐consuming and labour intensive with the amount of wells expanding in a field. This paper formulates the seismic‐well tie problem from the perspective of computer vision and, considering the lack of manually prepared training labels in most of real projects, proposes automating it by a self‐supervised workflow of two key components. The first component is to extract time‐variant wavelets in the target interval using a dual‐task autoencoder, which is optimized by maximizing the spectrum similarity between the extracted wavelet and the actual seismic. The second component is to estimate the corresponding time‐shift between a pair of the synthetic seismogram and the actual seismic using a flow net, which is trained by a pseudo dataset derived from the actual well measurements. More specifically, the data generation consists with defining one‐dimensional time‐shift curves to warp the original less accurate time‐depth relationships and then synthesizing the corresponding seismograms based on the convolutional model at all available wells. When turning to the stage of inference at a target well, the proposed workflow automatically extracts a representative wavelet, generates the corresponding synthetic seismogram from the original time‐depth relationship and estimates the time‐shift curve necessary for revising the original time‐depth relationship that would lead to an optimal tying with the actual seismic at the well. The proposed workflow is tested on two field datasets, and both results demonstrate improved tying over traditional methods such as statistical wavelet extraction and dynamic time warping.
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A generalized source‐distance semi‐automatic interpretation method for potential field data
More LessAbstractSource‐distance methods can be used to locate the position and depth of potential field sources. Existing analytic signal amplitude‐based methods are generalized here so that they are more flexible in the orders of analytic signal amplitude that they use. This not only gives benefits with respect to their robustness against noise and interference, but if the methods are applied several times using different orders then the repeatability of the results can be used to assess their reliability. Some of the proposed methods require the structural index of the source to be specified, whereas others do not. The methods are compared with the Euler deconvolution and Tilt‐Euler methods and are demonstrated on synthetic data and on aeromagnetic data from South Africa.
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- RESEARCH NOTE
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How low can you go: An investigation of depth sensitivity and resolution using towed marine controlled‐source electromagnetic systems
Authors Roslynn B. King and Steven ConstableAbstractUnderstanding the depth of investigation for electromagnetic and electrical methods is important in experimental design and for interpreting inversions. Many studies have defined the depth of investigation for electromagnetic sounding methods, but none have included continuously towed controlled‐source electromagnetic methods. Nodal controlled‐source electromagnetic surveys using ocean‐bottom electromagnetic receivers have generally been found to have a depth of investigation limited to about half the maximum source‐receiver spacing, but experience using continuously towed arrays suggests sensitivity to targets at depths approaching the source‐receiver spacing. We test this on two‐dimensional synthetic data using two methods. A rigorous approach is to re‐invert data as a highly conductive or resistive basement is included at successively shallower depths. When the data misfit becomes unacceptably high we can conclude that the maximum depth of inference has been passed. Rather than rely on overall misfit, we note that it is more realistic to preferentially examine those data most sensitive to largest depths (longest offsets and lowest frequencies). A more practical approach is to determine the depth at which a conductivity contrast can be imaged by inversion, noting that knowledge of a contrast is geologically useful even if the actual conductivities cannot be recovered. Both approaches confirm that the increased data density of towed electromagnetic systems at longest offset increases the depth of investigation to about the maximum offset distance.
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- ORIGINAL ARTICLES
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MEMS‐based 3‐C borehole gravimeter development
Authors Gang Yu, Fangjing Hu, Liangcheng Tu, Guo Zhao and Juan ChenAbstractA micro‐electro‐mechanical‐based 3‐C borehole gravimeter has been developed in China for mineral and hydrocarbon exploration. The 3‐C borehole gravimeter is composed of a three‐axis gravity sensor chip based on a deep silicon etching technique, high‐precision capacitive displacement sensing and weak signal detection circuitry. The gravity‐sensing chip is a silicon‐based integrated spring‐mass block system. Silicon wafer is etched by the micro‐nanofabrication technique to form a high collimation groove. The size of the gravity‐detecting mass block in the sensitive element plays a decisive role in the thermal noise level of the instrument. Deep silicon processing technique can produce a thicker silicon mass block (500 μm), which can obtain a larger mass block in the same area compared with the traditional silicon surface processing technique (10–100 μm). The out diameter of the final tool is 50 mm with 10,000 mGal measurement range, 155°C temperature and 100 MPa pressure rating. Apart from the 3‐C micro‐electro‐mechanical gravity sensor, a 3‐C fluxgate magnetic sensor is also integrated into the downhole tool. This allows us to measure both 3‐C gravity field and 3‐C magnetic field downhole simultaneously and conduct joint inversion of both the downhole 3‐C gravity and 3‐C magnetic data during the data processing stage. The prototype tool was tested in a borehole up to 850 m depth, and the 3‐C gravity sensor inside the tool can measure the vibration of the environment during the stationary measurement downhole. The first test data set shows repeatability near 800 m depth, which verifies the adaptability of the micro‐electro‐mechanical‐based gravimeter to the down instrument environment.
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Combined analysis of resistivity and induced polarization tomography for 3D modelling and preliminary volume estimation of the possible gold mineralization zones in the Simi locality, Adamawa, Cameroon
AbstractThe present study attempts to combine direct current and induced polarization methods for 3D geological modelling and preliminary volume estimation of gold mineralization targets in the Simi locality, Adamawa, Cameroon. To begin, resistivity and chargeability data were collected along seven profiles oriented in N150E using the electrical tomography technique. A geological investigation was also carried out and allowed in addition to the geological formations to highlight the existence of gold mineralization in the study area. The interpretation of the inversion results was done by taking into consideration the geological field data and the existing resistivity charts. The 3D distribution of the interpreted sections allowed us to make a horizontal correlation between the different sections and to elaborate the 3D geological model of the study area by using the deterministic inverse distance method. The estimated model indicates a volume of 621,130.625 m3 of the possible gold complex. The gold complex was then divided into two mineralization domains based on chargeability ranges (mV/V): A first domain is associated with a major mineralization zone (39–60 mV/V) with a volume of 10,842 m3, and a second domain is associated with secondary mineralization zone (18–39 mV/V) with a volume of 610,288 m3. This model allows to compartmentalize the gold complex and can be used as a base model for the gold investigation in the study area.
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Calibration of near‐surface multi‐frequency electromagnetic induction data
Authors Cécile Finco, Fayçal Rejiba, Cyril Schamper, Luis Henrique Cavalcante Fraga and Ao WangAbstractThe frequency‐domain electromagnetic induction method is a very efficient and convenient method to investigate a site of interest and for a large range of applications including hydrogeology and archaeology. Besides an easy infield acquisition, the data can be used to estimate the electrical, magnetic and, in certain cases, dielectric properties of the ground. It does, however, require calibration to get reliable quantitative values of these properties. We propose here an original and reliable self‐calibration method, specific to multi‐frequency measurements in the range of (5–100 kHz)‐based only on the consistency between the data at different acquisition frequencies. Contrary to other existing cross‐calibration procedures, no additional measurements with other methods are necessary. This self‐calibration (quadrature and in‐phase components of the electromagnetic induction signal) procedure is tested at a test site located at the centre for studies on risks, the environment, mobility and urban planning Normandie‐Centre facilities (Rouen, France). The developed quadrature self‐calibration has been successfully compared with the usual electrical resistivity tomography – electromagnetic induction cross‐calibration procedure. The main results reveal the potential of systematic assessment of all electromagnetic parameters from multi‐frequency and multi‐configuration electromagnetic induction data: The electrical resistivity and the magnetic susceptibility are estimated from the low‐frequency range, whereas the highest part of the frequency range is used for the dielectric permittivity.
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