Pub Date : 2022-11-23DOI: 10.1080/08123985.2022.2144722
Gagandeep Singh, Rahul Mahadik, W. K. Mohanty, A. Routray, Deepan Datta, S. Panda
This study improves a collection of attributes to detect subtle faults in three dimensional data obtained from the Krishna-Godavari (KG) basin, with results displayed on synthetic and real datasets. Seismic attributes, for instance, curvature and coherence, are often used to delineate discontinuities, such as faults and fractures where hydrocarbons may have been trapped. These attributes have their advantages subjective to the seismic data. In this paper, we propose a multi-attribute framework for identifying subtle faults inside seismic volumes. Curvature attribute is a powerful and popular technique to deal with these faults. The faulted horizon is fitted on the quadratic surface using the least-square method, and the most positive and most-negative curvature attributes are calculated, which are further used in saliency map calculations. Several signal processing techniques, such as Hough transform and ant tracking, have been used to delineate faults. Here, we have proposed a novel signal processing approach based on energy variations known as top-down saliency on the curvature attributes using 3D-FFT local spectra and multi-dimensional plane projections. To analyze the directional nature of seismic data, the directional center-surround technique is employed for visual attention. Furthermore, the log-Gabor filter and image erosion are applied to the saliency-rendered seismic volume to highlight the oriented amplitude discontinuities at faults. Most of the time, these discontinuities may not be very prominent to find the subtle faults and other trace-to-trace hidden geological features in three-dimensional seismic data. In our work, calculated attributes assist us in mapping these changes, because they are all differently sensitive to the faults and fractures in unique ways. Experimental results on real field seismic data from the Krishna-Godavari basin prove that the proposed algorithm is effective and efficient in tracking subtle and minor faults, better than previous works.
{"title":"Seismic multi-attribute approach using visual saliency for subtle fault visualization","authors":"Gagandeep Singh, Rahul Mahadik, W. K. Mohanty, A. Routray, Deepan Datta, S. Panda","doi":"10.1080/08123985.2022.2144722","DOIUrl":"https://doi.org/10.1080/08123985.2022.2144722","url":null,"abstract":"This study improves a collection of attributes to detect subtle faults in three dimensional data obtained from the Krishna-Godavari (KG) basin, with results displayed on synthetic and real datasets. Seismic attributes, for instance, curvature and coherence, are often used to delineate discontinuities, such as faults and fractures where hydrocarbons may have been trapped. These attributes have their advantages subjective to the seismic data. In this paper, we propose a multi-attribute framework for identifying subtle faults inside seismic volumes. Curvature attribute is a powerful and popular technique to deal with these faults. The faulted horizon is fitted on the quadratic surface using the least-square method, and the most positive and most-negative curvature attributes are calculated, which are further used in saliency map calculations. Several signal processing techniques, such as Hough transform and ant tracking, have been used to delineate faults. Here, we have proposed a novel signal processing approach based on energy variations known as top-down saliency on the curvature attributes using 3D-FFT local spectra and multi-dimensional plane projections. To analyze the directional nature of seismic data, the directional center-surround technique is employed for visual attention. Furthermore, the log-Gabor filter and image erosion are applied to the saliency-rendered seismic volume to highlight the oriented amplitude discontinuities at faults. Most of the time, these discontinuities may not be very prominent to find the subtle faults and other trace-to-trace hidden geological features in three-dimensional seismic data. In our work, calculated attributes assist us in mapping these changes, because they are all differently sensitive to the faults and fractures in unique ways. Experimental results on real field seismic data from the Krishna-Godavari basin prove that the proposed algorithm is effective and efficient in tracking subtle and minor faults, better than previous works.","PeriodicalId":50460,"journal":{"name":"Exploration Geophysics","volume":"54 1","pages":"387 - 394"},"PeriodicalIF":0.9,"publicationDate":"2022-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42238875","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-11-14DOI: 10.1080/08123985.2022.2144214
Xu Han, G. Tang, Shangxu Wang, Yanxiao He, Tao Liu, Yi Han
The pressure dependence of elastic parameters of rocks is mainly controlled by the geometry of the pore space. In general, the compliant-stiff pore structure model can be used to reasonably describe this pressure dependence. However, our experiment measurements revealed that for tight sandstone rock with complex pore structures, the contribution of the compressibility of the stiff pores to the elastic modulus is significant. The dual porosity is not sufficient to explain the variation of ultrasonic velocity with pressure. For this reason, we adopted a triple pore structure to divide the rock pore space into equant pores, intermediate pores and compliant pores. Our laboratory measurement and model results show that this pore space division can better describe the pressure dependence of the elastic moduli of rocks. The low-frequency stress–strain measurements show that the fluid-saturated tight sandstone has obvious dispersion in the seismic frequency band, which is primarily attributed to the squirt flow effect. In order to study the pressure and frequency dependence of the elastic moduli of tight sandstone, we retrieved the geometric parameters of the pore structure from the pressure variation of the ultrasonic velocities under dry conditions. Based on this complex pore structure and the extension of the squirt flow model, we constructed an elaborate rock physics model to explain the pressure and frequency dependence of velocity. The model does not require adjustable parameters, and all parameters are measured and calculated by the laboratory, which improves the accuracy of theoretical modelling. The modified squirt flow model can be used to describe dispersion and attenuation in a wide frequency band, and fit well with the velocity measurements in both the low-frequency range and the ultrasonic frequency range under different pressures. Therefore, this rock physics model could be applied in the extraction of pore microstructure and fluid properties provided elastic moduli or velocities can be estimated accurately.
{"title":"Effects of different pore shapes on the pressure and frequency dependence of velocities of oil-saturated tight sandstone","authors":"Xu Han, G. Tang, Shangxu Wang, Yanxiao He, Tao Liu, Yi Han","doi":"10.1080/08123985.2022.2144214","DOIUrl":"https://doi.org/10.1080/08123985.2022.2144214","url":null,"abstract":"The pressure dependence of elastic parameters of rocks is mainly controlled by the geometry of the pore space. In general, the compliant-stiff pore structure model can be used to reasonably describe this pressure dependence. However, our experiment measurements revealed that for tight sandstone rock with complex pore structures, the contribution of the compressibility of the stiff pores to the elastic modulus is significant. The dual porosity is not sufficient to explain the variation of ultrasonic velocity with pressure. For this reason, we adopted a triple pore structure to divide the rock pore space into equant pores, intermediate pores and compliant pores. Our laboratory measurement and model results show that this pore space division can better describe the pressure dependence of the elastic moduli of rocks. The low-frequency stress–strain measurements show that the fluid-saturated tight sandstone has obvious dispersion in the seismic frequency band, which is primarily attributed to the squirt flow effect. In order to study the pressure and frequency dependence of the elastic moduli of tight sandstone, we retrieved the geometric parameters of the pore structure from the pressure variation of the ultrasonic velocities under dry conditions. Based on this complex pore structure and the extension of the squirt flow model, we constructed an elaborate rock physics model to explain the pressure and frequency dependence of velocity. The model does not require adjustable parameters, and all parameters are measured and calculated by the laboratory, which improves the accuracy of theoretical modelling. The modified squirt flow model can be used to describe dispersion and attenuation in a wide frequency band, and fit well with the velocity measurements in both the low-frequency range and the ultrasonic frequency range under different pressures. Therefore, this rock physics model could be applied in the extraction of pore microstructure and fluid properties provided elastic moduli or velocities can be estimated accurately.","PeriodicalId":50460,"journal":{"name":"Exploration Geophysics","volume":"54 1","pages":"376 - 386"},"PeriodicalIF":0.9,"publicationDate":"2022-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48647055","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-11-08DOI: 10.1080/08123985.2022.2135430
Mohammad Amin Aminian, M. Riahi
ABSTRACT The main purpose of this research is to evaluate the effectiveness of coherent noise clustering in reconstructing leaked signals after conventional noise attenuation filters. We use Generalised Auto Regressive Conditional Heteroskedasticity (GARCH) model. We apply clustering, conditional variance, and conditional standard deviation analysis to synthetic and experimental seismic field data. The conditional variance and conditional standard deviation of coherent noises that are attenuated by the Ormsby and f-k filter are calculated. Each cluster is labelled using the two-dimensional average clustering method and then leaked signals are reconstructed from the initially filtered data to improve the signal-to-noise ratio. Results show that the proposed method mostly reconstructs the leaked signals after conventional filters.
{"title":"Enhanced data fidelity after ground roll attenuation using conditional standard deviation clustering obtained from the GARCH model","authors":"Mohammad Amin Aminian, M. Riahi","doi":"10.1080/08123985.2022.2135430","DOIUrl":"https://doi.org/10.1080/08123985.2022.2135430","url":null,"abstract":"ABSTRACT The main purpose of this research is to evaluate the effectiveness of coherent noise clustering in reconstructing leaked signals after conventional noise attenuation filters. We use Generalised Auto Regressive Conditional Heteroskedasticity (GARCH) model. We apply clustering, conditional variance, and conditional standard deviation analysis to synthetic and experimental seismic field data. The conditional variance and conditional standard deviation of coherent noises that are attenuated by the Ormsby and f-k filter are calculated. Each cluster is labelled using the two-dimensional average clustering method and then leaked signals are reconstructed from the initially filtered data to improve the signal-to-noise ratio. Results show that the proposed method mostly reconstructs the leaked signals after conventional filters.","PeriodicalId":50460,"journal":{"name":"Exploration Geophysics","volume":"54 1","pages":"271 - 287"},"PeriodicalIF":0.9,"publicationDate":"2022-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46527736","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-11-07DOI: 10.1080/08123985.2022.2140654
Mohammad Iranimehr, M. Riahi, A. Goudarzi
This paper introduces the estimated pattern denoising (EPD) wavelet transform for random noise attenuation in geophysical data. The proposed approach combines the capability of the Gaussian filter and dual-tree rational dilation wavelet transform (DT-RADWT) in random noise detection and suppression; we called this method Estimated Pattern Denoising (EPD). The EPD is an innovative approach in terms of estimation of the location and amplitude of the noise pattern, directly from the data. The employed approach produces a higher quality factor (Q-factor) than the conventional dyadic discrete wavelet transform (DWT) and separates the noise from the signal with higher accuracy. The EPD provides a data-driven scheme that resolves the complexity of the random noise model in noise suppression, using an auxiliary Gaussian filter. This approach does not require prior information about the noise source, statistical distribution, or frequency range. We show successful suppression of random noise using the proposed approach on synthetic and real field data.
{"title":"Random noise attenuation using the novel Estimated Noise Pattern Denoising Algorithm","authors":"Mohammad Iranimehr, M. Riahi, A. Goudarzi","doi":"10.1080/08123985.2022.2140654","DOIUrl":"https://doi.org/10.1080/08123985.2022.2140654","url":null,"abstract":"This paper introduces the estimated pattern denoising (EPD) wavelet transform for random noise attenuation in geophysical data. The proposed approach combines the capability of the Gaussian filter and dual-tree rational dilation wavelet transform (DT-RADWT) in random noise detection and suppression; we called this method Estimated Pattern Denoising (EPD). The EPD is an innovative approach in terms of estimation of the location and amplitude of the noise pattern, directly from the data. The employed approach produces a higher quality factor (Q-factor) than the conventional dyadic discrete wavelet transform (DWT) and separates the noise from the signal with higher accuracy. The EPD provides a data-driven scheme that resolves the complexity of the random noise model in noise suppression, using an auxiliary Gaussian filter. This approach does not require prior information about the noise source, statistical distribution, or frequency range. We show successful suppression of random noise using the proposed approach on synthetic and real field data.","PeriodicalId":50460,"journal":{"name":"Exploration Geophysics","volume":"54 1","pages":"316 - 328"},"PeriodicalIF":0.9,"publicationDate":"2022-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45227045","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-11-07DOI: 10.1080/08123985.2022.2140653
Omar N. A. Al-Khazraji
The time-depth conversion process is a significant task in seismic interpretation to establish the link between geophysical information in the time domain and geological information in the depth domain at/away from well locations. Selecting the suitable velocity model for time-depth conversion to generate an accurate depth map is difficult if the accuracy of these models is unknown. In the current study, the cross-validation technique is used as a tool to diagnose and evaluate the performance of time-depth conversion at/away from well controls to predict the depth of Top Hartha and Zubair reservoirs using the dataset of East Baghdad Oil Field. To test this technique, four common velocity model approaches used for time-depth conversion with different scenarios of velocity parameters (initial velocity V 0 and depth gradient (K)) were applied to produce ten velocity models (1–10). According to the gradient variation of velocity with depth, check shot analysis, the velocity models (1–10) include three key velocities layer-cakes: Layer 1 (Middle Miocene-Upper Cretaceous), Layer 2 (Upper Cretaceous), and Layer 3 (Lower Cretaceous) with 18 horizons from Middle Miocene down to Lower Cretaceous. The cross-validation analysis reveals that the velocity model with a variable surface initial velocity and constant depth gradient (Model 9) was the most accurate with fewer mistie between actual and predicted depth. Consequently, this model is used to construct the depth map of the Hartha and Zubair reservoirs. Finally, this study progresses a workflow that can be applied to the region with any geological setting to investigate time-depth conversion uncertainty.
{"title":"Cross-validation of time-depth conversion and evaluation of different approaches in the Mesopotamian Basin, Iraq","authors":"Omar N. A. Al-Khazraji","doi":"10.1080/08123985.2022.2140653","DOIUrl":"https://doi.org/10.1080/08123985.2022.2140653","url":null,"abstract":"The time-depth conversion process is a significant task in seismic interpretation to establish the link between geophysical information in the time domain and geological information in the depth domain at/away from well locations. Selecting the suitable velocity model for time-depth conversion to generate an accurate depth map is difficult if the accuracy of these models is unknown. In the current study, the cross-validation technique is used as a tool to diagnose and evaluate the performance of time-depth conversion at/away from well controls to predict the depth of Top Hartha and Zubair reservoirs using the dataset of East Baghdad Oil Field. To test this technique, four common velocity model approaches used for time-depth conversion with different scenarios of velocity parameters (initial velocity V 0 and depth gradient (K)) were applied to produce ten velocity models (1–10). According to the gradient variation of velocity with depth, check shot analysis, the velocity models (1–10) include three key velocities layer-cakes: Layer 1 (Middle Miocene-Upper Cretaceous), Layer 2 (Upper Cretaceous), and Layer 3 (Lower Cretaceous) with 18 horizons from Middle Miocene down to Lower Cretaceous. The cross-validation analysis reveals that the velocity model with a variable surface initial velocity and constant depth gradient (Model 9) was the most accurate with fewer mistie between actual and predicted depth. Consequently, this model is used to construct the depth map of the Hartha and Zubair reservoirs. Finally, this study progresses a workflow that can be applied to the region with any geological setting to investigate time-depth conversion uncertainty.","PeriodicalId":50460,"journal":{"name":"Exploration Geophysics","volume":"54 1","pages":"288 - 315"},"PeriodicalIF":0.9,"publicationDate":"2022-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47966210","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-11-04DOI: 10.1080/08123985.2022.2131390
Ibrar Iqbal, Bin Xiong, G. Tian, Yu Lu, Yang Yang
Adequate knowledge of velocity is required for accurate data imaging and depth conversion, as well as for quantifying the distribution of soil water content. Without complementary borehole information in the form of dielectric permittivity and/or porosity logs along the profile, it is currently impossible to reliably estimate the high-frequency electromagnetic velocity distribution in the probed subsurface region. Here, we present a new method for calculating the precise subsurface velocity structure from ground penetrating radar (GPR) reflection data that does not require boreholes or log data. This study investigates the ability of the pulse_EKKO PRO GPR system to predict a vertical profile for the possible velocity estimation of a layered and contaminated geophysical test site in Hangzhou, China. All data were acquired and saved on the GPR system in various files (projects) before analysis using GPR software to obtain approximated velocity modelling using common midpoint (CMP) gathers. Using the velocity spectrum analysis, a vertical profile of the interval velocities can be derived from each CMP gather. The findings of this study indicate that the proposed method is effective and sustainable. Furthermore, owing to the efficacy of the method in terms of field effort and computational complexity, it can easily be expanded to 3D GPR velocity exploration, increasing its importance in comparison to standard offset-based techniques for estimating velocity using GPR.
{"title":"Analysis of subsurface velocity using CMP gathers picked up by unshielded GPR system: results from an experimental NAPL contaminated test site","authors":"Ibrar Iqbal, Bin Xiong, G. Tian, Yu Lu, Yang Yang","doi":"10.1080/08123985.2022.2131390","DOIUrl":"https://doi.org/10.1080/08123985.2022.2131390","url":null,"abstract":"Adequate knowledge of velocity is required for accurate data imaging and depth conversion, as well as for quantifying the distribution of soil water content. Without complementary borehole information in the form of dielectric permittivity and/or porosity logs along the profile, it is currently impossible to reliably estimate the high-frequency electromagnetic velocity distribution in the probed subsurface region. Here, we present a new method for calculating the precise subsurface velocity structure from ground penetrating radar (GPR) reflection data that does not require boreholes or log data. This study investigates the ability of the pulse_EKKO PRO GPR system to predict a vertical profile for the possible velocity estimation of a layered and contaminated geophysical test site in Hangzhou, China. All data were acquired and saved on the GPR system in various files (projects) before analysis using GPR software to obtain approximated velocity modelling using common midpoint (CMP) gathers. Using the velocity spectrum analysis, a vertical profile of the interval velocities can be derived from each CMP gather. The findings of this study indicate that the proposed method is effective and sustainable. Furthermore, owing to the efficacy of the method in terms of field effort and computational complexity, it can easily be expanded to 3D GPR velocity exploration, increasing its importance in comparison to standard offset-based techniques for estimating velocity using GPR.","PeriodicalId":50460,"journal":{"name":"Exploration Geophysics","volume":"54 1","pages":"261 - 270"},"PeriodicalIF":0.9,"publicationDate":"2022-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48064348","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-11-02DOI: 10.1080/08123985.2022.2034477
Jing Wang, Yang Liu, Hongyu Zhou
Compared with the standard staggered-grid finite-difference (FD) methods, equivalent staggered-grid (ESG) ones can significantly reduce the computational memory for acoustic wave modelling in the variable-density media. To further enhance the simulation efficiency and accuracy, one way is to optimize the FD coefficients, another way is to design new FD stencils. In this paper, we propose a modified ESG (M-ESG) scheme which can significantly accelerate the wavefield simulation process while preserving or even improving the modelling accuracy. We calculate the FD coefficients by approximating the temporal and spatial derivatives simultaneously based on time–space domain (TS-D) dispersion relation of the discrete wave equation. Our M-ESG scheme in the TS-D can maintain basically the same accuracy as the conventional ESG (C-ESG) one when the FD coefficients are derived by the Taylor-series expansion (TE) approach. Note that the TS-D dispersion relation is nonlinear with respect to the FD coefficients of the C-ESG scheme, so it is difficult to obtain the optimized FD coefficients for the discrete wave equation. However, we can minimize the L2-norm error of the dispersion relation based on our M-ESG scheme to implement a linear FD coefficients optimization strategy, which is easy and efficient. Comparisons with TE- and optimization-based C-ESG schemes demonstrate the accuracy, stability, and efficiency superiorities of our TE- and optimization-based M-ESG ones.
{"title":"A novel equivalent staggered-grid finite-difference scheme and its optimization strategy for variable-density acoustic wave modelling","authors":"Jing Wang, Yang Liu, Hongyu Zhou","doi":"10.1080/08123985.2022.2034477","DOIUrl":"https://doi.org/10.1080/08123985.2022.2034477","url":null,"abstract":"Compared with the standard staggered-grid finite-difference (FD) methods, equivalent staggered-grid (ESG) ones can significantly reduce the computational memory for acoustic wave modelling in the variable-density media. To further enhance the simulation efficiency and accuracy, one way is to optimize the FD coefficients, another way is to design new FD stencils. In this paper, we propose a modified ESG (M-ESG) scheme which can significantly accelerate the wavefield simulation process while preserving or even improving the modelling accuracy. We calculate the FD coefficients by approximating the temporal and spatial derivatives simultaneously based on time–space domain (TS-D) dispersion relation of the discrete wave equation. Our M-ESG scheme in the TS-D can maintain basically the same accuracy as the conventional ESG (C-ESG) one when the FD coefficients are derived by the Taylor-series expansion (TE) approach. Note that the TS-D dispersion relation is nonlinear with respect to the FD coefficients of the C-ESG scheme, so it is difficult to obtain the optimized FD coefficients for the discrete wave equation. However, we can minimize the L2-norm error of the dispersion relation based on our M-ESG scheme to implement a linear FD coefficients optimization strategy, which is easy and efficient. Comparisons with TE- and optimization-based C-ESG schemes demonstrate the accuracy, stability, and efficiency superiorities of our TE- and optimization-based M-ESG ones.","PeriodicalId":50460,"journal":{"name":"Exploration Geophysics","volume":"53 1","pages":"669 - 682"},"PeriodicalIF":0.9,"publicationDate":"2022-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47640463","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-09-21DOI: 10.1080/08123985.2022.2123736
Belal Mohamed Abdelhamed, Sultan Awad Sultan Araffa, T. Abdelhafeez
The current study aims to determine the basement configuration and basement-related structural elements of the Abu Gharadig basin.: We delineated subsurface features that affect the configuration of reservoirs in the study area using an integrated interpretation of potential field and seismic reflection data. The study area lies in the North-Western Desert of Egypt to the east of the Qattara Depression, between latitudes 29° 00’ and 30° 00’ N and longitudes 28° 00’ and 30° 00’ E. Gravity data interpretation delineates shallow features, with NNE-SSW as the major trend and NW-SE as the minor trend. Given that the Euler structural index is approximately zero, these trends probably represent major faults with steep dips and large throws, which juxtapose considerable thicknesses of rocks with contrasting magnetization. On the other hand, the most common tectonic trends prevailing in the deeper levels are the NEN-SWS and NW-SE as the major trends and ENE-WSW as a minor trend. At the same time, the dominant tectonic trend from the Euler solution is NNW-SSE as a major trend and NNE -SSW and WNW-ESE as minor trends. The interpretation of magnetic data indicates the study area dissect by different trends where the trends of shallow features are NNW-SSE as a major trend and E-W as a minor trend. On the other hand, the most common tectonic trends prevailing in the deeper levels are the NNE-SSW and WNW-ESE as major trends and E-W, ENE-WSW, NEN-SWS, and NWN-SES as minor trends. At the same time, the dominant tectonic trend from the Euler solution is N-S as a major trend and NW-SE and NE-SW as minor trends. In the study area, the depth to the top of the basement rocks ranges from 1731.7 m to more than 4736.6 m. Main faults only affect the Lower and Upper Cretaceous sequences, according to seismic interpretation, and appear to be in two trends, the NW-SE and NWN-SES. These structural trends affect the configuration of oil reservoirs in the study area. The study area contains valuable reservoirs according to boreholes drilled in the stud area.
{"title":"Geophysical studies around abu gharadig basin, North Western desert, Egypt","authors":"Belal Mohamed Abdelhamed, Sultan Awad Sultan Araffa, T. Abdelhafeez","doi":"10.1080/08123985.2022.2123736","DOIUrl":"https://doi.org/10.1080/08123985.2022.2123736","url":null,"abstract":"The current study aims to determine the basement configuration and basement-related structural elements of the Abu Gharadig basin.: We delineated subsurface features that affect the configuration of reservoirs in the study area using an integrated interpretation of potential field and seismic reflection data. The study area lies in the North-Western Desert of Egypt to the east of the Qattara Depression, between latitudes 29° 00’ and 30° 00’ N and longitudes 28° 00’ and 30° 00’ E. Gravity data interpretation delineates shallow features, with NNE-SSW as the major trend and NW-SE as the minor trend. Given that the Euler structural index is approximately zero, these trends probably represent major faults with steep dips and large throws, which juxtapose considerable thicknesses of rocks with contrasting magnetization. On the other hand, the most common tectonic trends prevailing in the deeper levels are the NEN-SWS and NW-SE as the major trends and ENE-WSW as a minor trend. At the same time, the dominant tectonic trend from the Euler solution is NNW-SSE as a major trend and NNE -SSW and WNW-ESE as minor trends. The interpretation of magnetic data indicates the study area dissect by different trends where the trends of shallow features are NNW-SSE as a major trend and E-W as a minor trend. On the other hand, the most common tectonic trends prevailing in the deeper levels are the NNE-SSW and WNW-ESE as major trends and E-W, ENE-WSW, NEN-SWS, and NWN-SES as minor trends. At the same time, the dominant tectonic trend from the Euler solution is N-S as a major trend and NW-SE and NE-SW as minor trends. In the study area, the depth to the top of the basement rocks ranges from 1731.7 m to more than 4736.6 m. Main faults only affect the Lower and Upper Cretaceous sequences, according to seismic interpretation, and appear to be in two trends, the NW-SE and NWN-SES. These structural trends affect the configuration of oil reservoirs in the study area. The study area contains valuable reservoirs according to boreholes drilled in the stud area.","PeriodicalId":50460,"journal":{"name":"Exploration Geophysics","volume":"54 1","pages":"329 - 351"},"PeriodicalIF":0.9,"publicationDate":"2022-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49285152","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-09-08DOI: 10.1080/08123985.2022.2091986
J. Son, Seok-Jun Yang, S. Shin, Samgyu Park
Electrochemical reactions at the interface between groundwater and sulphides are remarkable. Sulphides in mineralised zones are relatively abundant compared to hydrothermal alteration zones and host rocks. Complex resistivity is a geophysical tool for visualising difference between various subsurface electrochemical reactions. The epithermal Au–Ag mineralisation at Moisan hill (South Korea) occurs in the extensively disseminated pyrite zone, a typical feature of advanced argillic and argillic alteration zones. The epithermal vein at Moisan had a strike length of >500 m horizontally and approximately 300 m vertically and was controlled by the WNW fault zone. In this context, the deposit was subjected to a test bed to demonstrate the applicability of the complex resistivity survey for mineral exploration. To compare complex resistivity results with geological characteristics of epithermal mineralisation, we visualised the complex resistivity survey results and Au–Ag mineralised zones confirmed by drilling cores in three dimensions. The quartz veins of the targets showed high resistivity and a strong phase response; however, both the alteration zones and host rocks showed lower resistivity and a weaker phase response than the target zones. Through a step-by-step clustering analysis, a simple map integrating both kinds of the geophysical models was generated, to identify the boundary between the target and background. Geologic survey and drilling investigations indicate that the target is well-localised in a mineralised zone. The complex resistivity survey is a useful tool for exploring epithermal Au–Ag deposits.
{"title":"Application of complex resistivity survey in an epithermal Au-Ag deposit, South Korea","authors":"J. Son, Seok-Jun Yang, S. Shin, Samgyu Park","doi":"10.1080/08123985.2022.2091986","DOIUrl":"https://doi.org/10.1080/08123985.2022.2091986","url":null,"abstract":"Electrochemical reactions at the interface between groundwater and sulphides are remarkable. Sulphides in mineralised zones are relatively abundant compared to hydrothermal alteration zones and host rocks. Complex resistivity is a geophysical tool for visualising difference between various subsurface electrochemical reactions. The epithermal Au–Ag mineralisation at Moisan hill (South Korea) occurs in the extensively disseminated pyrite zone, a typical feature of advanced argillic and argillic alteration zones. The epithermal vein at Moisan had a strike length of >500 m horizontally and approximately 300 m vertically and was controlled by the WNW fault zone. In this context, the deposit was subjected to a test bed to demonstrate the applicability of the complex resistivity survey for mineral exploration. To compare complex resistivity results with geological characteristics of epithermal mineralisation, we visualised the complex resistivity survey results and Au–Ag mineralised zones confirmed by drilling cores in three dimensions. The quartz veins of the targets showed high resistivity and a strong phase response; however, both the alteration zones and host rocks showed lower resistivity and a weaker phase response than the target zones. Through a step-by-step clustering analysis, a simple map integrating both kinds of the geophysical models was generated, to identify the boundary between the target and background. Geologic survey and drilling investigations indicate that the target is well-localised in a mineralised zone. The complex resistivity survey is a useful tool for exploring epithermal Au–Ag deposits.","PeriodicalId":50460,"journal":{"name":"Exploration Geophysics","volume":"54 1","pages":"217 - 228"},"PeriodicalIF":0.9,"publicationDate":"2022-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42774109","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-09-02DOI: 10.1080/08123985.2022.2117602
Fan Wu, Jingye Li, Xiaohong Chen, W. Geng, Wei Tang
Accurate prediction of S-wave velocity is of great significance in many aspects, such as inversion, migration, brittleness index calculation, etc. Under normal circumstances, the more types of known input parameters there are, the more accurate the rock’s specific situation, and the more accurate the predicted S-wave velocity. However, considering the actual situation, the types of parameters obtained through logging curves are relatively limited. Some parameters cannot be measured and calculated, which limits the accuracy of S-wave prediction. Therefore, if the parameters can be predicted, a more accurate underground situation is able to described by these parameters. Through rockphysical analysis, the pore aspect ratio and capillary pressure coefficient can affect the velocity. In this way, a new orthorhombic (ORT) rockphysical modeling process considering the pore aspect ratio and capillary pressure coefficient is proposed. The model consists of VTI anisotropy from compaction or textural alignment of minerals, and HTI anisotropy from high-angle fractures caused by stratum pressure, thus showing ORT anisotropy. The inputs of the model can be multiple minerals. And the pore structure and the modulus of the mixed fluids in the pores are considered. We use inverse theory (quantum genetic algorithms) to obtain the pore aspect ratio and capillary pressure coefficient and finally calculate the S-wave velocity through the above parameters. The calculation results in a shale reservoir show that the predicted S-wave velocity is in good agreement with the real logging data. This shows that the proposed rockphysical modeling process and inverse algorithm method are effective.
{"title":"Estimation of pore aspect ratio and capillary pressure coefficient to predict S-wave velocity based on rockphysics modeling in orthorhombic anisotropic reservoirs","authors":"Fan Wu, Jingye Li, Xiaohong Chen, W. Geng, Wei Tang","doi":"10.1080/08123985.2022.2117602","DOIUrl":"https://doi.org/10.1080/08123985.2022.2117602","url":null,"abstract":"Accurate prediction of S-wave velocity is of great significance in many aspects, such as inversion, migration, brittleness index calculation, etc. Under normal circumstances, the more types of known input parameters there are, the more accurate the rock’s specific situation, and the more accurate the predicted S-wave velocity. However, considering the actual situation, the types of parameters obtained through logging curves are relatively limited. Some parameters cannot be measured and calculated, which limits the accuracy of S-wave prediction. Therefore, if the parameters can be predicted, a more accurate underground situation is able to described by these parameters. Through rockphysical analysis, the pore aspect ratio and capillary pressure coefficient can affect the velocity. In this way, a new orthorhombic (ORT) rockphysical modeling process considering the pore aspect ratio and capillary pressure coefficient is proposed. The model consists of VTI anisotropy from compaction or textural alignment of minerals, and HTI anisotropy from high-angle fractures caused by stratum pressure, thus showing ORT anisotropy. The inputs of the model can be multiple minerals. And the pore structure and the modulus of the mixed fluids in the pores are considered. We use inverse theory (quantum genetic algorithms) to obtain the pore aspect ratio and capillary pressure coefficient and finally calculate the S-wave velocity through the above parameters. The calculation results in a shale reservoir show that the predicted S-wave velocity is in good agreement with the real logging data. This shows that the proposed rockphysical modeling process and inverse algorithm method are effective.","PeriodicalId":50460,"journal":{"name":"Exploration Geophysics","volume":"54 1","pages":"229 - 240"},"PeriodicalIF":0.9,"publicationDate":"2022-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48311851","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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