STRYDE’s Post

Join EEGS for the May TAG webinar “Passive Seismic Approaches for Active Geophysicists” Tuesday, May 28, 2024 Register at: https://lnkd.in/ez5JvE4D Resonance frequencies are intrinsic properties of elastic media: they depend on their stiffness and mass distribution, and on their constraints.  In geological and geophysical applications, resonance frequencies are traditionally assessed by means of the microtremor H/V seismic method.  Resonance frequencies can quite easily be converted into the corresponding depths of seismic reflectors responsible for the occurrence of those resonances, in the presence of a Vs estimate. Since 1999, this has led to several interesting images of the main reflectors in the soil achieved by means of passive single station approaches.  However, resonances, being intrinsic properties, are expected to change only in amplitude and not in frequency with the measurement point, in a same medium. "How can we reconcile the fact that, as an example, a basin cross-section is a geological medium with characteristic and unique modal frequencies that do not change along the cross-section, with the fact that the H/V peak frequencies shift from the sides to the center of the basin? To answer this question, we’ll explore what we call 1D and 2D resonance and H/V or H&V approaches and provide some hints on how to discriminate and exploit the two cases.

Join EEGS for the May TAG webinar “Passive Seismic Approaches for Active Geophysicists”  Tuesday, May 28, 2024  Register at: https://lnkd.in/ez5JvE4D Resonance frequencies are intrinsic properties of elastic media: they depend on their stiffness and mass distribution, and on their constraints.  In geological and geophysical applications, resonance frequencies are traditionally assessed by means of the microtremor H/V seismic method.  Resonance frequencies can quite easily be converted into the corresponding depths of seismic reflectors responsible for the occurrence of those resonances, in the presence of a Vs estimate. Since 1999, this has led to several interesting images of the main reflectors in the soil achieved by means of passive single station approaches.  However, resonances, being intrinsic properties, are expected to change only in amplitude and not in frequency with the measurement point, in a same medium. "How can we reconcile the fact that, as an example, a basin cross-section is a geological medium with characteristic and unique modal frequencies that do not change along the cross-section, with the fact that the H/V peak frequencies shift from the sides to the center of the basin? To answer this question, we’ll explore what we call 1D and 2D resonance and H/V or H&V approaches and provide some hints on how to discriminate and exploit the two cases. 

Regional petrophysics: Younami and Southwest Terranes 2022-23 https://lnkd.in/g5m3t6hC This dataset includes petrophysical analyses on 415 samples from 5 diamond holes located between Mount Magnet, Ravensthorpe and Greenbushes in WA. The drillholes penetrate the Archean igneous, meta-igneous and meta-sedimentary units of the granite-greenstone belts that comprise the Southwest and Younami Terranes. Released as part of an EIS-funded petrophysics project to sample diamond drillcore from across Western Australia. Petrophysical datasets can assist with the planning and interpreting of geophysical data, including characterizing the physical property response of stratigraphic units, alteration and mineralization styles, and constraining geophysical models of the subsurface. #EISfunded #ExplorationIncentiveScheme #Petrophysics #Archean

This week, as we celebrate Geophysics Day from Argentina, we extend our congratulations to all professionals in this exciting and valuable field of science. We also take this opportunity to invite you to join us for the April session of our 2024 webinar series titled "Shaping Your Seismic": Exploring Exclusion Zones in PaleoScan with Jake Marson. 🔗 Register >> https://lnkd.in/exTQ6WnP #subsurface #geoscience #geophysics

Filtering out noise to improve interpretation!💡 Sharp Reflections will attend the SEG 4D Forum in Galveston, Texas, 4-6 November with a speaker and a stand. Peter Harris, our Chief geophysicist, will present the paper "The Anatomy of Time-Lapse Seismic Cross-Plots for Separating Pressure and Saturation Effects" in the morning session on Tuesday November 5th. The paper compares time-lapse seismic analysis using a coloured inversion and extended elastic impedance analysis to separate pressure and saturation changes with a relative inversion method for the same aim. Noise in the AVO gradient tends to cause a noise trend in the EEI cross-plot that is nearly parallel to the direction associated with pressure changes. This causes a significant loss of resolution when using EEI. By contrast, the relative inversion results are less sensitive to noise and are more readily interpreted in terms of pressure changes. A North Sea dataset with seven vintages of data is analysed and the production-related pressure changes are mapped. Check out the event programme: https://lnkd.in/gZXTCSfK #SeismicInterpretation #OilandGas #SharpReflections #timelapse #4D

When designing an orthogonal 3D seismic program, we must consider the orientation of the source lines and receiver lines. There are 2 main criteria to consider in making the decision on how to orient the lines; the COST CRITERIA and the GEOPHYSICAL CRITERIA. So what happens when the results of our 2 criteria are different? How do we proceed: We must evaluate the BUSINESS VALUE OF USING THE OPTIMAL GEOPHYSICAL LINE ORIENTATION vs THE COST INCREASE of not following the line orientation with optimal cost. To answer this: We need to determine if the data quality will be reduced enough to justify the additional costs associated with the geophysically optimum line orientation. If we can reduce our exploration risk factors significantly by spending additional capital on the optimal geophysical line orientation, we move forward with more costly optimal geophysical line orientation.

🌐 EAGE E-Lecture: Seismic Geomechanics by Jörg Herwanger: 🔍 In this compact version of his EAGE Education Tour (EET 5), Jörg Herwanger (Ikon Science, previously Schlumberger) discusses the process of building and calibrating geomechanical models using 3D and 4D seismic data. 📊 He analyzes the three main uses that seismic data provide in building geomechanical models: horizon and fault interpretation for building structural models, AVO inversion and rock physics models for creating mechanical property models, and for model calibration. 🌏 Herwanger elaborates on these three points in two case studies. A 3D exploration geomechanical model. A 4D geomechanical model used for field development planning. https://lnkd.in/dcFwmeYE

When designing an orthogonal 3D seismic program, we must consider the orientation of the source lines and receiver lines. There are 2 main criteria to consider in making the decision on how to orient the lines; the COST CRITERIA and the GEOPHYSICAL CRITERIA. So what happens when the results of our 2 criteria are different? How do we proceed: We must evaluate the BUSINESS VALUE OF USING THE OPTIMAL GEOPHYSICAL LINE ORIENTATION vs THE COST INCREASE of not following the line orientation with optimal cost. To answer this: We need to determine if the data quality will be reduced enough to justify the additional costs associated with the geophysically optimum line orientation. If we can reduce our exploration risk factors significantly by spending additional capital on the optimal geophysical line orientation, we move forward with more costly optimal geophysical line orientation.

🚀🚀 Pre-print alert 🚀🚀 🙃 We call it Upside down Rayleigh-Marchenko: a new entry in the family of Marchenko-based methods in geophysics, perfectly suited for modern #seabed seismic acquisition systems with sparse receiver geometries. 💡 Together with my PhD student Ning Wang, we show that by smarty leveraging reciprocity, as commonly done in imaging of seabed data, the Marchenko equations are now also applicable to sparse acquisition geometries without making any compromise in terms of quality or requiring expensive outer-inner inversion schemes as previously proposed in the literature. Link to arxiv: https://lnkd.in/eSHZppaQ #kaust #pse #research #marchenko #inverseproblems

Although I am not at ASEG Discover in Hobart myself, I am excited for the presentation today on “A Novel yet Simple Approach to the Interpretation of HVSR Data in Australia – A Data Rich Case Study from the Pilbara” that I co-authored with Nathan Tabain from BHP. In this work, which is based on a dataset of ~3,400 short-duration 3C passive seismic recordings, Nathan will discuss how not peaks, but resonance troughs were used for interpretation. Indeed, the trough horizon was easier to interpret, had better along-line and across-line continuity, and more vertical variability than the corresponding peak horizon at half the trough frequency. Nathan will bring the proverbial kitchen sink and show how these data correlated, rather spectacularly, with several independent apriori datasets (airborne geophysics and drilling) and interpretations. Extended abstract: https://lnkd.in/d6uFkS8D. Presentation: Thu. 17/10 at 12 noon. Thanks to Alejandro Sanchez and others in the Southern Geoscience Consultants Near Surface team for their processing support, and Aaron Mullineux and crew for the efficient and safe aquisition of the data. The resonance trough example below is from Chandler and Lively (2014): Evaluation of the horizontal-to-vertical spectral ratio (HVSR) passive seismic method for estimating the thickness of quaternary deposits in Minnesota and adjacent parts of Wisconsin. Minnesota Geological Survey, OFR14-01.