3D Alford rotation analysis for the Diamond M Field, Midland Basin, Texas

2014 ◽  
Vol 2 (2) ◽  
pp. SE63-SE75 ◽  
Author(s):  
Oswaldo E. Davogustto Cataldo ◽  
Timothy J. Kwiatkowski ◽  
Kurt J. Marfurt ◽  
Steven L. Roche ◽  
James W. Thomas
Keyword(s):  
Vertical Component ◽  
Horizontal Stress ◽  
Compressional Wave ◽  
Carbonate Reservoir ◽  
S Wave ◽  
Stress Regime ◽  
Compressional Waves ◽  
Principal Axes ◽  
Wave Splitting ◽  
Processing Effort

The 2C by 2C S-wave survey generated significant excitement in the mid-1980s, but then it fell out of favor when S-wave splitting initially attributed to fractures was also found to be associated with an anisotropic stress regime. In general, 2C by 2C data require more expensive acquisition and more processing effort to obtain images comparable to 1C “compressional wave” data acquired with vertical component sources and receivers. Because S-waves are insensitive to fluids, and hence the water table, the effective S-wave weathering zone is greater than that for compressional waves, making statics more difficult. S-wave splitting due to anisotropy complicates residual statics and velocity analysis as well as the final image. S-wave frequencies and S-wave moveout are closer to those of contaminating ground roll than compressional waves. Since Alford’s introduction of S-wave rotation from survey coordinates to the principal axes in 1986, geoscientist and engineers retain their interest in fractures but are also keenly interested in the direction and magnitude of maximum horizontal stress. Simultaneous sweep and improved recording technology have reduced the acquisition cost to approximate that of 1C data. Alford’s work was applied to 2C by 2C poststack data. We extended the Alford rotation to prestack data using a modern high-fold 2C by 2C survey acquired over a fractured carbonate reservoir in the Diamond M Field, Texas. Through careful processing, the resulting images were comparable and in many places superior to that of the contemporaneously acquired 1C data. More importantly, we found a good correlation between our derived fracture azimuth map and the fracture azimuth log data from wells present in the field.

Comparison of P‐ and S‐wave seismic data: A new method for detecting gas reservoirs

Geophysics ◽  
1984 ◽  
Vol 49 (9) ◽  
pp. 1420-1431 ◽  
Author(s):  
Ross Alan Ensley
Keyword(s):  
Shear Wave ◽  
Seismic Data ◽  
Quantitative Methods ◽  
Qualitative Evaluation ◽  
Compressional Wave ◽  
Bright Spot ◽  
S Wave ◽  
Gas Reservoirs ◽  
Compressional Waves

Compressional waves are sensitive to the type of pore fluid within rocks, but shear waves are only slightly affected by changes in fluid type. This suggests that a comparison of compressional‐ and shear‐wave seismic data recorded over a prospect may allow an interpreter to discriminate between gas‐related anomalies and those related to lithology. This case study documents that where a compressional‐wave “bright spot” or other direct hydrocarbon indicator is present, such a comparison can be used to verify the presence of gas. In practice, the technique can only be used for a qualitative evaluation. However, future improvement of shear‐wave data quality may enable the use of more quantitative methods as well.

Premonitory seismic-wave phenomena before earthquakes near Fairview Peak, Nevada

1975 ◽  
Vol 65 (2) ◽  
pp. 425-437 ◽  
Author(s):  
Indra N. Gupta
Keyword(s):  
Vertical Component ◽  
Temporal Variations ◽  
Stress Axis ◽  
Wave Form ◽  
S Wave ◽  
Upward Migration ◽  
Compression Direction ◽  
Wave Splitting ◽  
First Motion ◽  
Precursory Phenomena

abstract Anomalous variations in three different seismic processes have been observed before an earthquake of magnitude 4 on May 14, 1971 in the Fairview Peak region of central Nevada. The data used are the three-component seismograms from Tonopah (TNP) and Battle Mountain (BMN) as well as the vertical-component seismograms from several other seismographic stations. The observed precursory phenomena are (1) reorientation of the compressive stress axis: evidence for this is based on clear reversals of first motion of Pg at certain stations together with reversal of wave form of the SV component of Sg at BMN; (2) vertical migration of hypocenters: the PmP phase is often distinctly observed in central Nevada and the observed temporal variations in t(PmP)−t(Pg) at TNP indicate generally upward migration of foci before the main event; (3) changes in the extent of S-wave splitting: a large precursory increase is observed along the tensile stress direction and a small premonitory decrease along the compression direction. Similar but unidentical results have been obtained before another earthquake of magnitude 4 whereas all events of magnitude 3.5 or larger have been preceded by anomalous S-wave splitting along the tension direction. The various observed pre-earthquake processes appear to be interrelated and may be explained in terms of recent laboratory and theoretical results when applied to the tectonics of central Nevada. It seems highly desirable to attempt simultaneous observations of anomalous changes in more than one seismic process.

scholarly journals ANISOTROPY STUDY OF THE FEBRUARY 4TH 2008 SWARM IN NW PELOPONNESUS (GREECE)

2017 ◽  
Vol 43 (4) ◽  
pp. 2084 ◽  
Author(s):  
G. Kaviris ◽  
P. Papadimitriou ◽  
K. Makropoulos
Keyword(s):  
Time Delay ◽  
Shear Wave ◽  
Selection Criteria ◽  
Vertical Component ◽  
Polarization Direction ◽  
Normal Faulting ◽  
S Wave ◽  
Gulf Of Corinth ◽  
Moderate Earthquake ◽  
Wave Splitting

The Gulf of Corinth, located in central Greece, is characterized by normal faulting and by high seismicity since the antiquity. On 4 February 2008 a seismic swarm burst in NW Peloponnesus characterized by the occurrence of two moderate-size earthquakes of moment magnitudes 4.7 and 4.5, respectively. Analysis of the data revealed the existence of shear-wave splitting. The events that were chosen for the anisotropy study fit the selection criteria, having clear and impulsive S wave arrival phases on the horizontal components. In addition, the amplitude of the S wave phase on the vertical component was smaller than on the horizontal ones. The representations that were used to determine the polarization direction of the fast split shear wave, the time delay between the two split shear waves and the polarization direction of the source were the polarigram and the hodogram. The uniform fast shear wave polarizations, irrespective of the azimuth of each event, are consistent with the general NNE-SSW direction of extension in the Gulf and, therefore, in agreement with the extensive dilatancy anisotropy (EDA) model. Finally, a decrease of the time delay values was observed after the occurrence of the first moderate earthquake, implying changes of the medium’s properties.

The High-Frequency Decay Slope of Spectra (Kappa) for M≥3.5 Earthquakes on Rock Sites in Eastern and Western Canada

2020 ◽  
Vol 110 (2) ◽  
pp. 471-488 ◽  
Author(s):  
Samantha M. Palmer ◽  
Gail M. Atkinson
Keyword(s):  
Ground Motion ◽  
Classical Method ◽  
Vertical Component ◽  
Western Canada ◽  
S Wave ◽  
Motion Modeling ◽  
Eastern Canada ◽  
General Observation ◽  
Anelastic Attenuation ◽  
Two Parameters

ABSTRACT Spectral decay of ground-motion amplitudes at high frequencies is primarily influenced by two parameters: site-related kappa (κ0) and regional Q (quality factor, inversely proportional to anelastic attenuation). We examine kappa and apparent Q-values (Qa) for M≥3.5 earthquakes recorded at seismograph stations on rock sites in eastern and western Canada. Our database contains 20 earthquakes recorded on nine stations in eastern Canada and 404 earthquakes recorded on eight stations in western Canada, resulting in 105 and 865 Fourier amplitude spectra, respectively. We apply two different methods: (1) a modified version of the classical S-wave acceleration method; and (2) a new stacking method that is consistent with the use of kappa in ground-motion modeling. The results are robust with respect to the method used and also with respect to the frequency band selected, which ranges from 9 to 38 Hz depending on the region, event, and method. Kappa values obtained from the classical method are consistent with those of the stacked method, but the stacked method provides a lower uncertainty. A general observation is that kappa is usually larger, and apparent Q is smaller, for the horizontal component in comparison to the vertical component. We determine an average regional κ0=7  ms (horizontal) and 0 ms (vertical) for rock sites in eastern Canada; we obtain κ0=19  ms (horizontal) and 14 ms (vertical) for rock sites in western Canada. We note that kappa measurements are quite sensitive to details of data selection criteria and methodology, and may be significantly influenced by site effects, resulting in large site-to-site variability.

A comparative study of the anisotropic dynamic and static elastic moduli of unconventional reservoir shales: Implication for geomechanical investigations

Geophysics ◽  
2016 ◽  
Vol 81 (3) ◽  
pp. D245-D261 ◽  
Author(s):  
Jaime Meléndez-Martínez ◽  
Douglas R. Schmitt
Keyword(s):  
Bedding Plane ◽  
Horizontal Stress ◽  
Pressure Sensitivity ◽  
S Wave ◽  
Fracture Pressure ◽  
Highly Nonlinear ◽  
Rock Anisotropy ◽  
Minimum Stress ◽  
Sonic Logging ◽  
Static Elastic Moduli

We obtained the complete set of dynamic elastic stiffnesses for a suite of “shales” representative of unconventional reservoirs from simultaneously measured P- and S-wave speeds on single prisms specially machined from cores. Static linear compressibilities were concurrently obtained using strain gauges attached to the prism. Regardless of being from static or dynamic measurements, the pressure sensitivity varies strongly with the direction of measurement. Furthermore, the static and dynamic linear compressibilities measured parallel to the bedding are nearly the same whereas those perpendicular to the bedding can differ by as much as 100%. Compliant cracklike porosity, seen in scanning electron microscope images, controls the elastic properties measured perpendicular to the rock’s bedding plane and results in highly nonlinear pressure sensitivity. In contrast, those properties measured parallel to the bedding are nearly insensitive to stress. This anisotropy to the pressure dependency of the strains and moduli further complicates the study of the overall anisotropy of such rocks. This horizontal stress insensitivity has implications for the use of advanced sonic logging techniques for stress direction indication. Finally, we tested the validity of the practice of estimating the fracture pressure gradient (i.e., horizontal stress) using our observed elastic engineering moduli and found that ignoring anisotropy would lead to underestimates of the minimum stress by as much as 90%. Although one could ostensibly obtain better values or the minimum stress if the rock anisotropy is included, we would hope that these results will instead discourage this method of estimating horizontal stress in favor of more reliable techniques.

scholarly journals S-wave experiments for the exploration of a deep geothermal carbonate reservoir in the German Molasse Basin

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Britta Wawerzinek ◽  
Hermann Buness ◽  
Hartwig von Hartmann ◽  
David C. Tanner
Keyword(s):  
Upper Jurassic ◽  
Carbonate Reservoir ◽  
P Wave ◽  
Seismic Survey ◽  
Seismic Exploration ◽  
Molasse Basin ◽  
S Wave ◽  
Induced Earthquakes ◽  
Conversion Point ◽  
Facies Classification

AbstractThere are many successful geothermal projects that exploit the Upper Jurassic aquifer at 2–3 km depth in the German Molasse Basin. However, up to now, only P-wave seismic exploration has been carried out. In an experiment in the Greater Munich area, we recorded S-waves that were generated by the conventional P-wave seismic survey, using 3C receivers. From this, we built a 3D volume of P- to S-converted (PS) waves using the asymptotic conversion point approach. By combining the P-volume and the resulting PS-seismic volume, we were able to derive the spatial distribution of the vp/vs ratio of both the Molasse overburden and the Upper Jurassic reservoir. We found that the vp/vs ratios for the Molasse units range from 2.0 to 2.3 with a median of 2.15, which is much higher than previously assumed. This raises the depth of hypocenters of induced earthquakes in surrounding geothermal wells. The vp/vs ratios found in the Upper Jurassic vary laterally between 1.5 and 2.2. Since no boreholes are available for verification, we test our results against an independently derived facies classification of the conventional 3D seismic volume and found it correlates well. Furthermore, we see that low vp/vs ratios correlate with high vp and vs velocities. We interpret the latter as dolomitized rocks, which are connected with enhanced permeability in the reservoir. We conclude that 3C registration of conventional P-wave surveys is worthwhile.

Delineating a cased borehole in unconsolidated formations using dipole acoustic data from a nearby well

Geophysics ◽  
2021 ◽  
pp. 1-39
Author(s):  
Gu Xihao ◽  
Xiao-Ming Tang ◽  
Yuan-Da Su
Keyword(s):  
Shear Waves ◽  
Low Frequency ◽  
Well Being ◽  
Compressional Wave ◽  
Acoustic Imaging ◽  
Wave Radiation ◽  
Dipole Source ◽  
Compressional Waves ◽  
Single Well ◽  
Cased Borehole

A potential application for single-well acoustic imaging is the detection of an existing cased borehole in the vicinity of the well being drilled, which is important for drilling toward (when drilling a relief well), or away from (collision prevention), the existing borehole. To fulfill this application in the unconsolidated formation of shallow sediments, we propose a detection method using the low-frequency compressional waves from dipole acoustic logging. For this application, we perform theoretical analyses on elastic wave scattering from the cased borehole and derive the analytical expressions for the scattered wavefield for the incidence of compressional and shear waves from a borehole dipole source. The analytical solution, in conjunction with the elastic reciprocity theorem, provides a fast algorithm for modeling the whole process of wave radiation, scattering, and reception for the borehole acoustic detection problem. The analytical results agree well with those from 3D finite-difference simulations. The results show that compressional waves, instead of shear waves as commonly used for dipole acoustic imaging, are particularly advantageous for the borehole detection in the unconsolidated formation. Field data examples are used to demonstrate the application in a shallow marine environment, where dipole-compressional wave data in the measurement well successfully delineate a nearby cased borehole, validating our analysis results and application.

Polarization and coherence of 5 to 30 Hz seismic wave fields at a hard-rock site and their relevance to velocity heterogeneities in the crust

1990 ◽  
Vol 80 (2) ◽  
pp. 430-449 ◽  
Author(s):  
William Menke ◽  
Arthur L. Lerner-Lam ◽  
Bruce Dubendorff ◽  
Javier Pacheco
Keyword(s):  
Hard Rock ◽  
Scale Effects ◽  
Spatial Coherence ◽  
Compressional Wave ◽  
P Wave ◽  
Transverse Motion ◽  
S Wave ◽  
Chemical Explosions ◽  
Aperture Arrays ◽  
The Waves

Abstract Except for its very onset, the P wave of earthquakes and chemical explosions observed at two narrow-aperture arrays on hard-rock sites in the Adirondack Mountains have a nearly random polarization. The amount of energy on the vertical, radial, and transverse components is about equal over the frequency range 5 to 30 Hz, for the entire seismogram. The spatial coherence of the seismograms is approximately exp(−cfΔx), where c is in the range 0.4 to 0.7 km−1Hz−1, f is frequency and Δx is the distance between array elements. Vertical, radial, and transverse components were quite coherent over the aperture of the array, indicating that the transverse motion of the compressional wave is a property of relatively large (106 m3) volumes of rock, and not just an anomaly caused by a malfunctioning instrument, poor instrument-rock coupling, or out-crop-scale effects. The spatial coherence is approximately independent of component, epicentral azimuth and range, and whether P- or S-wave coda is being considered, at least for propagation distances between 5 and 170 km. These results imply a strongly and three-dimensionally heterogeneous crust, with near-receiver scattering in the uppermost crust controlling the coherence properties of the waves.

S‐wave Splitting Intensity Analysis and Inversion

2018 ◽  
Author(s):  
Daniele Boiero ◽  
Claudio Bagaini
Keyword(s):  
Intensity Analysis ◽  
S Wave ◽  
Wave Splitting ◽  
And Inversion

scholarly journals Metode Seismik dalam Pemodelan Fisis Letusan Gunung Lumpur Bledug Kuwu

2019 ◽  
Vol 2 (2) ◽  
pp. 61-66
Author(s):  
Ahmad Fauzi Pohan ◽  
Rusnoviandi Rusnoviandi
Keyword(s):  
Wave Velocity ◽  
Physical Modeling ◽  
Vertical Component ◽  
Dominant Frequency ◽  
P Wave ◽  
Physical Parameters ◽  
S Wave ◽  
Interesting Phenomenon ◽  
Central Java ◽  
P Wave Velocity

Aktivitas gunung lumpur Bledug Kuwu di Jawa  Tengah merupakan fenomena yang menarik dikaji menggunakan pemodelan fisis. Tujuan penelitian ini adalah mengetahui parameter dari medium gunung lumpur Bledug Kuwu. Adapun pemodelan fisis yang dilakukan dengan menggunakan media fisis akuarium berukuran 59 × 59 × 37,3 cm yang diisi material dari lumpur Bledug Kuwu. Sumber letusan dihasilkan dari tekanan kompresor yang dapat diatur kedalaman (10.5, 13, dan 15.5 cm) dan sudut (30o, 45o dan 60o) sumbernya. Sensor yang digunakan geophone komponen vertikal sebanyak 3 buah dengan durasi perekaman selama 5 dan 2,5 detik. Data diambil dengan frekuensi sampel 2 dan 4 kHz untuk masing-masing durasi perekaman. Konfigurasi sumber dan geophone dibuat sesuai dengan pemodelan fisisnya. Pengukuran desnsitas lumpur menunjukkan angka sebesar 1200 kg/m3. Berdasarkan hasil analisis seismogram model fisis diperoleh kecepatan perambatan gelombang-P pada medium lumpur Bledug Kuwu adalah sebesar 48,74 m/s,dan gelombang-S sebesar 28,14 m/s dengan frekuensi dominan antara 20 sampai 25 Hz.   Bledug Kuwu mud volcano activity in Central Java is an interesting phenomenon to be studied using both physical  modeling. The objective of this study was to determine the physical parameters of the medium of Bledug Kuwu. The Physical model was an aquarium with a dimension of 59 × 59 × 37.3 cm filled with Bledug Kuwu’s mud. The eruption source is generated by a compressor pressure that can be controled both the depth(10.5, 13, and 15.5 cm) and the angel of the source (30o, 45o and 60o). The resulting seismic signals were recorded by using 3 vertical component geophones for 10 and 5 seconds durations at a frequency of 2 and 4 kHz respectivel, mud density 1200 kg/m3 . The physical modeling shows that the P-wave velocity of the Bledug Kuwu’s medium is 48.7 m/s, S-wave velocity of Bledug Kuwu’s is 28,14 m/s  with a dominant frequency of 20 to 25 Hz.

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