Tube-wave monitoring as a method to detect shear modulus changes around boreholes: A case study

Geophysics ◽  
2021 ◽  
pp. 1-69
Author(s):  
Daniel Wehner ◽  
Filipe Borges ◽  
Martin Landrø
Keyword(s):  
Shear Modulus ◽  
Body Waves ◽  
Rock Properties ◽  
Step Method ◽  
Monitoring Method ◽  
Near Surface ◽  
Wave Measurements ◽  
Geological Formation ◽  
Tube Wave ◽  
Borehole Seismic

Monitoring the shear modulus of formations around boreholes is of interest for various applications, ranging from near-surface investigation to reservoir monitoring. Downhole logging tools and borehole seismic are common techniques applied to measure and characterize formation properties. These methods rely on transmitted and reflected waves to retrieve the rock properties. Wave modes travelling along the interface between the well and the formation, such as tube waves, are often considered as noise. However, tube waves are less attenuated than body waves, and contain information about the shear modulus of the formation surrounding the well. Hence, a potential use of this interface wave is of interest. As tube-wave properties depend on several parameters, e.g. well geometry, highly accurate measurements should be performed for use in inferring rock properties. We study the feasibility of tube-wave measurements as a monitoring method. Different experiments are conducted using a hydrophone array in two boreholes, with depths of 30 m and 95 m. The experiments are used to investigate how accurate the tube-wave velocity can be measured, and which parameters have most impact on the measurements. Our results suggest that it is hard to estimate the absolute shear modulus of the geological formation using tube-wave velocities only. However, it seems feasible to use them to monitor changes of the shear modulus, depending on the borehole set up and geological formation. The tube-wave monitoring can be used as a first step method to determine the depth along the well where changes occur before more accurate measurements are performed in a second step.

Seismic inversion of soil damping and stiffness using multichannel analysis of surface wave measurements in the marine environment

2020 ◽  
Vol 221 (2) ◽  
pp. 1439-1449
Author(s):  
M A Armstrong ◽  
M Ravasio ◽  
W G Versteijlen ◽  
D J Verschuur ◽  
A V Metrikine ◽  
...  
Keyword(s):  
Shear Modulus ◽  
Frequency Dependence ◽  
Measurement Errors ◽  
Damping Ratio ◽  
Seismic Inversion ◽  
Material Damping ◽  
Near Surface ◽  
Soil Material ◽  
Wave Measurements ◽  
Degree Of Certainty

SUMMARY Determination of soil material damping is known to be difficult and uncertain, especially in the offshore environment. Using an advanced inversion methodology based on multichannel spectral analysis, Scholte and Love wave measurements are used to characterize subsea soil from a North Sea site. After normalization, a determinant-based objective function is used in a genetic algorithm optimization to estimate the soil shear modulus. The inverted shear-modulus profile is comparable to previously published results for the same data, although a higher degree of certainty is achieved in the near-surface layers. The half-power bandwidth method is used for extracting the attenuation curve from the measurements and efficient reference data points are chosen based on wavelet compression. The material-damping ratio inversion is performed using a modified stochastic optimization algorithm. Accounting for measurement errors, the material-damping ratio profile is retrieved from the fundamental-mode Scholte wave with a high degree of certainty. Furthermore, a method is proposed for identifying the frequency dependence of the material-damping ratio from in situ measurements. No evidence for frequency dependence is found and the small-strain soil material-damping ratio at this site can be said to be frequency independent for the measured conditions.

Acoustic modes of propagation in the borehole and their relationship to rock properties

Geophysics ◽  
1982 ◽  
Vol 47 (8) ◽  
pp. 1215-1228 ◽  
Author(s):  
F. L. Paillet ◽  
J. E. White
Keyword(s):  
Elastic Solid ◽  
Body Waves ◽  
Radioactive Waste Disposal ◽  
Plane Geometry ◽  
Rock Properties ◽  
Geometry Model ◽  
Head Waves ◽  
Time Domain Response ◽  
Tube Wave ◽  
The Time Domain

Acoustic waveform measurements in boreholes have important applications in fracture hydrology and radioactive waste disposal, but ambiguities in existing interpretation techniques remain a problem. We have addressed the problem by using residue theory to predict the relative excitation of various modes contained in experimental waveforms. A plane‐geometry model involving a layer of fluid between two elastic half‐spaces is shown to provide velocity dispersion curves for propagating modes that are very similar to those for the fluid‐filled borehole. We use the plane‐geometry model to illustrate the effects of the confined borehole fluid on surface and body waves traveling along the borehole in the elastic solid. We also computed excitation functions for some of the lowest‐order symmetric modes, calculated the time‐domain response of the trapped modes following the shear head waves, and compared them to waveforms recorded in boreholes through several homogeneous formations. The insight into the mode composition of the experimental waveforms obtained in these formations is used to construct amplitude logs that should be especially sensitive to variations in the presence of fluid‐filled fractures in the borehole wall. Initial tests show the technique is most successful when the waveform is dominated by the fundamental tube wave, and yet frequencies remain relatively high. The model analysis indicates these conditions can only be obtained when the borehole diameter is not much larger than that of the logging tool.

Surface and near-surface effects on seismic waves—theory and borehole seismometer results

1987 ◽  
Vol 77 (4) ◽  
pp. 1168-1196
Author(s):  
P. M. Shearer ◽  
J. A. Orcutt
Keyword(s):  
Free Surface ◽  
Plane Wave ◽  
Seismic Waves ◽  
Wave Model ◽  
Body Waves ◽  
P Wave ◽  
Surface Velocity ◽  
Ocean Bottom ◽  
Near Surface ◽  
Borehole Seismic

Abstract A simple plane wave model is adequate to explain many surface versus borehole seismometer data sets. Using such a model, we present a series of examples which demonstrate the effects of the free-surface, near-surface velocity gradients, and low impedance surface layers on the amplitudes of upcoming body waves. In some cases, these amplitudes are predictable from simple free-surface and impedance contrast expressions. However, in other cases these expressions are an unreliable guide to the complete response, and the full plane wave calculation must be performed. Large surface amplifications are possible, even without focusing due to lateral heterogeneities or nonlinear effects. Both surface and borehole seismometer site responses are almost always frequency-dependent. Ocean bottom versus borehole seismic data from the 1983 Ngendei Seismic Experiment in the southwest Pacific are consistent with both a simple plane wave model and a more complete synthetic seismogram calculation. The borehole seismic response to upcoming P waves is reduced at high frequencies because of interference between the upgoing P wave and downgoing P and SV waves reflected from the sediment-basement interface. However, because of much lower borehole noise levels, the borehole seismometer enjoys a P-wave signal-to-noise advantage of 3 to 7 dB over nearby ocean bottom instruments.

Effect of Dynamic Crosslinking on Mechanical Properties of PP/EPDM Blends

1993 ◽  
Vol 58 (11) ◽  
pp. 2642-2650 ◽  
Author(s):  
Zdeněk Kruliš ◽  
Ivan Fortelný ◽  
Josef Kovář
Keyword(s):  
Mechanical Properties ◽  
Impact Strength ◽  
Shear Modulus ◽  
High Impact ◽  
Necessary Condition ◽  
Step Method ◽  
Melt Mixing ◽  
One Step ◽  
High Impact Strength ◽  
Dynamic Curing

The effect of dynamic curing of PP/EPDM blends with sulfur and thiuram disulfide systems on their mechanical properties was studied. The results were interpreted using the knowledge of the formation of phase structure in the blends during their melt mixing. It was shown, that a sufficiently slow curing reaction is necessary if a high impact strength is to be obtained. Only in such case, a fine and homogeneous dispersion of elastomer can be formed, which is the necessary condition for high impact strength of the blend. Using an inhibitor of curing in the system and a one-step method of dynamic curing leads to an increase in impact strength of blends. From the comparison of shear modulus and impact strength values, it follows that, at the stiffness, the dynamically cured blends have higher impact strength than the uncured ones.

scholarly journals Near-surface real-time seismic imaging using parsimonious interferometry

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sherif M. Hanafy ◽  
Hussein Hoteit ◽  
Jing Li ◽  
Gerard T. Schuster
Keyword(s):  
Fluid Flow ◽  
Real Time ◽  
Temporal Resolution ◽  
Seismic Imaging ◽  
Time Lapse ◽  
Rock Properties ◽  
Recording Time ◽  
Near Surface ◽  
Arrival Times ◽  
Order Of Magnitude

AbstractResults are presented for real-time seismic imaging of subsurface fluid flow by parsimonious refraction and surface-wave interferometry. Each subsurface velocity image inverted from time-lapse seismic data only requires several minutes of recording time, which is less than the time-scale of the fluid-induced changes in the rock properties. In this sense this is real-time imaging. The images are P-velocity tomograms inverted from the first-arrival times and the S-velocity tomograms inverted from dispersion curves. Compared to conventional seismic imaging, parsimonious interferometry reduces the recording time and increases the temporal resolution of time-lapse seismic images by more than an order-of-magnitude. In our seismic experiment, we recorded 90 sparse data sets over 4.5 h while injecting 12-tons of water into a sand dune. Results show that the percolation of water is mostly along layered boundaries down to a depth of a few meters, which is consistent with our 3D computational fluid flow simulations and laboratory experiments. The significance of parsimonious interferometry is that it provides more than an order-of-magnitude increase of temporal resolution in time-lapse seismic imaging. We believe that real-time seismic imaging will have important applications for non-destructive characterization in environmental, biomedical, and subsurface imaging.

scholarly journals Rock Location and Property Analysis of Lunar Regolith at Chang’E-4 Landing Site Based on Local Correlation and Semblance Analysis

2020 ◽  
Vol 13 (1) ◽  
pp. 48
Author(s):  
Hanjie Song ◽  
Chao Li ◽  
Jinhai Zhang ◽  
Xing Wu ◽  
Yang Liu ◽  
...  
Keyword(s):  
Electromagnetic Waves ◽  
Lunar Regolith ◽  
Landing Site ◽  
Rock Properties ◽  
The Moon ◽  
Local Correlation ◽  
Near Surface ◽  
Property Analysis ◽  
Stratigraphic Division ◽  
Formation And Evolution

The Lunar Penetrating Radar (LPR) onboard the Yutu-2 rover from China’s Chang’E-4 (CE-4) mission is used to probe the subsurface structure and the near-surface stratigraphic structure of the lunar regolith on the farside of the Moon. Structural analysis of regolith could provide abundant information on the formation and evolution of the Moon, in which the rock location and property analysis are the key procedures during the interpretation of LPR data. The subsurface velocity of electromagnetic waves is a vital parameter for stratigraphic division, rock location estimates, and calculating the rock properties in the interpretation of LPR data. In this paper, we propose a procedure that combines the regolith rock extraction technique based on local correlation between the two sets of LPR high-frequency channel data and the common offset semblance analysis to determine the velocity from LPR diffraction hyperbola. We consider the heterogeneity of the regolith and derive the relative permittivity distribution based on the rock extraction and semblance analysis. The numerical simulation results show that the procedure is able to obtain the high-precision position and properties of the rock. Furthermore, we apply this procedure to CE-4 LPR data and obtain preferable estimations of the rock locations and the properties of the lunar subsurface regolith.

Tracking of velocity variations at depth in the presence of surface velocity fluctuations

Geophysics ◽  
2013 ◽  
Vol 78 (1) ◽  
pp. U1-U8 ◽  
Author(s):  
Benoit de Cacqueray ◽  
Philippe Roux ◽  
Michel Campillo ◽  
Stefan Catheline
Keyword(s):  
Surface Waves ◽  
Body Waves ◽  
Surface Velocity ◽  
Small Scale ◽  
Beam Forming ◽  
Near Surface ◽  
Velocity Fluctuations ◽  
Wave Separation ◽  
Double Beam ◽  
Velocity Variations

We tested a small-scale experiment that is dedicated to the study of the wave separation algorithm and to the velocity variations monitoring problem itself. It handles the case in which velocity variations at depth are hidden by near-surface velocity fluctuations. Using an acquisition system that combines an array of sources and an array of receivers, coupled with controlled velocity variations, we tested the ability of beam-forming techniques to track velocity variations separately for body waves and surface waves. After wave separation through double beam forming, the arrival time variations of the different waves were measured through the phase difference between the extracted wavelets. Finally, a method was tested to estimate near-surface velocity variations using surface waves or shallow reflection and compute a correction to isolate target velocity variations at depth.

scholarly journals Noise-based ballistic wave passive seismic monitoring. Part 1: body waves

2020 ◽  
Vol 221 (1) ◽  
pp. 683-691 ◽  
Author(s):  
F Brenguier ◽  
R Courbis ◽  
A Mordret ◽  
X Campman ◽  
P Boué ◽  
...  
Keyword(s):  
Seismic Velocity ◽  
Noise Source ◽  
Seismic Monitoring ◽  
Body Waves ◽  
P Wave ◽  
New Technique ◽  
Apparent Velocity ◽  
Near Surface ◽  
Velocity Increase ◽  
Passive Seismic

SUMMARY Unveiling the mechanisms of earthquake and volcanic eruption preparation requires improving our ability to monitor the rock mass response to transient stress perturbations at depth. The standard passive monitoring seismic interferometry technique based on coda waves is robust but recovering accurate and properly localized P- and S-wave velocity temporal anomalies at depth is intrinsically limited by the complexity of scattered, diffracted waves. In order to mitigate this limitation, we propose a complementary, novel, passive seismic monitoring approach based on detecting weak temporal changes of velocities of ballistic waves recovered from seismic noise correlations. This new technique requires dense arrays of seismic sensors in order to circumvent the bias linked to the intrinsic high sensitivity of ballistic waves recovered from noise correlations to changes in the noise source properties. In this work we use a dense network of 417 seismometers in the Groningen area of the Netherlands, one of Europe's largest gas fields. Over the course of 1 month our results show a 1.5 per cent apparent velocity increase of the P wave refracted at the basement of the 700-m-thick sedimentary cover. We interpret this unexpected high value of velocity increase for the refracted wave as being induced by a loading effect associated with rainfall activity and possibly canal drainage at surface. We also observe a 0.25 per cent velocity decrease for the direct P-wave travelling in the near-surface sediments and conclude that it might be partially biased by changes in time in the noise source properties even though it appears to be consistent with complementary results based on ballistic surface waves presented in a companion paper and interpreted as a pore pressure diffusion effect following a strong rainfall episode. The perspective of applying this new technique to detect continuous localized variations of seismic velocity perturbations at a few kilometres depth paves the way for improved in situ earthquake, volcano and producing reservoir monitoring.

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