Laboratory ultrasonic measurements: Shear transducers for compressional waves

2019 ◽  
Vol 38 (5) ◽  
pp. 392-399 ◽  
Author(s):  
Alexey Yurikov ◽  
Nazanin Nourifard ◽  
Marina Pervukhina ◽  
Maxim Lebedev
Keyword(s):  
Elastic Properties ◽  
Elastic Waves ◽  
High Energy ◽  
P Wave ◽  
P Waves ◽  
S Waves ◽  
Wave Velocities ◽  
Dipole Structure ◽  
Ultrasonic Measurements ◽  
P Wave Velocities

The ultrasonic measurements technique is well established to measure the elastic properties of rocks in the laboratory for seismic and well-log data interpretation. The key components of every laboratory ultrasonic setup are piezoelectric transducers, which generate and register elastic waves in rock samples. The elastic properties of rocks are determined through the velocities of elastic waves, which are measured by the times of the waves' travel from the source to the receiver transducer. Transducers can be specifically designed to generate P-waves (P-transducers) or S-waves (S-transducers). In limited studies, the measurement of P-wave velocities with S-transducers is mentioned. Such measurement is possible due to specific aspects of the operation of S-transducers. Namely, S-transducers are known to emit parasitic low-energy P-waves, which travel faster than high-energy S-waves and hence can be registered. However, no justification or elaboration of this method of measuring P-wave velocities was reported. To fill this gap, we first compare P-wave velocities measured with S-transducers against P-wave velocities measured with P-transducers in different rocks and materials. We show that the discrepancy between velocities measured with the two methods in homogeneous materials is less than 1% and can be up to 4% for natural rocks. Second, we numerically simulate the operation of S-transducers, show that parasitic P-waves have a dipole structure, and explain how the receiver transducer can register this compressional dipole. Finally, we use laser doppler interferometry to measure the displacement of the free surface of a sample caused by elastic waves emitted by the source S-transducer. We observed the dipole structure of the sample's surface displacement upon P-wave arrival on the surface.

scholarly journals Upscaling of elastic properties in carbonates: A modeling approach based on a multiscale geophysical data set

2020 ◽  
Author(s):  
Jerome Fortin ◽  
Cedric Bailly ◽  
Mathilde Adelinet ◽  
Youri Hamon
Keyword(s):  
Elastic Properties ◽  
Wave Velocity ◽  
Representative Elementary Volume ◽  
P Wave ◽  
Elementary Volume ◽  
Data Set ◽  
Wave Velocities ◽  
P Wave Velocity ◽  
Ultrasonic Measurements ◽  
Seismic Scale

<p>Linking ultrasonic measurements made on samples, with sonic logs and seismic subsurface data, is a key challenge for the understanding of carbonate reservoirs. To deal with this problem, we investigate the elastic properties of dry lacustrine carbonates. At one study site, we perform a seismic refraction survey (100 Hz), as well as sonic (54 kHz) and ultrasonic (250 kHz) measurements directly on outcrop and ultrasonic measurements on samples (500 kHz). By comparing the median of each data set, we show that the P wave velocity decreases from laboratory to seismic scale. Nevertheless, the median of the sonic measurements acquired on outcrop surfaces seems to fit with the seismic data, meaning that sonic acquisition may be representative of seismic scale. To explain the variations due to upscaling, we relate the concept of representative elementary volume with the wavelength of each scale of study. Indeed, with upscaling, the wavelength varies from millimetric to pluri-metric. This change of scale allows us to conclude that the behavior of P wave velocity is due to different geological features (matrix porosity, cracks, and fractures) related to the different wavelengths used. Based on effective medium theory, we quantify the pore aspect ratio at sample scale and the crack/fracture density at outcrop and seismic scales using a multiscale representative elementary volume concept. Results show that the matrix porosity that controls the ultrasonic P wave velocities is progressively lost with upscaling, implying that crack and fracture porosity impacts sonic and seismic P wave velocities, a result of paramount importance for seismic interpretation based on deterministic approaches.</p><p>Bailly, C., Fortin, J., Adelinet, M., & Hamon, Y. (2019). Upscaling of elastic properties in carbonates: A modeling approach based on a multiscale geophysical data set. Journal of Geophysical Research: Solid Earth, 124. https://doi.org/10.1029/2019JB018391</p>

Laboratory velocities and attenuation of P‐waves in limestones during freeze‐thaw cycles

Geophysics ◽  
1994 ◽  
Vol 59 (2) ◽  
pp. 245-251 ◽  
Author(s):  
Jean‐Michel Remy ◽  
Michel Bellanger ◽  
Françoise Homand‐Etienne
Keyword(s):  
Hydrostatic Compression ◽  
P Wave ◽  
Compression Tests ◽  
Freezing And Thawing ◽  
P Waves ◽  
Freeze Thaw ◽  
Rock Samples ◽  
Wave Velocities ◽  
P Wave Velocities ◽  
Freezing And Thawing Cycles

The velocity and the attenuation of compressional P‐waves, measured in the laboratory at ultrasonic frequencies during a series of freezing and thawing cycles, are used as a method for predicting frost damage in a bedded limestone. Pulse transmission and spectral ratio techniques are used to determine the P‐wave velocities and the attenuation values relative to an aluminum reference sample with very low attenuation. Limestone samples were water saturated under vacuum conditions, jacketed with rubber sleeves, and immersed in an antifreeze bath (50 percent methanol solution). They were submitted to repeated 24-hour freezing and thawing cycles simulating natural environment conditions. During the freeze/thaw cycles, P‐wave velocities and quality factor Q diminished rapidly in thawed rock samples, indicating modification of the pore space. Measurements of crack porosity were conducted by hydrostatic compression tests on cubic rock samples that had been submitted to these freeze/thaw cycles. These measurements are used as an index of crack formation. The hydrostatic compression tests confirmed the phases of rock damage that were shown by changes in the value of Q. Furthermore, comparisons between Q values and crack porosity demonstrated that the variations of P‐wave attenuation are caused by the creation of new cracks and not by the enlargement of pre‐existing cracks.

ANALYSIS OF ACOUSTIC PROPERTIES OF RESERVOIR ROCKS FROM RUNOVSCHYNSKA FIELD ON THE BASIS OF PETROPHYSICAL STUDIES IN VARIOUS PRESSURE CONDITIONS

2019 ◽  
pp. 21-26
Author(s):  
I. Bezrodna ◽  
S. Vyzhva
Keyword(s):  
Wave Velocity ◽  
Acoustic Properties ◽  
P Wave ◽  
Variable Pressure ◽  
Atmospheric Conditions ◽  
Void Space ◽  
Correlation Dependence ◽  
P Waves ◽  
Wave Velocities ◽  
P Wave Velocities

The results of rock physics study of 68 core samples from well No. 110 of the Runovshchynska field of the Dnipro-Donets depression in Ukraine are presented. Investigation of the P-waves on samples under different pressure conditions with the use of 'Kern-4' and high pressure VSC-1000 was performed. Analysis of the obtained data and calculated reservoir values of P-waves was performed. The character of the change in velocity of P- and S-waves for atmospheric conditions is considered. It is shown that the predominant amount of water saturated samples has a velocity of P-waves 3200–3500 m/s (dry samples 2100–2550 m/s), and the S-wave velocity for saturated samples is 2100–2550 m/s (dry specimens 1400–1500 m/s). For a collection of samples, which were measured in atmospheric conditions, the correlation dependence between velocities of P-waves and their density with a close correlation was established. Correlation dependences between elastic wave velocities and the connected porosity of saturated samples were investigated. The dependences of type Vð = f (Kð) with high correlation coefficient for three separate picks of the homotypic sandstones were established. During the analysis of the acoustic studies results under conditions of variable pressure for the majority of samples from the studied intervals, the authors obtained the following common factors. The values of the P-wave velocity, measured in atmospheric conditions, are always smaller than the values obtained after the removal of the pressure; however, there are sometimes quite noticeable fluctuations in their difference, which can be explained by a sharp (possibly hopping) closure of microcracks in the rock with increasing pressure and their delayed opening or non-disclosure when it is reduced. The most contrasting changes in the behavior of the P-wave velocities are haracteristic for several samples (Nos. 27, 48, 50, 53/1), which is most likely due to the void space structure in the rocks, possibly with an increased number of microcracks compared with other samples. On the basis of a priori data and the results of researches of samples at variable pressures, the authors calculated the P-wave velocities in reservoir conditions, conducted their comparative analysis with velocities that are characteristic for samples in atmospheric conditions, built a tight (R² = 0,85) correlation dependence of the investigated parameters.

Effect of Fluids on the Elastic Properties of 3D-Printed Anisotropic Rock Models

2021 ◽  
Vol 62 (5) ◽  
pp. 537-552
Author(s):  
Suresh Dande ◽  
◽  
Robert R. Stewart ◽  
Nikolay Dyaur ◽  
◽  
...  
Keyword(s):  
Wave Propagation ◽  
Elastic Properties ◽  
P Wave ◽  
Engine Oil ◽  
Rock Properties ◽  
Anisotropic Rock ◽  
Wave Velocities ◽  
Inclusion Model ◽  
3D Printed ◽  
Primary Porosity

Laboratory physical models play an important role in understanding rock properties and wave propagation, both theoretically and at the field scale. In some cases, 3D-printing technology can be adopted to construct complex rock models faster, more inexpensively, and with more specific features than previous model-building techniques. In this study, we use 3D-printed rock models to assist in understanding the effects of various fluids (air, water, engine oil, crude oil, and glycerol) on the models’ elastic properties. We first used a 3D-printed, 1-in. cube-shaped layered model. This model was created with a 6% primary porosity and a bulk density of 0.98 g/cc with VTI anisotropy. We next employed a similar cube but with horizontal inclusions embedded in the layered background, which contributed to its total 24% porosity (including primary porosity). For air to liquid saturation, P-velocities increased for all liquids in both models, with the highest increase being with glycerol (57%) and an approximately 45% increase for other fluids in the inclusion model. For the inclusion model (dry and saturated), we observed a greater difference between two orthogonally polarized S-wave velocities (Vs1 and Vs2) than between two P-wave velocities (VP0 and VP90). We attribute this to the S2-wave (polarized normal to both the layering and the plane of horizontal inclusions), which appears more sensitive to horizontal inclusions than the P-wave. For the inclusion model, Thomsen’s P-wave anisotropic parameter (ɛ) decreased from 26% for the air case to 4% for the water-saturated cube and to 1% for glycerol saturation. The small difference between the bulk modulus of the frame and the pore fluid significantly reduces the velocity anisotropy of the medium, making it almost isotropic. We compared our experimental results with theory and found that predictions using Schoenberg’s linear slip theory combined with Gassmann’s anisotropic equation were closer to actual measurements than Hudson’s isotropic calculations. This work provides insights into the usefulness of 3D-printed models to understand elastic rock properties and wave propagation under various fluid saturations.

Numerical simulation of azimuthal acoustic logging in a borehole penetrating a rock formation boundary

Geophysics ◽  
2016 ◽  
Vol 81 (3) ◽  
pp. D283-D291 ◽  
Author(s):  
Peng Liu ◽  
Wenxiao Qiao ◽  
Xiaohua Che ◽  
Xiaodong Ju ◽  
Junqiang Lu ◽  
...  
Keyword(s):  
Domain Model ◽  
P Wave ◽  
S Wave ◽  
Angle Variation ◽  
P Waves ◽  
Acoustic Logging ◽  
S Waves ◽  
Rock Formation ◽  
Logging Tool ◽  
Difference Time

We have developed a new 3D acoustic logging tool (3DAC). To examine the azimuthal resolution of 3DAC, we have evaluated a 3D finite-difference time-domain model to simulate a case in which the borehole penetrated a rock formation boundary when the tool worked at the azimuthal-transmitting-azimuthal-receiving mode. The results indicated that there were two types of P-waves with different slowness in waveforms: the P-wave of the harder rock (P1) and the P-wave of the softer rock (P2). The P1-wave can be observed in each azimuthal receiver, but the P2-wave appears only in the azimuthal receivers toward the softer rock. When these two types of rock are both fast formations, two types of S-waves also exist, and they have better azimuthal sensitivity compared with P-waves. The S-wave of the harder rock (S1) appears only in receivers toward the harder rock, and the S-wave of the softer rock (S2) appears only in receivers toward the softer rock. A model was simulated in which the boundary between shale and sand penetrated the borehole but not the borehole axis. The P-wave of shale and the S-wave of sand are azimuthally sensitive to the azimuth angle variation of two formations. In addition, waveforms obtained from 3DAC working at the monopole-transmitting-azimuthal-receiving mode indicate that the corresponding P-waves and S-waves are azimuthally sensitive, too. Finally, we have developed a field example of 3DAC to support our simulation results: The azimuthal variation of the P-wave slowness was observed and can thus be used to reflect the azimuthal heterogeneity of formations.

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