compressional wave
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2022 ◽  
Vol 61 (1) ◽  
pp. 40-54
Author(s):  
Jaime Meléndez Martínez ◽  
Rubén Nicolás López ◽  
Oscar C Valdiviezo

In this work, wet bulk density ?WBD and compressional wave velocity VP core log data obtained along the AND-2A drillcore are plotted on density-velocity ternary mineral Rock Physics Templates (RPTs) built from a Self-Consistent (SC) micromechanics modelling with the purpose to deter- mine data trends that allow us to assist in identifying mineral lithotypes and lithological features throughout the 1138 m length of the drillcore. The elastic properties of the three dominant miner- als present in the drillcore (mixed clays, quartz, and calcite) and the pore-filling fluid (brine) were used as input data for the SC model. The interpreted lithology is then compared to that obtained from the analysis of the AND-2A drillcore ?WBD and VP log data using Gardner type density-velocity cross plots. Results from both the SC and Gardner methods are in good agreement with the main lithologies present in the AND-2A drillcore already reported in the scientific literature. Our findings also agree well when compared to the lithological description of six selected rock samples obtained at different depths on the AND-2A drillcore. These results suggest that the proposed SC approach could be helpful to assist to identify lithology in scientific drill holes where downhole elastic proper- ties may exist over intervals where portions of the drillcore were not recovered. Furthermore, even when elastic property data sets come from measurements on cores, the SC approach is likewise useful because, from visual analysis alone, lithology can sometimes be difficult to determine, and additional information from the analysis of the elastic properties may provide more insight.


2021 ◽  
Author(s):  
ahmed wattan ◽  
Mohammed AL‑Jawad

Abstract Shear and compressional wave velocities are useful for drilling operations, the exploration of reservoirs, stimulation processes, and hydraulic fracturing. An ultrasonic device will be used in this investigation to anticipate and analyze the elastic characteristics of carbonate rocks. At the summit of the field, the well WQ1-20 obtained samples of the Mishrif formation from a variety of various depths. The number of samples taken from the well is nine from different units whereas the number of samples taken from the main unit (MB2) was five. The relations between the elastic properties for the carbonate rocks with P-and S-waves were defined. The relations between Vp and Vs with elastic properties were defined by applied Regression analysis. The results showed that a linear relationship between P-and S-wave velocities with the elastic properties of the carbonate rocks. It is found that the relationship between Vp and Young's modulus (E) is R2 equal to 0.979 while the relationship between Vs and Young's modulus (E) is R2 equal to 0.925. The relationship between shear modulus and Vs is good in comparison with Vp where the values of R2 were 0.985 and 0.94 respectively. R2 values for the Bulk modulus and Lame's constant of Vp are 0.925 and 0.6, respectively, while the values for Vs are 0.925 and 0.6 for the latter. The relation between Vp/Vs ratio with Poisson’s ratio showed a good R2 with a value of 0.97. When it comes to predicting the dynamic elastic characteristics of a material, the ultrasonic approach may be regarded as a cost-effective, easy, and non-destructive method.


Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Duoxing Yang ◽  
Lianzhong Zhang

Propagation of pore pressure and stress in water-saturated elastic porous media is theoretically investigated when considering the Darcy-Brinkman law. The wave mode, phase velocity, phase lag, damping factor, and characteristic frequency are found from the updated mathematic model. The Brinkman term describes the fluid viscous shear effects and importantly contributes to the dispersion relation and wave damping. The coincidence of the properties of Biot waves of the first and second kinds occurs at a characteristic frequency, which is remarkably influenced by the Brinkman term. A key finding is that, compared to the Darcy-Brinkman law, Darcy’s law overestimates the phase velocity, damping, and phase lag of the first wave, while underestimates the phase velocity, damping, and phase difference of the second wave. The introduction of the Darcy-Brinkman law yields an improved description of the damping of the compressional wave modes in saturated porous media.


2021 ◽  
Vol 93 (2) ◽  
pp. 104-127
Author(s):  
Raul Mollehuara-Canales ◽  
◽  
Nikita Afonin ◽  
Elena Kozlovskaya ◽  
Juha Lunkka ◽  
...  

We applied active-source seismic method for the interpretation of elastic parameters in tailings facilities which is essential for evaluating stability and seismic response. The methodology uses different analysis methods on the same dataset, i.e., conventional seismic refraction (SR) to determine compressional-wave velocity (Vp) and multichannel analysis of surface wave (MASW) to estimate shear-wave velocity (Vs). Seismic velocities in conjunction with tailings physics approach revealed interpretable data in terms of elastic parameters and hydrogeological conditions. The results determined the empirical linear relationships between Vp and Vs that are particular to an unconsolidated media such as tailings and showed that variability of hydrogeological conditions influences the elastic seismic response (Vp and Vs) and the elastic parameters. The analysis of the elastic parameters identified the state condition of the tailings at the time of the survey. The Bulk modulus K that relates the change in hydrostatic stress to the volumetric strain was predominant between 1.0−2.0 GPa. The Young’s modulus E in the tailings media was in the low range of 0.15−0.23 GPa. Poisson’s ratio values in all sections were in the upper limit in the range of 0.37−0.49, meaning that the tailings media is highly susceptible to transverse deformation under axial compression.


2021 ◽  
Author(s):  
Michael Begnaud ◽  
Sanford Ballard ◽  
James Hipp ◽  
Andre Encarnacao ◽  
Christopher Young ◽  
...  

SPE Journal ◽  
2021 ◽  
pp. 1-10
Author(s):  
Jing Fu ◽  
Carl Sondergeld ◽  
Chandra Rai

Summary Elastic wave velocities are commonly used to predict porosity, mineralogy, and lithology from formation properties. When only P-wave sonics are available in historical wells, systematics for predicting shear velocities are useful for developing elastic models. Although much research has been done on conventional reservoir velocity systematics, the equivalency for unconventional formations is still a work in progress. There has also been a limited number of research studies with laboratory measures published. Using laboratory pulse transmission ultrasonic data, we created a Vp-Vs systematic for the Meramec Formation in this study. The effects of porosity and mineralogy on velocities are explored, as well as a comparison of Meramec velocity systematics with well-established literature systematics. Vp and Vs measurements were taken on 385 dodecane-saturated core samples from seven Meramec wells (106 vertical and 279 horizontal plugs). S-wave and P-wave anisotropy in Meramec Formation samples used in this study are typically less than 10%. Each sample was also tested for porosity and mineralogy. We find that velocities are more sensitive to porosity than mineralogy by a factor of 10. Below are our equations for predicting Vp and Vs (in km/s), when only clay content and porosity are known. In these equations, φ is the volume fraction pores, and Clays is the weight fraction of clay. These equations are for those samples in which there is low P-wave and S-wave anisotropies:(1)Vp=6.4−1.2*Clays−15.4*φ(R2=0.5),(2)Vs=3.6−0.5*Clays−5.2*φ(R2=0.4). We suggest two methods for calculating Vs from Vp: Ignoring anisotropy, we combined both Vp and Vs measurements from all vertical plugs and low anisotropy horizontal plugs to create a single shear wave predictor; and considering anisotropy, Vp measurements from horizontal plugs were corrected using Thomsen’s compressional wave anisotropy parameter, after which a shear velocity predictor was generated. The shear wave predictors for dodecane-saturated measurements are as follows (all velocities are km/s):(3)Method 1: Vs= 0.90 + 0.42*Vp (R2=0.7),(4)Method 2: Vs= 0.80 + 0.45*Vp (R2=0.6). The residual and estimated error in Eq. 3 is slightly less than in Eq. 4. Even though there is a significant variance in measurement frequency, the Meramec velocity systematic shows good agreement with dipole wireline measurements using the first equation. The Meramec velocity systematics differ significantly from previously published systematics, such as the trend line by Greenberg and Castagna (1992) and the shale trend line by Vernik et al. (2018). Using the correlations by Greenberg and Castagna (1992) for limestone or dolomite, the shear velocities of the samples in this study cannot be predicted. These data have yielded shear wave systematics, which can be used in wireline and seismic investigations. The results suggest that the method of ignoring anisotropy yields a better Vs estimate than the one that takes anisotropy into account. Using well-established shear wave velocity systematics from the published literature can result in an estimated inaccuracy of greater than 16%. It is important to calibrate velocity systematics to the target formation.


2021 ◽  
Vol 60 (4) ◽  
pp. 294-319
Author(s):  
Joseline Mena-Negrete ◽  
Oscar C. Valdiviezo-Mijangos ◽  
Enrique Coconi-Morales ◽  
Rubén Nicolás-López

This work presents an approach to characterize the pore-structure and anisotropy in carbonate samples based on the Effective Medium Method (EMM). It considers a matrix with spheroidal inclusions which induce a transverse anisotropy. The compressional wave (VP), vertical (VSV)  and horizontal (VSH)  shear wave velocities are estimated taking into account parameters as characteristic length, frequency, angle of wave incidence, aspect ratio, mineralogy, and pore-filling fluid to predict pore shape in carbonates. Ranges of aspect ratios are shown to discriminate different pore types: intercrystalline, intergranular, moldic, and vuggy. The angle of wave incidence is a determinant parameter in the estimation of VP(0º, 45º, 90º), VSV(0º) and VSH(90º) to calculate dynamic anisotropic Young’s modulus (E33) and Poisson’s ratio (v31), as well as the Thomsen parameters, Epsilon, Gamma and Delta for quantification of the anisotropic pore-structure. The obtained results establish that the size, as well as the pore-structure, have a more significant impact on the elastic properties when the porosity takes values greater than 4% for the three frequencies, ultrasonic, sonic, and seismic. This investigation predicts the pore-structure and pore-size to improve characterization and elastic properties modeling of carbonate reservoirs. Validation of results includes porosity measurements and ultrasonic velocity data for different carbonate samples.


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