Determining formation shear‐wave transverse isotropy from borehole Stoneley‐wave measurements

Geophysics ◽  
2003 ◽  
Vol 68 (1) ◽  
pp. 118-126 ◽  
Author(s):  
Xiaoming Tang
Keyword(s):  
Shear Wave ◽  
Transverse Isotropy ◽  
Wave Spectrum ◽  
Weighted Average ◽  
Stoneley Wave ◽  
Fast Method ◽  
Actual Structure ◽  
Stoneley Waves ◽  
Wave Data ◽  
Shale Formation

Many rocks exhibit transversely isotropic (TI) characteristics. For determining the TI property using acoustic logging, Stoneley waves are the only borehole wave mode that has a significant sensitivity to TI effects, especially when the formation is acoustically slow compared to the borehole fluid. This study describes a method for deriving the formation shear‐wave TI parameter from the Stoneley wave data acquired by a logging tool. It is shown that the presence of the tool in the borehole can substantially affect the Stoneley wave propagation. Fortunately, for low‐frequency Stoneley waves, the tool effect can be satisfactorily modeled using an effective modulus, regardless of the actual structure of the tool. The modulus can be determined from a calibration procedure. In the inversion processing of the Stoneley wave data, the Stoneley wave slowness is related to the weighted average of the wave's dispersion curve over the frequency range occupied by the wave spectrum. This provides a fast method for the inversion. As a processing example, this method has been applied to estimate the shear‐wave TI parameter profile for the Lewis shale formation in Braggs, Wyoming. The resulting profile delineates the shear‐wave anisotropy magnitude and variation for this shale formation.

Simulation of borehole sonic waveforms in dipping, anisotropic, and invaded formations

Geophysics ◽  
2011 ◽  
Vol 76 (4) ◽  
pp. E127-E139 ◽  
Author(s):  
Robert K. Mallan ◽  
Carlos Torres-Verdín ◽  
Jun Ma
Keyword(s):  
Wave Propagation ◽  
Shear Modulus ◽  
Symmetry Axis ◽  
Transverse Isotropy ◽  
Cutoff Frequency ◽  
Dispersion Curves ◽  
Flexural Wave ◽  
Stoneley Wave ◽  
Stoneley Waves ◽  
The Impact

A numerical simulation study has been made of borehole sonic measurements that examined shoulder-bed, anisotropy, and mud-filtrate invasion effects on frequency-dispersion curves of flexural and Stoneley waves. Numerical simulations were considered for a range of models for fast and slow formations. Computations are performed with a Cartesian 3D finite-difference time-domain code. Simulations show that presence of transverse isotropy (TI) alters the dispersion of flexural and Stoneley waves. In slow formations, the flexural wave becomes less dispersive when the shear modulus (c44) governing wave propagation parallel to the TI symmetry axis is lower than the shear modulus (c66) governing wave propagation normal to the TI symmetry axis; conversely, the flexural wave becomes more dispersive when c44 > c66. Dispersion decreases by as much as 30% at higher frequencies for the considered case where c44 < c66. Dispersion of Stoneley waves, on the other hand, increases in TI formations when c44 > c66 and decreases when c44 < c66. Dispersion increases by more than a factor of 2.5 at higher frequencies for the considered case where c44 < c66. Simulations also indicate that the impact of invasion on flexural and Stoneley dispersions can be altered by the presence of TI. For the case of a slow formation and TI, where c44 decreases from the isotropic value, separation between dispersion curves for cases with and without the presence of a fast invasion zone increases by as much as 33% for the flexural wave and by as much as a factor of 1.4 for the Stoneley wave. Lastly, presence of a shoulder bed intersecting the sonic tool at high dip angles can alter flexural dispersion significantly at low frequencies. For the considered case of a shoulder bed dipping at 80°, ambiguity in the flexural cutoff frequency might lead to shear-wave velocity errors of 8%–10%.

Acoustic wave propagation in a fluid‐filled borehole surrounded by a formation with stress‐relief‐induced anisotropy

Geophysics ◽  
1993 ◽  
Vol 58 (9) ◽  
pp. 1257-1269 ◽  
Author(s):  
Lasse Renlie ◽  
Arne M. Raaen
Keyword(s):  
Wave Propagation ◽  
Acoustic Wave ◽  
Shear Wave ◽  
Transverse Isotropy ◽  
Shear Velocity ◽  
Stress Relief ◽  
Stoneley Wave ◽  
Acoustic Wave Propagation ◽  
Damaged Zone ◽  
Compressional Velocity

The stress relief associated with the drilling of a borehole may lead to an anisotropic formation in the vicinity of the borehole, where the properties in the radial direction differ from those in the axial and tangential directions. Thus, axial and radial compressional acoustic velocities are different, and similarly, the velocity of an axial shear‐wave depends on whether the polarization is radial or tangential. A model was developed to describe acoustic wave propagation in a borehole surrounded by a formation with stress‐relief‐induced radial transverse isotropy (RTI). Acoustic full waveforms due to a monopole source are computed using the real‐axis integration method, and dispersion relations are found by tracing poles in the [Formula: see text] plane. An analytic expression for the low‐frequency Stoneley wave is developed. The numerical results confirm the expectations that the compressional refraction is mainly given by the axial compressional velocity, while the shear refraction arrival is due to the shear wave with radial polarization. As a result, acoustic logging in an RTI formation, will indicate a higher [Formula: see text] ratio than that existing in the virgin formation. It also follows that the shear velocity may be a better indicator of a mechanically damaged zone near the borehole than the compressional velocity. The Stoneley‐wave velocity was found to decrease with the increasing degree of RTI.

scholarly journals Permeability Determination from Stoneley Waves in the Ara Group Carbonates, Oman

GeoArabia ◽  
2001 ◽  
Vol 6 (4) ◽  
pp. 649-666
Author(s):  
Latifa Qobi ◽  
André de Kuijper ◽  
Xiao Ming Tang ◽  
Jonathan Strauss
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Stoneley Wave ◽  
Stoneley Waves ◽  
Wave Data ◽  
Pressure Tests ◽  
Routine Basis ◽  
Acoustic Device ◽  
Petroleum Development ◽  
Hydrocarbon Reserves

ABSTRACT Measurement of continuous permeability profiles on a routine basis has become possible through recent advances in wireline logging hardware and software. Continuous permeability profiles allow geologists and reservoir engineers to better characterize their reservoirs and to more efficiently complete and manage the production of the hydrocarbon reserves. One of the most promising methods for the calculation of continuous permeability information is the use of Stoneley wave data acquired using a monopole acoustic device. This paper presents the results of a case study conducted for Petroleum Development Oman. In this study, permeability was determined from Stoneley wave data from the Sarmad-1H2 and Sarmad-2H1 wells that penetrated the carbonate reservoirs of the Ara Group of Oman. The Stoneley-wave derived profile was compared with permeability data from other sources; such as, cores, wireline pressure tests, and the interpretation of nuclear magnetic resonance measurements. The results demonstrated the validity of the methodology and showed that Stoneley-wave data can be used on a routine basis to obtain a continuous permeability indication for completion evaluation purposes. The method has great potential in permeability prediction.

Joint inversion of logging-while-drilling multipole acoustic data to determine formation shear-wave transverse isotropy

Geophysics ◽  
2020 ◽  
Vol 85 (4) ◽  
pp. D121-D132
Author(s):  
Yang-Hu Li ◽  
Song Xu ◽  
Can Jiang ◽  
Yuan-Da Su ◽  
Xiao-Ming Tang
Keyword(s):  
Shear Wave ◽  
Joint Inversion ◽  
Transverse Isotropy ◽  
Synthetic Data ◽  
Flexural Wave ◽  
Inversion Method ◽  
S Wave ◽  
Acoustic Data ◽  
Wave Data ◽  
Logging While Drilling

Seismic-wave anisotropy has long been an important topic in the exploration and development of unconventional reservoirs, especially in shales, which are commonly characterized as transversely isotropic ([TI] or vertical TI [VTI]) media. At present, the shear-wave (S-wave) TI properties have mainly been determined from monopole Stoneley- or dipole flexural-wave measurements in wireline acoustic logging, but the feasibility of those obtained from logging-while-drilling (LWD) acoustic data needs to be established. We have developed a joint inversion method for simultaneously determining formation S-wave transverse isotropy and vertical velocity from LWD multipole acoustic data. Our theoretical analysis shows that the presence of anisotropy strongly influences LWD Stoneley- and quadrupole-wave dispersion characteristics. Although the monopole Stoneley and quadrupole waves are sensitive to the formation S-wave TI parameters, they suffer from the typical nonuniqueness problem when using the individual-wave data to invert parameters alone. Thus, the respective dispersion data can be jointly used to estimate the formation S-wave TI properties. By the joint inversion, the nonuniqueness problem in the parameter inversion can also be effectively alleviated. The feasibility of the method has been verified by the processing results of theoretical synthetic data and field LWD acoustic-wave data. Therefore, the result offers an effective method for evaluating VTI formation anisotropy from acoustic LWD data.

The Effect of Pitch Gyradius on Added Resistance of Yacht Hulls

1991 ◽  
Author(s):  
James F. Moran
Keyword(s):  
Water Resistance ◽  
Wave Spectrum ◽  
Response Amplitude ◽  
Added Resistance ◽  
Regular Waves ◽  
Low Frequencies ◽  
Irregular Wave ◽  
Wave Data ◽  
The Difference ◽  
Response Amplitude Operators

The purpose of this investigation was to determine the effect of pitch gyradius on added resistance of yacht hulls. Tank testing of a model yacht in head seas was performed in the Webb Robinson Model Basin. The model was tested in regular waves at two speeds and five variations of gyradius. The model was also evaluated in irregular seas of the Pierson-Moskowitz spectrum at various speeds with two gyradii. Response Amplitude Operators were developed from the regular wave data and comparisons made. The irregular wave data were analyzed for the effect of speed on the difference in added resistance between the maximum and minimum gyradius settings. Several conclusions were arrived at after analyzing the data. The Response Amplitude Operaters shift as the gyradius changes. In regular waves, at low frequencies of encounter, a lower, gyradius resulted in less added frequencies of encounter in regular waves, this trend reverses itself and the higher gyradii result in reduced added resistance. However, at higher frequencies of encounter in regular waves, this trend reverses, reverses itself in reduced added resistance. The peaks of the RAO curves shift to higher frequencies at higher gyradii. It was also concluded that at the higher speed, Froude Number of 0.3, the added resistance was lower relative to the still-water resistance for each gyradius tested. The irregular wave testing revealed the effect of the lower frequencies dominating the irregular wave spectrum. The minimum gyradius, in irregular seas showed less added resistance than the maximum gyradius. In addition, the irregular wave testing verified, the reduction of added resistance, relative to still-water resistance, at increasing speeds for both the minimum and maximum gyradii.

Direct shear-wave seismic survey in Sanhu area, Qaidam Basin, west China

2022 ◽  
Vol 41 (1) ◽  
pp. 47-53
Author(s):  
Zhiwen Deng ◽  
Rui Zhang ◽  
Liang Gou ◽  
Shaohua Zhang ◽  
Yuanyuan Yue ◽  
...  
Keyword(s):  
Shear Wave ◽  
Reservoir Characterization ◽  
Qaidam Basin ◽  
P Wave ◽  
Data Sets ◽  
Direct Shear ◽  
Subsurface Structure ◽  
S Wave ◽  
West China ◽  
Wave Data

The formation containing shallow gas clouds poses a major challenge for conventional P-wave seismic surveys in the Sanhu area, Qaidam Basin, west China, as it dramatically attenuates seismic P-waves, resulting in high uncertainty in the subsurface structure and complexity in reservoir characterization. To address this issue, we proposed a workflow of direct shear-wave seismic (S-S) surveys. This is because the shear wave is not significantly affected by the pore fluid. Our workflow includes acquisition, processing, and interpretation in calibration with conventional P-wave seismic data to obtain improved subsurface structure images and reservoir characterization. To procure a good S-wave seismic image, several key techniques were applied: (1) a newly developed S-wave vibrator, one of the most powerful such vibrators in the world, was used to send a strong S-wave into the subsurface; (2) the acquired 9C S-S data sets initially were rotated into SH-SH and SV-SV components and subsequently were rotated into fast and slow S-wave components; and (3) a surface-wave inversion technique was applied to obtain the near-surface shear-wave velocity, used for static correction. As expected, the S-wave data were not affected by the gas clouds. This allowed us to map the subsurface structures with stronger confidence than with the P-wave data. Such S-wave data materialize into similar frequency spectra as P-wave data with a better signal-to-noise ratio. Seismic attributes were also applied to the S-wave data sets. This resulted in clearly visible geologic features that were invisible in the P-wave data.

scholarly journals Rancang Bangun Sistem Informasi Administrasi Vaksinasi Meningitis Berbasis Web di Kantor Kesehatan Pelabuhan Kelas III Banda Aceh

2017 ◽  
Vol 5 (2) ◽  
pp. 131-137
Author(s):  
Dedi Apriyandi ◽  
Kusworo Adi ◽  
Aris Puji Widodo
Keyword(s):  
Information System ◽  
Descriptive Analysis ◽  
Weighted Average ◽  
Test System ◽  
Fast Method ◽  
Class Iii ◽  
Research Subjects ◽  
Number Of Patients ◽  
Banda Aceh ◽  
Port Health

Meningitis vaccination service in Polyclinic of Class III Port Health Office (KKP) of Banda Aceh almost annually has increased the number of patients. There are several problems in the administration information system of meningitis vaccination that is currently running which officer is taking a long time to monitor the stock of vaccine and searching patient’s data that has been vaccinated. In the other hand, the data and information produced has yet incomplete, inaccurate and inconforn according within user system problems, Inaccurate timing for reporting and resulted to the inforrmation’s inconsistency. The purpose of this research is to produce an web-based information system of vaccine administration of meningitis at Polyclinic Class III Port Health Office of Banda Aceh.     The type of researchs used are qualitative and quantitative. This research design using one group pre and post test, system development using FAST method (Framework for the Application of System Techniques). Research subjects consisted of 8 respondents who work in Polyclinic Port Health Office Banda Aceh. The result of observation and interview is conducted by the method of content analysis and descriptive analysis by using the weighted average. Descriptively, the results of data analysis shows which overall weighted average value of quality information before the development of 1.91 system and after the development of 3.64 system with a difference of 1.73. The average calculation of time required to perform services to patients to be faster 4.9 minutes.     There is need support and commitment from the Class III Port Health Office Banda Aceh for implementing the administration information system of meningitis vaccination that has been developed optimally. Monitoring and evaluating users of the system should be performed periodically by Port Helath Office of Banda Aceh.

More reliable shear-wave data from VSPs using the CIPHER technique

First Break ◽  
1994 ◽  
Vol 12 (3) ◽  
Author(s):  
T. Gut ◽  
W. Söllner ◽  
E. Lüschen ◽  
H.A.K. Edelman
Keyword(s):  
Shear Wave ◽  
Wave Data
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