Acoustic radiation and reflection of a logging-while-drilling dipole source

2019 ◽  
Vol 219 (1) ◽  
pp. 108-128 ◽  
Author(s):  
Zhoutuo Wei ◽  
Xiaoming Tang ◽  
Jingji Cao
Keyword(s):  
Frequency Band ◽  
Wave Reflection ◽  
Excitation Frequency ◽  
Radiation Efficiency ◽  
Wave Radiation ◽  
Dipole Source ◽  
Sh Wave ◽  
S Wave ◽  
Single Well ◽  
Logging While Drilling

SUMMARY With the comparison to the resistivity ultra-deep measurement, the single-well reflection survey in acoustic logging-while-drilling (ALWD) measurement lags far behind, especially ALWD dipole measurement has long been thought to be little added value. In this paper, we extended the dipole shear-wave (S-wave) reflection survey technology in wireline logging into ALWD and demonstrated the theoretical feasibility of adopting a dipole source–receiver system to perform ALWD reflection survey. For this purpose, we investigated the radiation patterns of radiantSH, SV and P waves, the energy fluxes of guided and radiant waves and their acoustical radiation efficiencies from an LWD dipole acoustic source by comparisons with the wireline results. The analysis results reveal that a dominant excitation-frequency band does exist in ALWD dipole S-wave reflection. Consequently, the expected excitation frequency should be located in the band of the signal with high radiation efficiency, guaranteeing the best radiation performance. In fast formations, SH wave is the best candidate for ALWD reflection survey due to its highest radiation efficiency. In contrast, the dominant excitation-frequency band of SH wave gets wider in a slow formation. Besides, the SV- and P-wave radiation efficiencies are also remarkable, implying that both waves can also be used for ALWD reflection survey in slow formations. We expounded the SH-, SV- and P-reflection behaviours at three typical excitation frequencies by our 3-D finite difference. Simulations to single-well reflection validate the key role of dominant excitation-frequency band and demonstrate the theoretical feasibility of applying the technology to ALWD. Our results can guide the design and measurement methods of ALWD dipole S-wave reflection survey tool, which could have extensive application prospect for geo-steering.

Single-well S-wave imaging using multicomponent dipole acoustic-log data

Geophysics ◽  
2009 ◽  
Vol 74 (6) ◽  
pp. WCA211-WCA223 ◽  
Author(s):  
Xiao-Ming Tang ◽  
Douglas J. Patterson
Keyword(s):  
Field Data ◽  
Wave Radiation ◽  
Dipole Source ◽  
Directional Sensitivity ◽  
S Wave ◽  
Fracture Characterization ◽  
Processing Application ◽  
S Waves ◽  
Wave Imaging ◽  
Single Well

Single-well S-wave imaging has several attractive features because of its directional sensitivity and usefulness for fracture characterization. To provide a method for single-well acoustic imaging, we analyzed the effects of wave radiation, reflection, and borehole acoustic response on S-wave reflection measurements from a multicomponent dipole acoustic tool. A study of S-wave radiation from a dipole source and the wave’s reflection from a formation boundary shows that the S-waves generated by a dipole source in a borehole have a wide radiation pattern that allows imaging of reflectors at various dip angles crossing the borehole. More importantly, the azimuthal variation of the S-waves, in connection with the multicomponent nature of a cross-dipole tool, can determine the strike of the reflector. We used our theoretical foundation for borehole S-wave imaging to formulate an inversion procedure for field data processing. Application to field data validates the theoretical results and demonstrates the advantages of S-wave imaging. Application to near-borehole fracture imaging clearly demonstrates S-wave azimuthal sensitivity to fracture orientation.

scholarly journals Responses of dipole-source reflected shear waves in acoustically slow formations

2019 ◽  
Author(s):  
Hao Wang ◽  
Ning Li ◽  
Caizhi Wang ◽  
Hongliang Wu ◽  
Peng Liu ◽  
...  
Keyword(s):  
Finite Difference Time Domain ◽  
Dipole Source ◽  
Sh Wave ◽  
S Wave ◽  
High Fracture ◽  
S Waves ◽  
Angle Fracture ◽  
Dip Angle ◽  
Difference Time

Abstract In the process of dipole-source acoustic far-detection logging, the azimuth of the fracture outside the borehole can be determined with the assumption that the SH–SH wave is stronger than the SV–SV wave. However, in slow formations, the considerable borehole modulation highly complicates the dipole-source radiation of SH and SV waves. A 3D finite-difference time-domain method is used to investigate the responses of the dipole-source reflected shear wave (S–S) in slow formations and explain the relationships between the azimuth characteristics of the S–S wave and the source–receiver offset and the dip angle of the fracture outside the borehole. Results indicate that the SH–SH and SV–SV waves cannot be effectively distinguished by amplitude at some offset ranges under low- and high-fracture dip angle conditions, and the offset ranges are related to formation properties and fracture dip angle. In these cases, the fracture azimuth determined by the amplitude of the S–S wave not only has a $180^\circ $ uncertainty but may also have a $90^\circ $ difference from the actual value. Under these situations, the P–P, S–P and S–S waves can be combined to solve the problem of the $90^\circ $ difference in the azimuth determination of fractures outside the borehole, especially for a low-dip-angle fracture.

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.

Characterizing the borehole response for single-well shear-wave reflection imaging

Geophysics ◽  
2020 ◽  
pp. 1-42
Author(s):  
Yang-Hu Li ◽  
Xiao-Ming Tang ◽  
Huan-Ran Li ◽  
Sheng-Qing Lee
Keyword(s):  
Shear Wave ◽  
Wave Reflection ◽  
Spherical Wave ◽  
Dipole Source ◽  
Virtual Source ◽  
Shear Wave Imaging ◽  
Receiver System ◽  
Wave Imaging ◽  
Single Well ◽  
Reflection Imaging

Single-well shear-wave imaging using a dipole source-receiver system is an important application for detecting geological structures away from the borehole. This development allows for determining the azimuth information of the structures. Existing analyses, however, focus on the data received at the borehole axis and use the elastic reciprocity theorem to model the borehole radiation and recording. We extend the existing analyses to model the radiation, reflection, and the recording response of the borehole for azimuthally spaced receivers off the borehole axis. By treating the mirror image of the borehole source with respect to the reflector plane as a virtual source, the borehole reception problem is shown to be equivalent to the response of the borehole to the spherical wave incidence from the virtual source, which can be solved using the cylindrical-wave expansion method. An asymptotic solution using the steepest decent method is obtained if the virtual source is far from the borehole. The analytical solution allows us to analyze the borehole response for azimuthally spaced off-axis receivers. The analysis results agree well with those from 3D finite-difference simulations. With this analysis, one can further model the multi-component shear-wave reflection data from the cross-dipole acoustic tool and study the azimuthal variation characteristics of the data. The results show that, while the data characteristics are dominated by those of a dipole, non-dipole responses due to the off-axis reception can be observed, the magnitude of the responses depending on the off-axis distance and frequency and on the formation elasticity. The non-dipole response characteristics have the potential to resolve the 180°-ambiguity problem in the azimuth determination for the dipole shear-wave imaging. The findings, therefore, provide new information to the shear-wave reflection imaging analysis and development.

Modeling wave generation by borehole orbital vibrator source

Geophysics ◽  
2006 ◽  
Vol 71 (1) ◽  
pp. F1-F11
Author(s):  
Seiji Nakagawa ◽  
Thomas M. Daley
Keyword(s):  
Shear Wave ◽  
3D Models ◽  
Wave Generation ◽  
Guided Wave ◽  
Wave Radiation ◽  
S Wave ◽  
Wave Source ◽  
Partial Wave Expansion ◽  
Single Well ◽  
Tube Wave

An orbital vibrator source (OVS), a fluid-coupled shear-wave source, has many properties useful for crosswell, single-well, and borehole-to-surface imaging of both P- (compressional) and S- (shear) wave velocities of reservoir rocks. To this day, however, only a limited number of quantitative models have been developed to explain its properties. In this article, we develop both 2D and 3D models of an OVS, allowing us to examine source characteristics such as radiation patterns, frequency dependence of wave amplitudes, and guided-wave generation. These models are developed in the frequency-wavenumber domain using the partial wave expansion of the wavefield within and outside the borehole. The models predict many unique characteristics of an OVS, including formation-property-dependent vibrator amplitudes, uniform isotropic S-wave radiation pattern, and small tube-wave generation.

Shear-wave radiation, reception, and reciprocity of a borehole dipole source: With application to modeling of shear-wave reflection survey

Geophysics ◽  
2014 ◽  
Vol 79 (2) ◽  
pp. T43-T50 ◽  
Author(s):  
Xiao-Ming Tang ◽  
Jing-ji Cao ◽  
Zhou-tuo Wei
Keyword(s):  
Asymptotic Solution ◽  
Shear Wave ◽  
Wave Reflection ◽  
Wave Radiation ◽  
Dipole Source ◽  
Wave Component ◽  
Shear Wave Imaging ◽  
Reflection Data ◽  
Wave Imaging ◽  
Effects Of Radiation

The development of dipole shear-wave imaging technology requires understanding of the effects of radiation, reflection, and reception of elastic waves from a borehole dipole source, for which we provide a comprehensive analysis. We first show that the radiation of the dipole source can be accurately computed using its far-field asymptotic solution when the radiation distance is greater than wavelength. We then demonstrate the reciprocity relationship between shear-wave radiation and reception of the dipole source. Consequently, the borehole radiation pattern can be used to compute the borehole reception directivity. The use of the reciprocity relationship and the asymptotic solution greatly facilitates the modeling of the wavefield for the borehole shear-wave reflection survey. The modeling results agree well with those from a 3D finite-difference elastic wave simulation. The modeling of SH- and SV-wave radiation/reception of the dipole source also demonstrates that the SH-wave component is far greater than the SV-wave component, providing an important foundation for shear-wave reflection data processing and interpretation.

scholarly journals Design of a New Acoustic Logging While Drilling Tool

Sensors ◽  
2021 ◽  
Vol 21 (13) ◽  
pp. 4385
Author(s):  
Kai Zhang ◽  
Baohai Tan ◽  
Wenxiu Zhang ◽  
Yuntao Sun ◽  
Jian Zheng ◽  
...  
Keyword(s):  
Impedance Matching ◽  
Sine Wave ◽  
Azimuthal Anisotropy ◽  
Dipole Source ◽  
Pulse Excitation ◽  
Drilling Tool ◽  
Overall Design ◽  
Logging While Drilling ◽  
Physical Construction ◽  
Exciting Wave

To obtain qualified logging while drilling (LWD) data, a new acoustic LWD tool was designed. Its overall design is introduced here, including the physical construction, electronic structure, and operation flowchart. Thereafter, core technologies adopted in this tool are presented, such as dominant exciting wave bands of dipole source, a sine wave pulse excitation circuit, broadband impedance matching, and an intellectualized active reception transducer. Lastly, we tested this tool in the azimuthal anisotropy module well, calibration well, and normal well, working in the model of the cable, sliding eye, and logging while drilling. Experiments showed that the core technologies achieved ideal results and that the LWD tool obtained qualified data.

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