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Influence of drill collar eccentricity on quadrupole shear-wave logging while drilling : theory and field case
Rao Bo1; Su YuanDa1,2; Li ShengQing1; Sun YunTao3; Chen WenXuan3; Tang XiaoMing1,2
AbstractThe shear-wave velocity of formation is measured by using a acoustic logging-while-drilling (ALWD) quadrupole tool, while the eccentricity of drill collar will seriously influence the quality of the quadrupole waveforms and the shear-velocity measurement during the complicated rotary drilling process. In this study, an eccentric ALWD model is established in the dual cylindrical coordinate systems based on locations of the drill collar and borehole. The translational addition theorem of Bessel functions is utilized to construct the boundary conditions and borehole response functions. Then the wave-field excited by quadrupole sources under the conditions of the centered and eccentric drill collar models is numerically simulated. The results show that an eccentric tool causes multipole wave modes including the formation quadrupole mode, and the Stoneley-wave and the flexural wave coexist and couple with each other. It should be noted that when the drill collar is seriously eccentric in the slow formation, the quadrupole mode is seriously disturbed by Stoneley-wave and the flexural wave modes, which is not conducive for the shear velocity measurement. Field data analysis results show that high quality and pure quadrupole waveforms of the formation can be measured, and accurate shear-wave slowness can be obtained, which is in good agreement with the shear-wave velocity of ALWD monopole mode. However, the waveform has complex components when the ALWD tool is eccentric. The coupling interference of low-frequency Stoneley-wave causes poor correlation of formation quadrupole waveforms and unreliable shear-wave slowness. The measurement of slowness is between the actual shear-wave and Stoneley-wave, which is extremely different from the result of monopole measurement of the ALWD tool. This discrepancy become obvious in the slow formation. Therefore, based on the eccentric quadrupole ALWD theory and combined with the measured data, this study concentrates on the analysis of the influence of drill collar eccentricity on quadrupole-wave data, which provides a theoretical foundation for the processing and correction of quadrupole data of ALWD with an eccentric drill collar.
KeywordAcoustic logging while drilling Quadrupole Tool eccentricity Shear-wave velocity
WOS Research AreaGeochemistry & Geophysics
WOS SubjectGeochemistry & Geophysics
WOS IDWOS:000910572800009
Citation statistics
Document Type期刊论文
Corresponding AuthorSu YuanDa
Affiliation1.China Univ Petr, Key Lab Deep Oil & Gas, Qingdao 266580, Peoples R China
2.Laoshan Lab, Lab Marine Mineral Resources, Qingdao 266071, Peoples R China
3.Chinese Acad Sci, Inst Geol & Geophys, Beijing 100029, Peoples R China
Recommended Citation
GB/T 7714
Rao Bo,Su YuanDa,Li ShengQing,et al. Influence of drill collar eccentricity on quadrupole shear-wave logging while drilling : theory and field case[J]. CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION,2023,66(1):111-121.
APA Rao Bo,Su YuanDa,Li ShengQing,Sun YunTao,Chen WenXuan,&Tang XiaoMing.(2023).Influence of drill collar eccentricity on quadrupole shear-wave logging while drilling : theory and field case.CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION,66(1),111-121.
MLA Rao Bo,et al."Influence of drill collar eccentricity on quadrupole shear-wave logging while drilling : theory and field case".CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION 66.1(2023):111-121.
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