Investigation of borehole cross-dipole flexural dispersion crossover through numerical modeling
Crossover of the dispersion of flexural waves recorded in borehole cross-dipole measurements is interpreted as an indicator of stress-induced anisotropy around a circular borehole in formations that are isotropic in the absence of stresses. We have investigated different factors that influence flexu...
| Main Authors: | , , |
|---|---|
| Other Authors: | |
| Format: | Article |
| Language: | en_US |
| Published: |
Society of Exploration Geophysicists
2015
|
| Online Access: | http://hdl.handle.net/1721.1/99710 https://orcid.org/0000-0002-8814-5495 |
| _version_ | 1826192133841747968 |
|---|---|
| author | Fang, Xinding Cheng, Arthur Fehler, Michael |
| author2 | Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences |
| author_facet | Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences Fang, Xinding Cheng, Arthur Fehler, Michael |
| author_sort | Fang, Xinding |
| collection | MIT |
| description | Crossover of the dispersion of flexural waves recorded in borehole cross-dipole measurements is interpreted as an indicator of stress-induced anisotropy around a circular borehole in formations that are isotropic in the absence of stresses. We have investigated different factors that influence flexural wave dispersion. Through numerical modeling, we determined that for a circular borehole surrounded by an isotropic formation that is subjected to an anisotropic stress field, the dipole flexural dispersion crossover is detectable only when the formation is very compliant. This might happen only in the shallow subsurface or in zones having high pore pressure. However, we found that dipole dispersion crossover can also result from the combined effect of formation intrinsic anisotropy and borehole elongation. We found that a small elongation on the wellbore and very weak intrinsic anisotropy can result in a resolvable crossover in flexural dispersion that might be erroneously interpreted as borehole stress-induced anisotropy. A thorough and correct interpretation of flexural dispersion crossover thus has to take into account the effects of stress-induced and intrinsic anisotropy and borehole cross-sectional geometry. |
| first_indexed | 2024-09-23T09:06:46Z |
| format | Article |
| id | mit-1721.1/99710 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T09:06:46Z |
| publishDate | 2015 |
| publisher | Society of Exploration Geophysicists |
| record_format | dspace |
| spelling | mit-1721.1/997102022-09-26T10:31:28Z Investigation of borehole cross-dipole flexural dispersion crossover through numerical modeling Fang, Xinding Cheng, Arthur Fehler, Michael Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences Fang, Xinding Fehler, Michael Crossover of the dispersion of flexural waves recorded in borehole cross-dipole measurements is interpreted as an indicator of stress-induced anisotropy around a circular borehole in formations that are isotropic in the absence of stresses. We have investigated different factors that influence flexural wave dispersion. Through numerical modeling, we determined that for a circular borehole surrounded by an isotropic formation that is subjected to an anisotropic stress field, the dipole flexural dispersion crossover is detectable only when the formation is very compliant. This might happen only in the shallow subsurface or in zones having high pore pressure. However, we found that dipole dispersion crossover can also result from the combined effect of formation intrinsic anisotropy and borehole elongation. We found that a small elongation on the wellbore and very weak intrinsic anisotropy can result in a resolvable crossover in flexural dispersion that might be erroneously interpreted as borehole stress-induced anisotropy. A thorough and correct interpretation of flexural dispersion crossover thus has to take into account the effects of stress-induced and intrinsic anisotropy and borehole cross-sectional geometry. 2015-11-04T16:31:33Z 2015-11-04T16:31:33Z 2014-12 2014-09 Article http://purl.org/eprint/type/JournalArticle 0016-8033 1942-2156 http://hdl.handle.net/1721.1/99710 Fang, Xinding, Arthur Cheng, and Michael C. Fehler. “Investigation of Borehole Cross-Dipole Flexural Dispersion Crossover through Numerical Modeling.” Geophysics 80, no. 1 (December 22, 2014): D75–D88. © 2014 Society of Exploration Geophysicists https://orcid.org/0000-0002-8814-5495 en_US http://dx.doi.org/10.1190/GEO2014-0196.1 Geophysics Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf Society of Exploration Geophysicists Society of Exploration Geophysicists |
| spellingShingle | Fang, Xinding Cheng, Arthur Fehler, Michael Investigation of borehole cross-dipole flexural dispersion crossover through numerical modeling |
| title | Investigation of borehole cross-dipole flexural dispersion crossover through numerical modeling |
| title_full | Investigation of borehole cross-dipole flexural dispersion crossover through numerical modeling |
| title_fullStr | Investigation of borehole cross-dipole flexural dispersion crossover through numerical modeling |
| title_full_unstemmed | Investigation of borehole cross-dipole flexural dispersion crossover through numerical modeling |
| title_short | Investigation of borehole cross-dipole flexural dispersion crossover through numerical modeling |
| title_sort | investigation of borehole cross dipole flexural dispersion crossover through numerical modeling |
| url | http://hdl.handle.net/1721.1/99710 https://orcid.org/0000-0002-8814-5495 |
| work_keys_str_mv | AT fangxinding investigationofboreholecrossdipoleflexuraldispersioncrossoverthroughnumericalmodeling AT chengarthur investigationofboreholecrossdipoleflexuraldispersioncrossoverthroughnumericalmodeling AT fehlermichael investigationofboreholecrossdipoleflexuraldispersioncrossoverthroughnumericalmodeling |