Vertical open fractures and shear-wave velocities derived from VSPs, full waveform acoustic logs, and televiewer data

Journal Article · Tue Jun 01 04:00:00 EDT 1993 · Geophysics; (United States)

DOI:https://doi.org/10.1190/1.1443467· OSTI ID:6102050

Lefeuvre, F; Turpening, R; Caravana, C; Born, A ^[1]; Nicoletis, L ^[2]

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1. Massachusetts Inst. of Tech., Cambridge, MA (United States). Earth Resources Lab.
2. Inst. Francais du Petrole, Malmaison (France)

Fracture or stress-related shear-wave birefringence (or azimuthal anisotropy) from vertical seismic profiles (VSPs) is commonly observed today, but no attempt is made to fit the observations with observed in-situ fractures and velocities. With data from a hard rock (limestones, dolomites, and anhydrites) region of Michigan, fast and slow shear-wave velocities have been derived from a nine-component zero offset VSP and compared to shear-wave velocities from two full waveform acoustic logs. To represent the shear-wave birefringence that affects the shear wave's vertical propagation, a propagator matrix technique is used allowing a local measurement independent of the overburden layers. The picked times obtained by using a correlation technique have been corrected in the birefringent regions before they compute the fast and slow velocities. Although there are some differences between the three velocity sets, there is a good fit between the velocities from the shear-wave VSP and those from the two logs. The authors suspect the formations showing birefringence to be vertically fractured. To support this, they examine the behavior of the Stoneley wave on the full waveform acoustic logs in the formations. In addition, they analyze the borehole televiewer data from a nearby well. There is a good fit between the fractures seen from the VSP data and those seen from the borehole.

• OSTI ID: 6102050
• Journal Information: Geophysics; (United States), Journal Name: Geophysics; (United States) Vol. 58:6; ISSN GPYSA7; ISSN 0016-8033
• Country of Publication: United States
• Language: English

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