Acoustic Logging While Drilling (LWD): Experimental Studies with Anisotropic Models
Author(s)
Rao, Rama V. N.
Zhu, Zheny
Burns, Daniel R.
Toksoz, M. Nafi
Date Issued
2002
Publisher
Massachusetts Institute of Technology. Earth Resources Laboratory
Series/Report no.
Earth Resources Laboratory Industry Consortia Annual Report;2002-02
Abstract
A model LWD tool (0.16" ID, 0.4" OD) was built to investigate its operation in
an anisotropic formation. The tool consists of a dipole source and six dipole receivers
capable of operating at several hundred kHz. The formation was a block of delabole
slate with a borehole of 1.27 cm diameter.
In an anisotropic °uid-¯lled borehole with a dipole source and dipole receiver ori-
ented along the principal directions, dipole (°exural) modes are mainly observed. Weak
compression and shear refracted arrivals are also discernable when they were not ob-
scured by stronger arrivals. Further, modes corresponding to fast shear direction are
evident in the slow shear direction measurement.
With a model LWD tool in the °uid-¯lled borehole, and oriented in the fast and
slow directions, the main arrivals were the corresponding °exural modes. Modes cor-
responding to the fast shear direction are no longer evident in the slow shear direction
measurments. These preliminary experiments suggest that, with an LWD tool in an
anisotropic formation, arrivals sensitive to formation properties can be discerned.
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