Schlumberger Technology Corporation

Kenneth K Liang

Andrew J Hayman

Benoit G Froelich

Fred E Stanke

Philippe G Herve

Francedillaois M Auzerais

An acoustic logging tool emits a wideband acoustic pulse toward an inside surface of a borehole casing and an acoustic response is received. The acoustic response is analyzed at one or more higher order harmonics of the thickness mode resonance of the casing to determine the acoustic impedance of the material behind the casing.

Using higher order harmonics to determine acoustic impedance of material behind borehole casings

The present invention discloses an acoustic resonator device capable of nucleating bubbles in a formation fluid under borehole-like conditions wherein the static pressure is higher than the bubble point pressure. The device is comprised of one or more coaxial layers forming a central conduit, wherein at least one of the coaxial layers is comprised of an electro-acoustic transducer material such as including piezoelectric or magnetorestrictive materials. This device is preferably designed to be in fluid communication with a host tool to allow in-situ sampling and bubble point determination. Also disclosed is an in-situ method of fluid analysis in a borehole for determining phase characteristics of a formation fluid using the device. Cavitation may be induced using the device in either a captured volume sample or a flow-line sample.

Ultrasonic cylindrical resonator to facilitate bubble point pressure measurement

An improved technique for determining the thickness of a member, especially pipe such as fluid-filled casing in an earth borehole, includes the following steps: directing a pulse of ultrasonic energy toward the inner surface of the pipe, and receiving and storing, as a function of time, signals representative of ultrasonic energy reflected from the inner surface of the pipe; determining, from the stored signals, the arrival time of the initial echo from the inner surface; determining, from the stored signals, the arrival time and the amplitude of a first candidate initial echo from the outer surface of the pipe; performing a reverse search on the stored signals to determine, from stored signals at times earlier than the arrival time of the first candidate, the arrival time and the amplitude of a second candidate initial echo from the outer surface; comparing amplitudes of the first and second candidates, and selecting, based on the comparison, one of the first and second candidates as the actual outer surface echo; and determining the thickness of the pipe from the arrival time of the actual outer surface echo and the arrival time of the inner surface echo. Using this technique, the earlier arriving candidate can be properly identified as the actual outer surface echo, even when the later arriving candidate has a greater amplitude.

Method and apparatus for inspecting well bore casing

An improved technique for determining the thickness of a member, especially pipe such as fluid-filled casing in an earth borehole, includes the following steps: directing a pulse of ultra-sonic energy toward the inner surface of the pipe and receiving/storing, as a function of time, signals representative of ultra-sonic energy reflected from the inner surface of the pipe; determining, from the stored signals, the arrival or the initial echo from the inner surface; determining from the stored signals, the arrival and the amplitude of a first candidate initial echo from the outer surface of the pipe; performing a reverse search on the stored signals to determine, from stored signals at times earlier than the arrival time of the first candidate the arrival and the amplitude of a second candidate initial echo from the outer surface; comparing amplitudes of the first and second candidates and selecting, based on the comparison, one of the first and second candidates as the actual outer surface echo; and determining the thickness of the pipe from the arrival time of the actual outer surface echo and the arrival time of the inner surface echo. Using this technique, the earlier arriving candidate can be properly identified as the actual outer surface echo, even when the later arriving candidate has a greater amplitude.

A portion of a borehole wall is isolated from surrounding borehole fluids by placing a chamber of a borehole tool against the borehole wall. The chamber comprises a cylindrical recess in an exterior surface of the borehole tool. The recess is open at one end to receive borehole fluids, and closed at the opposite end by a concave ultrasonic acoustic transducer. Mudcake present within the chamber and on the isolated portion of the borehole wall is disintegrated by the concave ultrasonic transducer. This approach can be used to remove mudcake from a borehole wall with a moving or stationary borehole tool.

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Stow, MA, United States of America

Kenneth K Liang