Schlumberger Technology Corporation

Jean-Pierre Masson

Kai Hsu

Shu-Kong Chang

Thomas J Plona

James C Mayes

Miguel F Pabon

Sergio Kostek

Curtis J Randall

Gordon Lane McDaniel

Claude Fierfort

Jacky Bourseul

An ultrasonic sensor assembly for measuring the diameter of a well while it is being drilled is provided. The sensor assembly includes a stack including an inner sound absorbing backing element, a piezoelectric ceramic disk transducer stacked outwardly adjacent the backing element, and a matching layer, preferable made of PEEK and disposed outwardly adjacent the transducer. The layers of the stack are provided within a cavity of a metal cup and are maintained in position by a flexible diaphragm preferably made of PEEK. The diaphragm is sealed with an O-ring. A window, also preferably made of PEEK, is provided against the diaphragm and is held against the diaphragm by a spring. This arrangement acoustically couples the diaphragm to the stack and improves signal recovery. The diaphragm and O-ring form a hydraulic seal between fluid/mud in the well and the stack, and operate to retain the layers of the stack. Also, the diaphragm deforms to permit the stack to move when transmitting or receiving, and maintains an acoustic coupling between the stack and the window.

Acoustic sensor assembly

The present invention is directed to sonic logging while drilling. A transmitter and at least one receiver are mounted on a drill collar for performing sonic investigations of the formation traversed by a borehole. It has been discovered that a drill collar has a natural stop band or notch where acoustic energy propagating in this frequency range is severely attenuated. Thus, to reduce drill collar acoustic coupling, the transmitter is operated within this natural stop band of the drill collar. An imperforate stop band filter is also included between the transmitter and receiver to enhance the natural stop band. The transmitter is mounted transverse to the longitudinal axis of the drill collar, and is preferably mounted within means that reduce drill collar acoustic coupling. The transmitter preferably includes a material whose acoustic response is more favorable along its longitudinal axis relative to its radial axis, thereby directing the acoustic energy into the formation rather than the surrounding drill collar. Received acoustic energy waveforms are electronically processed to reliably detect, in the presence of drilling noise, those acoustic signals which are produced by the transmitter and transmitted through the formation.

Method of sonic logging while drilling a borehole traversing an earth

A method of measuring acoustic vibrations affecting the fluid in a well at a plurality of points which are angularly distributed around the axis of the well and which are in the proximity of the wall of the well by means of an apparatus including an elongate body which is rotatable about its longitudinal axis and having at least one acoustic vibration detector disposed at the end of an arm which is hinged to the body. The arm is moved away from the body so as to place its end at a determined distance from the wall of the well, and the arm is then caused to rotate continuously about the axis while simultaneously recording the signals produced by the detector. The method is suitable for use in a relief well to locate a well which is blowing out.

Method and apparatus for detecting acoustic vibrations in a borehole

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Richmond, TX, United States of America

Jean-Pierre Masson