Standard Oil Company (indiana)

John B Farr

Pierre A Beynet

Newell Pottorf

A downhole seismic source for use when drilling a borehole in the earth using a rotating drill string through which a drilling fluid is circulated. In one embodiment, a section of the drill string has a slot in it and a sleeve rotatably surrounding the slot with a plurality of spaced-apart slots arranged to align with the slot in section of drill pipe during rotation of the sleeve with respect to the section. In operation this generates a controlled seismic signal. In another embodiment the bit is modified to have a fluid passage with a valve therein that opens and closes in a selected pattern during rotation of the drill bit.

Downhole seismic source

Disclosed is a seismic source forming part of a drill string which allows geological prospecting while drilling a borehole. The source includes a section of drill pipe having a spiral cam machined into its outer surface and a port for allowing mud to flow from the inside of the drill pipe into the borehole. A sleeve surrounds this section of the drill pipe and includes a cam follower, a plurality of ports, and a spring borehole contact for preventing rotation of the sleeve. The sleeve blocks flow of mud through the drill pipe port, except when a sleeve port is in alignment therewith. When the sleeve cam follower is engaged in the drill pipe cam and the drill pipe is rotated, the drill pipe port follows a helical path relative to the sleeve and sequentially passes all the ports in the sleeve. Signal wave shape is determined by the configuration of the sleeve ports and frequency is determined by the drill pipe rotation rate.

A continuous line hydrophone comprising a plurality of coaxial cable segments coupled by electronic circuit modules wherein the coaxial cable serves the functions of seismic detector, signal transmission line, and DC power supply line. In the preferred embodiment, the coaxial cable is sensitized to seismic energy by having the inter-electrode dielectric permanently polarized so that it becomes an electret. An electronic circuit module at the end of a coaxial cable segment responds to seismic frequency signals produced in the coaxial cable by acoustic waves to generate a frequency-modulated carrier wave which is coupled to the next coaxial cable segment for transmission toward a tape recorder. The electronic module also retransmits any carrier wave signals which it receives from cables from distant from the recorder. The electronic circuit means additionally allows DC power to be coupled from the recorder end of the cable to more distant electronic circuits.

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Houston, TX, United States of America

John B Farr