MONOPOLE ACOUSTIC TRANSMITTER COMPRISING A PLURALITY OF PIEZOELECTRIC DISCS
First Claim
1. A LWD logging tool acoustic transmitter comprising:
- (a) at least one disc assembly comprising(i) a plurality of piezoelectric discs, and(ii) a clamping mechanism cooperating with a first end cap and a second end cap to exert a compressional force upon said disc assembly;
wherein(b) masses of said first end cap and said end cap are selected to obtain predetermined transmitter frequency response;
(c) said at least one disc assembly is disposed in a recess in an outer surface defining a wall of said logging tool; and
(d) said discs are polarized and configured physically and electrically to emit a pressure pulse from each said disc in a common direction upon application of a voltage to said at least one disc assembly.
9 Assignments
0 Petitions
Accused Products
Abstract
A monopole acoustic transmitter with at least one disc assembly with a plurality of piezoelectric discs configured to optimized acoustic pressure output within a desired frequency range while meeting physical restrictions of LWD and MWD logging systems. The transmitter is disposed in a recess or “slot” in the perimeter of a logging tool housing to reduce acoustic pressure waves transmitted directly along the tool housing and to optimize acoustic energy transmission into the borehole environs. In order to increase acoustic pressure output at a desired logging frequency range, the plurality of piezoelectric discs in each of at least one disc assembly are connected electrically in parallel and fired simultaneously. The polarity of the discs and the wiring arrangement are such that each disc expands or contracts in a common direction during simultaneous firing by an applied voltage. The desired output frequency is obtained by selectively polarizing and dimensioning the discs within the one or more disc assemblies. Each disc assembly is preferably disposed within an oil filled pressure housing that is pressure and temperature compensated. The axis of the at least one disc assembly can be parallel or perpendicular to the major axis of the logging tool.
31 Citations
22 Claims
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1. A LWD logging tool acoustic transmitter comprising:
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(a) at least one disc assembly comprising (i) a plurality of piezoelectric discs, and (ii) a clamping mechanism cooperating with a first end cap and a second end cap to exert a compressional force upon said disc assembly;
wherein(b) masses of said first end cap and said end cap are selected to obtain predetermined transmitter frequency response; (c) said at least one disc assembly is disposed in a recess in an outer surface defining a wall of said logging tool; and (d) said discs are polarized and configured physically and electrically to emit a pressure pulse from each said disc in a common direction upon application of a voltage to said at least one disc assembly. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method emitting a pressure pulses into a borehole from a LWD logging tool, the method comprising:
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(a) disposing within said borehole a logging tool comprising a least one disc assembly comprising (i) a plurality of piezoelectric discs, and (ii) a clamping mechanism cooperating with a first end cap and a second end cap to exert a compressional force upon said disc assembly; (b) selecting masses of said first end cap and said second end caps to obtain a desired transmitter output frequency; (c) disposing said at least one disc assembly in a recess in an outer surface defining a wall of said logging tool; and (d) polarizing and configuring physically and electrically said discs to emit said pressure pulse from each said disc in each said at least one disc assembly in a common direction upon application of a voltage to said at least one disc assembly. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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Specification