Apparatus and method for electromagnetically detecting the passing of a plug released into a well by a bridge circuit
First Claim
1. An apparatus for detecting the passing of a plug released into a well, comprising:
- an electrical bridge circuit including a first electrical coil and a second electrical coil spaced at fixed locations along a course through which the plug passes in a single direction from an initial position above both said coils; and
at least one metallic member mounted on the plug so that said at least one metallic member passes in effective proximity to both said first and second electrical coils as the plug passes both said first and second electrical coils in said single direction, wherein said at least one metallic member changes an electrical response of said electrical bridge circuit to an electrical response identifiable with said at least one metallic member when the plug passes both said first and second coils.
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Accused Products
Abstract
A plug released into an oil or gas well carries one or more metallic strips that affect the inductance of a resistive-inductive bridge circuit mounted adjacent a conduit through which the plug and fluids are pumped into the well. This unbalances the bridge circuit to produce a signal preferably uniquely identified with the plug so that an indicator can be activated to confirm proper release of the plug into the well. When an amorphous metal is used in the metallic strips, the unbalancing of the bridge produces a signal having an identifiable harmonic of a fundamental frequency of an oscillator signal driving the bridge circuit, which harmonic is not present in other signals resulting from the bridge circuit being unbalanced by other materials flowing in the conduit.
45 Citations
32 Claims
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1. An apparatus for detecting the passing of a plug released into a well, comprising:
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an electrical bridge circuit including a first electrical coil and a second electrical coil spaced at fixed locations along a course through which the plug passes in a single direction from an initial position above both said coils; and at least one metallic member mounted on the plug so that said at least one metallic member passes in effective proximity to both said first and second electrical coils as the plug passes both said first and second electrical coils in said single direction, wherein said at least one metallic member changes an electrical response of said electrical bridge circuit to an electrical response identifiable with said at least one metallic member when the plug passes both said first and second coils. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. An apparatus for detecting the passing of a cementing plug pumped into a well with a column of cement containing different metals, comprising:
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a bridge circuit, including; two electrical coils disposed outside a path through which the plug and cement are pumped in a single direction into the well, said two coils spaced longitudinally from each other relative to said single direction but connected in electrical series with each other; and two series connected electrical resistances connected in electrical parallel with said two electrical coils; an oscillator circuit connected across said bridge circuit in electrical parallel with said parallel connected electrical coils and resistances, said oscillator circuit including means for providing an electrical input signal, having a fundamental frequency, to said bridge circuit so that no signal is output from said bridge circuit from between said series connected electrical coils to between said series connected resistances when said bridge circuit is in electrical balance with the plug disposed longitudinally above both said coils relative to said single direction and so that a signal is output from said bridge circuit from between said series connected electrical coils to between said series connected resistances when said bridge circuit is not in electrical balance in response to metal passing said coils and thereby changing the conductivity of said bridge circuit; an amorphous metallic alloy disposed on the plug for changing the impedance of said bridge circuit so that an output signal is provided from said bridge circuit when the plug passes both said coils in said single direction and additionally for effecting in said output signal a frequency which is a harmonic of the fundamental frequency of said input signal; and means, connected to said bridge circuit, for sensing the harmonic frequency and for indicating in response thereto that the plug has passed both said electrical coils in said single direction. - View Dependent Claims (20, 21, 22, 23, 24, 25)
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26. A method of detecting a plug passing a predetermined location along a flow path of a well, comprising:
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generating at the well an electrical signal having a fundamental frequency; driving an electrical bridge circuit, connected adjacent the flow path, with the electrical signal; pumping a fluid against the plug so that the fluid and the plug move in a single direction through the flow path past the bridge circuit; generating an output signal from the bridge circuit in response to metal in the fluid or the plug moving sequentially past two coils of the bridge circuit, including producing in the output signal from the bridge circuit a harmonic of the fundamental frequency in response only to the plug passing the two coils of the bridge circuit; and sensing the harmonic in the output signal. - View Dependent Claims (27, 28, 29, 30, 31)
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32. In a system wherein a plug container is connected to an oil or gas well so that a metal-containing fluid pumped into the plug container against a plug contained in the plug container moves the plug downwardly towards the well when the plug is released from the plug container, an apparatus for detecting that the plug has successfully released from the plug container, comprising:
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an adapter coupling member connected below the plug container and above the well for defining at least part of a flow path through which the metal-containing fluid and the plug are to move into the well; a distinctive metal, different from metal in the metal-containing fluid, mounted in the plug; and an electrical bridge circuit including a first electrical coil and a second electrical coil retained at respective fixed locations along said adapter coupling member, each of said coils encircling said flow path but disposed outside said flow path so that the fluid and a successfully released plug move through both said coils as the fluid and successfully released plug move from the plug container into the well, said electrical bridge circuit providing a first electrical response to metal in the fluid moving past said first and second coils and said electrical bridge circuit providing a second electrical response to said distinctive metal in the plug moving past both said first and second coils, said second electrical response adapted for indicating that the plug has successfully released from the plug container.
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Specification