High sensitivity well logging system having dual transmitter antennas and intermediate series resonant

Claim 1

Apparatus for use in a borehole to measure an electrical parameter of the formation surrounding the borehole, the apparatus comprising: housing means; first and second transmitting antenna means, each arranged around the housing means and spaced from each other; transmitter circuit means for alternately supplying an oscillating drive signal to the first and second transmitting antenna means, the oscillating electrical drive signal causing said first and second transmitting antenna means to radiate an electromagnetic wave signal that propagates through the formation; first and second series resonant receiving antenna means for producing first and second pick-up signals, each receiving antenna means having an impedance which includes a capacitive reactance component, an inductive reactance component, and a resistive component, wherein said capacitive reactance component and said inductive reactance component are substantially equal in magnitude and opposite in phase, each receiving antenna means being arranged around the housing means at a spaced position between the first and second transmitting antenna means and each including antenna circuit means in which an induced alternating current is produced while the electromagnetic wave signal propagates through the formation, the resonant frequency of the antenna circuit means being in a region embracing the frequency of the oscillating drive signal, and means responsive to the induced alternating current for producing a respective one of the pick-up signals; and sampled-data signal processing means responsive to the pick-up signals for producing a signal that is a function of the formation parameter.

Claim 20

A method for measuring an electrical parameter of the formation surrounding a borehole, which comprises: positioning in the borehole first and second series resonant single turn receiving antennae that are each tuned with a series connected capacitor to increase the sensitivity of the antenna at a predetermined frequency; generating an oscillating electrical drive signal at the predetermined frequency; alternately coupling the electrical drive signal to one and then another of a pair of transmitters to cause an electromagnetic wave signal to propagate through the formation in first one direction and then another so that the propagating electromagnetic wave signal induces the first and second receiving antenna to develop a first pair and then a second pair of pick-up signals; processing the first pair of pick-up signals to produce a first sampled signal, and recording the first sampled signal; processing the second pair of pick-up signals to produce a second sampled signal; and processing the recorded first sampled signal and the second sampled signal to produce a signal that is a function of the formation parameter.

Claim 21

A method for measuring an electrical parameter of the formation surrounding a borehole, which comprises: positioning in the borehole first and second series resonant single turn receiving antennae that are each tuned with a series connected capacitor to increase the sensitivity of the antenna at a predetermined frequency; generating an oscillating electrical drive signal at the predetermined frequency; alternately coupling the electrical drive signal to one and then another of a pair of transmitters to cause an electromagnetic wave signal to propagate through the formation in first one direction and then another so that the propagating electromagnetic wave signal induces the first and second receiving antenna to develop a first pair and then a second pair of pick-up signals; processing the first pair of pick-up signals to produce a first sampled signal, and recording the first sampled signal; processing the second pair of pick-up signals to produce a second sampled signal; and processing the recorded first sampled signal and the second sampled signal to produce a signal that is a function of the formation parameter.

Claim 30

An apparatus for use in a borehole to measure an electrical parameter of the formation surrounding the borehole, comprising: a logging device adapted for movement through said borehole, defining a central longitudinal axis; upper and lower transmitting antenna members disposed about said logging device and axially spaced apart along said central longitudinal axis; a transmitter circuit for selectively energizing said upper and lower transmitting antenna members at a selected transmission frequency, causing said upper and lower transmitting antenna members to radiate an electromagnetic wave signal into said formation surrounding said borehole; a first receiver member disposed between said upper and lower transmitting antenna members, and including: (a) a single loop conductive coil having a predetermined impedance including an inductive reactance component and a resistive component; (b) a reactive circuit element coupled electrically in series with said single loop conductive coil and defining a capacitive reactance equal in magnitude to said inductive reactance component of said single loop conductive coil but opposite in phase from said inductive reactance component of said single loop conductive coil; (c) said single loop conductive coil and said reactive circuit element together defining a first receiving antenna which has an impedance which is essentially only resistive, and low in magnitude to maximize current flow, and which is tuned to a selected reception frequency which is substantially similar to said selected transmission frequency of said transmitter circuit; a second receiver member disposed between said upper and lower transmitting antenna members, and including: (a) a single loop conductive coil having a predetermined impedance including an inductive reactance component and resistive component; (b) a reactive circuit element coupled electrically in series with said single loop conductive coil and defining a capacitive reactance equal in magnitude to said inductive reactance component of said single loop conductive coil but opposite in phase from said conductive reactance component of said single loop conductive coil; (c) said single loop conductive coil and said reactive circuit element together defining a second receiving antenna which has an impedance which is essentially only resistive, and low in magnitude to maximize current flow, and which is tuned to a selected reception frequency which is substantially similar to said selected transmission frequency of said transmitter circuit; wherein said first and second receiver members detect at least one electrical characteristic of energy from said formation during selective energizing of said upper and lower transmitting antenna members and produce first and second output signals corresponding thereto; and means for determining a property of said formation as a function of said first and second output signals.

Claim 31

An apparatus for use in a borehole to measure an electrical parameter of the formation surrounding the borehole, comprising: a logging device adapted for movement through said borehole, defining a central longitudinal axis; upper and lower transmitting antenna members disposed about said logging device and axially spaced apart along said central longitudinal axis; a transmitter circuit for selectively energizing said upper and lower transmitting antenna members at a selected transmission frequency, causing said upper and lower transmitting antenna members to radiate an electromagnetic wave signal into said formation surrounding said borehole; a first receiver member disposed between said upper and lower transmitting antenna members, and including: (a) a single loop conductive coil having a predetermined impedance including an inductive reactance component and a resistive component; (b) a reactive circuit element coupled electrically in series with said single loop conductive coil and defining a capacitive reactance equal in magnitude to said inductive reactance component of said single loop conductive coil but opposite in phase from said inductive reactance component of said single loop conductive coil; (c) said single loop conductive coil and said reactive circuit element together defining a first receiving antenna which has an impedance which is essentially only resistive, and low in magnitude to maximize current flow, and which is tuned to a selected reception frequency which is substantially similar to said selected transmission frequency of said transmitter circuit; a second receiver member disposed between said upper and lower transmitting antenna members, and including: (a) a single loop conductive coil having a predetermined impedance including an inductive reactance component and resistive component; (b) a reactive circuit element coupled electrically in series with said single loop conductive coil and defining a capacitive reactance equal in magnitude to said inductive reactance component of said single loop conductive coil but opposite in phase from said conductive reactance component of said single loop conductive coil; (c) said single loop conductive coil and said reactive circuit element together defining a second receiving antenna which has an impedance which is essentially only resistive, and low in magnitude to maximize current flow, and which is tuned to a selected reception frequency which is substantially similar to said selected transmission frequency of said transmitter circuit; wherein said first and second receiver members detect at least one electrical characteristic of energy from said formation during selective energizing of said upper and lower transmitting antenna members and produce first and second output signals corresponding thereto; and means for determining a property of said formation as a function of said first and second output signals.

Claim 39

An apparatus for use in a borehole to measure an electrical parameter of the formation surrounding the borehole, comprising: a logging device adapted for movement through said borehole, defining a central longitudinal axis; upper and lower transmitting antenna members disposed about said logging device and axially spaced apart along said central longitudinal axis; a transmitter circuit for selectively energizing said upper and lower transmitting antenna members at a selected transmission frequency, causing said upper and lower transmitting antenna members to radiate an electromagnetic wave signal into said formation surrounding said borehole; a first receiver member disposed between said upper and lower transmitting antenna members, and including at least; (a) an antenna assembly having a predetermined impedance including an inductive reactance component, a resistive component, and a capacitive reactance component; (b) wherein said first receiver detects at least one electrical characteristic of energy from said formation during selective energizing of said upper and lower transmitting antenna member and produces a first output signal corresponding thereto which includes a first signal component representative of said at least one electrical characteristic and a first error component originating from said first receiver member; a second receiver member disposed between said upper and lower transmitting antenna members, and including at least; (a) an antenna assembly having a predetermined impedance including an inductive reactance component, a resistive component, and a capacitive reactance component; (b) wherein said second receiver member detects at least one electrical characteristic of energy from said formation during selective energizing of said upper and lower transmitting antenna members and produces a second output signal corresponding thereto which includes a second signal component representative of said at least one electrical characteristic and a second error component originating from said first receiver member; means for combining said first and second output signals to eliminate said first and second error components and isolate said first and second signal components, thereby rendering said first and second receiver members impervious to inherent error components.

Claim 40

An apparatus for use in a borehole to measure an electrical parameter of the formation surrounding the borehole, comprising: a logging device adapted for movement through said borehole, defining a central longitudinal axis; upper and lower transmitting antenna members disposed about said logging device and axially spaced apart along said central longitudinal axis; a transmitter circuit for selectively energizing said upper and lower transmitting antenna members at a selected transmission frequency, causing said upper and lower transmitting antenna members to radiate an electromagnetic wave signal into said formation surrounding said borehole; a first receiver member disposed between said upper and lower transmitting antenna members, and including at least; (a) an antenna assembly having a predetermined impedance including an inductive reactance component, a resistive component, and a capacitive reactance component; (b) wherein said first receiver detects at least one electrical characteristic of energy from said formation during selective energizing of said upper and lower transmitting antenna member and produces a first output signal corresponding thereto which includes a first signal component representative of said at least one electrical characteristic and a first error component originating from said first receiver member; a second receiver member disposed between said upper and lower transmitting antenna members, and including at least; (a) an antenna assembly having a predetermined impedance including an inductive reactance component, a resistive component, and a capacitive reactance component; (b) wherein said second receiver member detects at least one electrical characteristic of energy from said formation during selective energizing of said upper and lower transmitting antenna members and produces a second output signal corresponding thereto which includes a second signal component representative of said at least one electrical characteristic and a second error component originating from said first receiver member; means for combining said first and second output signals to eliminate said first and second error components and isolate said first and second signal components, thereby rendering said first and second receiver members impervious to inherent error components.

Claim 41

An apparatus for use in a borehole to measure an electrical parameter of the formation surrounding the borehole, comprising: a logging device adapted for movement through said borehole, defining a central longitudinal axis; upper and lower transmitting antenna members disposed about said logging device and axially spaced apart along said central longitudinal axis; a transmitter circuit for selectively energizing said upper and lower transmitting antenna members at a selected transmission frequency, causing said upper and lower transmitting antenna member to radiate an electromagnetic wave signal into said formation surrounding said borehole; a first receiver member disposed between said upper and lower transmitting antenna members, an including at least; (a) a single loop conductive coil having a predetermined impedance including an inductive reactance component and a resistive component; (b) a reactive circuit element coupled electrically in series with said single loop conductive coil and defining a capacitive reactance equal in magnitude to said inductive reactance component of said single loop conductive coil but opposite in phase from said inductive reactance component of said single loop conductive coil; (c) said single loop conductive coil and said reactive circuit element together defining a first receiving antenna which has an impedance which is essentially only resistive, and which is tuned to a selected reception frequency which is substantially similar to said selected transmission frequency of said transmitter circuit; (d) wherein said first receiver member detects at least one electrical characteristic of energy from said formation during selective energizing of said upper and lower transmitting antenna members and produces a first output signal corresponding thereto which includes a first signal component representative of said at least one electrical characteristic and a first error component originating from said first receiver member; a second receiver member disposed between said upper and lower transmitting antenna members, and including at least; (a) a single loop conductive coil having a predetermined impedance including an inductive reactance component and a resistive component; (b) a reactive circuit element coupled electrically in series with said single loop conductive coil and defining a capacitive reactance equal in magnitude to said inductive reactance component of said single loop conductive coil but opposite in phase from said inductive reactance component of said single loop conductive coil; (c) said single loop conductive coil and said reactive circuit element together defining a second receiving antenna which has an impedance which is essentially only resistive, and which is tuned to a selected reception frequency which is substantially similar to said selected transmission frequency of said transmitter circuit; (d) wherein said second receiver member detects at least one electrical characteristic of energy from said formation during selective energizing of said upper and lower transmitting antenna members and produces a second output signal corresponding thereto which includes a second signal component representative of said at least one electrical characteristic and a second error component originating from said second receiver member; and means for combining said first and second output signals to eliminate said first and second error components and isolate said first and second signal components, thereby rendering said first and second receiver members impervious to inherent error components.

Claim 42

An apparatus for use in a borehole to measure an electrical parameter of the formation surrounding the borehole, comprising: a logging device adapted for movement through said borehole, defining a central longitudinal axis; upper and lower transmitting antenna members disposed about said logging device and axially spaced apart along said central longitudinal axis; a transmitter circuit for selectively energizing said upper and lower transmitting antenna members at a selected transmission frequency, causing said upper and lower transmitting antenna member to radiate an electromagnetic wave signal into said formation surrounding said borehole; a first receiver member disposed between said upper and lower transmitting antenna members, an including at least; (a) a single loop conductive coil having a predetermined impedance including an inductive reactance component and a resistive component; (b) a reactive circuit element coupled electrically in series with said single loop conductive coil and defining a capacitive reactance equal in magnitude to said inductive reactance component of said single loop conductive coil but opposite in phase from said inductive reactance component of said single loop conductive coil; (c) said single loop conductive coil and said reactive circuit element together defining a first receiving antenna which has an impedance which is essentially only resistive, and which is tuned to a selected reception frequency which is substantially similar to said selected transmission frequency of said transmitter circuit; (d) wherein said first receiver member detects at least one electrical characteristic of energy from said formation during selective energizing of said upper and lower transmitting antenna members and produces a first output signal corresponding thereto which includes a first signal component representative of said at least one electrical characteristic and a first error component originating from said first receiver member; a second receiver member disposed between said upper and lower transmitting antenna members, and including at least; (a) a single loop conductive coil having a predetermined impedance including an inductive reactance component and a resistive component; (b) a reactive circuit element coupled electrically in series with said single loop conductive coil and defining a capacitive reactance equal in magnitude to said inductive reactance component of said single loop conductive coil but opposite in phase from said inductive reactance component of said single loop conductive coil; (c) said single loop conductive coil and said reactive circuit element together defining a second receiving antenna which has an impedance which is essentially only resistive, and which is tuned to a selected reception frequency which is substantially similar to said selected transmission frequency of said transmitter circuit; (d) wherein said second receiver member detects at least one electrical characteristic of energy from said formation during selective energizing of said upper and lower transmitting antenna members and produces a second output signal corresponding thereto which includes a second signal component representative of said at least one electrical characteristic and a second error component originating from said second receiver member; and means for combining said first and second output signals to eliminate said first and second error components and isolate said first and second signal components, thereby rendering said first and second receiver members impervious to inherent error components.