Logging tool with independently energizable transmitters
A downhole induction resistivity assembly that comprises a downhole tool string component. The tool string component comprises an induction transmitter. The transmitter is adapted to induce an induction field in the surrounding formation. A first induction receiver is spaced apart from the transmitter and is adapted to measure the induction field. A magnetic field generating mechanism is disposed adjacent on either or both sides of the transmitter and adapted to guide the transmitter's signal into the formation. A second induction receiver is disposed in close proximity to the magnetic field generating mechanism and is adapted to measure the magnetic field generated by the mechanism.
1. A logging tool comprising:
a component configured to be conveyed into a wellbore, said component having a central axis and a length along said central axis, said component including:
at least one transmitter adapted to generate an induction signal and transmit said induction signal into a formation adjacent to said wellbore, said transmitter including a plurality of transmitter units adapted to be independently energized;
a Halbach array proximate said transmitter, said Halbach array being adapted to generate a magnetic field which influences said induction signal;
at least one receiver spaced apart from said transmitter along said length of said component, said receiver being adapted to receive a return induction signal representative of said formation; and,
a cover positioned over at least one of said transmitter and said receiver.
2. The logging tool of claim 1 , wherein said plurality of transmitter units are disposed in at least one recess of said component.
3. The logging tool of claim 1 , wherein said plurality of transmitter units are spaced around said component at a first radial distance.
4. The logging tool of claim 3 , wherein said at least one receiver includes a plurality of receiver units spaced around the component at a second radial distance.
5. The logging tool of claim 4 , wherein said receiver units are configured for independent deactivation.
6. The logging tool of claim 4 , wherein the first radial distance and the second radial distance are equal.
7. The logging tool of claim 4 , wherein said transmitter units and said receiver units are tilted with respect to said central axis of said component.
8. The logging tool of claim 4 , wherein said transmitter units and said receiver units are substantially parallel with respect to said central axis of said component.
9. The logging tool of claim 1 , wherein said cover is a plastic.
10. The logging tool of claim 1 , wherein said component is configured to conveyed into said wellbore on at least one of a drill string and a wireline.
11. The logging tool of claim 1 , further comprising:
a reference receiver located along said length of said component and between said transmitter and said receiver, said reference receiver being adapted to measure said magnetic field and to generate a magnetic field signal representative of said magnetic field; and
a control loop adapted to receive said magnetic field signal from said reference receiver and to execute a command to said Halbach array to adjust said magnetic field.
12. The logging tool of claim 1 , wherein at least one of said plurality of transmitter units is adapted to generate and transmit said induction signal into a portion of said formation in substantially a single direction.
13. The logging tool of claim 1 , wherein at least one of said plurality of transmitter units is adapted to generate and transmit said induction signal into a portion of said formation associated with a fraction of a circumference of said wellbore.
14. A logging tool comprising:
a component configured to be conveyed into a wellbore, said component having a central axis and a length along said central axis, said component including:
at least one transmitter adapted to generate an induction signal and transmit said induction signal into a formation adjacent to said wellbore, said transmitter including a plurality of transmitter units adapted to be independently energized;
a magnetic field generating mechanism proximate said transmitter, said magnetic field generating mechanism being adapted to generate a magnetic field which influences said induction signal;
at least one receiver spaced apart from said transmitter along said length of said component, said receiver being adapted to receive a return induction signal representative of said formation;
a reference receiver located along said length of said component and between said transmitter and said receiver, said reference receiver being adapted to measure said magnetic field and to generate a magnetic field signal representative of said magnetic field;
a control loop adapted to receive said magnetic field signal from said reference receiver and to execute a command to said magnetic field generating mechanism to adjust said magnetic field; and
a cover positioned over at least one of said transmitter and said receiver.
15. The logging tool of claim 10 , wherein said magnetic field generating mechanism includes a Halbach array.
16. The logging tool of claim 10 , wherein at least one of said plurality of transmitter units is adapted to generate and transmit said induction signal into a portion of said formation in substantially a single direction.
17. The logging tool of claim 10 , wherein at least one of said plurality of transmitter units is adapted to generate and transmit said induction signal into a portion of said formation associated with a fraction of a circumference of said wellbore.
18. A logging tool comprising:
a component configured to be conveyed into a wellbore, said component having with a central axis and a length along said central axis, said component including:
at least one transmitter adapted to generate an induction signal and transmit said induction signal into a formation adjacent to said wellbore, said transmitter including a plurality of transmitter units adapted to be independently energized;
a magnetic field generating mechanism proximate said transmitter, said magnetic field generating mechanism being adapted to generate a magnetic field which influences said induction signal;
at least one of said transmitter and said magnetic field generating mechanism including a Halbach array;
at least one receiver spaced apart from said transmitter along said length of said component, said receiver being adapted to receive a return induction signal representative of said formation; and
a cover positioned over at least one of said transmitter and said receiver.