Method and system for measuring azimuthal anisotropy effects using acoustic multipole transducers

A method, using at least one multipole transducer, for logging a borehole having a longitudinal axis to obtain information for measuring azimuthal anisotropy of a formation traversed by the borehole, including the steps of:

• (a) operating a first transducer disposed in the borehole to generate a first acoustic signal that will propagate into the formation from within the borehole;
• (b) detecting an arrival of the first acoustic signal at a second transducer disposed in the borehole, where one of the first and second transducers is a monopole transducer having multipole order n=0 and the other is a multipole transducer having multipole order n+2m, where m is a member of the set of integers and half-integer numbers and n+2m>0, at least one of the transducers defining a first azimuthal angle relative to the longitudinal axis of the borehole;
• (c) rotating said multipole transducer to define a second azimuthal angle relative to the longitudinal axis of the borehole;
• (d) operating said first transducer to generate a second acoustic signal azimuthally distinct from said first acoustic signal;
• and
• (e) detecting the arrival of the second acoustic signal with the second transducer.

An apparatus for logging a borehole to obtain information for measuring azimuthal anisotropy of a formation traversed by the borehole, including:

• (a) a housing adapted to be suspended in the borehole and having a longitudinal axis;
• (b) a first monopole transducer having multipole order n=0 mounted in the housing and capable of generating a first acoustic signal that will propagate from within the borehole into the formation;
• (c) a first multipole receiver, having multipole order n+2m, where n is zero, m is a member of the set of integers and half-integer numbers, and n+2m>0, and capable of detecting an arrival of the first acoustic signal, said first multipole receiver being mounted in the housing at a first azimuthal angle relative to the longitudinal axis;
• and
• (d) a second multipole receiver, having multipole order n+2p, where n is zero, p is a member of the set of integers and half-integer numbers, and n+2p>0, and capable of detecting an arrival of the first signal, said second multipole receiver being mounted in the housing at a second azimuthal angle relative to the longitudinal axis.

An apparatus for logging a borehole to obtain information for measuring azimuthal anisotropy of a formation traversed by the borehole, including:

• (a) a housing adapted to be suspended in the borehole and having a longitudinal axis;
• (b) a first multipole transmitter having multipole order n+2m, where n is zero, m is a member of the set of integers and half-integer numbers, and n+2m>0, said first multipole transmitter being mounted in the housing at a first azimuthal angle relative to the longitudinal axis, and being capable of generating a first acoustic signal that will propagate from within the borehole into the formation;
• (c) a second multipole transmitter, having multipole order n+2p, where n is zero, p is a member of the set of integers and half-integer numbers, and n+2p>0, said second multipole transmitter being mounted in the housing at a second azimuthal angle relative to the longitudinal axis, and being capable of generating a second acoustic signal that will propagate from within the borehole into the formation;
• and
• (d) a monopole receiver, having multipole order n=0, mounted in the housing at a position spaced along the longitudinal axis from the first transmitter and the second transmitter, and capable of detecting arrivals of the first and second acoustic signals.

An apparatus for logging a borehole to obtain information for measuring azimuthal anisotropy of a formation traversed by the borehole, including:

• (a) a housing adapted to be suspended in the borehole and having a longitudinal axis;
• (b) a first monopole transducer, having multipole order n=0, mounted in the housing and capable of generating an acoustic signal that will propagate from within the borehole into the formation;
• (c) a second transducer having multipole order n+2m, where n is zero, m is a member of the set of integers and half-integer numbers, and n+2m>0, said second transducer being mounted in the housing and capable of detecting an arrival of the acoustic signal;
• and
• (d) means for rotating the second transducer azimuthally.

A method, using at least one multipole transducer, for logging a borehole having a longitudinal axis to obtain information for measuring azimuthal anisotropy of a formation traversed by the borehole, including the steps of:

• (a) operating a first transducer disposed in the borehole to generate a first acoustic signal that will propagate into the formation from within the borehole;
• (b) detecting an arrival of the first acoustic signal at a second transducer disposed in the borehole, where one of the first and second transducers is a dipole transducer and the other is a quadrupole transducer, at least one of the transducers defining a first azimuthal angle relative to the longitudinal axis of the borehole;
• and
• (c) at a location within the borehole, detecting another acoustic arrival associated with a second azimuthal angle relative to the longitudinal axis of the borehole.

A method, using at least one multipole transducer, for logging a borehole having a longitudinal axis to obtain information for measuring azimuthal anisotropy of a formation traversed by the borehole, including the steps of:

• (a) operating a first transducer disposed in the borehole to generate a first acoustic signal that will propagate into the formation from within the borehole;
• (b) detecting an arrival of the first acoustic signal at a second transducer disposed in the borehole, where one of the first and second transducers is a monopole transducer and the other is a dipole transducer, at least one of the transducers defining a first azimuthal angle relative to the longitudinal axis of the borehole;
• and
• (c) at a location within the borehole, detecting another acoustic arrival, where the arrival detected in this step (c) is associated with a second azimuthal angle relative to the longitudinal axis of the borehole.

A method, using at least one multipole transducer, for logging a borehole having a longitudinal axis to obtain information for measuring azimuthal anisotropy of a formation traversed by the borehole, including the steps of:

• (a) operating a first transducer disposed in the borehole to generate a first acoustic signal that will propagate into the formation from within the borehole;
• (b) detecting an arrival of the first acoustic signal at a second transducer disposed in the borehole, where one of the first and second transducers is a monopole transducer and the other is a octopole transducer, at least one of the transducers defining a first azimuthal angle relative to the longitudinal axis of the borehole;
• and
• (c) at a location within the borehole, detecting another acoustic arrival, where the arrival detected in this step (c) is associated with a second azimuthal angle relative to the longitudinal axis of the borehole.

An apparatus for logging a borehole to obtain information for measuring azimuthal anisotropy of a formation traversed by the borehole, including:

• (a) a housing adapted to be suspended in the borehole and having a longitudinal axis;
• (b) a first dipole transducer having mounted in the housing and capable of generating a first acoustic signal that will propagate from within the borehole into the formation;
• (c) a first multipole receiver, having multipole order n+2m, where n is a one, m is a member of the set of integers and half-integer numbers, and n+2m>0, and capable of detecting an arrival of the first acoustic signal, said first multipole receiver being mounted in the housing at a first azimuthal angle relative to the longitudinal axis;
• and
• (d) a second multipole receiver, having multipole order n+2p, where n is one, p is a member of the set of integers and half-integer numbers, and n+2p>0, and capable of detecting an arrival of the first signal, said second multipole receiver being mounted in the housing at a second azimuthal angle relative to the longitudinal axis.

An apparatus for logging a borehole to obtain information for measuring azimuthal anisotropy of a formation traversed by the borehole, including:

• (a) a housing adapted to be suspended in the borehole and having a longitudinal axis;
• (b) a first multipole transmitter having multipole order n+2m, where n is one, m is a member of the set of integers and half-integer numbers, and n+2m>0, said first multipole transmitter being mounted in the housing at a first azimuthal angle relative to the longitudinal axis, and being capable of generating a first acoustic signal that will propagate from within the borehole into the formation;
• (c) a second multipole transmitter, having multipole order n+2p, where n is one, p is a member of the set of integers and half-integer numbers, and n+2p>0, said second multipole transmitter being mounted in the housing at a second azimuthal angle relative to the longitudinal axis, and being capable of generating a second acoustic signal that will propagate from within the borehole into the formation;
• and
• (d) a dipole receiver mounted in the housing at a position spaced along the longitudinal axis from the first transmitter and the second transmitter, and capable of detecting arrivals of the first and second acoustic signals.

An apparatus for logging a borehole to obtain information for measuring azimuthal anisotropy of a formation traversed by the borehole, including:

• (a) a housing adapted to be suspended in the borehole and having a longitudinal axis;
• (b) a first transducer having multipole order n+2m, where n is zero, m is a member of the set of integers and half-integer numbers, and n+2m>0, said second transducer being mounted in the housing and capable of detecting an arrival of the acoustic signal;
• (c) a second monopole transducer having multipole order n=0 mounted in the housing and capable of generating an acoustic signal that will propagate from within the borehole into the formation;
• and
• (d) means for rotating the first transducer azimuthally.

An apparatus for logging a borehole to obtain information for measuring azimuthal anisotropy of a formation traversed by the borehole, including:

• (a) a housing adapted to be suspended in the borehole and having a longitudinal axis;
• (b) a first transducer having multipole order n+2m, where n is one, m is a member of the set of integers and half-integer numbers, and n+2m>0, said second transducer being mounted in the housing and capable of detecting an arrival of the acoustic signal;
• (c) a second dipole transducer having multipole order n=1 mounted in the housing and capable of generating an acoustic signal that will propagate from within the borehole into the formation;
• and
• (d) means for rotating the first and second transducers azimuthally with respect to each other.

A method, using at least one multipole transducer, for logging a borehole having a longitudinal axis to obtain information for measuring azimuthal anisotropy of a formation traversed by the borehole, including the steps of:

• (a) operating a first transducer disposed in the borehole to generate a first acoustic signal that will propagate into the formation from within the borehole;
• (b) detecting an arrival of the first acoustic signal at a second transducer disposed in the borehole, where one of the first and second transducers is a dipole transducer having multipole order n=1 and the other is a multipole transducer having multipole order n+2m, where m is a member of the set of integers and half-integer numbers and n+2m>0, at least one of the transducers defining a first azimuthal angle relative to the longitudinal axis of the borehole;
• (c) rotating at least one of said first and second transducers to define a second azimuthal angle relative to the longitudinal axis of the borehole;
• (d) operating said first transducer to generate a second acoustic signal azimuthally distinct from said first acoustic signal;
• and
• (e) detecting the arrival of the second acoustic signal with the second transducer.