Method and apparatus for acquiring borehole seismic data in two opposite directions

Claim 3

A method according to claim 1, wherein: said emitting is omnidirectional; and said detecting comprises performing omnidirectional reception and bidirectional reception of the echoes or reflected and refracted pressure waves, the two directions of bidirectional reception defining a plane orthogonal to the longitudinal plane of symmetry of said borehole.

Claim 4

A method according to claim 1, wherein: said emitting is bidirectional; and said detecting comprises performing omnidirectional reception and bidirectional reception of the echoes or reflected and refracted pressure waves, the two directions of said emission and of said bidirectional reception being respectively contained in a plane orthogonal to said longitudinal plane of symmetry of said borehole.

Claim 5

A method according to claim 1, wherein: said emitting is omnidirectional and bidirectional; and said detecting comprises performing omnidirectional reception, the two directions of said bidirectional emission defining a plane orthogonal to said longitudinal plane of symmetry of the borehole.

Claim 6

A method according to claim 1, wherein: said emitting is bidirectional and omnidirectional; and said detecting comprises performing bidirectional reception, the two directions of said bidirectional emission and of said bidirectional reception being respectively contained in a plane orthogonal to said longitudinal plane of symmetry of said borehole.

Claim 11

Apparatus for acquiring borehole seismic data in two opposite directions in a borehole parallel or quasi-parallel to surrounding geological strata, comprising: emission means for emitting an omnidirectional and/or a bidirectional pressure wave; and bidirectional detection means for detecting echoes reflected and refracted by the adjacent geological formations, the detection means being disposed at an offset from the emission means, and serving to discriminate between pressure waves from the two opposite directions that have been reflected and refracted by said geological formations in a longitudinal plane of symmetry of said borehole, the discrimination being performed on the basis of detecting the sum and the difference of the echo signals coming from said opposite directions.

Claim 12

Apparatus for acquiring borehole seismic data in two opposite directions in a borehole parallel or quasi-parallel to surrounding geological strata, comprising: emission means for emitting an omnidirectional and/or a bidirectional pressure wave; and bidirectional detection means for detecting echoes reflected and refracted by the adjacent geological formations, the detection means being disposed at an offset from the emission means, and serving to discriminate between pressure waves from the two opposite directions that have been reflected and refracted by said geological formations in a longitudinal plane of symmetry of said borehole, the discrimination being performed on the basis of detecting the sum and the difference of the echo signals coming from said opposite directions.

Claim 13

Apparatus according to claim 10, wherein said emission means are constituted by a pulse source.

Claim 14

Apparatus according to claim 10 or 11, wherein said emission means are constituted by a vibration generating source.

Claim 15

Apparatus according to claims 10 or 11, wherein said bidirectional detection means comprise a hydrophone disposed in the ambient medium of the borehole constituted by mud.

Claim 16

Apparatus according to claims 10 or 11, wherein said bidirectional detection means comprise either a set of two dipole hydrophones whose axes are mutually perpendicular and perpendicular to the axis of the apparatus, or bidirectional geophone comprising two vibration transducer components disposed orthogonally in a plane that is orthogonal to the longitudinal axis of the apparatus, the two vibration transducer components being designed to be mechanically coupled in operation with the walls of the borehole.

Claim 17

Apparatus according to claim 12, wherein the pulse source and vibration generator are disposed close to the dipole hydrophones and bidirectional geophone.

Claim 18

Apparatus according to claims 10 or 11, further comprising a plurality of emission means and bidirectional detection means, said means being capable of being activated selectively to obtain an offset distance between the reception means and the emission means that is adjustable depending on user choice.

Claim 19

A method according to claim 6, wherein said omnidirectional and bidirectional emission or reception are both performed in that order or in the opposite order.

Claim 20

A method according to claim 6, wherein said detecting is performed on the basis of said omnidirectional and bidirectional reception, said omnidirectional reception serving with omnidirectional emission to obtain a signal representative of echoes proportional to the sum of the pressures (R+R') of the pressure waves reflected and refracted in said longitudinal plane of symmetry of the borehole, said bidirectional reception serving to obtain a signal representative of the difference between the pressure gradients (∂R/∂x and ∂R/∂x) in said directions of the pressure waves reflected or refracted in said longitudinal plane of symmetry of the borehole.

Claim 21

A method according to claim 6, wherein said detecting is performed on the basis of said omnidirectional and bidirectional reception, said omnidirectional reception serving with omnidirectional emission to obtain a signal representative of echoes proportional to the sum of the pressures (R+R') of the pressure waves reflected and refracted in said longitudinal plane of symmetry of the borehole, said bidirectional reception serving to obtain a signal representative of the difference between the pressure gradients (∂R/∂x and ∂R/∂x) in said directions of the pressure waves reflected or refracted in said longitudinal plane of symmetry of the borehole.

Claim 22

A method according to claim 6, wherein said detecting is performed on the basis of said omnidirectional and bidirectional reception, said bidirectional reception in association with bidirectional emission serving to obtain a signal representative of echoes proportional to the sum of the pressures (R+R') of the pressure waves reflected and refracted in said longitudinal plane of symmetry of the borehole, said bidirectional reception serving to obtain a signal representative of the difference between the pressure gradients (∂R/∂x and ∂R/∂x) in said direction of the pressure waves reflected and refracted in said longitudinal plane of symmetry of the borehole.

Claim 23

A method according to claim 7, wherein said detecting is performed on the basis of said omnidirectional and bidirectional reception, said bidirectional reception in association with bidirectional emission serving to obtain a signal representative of echoes proportional to the sum of the pressures (R+R') of the pressure waves reflected and refracted in said longitudinal plane of symmetry of the borehole, said bidirectional reception serving to obtain a signal representative of the difference between the pressure gradients (∂R/∂x and ∂R/∂x) in said direction of the pressure waves reflected and refracted in said longitudinal plane of symmetry of the borehole.

Claim 24

Apparatus according to claim 12, wherein said bidirectional detection means comprise a hydrophone disposed in the ambient medium of the borehole constituted by mud.

Claim 25

Apparatus according to claim 12, wherein said bidirectional detection means comprise either a set of two dipole hydrophones whose axes are mutually perpendicular and perpendicular to the axis of the apparatus, or a bidirectional geophone, comprising two vibration transducer components disposed orthogonally in a plane that is orthogonal to the longitudinal axis of the apparatus, the two vibration transducer components being designed to be mechanically coupled in operation with walls of the borehole.

Claim 26

Apparatus according to claim 13, wherein said bidirectional detection means comprise either a set of two dipole hydrophones whose axes are mutually perpendicular and perpendicular to the axis of the apparatus, or a bidirectional geophone, comprising two vibration transducer components disposed orthogonally in a plane that is orthogonal to the longitudinal axis of the apparatus, the two vibration transducer components being designed to be mechanically coupled in operation with walls of the borehole.

Claim 27

Apparatus according to claim 14, wherein the pulse source and vibration generator are disposed close to the dipole hydrophones and bidirectional geophone.

Claim 28

Apparatus according to claim 12, further comprising a plurality of emission means and bidirectional detection means, said means being capable of being activated selectively to obtain an offset distance between the reception means and the emission means that is adjustable depending on user choice.

Claim 29

Apparatus according to claim 13, further comprising a plurality of emission means and bidirectional detection means, said means being capable of being activated selectively to obtain an offset distance between the reception means and the emission means that is adjustable depending on user choice.

Claim 30

Apparatus according to claim 14, further comprising a plurality of emission means and bidirectional detection means, said means being capable of being activated selectively to obtain an offset distance between the reception means and the emission means that is adjustable depending on user choice.

Claim 31

Apparatus according to claim 15, further comprising a plurality of emission means and bidirectional detection means, said means being capable of being activated selectively to obtain an offset distance between the reception means and the emission means that is adjustable depending on user choice.

Claim 34

A method according to claim 30, wherein said detecting a signal proportional to the sum and said detecting a signal representative of the difference between pressure gradients comprises: omnidirectional emission of a pressure wave from a first point in said borehole; omnidirectional reception at a second point, offset from said first point, of the pressure waves reflected and refracted in said first and second directions so as to detect a signal representative of echoes proportional to the sum of the pressure waves reflected and refracted in said first direction and the pressure waves reflected and refracted in said second direction; and bidirectional reception at said second point of the pressure waves reflected and refracted in said first and second directions so as to detect a signal representative of the difference between the pressure gradients of the pressure waves reflected and refracted in said first direction and the pressure waves reflected and refracted in said second direction.

Claim 35

A method according to claim 30, wherein said detecting a signal proportional to the sum and said detecting a signal representative of the difference between pressure gradients comprises: bidirectional emission from a first point of a pressure wave; bidirectional reception at said second point of the pressure waves reflected and refracted in said first and second directions so as to detect a signal representative of echoes proportional to the sum of the pressure waves reflected and refracted in said first direction and the pressure waves reflected and refracted in said second direction; and omnidirectional reception at a second point of the pressure waves reflected and refracted in said first and second directions so as to detect a signal representative of the difference between the pressure gradients of the pressure waves reflected and refracted in said first direction and the pressure waves reflected and refracted in said second direction.

Claim 36

A method according to claim 30, wherein said detecting a signal proportional to the sum and said detecting a signal representative of the difference between pressure gradients comprises: omnidirectional emission from a first point of a pressure wave; bidirectional emission from a first point of a pressure wave; and omnidirectional reception at a second point of the pressure waves reflected and refracted in said first and second directions so as to detect, respectively, both a signal representative of echoes proportional to the sum of and a signal representative of the difference between the pressure gradients of the pressure waves reflected and refracted in said first direction and the pressure waves reflected and refracted in said second direction.

Claim 37

A method according to claim 30, wherein said detecting a signal proportional to the sum and said detecting a signal representative of the difference between pressure gradients comprises: bidirectional emission from a first point of a pressure wave; omnidirectional emission from a first point of a pressure wave; bidirectional reception at a second point of the pressure waves reflected and refracted in said first and second directions so as to detect, respectively, both a signal representative of echoes proportional to the sum of and a signal representative of the difference between the pressure gradients of the pressure waves reflected and refracted in said first direction and the pressure waves reflected and refracted in said second direction.

Claim 38

Apparatus for acquiring borehole seismic data in a first and a second opposite directions in a borehole surrounded by geological formations, said first and second directions being contained in a longitudinal plane of symmetry of said borehole passing through a longitudinal axis of said borehole and being symmetrical about said axis, said axis being substantially parallel to said geological formations, said apparatus comprising: emission means for emitting a bidirectional and an omnidirectional pressure wave; bidirectional reception means, offset from said emission means, for receiving pressure waves reflected and refracted in said first and second directions, so as to carry out, respectively, detection of a signal representative of echoes proportional to the sum of the pressure waves reflected and refracted in said first direction and the pressure waves reflected and refracted in said second direction and detection of a signal representative of the difference between pressure gradients of the pressure waves reflected and refracted in said first direction and the pressure waves reflected and refracted in said second direction; and discrimination means for discriminating between said pressure waves reflected and refracted in said first direction and said pressure waves reflected and refracted in said second direction, based upon the detection of said signals representative of said sum and said difference.

Claim 39

Apparatus for acquiring borehole seismic data in a first and a second opposite directions in a borehole surrounded by geological formations, said first and second directions being contained in a longitudinal plane of symmetry of said borehole passing through a longitudinal axis of said borehole and being symmetrical about said axis, said axis being substantially parallel to said geological formations, said apparatus comprising: emission means for emitting a bidirectional and an omnidirectional pressure wave; bidirectional reception means, offset from said emission means, for receiving pressure waves reflected and refracted in said first and second directions, so as to carry out, respectively, detection of a signal representative of echoes proportional to the sum of the pressure waves reflected and refracted in said first direction and the pressure waves reflected and refracted in said second direction and detection of a signal representative of the difference between pressure gradients of the pressure waves reflected and refracted in said first direction and the pressure waves reflected and refracted in said second direction; and discrimination means for discriminating between said pressure waves reflected and refracted in said first direction and said pressure waves reflected and refracted in said second direction, based upon the detection of said signals representative of said sum and said difference.

Claim 40

Apparatus according to claim 35, wherein said emission means comprises a pulse source.

Claim 41

Apparatus according to claim 35, wherein said emission means comprises a vibration generating source.

Claim 42

Apparatus according to claim 35, wherein said bidirectional detection means comprises a hydrophone disposed in the ambient medium of the borehole constituted by mud.

Claim 43

Apparatus according to claim 35, wherein said bidirectional detection means comprises a set of two dipole hydrophones whose axes are mutually perpendicular and perpendicular to the axis of the apparatus, or a bidirectional geophone comprising two vibration transducer components disposed orthogonally in a plane that is orthogonal to the longitudinal axis of the apparatus, the two vibration transducer components being designed to be mechanically coupled in operation with the walls of the borehole.

Claim 44

Apparatus according to claim 37 or 39, wherein the pulse source and vibration generator are disposed close to the dipole hydrophones and bidirectional geophone.

Claim 45

Apparatus according to claim 35, wherein said apparatus further comprises a plurality of emission means and bidirectional detection means, said means being capable of being activated selectively to obtain an offset distance between the reception means and the emission means that is adjustable depending on user choice.