Abstract: The present invention relates to a system for emitting seismic waves in an underground formation traversed by a well comprising a casing (10). The system comprises a casing seal (1) allowing passage of a magnetic field, an active part generating seismic waves, made up of magnetic-field active elements (4) and arranged outside the casing seal, and a mobile magnetic field induction source (8) arranged inside the casing seal. The invention also relates to a method implementing the seismic wave emission system.

Abstract: The present invention relates to a system for emitting seismic waves in an underground formation traversed by a well comprising a casing (10). The system comprises a casing seal (1) allowing passage of a magnetic field, an active part generating seismic waves, made up of magnetic-field active elements (4) and arranged outside the casing seal, and a mobile magnetic field induction source (8) arranged inside the casing seal. The invention also relates to a method implementing the seismic wave emission system.

Abstract: A device for seismic emission in an underground formation comprising one or more vibrators of any type and method for implementing same. According to a preferred embodiment, each vibrator comprises at least one pillar (1) of sensitive elements (of piezoelectric type for example) between two end plates or slabs (2, 3) and a signal generator for applying vibrational signals to the pillar. The pillar (1) is coated with a protective sheath (4) and the vibrator is positioned in a well or cavity (W) and embedded in a mass of a solid coupling material (7) in contact with protective sheath (4) and the two end plates (2, 3) over at least part of each of the respective faces thereof, which provides coupling of the vibrator with the surrounding formation. The vibrators can be buried at intervals in relation to one another in a well. Sequential triggering thereof with selected delays allows reinforcement of the waves emitted by the device in a preferred direction.

Abstract: Seismic emission system for use in an underground formation, using at least one seismic source movable successively in a plurality of prepared activation locations and method for implementing same. The system comprises for example a plurality of coupling devices (1) including each for example two anchor elements (12, 9?) tightly coupled with the formation (by cementing for example). These anchor elements are secured to the seismic source (V) such as a vibrator of any type or an impulsive source by transmission elements (10, 13). The seismic source is coupled with coupling device (1) by fast locking means (18, 19). Coupling devices (1) can be preinstalled at a plurality of prepared activation locations above the formation to be monitored. Seismic monitoring operations can be carried out by moving at least one seismic source successively between the different locations where coupling devices (1) are installed.

Abstract: An electromechanical device for generating elastic waves in a material medium such as the subsoil in a frequency range where the wavelengths of the waves generated are great in view of the dimensions of the device, and method of implementation. The device comprises one or more vibrators which are buried in the medium, associated with a control system. Each vibrator comprises at least one inertia mass (1), several plates (2, 3) providing mechanical coupling with the medium, electromechanical transducers (4, 5) connecting inertia masses (1) to plates (2, 3). A control system (7) applies to the various transducers (4, 5) respective control signals so that the resulting elastic wavefield generated in the medium by the device is preferentially oriented in one or more directions.

Abstract: The invention relates to a device for seismic emission in an underground formation, comprising one or more vibrators of any type, and to a method of implementing same. In a preferred embodiment, each vibrator comprises at least one pillar (1) of sensitive elements (e.g. piezoelectric type) which is disposed between two end plates or horns (2, 3) and a signal generator which applies vibratory signals at the pillar. Said pillar (1) is encased in a protective sleeve (4) and the vibrator is positioned in a pit or cavity (W) and embedded in a mass of solid coupling material (7) which is in contact with the protective sleeve (4) and with the two end plates (2, 3) on at least one part of each of the respective faces thereof and which connects the vibrator to the surrounding formation. Several of such vibrators can be buried at intervals from one another in the pit.

Abstract: A method and device for seismic exploration of a subsea geologic formation by pickups set on the sea bottom and intermittently connectable to active data acquisition stations (11) brought nearby. Permanent passive reception stations (1) comprising a heavy pedestal provided with housings for seismic pickups (geophones (6), hydrophone (7) which receive acoustic or seismic signals from the underlying formation are arranged at the bottom of the water body. When collection sessions for the signals received by the pickups are scheduled, mobile active acquisition stations (11) connected to permanent passive reception stations (1) are positioned at the bottom of the water body. The signals picked up are then recorded, for the time required to carry out at least one session of acquisition and recording of the acoustic or seismic signals received by the passive stations in response to the emission of seismic waves by one or more seismic sources.

Abstract: A method and device for seismic exploration of a subsea geologic formation by pickups set on the sea bottom and intermittently connectable to active data acquisition stations (11) brought nearby. Permanent passive reception stations (1) comprising a heavy pedestal provided with housings for seismic pickups (geophones (6), hydrophone (7)) which receive acoustic or seismic signals from the underlying formation are arranged at the bottom of the water body. When collection sessions for the signals received by the pickups are scheduled, mobile active acquisition stations (11) connected to permanent passive reception stations (1) are positioned at the bottom of the water body. The signals picked up are then recorded, for the time required to carry out at least one session of acquisition and recording of the acoustic or seismic signals received by the passive stations in response to the emission of seismic waves by one or more seismic sources.

Abstract: Seismic emission system for use in an underground formation, using at least one seismic source movable successively in a plurality of prepared activation locations and method for implementing same. The system comprises for example a plurality of coupling devices (1) including each for example two anchor elements (12, 9?) tightly coupled with the formation (by cementing for example). These anchor elements are secured to the seismic source (V) such as a vibrator of any type or an impulsive source by transmission elements (10, 13). The seismic source is coupled with coupling device (1) by fast locking means (18, 19). Coupling devices (1) can be preinstalled at a plurality of prepared activation locations above the formation to be monitored. Seismic monitoring operations can be carried out by moving at least one seismic source successively between the different locations where coupling devices (1) are installed.

Abstract: A hydrophone which is automatically inhibited when the immersion depth exceeds a predetermined threshold by action, on the push element (7) of a switch (6), of a flexible wall that bends under the action of the outside pressure. The hydrophone comprises a tubular body (1) with two chambers (1a, 1b) separated by a partition (2). One of the chambers is closed by a flexible diaphragm (4). Switch (6) is fixed at the center of one of the chambers. Diaphragm (4) can push down on and actuate push element (7) by bending. The body can advantageously consist of two parts that can be screwed onto one another, which allows easier adjustment of the inhibition pressure. A pressure-sensitive reception unit (S) is arranged in the other chamber.

Abstract: Electromechanical device for generating elastic waves in a material medium such as the subsoil in a frequency range where the wavelengths of the waves generated are great in view of the dimensions of the device, and method for implementing it.

Abstract: A method and device for emitting radial seismic waves in a material medium by electromagnetic induction, used notably for generating seismic waves in cased or uncased wells or in a water mass is disclosed. Emission of radial waves is essentially obtained by radially expanding a metal tube (1) under the effect of a magnetic pressure generated by electromagnetic induction with elastic waves being created in the medium under the effect of this expansion. The magnetic pressure is obtained by connecting a coil (2) in line with the tube to a current generator (3). The winding pitch of coil (2) can be constant or variable. Tube (1) can for example be added into a well or hole or it can be a tube portion of a cased well.

Abstract: Hydrophone which is automatically inhibited when the immersion depth exceeds a predetermined threshold by action, on the push element (7) of a switch (6), of a flexible wall that bends under the action of the outside pressure.

Abstract: A device which picks up elastic waves, such as a geophone for example, in positions far from the natural operating position for which it is designed. The device comprises an electrodynamic pickup including a magnet (1), a moving coil (2) placed in the magnetic field, springs (4) suited to hold the coil in a well-centered static position when the axis thereof is parallel to a selected reference direction (horizontal or vertical, for example) and a current source which applies to the coil an electrical current which corrects any unbalance of the coil in relation to the static position thereof due to an inclination of the axis of the coil in relation to the reference direction. The current source may be for example a source of direct current (5) and a voltage divider (P) whose division factor depends on the angle between the axis of the pickup and a reference axis or a compensating device suited to minimize the distortion ratio of the geophone.

Abstract: Compact vibrator for emitting elastic waves in a material medium such as the subsoil. The vibrator comprises a baseplate (3) intended to be coupled in operation with a surface of this medium, an inertia mass (5) and at least a pair of electromechanical transducers (1, 2) comprising each one or more pillars (A, B) made for example of a piezoelectric or magnetostrictive material. Pillars (A) of first transducer (1) are interposed between baseplate (3) and a relay plate (4). Pillars (B) of the second transducer are interposed between relay plate (4) and inertia mass (5), on the same side of relay plate (4) as pillars (A) preferably, so that inertia mass (5) is positioned in the vicinity of baseplate (3), which contributes to the compactness and to the stability of the vibrator that can therefore be used on slightly sloping surfaces.

Abstract: Method and device for emitting radial seismic waves in a material medium by electromagnetic induction, used notably for generating seismic waves in cased or uncased wells or in a water mass.

Abstract: The present invention is a system permanently installing measuring sondes against the inner wall of a pipe (1) such as a well or a tube. Measuring sondes (8) are respectively associated with coupling devices (2) that are brought to their coupling points in the pipe by means of an elongate support element (3) such as a cable or a tube. Each coupling device (2) comprises a deformable element (6) made of a shape-memory alloy that is deformed in order to allow displacement thereof along the pipe, and that is brought back to its expanded (convex) shape for example by means of a hot fluid stream that is injected in the pipe by means of a pump (P). In this expanded position, it immobilizes coupling device (2) and presses the sonde (8) against pipe (1) while mechanically decoupling the sonde from support element (3). The support element may be withdrawn if not serving another purpose.

Abstract: A system intended for permanent installation of measuring sondes against the inner wall of a pipe (1) such as a well or a tube. Measuring sondes (7) are respectively associated with coupling devices (2) that are brought to their respective coupling points in the pipe by means of a tube (3) positioned by off-centering devices (4) for example. Each coupling device (2) comprises a flexible element (6) carrying sonde (7), that is deformed to a set back position where it is immobilized by a lock (9) so as to allow displacement thereof along pipe (1). In order to release flexible blades (6), a sufficient overpressure allowing to push back the piston of a jack (10) whose cylinder communicates at one end with the inside of pipe (1) is established. In this expanded position, it immobilizes coupling device (2) and presses sonde (7) against pipe (1) while mechanically decoupling it from tube (3). Tube (3) can possibly be withdrawn if it does not serve another purpose.

Abstract: A well tool in accordance with the invention comprises an attenuation device which attenuates tube waves associated with an elastic wave emission and/or reception set (1, 12). The attenuation device comprises a bubble generator (2) which releases into the well a gas not readily soluble in the well fluid, slightly overpressured in relation to the hydrostatic pressure, in the form of calibrated bubbles which greatly attenuate the parasitic tube waves. The attenuation device is placed above or below the elastic wave emission and/or reception set having a plurality of pickups whose signals are acquired by a local electronic module (14) and/or a source of elastic waves such as a vibrator. A bubble trap (17) is preferably associated with the bubble generator (2) in order to limit the volume of gas to be generated in situ. The invention is applicable to VSP type seismic prospecting and acoustic logging.

Abstract: The present invention relates to a method for the acquisition of signals during a well drilling operation, wherein the following stages are carried out: shakes are generated by means of a vibration source, the signals resulting from the shakes are detected by downhole and surface measuring means (23; 24) connected to a control unit (22), a code for synchronizing the signals acquired by the downhole (7) and surface means (23; 24) is emitted, the signals supplied by the downhole measuring means (7) are stored in a storage module (11), the signals contained in storage module (11) are collected at the surface, then processings are performed on the synchronized downhole and surface signals.