Abstract: A field detector (2) comprises a field-responsive element (10) which undergoes a dimensional change when exposed to a predetermined field; and an interferometric read-out arrangement arranged to detect the dimensional change of the field-responsive element. A light source (4) is arranged to provide a measurement beam reflected from the field-responsive element (10) and a reference beam not reflected from the field-responsive element (10), an optical detector (6) being disposed so as to detect at least part of an interference pattern produced by the measurement beam and the reference beam. The field-responsive element (10) has a shape comprising a curved surface and is constrained at least one edge (12) thereof such that the dimensional change causes the curved surface to be displaced in a direction which changes an optical path length of the measurement beam relative to the reference beam, thereby changing the interference pattern detected by said optical detector.

Abstract: A field detector (2) comprises a field-responsive element (10) which undergoes a dimensional change when exposed to a predetermined field; and an interferometric read-out arrangement arranged to detect the dimensional change of the field-responsive element. A light source (4) is arranged to provide a measurement beam reflected from the field-responsive element (10) and a reference beam not reflected from the field-responsive element (10), an optical detector (6) being disposed so as to detect at least part of an interference pattern produced by the measurement beam and the reference beam. The field-responsive element (10) has a shape comprising a curved surface and is constrained at least one edge (12) thereof such that the dimensional change causes the curved surface to be displaced in a direction which changes an optical path length of the measurement beam relative to the reference beam, thereby changing the interference pattern detected by said optical detector.

Abstract: The present invention relates to a displacement sensor device and the system including the device, wherein the device comprises a first at least partially transparent plane surface with a first diffraction pattern and a second plane surface comprising a second reflecting diffraction pattern. The diffractive patterns being adapted to diffract light within a chosen range of wavelengths, the second surface being positioned below and parallel to the first surface constituting a pair wherein said first and second diffractive patterns being essentially equal, the device also comprising displacement means for allowing a movement in a direction parallel to said surfaces, the device thus providing a movement sensitive diffraction pattern.

Abstract: The present invention relates to a displacement sensor device and the system including the device, wherein the device comprises a first at least partially transparent plane surface with a first diffraction pattern and a second plane surface comprising a second reflecting diffraction pattern. The diffractive patterns being adapted to diffract light within a chosen range of wavelengths, the second surface being positioned below and parallel to the first surface constituting a pair wherein said first and second diffractive patterns being essentially equal, the device also comprising displacement means for allowing a movement in a direction parallel to said surfaces, the device thus providing a movement sensitive diffraction pattern.

Abstract: The present invention relates to a displacement sensor device and the system including the device, wherein the device comprises a first at least partially transparent plane surface with a first diffraction pattern and a second plane surface comprising a second reflecting diffraction pattern. The diffractive patterns being adapted to diffract light within a chosen range of wavelengths, the second surface being positioned below and parallel to the first surface constituting a pair wherein said first and second diffractive patterns being essentially equal, the device also comprising displacement means for allowing a movement in a direction parallel to said surfaces, the device thus providing a movement sensitive diffraction pattern.

Abstract: The present invention relates to a displacement sensor device and the system including the device, wherein the device comprises a first at least partially transparent plane surface with a first diffraction pattern and a second plane surface comprising a second reflecting diffraction pattern. The diffractive patterns being adapted to diffract light within a chosen range of wavelengths, the second surface being positioned below and parallel to the first surface constituting a pair wherein said first and second diffractive patterns being essentially equal, the device also comprising displacement means for allowing u movement in a direction parallel to said surfaces, the device thus providing a movement sensitive diffraction pattern.

Abstract: Methods and apparatus for reducing the impact of guided (or “tube”) waves in permanently installed seismic systems are provided. By utilizing passive acoustic absorbers, the impact of tube waves may be reduced, leading to improved performance of permanently installed seismic systems that are installed onto production tubing when the well is completed.

Abstract: Methods and apparatus for reducing the impact of guided (or “tube”) waves in permanently installed seismic systems are provided. By utilizing passive acoustic absorbers, the impact of tube waves may be reduced, leading to improved performance of permanently installed seismic systems that are installed onto production tubing when the well is completed.

Abstract: Methods and apparatus for reducing the impact of guided (or “tube”) waves in permanently installed seismic systems. By utilizing passive acoustic absorbers, the impact of tube waves may be reduced, leading to improved performance of permanently installed seismic systems that are installed onto production tubing when the well is completed.

Abstract: Methods and apparatus for reducing the impact of guided (or “tube”) waves in permanently installed seismic systems are provided. By utilizing passive acoustic absorbers, the impact of tube waves may be reduced, leading to improved performance of permanently installed seismic systems that are installed onto production tubing when the well is completed.

Abstract: An acoustic sensor, such as a hydrophone, is deployable in a fluidic media having high temperature, high pressure, and/or potentially caustic chemicals. The hydrophone includes a housing filled with an internal fluid and containing a sensing mandrel. The sensing mandrel senses the acoustic pressure transmitted to the internal fluid through a diaphragm. The sensing mandrel preferably includes a polymer tubular mandrel having a coil of optical fiber wound and bonded to its outer surface. The sensing mandrel can be suspended within the housing instead of being rigidly attached thereto. To relieve pressure created by thermal expansion of the internal fluid, the flexible diaphragm, a filler member, a pressure compensator, or combinations thereof can be used. The filler member is mounted in the hydrophone and reduces the amount of internal fluid required in the housing. The compensator may be a bellows or a buffer tube.

Abstract: A clamp mechanism for actively coupling an in-well seismic station to the casing of a well is disclosed. The clamp mechanism is capable of associating a sensor to production tubing for deployment in the well and is capable of actively coupling the sensor to the casing of the well. The clamp mechanism includes a body capable of being coupled to the deployment member. A carrier mechanism is attached to the sensor and positions adjacent the body. A release mechanism releases the carrier mechanism when subjected to a predetermined pressure in the well or when subjected to fluid in the well for a predetermined amount of time. A biasing mechanism is disposed between the body and the carrier mechanism and displaces the carrier mechanism with attached sensor towards the surface of the casing when released. A guiding mechanism guides the displacement of the carrier mechanism towards the surface of the casing.

Abstract: Fiber optic particle detector for measurements in a fluid flow, comprising an optical fiber (2,3,12) being acoustically coupled to a mechanical element (11,13,14) adapted to be acoustically coupled to the flow, a fiber optic interferometer (54,56) and a light source (12,51,55) providing light in said optical fiber.

Abstract: A highly sensitive accelerometer for determining the acceleration of a structure includes a mass within a housing suspended by opposing support members. The support members are alternately wound around a pair of fixed mandrels and the mass in a push pull arrangement. At least a portion of one of the support members comprises a transducer capable measuring the displacement of the mass within the housing. An embodiment of the invention employs optical fiber coils as the support members for use in interferometric sensing processes. Arrays of such interferometer based accelerometers may be multiplexed using known techniques.

Abstract: The present invention generally relates to an apparatus and method for seismic monitoring. In one aspect, an apparatus for acoustically coupling a sensor mechanism to a surface in a wellbore is provided. The apparatus includes a mandrel disposable in a tubing string. The apparatus further includes a carrier member disposed on the mandrel, the carrier member axially adjustable relative to the mandrel. The apparatus also includes at least one sensor mounted on the carrier member, the at least one sensor connected to the surface of the well via a cable line and a deployment assembly disposed on the carrier member for coupling the at least one sensor to the surface of the well. In another aspect, a method for acoustically coupling a sensor mechanism to a surface of a wellbore is provided.

Abstract: A highly sensitive accelerometer for determining the acceleration of a structure includes a mass within a housing rotationally supported by a hinge and opposing support members. The support members are alternately wound around a fixed mandrel and the mass in a pendulum arrangement. At least a portion of one of the support members comprises a transducer capable measuring the rotation of the mass within the housing. An embodiment of the invention employs optical fiber coils as support members for use in interferometric sensing processes. Arrays of such interferometer based accelerometers maybe multiplexed using WDM or similar methods.

Abstract: A multiple component mechanism for housing one or more fiber optic based sensors and one or more fiber organizers and other devices for the sensors is disclosed. The mechanism includes a splice component and a sensor component, which are hermetically sealed. The sensor and splice components include substantially tubular bodies having lids welded to the ends. The fiber organizer and other devices are installed in the cylindrical splice component. The one or more sensors are installed in the tubular body of the sensor component with wedging devices. In one embodiment, the sensor component is acoustically decoupled from the splice component by a tube welded to the lids of the components. The tube communicates optical fiber from the fiber organizer to the one or more sensors.

Abstract: A highly sensitive accelerometer for determining the acceleration of a structure includes a mass within a housing suspended by opposing support members. The support members are alternately wound around a pair of fixed mandrels and the mass in a push pull arrangement. At least a portion of one of the support members comprises a transducer capable measuring the displacement of the mass within the housing. An embodiment of the invention employs optical fiber coils as the support members for use in interferometric sensing processes. Arrays of such interferometer based accelerometers may be multiplexed using known techniques.

Abstract: Methods and apparatus for reducing the coherence of an optical signal that is used to interrogate optical interferometric sensors are disclosed. The optical field phasor of the interrogation source is modulated in a controlled manner to produce a broadened optical source power spectrum at the output of the source unit. The output from the source unit is launched into an optical sensor network, comprising a multiple of optical pathways from its input to the detection unit, where pairs of optical pathways form sensor interferometers. A compensating interferometer with delay difference similar to the sensor delay difference may be arranged in a serially coupled manner with the optical sensor network, either before or after the network. The optical output power from the source unit may either be continuous or pulsed with a pulse duration similar to the sensor delay.

Abstract: The present invention generally relates to an apparatus and method for seismic monitoring. In one aspect, an apparatus for acoustically coupling a sensor mechanism to a surface in a wellbore is provided. The apparatus includes a mandrel disposable in a tubing string. The apparatus further includes a carrier member disposed on the mandrel, the carrier member axially adjustable relative to the mandrel. The apparatus also includes at least one sensor mounted on the carrier member, the at least one sensor connected to the surface of the well via a cable line and a deployment assembly disposed on the carrier member for coupling the at least one sensor to the surface of the well. In another aspect, a method for acoustically coupling a sensor mechanism to a surface of a wellbore is provided.