Abstract: An intrusion detection system for monitoring a premises includes at least one optical cable that houses at least one optical fiber and extends about the premises. Optical time domain reflectometry (OTDR) means is operably coupled to opposite first and second ends of the at least one optical fiber. The OTDR means includes first signal processing circuitry that analyzes the backscatter signal received via the first end of the at least one optical fiber in order to detect an intrusion of the premises, and second signal processing circuitry that analyzes the backscatter signal received via the second end of the at least one optical fiber in order to detect an intrusion of the premises. The redundancy of intrusions decisions made by the first and second signal processing circuitry can be verified.

Abstract: A seismic acquisition system includes a distributed optical sensor (having an optical fiber) and an interrogation subsystem configured to generate a light signal to emit into the optical fiber. The interrogation subsystem receives, from the distributed optical sensor, backscattered light responsive to the emitted light signal, wherein the backscattered light is affected by one or both of seismic signals reflected from a subterranean structure and noise. Output data corresponding to the backscattered light is provided to a processing subsystem to determine a characteristic of the subterranean structure.

Abstract: Disclosed are a system, apparatus, and method for optical fiber well deployment in seismic optical surveying. Embodiments of this disclosure may include methods of deploying a spooled optical fiber distributed sensor into the wellbore integrated in a ballast or weight for a seismic optic tool, to achieve deployment of a lightweight disposable fiber optic cable against the wellbore walls via gravity. The method may further include unspooling the spooled optical fiber distributed sensor and using the optical fiber as a distributed seismic receiver. Once the fiber optic distributed sensor is deployed according to methods of the present disclosure, surveys may be obtained and processed by various methods.

Abstract: A method of detecting seismic waves traveling through a subsurface formation includes lowering a cable into a borehole in the subsurface formation, the cable having at least one optical fiber associated therewith, and causing descent of a remote end of the cable to be arrested. The method further includes feeding a further length of the cable into the borehole such that the cable is slack and in contact with at least part of a wall of the borehole, and using an interrogator coupled to the at least one optical fiber to detect seismic waves traveling through the subsurface formation and into the cable.

Abstract: A method for measuring Brillouin backscattering from an optical fibre, comprising mixing backscattered light received from the optical fibre and having a Brillouin frequency f?(t) with coherent light at a frequency f i in an optical detector to produce an electrical signal with a difference frequency ?F(t)=f?(t)?f15 and directly digitising the electrical signal using an analog-to-digital converter to generate a sequence of samples representing the electrical signal, the samples then being processed to determine one or more properties of the Brillouin spectral line. The difference frequency may be further reduced by an additional frequency mixing stage to allow digitisation at a lower sampling rate.

Abstract: A method and system for acoustic monitoring using a fiber optic cable. The optical fiber is used as a distributed interferometer that may be used to monitor activity, such as activity with respect to a conduit, wellbore or reservoir. The distributed interferometric monitoring provides for accurate detection of acoustic occurrences along the fiber optic cable and these acoustic occurrences may include fluid flow in a pipeline or wellbore, processes taking place in a wellbore or pipeline, fracturing, gravel packing, production logging and/or the like.

Abstract: A fiber optic distributed vibration system for detecting seismic signals in an earth formation is provided. The system includes a fiber optic cable deployed in a borehole that extends into the earth formation and which is configured to react along its length to a seismic wave incident on the fiber optic cable from outside the borehole. An optical source launches an optical signal into the fiber optic cable while the seismic wave is incident thereon. A receiver detects coherent Rayleigh noise (CRN) produced in response to the optical signal. A processing circuit processes the detected CRN signal to determine characteristics of the earth formation.

Abstract: A fiber optic sensing tool assembly is deployed in a wellbore that penetrates a hydrocarbon-bearing formation of interest to measure fluid composition and other fluid characteristics. This measurement is implemented by deploying the tool in a region in which there is substantially no fluid flow and by heating the tool through an optical delivery system. Parameters of the fluid are monitored as a function of the heating of the tool to derive information that is indicative of fluid composition and other fluid characteristics.

Abstract: A fiber optic distributed vibration system for detecting seismic signals in an earth formation is provided. The system includes a fiber optic cable deployed in a borehole that extends into the earth formation and which is configured to react along its length to a seismic wave incident on the fiber optic cable from outside the borehole. An optical source launches an optical signal into the fiber optic cable while the seismic wave is incident thereon. A receiver detects coherent Rayleigh noise (CRN) produced in response to the optical signal. A processing circuit processes the detected CRN signal to determine characteristics of the earth formation.

Abstract: Fiber optic monitoring of dimensional changes within a subterranean formation includes deploying a fiber optic cable assembly in a wellbore and attaching the cable assembly to first and second attachment points on either side of the formation. A surface fiber optic measurement system measures changes in the optical path length between the attachment points of the fiber optic cable assembly. The changes in optical path length are directly indicative of dimensional changes within the formation.

Abstract: A distributed acoustic wave detection system and method is provided. The system may include a fiber optic cable deployed in a well and configured to react to pressure changes resulting from a propagating acoustic wave and an optical source configured to launch interrogating pulses into the fiber optic cable. In addition, the system may include a receiver configured to detect coherent Rayleigh noise produced in response to the interrogating pulses. The CRN signal may be use to track the propagation of the acoustic wave in the well.

Abstract: To provide a polarization-diverse, heterodyne optical receiving system, a light signal is transmitted into an optical fiber having a plurality of optical sensors that are distinguishable using a multiplexing arrangement. A return light signal from the optical fiber is mixed with an optical local oscillator light signal, where the mixing outputs plural output signal portions having different polarizations. A birefringence of a particular optical sensor is determined based on the plural signal portions.

Abstract: Acoustic monitoring is carried out using a fiber optic cable. Coherent Rayleigh noise generated by the transmission of a coherent beam of radiation through the fiber optic cable is detected, a phase of the coherent Rayleigh noise is measured and the measured phase is processed to identify an acoustic occurrence along the fiber optic cable. In certain aspects, an optical fiber serves as a distributed interferometer that may be used to monitor a conduit, wellbore or reservoir. The distributed interferometric monitoring provides for accurate detection of acoustic occurrences along the fiber optic cable and these acoustic occurrences may include fluid flow in a pipeline or wellbore, processes taking place in a wellbore or pipeline, fracturing, gravel packing, or production logging.

Abstract: A tilt meter includes a housing structure defining an inner chamber sealed from an environment outside the housing structure. First and second optical fiber sections are provided in the inner chamber. The second optical fiber section is optically coupled to the first optical fiber section, with the second optical fiber section rotated azimuthally with respect to the first optical fiber section. The first and second optical fiber sections are arranged to receive light transmitted from a remote light source, and a tilt of the housing structure induces a differential pressure within the inner chamber to be detected by the first and second optical fiber sections.

Abstract: Acoustic monitoring is carried out using a fiber optic cable. Coherent Rayleigh noise generated by the transmission of a coherent beam of radiation through the fiber optic cable is detected, a phase of the coherent Rayleigh noise is measured and the measured phase is processed to identify an acoustic occurrence along the fiber optic cable. In certain aspects, an optical fiber serves as a distributed interferometer that may be used to monitor a conduit, wellbore or reservoir. The distributed interferometric monitoring provides for accurate detection of acoustic occurrences along the fiber optic cable and these acoustic occurrences may include fluid flow in a pipeline or wellbore, processes taking place in a wellbore or pipeline, fracturing, gravel packing, or production logging.

Abstract: Methods and apparatus for facilitating optical communications and sensing, with downhole optical or other sensors, in high temperature oilfield applications. The apparatus can include a downhole telemetry cartridge for downhole use at temperatures in excess of about 115 degrees Celsius. The apparatus can also include a downhole light source optically connected to the telemetry cartridge. The light source may include at least one remotely pumped laser optically connected to a surface pump laser via optical fiber(s). The remotely pumped laser may drive the downhole optical or other sensors for their operations.

Abstract: Acoustic monitoring is carried out using a fiber optic cable. Coherent Rayleigh noise generated by the transmission of a coherent beam of radiation through the fiber optic cable is detected, a phase of the coherent Rayleigh noise is measured and the measured phase is processed to identify an acoustic occurrence along the fiber optic cable. In certain aspects an optical fiber serves as a distributed interferometer that may be used to monitor a conduit, wellbore or reservoir. The distributed interferometric monitoring provides for accurate detection of acoustic occurrences along the fiber optic cable and these acoustic occurrences may include fluid flow in a pipeline or wellbore, processes taking place in a wellbore or pipeline, fracturing, gravel packing, or production logging.

Abstract: A method for measuring Brillouin backscattering from an optical fiber, includes frequency mixing a first signal with a frequency representative of the Brillouin frequency shift in backscattered light received from a deployed optical fiber with a second signal at a frequency that varies in time in the same manner as a Brillouin shift previously measured from the fiber to produce a difference signal with a difference frequency that has a nominally constant value corresponding to the situation where the received light has a Brillouin shift that matches the previously measured shift. The difference signal is acquired and processed to determine properties of the Brillouin shift and corresponding physical parameters producing the shift. The frequency mixing can be carried out optically or electrically. Techniques for acquisition of the difference signal include the use of parallel frequency measurement channels and fast rate digital sampling.

Abstract: A seismic acquisition system includes a distributed optical sensor (having an optical fiber) and an interrogation subsystem configured to generate a light signal to emit into the optical fiber. The interrogation subsystem receives, from the distributed optical sensor, backscattered light responsive to the emitted light signal, wherein the backscattered light is affected by one or both of seismic signals reflected from a subterranean structure and noise. Output data corresponding to the backscattered light is provided to a processing subsystem to determine a characteristic of the subterranean structure.

Abstract: To measure a characteristic of a multimode optical fiber, a light pulse source produces a light pulse for transmission into the multimode optical fiber. A spatial filter passes a portion of Brillouin backscattered light from the multimode optical fiber that is responsive to the light pulse. Optical detection equipment detects the portion of the Brillouin backscattered light passed by the spatial filter.