Schlumberger Technology Corporation

Yuehua Chen

Arthur H Hartog

Colin Allan Wilson

Maxwell Richard Hadley

Rogerio Tadeu Ramos

Robert J Schroeder

Ian Atkinson

Jeffrey A Tarvin

Franck Monmont

Cong Wang

James McInnes

Timothy Jeffreys

A technique includes acquiring dry condition and wet measurements using an optical spectrometer for a plurality of lamp intensities. The technique includes determining candidate maximum optical densities as a function of the lamp intensities based at least in part on a reference measurement that is acquired by the spectrometer, the reference measurement and does not vary with respect to the lamp intensities. The technique includes determining an optical density linear dynamic range based at least in part on the candidate maximum optical densities.

Determining an optical density linear dynamic range for an optical spectrometer

A multiple sensor fiber optic sensing system includes an optical fiber having at least first fiber optic sensors and second fiber optic sensors deployed along its length. In response to an interrogating pulse, the first fiber optic sensors generate responses in a first optical spectrum window, and the second fiber optic sensors generate responses in a second, different optical spectrum window. The responses in the first optical spectrum window are measured in a first optical spectrum channel, and the responses in the second optical spectrum window are measure in a second, different optical spectrum channel and provide simultaneous indications of one or more parameters, such as temperature and pressure, in the environment in which the sensors are deployed.

Multiple spectrum channel, multiple sensor fiber optic monitoring system

A telemetry apparatus and method for communicating data from a down-hole location through a borehole to the surface is described including a light source, an optical fiber being placed along the length of the wellbore and receiving light from the light source, a transducer located such as to produce a force field (e.g. a magnetic field) across the optical fiber and its protective hull without mechanical penetration of the hull at the down-hole location, one or more sensors for measuring down-hole conditions and/or parameters, a controller to provide a modulated signal to the magnetic field generator, said modulated signal being under operating conditions representative of measurements by the one or more sensors, and an optical detector adapted to detect changes in the light intensity or polarization of light passing through the fiber.

Borehole telemetry system

A sensing system including a sensor having an enclosure that defines a chamber, a fiber optic segment extending from outside the enclosure into the chamber, and a sequence of optical processing elements within the chamber. The elements include a fiber Bragg grating, a polarizer, a side hole fiber, and a mirror. A light source is arranged to direct light to the sensor(s). A spectral analyzer is arranged to detect light reflected back from the sensor(s). The fiber Bragg grating substantially reflects a first spectral envelope while transmitting the remainder of the optical spectrum to the polarizer and side hole fiber. The polarizer, side hole fiber, and mirror cooperate to return an optical signal within a second spectral envelope. The characteristic wavelength of a peak in the first spectral envelope is highly sensitive to temperature and relatively weakly sensitive to pressure. The period of the optical signal within the second spectral envelope is highly sensitive to pressure and relatively weakly sensitive to temperature. The spectral analyzer measures these spectral components to simultaneously derive a measure of temperature and pressure that effectively compensates for temperature-pressure cross-sensitivity of the sensor(s).

Fiber optic temperature and pressure sensor and system incorporating same

A sensing system including a sensor having an enclosure that defines a chamber, a fiber optic segment extending from outside the enclosure into the chamber, and a sequence of optical processing elements within the chamber. The elements include a fiber Bragg grating, a polarizer, a side hole fiber, and a mirror. A light source is arranged to direct light to the sensor(s). A spectral analyzer is arranged to detect light reflected back from the sensor(s). The fiber Bragg grating substantially reflects a first spectral envelope while transmitting the remainder of the optical spectrum to the polarizer and side hole fiber. The polarizer, side hole fiber, and mirror cooperate to return an optical signal within a second spectra! envelope. The characteristic wavelength of a peak in the first spectral envelope is highly sensitive to temperature and relatively weakly sensitive to pressure. The period of the optical signal within the second spectral envelope is highly sensitive to pressure and relatively weakly sensitive to temperature. The spectral analyzer measures these spectral components to simultaneously derive a measure of temperature and pressure that effectively compensates for temperature-pressure cross-sensitivity of the sensor(s).

An optical fiber splice protector is provided which includes a first tube being substantially hollow and being locatable along a portion of the length of at least one optical fiber, the portion including a bare optical fiber section of the optical fiber. A longitudinal support is also locatable along the portion of the length of the optical fiber that includes the bare optical fiber splice section of the optical fiber, the longitudinal support being enclosable by the first tube along the length of the optical fiber. The first tube is of high temperature resistant material that is resistant to temperatures above 125 degrees Celsius.

Optical fibre splice protector

A sensing fibre for use in a distributed temperature sensing system comprises an optical fibre to be deployed in a measurement region in which a temperature measurement is to be made, which incorporates a reflective element, such as a join between portions of fibre, and a coiled fibre portion positioned adjacent a distal side of the reflective element, the coiled fibre portion contributing substantially nothing to the spatial extent of the optical fibre when deployed. In use, the effect of any forward propagating light incident on the reflective element that is returned for detection by the system, and which saturates the detector, can be eliminated by removing the part of the detected signal that corresponds to the coiled portion, after which the detector will have recovered. The remaining parts of the signal can be used to derive the distributed temperature profile since these parts represent the whole extent of the sensing fibre owing to the lack of spatial extent of the coil. Coils can be provided on both sides of the reflective element for double-ended temperature sensing techniques.

Apparatus and methods for distributed temperature sensing

A method and apparatus for receiving measurements from an interferometer transducer () uses a broad band light beam (A), reflected from the transducer (), and compares it with the amplitudes of narrow band beams, derived from the reflected broad band light beam (A), by filters (A-D) on different frequencies. The narrow band light beams and the broad band light beam (A) are measured on photo detectors (A,B-E). Microprocessor () compares outputs of the photo detectors to interpret phase differences between signals () from the narrow band beams. A periodically operable shutter and a single photo detector () can also be used. Other embodiments modulate () the light source () to produce very short broad band pulses of light () which are reflected from the transducer ().

Fibre-optic interferometric remote sensor

An apparatus for sensing data from a remote optical sensorhas its frequency stabilised by balancing the outputs of narrow band filter, spaced about a desired frequencypositioned at about the 3 db down pointsof a broad band light sourceusing voltage control, current control or temperature control to vary the frequency of the wide band light source. Difference between the outputs through the two narrow band filterscan be used to drive an amplifierto correct the frequency of the broad band light source. The outputs through the two narrow band filterscan be convertedto binary numbers and fed to a microprocessorwhich is used, via analog conversion, to drive the amplifier. The broad band light sourcecan be pulse modulatedto provide temporally separate light pulsesthrough each of the narrow band filtersmeasured at separate times. The corrective output to the amplifiercan be governed by a ratio between the outputs through the narrow band filtersrather than by a difference there between.

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Southampton, United Kingdom

Yuehua Chen