Schlumberger Technology Corporation

Stewart Hughes Limited

Maxwell Richard Hadley

Arthur H Hartog

Yuehua Chen

Dylan H Davies

Dominic Joseph Brady

James McInnes

Ian C Cheeseman

Timothy Jeffreys

Richard P Dudley

A distributed temperature sensing (DTS) system is operated to detect fluid leaks from a pipeline. The DTS system obtains temperature profiles from a sensing element that is deployed along the pipeline, where the profiles are temperature measurements as a function of distance. The temperature profiles are examined to identify the presence of a characteristic temperature signature expected to occur in the presence of a leak. A leak condition signal for a particular distance point is generated based on a determination that the energy of the temperature signal exceeds a threshold energy for that point.

Detection of leaks from a pipeline using a distributed temperature sensor

A distributed temperature sensing (DTS) system is connected to a buried fiber optic cable that is used to monitor a structure. The DTS system is operated to obtain temperature measurements along the length of the fiber cable. The temperature measurements are then used to calculate a measure of diurnal temperature variability at each point along the cable. This calculation is used to identify points at which the diurnal temperature variability changes rapidly over a short length of the cable. These points can be identified with features along the cable, such as splice chambers, where the cable burial conditions change. The known geographic location of these features can then be identified with specific distances along the fiber.

Identification of features on an optical fiber using a distributed temperature sensor

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.

Polarization-diverse, heterodyne optical receiving system

A technique that is usable with a well includes changing the temperature of a local environment of a distributed temperature sensor, which is deployed in a region of the well and using the sensor to acquire measurements of a temperature versus depth profile. The region contains at least two different well fluid layers, and the technique includes determining the depth of a boundary of at least one of the well fluid layers based at least in part on a response of the temperature versus depth profile to the changing of the temperature.

Fluid level indication system and technique

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.

Light source stabilisation

A method and apparatus for use when measuring pressure in hydrocarbon wells. A sensor, an interferometric optical pressure transducer, at the end of a fibre optic line is illuminated by broadband light pulses. Measuring equipment output drives a display indicating the pressure at the sensor. The transducer is modelled by subjecting it to known pressures. The measuring equipment is modelled by applying test signals. The models are combined and a display output C is assumed. A mathematical model is used to calculate an estimation B of the actual output A from the sensor. B is compared with A and the value of C changed until the closest match is found between A and B. This value of C is taken as the output representing the pressure at the sensor. Different models and compensation factors allow for interchange of sensors and sensor types and measuring equipment and measuring equipment types.

Sensor response with compensation for sensor type and measuring equipment type

Optical tracker system for determining the position of a rotating body

Variable gain amplifier providing substantially uniform magnitude output

Rotor blade tracking devices

This invention relates to apparatus for producing a periodic output signal having a predetermined period ratio (a/b) relative to a periodic input signal. Signals from a tachometer on a gearbox are received by a counter timer unit, the counter timer unit evaluates the number of clock pulses k.sup.o received from a clock within each period of the tacho signal. A control unit receives values of k.sup.o from the counter timer and employs an algorithm based on the following equation to calculate a count value n.sup.o to be loaded into a register for the next tacho period. ##EQU1## where dK represents k.sup.-1 -k.sup.o. An accumulator is connected via an adder to the register and at receipt of each clock pulse from the clock adds the count stored in register into the accumulator. An output is produced on line when the accumulator overflows.

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Lyndhurst, United Kingdom

Maxwell Richard Hadley