Measuring and testing – Fluid pressure gauge – Photoelectric
Reexamination Certificate
1999-06-25
2002-09-17
Oen, William (Department: 2855)
Measuring and testing
Fluid pressure gauge
Photoelectric
C250S227190, C250S231190
Reexamination Certificate
active
06450037
ABSTRACT:
TECHNICAL FIELD
This invention relates to sensing pressure around pipes and more particularly to a non-intrusive fiber pressure sensor for measuring unsteady pressures within a pipe.
BACKGROUND ART
It is known in the oil and gas industry that the measurement of fluid pressure in a down-hole pipe is useful to exploration and production of oil and gas. However, typical pressure sensors require that a hole be drilled in the pipe to port the pressure to the sensor, or that the sensor or portion thereof be deployed in the pipe. Drilling holes in the pipes can be costly and add failure modes to the system. Accordingly, it would be desirable to measure pressure in a pipe in a non-invasive manner.
SUMMARY OF THE INVENTION
Objects of the present invention include provision of a non-intrusive pressure sensor for measuring unsteady pressure within pipes.
According to the present invention, a pressure sensor for measuring unsteady (ac, dynamic or time varying) pressure at least one axial location along a pipe, comprises an optical fiber wrapped around the circumference of the pipe.
According still further to the present invention, a length of said optical fiber changes when the pressure to be measured changes. According still further to the present invention, a reflective element is disposed within said fiber having a reflection wavelength related the pressure.
The present invention provides a significant improvement over the prior art by providing a non-intrusive pressure sensor for the measurement of unsteady pressure in a pipe using fiber optic sensing. Also, the present invention eliminates the need for any electronic components down-hole, thereby improving reliability of the measurement. Still further, the present invention is inherently safe and explosion proof as compared to electrical systems. The present invention may also provide circumferentially averaged pressure and/or axially averaged unsteady pressure over a predetermined axial length of the pipe. Circumferential averaging naturally filters out pressure disturbances such as those associated with transverse pipe vibrations, flow noise, and higher dimensional acoustic oscillations. This attribute is useful for measuring propagating one-dimensional acoustic waves. Thus, the present invention enables real time unsteady pressure measurement for oil and gas exploration and production or for other applications where a fluid (liquid or gas) is flowing in a pipe or conduit.
The foregoing and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of exemplary embodiments thereof.
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“Noise and Vibration Control Engineering Principles and Applications”, Leo L. Beranek and Istvan L. Ver, A Wiley Interscience Publication, pp. 537-541, No date.
Davis Allen R.
Faustino John M.
Gysling Daniel L.
McGuinn Rebecca S.
Winston Charles R.
CiDRA Corporation
Oen William
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