Apparel – Nether garments – Bifurcated
Reexamination Certificate
1999-03-22
2001-05-22
Epps, Georgia (Department: 2873)
Apparel
Nether garments
Bifurcated
C250S254000
Reexamination Certificate
active
06233746
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a fiber optic transducer for combined pressure, temperature, and strain measurements, and in particular to multiple sensors arranged in a convoy fashion to provide multiplexed measurements in a downhole environment.
BACKGROUND OF THE INVENTION
Sensors have been used in downhole environments to detect and measure pressure, strain, temperature and other well characteristics that indicate the production capability of the well. These sensors have typically been constructed using piezoelectric and ferroelectric components that are reactive to pressure and temperature characteristics, and have been within the bore of downhole tools to monitor these conditions. Once the measurements are completed, then the downhole tools are retrieved and the data retrieved for analysis of the downhole conditions. This process of retrieving data is time consuming and also requires stopping well production. This time translates into lost profits and increased operational costs of the well.
Pressure, temperature, flow, and water cut are fundamental measurements for the management of producing wells. In deepwater operations and high producing horizontal/multilateral wells, these measurements take on an increased significance. Oil producers have been incurring costs to monitor wells in these complex oil well environments using antiquated technology.
For example, sensors have been developed and deployed to remain downhole to monitor conditions in producing wells. These sensors, however, are single-point electronic sensors that are very expensive and have a mean-time-to-failure much lower than optimal. As a result, and despite the full complement of sensors, the majority of a well structure after a short time is monitored by less than the complement of sensors.
As an advance in sensor technology, Bragg grating technology has emerged as an alternative to single-point sensors due to its fiber optic sensing transducer capability. Due to their narrowband wavelength reflection, they can be multiplexed in a fiber optic network. Nevertheless, such sensors can be susceptible to the hostile downhole environments, and, as a consequence, fail to operate for a time far shorter than the producing life of a well. Thus, a need exists for simplified optical sensors that have a robust housing to withstand the large magnitude forces downhole while still sufficiently yielding to reliably sense the environment conditions.
SUMMARY OF THE INVENTION
Accordingly, provided is an optic sensor for use in a well. The sensors can be configured to sense downhole temperature conditions, pressure conditions, or stress conditions, either individually or in combination. The optic sensor has a sensor housing that defines a chamber. The sensor housing also defines a region that is responsive to an external force such as pressure, stress, or temperature. An optic fiber extends through the housing. The optic fiber has a dielectric boundary that resides within the housing chamber, and has a refractive index variation that provides maximum reflectivity at a central reflectivity wavelength, the central reflectivity wavelength correspondingly shifting with respect to an expansion or contraction of the region.
In a further aspect of the invention, the optic fiber has a second dielectric boundary spaced apart from the first dielectric boundary. The second dielectric boundary is within the chamber and has a refractive index variation that provides maximum reflectivity at a central reflectivity wavelength sufficiently dissimilar to the first dielectric boundary. The second dielectric boundary floats in the cavity such that the second dielectric boundary is responsive to a temperature change within the sensor housing.
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Epps Georgia
Halliburton Energy Service,s Inc.
Herman Paul I.
Murphy James J.
Seyrafi Saeed
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