A secondary silver-coated fiber grating gas sensor

Abstract

The invention discloses a twice silver plated fiber bragg grating gas sensor. A separation cavity is connected with a sensor fixing flange at the upper end through a flange fixing thread; a small hole is formed in the center of the sensor fixing flange; an optic fiber passes through the small hole; a silver plated FBG gas sensitive element is arranged at the lower end of the optic fiber; a streamline protective shell is arranged outside the silver plated FBG gas sensitive element; an equidistant spiral guide slot is engraved in the inner wall of the separation cavity; the bottom of the separation cavity is connected with a device with a spiral diversion hole through a fixed thread; the screw pitch of the device with the spiral diversion hole is same as that of the spiral guide slot in the separation cavity. In order to ensure the effective contact between the gas in well fluid and a gas sensitive film plating layer and correctly measure the concentration of the underground gas, oil-gas separation is carried out at first and then the gas content is detected through plating a sensitive material Ag film on a fiber bragg grating (FBG). By adopting a rotary separation principle and separating the gas and liquid phases by means of centrifugal force, the twice silver plated fiber bragg grating gas sensor has the advantages of being reasonable in design, simple in structure, convenient to operate, high in sensitivity and suitable for the real-time detection of low-concentration H2S gas and environment temperature in oil gas wells.

Description

technical field [0001] The invention belongs to the technical field of optical fiber sensing, and in particular relates to a secondary silver-coated optical fiber grating gas sensor for detecting low-concentration hydrogen sulfide gas in oil and gas wells. Background technique [0002] With the development of the petrochemical industry, the types and ranges of flammable, explosive and toxic gases have increased. Once these gases leak during production, transportation, and use, it will cause poisoning, fire and even explosion accidents, seriously endangering people's lives and property safety. Blowout accidents of sour gas wells accompanied by hydrogen sulfide (H 2 The release or combustion of toxic gases such as S) will cause serious casualties, property losses and affect the environment; the detection of hydrogen sulfide gas downhole in oil and gas wells is a difficult problem in the field of oil and gas field exploration and development. At present, the hydrogen sulfide ...

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Problems solved by technology

[0003] In order to overcome the defect that existing traditional hydrogen sulfide gas sensors cannot be laid downhole, the object of the present invention is to propose a secondary silver-plated fiber grating gas sensor: in order to allow the gas in the well fluid to effectively contact the gas-sensitive film coating, To accurately measure the concentration of downhole gas, oil and gas separation must be carried out first. On this basis, the gas content is detected by coating the sensitive material Ag film on the fiber bragg grating (FBG)

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