CN-121994755-A - Array type round table type optical fiber probe downhole multiphase flow gas holding rate sensor

Abstract

The invention relates to the technical field of optical fiber sensing and discloses an array type circular truncated cone type optical fiber probe downhole multiphase flow gas holdup sensor, which comprises an array type optical fiber probe formed by a plurality of optical fiber probes, wherein the array type optical fiber probes are distributed in a downhole measuring pipeline in a cross-section manner along the pipeline; wherein each optical fiber probe is formed by grinding a tip portion of a single-mode optical fiber so that the tip portion has a truncated cone-shaped structure. Compared with the existing optical fiber sensor, the array type optical fiber probe downhole multiphase flow gas holding rate sensor has higher gas holding rate measurement precision and lower cost.

Inventors

• WANG RUOHUI
• JI HAOZHE
• HE MINGHUI
• QIAO XUEGUANG

Assignees

• 西北大学

Dates

Publication Date

20260508

Application Date

20260318

Claims (10)

1. 1. The array type round table type optical fiber probe downhole multiphase flow gas holding rate sensor is characterized by comprising an array type optical fiber probe formed by a plurality of optical fiber probes, wherein the array type optical fiber probes are symmetrically distributed in a downhole measurement pipeline along the cross section of the pipeline; wherein each optical fiber probe is formed by grinding a tip portion of a single-mode optical fiber so that the tip portion has a truncated cone-shaped structure.
2. 2. The downhole multiphase flow gas holdup sensor of array circular truncated cone type optical fiber probes according to claim 1, wherein the inclination angle of the circular truncated cone portion in each optical fiber probe is larger than or equal to 80 degrees, the top end plane diameter of the circular truncated cone portion is 50-60 μm, and the height of the circular truncated cone portion is larger than or equal to 350 μm.
3. 3. The array type circular truncated cone type optical fiber probe downhole multiphase flow gas holdup sensor of claim 2, wherein the single mode optical fiber has a length of 5mm and a diameter of 125 μm, and wherein the fiber core has a diameter of 9 μm.
4. 4. The downhole multiphase flow gas holdup sensor of array circular truncated cone type optical fiber probes according to claim 1, wherein each optical fiber probe is coaxially packaged by a capillary steel tube, wherein the length of the capillary steel tube is 3cm, and the inner diameter of the capillary steel tube is 130 μm.
5. 5. The downhole multiphase flow gas holdup sensor of arrayed circular-table type optical fiber probe of claim 4, wherein the capillary tube and the optical fiber probe are cured by 353ND glue to form a sealing layer.
6. 6. The array bench type fiber optic probe downhole multiphase flow gas holdup sensor of claim 5, wherein the thickness of the sealing layer is greater than or equal to 0.05mm.
7. 7. The array type round table type optical fiber probe downhole multiphase flow gas holdup sensor of claim 1, wherein each optical fiber probe is fixed on an array base and fixed inside a downhole measuring pipeline through an M3 countersunk bolt.
8. 8. The array circular truncated cone type optical fiber probe downhole multiphase flow gas holdup sensor of any one of claims 1 to 7, wherein the optical fiber probes are 4 for gas holdup measurement of downhole measurement pipe with pipe inner diameter of 25.4 mm.
9. 9. The array type round bench type optical fiber probe downhole multiphase flow gas holdup sensor of claim 1, wherein the sensor further comprises a light source module and an array type intensity demodulation module; The light source module comprises a driving power supply, a photodiode, a coupler and a plurality of optical fiber circulators, and the arrayed intensity demodulation module comprises a plurality of photoelectric detectors, an IV conversion circuit, a multichannel AD synchronous sampling module, an FPGA development board and an upper computer, wherein the optical fiber circulators and the photoelectric detectors are respectively in one-to-one correspondence with the optical fiber probes; The photoelectric detector converts the reflected light intensity signals of the corresponding optical fiber probes into current signals, the IV conversion circuit converts the current signals of all the optical fiber probes into voltage signals, and the current signals are sampled by the multichannel AD synchronous sampling module, and then the FPGA development board performs gas holding rate measurement and sends the gas holding rate measurement to the upper computer for display.
10. 10. The downhole multiphase flow gas holdup sensor of array circular truncated cone type optical fiber probes according to claim 9, wherein the FPGA development board judges abnormal values of the sampled signals of each optical fiber probe sampled by the multi-channel AD synchronous sampling module, adjusts weight values of corresponding sampled signals if a single sampled signal deviates from a preset percentage of average values of other sampled signals, and measures gas holdup by weighting and fusing all sampled signals.

Description

Array type round table type optical fiber probe downhole multiphase flow gas holding rate sensor Technical Field The invention relates to the technical field of optical fiber sensing, in particular to an array type circular truncated cone type optical fiber probe downhole multiphase flow gas holding rate sensor. Background Currently, water injection exploitation of oil fields has become a mainstream exploitation mode of most oil fields, and along with the continuous advancement of exploitation process, a large number of oil fields gradually enter the middle and later stages of exploitation, and the oil reservoir condition is increasingly complex. The oil-gas-water multiphase flow is used as a typical fluid form in the development process of an oil field, is widely used in produced liquid and transport pipelines of the oil field, and parameters such as phase distribution, gas holding rate, water content and the like directly reflect the development state of the oil reservoir, fluid flow characteristics and exploitation efficiency, and are core basis for guiding the production-increasing operations such as refined water injection, profile control, water shutoff and the like of the oil field, optimizing exploitation schemes, reducing production cost and improving oil recovery efficiency. In the oil-gas-water multiphase flow detection, ‌ gas holding rate refers to the volume proportion of gas phase in mixed fluid, and is a core parameter for representing multiphase flow characteristics. The severe environment of high temperature and high pressure in the pit has very high requirements on the precision and stability of the measuring instrument. The conventional gas retention rate measurement methods (such as an image detection method, a rapid valve closing method, an ultrasonic measurement method and a tomography method) have obvious limitations in underground high-temperature, high-pressure and strong electromagnetic interference environments, and are difficult to meet actual measurement requirements. In contrast, the optical fiber probe sensor is more suitable for underground gas holding rate measurement due to the advantages of high sensitivity, high temperature and high pressure resistance, electromagnetic interference resistance and the like. The optical fiber probe sensor has the advantages that the measuring mode is contact type, the phase state of a contact medium can be directly distinguished, the flow pattern of the cross section of a pipeline can be inverted through array arrangement, meanwhile, the interference of the micron-sized optical fiber on the fluid flow is negligible, and the accuracy of a measuring result is further ensured. The core principle of the detection of the gas holding rate of various optical fiber probe sensors is basically consistent, and the identification and judgment of the fluid phase state are realized through an effective reflecting surface formed by the contact of the sensitive head fiber core and a detected medium based on the Fresnel reflection effect. Common fiber optic probe sensors include sapphire fiber optic probes and tapered fiber optic probes. The sapphire optical fiber probe relies on refractive index characteristics of a sapphire material, so that the reflected light signal intensity after medium contact can be enhanced to a certain extent, but the processing technology of the sapphire material is complex, the preparation cost is high, large-scale industrial application is difficult to realize, the optical coupling efficiency of a sapphire sensitive head and a conventional quartz single-mode optical fiber is low, light energy loss is easy to cause, and the accuracy of a measurement signal is further affected. The conical optical fiber probe has certain bubble puncture efficiency by virtue of the conical tip structure, but the diameter of the fiber core is excessively reduced in the preparation process, so that the effective reflection area is greatly reduced, the intensity of a reflected light signal is obviously reduced, the reflected light signal is extremely easy to be submerged by system noise, gas phase leakage judgment is further caused, and the measurement accuracy of the gas holding rate is seriously reduced. Disclosure of Invention The invention aims to provide an array type round table type optical fiber probe downhole multiphase flow gas holding rate sensor, which can solve the problems of high manufacturing cost and low measuring precision of the conventional optical fiber probe sensor. In order to solve the technical problems, the embodiment of the invention provides an array type round table type optical fiber probe downhole multiphase flow gas-holding rate sensor, which is characterized by comprising an array type optical fiber probe formed by a plurality of optical fiber probes, wherein the array type optical fiber probes are symmetrically distributed along the cross section of a pipeline in a downhole measurement pipeline; wherein each optical