Fiber-optic vibration measurement system in multiphase flows with a method related to monitoring multiphase flows

Abstract

A vibration measurement system and relative method for monitoring multiphase flow in extraction wells or pipes, with reversible multi-dimensional fiber light analysis, comprising:\n•\tA multi-purpose sensing optical fiber;\n•\tA light source comprising a high-coherence laser that sends light pulses to be sent to the sensing fibers;\n•\tA photonic lantern with 3 or more single-mode optical fiber ports and a multi-purpose fiber port connected to the multi-purpose sensing fiber;\n •\tAn optical receiver, comprising a number of photodetectors equal to the number of ports A single-unit optical fiber negative lantern 1, each of which is connected to one of the single-mode ports.\n•\tSystem for processing output signals from the optical receiver,\n\nThe light source is connected to one of the single-mode optical fiber fibers and the other single-mode port is connected to the optical receiver.\nAlso, a process for reconfiguring an optical reflection system that has been previously installed in a facility to be monitored is described.

Description

� Fiber-optic vibration measurement system in multiphase flows with a method related to monitoring multiphase flows� Summary of the invention A vibration measurement system and relative method for monitoring multiphase flow in extraction wells or pipes, with reversible multi-dimensional fiber light analysis, comprising: � Multi-purpose sensing optical fiber; � A light source consisting of a high-coherence laser that sends light pulses to be sent to sensitive fibers; � A photonic lantern with 3 or more single-mode fiber optic ports and one multimode fiber port connected to the sensor's multimode fiber; � An optical receiver, consisting of a number of photodetector devices equal to the number of single-unit fiber optic ports of the lantern minus 1, each of which is connected to each of the single-mode ports. � System for processing signals output from the optical receiver, The light source is connected to one of the single-mode optical fibers, and the other single-mode port is connected to the optical receiver. Also described is a process for reconfiguring an optical reflection system previously installed at a facility to be monitored. � Multi-bit stream fiber optic fiber measurement system Using multiphase flow monitoring methods ENI SpA, P.le Enrico Mattei 1, Roma Description of the invention This invention relates to a vibration measurement system for monitoring multiphase flow, in particular in extraction wells and lines, based on background light analysis by a multi-purpose fiber. Most non-optical techniques do not provide for direct mechanical interaction with the flow (with the exception of venturi tubes and / or flow mixers), but are based on interactions with radiation of various types. Thus, there are gamma rays, X-rays and ultrasonic tomography, electrical impedance tomography and dielectric constant analysis using microwaves. Due to their nature, these techniques are not suitable for use in the well, therefore, they do not reveal the composition of the flow in the inlet sections of the well. In the existing literature, optical sensors are typically classified into ‘direct’ and ‘indirect’. ‘Direct’ sensors are those in which electromagnetic radiation interacts directly with the current, while in ‘indirect’, the electromagnetic radiation does not interact directly with the current flow. Direct sensors generally use various phenomena (total internal reflection, transmission or attenuation of the wave, fluorescence) to estimate the composition of the flow, often using spectroscopic techniques. Among direct sensors, there are examples of optical tomography sensors. In the case of indirect sensors on the other hand, optical radiation is used to measure the temperature or deformation caused by the sensor (whether fiber, cavity resonance or other) by the pipeline, the well structure or even directly by the flow itself. It should be noted that in the case of indirect sensors the physical parameters measured are not only temperature or deformation. Information on other parameters can be deduced from this. In particular, deformation measurements correspond to pressure or vibration measurements, where the two are often characterized by the frequency band of the observed phenomenon. Vibration is therefore known as mechanical energy and therefore one of the most important fiber optic vibration sensors is distributed as an acoustic sensor. In the case of multi-stage flow structures these basic physical measurements are derived through appropriate physical models of the raw data and data processing. Although existing literature suggests temperature measurement as an indirect solution to obtain multi-phase flow composition, patent activity seems to be more inclined towards vibration measurement. In this context, it is appropriate to mention the potential of distributed fiber optic sensors. In the area of ​​measuring local parameters of multi-phase flow, distributed temperature and vibration measurements, they provide a continuous map with the appropriate space and time for the entire well, which can be done through appropriate computational algorithms. It should be noted that such distributed measurements can be performed along the well only with technologies based on the use of fiber optics. In or near a well, several multimode optical fibers, generally made of silica, are installed in a position parallel to the well. These fibers have two uses: for bidirectional data transmission in a buttonhole / surface bus or as a distributed temperature sensor using the Raman method. A different use of previously installed fibers is proposed in US Patent US-7668411 by Schlumberger Tech. Corp to provide a distributed vibration sensor through spatial analysis of the reversible signal due to the Rayleigh effect. The OTDR measuring instrument is coupled to a highly coherent pulsed light source, usually a DFB laser. Due to the high spatial coherence of the source, the backscattered signal due to scattering points within the optical pulse creates an interference signal at the receiver. If single-mode fiber is used, the measurement based on Rayleigh scattering is simpler. On the other hand, the use of multimode fibers along the well is very common due to their greater tolerance to bending, simpler connections and, finally, because Raman emission-based temperature measurement systems practically use multimode fibers. To overcome the non-optical nature of the multimode filler, the solution proposed in US-7668411 provides for the placement of a “single-mode filter system” between the coherent OTDR and the multimode fiber (see Figures 3, 4, 5 and 6 of the invention). The invention also provides for a “single-mode filter system”, for example, using a single-mode fiber or a pin in the air. The solution described in that invention has the following three critical technical points: 1. The use of a single-mode fiber beam splitter (e.g. a single-mode fiber beam splitter) placed between the laser source and the multimode sensor fibers is generally a major source of loss in the measurement signal; the typical thickness in a single-mode fiber-multimode fiber splice may vary from 6 to 15 dB. This loss will have a very small effect on the signal-to-noise ratio (SNR), limiting the measurable fiber length, spatial resolution, vibrational band or sensitivity. If a pin in the air is used to provide a "spatial mode splice" as proposed in US-7668411, the loss will be even greater; an air hole is used to make a single-mode filter. 2. It may happen that the selected "single spatial mode" is temporarily sensitive to fine vibrations. This problem is well known to those skilled in the art and is described in US-7668411, where it is proposed to solve the problem by selecting another "element or void". However, there is no explanation of how this selection is made. 3. Interpretation of distributed vibration measurements may lead to an increase in critical points. In fact, it should be remembered that the purpose of the patent is to reuse multimode fibers that have already been installed in wells for other purposes and are therefore not necessary for vibration measurements. Multimode optical fibers are often preferred to single-mode fibers for installation in production wells due to the greater ease of making connections. This aspect makes the configuration of the vibration measurement system suboptimal and enables the definition of precise mathematical models that allow vibration measurements tailored to more complex multiphase flow properties. A new system has now been found that offers a solution to the three problems mentioned above, and proposes the elimination of the spatial mode filtering system envisaged by US-7668411, and the placement of a photonic lantern, with three or more single-mode optical fiber ports and a multimode fiber, between the source, the multimode measurement fiber and the receiver. This ensures a better signal-to-noise ratio that can offer improvements in dynamics, resolution or sensitivity. In relation to the measurement of distributed vibrations in multimode fibers, the present invention overcomes some of the inherent problems of the solution of US-7668411. In particular, the present invention minimizes the insertion loss due to the coupling between the spatially integrated filter system and the multimode fiber, thereby improving the quality of the measurement. Furthermore, the present invention allows the different points of the return signal to be monitored live, thereby inherently being immune to the problem of individual particle loss, which affects the system of US-7668411. The reflective vibration measurement system that is the subject of this invention for monitoring multiphase flow, particularly in production wells or pipelines, using multi-purpose fibers, comprises: � Multi-purpose sensing optical fiber; � A light source consisting of a high-coherence laser that sends light pulses to be sent to sensitive fibers; � "Photonic lantern" with three or more single-mode fiber optic ports and one multimode fiber port connected to the sensing multimode fiber; � an optical receiver, comprising a number of photodetectors equal to the number of said single-mode optical fiber ports minus 1, wherein each photodetector is connected to each of the single-mode ports; � System for processing the signals output from the optical receiver. The light source is connected to one of the single-mode optical fibers, and the other single-mode fiber is connected to the light receiver. The system preferably predicts: � The light source has two output ports, in a first port emitting an optical signal at a first frequency and in a second port emitting an optical signal at a second frequency different from the first frequency; � The optical receiver includes a light splitter with 1 input and a number of outputs equal to the number of photodetectors, and also includes a number of optical combiners equal to the number of photodetectors, where: o The input port of the splitter is connected to the second port of the light source; o Each of the output ports of the splitter is connected to each combiner; o Each combiner is connected to each of the photodetectors. Another object of this invention is a method of measuring vibrations along a structure through the system described above, which comprises: � Locate a multi-purpose sensing optical fiber along the structure to be monitored; � Sending a light pulse to the sensing optical fiber; � Selection of one or more background optical speckles from the "sensing" fiber due to Rayleigh scattering caused by the emitted pulse; � �Generate a signal that represents vibration along the monitored structure from multiple fiber-collected columns. The method may involve using a multi-dimensional fiber to provide reversible light to the optical receiver. Another objective of this application is the process of reconfiguring an optical domain reflector system that has already been installed in the structure to be monitored. Vibration mapping along a wellbore may be performed in a non-invasive manner using a reflection method based on coherent Rayleigh scattering, using previously installed optical fibers. Specifically, the backscattered signal is analyzed and, through the use of two (or more) receivers in parallel, it is possible to process the states that have a spatial and temporal behavior that changes due to external disturbances, usually pressure, temperature and vibration. While pressure and temperature change slowly, vibration due to their nature varies rapidly in time and space, which makes them easier to detect and then analyze. Spatial mapping of temperature, pressure and vibration (along the wellbore) allows the detection of malfunctions, changes in the composition of multiphase flow, the formation of bottlenecks due to hydrate precipitation, etc. in a live and simultaneous manner. As previously mentioned, vibration measurements can be much more accurate if single-mode fiber is used. Consequently, if we want to use multimode fibers already installed in the well, a performance reduction compared to the desired performance must be accepted. An innovative idea involves using the same multimode fiber to interrogate local sensors installed next to the well, to integrate vibration distribution measurements with other physical parameters. These local sensors may be installed during well maintenance, and are possibly as objects already installed in certain components of the well itself (e.g. valves, etc.). The measured parameter may still be vibration, but at the point of using the sensor or internal reflection as a whole for direct analysis of the three-phase current already known in the advanced state. Individual sensors may be processed using multi-wavelength techniques, so that the same multi-mode fiber can be used to perform vibration distribution measurements and local sensors can be investigated at the same time. The process of the present invention for reconfiguring an optical reflection system, comprising a multi-purpose sensor optical fiber mounted next to the aforementioned structure, a source for launching optical signals to the multi-purpose sensor fiber, an optical receiver for receiving light, Rayleigh scattering caused by the pulse-triggered, mainly involves inserting a "photonic lantern" between the sensor fiber and the optical receiver that spatially separates several points of light caused by Rayleigh scattering, each output of which is connected to a photodiode. The process may also include generating a signal indicative of vibration along the monitored structure, using an analysis system based on multiple recorded speckles. To better define this invention, an example is shown that demonstrates the effectiveness of the proposed system. Example 1 The diagram can be seen in Figure 1. A high-coherence laser 101 with an emission wavelength typically between 800 and 1650 nm (preferably between 1300 and 1650 nm) controlled by an external pulse generator 102, produces optical pulses typically 3 to 200 ns (preferably 20-100 ns) with a repetition rate of at least 1 kHz, is connected to one of the input ports of a photonic lantern. The other input ports of the photonic lantern are connected to one or more photodiodes (PDs) that provide electrical signals proportional to the corresponding optical input plates. The multi-function output port of the photonic lantern is connected to the multi-function sensor fiber. Complaint 1. Vibration measurement system and relative method for monitoring multiphase flow in extraction wells or pipes, with reversible multidimensional fiber light analysis, comprising: � Multi-purpose sensing optical fiber; � A light source consisting of a high-coherence laser that sends light pulses to be sent to sensitive fibers; � A photonic lantern with 3 or more single-mode fiber optic ports and one multimode fiber port connected to the sensor's multimode fiber; � An optical receiver, consisting of a number of photodetector devices equal to the number of single-unit fiber optic ports of the lantern minus 1, each of which is connected to each of the single-mode ports. � System for processing signals output from the optical receiver, The light source is connected to one of the single-mode optical fibers, and the other single-mode port is connected to the optical receiver. 2. The system according to claim 1, wherein: � The light source has two output ports, in a first port emitting an optical signal at a first frequency and in a second port emitting an optical signal at a second frequency different from the first frequency; � ���The optical receiver consists of a light splitter with 1 input and a number of outputs equal to the number of photodetectors, and also includes a number of optical combiners equal to the number of photodetectors, The input port of the splitter is connected to the second port of the light source; � Each of the output ports of the splitter is connected to each combiner; � Each combiner is connected to each of the photodetectors. 3. Method for measuring vibrations along a structure by means of a system according to at least one of claims 1 to 2: � Locate a multi-purpose sensing optical fiber along the structure to be monitored; � Sending a light pulse to the sensing optical fiber; � Selection of one or more background optical speckles from the "sensing" fiber due to Rayleigh scattering caused by the emitted pulse; � �Generate a signal that represents vibration along the monitored structure from multiple fiber-collected columns. 4. The method according to claim 3 further comprising using a multi-dimensional fiber to provide reversible light to the optical receiver. 5. Method for reconfiguring an optical reflector system according to at least one of claims 1 to 2, previously installed in a facility to be monitored, comprising a multi-purpose sensor optical fiber installed next to said structure, a source for initiating optical signals to the multi-purpose sensor fiber, an optical receiver for receiving light, Rayleigh scattering caused by the pulse-triggered light, mainly comprising inserting a "photonic lantern" between the sensor fiber and the optical receiver that spatially separates a plurality of points of light caused by Rayleigh scattering, each output of which is connected to a photodiode. 6. The process according to claim 5 further comprising generating a signal indicative of vibration along the monitored structure, using an analysis system based on the multiple recorded speckles. MURG * 170069

Claims

CLAIMS 1. Reflectometric system for vibration measurement to monitor multiphase flows by analysis of the light backscattered by multimode fiber comprising: · a sensing multimode optical fiber; · an optical source, containing a high coherence laser that emits optical pulses to be sent in said sensing fiber; · a photonic lantern with 3 or more single-mode optical fiber ports , and one multimode fiber port connected to the sensing multimode fiber; · an optical receiver, comprising a number of photodetectors equal to the number of single-mode optical fiber ports of said photonic lantern minus 1, wherein each photodetector is connected to each of said single-mode ports; · a system for processing output signals from the optical receiver, the optical source being connected to one of the single-mode optical fiber ports and the other single-mode fibers being connected to the optical receiver.

2. System according to claim 1, wherein: · the optical source has two output ports, emitting at a first port an optical signal at a first frequency and at a second port an optical signal at a second frequency, different from said first frequency; · the optical receiver includes a light splitter with 1 input and a number of outputs equal to the number of photodetectors, and also includes a number of optical combiners equal to the number of photodetectors: · the input port of said splitter is connected to said second port of the optical source; · each output port of said splitter is connected to each combiner; · each combiner is connected to each of said photodetectors.

3. Method for vibration measurements along a structure by means of a system according to at least one of claims from 1 to 2: · finding a sensing multimode optical fiber installed along the structure to be monitored; · launching an optical signal in said optical sensing fiber; · selecting more than one speckle of the light backscattered from the sensing fiber by Rayleigh scattering induced by the launched pulse; · generating from the multiple speckles collected from the fiber a signal indicative of the vibrations along the monitored structure.

4. Method according to claim 3 further comprising also the use of a multimode fiber to convey the backscattered light towards the optical receiver.

5. A method for reconfiguring an optical reflectometry system, according to at least one of claims from 1 to 2, already installed at a facility to be monitored, comprising a sensing multimode optical fiber installed along said structure, a source for launching pulses in said sensing multimode fiber, an optical receiver for receiving the light backscattered by said sensing fiber by Rayleigh scattering induced by the impulse launched, characterized in that it comprises the interposition between the sensing fiber and the optical receiver of a photonic lantern to spatially separate multiple speckles of the light backscattered by Rayleigh scattering.

6. Process according to claim 5 comprising also generating a signal indicative of the vibration along the monitored structure, by means of an analysis system based on the multiple speckles recorded. MURG * 170069

Images