CN102364046B - Multi-phase flow meter for underground pipeline - Google Patents

Abstract

The invention relates to a multiphase flowmeter for downhole pipelines, which is characterized in that two sets of optical intensity modulation optical fiber sensors are installed at the outlet of oil well pipelines to measure the light reflectance and light transmittance of crude oil respectively, and can be processed after treatment. Calculate the proportion of each phase of the oil-gas-water three-phase mixed liquid per unit time, and then use the phase modulation optical fiber sensor to measure the average flow rate of the mixed liquid per unit time, and calculate the flow rate of each single phase per unit time according to the proportional relationship. Using TMS320LF2407A to comprehensively analyze and process the data, the quality of crude oil can be judged in real time, so as to provide necessary data for rapid correction of oil production process. The invention has the advantages of high data collection accuracy, good multiphase flow discrimination effect, convenient use and flexible operation, is a practical multiphase flowmeter, and has wide application prospects in fields such as oil fields.

Description

A multiphase flowmeter for downhole pipeline

technical field

The invention relates to a multiphase flowmeter used for downhole pipelines, which belongs to a data acquisition and processing system and is suitable for fields such as oil fields. the

Background technique

Currently, in the global energy crisis, the price of oil has exceeded 100 US dollars per barrel. In order to better extract oil and save energy, the requirements for data processing in oil extraction are getting higher and higher. the

The main technology used in oil extraction is to calculate the flow rate of each phase based on the data after measuring some data, which will greatly affect the flow accuracy. The measurement error of each phase is ±10%; all the technologies currently used for multi-phase measurement require that the characteristics of the fluid, such as dielectric constant, mass absorption coefficient, etc., be mastered in order to measure more accurately. Frequent evaluation and calibration of the multiphase flowmeter sensors is necessary if fluid properties vary or if the multiphase flowmeter is used for multi-well metering. the

The existing problems and shortcomings are: the highest applicable gas content of several major multiphase flowmeters on the market is 0.9% to 1.0%. With the increase of gas content, the measurement accuracy of the liquid phase will be affected; the multiphase flowmeter Radiation sources such as microwaves are widely used, and the relevant regulations have strict restrictions on the use of radiation sources; current multiphase flowmeter calibration facilities can only calibrate component measurement instruments well, and there is no satisfactory calibration for flow rate measurement method. the

Contents of the invention

technical problem to be solved

In order to avoid the deficiencies of the prior art, the present invention proposes a multiphase flowmeter for downhole pipelines, which can deduce the ratio of each component according to the change of the optical refractive index of the multiphase fluid without separating the multiphase flow Real-time judgment of crude oil quality can be realized, so as to achieve the purpose of quickly correcting the oil production process. the

The idea of the present invention is to: design a multiphase flowmeter signal processing circuit with the TMS320LF2407A chip as the core; design an optical fiber sensor applied to this kind of multiphase flowmeter; design a sensor signal transmission and transmission circuit. the

Technical solutions

A multiphase flowmeter for downhole pipelines, characterized in that it includes a downhole collection subsystem and an uphole processing subsystem; the downhole collection subsystem includes an optical fiber sensor group, a temperature sensor, a pressure sensor and a voltage and current conversion connected to each The temperature sensor and the pressure sensor are set on the pipe wall on the side of the pipeline at the outlet of the oil well pipeline. The temperature signal of the temperature sensor is converted into a current signal by a voltage-current converter and transmitted to the uphole processing subsystem. The pressure signal of the pressure sensor is passed through the voltage The current converter converts the current signal into a current signal and transmits it to the processing subsystem on the well; the optical fiber sensor group includes a light source, two sapphire lenses, two light intensity modulation optical fiber sensors and a phase modulation optical fiber sensor, and the light source is arranged in parallel on one side of the pipe wall , Light intensity modulated optical fiber sensor and phase modulated optical fiber sensor. The light intensity modulated optical fiber sensor measures the reflected light intensity passing through the pipeline, and converts it into a current signal through a photoelectric converter and a voltage-current converter and transmits it to the processing subsystem on the well; On the other side of the tube wall facing the optical axis of the light source, a light intensity modulated optical fiber sensor is installed to measure the transmitted light intensity passing through the tube, and convert it into a current signal through a photoelectric converter and a voltage-current converter and transmit it to the processing subsystem on the well ; There is a sapphire lens at the transmitting end of the light source and the receiving end of the light intensity modulation optical fiber sensor on the opposite side; the above-hole processing subsystem includes a current-voltage converter, an A/D converter, a shaper, a counter and a DSP digital The processor, the current-voltage converter receives the data of the underground acquisition subsystem, converts it into a voltage signal through the current-voltage converter, and then forms a digital signal through the A/D converter and outputs it to the DSP digital processor; the shaper converts the current-voltage converter into a voltage signal The signal is shaped into a pulse signal and output to the counter to count the pulse signal. the

The DSP digital processor adopts TMS320LF2407A chip. the

The light source is a high-power light-emitting diode. the

Beneficial effect

A kind of multiphase flow meter that is used for downhole pipeline that the present invention proposes has two obvious advantages: one, the data acquisition precision is high. Because the optical sensor is inside the oil well, the gas in the crude oil has not yet volatilized, so the data obtained in this way are highly reliable; 2. DSP quickly analyzes the data. This system uses TMS320LF2407A as a digital signal processor, which can process multiple signals at the same time and ensure high efficiency of the system. Stablize. the

Description of drawings

Figure 1: Schematic diagram of the system of the present invention;

Figure 2: Schematic diagram of sensor installation of the present invention;

Figure 3: Schematic diagram of the optical path of the present invention;

Fig. 4: The schematic diagram of the integer device and the counter circuit of the frequency signal of the embodiment of the present invention;

Fig. 5: the voltage-to-current converter of temperature sensor of the embodiment of the present invention;

Fig. 6: The voltage-to-current converter of the pressure sensor of the embodiment of the present invention. the

Detailed ways

Now in conjunction with embodiment, accompanying drawing, the present invention will be further described:

The embodiment of the present invention sees accompanying drawing 1, comprises downhole acquisition subsystem and uphole processing subsystem, and downhole acquisition subsystem sends the signal that collects to uphole processing subsystem, and uphole processing subsystem sends average velocity V, light transmittance I _T , light reflectance I _R , pressure P, temperature T, the analog signals of the five signals are converted into digital signals and then processed to obtain measurement results.

The above-ground signal processing subsystem: see Fig. 1, Fig. 4: including current-voltage converter, A/D converter, shaper, counter and DSP digital processor, the current-voltage converter receives the data of downhole acquisition subsystem, After being converted into a voltage signal by a current-voltage converter, a digital signal is output to the DSP digital processor after being entered by an A/D converter; the shaper shapes the signal of the current-voltage converter into a pulse signal, and outputs it to a counter to count the pulse signal . the

Four 4-20mA current signals and one frequency signal sent by the downhole acquisition subsystem. It is directly converted into a voltage signal of 0.6~3V through a 150Ω precision resistance, and is collected by an A/D converter; after the frequency signal of 4~20mA is converted into a voltage signal, it is shaped into a pulse signal by a voltage shaper, and the counter is used to control the voltage signal. Pulse signal counting (see Figure 5), after the counting results in a certain time interval are latched, they can be collected by the I/O interface of the processor. The A/D converter adopts the AD574 chip of AD Company, which converts the analog signal into a digital signal that can be processed by the DSP digital processor. DSP uses TMS320LF2407A chip to process the collected digital signals. The processing results are stored in the off-chip FLASH memory in turn, and the host computer reads it regularly through the RS-485 serial communication interface. the

After the five signals of average flow velocity V, light transmittance I _T , light reflectance I _R , pressure P, and temperature T are obtained by the processor, the oil-gas-water ratio and the single-phase traffic. The data is stored in the off-chip FLASH memory, which is regularly read by the host computer through the RS-485 serial communication interface. The sampling time interval and counting time length need to be set in the acquisition control software according to the actual situation on site. There is no strict mathematical derivation formula for the relationship between the oil-gas-water ratio and the semaphore. It needs to be calibrated according to the experimental data to obtain the empirical formula.

The downhole acquisition subsystem is shown in Fig. 2 and Fig. 3, and includes an optical fiber sensor group, a temperature sensor, a pressure sensor and a voltage-current converter connected with each other, and the temperature sensor and the pressure sensor are arranged on the pipe wall on the side of the pipe at the outlet of the oil well pipe Above, the temperature signal of the temperature sensor is converted into a current signal by a voltage-current converter and transmitted to the uphole processing subsystem, and the pressure signal of the pressure sensor is converted into a current signal by a voltage-current converter and transmitted to the uphole processing subsystem; the optical fiber sensor group includes Light source, two sapphire lenses, two light intensity modulated fiber optic sensors and phase modulated fiber optic sensors, the light source, light intensity modulated fiber optic sensor and phase modulated fiber optic sensor are arranged in parallel on one side of the tube wall, the light intensity modulated fiber optic sensor The sensor measures the reflected light intensity passing through the pipeline, and converts it into a current signal through a photoelectric converter and a voltage-current converter and transmits it to the uphole processing subsystem; on the other side of the tube wall, there is a light intensity modulation optical fiber on the optical axis facing the light source The sensor measures the intensity of the transmitted light passing through the pipeline, and converts it into a current signal through a photoelectric converter and a voltage-current converter and transmits it to the processing subsystem on the well; at the transmitting end of the light source and the receiving end of the light-intensity-modulated optical fiber sensor on the opposite side The end has a sapphire lens. the

A is crude oil, B is the beam emitted by light source 1, C is the sapphire lens, and D is the reflected beam. Light intensity modulation optical fiber sensor 2 measures light transmittance I _T and light reflectance I _R ; phase modulation optical fiber sensor 3 measures average flow velocity V; pressure sensor 4 measures pressure P; temperature sensor 5 measures temperature T . The signal obtained by the fiber optic sensor must first pass through the fiber optic voltage sensor and be converted into a voltage signal. Due to the long distance between the downhole sensor and the surface processor, in order to reduce the influence of signal attenuation and interference, the sensor signal needs to be converted into a 4-20mA current signal through voltage and current conversion before being sent to the processor. The voltage-to-current conversion circuits and photoelectric converters of _IT , I _R , and V adopt mature products for the voltage-to-current converters of P and T, as shown in Figure 5 and Figure 6.

In this system, the quartz step multimode optical fiber with a core diameter of 62.5um is selected. In order to improve the reliability of the system, a metal or plastic protective sleeve is added to the optical fiber to avoid damage to the optical fiber in the harsh working environment. A high-power light-emitting diode is used as the light source of the fiber optic sensor. Using the light intensity modulation fiber optic sensor, place the sensor probe into the pipeline 5-10mm, and use two photocells to detect the changes in the intensity of transmitted light and reflected light respectively, and the ratio of oil, gas and water can be calculated through a certain relationship. Optical fiber sensors require a very stable light source with a power above the milliwatt level, otherwise they cannot penetrate the mixed liquid. Use a phase modulation fiber optic processor to measure the average flow velocity of the mixed liquid. According to the optical Doppler phenomenon, the reflected beam loaded with the flow velocity signal is coherent with another reference reflected beam and then projected onto the optical detector to obtain a set of frequency signals. The frequency is high or low. represents the size of the average flow velocity. The same light source can be used for the determination of flow rate and oil-water-air ratio. the

Claims (3)

1. A multiphase flowmeter for downhole pipelines, characterized in that it includes a downhole collection subsystem and an uphole processing subsystem; the downhole collection subsystem includes an optical fiber sensor group, a temperature sensor, a pressure sensor and the above three parts A voltage-to-current converter is connected. The temperature sensor and the pressure sensor are set on the pipe wall at the outlet of the oil well pipeline. The temperature signal of the temperature sensor is converted into a current signal by the voltage-to-current converter and transmitted to the uphole processing subsystem. The pressure signal of the sensor is converted into a current signal by a voltage-to-current converter and transmitted to the uphole processing subsystem; the fiber optic sensor group includes a light source, two sapphire lenses, two light intensity-modulated fiber optic sensors and a phase-modulated fiber optic sensor. A light source, a light intensity modulated fiber sensor and a phase modulated fiber sensor are set in parallel on one side of the tube. The light intensity modulated fiber sensor measures the reflected light intensity passing through the pipeline, and converts it into a current signal for transmission through a photoelectric converter and a voltage-current converter. To the uphole processing subsystem; on the other side of the tube wall facing the optical axis of the light source, a light intensity modulated optical fiber sensor is installed to measure the transmitted light intensity through the tube, and convert it into a current signal through a photoelectric converter and a voltage-current converter Transmission to the uphole processing subsystem; a sapphire lens is provided at the transmitting end of the light source and the receiving end of the light intensity modulation optical fiber sensor on the opposite side; the above-hole processing subsystem includes a current-voltage converter, an A/D converter, a shaping The current-voltage converter receives the data of the underground acquisition subsystem, converts it into a voltage signal through the current-voltage converter, and then enters the A/D converter to form a digital signal and output it to the DSP digital processor; shaping The converter shapes the signal of the current-voltage converter into a pulse signal, and outputs it to the counter to count the pulse signal. 2. The multiphase flowmeter for downhole pipeline according to claim 1, characterized in that: said DSP digital processor adopts TMS320LF2407A chip. 3. The multiphase flowmeter for downhole pipelines according to claim 1, wherein the light source is a high-power light emitting diode.

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