An oil-water two-phase measurement device and method based on swirl shaping

Abstract

An oil-water two-phase measuring device based on swirl shaping includes an oil-water swirl shaping device. The straight pipe section required by the invention is greatly shortened, the pressure difference is also greatly reduced, and it has excellent adaptability to the conditions of rotating flow and vortex. For two-phase fluid, the swirl device can rectify the complex two-phase fluid into a uniformly dispersed flow or annular flow state in the tube that is symmetrical about the axis, thereby making it easier to measure. Since only a simple swirl device is affected in the measurement of this method, this method and device are easier to standardize compared to other non-standard differential pressure flow meters.

Description

Technical Field

[0001] The invention belongs to the technical field of two-phase flow rate and water content measurement, and particularly relates to an oil-water two-phase measurement method for oil field and oil well production fluid. Background Art

[0002] Two-phase flow is widely present in modern industrial production and daily life, and two-phase flow in pipelines often appears in various fields of production processes such as petroleum, chemical industry, metallurgy, and food. Its parameter detection is of great significance for the rational development of resources, production safety, and industrial process control. It has become a frontier subject that has received great attention at home and abroad. Therefore, accurate online measurement of various parameters of two-phase flow, such as the flow rate of each phase, phase content, etc., plays an important role in industrial production. However, due to the diverse flow patterns and complex flow mechanisms of two-phase flow, the measurement research on two-phase flow is still a hot spot and difficult point.

[0003] In the oilfield production process, the oil well produced fluid mainly contains oil, associated gas, water, etc. The oilfield surface multiphase flow is the oil and water two-phase flow or oil, gas, water three-phase flow in the oilfield surface pipeline. The pipeline has several situations such as horizontal, inclined and vertical. The surface multiphase pipe flow starts from the wellhead of the oil well, and goes through the process of collection, transportation, pressurization, gas-liquid separation, oil-water separation, etc. in the middle. It is necessary to measure the total flow rate of oil, gas, and water in the pipeline at different process stages, the phase flow rate, water content, gas content and other parameters. The "two-phase" in the present invention refers to the two-phase oil phase and water phase in the oilfield production fluid. Due to the complexity of oil and water flow, the oil-water two-phase measurement method is very difficult, and there are currently a variety of two-phase measurement technology routes.

[0004] According to the research results at home and abroad, the oil-water two-phase flow measurement scheme can be summarized into two types: one is to use the uniform flow model to measure the mixed phase flow rate using conventional single-phase flow instruments, and calculate the phase flow rate through phase content analysis; the other is to separate the oil and water through a two-phase separator and measure the oil and water volume respectively. The core technologies of oil-water two-phase flow measurement include: one is the oil-water separation method, the second is the structural optimization design of the oil-water separator, and the third is the oil-water phase content measurement technology. Elkow KJ, Kozma R. and others studied various oil-gas-water phase flow measurement methods such as capacitance method and thermal method. Cao Xuewen, Kou Jie, Lin Zonghu and others summarized and summarized the measurement principles of various multiphase flow meters currently used in actual production at home and abroad and how to select them under different application conditions. The application of Coriolis force mass flowmeter can simultaneously measure the mass flow rate and water content of oil-water two-phase flow. There are many flowmeters for flow measurement, such as volumetric flowmeter, velocity flowmeter, mass flowmeter, etc.

[0005] In multiphase flow metering technology, separation method is still the most reliable and accurate technology. For example, Chinese patents ZL200810112558.3 ​​and ZL200710046862.8 all use large containers as oil, gas and water three-phase separation systems, and then use single-phase metering methods. Because this method separates the oil, gas and water three-phase fluid in the multiphase fluid into single-phase gas, oil and water, and then uses a single-phase flowmeter to measure the flow of each phase, thereby avoiding the influence of flow pattern changes and flow instability on the measurement. However, in actual multiphase fluid measurement, many fluids are sometimes unable to be completely separated economically and effectively, and this multiphase metering brings a lot of trouble.

[0006] Therefore, scholars at home and abroad have summarized and analyzed various combined methods for measuring multiphase flow, such as using electrical, magnetic or radioactive methods to measure the phase density, phase content and phase velocity of the three phases of oil, gas and water online, so as to achieve oil, gas and water three-phase measurement, such as ZL201410468193.3 and 200810150257.X. With the progress of related research work, new technologies for multiphase detection continue to emerge. The multiphase flow measurement method based on multi-sensor combination can be summarized into the following three categories: (1) Combination of single-phase flowmeter and density sensor (or water content sensor) The flowmeters used in this method include: volumetric flowmeters such as swivel flowmeter and scraper flowmeter, velocity flowmeters such as turbine flowmeter, differential pressure flowmeters such as orifice plate and venturi tube, and mass flowmeter. The phase content uses a pressure difference density meter, a capacitance water content meter or a ray water content meter. (2) Combination of single-phase flow sensor and single-phase flow sensor This method uses two or more single-phase flow meters whose signal output is related to both flow rate and phase content to fuse. Among them, the most widely used is the fusion of differential pressure sensor and differential pressure sensor. (3) Dual sensor correlation analysis and phase content sensor integration This method is most commonly used for dual-ray attenuation sensor correlation velocity measurement, and at the same time uses the attenuation signal to analyze the phase content. There are also dual venturi tubes for correlation and content analysis. There are also capacitance correlation and conductivity correlation for flow and water content measurement. Different multiphase flow meters are suitable for different media conditions. The interface stability and pressure drop of the three-phase pipe flow of oil, gas and water change with the different states of the pipeline geometry, the content of each phase of the fluid, the fluid pressure, temperature, etc., showing different flow patterns, which are called flow patterns. Different flow patterns have a great influence on the accuracy of flow parameter measurement. The change of gas phase in the three-phase flow of oil, gas and water has the greatest influence on the flow pattern. The research on gas-liquid two-phase flow and multiphase flow by researchers such as D.Favrat and O.Zurcher mainly focuses on the research on the flow patterns of fluids in horizontal and vertical pipelines, and the flow patterns in vertical and horizontal pipelines. However, the application of existing technologies is still very difficult for oil well produced fluids, which have large fluctuation ranges in flow and phase content and complex flow. At present, there are many methods for measuring the flow rate and water content of oil well produced fluids, but they generally have small measurement ranges, limited applicability, and high prices, which are difficult to meet the actual needs of oil field production.

[0007] Based on the urgency of online metering of oil well production, indoor and field experimental studies have shown that when the oil-water two-phase flow makes a spiral rotation in the pipe, a cyclonic pressure difference and an axial differential pressure will be generated. These two pressure differences are very sensitive to flow and water content. Under a given flow, both pressure differences have a stable corresponding relationship with water content. Therefore, the present invention is based on the above research. Compared with the prior art, the invention not only has a high resolution, but more importantly, it uses differential pressure measurement technology. The current differential pressure transmitter is very mature in technology, stable and reliable in operation, economically reasonable, and suitable for large-scale application. Summary of the invention

[0008] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to propose a differential pressure flow and water content measurement method based on swirl shaping. The swirl shaper is mainly used to rectify the oil-water two-phase flow into a uniform dispersed flow or an oil core-water ring based on axisymmetric flow pattern, and the radial differential pressure generated along the center and wall of the pipeline and the axial pressure difference formed before and after the swirl shaping device are related to the flow and water content, so as to realize the dual parameter measurement of water content and liquid phase flow of the oil-water two-phase by double differential pressure.

[0009] The purpose of the present invention can also be achieved by the following technical measures:

[0010] A method for measuring the oil-water two-phase content and flow rate based on swirl shaping, mainly comprising an oil-water mixture inlet section, an oil-water swirl shaping device, an upstream axial pipe wall pressure-inducing pipe for oil-water mixture, an axial pipe wall pressure-inducing pipe for downstream oil-water mixture, a radial pipe wall pressure-inducing pipe for downstream oil-water mixture, a central pressure-inducing pipe for radial pipe of oil-water mixture, and an axial differential pressure transmitter ΔP for oil-water mixture. z , radial differential pressure transmitter for oil-water mixture ΔP r , the oil-water mixture outlet is composed. The oil-water mixture is first shaped by the oil-water swirl shaper, and the flow pattern required for radial and axial pressure difference measurement is established with an axisymmetric uniform dispersed flow or uniform annular flow pattern. It is connected to the axial and radial differential pressure measurement system through the pressure pipeline, and the radial pressure difference between the center tube and the wall at the specified section after swirl shaping and the axial pressure difference between the two walls at the specified section before and after swirl shaping are measured respectively. The relationship between the axial pressure difference and the radial pressure difference and the water content and flow rate are established respectively, so as to realize the measurement of the water content and flow rate of the oil-water two-phase.

[0011] The present invention utilizes a swirl device and a static rotating flow channel to force rotation for shaping, thereby increasing the scope of application in different occasions. It is not only suitable for stratified flow and wavy stratified flow at low flow rates, but also suitable for annular flow and elastic flow at high flow rates.

[0012] The oil-water mixture with complex flow pattern is arranged into the desired axisymmetric uniform flow pattern through the swirl device, and the flow pattern required for radial and axial pressure difference measurement is established.

[0013] When the axial pressure taking points are arranged, the first pressure taking position is located between 2D-5D upstream of the cyclone device, and the second pressure taking position is located between 5D-10D upstream of the cyclone device.

[0014] The radial pressure-taking surface is arranged between 1D-5D downstream of the swirl device, and the second axial pressure-taking position can coincide with the radial pressure-taking wall pressure-taking position.

[0015] The swirl blades in the swirl device selected in the patent of the present invention can be either elliptical blade type or spiral type. The angle θ of the elliptical blade type is 45-60°, and the rotation angle θ of the spiral type is 30-60°.

[0016] The present invention discloses an oil-water two-phase measurement method based on the swirl shaping principle. It is known from fluid mechanics that the axial pressure difference is caused by the friction along the fluid flow process, while the radial pressure difference is caused by the centrifugal acceleration when the fluid rotates. Here, the radial pressure difference is expressed as ΔP z , the axial pressure difference is expressed as ΔP r , define the ratio of the two as λ, the formula is as follows:

[0017]

[0018] After a lot of indoor and field research, it was found that when the oil-water two-phase mixture flows through the cyclone device, the radial pressure difference ΔP z and axial pressure difference ΔP r The ratio λ and the volume water content β of the oil-water two-phase mixture have the following relationship:

[0019] β=A·λ 2 +B·λ+C (2)

[0020] Among them, A, B, and C are all constants and can be obtained through indoor experiments or field experiments.

[0021] At the same time, the total flow rate of oil-water mixture Q m The radial pressure difference of the swirl flow, the pipe radius R, the volume water content β, the water phase density ρ w , oil phase density ρ o .

[0022]

[0023] In addition, the radial flow coefficient α r and D are constants related to the fluid medium. Therefore, once the structure of the designed metering device is finalized, the corresponding radial value can be determined through indoor experiments.

[0024] The present invention discloses an online measurement method for oil-water two-phase based on the swirl shaping principle. The implementation steps are as follows:

[0025] Step 1: From formula (2), it can be seen that after the device is processed, as long as the radial pressure difference ΔP at a certain cross section after the swirl is measured, z and axial pressure difference ΔP r The volumetric water content β of the oil-water two-phase mixture can be obtained by substituting the ratio λ between the two.

[0026] Step 2: Substitute the measured water content β into formula (3), and combine the experimentally obtained related constants and oil-water density to obtain the total flow rate Q of the oil-water mixture: m , to achieve the measurement of total oil and water flow and phase content after degassing.

[0027] The present invention has the following advantages and features: the required straight pipe section is greatly shortened, the pressure difference is greatly reduced, and it has excellent adaptability to the situation of rotating flow and vortex. For two-phase fluid, the cyclone device can rectify the complex two-phase fluid into a uniformly dispersed flow or annular flow state in the tube that is symmetrical about the axis, so that it is more convenient to measure. Since only a simple cyclone is affected in the measurement of this method, this method and device are easier to standardize compared with other non-standard differential pressure flow meters. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. The drawings in the following description are only some embodiments of the present invention.

[0029] Figure 1 A schematic diagram of a device for measuring an oil-water two-phase method based on swirl shaping;

[0030] Figure 2 Schematic diagram of the structure of the oil-water cyclone shaper;

[0031] Figure 3 a Schematic diagram of the swirl shaping blade structure (elliptical blade type and its angle);

[0032] Figure 3 b Schematic diagram of the swirl shaping blade structure (spiral type and its rotation angle)

[0033] Figure 4 a is a schematic diagram of the flow pattern of the oil-water two-phase being transformed into an axially uniformly dispersed flow after being shaped by static swirl in a circular pipe;

[0034] Figure 4 b is a schematic diagram of the flow pattern of the oil-water two-phase being transformed into annular flow after static swirl shaping in a circular pipe;

[0035] Figure 5 Field measured curve of axial radial pressure difference ratio λ and β water content;

[0036] Figure 6 Field measured curve of radial pressure difference and flow rate.

[0037] The reference numerals are as follows:

[0038] 1 Oil-water mixture inlet; 2 Oil-water swirl shaper; 3 Upstream axial pressure-inducing pipe of oil-water mixture; 4 Downstream axial pressure-inducing pipe of oil-water mixture; 5 Downstream radial pressure-inducing pipe of oil-water mixture; 6 Center pressure-inducing pipe of radial pipe of oil-water mixture; 7 Axial differential pressure transmitter ΔP of oil-water mixture z ;8 Oil-water mixture radial differential pressure transmitter ΔP r ; 9 oil-water mixture outlet;

[0039] 2-1 swirl shaping blade; 2-2 swirl shaping blade outer tube. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] It mainly includes the following components: 1 oil-water mixture inlet section, 2 oil-water swirl shaper, 3 oil-water mixture upstream axial pipe wall pressure pipe, 4 oil-water mixture downstream pipe wall axial pressure pipe, 5 oil-water mixture downstream pipe wall radial pressure pipe, 6 oil-water mixture radial pipe center pressure pipe, 7 oil-water mixture axial differential pressure transmitter ΔP z ,8 Oil-water mixture radial differential pressure transmitter ΔP r , 9. Oil-water mixture outlet.

[0042] The oil-water mixture first passes through the oil-water mixture inlet 1 and enters the oil-water cyclone shaper 2 for shaping, and is shaped into a uniform dispersed flow pattern symmetrical about the axis, and the flow pattern required for radial and axial pressure difference measurement is established, and then the measurement is performed. The axial pressure difference is connected to the oil-water mixture axial differential pressure transmitter ΔP through the upstream axial pipe wall pressure guide pipe 3 of the oil-water mixture and the downstream axial pipe wall pressure guide pipe 4 of the oil-water mixture. z 7, to achieve the purpose of measuring the axial pressure difference on the specified two sections. In addition, on the specified section, the radial pressure guide pipe 5 on the downstream wall of the oil-water mixture and the radial pressure guide pipe 6 on the center of the oil-water mixture are connected to the radial differential pressure transmitter ΔP of the oil-water mixture. r 8, to measure the radial pressure difference on the specified cross section. The measured oil-water mixture flows out from the oil-water mixture outlet 9. Then, according to the formula, the ratio λ of the two phases is substituted to obtain the volume water content β of the oil-water two-phase mixture. Combining the experimentally obtained related constants and the oil-water density, the total flow rate Q of the oil-water mixture can be obtained. m , to achieve the measurement of total oil and water flow and phase content after degassing.

[0043] The oil-water swirl shaping mixer comprises a swirl shaping blade 2-1 and a swirl shaping blade outer tube 2-2, which is mainly arranged as follows: Figure 4 a and Figure 4 The (1) uniformly dispersed flow and (2) annular flow, which are symmetrical about the axis as shown in b, establish the flow patterns required for radial and axial pressure difference measurements.

[0044] Figure 3 Schematic diagram of the swirl shaping blade structure. The structures selected by the present invention in indoor and field experiments are (a) elliptical blade type, wherein the elliptical blade angle θ is 45-60°, and (b) spiral type, wherein the spiral rotation angle θ is 30-60°. In this embodiment, the fluid is first rectified by an elliptical blade, and then rectified twice by a spiral blade to ensure the output results of the oil-water two-phase. In field use, the staff uses separate elliptical blades and spiral blades. No matter how the parameters are adjusted, the measurement results cannot be guaranteed to be accurate. Only when the two are mixed can the final satisfactory results be achieved. In practical applications, the type and position of the blades can also be dynamically adjusted according to the needs of the site. For example, an elliptical blade is connected after a spiral blade, or a spiral blade is connected between two elliptical blades, etc. The different flow patterns of the oil-water two-phase in a circular pipe are converted into a measurable final flow pattern after static swirl shaping.

[0045] Through measurement, we finally get Figure 5 The field measured curve of the axial radial pressure difference ratio λ and β water content is shown in the figure. Figure 6 The shown graph is a field-measured curve of radial pressure difference and flow rate. Figure 5 The corresponding is when the oil-water two-phase mixture flows through the cyclone device, the radial pressure difference ΔP z and axial pressure difference ΔP r The formula for the ratio λ and the volume water content β of the oil-water two-phase mixture is:

[0046] β=A·λ 2 +B·λ+C.

[0047] Figure 6 The corresponding is the total flow rate of oil-water mixture Q m The radial pressure difference of the swirl flow, the pipe radius R, the volume water content β, the water phase density ρ w , oil phase density ρ o .

[0048]

[0049] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for measuring oil-water two-phase holdup and flow rate based on cyclone shaping, characterized in that: An oil-water two-phase measuring device based on swirl shaping is used. The oil-water swirl shaping device connected to the pressure-inducing pipe of the measuring device is arranged between the oil-water mixture inlet and the oil-water mixture outlet. The pressure-inducing pipe includes an axial pressure-inducing pipe and a radial pressure-inducing pipe, and the axial pressure-inducing pipe and the radial pressure-inducing pipe are respectively connected to the axial differential pressure measuring system and the radial differential pressure measuring system; The oil-water swirl shaper comprises a swirl shaping blade and a swirl shaping blade outer tube, wherein the oil-water swirl shaper is an elliptical blade type and / or a spiral type, wherein the elliptical blade type has an angle θ of 45-60° and the spiral type has an angle θ of 30-60°; Connect to the oil-water mixture axial differential pressure transmitter through the upstream axial pipe wall pressure guide pipe of the oil-water mixture and the downstream axial pipe wall pressure guide pipe of the oil-water mixture; Connect to the radial differential pressure transmitter of the oil-water mixture through the radial pressure inlet pipe on the downstream wall of the oil-water mixture pipe and the central pressure inlet pipe of the oil-water mixture radial pipe at the designated cross section; When the axial pressure points are arranged, the first pressure taking position is located between 2D-5D upstream of the swirl device, and the second pressure taking position is located between 5D-10D upstream of the swirl device; the radial pressure taking surface is arranged between 1D-5D downstream of the swirl device, and the axial second pressure taking position coincides with the radial pressure taking wall pressure; The measurement method includes the oil-water mixture inlet section, the oil-water swirl shaper, the upstream axial pipe wall pressure pipe of the oil-water mixture, the downstream axial pipe wall pressure pipe of the oil-water mixture, the radial pressure pipe of the downstream pipe wall of the oil-water mixture, the central pressure pipe of the radial pipe of the oil-water mixture, and the axial differential pressure transmitter ΔP of the oil-water mixture z , radial differential pressure transmitter for oil-water mixture ΔP r , the oil-water mixture outlet composition; the oil-water mixture is first shaped by the oil-water swirl shaper, and the uniform dispersed flow or uniform annular flow pattern about the axis is established to establish the flow pattern required for radial and axial pressure difference measurement; it is connected to the axial and radial differential pressure measurement system through the pressure-leading pipeline, and the radial pressure difference between the center tube and the wall at the specified section after the swirl shaping and the axial pressure difference between the two walls at the specified section before and after the swirl shaping are measured respectively, and the relationship between the axial pressure difference and the radial pressure difference and the water content and flow rate are established respectively, so as to realize the measurement of the water content and flow rate of the oil-water two-phase; After the oil-water mixture flows through the cyclone device, the volume water content β of the oil-water mixture is as shown in formula (2): β=A*λ 2 +B*λ+C (2) Where: λ is the radial pressure difference ΔP z and axial pressure difference ΔP r A, B, and C are all constants, obtained through indoor or field experiments; Total flow rate of oil-water mixture Q m As shown in formula (3) Where: Radial flow coefficient α r , pipe radius R, volume water content β, water phase density ρ w , oil phase density ρ o .

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