CN114440959A - Oil-water two-phase measuring device and method based on rotational flow shaping - Google Patents

Abstract

An oil-water two-phase measuring device based on rotational flow shaping comprises an oil-water rotational flow shaper. The straight pipe section required by the invention is greatly shortened, the pressure difference is also greatly reduced, and the invention has excellent adaptability to the conditions of rotary flow and vortex. For two-phase fluid, the swirling device can rectify complex two-phase fluid into a uniformly dispersed flow or annular flow state in the pipe which is symmetrical about an axis, so that the measurement is more convenient, and the method and the device are easier to realize standardization compared with other non-standard differential pressure flow meters because only a simple swirler is used for influencing the measurement of the method.

Description

A kind of oil-water two-phase measuring device and method based on swirl shaping

technical field

The invention belongs to the technical field of two-phase flow flow rate and water content measurement, and in particular relates to an oil-water two-phase measurement method for liquid produced by oil wells in oil fields.

Background technique

Two-phase flow widely exists in modern industrial production and daily life, and two-phase flow in pipelines often occurs in various fields of production processes such as petroleum, chemical, metallurgy, and food. Its parameter detection is important for the rational development and production of resources. Safety and industrial process control are of great significance and have become frontier subjects that have been paid great attention at home and abroad. Therefore, accurate online measurement of parameters of two-phase flow, such as flow rate of each phase, phase holdup, etc., plays an important role in industrial production. However, due to the diverse flow patterns and complex flow mechanism of the two-phase flow, the measurement and research of the two-phase flow are still hot and difficult.

In the oilfield production process, the oil well produced fluid mainly contains oil, associated gas, water, etc. The multiphase flow on the oilfield surface is the two-phase flow of oil and water or the three-phase flow of oil, gas and water in the oilfield surface pipeline. , inclined and vertical. The multiphase pipeline flow on the ground starts from the wellhead of the oil well, and goes through the process of collection, transportation, pressurization, gas-liquid separation, and oil-water separation. rate, gas content and other parameters. The "two-phase" in the present invention refers to the two-phase oil phase and the water phase in the oil field production fluid. Due to the complexity of the oil-water flow, the oil-water two-phase measurement method has great difficulty, and there are currently a variety of two-phase measurement technical routes.

According to the research results at home and abroad, the oil-water two-phase flow measurement schemes can be summarized into two types: one is to measure the mixed-phase flow by using a uniform-phase flow model and a conventional single-phase flow meter, and to calculate the split-phase flow through phase holdup analysis; The separator separates the oil and water and measures the oil and water 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 K.J., Kozma R., etc. have studied various methods for measuring the flow rate of oil-gas-water phase flow, such as capacitive method and thermal method. Cao Xuewen, Kou Jie, Lin Zonghu, etc. summarized and summarized the measurement principles of various multiphase flow flowmeters used in actual production at home and abroad and how to select models for different application conditions. The application of Coriolis force mass flowmeter can simultaneously measure the mass flow and water content of oil-water two-phase flow. Flow measurement has a variety of flowmeters such as volumetric flowmeters, velocity flowmeters, and mass flowmeters.

In the multiphase flow metering technology, the separation method is still the most reliable and accurate technology. For example, Chinese patents ZL200810112558.3 and ZL200710046862.8 all use large containers as a three-phase separation system for oil, gas and water, and then use a single-phase metering method. Because this method separates the oil-gas-water three-phase fluid in the multiphase fluid into single-phase gas and oil and water, and then uses the single-phase flowmeter to measure the flow rate of each phase, so as to avoid factors such as flow pattern change and flow instability. measure the impact. However, in actual multiphase fluid measurement, many fluids cannot be completely separated economically and effectively, and this multiphase measurement brings a lot of troubles.

Therefore, different scholars at home and abroad have summarized and analyzed various combined methods for measuring multiphase flow. So as to realize the three-phase measurement of oil, gas and water, such as ZL201410468193.3 and 200810150257.X, etc. With the progress of related research work, new technologies for multiphase detection continue to emerge. The multi-phase 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 are: waist wheel flowmeter, scraper flowmeter Equal volume flow meters, turbine flow meters, constant velocity flow meters, orifice plates, venturi tubes and other differential pressure flow meters and mass flow meters, etc. The phase holdup adopts a differential pressure 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 flow rate and phase holdup for fusion. One of the most widely used is the fusion of differential pressure sensor and differential pressure sensor. (3) Integrated combination of dual-sensor correlation analysis and phase holdup sensor The most commonly used method is the correlation velocity measurement of dual-ray attenuation sensors, and at the same time, the phase holdup is analyzed by using the attenuation signal. Correlation and holdup analysis are also performed with double venturi tubes. There are also capacitance-related and conductivity-related flow and water content measurements. Different multiphase flow meters are suitable for different media conditions. The interfacial stability and pressure drop of oil, gas, and water three-phase pipe flow vary with the pipe geometry, fluid holdup, fluid pressure, temperature, etc., showing different flow patterns, which are called flow type. Different flow patterns have a greater impact on the accuracy of flow parameter measurement, and the gas phase change in the three-phase flow of oil, gas and water has the greatest impact on the flow pattern. The research of D.Favrat, O.Zurcher. and other researchers on gas-liquid two-phase flow and multiphase flow pattern mainly focuses on the study of fluid flow pattern in horizontal pipes and vertical pipes, and the flow patterns in vertical pipes and horizontal pipes. However, it is still very difficult to apply the prior art for the occasions where the flow rate and phase holdup of the oil well produced fluid fluctuates in a large range and the flow is complicated. At present, there are many measurement methods based on oil well production flow and water cut, but there are generally small measurement range, limited application and high price, which are difficult to meet the actual needs of oilfield production.

Based on the urgency of on-line measurement of oil well production, laboratory and field experiments show that when the oil-water two-phase flow rotates in a spiral shape in the pipe, a swirl pressure difference and an axial differential pressure will be generated. Flow rate and water content are very sensitive. Under a given flow rate, 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 high resolution ability, but more importantly, it adopts the differential pressure measurement technology, and the current differential pressure transmitter is very mature in technology and works stably and reliably , Economically reasonable, suitable for large-scale application.

SUMMARY OF THE INVENTION

In order to overcome the above-mentioned deficiencies of the 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 dispersion flow or an axisymmetric flow pattern based on the oil core-water ring. The axial pressure difference formed before and after the flow shaping device is related to the flow rate and water content, so that the double differential pressure can be used to realize the dual-parameter measurement of water and liquid flow in the oil-water two-phase.

The object of the present invention can also be realized through the following technical measures:

A method for measuring oil-water two-phase content and flow rate based on swirl shaping, which mainly includes an oil-water mixture inlet section, an oil-water cyclone shaper, an upstream axial pipe wall pressure pipe of the oil-water mixture, and a downstream pipe wall of the oil-water mixture. Axial pressure pipe, radial pressure pipe of downstream pipe wall of oil-water mixture, central pressure pipe of oil-water mixture radial pipe, axial differential pressure transmitter ΔP _z of oil-water mixture, radial differential pressure change of oil-water mixture The feeder ΔP _r is composed of the oil-water mixture outlet. The oil-water mixture is first shaped by the oil-water cyclone shaper, and the flow pattern required for radial and axial pressure difference measurement is established with respect to the axisymmetric uniform dispersion flow or uniform annular flow flow pattern. Connect to the axial and radial differential pressure measurement systems through the pressure-inducing pipeline to measure the radial pressure difference between the center tube and the wall at the designated section after swirl shaping, and the axial pressure on the two walls at the designated section before and after swirl shaping. Through the axial pressure difference and radial pressure difference, the relationship between water content and flow rate is established respectively to realize the water content and flow measurement of oil-water two-phase.

The invention utilizes a swirl device, and utilizes a static rotating flow channel to force a rotation for shaping, which increases the scope of application in different occasions, and is not only suitable for laminar flow and wavy laminar flow under low flow velocity, but also for annular flow under high flow velocity. flow and slug flow.

Through the cyclone device, the oil-water mixture with complex flow pattern is arranged into the desired uniform flow pattern about the axis symmetry, and the flow pattern required for radial and axial pressure difference measurement is established.

When the axial pressure-taking points are arranged, the first pressure-taking position is located between 2D-5D upstream of the swirl device, and the first 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 second axial pressure taking position may coincide with the radial pressure taking wall surface.

The swirl vanes in the swirl device selected by the patent of the present invention can be either elliptical vane type or helical type.

The invention discloses an oil-water two-phase measurement method based on the principle of swirl shaping. It can be known from fluid mechanics that the axial pressure difference is caused by the friction along the path during the fluid flow, and 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 , and the ratio between the two is defined as λ. The formula is as follows:

After a large number of indoor and field studies, it is found that when the oil-water two-phase mixture flows through the cyclone device, the ratio λ of the radial pressure difference ΔP _z to the axial pressure difference ΔP _r and the volumetric water content β of the oil-water two-phase mixture have the following relationship :

β=A·λ ² +B·λ+C (2)

Among them, A, B, and C are all constants, which can be obtained through laboratory experiments or field experiments.

At the same time, the total flow Q _m of the oil-water mixture and the radial pressure difference of the swirl, the pipe radius R, the volumetric water content β, the water phase density ρ _w , and the oil phase density ρ _o .

In addition, the radial flow coefficients α _r and D are constants related to the fluid medium, so as long as the designed metering device structure is finalized, the corresponding radial value can be determined through laboratory experiments.

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

Step 1, it can be seen from formula (2) that after the device is processed, as long as the values of the radial pressure difference ΔP _z and the axial pressure difference ΔP _r at a certain section after the swirl flow are measured, the ratio of the two is λ. Substitute into the volume water content β of the oil-water two-phase mixture.

In step 2, the measured water content β is substituted into formula (3), and the relevant constant obtained from the experiment and the oil-water density can be combined to obtain the total flow Q _m of the oil-water mixture, so as to realize the measurement of the total oil-water flow and phase content after degassing.

The invention has the following advantages and characteristics: the required straight pipe section is greatly shortened, the pressure difference is also greatly reduced, and it has excellent adaptability to the conditions of rotating flow and eddy current. For two-phase fluid, the cyclone device can rectify the complex two-phase fluid into a state of uniform dispersed flow or annular flow in the pipe symmetrical about the axis, which is more convenient for measurement, because only a simple cyclone affects the measurement of this method. , so compared with other non-standard differential pressure flow meters, this method and device are easier to achieve standardization.

Description of drawings

In order to illustrate the technical solutions in the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings used in the description of the embodiments, and the accompanying drawings in the following description are only some embodiments of the present invention.

Fig. 1 is a kind of device schematic diagram of the oil-water two-phase measurement method based on swirl shaping;

Fig. 2 is a schematic diagram of the structure of the oil-water cyclone shaper;

Figure 3a is a schematic diagram of the structure of the swirl shaping blade (elliptical blade type and its angle);

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

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

Figure 4b is a schematic diagram of the flow pattern of the oil-water two-phase transformation into annular flow after being shaped by static swirl in a circular pipe;

Fig. 5 The field measurement curve of the axial radial pressure difference ratio λ and β water content;

Fig. 6 Field measured curve diagram of radial pressure difference and flow rate.

The reference numbers are as follows:

1. Oil-water mixture inlet; 2. Oil-water cyclone shaper; 3. Oil-water mixture upstream axial pressure-inducing pipe; 4. Oil-water mixture downstream pipe wall axial pressure-inducing pipe; 5. Oil-water mixture downstream pipe wall radial pressure 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;

2-1 swirl shaping blade; 2-2 swirl shaping blade outer tube.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

Mainly include the following components: 1. Oil-water mixture inlet section, 2. Oil-water cyclone shaper, 3. Oil-water mixture upstream axial 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 mixed liquid radial pipe center pressure pipe, 7 oil-water mixed liquid axial differential pressure transmitter ΔP _z , 8 oil-water mixed liquid radial differential pressure transmitter ΔP _r , 9 oil-water mixed liquid radial differential pressure transmitter The mixture is exported.

The oil-water mixture first enters the oil-water cyclone shaper 2 through the oil-water mixture inlet 1 for shaping, and is arranged into a uniformly dispersed flow pattern that is symmetrical about the axis, and the flow pattern required for radial and axial pressure difference measurement is established. Measurement. The axial pressure difference is connected to the oil-water mixture axial differential pressure transmitter ΔP _z 7 through the upstream axial pipe wall pressure pipe 3 of the oil-water mixture and the downstream pipe wall axial pressure pipe 4 of the oil-water mixture to realize the measurement specification. The purpose of the axial pressure difference between the two sections. In addition, on the specified section, it is connected to the oil-water mixture radial differential pressure transmitter ΔP _r 8 through the oil-water mixture downstream pipe wall radial pressure pipe 5 and the oil-water mixture radial pipe center pressure pipe 6 to realize the measurement designation. Radial pressure difference across the 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 can be substituted into the volume water content β of the oil-water two-phase mixture. Combined with the correlation constant obtained from the experiment and the oil-water density, the total flow rate Q _m of the oil-water mixture can be obtained, and the measurement of the total oil-water flow rate and phase content after degassing can be realized.

The oil-water swirl shaping mixer is composed of a swirl shaping blade 2-1 and an outer tube 2-2 of the swirl shaping blade, which are mainly arranged into (1) uniform dispersion about the axis symmetry as shown in Figure 4a and Figure 4b flow and (2) annular flow, establishing the flow pattern required for radial and axial differential pressure measurement.

Fig. 3 is a schematic diagram of the structure of the swirl shaping blade, the structure selected by the present invention in the indoor and field experiments (a) elliptical blade type, wherein the elliptical blade type angle θ is 45-60, (b) helical type, the spiral rotation The angle θ is 30-60°. In this embodiment, the fluid is first rectified through an elliptical blade, and then secondarily rectified through a helical blade to ensure the output result of the oil-water two-phase. In field use, the staff uses separate elliptical blades and helical blades. No matter how the parameters are adjusted, the measurement results cannot be guaranteed to be accurate. Only when the two are mixed, the final satisfactory results can 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 the helical blade, or a helical blade is connected between two elliptical blades. The oil-water two phases are transformed into measurable final flow patterns after different flow patterns in the circular pipe through static swirl shaping.

Through the measurement, the field measurement curve of the axial radial pressure difference ratio λ and β water content shown in Figure 5 and the field measurement curve diagram of the radial pressure difference and flow shown in Figure 6 are finally obtained. Figure 5 corresponds to the formula of the ratio λ of the radial pressure difference ΔP _z to the axial pressure difference ΔP _r and the volumetric water content β of the oil-water two-phase mixture after the oil-water two-phase mixture flows through the cyclone device:

β=A·λ ² +B·λ+C.

Figure 6 corresponds to the total flow Q _m of the oil-water mixture and the radial pressure difference of the swirl, the pipe radius R, the volumetric water content β, the water phase density ρ _w , and the oil phase density ρ _o .

Although embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, The scope of the invention is defined by the claims and their equivalents.

Claims (6)

1. An oil-water two-phase measuring device based on swirl shaping, characterized in that: comprising an oil-water swirl shaping device. 2 . The oil-water two-phase measuring device based on swirl shaping according to claim 1 , wherein the oil-water swirl shaping device is arranged between the oil-water mixture inlet and the oil-water mixture outlet. 3 . 3 . The oil-water two-phase measuring device based on swirl shaping as claimed in claim 2 , wherein the oil-water swirl shaping device is connected to a pressure pipe. 4 . 4 . The oil-water two-phase measuring device based on swirl shaping according to claim 3 , wherein the pressure-inducing pipe comprises an axial pressure-inducing pipe and a radial pressure-inducing pipe. 5 . 5 . The oil-water two-phase measuring device based on swirl shaping according to claim 1 , wherein the oil-water swirl shaping device is an elliptical blade type and/or a helical type. 6 . 6. a method using the oil-water two-phase measuring device based on swirl shaping as described in any one of claims 1-5, is characterized in that: the oil-water mixture enters the oil-water swirl shaping device to carry out shaping, and finishing A uniform dispersion flow pattern that is symmetrical about the axis is established to establish the flow pattern required for radial and axial differential pressure measurement.

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