CN101666770A - Device and method for measuring crude oil with low air void - Google Patents

Abstract

The invention discloses a low gas content crude oil measuring device and method, belonging to the technical field of fluid measurement. The crude oil measurement device with low gas content includes a metering pipeline, a capacitive sensor at the front end of the metering pipeline, a mixer in the middle of the metering pipeline, a Coriolis mass flowmeter and a pressure sensor at the back end of the metering pipeline, an A/D conversion card and a computer. Capacitance sensor, Coriolis mass flow meter and pressure sensor are all connected to computer through A/D conversion card. The invention also provides a measuring method adopted by the device. The invention has the advantages of small size, simple structure, convenient installation, many measurement parameters, high parameter detection precision, good real-time performance, reliability and easy realization. It is suitable for the measurement of crude oil with low gas content in oil field.

Description

Device and method for measuring crude oil with low gas content

technical field

The invention belongs to the technical field of fluid measurement, and in particular relates to a device and method for measuring the phase holdup of crude oil with low gas content and the flow rate of each phase.

Background technique

Crude oil is a typical multiphase flow, generally including oil, gas and water three-phase substances. The three phases of oil, gas and water interact in the flow process, and it is very difficult to detect the flow rate of the separated phases. However, for the rational development of oil fields, the oil production, water production and gas production of each oil well must be mastered. At present, most oil fields use the separation metering method to measure the phase-separated flow rate of crude oil. Separation measurement method is generally divided into complete separation method and partial separation method.

The complete separation method is a traditional metering method in the oil field. This method uses a high-efficiency metering separator to separate crude oil into oil phase, water phase and gas phase, and then uses each single-phase measuring instrument or device to obtain the respective contents of the three components, and then mix and transport To the pumping station for production processing. The complete separation method converts the crude oil phase flow measurement into a single-phase fluid flow measurement, which has the advantages of reliable operation, high measurement accuracy, wide measurement range, and is not affected by changes in the flow state of crude oil. However, the oil and water separation effect involved in this method is easily affected by various factors, and it is difficult to achieve a high degree of separation, which will affect the accuracy of single-phase measurement. Moreover, the separation equipment used in this method is bulky, requires a certain amount of time for separation, and cannot be measured on-line, thereby greatly restricting production efficiency.

Partial separation methods include fractionation and phase separation and simple separator methods. The flow and phase separation method first divides a part of the fluid through a distributor, and then uses a separator to separate this part of the three-phase fluid into a single-phase gas and a single-phase liquid, and then uses a single-phase gas flowmeter and a single-phase liquid flowmeter for measurement. And convert it into the flow rate and composition of the measured fluid according to the proportional relationship, and finally return this part of single-phase gas and single-phase liquid to the flow pipeline. The problem with this method is that the gas-liquid ratio of the sampling part is often different from the gas-liquid ratio in the original flow, and the sampling ratio is easily affected by flow patterns and flow fluctuations. The simple separator method is to use a small gas-liquid separator to pre-separate the three-phase flow to obtain a path dominated by the gas phase and a path dominated by the liquid phase. Three-phase flow of oil, gas and water, the measured fluids are mixed together and sent back to the original pipeline. This separation method reduces the volume of the equipment to a certain extent and improves the real-time performance of measurement. Therefore, most of the multiphase flowmeter products introduced in recent years adopt the partial separation method. However, the gas-liquid separation effect of the partial separation method is poor, and a certain amount of gas is often mixed in the liquid phase. The mixed gas has a great impact on the measurement accuracy of the liquid phase flow rate, and also affects the accurate measurement of the gas flow rate.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned deficiencies of the prior art and provide a measurement device and method for crude oil with low gas content. The device provided by the invention has the advantages of small volume, simple structure, convenient installation, many measurement parameters, high parameter detection precision, good real-time performance, reliability and easy realization. It is suitable for the measurement of crude oil with low gas content after separation of crude oil in oil field.

For this reason, the present invention adopts following technical scheme:

A crude oil measurement device with low gas content, comprising metering pipeline (1), capacitance sensor (2), flow mixer (3), Coriolis mass flowmeter (4), pressure sensor (5), A/D conversion card ( 6), the computer (7), the metering pipeline (1) is provided with a capacitive sensor (2), a flow mixer (3), a Coriolis mass flowmeter (4), a pressure sensor (5), and an A/D conversion card in sequence (6) is connected with capacitance sensor (2), Coriolis mass flow meter (4), pressure sensor (5), and computer (7) is connected with A/D conversion card (6).

The present invention simultaneously provides a measurement method adopted by the above-mentioned low gas content crude oil measurement device, comprising the following steps:

确定管截面上第j个像素的灰度值，式中，f_j-第j个像素的灰度值，N-电容传感器提供的测量一个管截面上电容分布时的电容个数(例如，对于具有n个电极的电容传感器，

c_i-第i个测量电容的归一化值，由电容传感器测量得到，s_ij-第j个像素相对于第i个测量电容值的权重系数(即灵敏度)，具体数值通过有限元分析并辅助实际测量校正获得。然后，根据

计算低含气率原油的体积含气率，式中，φ_g-低含气率原油的体积含气率，A_j-第j个像素的面积，A-测量管道的截面面积。The tube section is divided into N pixels, and the capacitive sensor measures the capacitance distribution on the tube section, and according to

Determine the gray value of the jth pixel on the tube section, where, f _j - the gray value of the jth pixel, N - the number of capacitances provided by the capacitive sensor when measuring the capacitance distribution on a tube section (for example, for capacitive sensor with n electrodes,

c _i - the normalized value of the i-th measured capacitance, which is measured by the capacitive sensor, s _ij - the weight coefficient (ie sensitivity) of the j-th pixel relative to the i-th measured capacitance value, the specific value is analyzed by finite element analysis and Auxiliary actual measurement corrections are obtained. Then, according to

Calculate the volumetric gas content of crude oil with low gas content, where, φ _g - the volume gas content of low gas content crude oil, A _j - the area of the jth pixel, A - the cross-sectional area of the measuring pipeline.

计算液体的密度，式中，ρ_l-液体的密度，ρ_m-低含气率原油的混合密度，由科氏质量流量计测量得到。然后，根据

计算体积含油率，根据φ_w＝1-φ_o计算体积含水率，式中，φ_o、φ_w-分别为低含气率原油的体积含油率和体积含水率，ρ_o、ρ_w-分别为温度T和压力P下纯原油、纯水的密度。Calculate the gas density ρg according to the temperature T measured by the Coriolis mass flowmeter and the pressure _P measured by the pressure sensor, and according to

Calculate the density of the liquid, where, ρ _l - the density of the liquid, ρ _m - the mixed density of crude oil with low gas content, measured by a Coriolis mass flowmeter. Then, according to

Calculate the volumetric oil content, and calculate the volumetric water content according to φ _w = 1-φ _o , where φ _o , φ _w - are the volumetric oil content and volumetric water content of crude oil with low gas content, respectively, ρ _o , ρ _w - respectively Density of pure crude oil and pure water at temperature T and pressure P.

计算低含气率原油的体积流量，式中，Q_v-低含气率原油的体积流量，Q_m-低含气率原油的质量流量，由科氏质量流量计测量得到。according to

Calculate the volume flow rate of crude oil with low gas content, where, Q _v - the volume flow rate of crude oil with low gas content, Q _m - the mass flow rate of crude oil with low gas content, measured by Coriolis mass flowmeter.

According to Q _vg ＝ Q _v φ _g 、 Q _vo ＝ Q _v φ _o 、 Q _vw ＝ Q _v φ _w Calculate the volume flow rate of gas, oil and water respectively, according to Q _mg ＝ Q _vg ρ _g 、 Q _mo ＝ Q _vo ρ _o , Q _mw = Q _vw ρ _w respectively calculate the mass flow rate of gas, oil and water.

The beneficial effects and advantages of the present invention are that there is no need to use a high-efficiency gas-liquid separator for gas-liquid separation, a mixer is used to stir crude oil with low gas content into a homogeneous flow, and a combination of a mixer and a Coriolis mass flowmeter is used to measure low gas content. The oil content of crude oil and the phase flow of oil, gas and water. Using Coriolis mass flowmeter to measure mass flow rate, mixing density and oil content does not require complete separation of oil-water two-phase, which solves the problem of complete separation of oil-water two-phase in oil-gas-water three-phase flow measurement based on complete separation method problem. The fluid to be measured is stirred into a homogeneous flow by using a mixer, so that the Coriolis mass flowmeter can measure low-gas-containing media, and the problem of poor separation effect of the gas-liquid separator is solved. The device has the advantages of simple structure, high parameter detection precision and easy realization. It is suitable for the measurement of crude oil with low gas content after separation of oilfield production fluid.

Description of drawings

The accompanying drawing is a schematic structural diagram of a crude oil measurement device with low gas content.

Detailed ways

The crude oil measuring device with low gas content has a metering pipeline (1), on which a capacitance sensor (2), a flow mixer (3), a Coriolis mass flowmeter (4), and a pressure sensor (5) are sequentially arranged on the metering pipeline (1) , the A/D conversion card (6) is connected to the capacitance sensor (2), the Coriolis mass flow meter (4), and the pressure sensor (5), and the computer (7) is connected to the A/D conversion card (6).

The present invention will be further described below by way of examples.

After the oilfield production fluid is preliminarily separated by the gas-liquid separator, crude oil with low gas content enters the metering pipeline 1, and the capacitance sensor 2 collects the capacitance distribution on the pipeline section, and sends the capacitance measurement signal to the computer 7 through the A/D conversion card 6 . Since the medium to be measured contains gas, the gas is likely to form large bubbles or gas bombs in the pipeline, thereby reducing the measurement accuracy of the Coriolis mass flowmeter. At the same time, due to the poor oil-water separation effect, crude oil generally contains a certain amount of water. Water-containing crude oil may have a phase interface, so that the oil and water phases are in a separated flow state. This flow state reduces the density measurement accuracy of the Coriolis mass flowmeter, thereby reducing the calculation accuracy of the oil content. Therefore, in the present invention , the fluid first passes through the flow mixer 3, and the flow mixer 3 makes the fluid mix evenly into a homogeneous flow. The Coriolis mass flowmeter 4 measures the mass flow, mixing density and temperature of the fluid, and the measured mass flow, mixing density and temperature signals are sent to the computer 7 through the A/D conversion card 6 . The pressure sensor 5 is used to detect the pressure of the fluid and convert the pressure signal into a standard electrical signal and send it to the computer 7 through the A/D conversion card 6 . A storage module is provided in the computer 7 to store data such as density values of pure oil, gas, and pure water at different temperatures and pressures, and weight coefficients (ie, sensitivity) of each capacitance value measured by the capacitance sensor. The computer 7 performs real-time processing to obtain the phase-separated holdup and phase-separated flow rate of crude oil with low gas content.

It should be pointed out that the flow state of crude oil is relatively complicated. Although the gas-liquid separator has been preliminarily separated, the separated liquid still contains some gas. When the gas content of the liquid to be tested is less than 5%, the bubbles in the liquid are small and less, and the bubbles have little influence on the measurement accuracy of the Coriolis mass flowmeter. However, when the gas content of the liquid to be tested exceeds 5%, the air bubbles in the liquid become larger, and the measurement accuracy of the mass flowmeter decreases significantly. At the same time, the crude oil in the fluid (that is, liquid medium, or oil-water mixture) also exists in different states. When the water content of the liquid is low, the liquid is in a dispersed flow pattern (that is, water exists in the continuous phase of the oil in the form of bubbles), at this time, the water content calculated according to the density measurement value of the Coriolis mass flowmeter is more accurate , however, when the water content of the liquid is not much different from the oil content, the liquid is in a separate flow pattern (that is, oil and water flow at different speeds), at this time, the density calculated according to the measured value of the Coriolis mass flowmeter The moisture content accuracy is reduced. During design, a mixer is used to stir crude oil with low gas content into a homogeneous flow.

In addition, the Coriolis mass flowmeter is a direct mass flowmeter, which can directly measure mass flow, density and temperature, and has the advantages of high precision, good repeatability, wide range ratio, simple internal structure, and no moving parts.

The specific measurement model and solution scheme are as follows:

1. Gas fraction measurement model

${\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\underset{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}\frac{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}}{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}<span\; class="notranslate">\; \%</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}<span\; class="notranslate">\; /</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

A_j-第j个像素的面积，A-测量管道的截面面积，f_j-第j个像素的灰度值，c_i-第i个测量电容的归一化值，由电容传感器测量得到，s_ij-第j个像素相对于第i个测量电容值的权重系数(即灵敏度)，具体数值通过有限元分析并辅助实际测量校正获得。Among the above formulas, φ _g -volume gas content of crude oil with low gas content, N-capacitance sensor provides the number of capacitances when measuring the capacitance distribution on a tube section (for example, for a capacitance sensor with n electrodes,

A _j - the area of the jth pixel, A - the cross-sectional area of the measuring pipe, f _j - the gray value of the jth pixel, _ci - the normalized value of the i-th measured capacitance, which is measured by the capacitive sensor, s _ij - the weight coefficient (ie sensitivity) of the jth pixel relative to the ith measured capacitance value, the specific value is obtained through finite element analysis and auxiliary actual measurement correction.

2. Oil content measurement model

${\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}}{{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

In the above formulas, φ _o - the volumetric oil content of crude oil with low gas content, ρ _o , ρ _g , ρ _w - the densities of pure crude oil, gas and pure water at temperature T and pressure P respectively, ρ _l - the density of liquid Density, ρ _m - the mixed density of crude oil with low gas content, measured by Coriolis mass flowmeter.

3. Moisture content measurement model

φ _w ＝1-φ _o (5)

In the formula, φ _w -volume water content of crude oil with low gas content.

4. Phase separation flow measurement model

${\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; v</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}{{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

Q _{v g} ＝ Q _v φ _g (7)

Q _vo ＝ Q _v φ _o (8)

Q _vw ＝ Q _v φ _w (9)

Q _mg = Q _vg ρ _g (10)

Q _mo = Q _vo ρ _o (11)

Q _mw = Q _vw ρ _w (12)

In the above formulas, Q _v - the volume flow rate of crude oil with low gas content, Q _m - the mass flow rate of crude oil with low gas content, measured by Coriolis mass flowmeter, Q _vg , Q _vo , Q _vw - respectively , the volume flow of pure crude oil and pure water, Q _mg , Q _mo , Q _mw - are the mass flow of gas, pure crude oil and pure water respectively.

Claims (2)

1. A crude oil measuring device with low gas content, characterized in that it has a metering pipeline (1), on which a capacitive sensor (2), a flow mixer (3), and a Coriolis mass flow rate are successively arranged on the metering pipeline (1). Meter (4), pressure sensor (5), A/D conversion card (6) is connected with capacitance sensor (2), Coriolis mass flow meter (4), pressure sensor (5), and computer (7) is connected with A/D Conversion card (6) links to each other. 2. A measuring method adopted by the low gas content crude oil measuring device according to claim 1, characterized in that it comprises the following steps: (1) Divide the tube section into N pixels, and the capacitive sensor measures the capacitance distribution on the tube section, and according to $f_j=\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{c}_i{\mathrm{the\; s}}_{\mathrm{ij}}/\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{\mathrm{the\; s}}_{\mathrm{ij}}$ Determine the gray value of the jth pixel on the tube section, where, f _j - the gray value of the jth pixel, N - the number of capacitances provided by the capacitive sensor when measuring the capacitance distribution on a tube section (for example, for capacitive sensor with n electrodes, $N=\frac{\mathrm{no}(\mathrm{no}-1)}{2}),$ c _i - the normalized value of the i-th measured capacitance, which is measured by the capacitive sensor, s _ij - the weight coefficient (ie sensitivity) of the j-th pixel relative to the i-th measured capacitance value, the specific value is determined by finite element analysis and Auxiliary actual measurement corrections are obtained. Then, according to ${\mathrm{\&phi;}}_g=[1-\left(\underset{j=1}{\overset{N}{\mathrm{\&Sigma;}}}{f}_j\frac{A_j}{A}\right)]\&times;100\%$ Calculate the volumetric gas content of crude oil with low gas content, where φ _g - the volumetric gas content of low gas content crude oil, A _j - the area of the jth pixel, and the cross-sectional area of the measurement pipeline on A. (2) Calculate the gas density ρg according to the temperature T measured by the Coriolis mass flowmeter and the pressure _P measured by the pressure sensor, and according to ${\mathrm{\&rho;}}_i=\frac{{\mathrm{\&rho;}}_m-{\mathrm{\&rho;}}_g{\mathrm{\&phi;}}_g}{1-{\mathrm{\&phi;}}_g}$ Calculate the density of the liquid, where, ρ _l - the density of the liquid, ρ _m - the mixed density of crude oil with low gas content, measured by a Coriolis mass flowmeter. Then, according to ${\mathrm{\&phi;}}_o=\frac{{\mathrm{\&rho;}}_i-{\mathrm{\&rho;}}_w}{{\mathrm{\&rho;}}_o-{\mathrm{\&rho;}}_w}$ Calculate the volumetric oil content, and calculate the volumetric water content according to φ _w = 1-φ _o , where φ _o , φ _w - are the volumetric oil content and volumetric water content of crude oil with low gas content, respectively, ρ _o , ρ _w - respectively Density of pure crude oil and pure water at temperature T and pressure P. (3) According to $Q_v=\frac{Q_m}{{\mathrm{\&rho;}}_m}$ Calculate the volume flow rate of crude oil with low gas content, where, Q _v - the volume flow rate of crude oil with low gas content, Q _m - the mass flow rate of crude oil with low gas content, measured by Coriolis mass flowmeter. (4) According to Q _vg = Q _v φ _g , Q _vo = Q _v φ _o , Q _vw = Q _v φ _w respectively calculate the volume flow rate of gas, pure crude oil and pure water, according to Q _mg = Q _vg ρ _g , Q _mo = Q _vo ρ _o , Q _mw = Q _vw ρ _w respectively calculate the mass flow rate of gas, pure crude oil, and pure water.