Method and device for measuring liquid flow in gas-liquid mixtures

FIELD: oil and gas extractive industry.

SUBSTANCE: method includes separating gas from liquid in the mixture. Liquid is periodically accumulated in calibrated gas separator tank with concurrent by-way of gas into collector and accumulated liquid is pushed out by gas with open pipeline used for draining gas into collector. During pushing away accumulated liquid by gas differential pressure between lower and upper pipeline points is additionally measured. Liquid flow in gas-liquid mixtures is calculated as total of flow of liquid filling calibrating tank, and flow of liquid, carried away by gas from separator, determined from given relation. Method is realized by device, which contains calibrating tank with inlet branch pipe for feeding gas-liquid mixture therein, pipeline for draining gas and pipeline for draining liquid, connected to collector through three-drive valve. Also, following are mounted in separator: level relay-sensor limiting calibrating volume, absolute temperature sensor, absolute pressure sensor and differential pressure sensor between lower and upper separator points. Between lower and upper pipeline points a sensor for measuring differential pressure is mounted. At entrance of pipeline dispersant is mounted for evening gas and liquid speeds.

EFFECT: higher precision.

2 cl, 1 dwg

 

The invention relates to the field of control and metering of gas and liquid in gas-liquid mixtures coming from oil wells.

Known methods of measuring production wells, separating gas from liquid, which accumulate in the tank. In one case, the liquid mass is determined cyclically according to the data obtained from the transducer force (weight)installed capacity [1. USSR author's certificate No. 1652521, E 21 In 47/00, 1991]. In another case, the accumulated liquid away from the tank into a collecting reservoir through a pipeline, in which is installed a flow meter [2. Gesloten. Collection and preparation of oil, gas and water. M., Nedra, 1983, p.45-46, 20].

The known method and device for measuring fluid flow in gas-liquid mixtures coming from oil wells [3. Gsanremo and other Automated measuring system for measuring the flow rate of oil wells. Scientific-technical journal “automation and implementation of telemechanics and communication in the oil industry, No. 1-2, 2001, p.16-18], which also includes the separation of the mixture in the separator for liquid and gas, periodic accumulation of fluid in the tank of the separator and the displacement of gas by measuring the differential pressure when the liquid reaches the lower and upper fixed levels and time filling fixed volumes. The mass flow rate of fluid is STI calculated using the known dependence in accordance with a hydrostatic method of measuring mass [4. Oil and oil products. Methods of measurement of mass. GOST 26976-86].

All known methods of measurement do not take into account fluid flow out of the separator gas. Their implementation requires high quality gas separation, especially in the oil fields with large gas factor.

The technical task of the invention is to improve the accuracy of measurement of liquid flow in gas-liquid mixtures coming from oil wells, by taking into account the flow rate of the liquid carried away by the gas stream from the separator.

To solve the problem in the process of measurement of liquid flow in gas-liquid mixtures coming from oil wells, including the separation of a mixture of liquid and gas, periodic accumulation of fluid in calibrated capacity of the separator while bypass gas into a collecting reservoir and the displacement of fluid accumulated gas in an overlapped pipeline that is intended to discharge gas into a collecting reservoir, and the calculation of fluid flow in gas-liquid mixtures as liquid flow rate, filling the calibrated capacity of the separator, when the displacement of fluid accumulated gas is additionally measured differential pressure ΔP between the lower and upper points of the pipeline serving for discharge of gas into precast the reservoir and fluid flow in gas-liquid mixtures compute the AK is the sum of consumption, G 1liquid filling calibrated capacity of the separator, and flow rate G2liquid carried away by the gas from the separator is determined from the dependencies

where RG- the density of the gas in the working conditions;

pWthe density of the liquid out gas in the work environment;

g - free fall acceleration;

H is the distance between the lower and upper points of the pipeline serving for discharge of gas into a collecting reservoir;

ΔP - differential pressure;

qG- volume flow of gas in the working conditions.

The proposed method can be implemented using devices designed for measuring fluid flow in gas-liquid mixtures coming from oil wells that contain the separator with an inlet pipe to feed it gas-liquid mixture and pipelines serving for discharge through a three-way valve liquid and gas into the reservoir, and sensors to control the filling and the displacement of liquid from the separator parameters that determine the mass flow rate G1fluid accumulated in the separator, and the volume flow qGgas in the working conditions.

To solve the technical problem in the device introduced additional sensor for measuring differential pressure ΔP is between the lower and upper points of the pipeline, used to discharge gas into the reservoir.

The invention is illustrated by the drawing, which shows a diagram of a device for measuring fluid flow in gas-liquid mixtures.

The device shown in the drawing, similar to a device used to measure fluid flow in accordance with a hydrostatic method of measuring mass [3].

The device includes a separator 1 with a calibrated volume V1restricted sensor-relay layer 2, the fixing liquid level at a height of H1sensor 3 absolute temperature sensor 4 absolute pressure sensor 5 differential pressure between the lower and upper points of the separator 1. The separator 1 is equipped with an inlet pipe 6 for feeding it gas-liquid mixture, the pipeline 7 for discharge of gas and pipeline 8 for liquid connected to the collector through a three-way valve 9 with electric drive (known devices excluded site pre-selection of gas, the construction of which does not affect the ability of the invention). The separator is equipped with a sensor 10 for measuring the differential pressure between the lower and upper points of the pipeline 7, at the entrance of which has disperser 11.

Gas-liquid mixture through the inlet pipe 6 is fed to the separator 1, where the liquid is separated from gas and accumulates at the bottom is part of it, gradually filling volume V1limited by the height H1. At this time, the three-way valve 9 closes the exit of fluid from the separator through pipe 8 into the reservoir, but opens the gas outlet and carried away by the gas-liquid separator through the pipe 7 into the reservoir.

After reaching the liquid level H1that is recorded by the sensor-relay layer 2, the command to switch the three-way valve 9 in a position where the gas outlet into the reservoir through the pipe 7 is closed, and the exit of fluid into the reservoir through pipe 8 is open. The liquid due to the energy cumulative separator gas is displaced into the reservoir. While sensors 3 absolute temperature and 4 absolute pressure control the temperature and pressure of the gas in the separator to determine its density in the working conditions.

After displacement of the liquid from the separator, which is recorded by the sensor-relay layer 2 and the sensor 5 differential pressure, three-way valve 9 returns to its original position, and the process is cyclically repeated.

The accumulation of liquid in the separator known hydrostatic method [3, 4] is determined by the mass flow rate G1and its density ρWand when emptying - volumetric gas flow rate qG.

The flow measurement G2liquid out of the separator gas is as follows.

After switching the three-way valve 9 in a position where the gas outlet and carried away by the gas flow of liquid through the pipe 7 into the reservoir is closed, line 7 remains a mixture of gas with liquid of density Rwith:

where mG, mWis the mass of the gas and the liquid, respectively,

VWVGV (V=VW+VG- the volume occupied by the liquid and gas mixture, respectively.

The density of the mixture of pwithremaining in the pipe 7 height H, is determined by the formula (2)

where ΔP is the differential pressure measured by sensor 10;

g - acceleration of free fall.

The mass of the gas mGand liquid mWin volume V of the tube 7 are expressed by the formulas (3) and (4) respectively

Substituting the expression mGand mWfrom formulas (3) and (4) in formula (1) after identical transformations have the formula (5)

where ϕ - volumetric concentration of gas in a locked pipe 7.

From the formula (5) we get the formula (6) to determine ϕ using the known values ρwiththat ρGand ρW.

By definition, the mass flow rate G2the pipe 7 is expressed by the formula (7)

where q2volumetric flow rate in the pipe 7 during the accumulation of liquid in the separator.

Flow q2can be expressed through bulk supplies gas β formula (8)

Under the condition of equality of the velocities of gas and liquid in the pipe 7 during the accumulation of liquid in the separator is the equality (9)

Under this condition, replacing in the formula (8) β ϕ and substituting into it the expression ϕ from the formula (6) have the formula (10)

Substituting the expression of pcfrom the formula (2) in formula (10) we obtain the formula (11)

Substituting the expression for q2from the formula (11) in formula (7) have the formula (12)

For certain values β condition (9) may not be performed [5. Vasami and other Hydrodynamics of gas-liquid mixtures in pipes. M., Nedra, 1969].

To ensure conditions ϕ=β, that is, to equalize the velocities of gas and liquid in the pipe 7, is mounted disperser 11.

Thus, knowing the value of G2you can improve the measurement accuracy of the total flow rate G=G1+G2.

1. Method of measurement of liquid flow in gas-liquid mixtures coming from oil is s wells involving separation of a mixture of liquid and gas, periodic accumulation of fluid in the tank of the separator while bypass gas into a collecting reservoir and the displacement of fluid accumulated gas in an overlapped pipeline that is intended to discharge gas into the reservoir, and the calculation of fluid flow in gas-liquid mixtures as liquid flow rate filling capacity of the separator, characterized in that during the displacement of fluid accumulated gas is additionally measured differential pressure ΔP between the lower and upper points of the pipeline serving for discharge of gas into the reservoir, and fluid flow in gas-liquid mixtures are calculated as the sum of consumption, G1fluid accumulated in the separator, and flow rate G2liquid carried away by the gas from the separator is determined from the dependencies

where RG- the density of the gas in the working conditions;

pWthe density of the liquid out gas in the work environment;

g - free fall acceleration;

H is the distance between the lower and upper points of the pipeline serving for discharge of gas into a collecting reservoir;

ΔP - differential pressure;

qg- volume flow of gas in the working conditions.

2. A device for measuring fluid flow in gas-liquid mixtures, enter the from oil wells, containing the separator with an inlet pipe to feed it gas-liquid mixture and pipelines serving for discharge through a three-way valve liquid and gas into the reservoir, and sensors to control when filled and the displacement of liquid from the separator, parameters that determine the flow of liquid accumulated in the separator, and the gas flow, characterized in that it additionally introduced a sensor for measuring the differential pressure between the lower and upper points of the pipeline serving for discharge of gas into the collector.

3. The device according to claim 2, characterized in that it is equipped with a disperser installed at the inlet of the pipeline serving for discharge of gas into the collector.



 

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