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

FIELD: oil extractive industry.

SUBSTANCE: mixture is separated on liquid and gas in separator. Liquid is periodically collected and forced away by gas while measuring absolute pressure and gas temperature in separator tank near upper and lower fixed liquid levels, and times of forcing away of fixed liquid volume. Additionally measured are absolute pressure and temperature in moment when liquid reaches intermediate fixed level. Then liquid is forced from intermediate fixed level to lower fixed level separator is switched off from well, and mass loss of gas is calculated from provided relation. Device for realization of method consists of separator with feeding pipe, in which a three-drive valve is mounted, and draining pipe, which through said valve is connected to liquid outlet channel and to gas outlet channel. Separator is provided with sensors of temperature and pressure and sensors of upper, intermediate and lower levels, mounted in such a manner, that they separate fixed volumes between each other in separator tank, in case of equality of which calculations are simplified.

EFFECT: higher precision.

2 cl, 1 dwg

 

The invention relates to the measurement of gas flow in gas-liquid mixtures coming from oil wells.

A known method of measuring the gas flow in gas-liquid mixtures coming from oil wells [1. Gsanremo and others, 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]. The method involves 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 absolute pressure and temperature of gas in the tank of the separator at the upper and lower fixed fluid levels, and time displacement fixed volume of liquid. The volumetric gas flow rate is calculated from the known dependence in accordance with the method PVT”.

There is a method associated with use for measuring gas flow q0method PVT [2. “Automating production of oil wells”, M., Nedra, 1975, s-96], leads to the following errors:

Δq1methodological error due to the inability to determine with sufficient accuracy the values of the volume is occupied by gas in the entire system, including the inlet pipe, the separator and the discharge pipe, and its weight in the initial moment of time;

Δ 2methodological error due to the variability of the absolute pressure in the separator (in the devices described in [1], the calculation formula for q0a similar formula described in [2, page 96] for a particular case when Pa=const). The condition of constancy of the absolute pressure is practically impossible [2, page 94];

Δq3methodological error due to the variability of the absolute gas temperature T in the interval.

The technical task of the invention is to increase the measurement accuracy by eliminating errors caused by the inability to determine with sufficient accuracy the values of the volume occupied by the gas throughout the system, and variability in the separator absolute pressure and absolute temperature of the gas.

To solve technical problems in the measurement of gas flow in gas-liquid mixtures coming from oil wells, including the separation of a mixture of liquid and gas separator, the periodic accumulation of fluid and the displacement of gas by measuring the absolute pressure and temperature of gas in the tank of the separator at the upper and lower fixed fluid levels, and time displacement fixed volume of fluid, and calculating the volumetric flow of gas, additional measures absolute pressure and temperature at the moment of achievement of the LM is bone intermediate fixed level, moreover, the displacement of fluid from the intermediate fixed level to the lower fixed level cutoff separator from the wells, and the mass flow rate of gas, reduced to standard conditions, calculated from dependencies

V=V2=V3- the calibrated values of the volume of the separator between fixed levels (upper and intermediate, intermediate, and lower);

ρ1- the density of the gas at the start of the displacement of fluid from the upper fixed level;

ρ2- gas density at the time of displacement liquid to the intermediate fixed level;

ρ3- gas density at the time of displacement liquid to the lower fixed level;

t2-t1the time displacement of fluid from the upper fixed to an intermediate level fixed level.

This structural scheme of the device for implementing the method is similar to that in the known devices [1], containing a separator with a calibrated displacement between the marks of the upper and lower fixed levels, the three-way valve at the outputs of the separator gas and liquid level sensors to generate signals when the liquid reaches a fixed level, the absolute pressure sensor and the sensor of the absolute temperature.

The solution of a technical problem in the device additionally introduced the three-way valve with actuator to turn off the separator from the well, and in the separator is an additional sensor intermediate fixed level, dividing the calibrated volume between the marks of the upper and lower fixed levels on two fixed volume.

Known schemes excluded the pre-selection of gas, the construction of which does not affect the ability of the proposed method of measurement.

The invention is illustrated by the drawing, which shows a diagram of the device for measuring the average mass flow of gas.

The device consists of a separator 1 with a supply pipe 2, which features a three-way valve 3 to connect the separator to the wells, and the discharge pipe 4 with a three-way valve 5. A suction pipe 4 through the valve 5 is connected to the channel 6 output fluid (residence permit) and to the channel 7 gas outlet (VG) of the separator 1. The separator is equipped with sensors 8, 9 and 10 of the upper, intermediate and lower levels, and sensors 11 and 12 temperature and pressure in the separator. The sensors of the levels are set so that between the separating capacity of the separator is equal to a fixed volume, and three-way valves are equipped with electric.

Ow G as follows.

Gas-liquid mixture from the wells through a three-way valve 3 and the inlet pipe 2 is fed to the separator 1, where the gas is separated from the liquid which collects in n the sung part of the separator, gradually filling its volume. At this time, the second three-way valve 5 closes the exit of fluid (residence permit) from the separator, but opens the gas outlet (VG) from the separator through the channel 7 and the outlet pipe 4 in the header.

After reaching the liquid level above H3that is recorded by the sensor 8, the command to the switching valve 5 in a position where the output of the gas in the manifold is closed, and the output of the fluid in the collector is open. The liquid due to the energy cumulative separator gas begins to be forced out into the reservoir.

At time t1reduce the liquid to the level of H3(recorded by the sensor 8 level switch), starts the flow measurement gas G, which ends at the point (time t3) reduce the liquid to the level of H1(recorded by the sensor 10).

In the process of gas flow measurement at time t2by reducing the liquid to the intermediate level of the H2(recorded by the sensor 9) tap 3 command is issued on the overlap of the pipe 2, while the well is connected to the collector.

After emptying of the separator from the liquid the command to the valves 3 and 5 to switch their positions, and the accumulation of fluid in the separator begins again.

The process is cyclically repeated.

At time t1in volume V4above: pipe 7+ separator + pipe 8, azapo the United liquid, accumulated gas mass

where ρ1- gas density at time t1determined measured values of the absolute pressure Pandin the separator sensor 12 and the absolute temperature t of the sensor 11 by the well-known formula

where ρabout- gas density at standard conditions;

Pathe value of absolute pressure;

T is the absolute temperature;

PaboutTaboutvalues of absolute pressure and absolute temperature at standard conditions, respectively.

During displacement of fluid from the volume V3equal to t2-t1in the separator will flow some mass of the gas due to the measured mass flow of the gas G, and at the same time, the volume of the system V4added volume V3(calibrated in advance). Therefore, we can write:

where ρ2- gas density at time t2determined by the sensors 11 and 12 (calculated by the formula 2).

At time t2switches the three-way valve with actuator K1 position: separator inlet locked and the gas-liquid mixture enters the manifold. Allowing inflow of gas in the volume V4+V3is interrupted, and accumulated in the volume of gas viesnyaetsya liquid V 2(also calibrated in advance), filling it with gas before time t3i.e. you can write:

or, if the equality V3=V2=V,

where ρ3- gas density at time t3determined by the sensors 11 and 12.

Deciding together (1), (3) and (5), we obtain the algorithm for determining the mass flow rate of gas G(7):

ρ1V4+G(t2-t1)=ρ3V4+2ρ3V

G(t2-t1)=ρ3V41V4+2ρ3V

G(t2-t1)=ρ2V42V-ρ1V4

31)V4+2ρ3V=(ρ21)V42V

1. A method of measuring the gas flow in gas-liquid mixtures coming from oil wells, including the separation of a mixture of liquid and gas separator, the periodic accumulation of fluid and the displacement of gas by measuring the absolute pressure and temperature of gas in the tank of the separator at the upper and lower fixed fluid levels and time displacement fixed volume of fluid and the calculation of gas flow, characterized in that it further measure absolute pressure and temperature of the tour at the moment of reaching the liquid intermediate fixed level, moreover, the displacement of fluid from the intermediate fixed level to the lower fixed level cutoff separator from the wells, and the mass flow rate of gas, reduced to standard conditions, calculated from dependencies

where V=V2=V3- the calibrated values of the volume of the separator between fixed levels (upper and intermediate, intermediate, and lower);

ρ1- the density of the gas at the start of the displacement of fluid from the upper fixed level;

ρ2- gas density at the time of displacement liquid to the intermediate fixed level;

ρ3- gas density at the time of displacement liquid to the lower fixed level;

t2-t1the time displacement of fluid from the upper fixed to an intermediate level fixed level.

2. Device for measuring the mass flow of gas containing a separator with a calibrated displacement between the marks of the upper and lower fixed levels, the three-way valve at the outputs of the separator gas and liquid level sensors to generate signals when the liquid reaches a fixed level, the sensor absolute pressure and absolute temperature sensor, characterized in that, to increase exactly what ti measurement, in the device additionally introduced the three-way valve with actuator to turn off the separator from the wells, and the separator has an additional sensor intermediate fixed level, dividing the calibrated volume between the marks of the upper and lower fixed levels on two fixed volume.



 

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