RU2519236C1 - Method for determining parameters of oil-gas-water flow - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: method involves separation of oil-gas-water fluid contained in a measuring cylinder using chemical reagents for oil and water with gas emission, measurement of height of liquid column, hydrostatic pressure, emptying of the measuring cylinder, measuring current values of differential pressure and levels of oil-gas-water fluid, oil-water fluid, oil, calculation of oil and water density. At that, volume content of water is calculated by a mathematic formula, and weight content of water is calculated as difference between the value of differential pressure of water in the measuring cylinder and the value of differential pressure of oil-water fluid in the measuring cylinder.

EFFECT: increased measurement accuracy for determination of parameters of oil-gas-water mix.

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Description

The invention relates to the field of oil production and can be used to work as part of measuring installations and transmitting data on the parameters of the oil and gas stream to the computing unit of the measuring installation to adjust the data involved in calculating the production rate of oil wells.

A known method for determining the water cut of a liquid in the production of oil wells, which consists in the fact that a representative sample of the liquid contained in a vertical cylindrical vessel is adjusted by sedimentation, treatment with chemicals and heating to a state of at least incomplete separation into oil and water, and the height of the liquid column is measured , hydrostatic pressure, and then in the process of emptying the specified vertical vessel, continuous measurements of hydrostatic pressure and the height of the liquid column are made [RU 2396427 C2, IPC E21B 47/10, G01N 3/36 (2006.01)]. The density of water and oil in the composition of the liquid is determined as the quotient of the difference between the maximum and current drops in hydrostatic pressure and the corresponding difference in the heights of the liquid column at the beginning and end of the discharge. Accumulate an array of data, build dependency graphs. The selected values of the densities of water and oil determine the mass water cut of well production.

However, the known method does not provide the required metrological accuracy of measurements, since the error of the interfacial level gauge (microwave) depends on the correct setting of many parameters (in particular, dielectric constant), which complicates the setup and significantly affects the error.

The problem to which the claimed technical solution is directed is to develop a method for measuring the parameters of an oil and water mixture, taking into account modern technological requirements.

In the implementation of the proposed technical solution, the problem is solved by achieving a technical result, which consists in increasing the accuracy of measuring the parameters of the oil and water mixture in pressurized collection systems.

The specified technical result is achieved by the fact that the method for determining the parameters of the oil and gas stream contained in the measuring cylinder, equipped with reinforcing piping and equipped with differential sensors, an overpressure sensor, a temperature sensor and a microcontroller, provides for the preliminary installation in the microcontroller of the required level of the oil and water mixture in the measuring cylinder, the process of filling a measuring cylinder with an oil and water mixture, density calculation of the oil and water mixture in the measuring cylinder at the end of the increase in the pressure drop of the lower level, calculating the current values of the levels of the oil and water mixture in the measuring cylinder, comparing the calculated current values of the levels of the oil and water mixture with a predetermined one, and if the values of the current level and the predetermined stop supply of the oil and gas mixture to the measuring cylinder to equalize the density of the oil and water mixture along the height of the measuring cylinder, the oil and gas are mixed mixture with the simultaneous process of the exit of bubble gas until the oil-water liquid is in the measuring cylinder, then the pressure drops of the lower and upper level sensors are measured and, if the pressure drops are equal, the density and level of the oil-liquid are calculated, then the chemical is supplied and the oil-water is mixed for its separation into oil and water, while the microcontroller calculates the end of growth and the drop in the differential pressure sensors of the lower and at the highest levels, it calculates and remembers the density of water and oil under operating conditions, after which the contents of the measuring cylinder are emptied, the density of the current oil level is calculated by the microcontroller, and if this value is equal to the oil density measured under operating conditions, the emptying of the measuring cylinder is stopped, in which oil will remain under operating conditions, calculate the oil level in the measuring cylinder, determine the water level as the difference between the level of the oil-water mixture and the level oil, water pressure drop is determined as a difference value between the values of water pressure drop in the measuring cylinder and the differential oil pressure, wherein the volume content of water is calculated by the formula:

$$W_o=\frac{N_{\mathrm{at}}}{N{}_{\mathrm{well}}}\times \mathrm{one\; hundred}\%,$$

where: Н _в - water level in the measuring cylinder, Н _ж - water-oil liquid level in the measuring cylinder, and the mass content of water is calculated by the formula:

$$W=\frac{d\rho {}_{\mathrm{at}}}{d\rho {}_{\mathrm{well}}},$$

where: dρ _in - the value of the differential pressure of water in the measuring cylinder;

dρ _W - the value of the differential pressure of the oil-liquid in the measuring cylinder.

The inventive method has a metrological advantage, which consists in a more accurate determination of the parameters of the oil and water mixture, due to the use of differential pressure sensors compared to the interphase level gauge.

Also, the error of the interphase level meter (microwave) depends on the correct setting of many parameters (in particular, the dielectric constant), which complicates the setup and significantly affects the error. Using differential pressure sensors, it is possible to measure both the minimum and maximum levels with the same minimum error (which ensures the compactness of the device), and for an interphase level gauge the error depends on the height (a satisfactory error occurs from 2 meters of height and above).

The drawing shows a General scheme for determining the parameters of oil and gas flow. The numbers indicate: 1 - nozzle, 2 - input line, 3 - microcontroller, 4 - input line solenoid valve 2, 5 - input line choke 2, 7 - measuring cylinder, 8 - hemisphere surface mounted at the top of the measuring cylinder 7, 9 - differential pressure sensor, 10 - output line solenoid valve, 11 - differential pressure sensor of the lower 11 level, 12 - pipe, 13 - chemical agent dispenser, 14 - pump, 15 - overpressure sensor, 16 - output line choke 17, 18 - pipe, 19 - line (pipeline) connecting the upper part be measuring the cylinder 7 with the lower part, 20 - upper level of the differential pressure sensor 21 - chemical agent supply pipe, 25 - temperature sensor.

The method is as follows.

The command "start" of the microcontroller 3 opens the electromagnetic valve 4, while the electromagnetic valve 10 is closed. The oil-gas-water mixture from the sampler through a pipe connected to the pipe 1, through the inlet line 2 through the electromagnetic valve 4 through the throttle 5 through the supply line 6 enters the surface of the hemisphere 8, spreads along it and flows down the walls of the measuring cylinder 7. This reduces the interference , when measuring the differential pressure sensors 9, 11, 20 during the filling process. The throttle 5 is used to manually set the filling speed of the measuring cylinder 7 oil-gas mixture. The pipe 12 of the measuring cylinder 7 is connected by a pipe to the separator of the measuring installation to equalize the excess pressure between the measuring cylinder 7 and the separator of the measuring installation.

An increase in the level in the measuring cylinder 7 leads to an increase in the differential pressure of the sensor 11. When the level of the oil and water mixture in the measuring cylinder 7 reaches the level of H ₂ , the increase in the differential pressure of the sensor 11 stops. The microcontroller 3 calculates the end of the growth of the differential pressure and calculates the density of the oil-water mixture ρ _s in the measuring cylinder 7 by the formula (1):

$${\rho }_{\mathrm{from}}=\frac{d\rho {}_2}{g\cdot \mathrm{<figure-callout\; id="2"\; label="H"\; filenames="00000016.png"\; state="\{\{state\}\}">H</figure-callout>}{}_2},$$

Where:

ρ _{with the} density of the oil and gas mixture in the measuring cylinder 7;

dρ ₂ - pressure drop of the sensor level 11 H ₂ in the measuring cylinder 7;

g is the acceleration of gravity;

Н ₂ is the level of the oil and gas mixture in the measuring cylinder 7. Upon completion of the measurement of the density of the oil and gas mixture ρ _s calculated by the formula (1), the microcontroller 3 calculates the current value of the levels of H ₁ , _{2 ... n} oil and gas mixture in the measuring cylinder 7 by the formula (2) :

$$H_{\mathrm{1,2}...n}=\frac{d{\rho }_{\mathrm{1,2}...n}}{g\cdot {\rho }_c},$$

Where:

H _{1,2 ... n} - the current values of the levels of oil and gas mixture in the measuring cylinder 7;

dρ ₁ , _{2 ... n} - pressure drops of the sensor 9 levels H ₁ , _{2 ... n} in the measuring cylinder 7;

g is the acceleration of gravity;

ρс is the density of the oil and gas mixture in the measuring cylinder 7, calculated by the formula (1).

In the microcontroller 3, the necessary value of the level H _n * is pre-set and compared with the current values of the levels H ₁ , _{2 ... n of the} oil and water mixture calculated by the formula (2). When the values of the levels of H _n * and H _n are equal, at the command of the microcontroller 3, the electromagnetic valve 4 closes, which will stop the flow of oil and gas mixture into the measuring cylinder 7.

Due to the fact that the density of the oil and water mixture along the height of the measuring cylinder 7 is different, an error occurs when calculating the level by formula (2). To reduce the error in calculating the level of H _n oil and gas mixture, it is necessary that the density of the oil and water mixture along the height of the measuring cylinder 7 is the same.

To equalize the density of the oil and water mixture along the height of the measuring cylinder 7, the pump 14 is turned on by the command of the microcontroller 3, which pumps the oil and gas and water mixture along line 19 from the upper part of the measuring cylinder 7 to the lower part. As a result of this, the oil-gas mixture is mixed in the measuring cylinder 7.

Mixing accelerates the process of exit of bubble gas from the oil and gas mixture, and after its release in the measuring cylinder 7 remains oil-water liquid.

After mixing (the mixing time is set in the microcontroller 3), by the command of the microcontroller 3, the pump 14 is stopped and the oil-water liquid is checked for density uniformity along the height of the measuring cylinder 7.

To do this, measured values of the sensors pressure drops 11 and 20, and if the value of the differential pressure are then calculated liquid density ρ _Well, if - no, the mixing process needs to continue on, until the value of the sensor pressure drops 11 and 20 are equal. The density of the oil-water homogeneous liquid ρ _{W is} calculated by the formula (3):

$$\rho {}_{\mathrm{well}}=\frac{d\rho {}_{2\mathrm{well}}}{g\cdot H{}_{2\mathrm{well}}},$$

Where:

ρ _W - the density of the oil-water homogeneous liquid in the measuring cylinder 7;

dρ _2zh - pressure drop of the sensor 11 of the level of H ₂ liquid in the measuring cylinder 7;

g is the acceleration of gravity;

H ₂ - liquid level in the measuring cylinder 7.

After calculating the density of the oil-water homogeneous liquid ρ _{W, the} microcontroller 3 calculates the updated liquid level H _nzh by the formula (4):

$$H_{n\mathrm{well}}=\frac{d\rho {}_{n\mathrm{well}}}{g\cdot \rho {}_{\mathrm{well}}},$$

Where:

N _nzh - level of oil-water homogeneous liquid in the measuring cylinder 7;

dρ _nж - pressure drop of the level 9 sensor Н _nж in the measuring cylinder 7;

g is the acceleration of gravity;

ρ _W - the density of the oil-water homogeneous liquid in the measuring cylinder 7, calculated by the formula (3).

After calculating the adjusted level at the command of the microcontroller, the chemical dosing device 13 is turned on and a dose of the chemical is supplied to the measuring cylinder 7 through the pipe 21.

To reduce the time of separation of the oil-water liquid into oil and water, it must be mixed. For this, at the command of the microcontroller 3, the pump 14 is turned on, and the oil-water liquid is mixed (the mixing time is set in the microcontroller 3).

The further presence of the mixed oil-water liquid with a chemical in the measuring cylinder 7 will lead to the separation of the liquid into oil and water. This separation will occur gradually, water will accumulate at the bottom of the measuring cylinder 7, and oil - on top of the water.

Substitution of the oil-water liquid with water will lead to an increase in the pressure drop of the sensor 11, and the replacement of the oil-water liquid with oil will lead to a gradual drop in the pressure drop of the sensor 20, and when the liquid separation ends, the pressure drop of the sensors 11, 20 will end.

The microcontroller 3 calculates the end of the rise and fall of the differential pressure sensors 11, 20, calculates and stores in memory the density of water under operating conditions ρ _in when the temperature T1 of the sensor 25 and gauge pressure P1 of the sensor 15.

The density of water under operating conditions is calculated by the formula (5):

$$\rho {}_{\mathrm{at}}=\frac{\mathrm{<figure-callout\; id="2"\; label="d\; \rho "\; filenames="00000016.png"\; state="\{\{state\}\}">d\; </figure-callout>}{\rho }_{}{}_{2\mathrm{at}}}{g\cdot \mathrm{<figure-callout\; id="2"\; label="H"\; filenames="00000016.png"\; state="\{\{state\}\}">H</figure-callout>}{}_{2\mathrm{at}}},$$

Where:

ρ _in - the density of water under operating conditions in the measuring cylinder 7;

dρ _2c - differential pressure of the differential sensor 11 level H _2B in the measuring cylinder 7;

g is the acceleration of gravity;

H _2B is the water level in the measuring cylinder 7. After calculating the density of water, the microcontroller 3 calculates and stores the density of oil under operating conditions according to the formula (6):

$$\rho {}_n=\frac{d\rho {}_{2n}}{g\cdot H{}_{2n}},$$

where: ρ _n - oil density under operating conditions in the measuring cylinder 7;

dρ _3n - differential pressure of the differential sensor 20 level N _3n in the measuring cylinder 7;

g is the acceleration of gravity;

H _3n - oil level in the measuring cylinder 7.

After calculating the density of oil and water under operating conditions, at the command of the microcontroller 3, the solenoid valve 10 opens, and the contents of the measuring cylinder 7 through the solenoid valve 10, the throttle 16 through the outlet line 17 through the pipe 18 enters the pipeline, which is connected to the controller of the measuring unit.

The throttle 16 is used to manually set the speed of the emptying the contents of the measuring cylinder 7. The level of homogeneous oil-water liquid calculated by the formula (4) will decrease, and the water level N _c will also decrease. The microcontroller 3 will constantly calculate the density of the level of H ₂ according to the formula (7):

$$\rho =\frac{d\rho {}_2}{g\cdot \mathrm{<figure-callout\; id="2"\; label="H"\; filenames="00000016.png"\; state="\{\{state\}\}">H</figure-callout>}{}_2}.$$

In the memory of the microcontroller there are already oil density values ρ _n under operating conditions calculated by the formula (6). This density value ρ _{n is} compared with the current density values calculated by the formula (7). When these densities are equal, the microcontroller 3 will close the solenoid valve 10, and oil will remain in the measuring cylinder 7 under operating conditions.

The microcontroller 3 calculates the oil level in the measuring cylinder 7 according to the formula: (8)

$$H_n=\frac{d\rho {}_n}{g\cdot {\rho }_n},$$

Where:

N _n - the oil level in the measuring cylinder 7 after draining the water;

ρ _n - oil density under operating conditions in the measuring cylinder 7 after draining the water;

dρ _n - differential pressure of the differential sensor 11 level H ₂ in the measuring cylinder 7 after draining the water;

g - gravitational acceleration.

The water level in the measuring cylinder 7 is calculated by the formula (9):

N _in = N _W - N _n ,

Where:

N _in - the water level in the measuring cylinder 7;

N _W - liquid level calculated by the formula (4);

N _n - oil level calculated by the formula (8).

The volumetric water content is calculated by the formula (10):

$$W_o=\frac{N_{\mathrm{at}}}{N{}_{\mathrm{well}}}\times \mathrm{one\; hundred}\%,$$

Where:

W _o - volumetric water content of the liquid in the measuring cylinder 7;

N _in - the water level in the measuring cylinder 7, calculated by the formula (9);

N _W - liquid level in the measuring cylinder 7, calculated by the formula (4).

The value of the differential pressure of water in the measuring cylinder 7 is calculated by the formula (11):

$$d\rho {}_{\mathrm{at}}=d\rho {}_{\mathrm{well}}-d\rho {}_n,$$

Where:

dρ _in - the value of the differential pressure of water in the measuring cylinder 7;

dρ _W - the value of the differential pressure of the liquid of the sensor 9 level N _W in the measuring cylinder 7 (from formula (4));

dρ _n - the pressure drop of the sensor level 11 H ₂ in the measuring cylinder 7 after draining the water (from formula (8)).

The mass content of water is calculated by the formula (12):

$$W=\frac{d\rho {}_{\mathrm{at}}}{d\rho {}_{\mathrm{well}}}.$$

Thus, the proposed utility model allows determining the parameters of the oil and gas and water flow.

Claims (1)

A method for determining the parameters of an oil and water stream, including separating the oil and gas liquid contained in the measuring cylinder using chemicals for oil and water with a gas outlet, measuring the height of the liquid column, hydrostatic pressure, emptying the measuring cylinder, measuring the current values of the pressure drops and levels of the oil and gas liquid, oil-liquid liquid , oil, calculating the density of oil, water and determining the volumetric water content, while the volumetric water content according to the formula:
$${\text{W}}_{\text{about}}=\frac{{\text{H}}_{\text{AT}}}{\text{H}{}_{\text{well}}}\times \text{one hundred\%}\text{,}$$

where: Н _в - water level in the measuring cylinder, Н _ж - water-oil liquid level in the measuring cylinder, and the mass content of water is calculated by the formula:
$$\text{W}=\frac{\text{dρ}{}_{\text{AT}}}{\text{dρ}{}_{\text{well}}},$$

where: dρ _in - the value of the differential pressure of water in the measuring cylinder, dρ _w - the value of the differential pressure of the oil-water liquid in the measuring cylinder.

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