RU2325520C2 - Method for determination of production rate of wells' production - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention is referred to the field of measuring of quantity of fluid and gas in a gas-liquid mixture. It can be used both in a petroleum industry and in those production fields where it is necessary to metre quantity of fluid and gas in a two phase flow. It provides increase of functionality of panel measuring devices operating on fields by attachment to it of functions of gas and fluid gain measuring for gas-oil ratio definition at minor alteration of means and measuring technology. Essence of invention: method includes hole hooking up on measurement, separation of a well production and fluid accumulation in a metering tank with fluid and gas diversion lines of fluid and gas, measuring of temperature, a fluid and gas production rate. According to the invention a hole is hooked up serially on panel measuring devices, and for definition of a production rate of fluid and a gas at the barred line of diversion the gas diversion line is bridged. The pressure is defined and time of gas diversion line capping is fixed. Fluid accumulation with a pressure boost in a metering tank is continued. Simultaneously or in any succession fluid and gas diversion lines is opened. The pressure is defined and time of opening of first by turns lines and a gas gain in a metering tank and a fluid gain in a metering tank during its work with both bridged fluid and gas diversion lines is defined.

EFFECT: increase of functionality of panel measuring devices at minor alteration of means and measuring technology.

3 cl, 1 dwg

Description

The invention relates to the field of measuring the amount of liquid and gas in a gas-liquid mixture. It can be used both in the oil industry and in those areas of production where it is necessary to measure the amount of liquid and gas in a two-phase flow.

Known methods for determining the flow rate of liquid and gas in the production of wells, in which a gas-liquid system is supplied to a tank for separation into a gas and liquid phase, while the flow rate of the liquid is measured by the weight of the separated liquid [1. SU 1680966, MKI ⁵ Е21В 47/10, 1991], or a flow meter [2. RU 2157888, MKI ⁷ Е21В 47/10, 2000] on the flow line, and the gas flow rate by the flow meter on the gas flow line [1], or by the difference in the flow meter on the gas-liquid line [2] at the inlet to the tank and the flow meter at the outlet of the separated oil .

The disadvantage of the methods is the difficulty of applying them to group metering devices.

Closest to the proposed is a method of measuring the production rate of oil wells [3. RU 2220282, MKI ⁷ Е21В 47/10, 2003], which includes the separation of well products and filling the measuring tank with liquid in an open gas and closed liquid lines. The method involves determining the hydrostatic pressure in the vessel at a known height of the liquid column, determining the overpressure, determining the temperature, setting the time for filling the vessel, holding the product to the complete absence of gas bubbles and foam settling, and measuring the height of the liquid column and hydrostatic pressure. Simultaneously with the closure of the gas and the opening of the liquid lines, the flow of products into the tank is resumed, the rate of liquid displacement by gas after the gas closure and the opening of the liquid line is determined, and the productivity of the liquid, oil, water and gas is calculated based on the data obtained and the known densities of oil and water contained in well production.

In the vast majority of Russian fields, the gas production rate and, accordingly, the gas factor of well production are not measured on group metering devices, since well production with different fluid rate, with different water cut and gas content is supplied to group metering devices. The disadvantage of the prototype is that the high sensitivity of gas and gas-liquid flow meters to the ratio of phases in the system and to the flow rate leads to a significant error in the measurement of the gas factor of well production.

The technical challenge facing the invention is to increase the functionality of the gas fields operating in the fields by adding to them the function of measuring the gas factor with a slight change in the technical means and measurement technology.

The problem is solved in that when determining the production rate of the wells, including connecting the well for metering, separating the production of the well and accumulating fluid in the measuring tank with liquid and gas extraction lines, measuring temperature, fluid flow rate and gas flow rate, additionally connect to the group measuring devices of the well alternately, and to determine the fluid flow rate and gas flow rate with a closed liquid exhaust line, the gas exhaust line is closed, the pressure is determined and the time it takes to close the line from ode of gas, continue to accumulate liquid with increasing pressure in the measuring tank, at the same time or in any sequence, open the drainage lines of liquid and gas, determine the pressure, record the opening time of the first line in turn and determine the increase in gas in the measuring tank, and determine the increase in liquid in the measuring tank during her work with both blocked liquid and gas drainage lines.

For foamy oil, the production flow into the tank before the opening of the first in turn liquid or gas removal line is stopped until the foam settles.

The overlap of the gas exhaust line may coincide with the connection of the well for measurement.

The invention is illustrated by the drawing, which shows a diagram of a device for measuring the gas factor of well production (the drawing schematically shows an automated group metering unit - AGZU).

The automated group metering unit includes a switch 1 for connecting wells in turn through line 2 to a measuring tank 3 combined with a separator, equipped with a pressure gauge 4. The tank 3 is equipped with a gas exhaust line 5 and a liquid discharge line 6. A drain valve 7 and a flow meter 8 are installed in the liquid discharge line 6, and a temperature sensor 9, a gas damper 10 and a gate valve 11 are installed in the gas outlet line 5. Lines 5 and 6 are connected through a valve 12 to the collecting manifold 13. In the tank 3 there is connected gas shutter 10 float 14. The installation has an automated control system 15, which provides the connection of wells for measurement, and pressure sensors, temperature, time and fluid flow to block 16 to calculate the flow rate.

The principle of operation of existing metering devices, including automated devices, is as follows.

The production of wells (gas-liquid system) entering the switch 1, along the supply line 2 is supplied to the measuring tank 3, which serves to separate the phases. When the valve 7 is closed, fluid accumulates in the lower part of the tank 3 at a linear pressure P ₁ , which is recorded by a pressure gauge 4. The gas released at pressure P ₁ through the gas exhaust line 6 through open valves 11 and 12 enters the collection manifold 13. During the production of the well together with the liquid level, a float 14 rises into the tank 3, which closes the gas shutter 10 at a certain liquid level. When the line 5 is closed, the pressure in the tank 3 rises to the value of Р ₂ and opens the drain valve 7. Discharged in di in the pressure range P ₁ -P _{2, the} liquid through the flow meter 8 enters the collection manifold 13. The liquid level in the tank 3 decreases, the shutter 10 opens the discharge of accumulated gas into the collection manifold 13. During the time of liquid displacement, the gas-liquid system continues to flow into the tank and the gas phase is removed . When the liquid level drops to the initial valve 7 closes and switch 1 connects the next well to the measuring system.

Automated control system (ACS) 15 provides timely connection of wells to the measuring device (measuring tank 3), and pressure sensors 4, temperature 9, time and flow meter 8 to the device 16 for calculating the flow rate.

It is easy to verify that the design of the gas supply unit provides both a measurement of fluid flow rate and gas flow rate.

We accept:

V ₀ is the volume of the memory, i.e. capacity 3 and gas line 5 to the valve 10;

V ₁ - the volume of the tank 3 occupied by the liquid when closing the valve 7 and connecting another well to the gas storage unit;

t ₁ - the time of accumulation of fluid in the separator before closing the shutter 10;

t ₂ - the time of accumulation of fluid in the separator until the opening of the drain valve 7;

P ₁ and P ₂ - pressure in the tank 3 when connecting the well and at the time of opening of the valve 7, respectively;

T is the temperature of the liquid;

t ₃ - the total time of measuring the flow rate of the well;

z is the coefficient of non-ideal gas;

Q is the volume of fluid passing through the flow meter 8 during the drain.

The volume of fluid Q ₁ received in the tank until the shutter 10 is closed is determined by the expression:

Accordingly, the volume of gas V _g1 at a pressure P ₁ is equal to:

The free volume V _g2 filled with gas at a pressure of P ₂ is determined by the expression:

The volume of gas under normal conditions will be:

Volume V _g2 is the gas that was in the tank at a pressure of P ₁ at the time of shutter 10 closure, and the gas released from the oil that entered the tank at a time t ₂ -t ₁ when the shutter was closed. The volume of gas V _g released from the oil entering the tank during t ₂ -t ₁ is determined by the expression:

Therefore, the gas factor of the production of the GJ well under the conditions of the GZU operation is determined by the expression:

With a known water cut k and residual gas content of oil ΔГ in gas-oil separation, the gas oil factor is:

Thus, the differences and advantages of the proposed method from analogues and prototype consist in the fact that the need for gas-liquid and gas flow meters is eliminated, and after measuring the operating time of the gas storage unit with a closed shutter, the gas factor is determined by the formula (7).

To increase the accuracy of measurements in high-yield wells with a high gas content, when the operating time of the GZU in the standard mode with the shutter closed can reach several seconds, which leads to an increase in the error in measuring the gas factor, by adjusting the float, the liquid level at which the shutter closes the gas line is reduced.

The increase in pressure begins before the gas line closes due to a decrease in the flow area, which leads to an error in the measurement of the gas factor. The magnitude of the error depends on the flow rate and gas content of the product, as well as on the set opening pressure of the drain valve. This drawback is eliminated by installing a valve in the gas line instead of the shutter 10. The valve closes when the set liquid level in the separator (measuring tank 3) is reached. Simultaneously with closing the valve, a report on the operating time of the gas supply unit with the valve closed is turned on. When pressure P _{2 is} reached, valves for venting liquid and gas open. The GZU operation time report is closed with the valve closed. The report of the time of change in the fluid flow rate continues until the drain valve 7 closes. On a low-flow fund of wells with a low gas content, the flow rate measurement should be started with valves 7 and 10 closed. Valve 7 opens when pressure P _{2 is} reached simultaneously with valve 10 on gas line 5 being opened.

A certain difficulty is the measurement of the gas factor and the debit of wells with foamy oils. The presence of foam leads to an underestimation of the flow rate and to an overestimation of the gas factor. To improve the reliability of the measurements, as in the prototype, it takes time to extinguish the foam, during which the gas-oil system should not enter the tank 3. This is achieved by the fact that when the pressure P ₂ in the tank 3 is reached with the valves 7 and 10 closed, the time report measuring the debit of liquid and gas, the control device 15 switches the switch 1 to the neutral position, in which all the wells work directly in the collection manifold, bypassing the measuring tank 3. After the set time for the foam settling time, the ACS provides The switch 1 connects the well to measure oil and gas flow rates.

Claims (3)

1. A method for determining the production rate of wells, including connecting the well for metering, separating the production of the well and accumulating fluid in the measuring vessel with liquid and gas discharge lines, measuring temperature, fluid flow rate and gas flow rate, characterized in that the wells are connected in series to metering devices , and to determine the liquid flow rate and gas flow rate with a closed liquid exhaust line, the gas exhaust line is closed, the pressure is determined and the time of overlapping the gas exhaust line is recorded, continue liquid pouring with increasing pressure in the measuring vessel, at the same time or in any sequence, open the liquid and gas removal lines, determine the pressure, record the opening time of the first line in turn and determine the gas growth in the measuring vessel and the liquid growth in the measuring vessel during its operation with both blocked lines of drainage of liquid and gas. 2. The method according to claim 1, characterized in that for foamy oil the production flow into the tank before the opening of the first in turn liquid or gas removal line is stopped until the foam is deposited. 3. The method according to claim 1 or 2, characterized in that the overlap of the gas exhaust line coincides with the connection of the well for measurement.