RU2504653C1 - Method of defining oil associated gas and water discharge - Google Patents

Abstract

FIELD: oil-and-gas industry.

SUBSTANCE: proposed method comprises filling measuring tank with well product via inlet valve to maximum level With water-oil mix reaching maximum level, tank inlet valve is closed to let free gas to escape from fluid. Water-oil mix discharge is defined by the rate of tank filling the volume of separated fluid. Inlet valve is opened to displace the product from tank into manifold for time interval equal to previous period of tank filling with well product. Gas is gradually derived and forced into manifold by compressor. Gas bleeding is performed via pressure control valve at compressor inlet to atmospheric magnitude. Associated gas discharge is defined by compressor output, time of pressure decrease in calibrated vessel to atmospheric values and volume of vessel filled at the time with gas phase.

EFFECT: higher accuracy of measurement and definition of oil gas factor with allowance for dissociated gas.

2 dwg

Description

The present invention relates to the field of oil production and can be used to determine the flow rates of oil, water and associated petroleum gas (or gas factor) by both mobile and stationary metering units.

It is known that for monitoring the development of oil fields, automated group stationary metering units or mobile metering units are used. To measure the flow rates of oil, gas and water, a method is known based on determining the filling speed of two measuring tanks in turn and their subsequent emptying [1]. According to the time of filling the tanks, the flow rate of the oil-water mixture is determined, and the gas phase flow rate is determined by the rate of emptying of the tanks. Oil flooding or water flow rate is determined by the difference in the reflection coefficient of electromagnetic waves by the height of the liquid column in the cylinder at the time of filling.

The method has the disadvantage that, when measuring in a liquid filling a cylindrical container, dispersed water and gas phases are present in the form of droplets and bubbles, which leads to a significant measurement error. In addition, a sufficient amount of dissolved associated gas remains in the oil phase, which does not exit the oil at the operating pressure (usually pressure of the pressure head manifold) and therefore cannot be taken into account in calculating the gas factor of oil or gas production.

In a known installation for determining the production rate of a well [2], the water production rate is determined by the known densities of oil and water and the hydrostatic pressure of the liquid column in the measuring cylinder. At the time of reaching the upper level in the measuring tank, the sensors give a signal to switch the flow to another tank and measure the hydrostatic pressure, which determines the average density of the liquid. Using previously known oil and water densities, the water content in the liquid volume is calculated.

The measurement method by which the unit operates has a significant error due to the presence in the oil volume of a part of both free dispersed and dissolved gas.

Closest to the technical nature of the claimed invention are a method and apparatus for measuring oil flow rate [3]. The method includes feeding a gas-water-oil mixture into a measuring tank, separating it into gas and a water-oil mixture (ANS), which is an emulsion, measuring the ANS flow rate by the rate of filling of the calibrated part of this tank and draining the ANS with a frequency determined by the intensity of the product supply to a particular well , the calculation of the proportion of water and the proportion of oil in the liquid phase of this product from the measured value of the ANS density and the known values of the density of produced water and degassed oil, and the subsequent calculation of the oil flow rate. In addition to the calibrated part of the measuring capacitance, with a given periodicity, the ANS is filled in the settling chamber, it is held in it for a certain amount of time, after which the density of the settled ANS is measured, followed by emptying of this chamber.

The method has the same disadvantages associated with the need to measure the density of the mixture to calculate the water content in the volume of the measured capacity. In addition, the method does not allow to determine the gas factor of oil.

The aim of the invention is to improve the accuracy of measurement and determination of the gas factor of oil, taking into account dissolved gas.

This goal is achieved by the fact that in the known method, which includes filling to a maximum level through an open inlet tap of a measuring tank with well products pretreated with a demulsifier, measuring the flow rate of oil-water mixture by filling speed of a calibrated tank from minimum to maximum levels, pumping the mixture to the collector with a pump from the bottom of the tank for subsequent measurements, after the level of the oil-water mixture reaches its maximum position, the input of the first valve of the tank and the shutter speed for separating free gas from the liquid, then the flow rate of the oil-water mixture is determined by the rate of filling the tank with products and the volume of the separated liquid, after which the inlet valve is opened and the products are displaced from the tank to the collector for a period equal to the time of the previous filling of the tank with products wells, and after this period synchronously block the inlet and outlet cranes of the tank, open an additional drain line in the upper part of the tank and through it produce gradual sampling of the gaseous medium and pumping it into the manifold by the compressor, while the gas phase is taken through a pressure reducer that reduces the pressure at the compressor inlet to atmospheric value, and the associated gas flow rate is determined by the compressor supply, the time the gas pressure in the calibrated tank drops to atmospheric value and the volume of the tank occupied by this moment in the gas phase, and the water flow rate is determined by the time of filling and the levels of the section “ha s-oil ”and“ oil-water ”, after which the pump pumps liquids from the bottom of the tank into the collector with the inlet valve closed for subsequent measurement.

Figure 1 presents a diagram of the implementation of the method. In the collector 1, through which the production of the well is pumped out, a discontinuous valve 2 is installed. Before the valve 2, a receiving line 3 of the metering unit with an inlet valve 4 is connected to the collector 4. Line 3 connects the collector to a calibrated measuring capacitance 5, in which the sensors 6 and 7 are interphase levels of gas-oil and oil-water. The upper part of the tank through line 8, the outlet valve 9 and the check valve 10 is connected to the collector 1 after the valve 2. The lower part of the tank 5 is also connected to the collector through the valve 11, pump 12 and the check valve 10. In parallel with line 8 to the upper part of the tank 5 an additional line 13 with a valve 14, pressure gauges 15, 16, a reduction gear 17, a reciprocating compressor 18 and a non-return valve 19 is connected. The valves 4, 9, 11 and 14 are controlled by the controller 20 according to the signals supplied by the sensors 6 and 7. In the receiving 3 of the dispenser 21 demulsifier is dosed. Level 6 and 7 sensors are made of materials that allow them to be located on the interface. The material of the sensor 7 is selected intermediate between oil and water density.

Figure 2 presents the operating characteristic of the reciprocating compressor, showing the linear nature and constancy of gas flow at a given pressure drop at the inlet and outlet.

The method is as follows.

After the previous measurement and pumping of the liquid by the pump 12 from the tank 5 to the collector 1, the pressure in the tank 5 will correspond to the atmospheric value.

For new measurements, the cranes 4 and 9 are simultaneously opened, as well as the valve 11. The pressure of the downhole pump (not shown in Fig. 1) will begin to flow into the vessel 5 through the valve 4. Due to the pressure in the manifold, the gas in the vessel 5 will gradually compress, increasing the pressure in the container itself. Simultaneously with the flow of liquid into the tank 5, the separation of the free gas phase and partial release of dissolved gas from the incoming oil will begin. When the pressure in the pressure vessel 5 in the reservoir 1 is reached, part of the gas from the upper part of the vessel will be displaced by the liquid into the reservoir.

After the level of the oil-water mixture in the tank 5 reaches the maximum value, the sensor 6 sends a signal to the controller 20 to close the valve 4. After that, the separation of free gas and liquid will continue and the level of the gas-oil section will partially decrease. After this level is stabilized and will not change over time, the position of the sensor 6 is recorded for the subsequent calculation of the flow rate of the oil-water mixture by the time of filling the tank and the final level of the gas-oil section.

Next, the controller gives the command to open the tap 4. A new portion of the well’s production will begin to flow into the reservoir 5 under the pressure of the collector and displace previously arrived products into the collector through the tap 9 and the check valve 10.

The displacement of a new portion of products from the tank 5 is carried out for a period equal to the time of the previous filling of the tank with products. After this period, the valves 4 and 9 are closed and the valve 14 of the additional line 13 is opened. At the same time, the compressor 18 is turned on and gas will gradually be pumped from the top of the vessel 5 to the collector through the non-return valve 19. The pressure regulator 17 is adjusted so that the pressure after it it remains strictly atmospheric, which is controlled by pressure gauges 15 and 16. In this case, on the one hand, the compressor performs the function of an organ forcing gas from the tank to the collector 1. On the other hand, the compressor simultaneously performs the functions iju gas flow, meaning its strict operating characteristic (Figure 2).

Pumping of gas by the compressor continues until the pressure in the vessel 5 reaches atmospheric value, at which all the dissolved gas will come out of the oil.

Upon reaching atmospheric pressure in the tank, the valve 14 is closed, the compressor 18 is stopped and the position of the interfacial levels is monitored by sensors 6 and 7. After their stabilization, their position is recorded, the valve 11 is opened and the tank 5 is emptied by pump 12 into the collector 1.

After emptying, the valve 11 closes, and the valves 4 and 9 open for the following measurements.

Registration of the established positions of the interfacial levels with sensors 6 and 7 allows you to determine the flow rate of water by the volume occupied by it and the time of filling the tank.

The gas flow rate is determined by the product of the compressor supply at the time of gas evacuation until the pressure in the tank reaches atmospheric value. To this amount is added the volume of gas filling the upper part of the vessel 5 at the time the pressure reaches atmospheric value.

The gas factor of oil is calculated as the ratio of gas production (at atmospheric pressure) to oil production.

The technical and economic advantage of the claimed method is the high accuracy of the measured values and the ability to determine the gas factor taking into account dissolved gas.

Literature

1. Patent of the Russian Federation No. 2082107. The method of determining the amount of oil, gas and water in the production of wells. Claim 05/18/95, Publ. 06/20/97

2. RF patent No. 2133826. Installation for determining the production rate of a well. Claim 01/05/98, publ. 07.27.99 g.

3. RF patent No. 2236584. Method and device for measuring oil flow rate. Claim December 17, 2002, Publ. September 20, 2004

Claims (1)

A method for determining the flow rates of oil, associated gas and water from oil wells, which includes filling the measuring capacity to the maximum level through an open inlet valve with well products pre-treated with a demulsifier, measuring the flow rate of the oil-water mixture by filling speed of the calibrated tank from minimum to maximum levels, pumping the mixture out with a pump into the collector from the bottom of the tank for subsequent measurements, characterized in that after the level of the oil-water mixture reaches the maximum floor After closing the inlet valve of the tank and holding to separate the free gas from the liquid, then the flow rate of the oil-water mixture is determined by the rate of filling the tank with the product and the volume of the separated liquid, after which the inlet valve is opened and the product is displaced from the tank to the collector for a period equal to the previous time filling the tank with well products, and after this period synchronously shut off the input and output cranes of the tank, open an additional drain line in the upper part of the container and through it, the gas medium is gradually taken and pumped into the collector by the compressor, while the gas phase is taken through a pressure reducer that reduces the pressure at the compressor intake to atmospheric values, and the associated gas flow rate is determined by the compressor supply, the time of gas pressure decrease in calibrated capacity to the atmospheric value and the volume of the capacity occupied by the gas phase at this point, and the water flow rate is determined by the time of filling and established after degassing of oil and water separation of an oil-oil mixture to the levels of the “gas-oil” and “oil-water” sections, after which liquids are pumped from the lower part of the tank to the collector with the pump inlet closed for subsequent measurement.

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