RU2658699C1 - Method of measuring the production of the oil well - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention relates to the oil industry and can be used in order to determine the gas factor of oil, as well as oil and water flow rates of oil wells. Method for measuring production of the oil well includes the entry of oil well products into a separator with a calibrated portion, its separation into the gas and liquid phases, sequential selection of gas and liquid respectively from the upper and lower points of the separator, measuring the flow rate of the fluid according to the filling rate of the calibrated part of the separator, and the gas flow rate – according to the rate of its emptying, as well as measuring the product density in the calibrated part of the separator by means of hydrostatic pressure difference sensors, which are installed at different levels of the calibrated part of the separator. Under the conditions of deficiency of the free gas phase in the well production, cyclical emptying of the separator from the liquid after its filling is performed using the siphon tube, the ascending line of which is connected to the lower point of the calibrated part of the separator, and the descending line of which is connected to the pressure line of the well, which is charged when the liquid level in the separation tank reaches the uppermost point of the siphon tube, and which breaks when the liquid level in the separator reaches the point of its collection by a siphon. Point of liquid removal from the container by the siphon is located directly below the lower sensor, and the upper point of the siphon tube – directly above the upper hydrostatic pressure sensor. Volumetric flow rate of the liquid, which is discharged through the siphon, is maintained above the volumetric flow rate of the incoming liquid to the separator by means of adjusting the throttle on the siphon's descending line.

EFFECT: technical result consists in providing the possibility of measuring the flow rate of the fluid in case of a small content of free oil gas or in case of its absence in the measured product.

1 cl, 1 dwg

Description

The present invention relates to the oil industry and can be used to determine the gas factor of oil, as well as oil and water production rates of oil wells.

Measurement of oil well production in most cases is carried out by automated group metering units of a stationary or mobile type. Known installation for measuring oil, gas and water in the production of oil wells / patent RU No. 168317 U1. Installation for measuring oil well production. Claim 07/21/2016. Publ. 01/30/2017 /. The installation includes a measuring tank with a calibrated part, upper and lower liquid level position sensors, lines for supplying well products to the separator, gas and liquid discharge from it, and a three-way valve for switching the liquid drain to gas extraction and vice versa. When the liquid level in the measuring tank reaches the upper sensors, the control unit sends a signal to the three-way valve actuator to drain the liquid, and when the lower sensor is reached, to the gas outlet from the upper part of the measuring tank.

Also known is a device for determining the production rate of a well / RF Patent No. 2133826. Installation for determining the production rate of wells. Claim January 5, 1998 Publ. July 27, 1999 /. The water flow 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.

However, the above analogues have a significant drawback, which consists in the difficulty of taking measurements with a low content of free gas in the well production entering the measuring tank. In the complete absence of free gas in the production, the measurement of flow rates becomes impossible.

A known method for determining the flow rates of oil, associated gas and water / Patent RU No. 2504653 C1. A method for determining the flow rates of oil, associated gas and water. Claim 07/30/2012 Publ. January 20, 2014 /. To measure the flow rate of the liquid, the measuring tank is filled with well products, and after reaching the maximum level of the oil-water mixture, the inlet tap of the measuring tank is closed and the time is taken to separate free gas from the liquid. After determining the flow rate of the oil-water mixture by the filling speed and the volume of the separated liquid, the gas phase is gradually taken from the upper part of the measuring container by the compressor through a reducer reducing to atmospheric pressure. In this case, the compressor pumps the sampled gas into the well reservoir. Gas is pumped out until the pressure in the measuring tank drops to atmospheric value. The gas factor is calculated by compressor performance and its operating time.

However, the use of a compressor is complicated due to a change in the pressure of gas injection into the reservoir, which varies over a wide range even within the same oil field.

A known method of measuring gas flow rate, based on the determination of the filling speed of two measuring tanks in turn and their subsequent emptying / RF Patent No. 2082107. The method of determining the amount of oil, gas and water in the production of wells. Claim May 18, 1995 Publ. June 20, 1997 /. The time of filling the tanks determines the flow rate of the oil-water mixture, and the flow rate of the tanks determines the flow rate of the free gas phase. The disadvantage of this device is 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.

The closest in technical essence to the proposed technical solution is a method of measuring the flow rate of oil and associated gas oil wells / patent RU No. 2439316 C2. Claim 04/05/2010. Publ. January 10, 2012 /, including the flow of extracted products from the tubing string into the separator and the separation of gas and oil in it. Next, sequential selection of oil and gas from the separator is carried out with the measurement of their quantity using a float and a three-way flow switch according to time, respectively, filling and emptying the measuring part of the separator. Oil and gas flows are switched by increasing the pressure on each side of the two-sided piston of the flow switch while float locking the oil and gas exits from the separator in the upper and lower ends of the vertical perforated pipe.

The disadvantage of this method is that when the pressure in the separator increases, the gas phase is compressed and the flow switch is delayed. This, in turn, leads to a significant error in measuring the time of loading and discharge of oil, as well as the reliability of the measurements.

However, the main disadvantage of this method is the impossibility of taking measurements with small amounts of associated petroleum gas or its absence in the liquid, for example, when measuring the production of highly watered wells. Small amounts of associated petroleum gas lead to a significant increase in the measurement period of its flow rate, measured for many hours, and in the complete absence of free gas in the liquid, to a loss in the operability of the installation and ensuring the measurement of the flow rate of the liquid due to the impossibility of emptying the measuring tank after filling it.

The technical task of the proposed method is to provide the ability to measure the flow rate of the liquid with a low content of free oil gas or its absence in the measured product.

The solution of the technical problem is achieved by the fact that in the known method for measuring the flow rates of oil, water and associated petroleum gas, which includes the flow of oil production into the separator with a calibrated part, its separation into gas and liquid phases, sequential selection of gas and liquid, respectively, from the upper and lower separator points, measuring fluid flow rate by the filling speed of the calibrated part of the separator, and gas flow rate - by the speed of its emptying, as well as the product density in the calibrated part of the separator ora using hydrostatic differential pressure sensors installed at different levels of the calibrated part of the separator, according to the invention, in conditions of deficiency of the free gas phase in the production of the well, for example, when it reaches high water cut, the cyclical emptying of the separator from the liquid after its filling is carried out using a siphon tube, the ascending line of which is connected with the lower point of the calibrated part of the separator, and the descending line with the pressure line of the well, and charged when the fluid reaches the level in the separation tank of the extreme upper point of the siphon tube, and disrupting its work when the liquid level in the separator reaches the point of its selection by a siphon, and the point of liquid withdrawal from the tank by a siphon is located directly below the lower sensor, and the upper point of the siphon tube is directly above the upper hydrostatic pressure sensor, and the volumetric flow rate of the liquid discharged through the siphon is maintained above the volumetric flow rate of the incoming liquid into the separator by adjusting the throttle on the downstream line of the siphon.

The drawing shows a schematic diagram of the implementation of the method.

A separator 4 is connected to the pressure collector 1 of the well through the inlet 2 and outlet 3 valves. An explosive valve 5. is placed on the collector 1. Inlet 6 and outlet 7 are connected to the separator 4. An ascending line 8 of the siphon tube is introduced at the lower point of the calibrated part of the separator 4, and its descending line 9 is connected through the throttle 10 to the outlet pipe 7. The gas pipe 11 connects the upper part of the separator 4 to the outlet pipe 7. At the upper and lower levels of the calibrated part of the separator 4, hydrostatic pressure sensors 12 and 13 connected to the control unit 14. The sensor 12 is installed below the upper point of the siphon, and the sensor 13, on the contrary, is higher than the entry point of the siphon tube 8. At the intersection of the drain line 15 of the separator with the gas pipe 11 there is a three-way valve 16 with an electric drive.

The method is as follows.

The oil well output coming through the inlet pipe 6 to the separator 4 is stratified into a liquid containing a certain volume of water and free associated gas released from the oil phase at a pressure in the reservoir 1. With a sufficient volume of free gas, i.e. in conditions of water cut to 75 ... 80%, the inductor 10 is completely blocked. When the liquid level in the separator 4 of the pressure sensor 12 reaches the control unit 14 sends a signal to the valve actuator 16 to switch it to drain the liquid from the separator 4. Prior to switching the valve 16, the accumulated gas phase is discharged from the separator 4 through the gas pipeline 11 through the valve 16 and pipeline 7 to the collector 1. After the tap 16 is switched to drain, the liquid level in the separator 4 will decrease, and when the sensor 13 is reached, the tap 16 will again switch to pouring liquid into the separator. Based on the speed of moving the liquid level from the sensor 13 to the sensor 12, the well’s flow rate is calculated, and by the rate of decrease in the liquid level from the sensor 12 to the sensor 13, the flow rate of free oil gas is calculated. The measured hydrostatic differential pressure of the liquid column between the sensors 12 and 13 when the calibrated part of the separator 4 is completely filled at known densities of oil and water allows us to calculate the water cut of the well production.

Upon reaching a water cut of 75 ... 80%, a deficiency of the free gas phase is formed and the duration of a decrease in the liquid level in separator 4 can be measured for many hours. The liquid will be a direct type emulsion (oil in water) with a water content of more than 75 ... 80%. A small amount of free gas released from oil at a pressure in the reservoir 1, does not allow measurements of products described above by the method of displacing the incoming liquid by accumulating gas from the separator 4.

Under these conditions, the three-way valve 16 is set to a constant position for gas discharge from the separator 4, and the throttle 11 is opened, i.e. measurements are made by including a siphon in the work.

The drawing shows the filling cycle of the separator 4 products, in which there is a rise in the liquid level. At the same time, in the ascending line 8 of the siphon tube, the liquid level also rises according to the law of communicating vessels. In addition, in the same period, a small amount of gas will flow through the gas line 11 and the outlet pipe 7 into the manifold 1.

Upon reaching the fluid level of the hydrostatic pressure sensor 12 by block 14, as in the previous case, the time of filling the liquid and the calibrated part of the separator 4 from the installation level of the sensor 13 to the installation level of the sensor 12 is recorded. The flow rate of the well is calculated by the liquid, and by the differential hydrostatic pressure between the sensors 12 and 13, as well as the well-known oil and water densities laid down by the program, the water cut of the well production is calculated.

A further rise in the liquid level in the separator and reaching the upper point of the siphon tube will lead to the overflow of liquid from the ascending line 8 to the descending 9. At the same time, the siphon is charged and through it the cycle of draining the liquid from the separator 4 to the collector 1 through the throttle 10 and pipe 7. Siphon the tube is selected so that the volumetric flow rate of the drained liquid from the separator 4 exceeds the volumetric flow rate of the liquid entering the separator 4 through the inlet pipe 6. Charging the siphon allows the liquid level in the separator 4 to be reduced I install the mark sensor 13 and further to the uplink siphon inlet 8 into the separator 4. Further, the gas line 8 enters the work and picks siphon. The liquid withdrawal from the separator 4 will immediately stop and the liquid level in it will already increase, i.e. the cycle of filling the separator 4 with liquid, etc. will begin.

The minimum pressure of the siphon N is determined by the distance from the entry point of the ascending line 8 into the separator 4 to the level of the outlet pipe 7. The maximum vacuum level h corresponds to the entire length of the ascending line 8 of the siphon tube. The choice of the corresponding lengths and diameters of lines 8 and 9, as well as the degree of overlap of the flow by the throttle 10, i.e. regulation of hydraulic resistance in the system allows for stable operation of the siphon and drain the required amount of liquid from the separator 4 per unit time.

Charging the siphon at the moment the liquid level reaches the upper point of the siphon, as well as the failure of its operation at the lower position of the liquid level due to the instability of the processes, require a short period of time. In this regard, the upper sensor 12 is located below the upper point of the siphon, and the lower sensor 13 is located above the point of fluid withdrawal from the separator 4. Thus, when determining the flow rate of a well by liquid, unstable periods of operation of the siphon are eliminated and measurements are made only by the time the liquid level moves from the sensor 13 to the sensor 12. Thus, the measurement of the flow rate of free gas due to its smallness with high water cut of the product is not performed.

The technical and economic advantage of the proposed method is the ability to measure the flow rate of oil and water wells with a low content of free gas in the produced product or its complete absence.

Claims (1)

A method of measuring oil well production, including the flow of oil well products into a separator with a calibrated part, its separation into gas and liquid phases, sequential sampling of gas and liquid from the upper and lower points of the separator, measuring fluid flow rate by the filling rate of the calibrated part of the separator, and flow rate gas - by the speed of its emptying, as well as the density of the products in the calibrated part of the separator using hydrostatic differential pressure sensors installed at different levels the calibrated part of the separator, according to the invention, in conditions of deficiency of the free gas phase in the production of the well, for example, when it reaches a high water cut, the cyclical emptying of the separator from the liquid after filling is performed using a siphon tube, the ascending line of which is connected to the lower point of the calibrated part of the separator, and descending - with the pressure line of the well, and charging when the liquid level in the separation tank reaches the extreme upper point of the siphon tube, and disrupts its work when the liquid level in the separator decreases the point of its selection by a siphon, and the point of liquid withdrawal from the tank by a siphon is located directly below the lower sensor, and the upper point of the siphon tube is directly above the upper hydrostatic pressure sensor, and the volumetric flow rate of the liquid drained through the siphon is maintained above the volumetric flow rate fluid into the separator by adjusting the throttle on the siphon downlink.

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