RU2220282C1 - Process measuring production rate of oil wells in systems of sealed gathering and gear for its implementation - Google Patents

Abstract

FIELD: oil production, operative control over discharge of oil and gas condensate wells in systems of sealed gathering. SUBSTANCE: process includes filling of measuring vessel of calibrated volume of with well product while gas line is open to collector and fluid discharge line is closed, determination of hydrostatic pressure when height of fluid column, excessive pressure, temperature, rate of fluid driven by gas from vessel are known after shut-off of gas and opening of fluid discharge line to collector and estimation of productivity by fluid, oil, water and gas on basis of obtained data and known densities of oil and stratal water contained in well production. Time to fill measuring vessel with well product is specified beforehand with due account of maximal productivity of gear. On expiration of specified time supply of well product into measurement vessel is stopped, well product contained in measuring vessel is held till state of total absence of bubble gas and foam settling, then height of fluid column and hydrostatic pressure are measured and later supply of well product into measuring vessel is recommenced with simultaneous shut-off of gas line and opening of fluid discharge line to collector. Gear is equipped with volume gas separator, calibrated measuring vessel strapped by pipe-line fittings, the latter being fitted with gauges of its filling, hydrostatic and excessive pressures, thermometer and timer and flow switch connecting gas lines of separator and measuring vessel, collector and fluid discharge line of measuring vessel. Pipe-line fittings display capability to switch flow from inlet of well to collector and from well to separator with the help of flow switch and filling gauge of measuring vessel is analogous one ( radar or rheostat type, for instance ) and shows capability to check any level of fluid. EFFECT: raised measurement stability and accuracy. 2 cl, 1 dwg

Description

The invention relates to oil production and can be used for operational accounting of production rates of oil and gas condensate wells in pressurized gathering systems.

There is a method of accounting for oil well products, according to which a portion of accumulated products is maintained in the annulus of the well until it is stratified into components (gas, oil and water) under the influence of gravity, then these components are displaced from the annulus by the flow of well products through a flow transducer, recording time the passage of each component, while the components are identified, for example, by a density indicator (1).

The disadvantages of this method are the low accuracy due to the impossibility of a complete separation of the well products without heating and the introduction of chemicals, as well as the long duration of each measurement.

A device is known for implementing this method, comprising a packer, a flow converter, a processor module, a pressure sensor and a two-position valve-switch at the wellhead for communicating the annulus with the cavity of the tubing (1).

However, when using the known device, the formation pressure extends to the casing, which leads to a violation of its tightness.

The closest technical solution is a hydrostatic method for measuring the flow rate of wells by liquid, oil, water and gas, including determining the time for filling the measuring tank with partially separated well products of a fixed volume with a gas line open and a closed drain line, determining the hydrostatic pressure at a known height of the liquid column , excess pressure, temperature, speed of displacement of the contents of the container after closing the gas line and opening the drain idkostnoy line to the collector and the calculation performance liquid oil, water and gas based on the received data and the known densities of the formation water and oil contained in the wells of products (2).

This principle is based on the work of automated metering systems containing a volumetric gas separator and calibrated measuring tank equipped with sensors for its filling, hydrostatic and overpressure, a thermometer and a timer, as well as a flow switch connecting the gas lines of the separator and the measuring tank, the collector and drain liquid line of the measuring tank (2).

The disadvantages of the known method and device are:

- low accuracy and instability of measurements with increased foaming and high flow rates of wells;

- very stringent requirements for the quality of separation;

- high material consumption of the device, due to the need to have a very powerful separator.

The objective of the proposed technical solution is to increase the accuracy and stability of measurements by ensuring insensitivity to foaming, as well as to reduce material consumption by reducing the requirements for the quality of separation, and therefore, reducing the size of the separating elements, up to and including their exclusion from the device.

A method is proposed for measuring the production rate of oil wells in pressurized collection systems, including filling the measuring capacity of the calibrated volume with the production of the well with a gas line open and a closed drain liquid line, determining the hydrostatic pressure at a known height of the liquid column, gauge pressure, temperature, rate of liquid displacement by gas from tanks after closing the gas and opening the liquid lines to the collector and calculating the performance of liquid, oil, water and ha based on the obtained data and the known densities of oil and produced water contained in the well production, characterized in that the time for filling the measuring tank with the well products is set in advance taking into account the maximum productivity of the device, after a predetermined time the flow of the well products into the measuring tank is stopped, the well production contained in the measuring vessel is kept to a state of complete absence of bubble gas and foam settling, then the height of the liquid column is measured and hydrostatic pressure, and then simultaneously with the closure of the gas line and the opening of the liquid line to the collector, the flow of well production into the measuring tank is resumed.

A device for implementing this method is proposed, comprising a volumetric gas separator tied with pipe fittings and a calibrated measuring tank equipped with sensors for filling it, hydrostatic and overpressure, a thermometer and a timer, as well as a flow switch connecting the gas lines of the separator and the measuring tank, a collector and a liquid drain a line of measuring capacity, characterized in that the pipe fittings are configured to switch the flow from the entrance from the well for example, using the flow switch, and the sensor for filling the measuring capacitance is made analog with the ability to monitor any liquid level, for example, radar or rheostat type.

The implementation of pipe fittings with the ability to switch the flow from the inlet from the well to the reservoir and from the well to the separator, as well as the implementation of the sensor of the measuring capacitance analog with the ability to track any level of liquid provide, according to the method, filling the measuring capacitance for a predetermined time, keeping the well production the state of complete absence of bubble gas and foam sedimentation, followed by determination of the liquid volume and the remaining measurements.

The proposed method and device can improve the accuracy and stability of measurements, as well as create a compact device for measuring a wide range of flow rates of wells, including those where foamy oil and a high gas factor are present.

The drawing shows a device that implements the proposed method.

The device comprises a gas separator 1, a measuring tank 2, temperature sensors 3 and 4, an analog filling sensor 5 of the measuring tank 2, a differential pressure sensor (hydrostatic) 6, an overpressure sensor 7, flow switches 8 and 9, input from the well 10, exit to the collector 11, the inlet pipe 12 into the measuring tank 2; gas pipelines 13 and 14, respectively, from the separator 1 and from the measuring tank 2, a drain liquid line 15, outlets to the drain 16 and 17, a condensate sump 18, a check valve 19, samplers 20, valves 21, 22, 23, 24, 25 and 26, wedge gate valves 27, 28, 29 and 30, pressure gauges 31 and 32, safety valve 33.

The zero mark of the filling sensor 5 corresponds to a "zero" of the differential pressure sensor 6.

The method is implemented as follows.

The principle of operation of the device is based on the hydrostatic method of measuring mass, based on the dependence of the hydrostatic pressure P of a liquid column of height H on the density of the liquid ρ:

where q is the acceleration of gravity.

Before starting the work of the measuring device, the density values of oil and produced water determined by laboratory methods are entered into its control computer (not shown). The measuring capacitance 2 is calibrated by determining the dependence of the mass of liquid (water) in the range of the analog filling sensor 5 on the height of the tapping level determined by this sensor.

Assign a time τ of filling the measuring tank 2, during which the flow switch 9 connects the input from the well 10 to the separator 1. During this time, the highest production well, for which the measuring device is designed, should not overfill the calibrated volume of the measuring tank 2 with its liquid.

At the beginning of the measurement procedure, the flow switch 9 is placed in the “filling” position, the time for filling is started, and the production of the well from the inlet pipe 10 through the gas separator 1, in which the gas is preliminarily separated from the liquid, enters the measuring vessel 2 through the pipe 12. With this flow switch 8, the gas lines 13 and 14 are connected to the manifold 11, and the drain liquid line 15 is closed. At the end of the countdown time, the flow switch 9 is placed in the "drain to collector" position, the input from the well 10 is connected to the outlet to the collector 11, the filling is stopped, and the accumulated production of the well begins to settle in the measuring tank 2 to the state of complete absence of bubble gas and foam settling . The duration of sludge is determined empirically individually for each formation or well.

At the end of the sludge, the level H _i and the hydrostatic pressure of the liquid column ΔP are fixed (the value of the output current J _i of the differential pressure sensor 6).

Liquid production rate is determined by the following formula:

where K _p - the coefficient of proportionality, t / mA, determined during the calibration of the measuring installation. It takes into account all liquid poured over time τ, including the one below the “zero” of the analog filling sensor 5.

To determine the gas flow rate, the flow switches 8 and 9 are simultaneously placed in a position where the inlet from the well 10 is connected to the separator 1 and the drain fluid line 15 is connected to the manifold 11, while the gas pipelines 13 and 14 are closed. In this position, the liquid begins to be displaced from the measuring tank 2 by the gas coming from the well.

To measure the volumetric gas flow rate, the substitution method is used - the "PVT method" (pressure × volume × temperature).

The volumes of the measuring capacitance 2 V _i correspond to the values of the interval H ₀ -H ₁ and are determined during setup.

In the process of gas displacement of the liquid volume V _i , the displacement time τ _g and the average overpressure P and gas temperature t are fixed.

Gas production rate is determined by the following algorithm:

where V _i is the volume of the measuring capacitance 2 between the "zero" mark of the analog sensor 5 and the surface of the liquid detected by the analog filling sensor 5 after it has settled;

P is the average value of the excess gas pressure in the measuring tank 2, measured by the sensor 7;

t is the gas temperature ° C;

K _a is the compressibility factor.

Oil production rate

where ρ _in - the density of water in the production of the well (known value);

ρ _n - oil density in the production of the well (known value);

ρ _W - the density of the liquid in the production of the well (determined by the reading of the hydrostatic pressure sensor 6 in the interval of the analog filling sensor 5, for example, by the formula

where J _i is the hydrostatic pressure sensor reading corresponding to the liquid column Hi;

K _P2 - the proportionality coefficient of the interval of the analog filling sensor 5, t / mA;

V _i is the volume of the measuring capacitance 2 in the interval of the analog filling sensor 5 (corresponding to the liquid column H _i ).

Water flow rate

Using the proposed technical solution will make it possible to more widely apply the progressive hydrostatic method for measuring the production rate of oil wells, since the determination of the level of the measuring capacity (surface position of the separated liquid) does not depend on the quality of the preliminary separation and is not limited by the filling time. The absence of foam and residual gas in the measured liquid allows to obtain more correct measurement results.

Bibliographic data

1. A.S. No. 1437495, Е 21 В 47/10, 1988, bull. Number 42.

2. Certificate for utility model No. 22179, E 21 B 47/00, 2002, bull. No. 7 (prototype).

Claims (2)

1. A method of measuring the production rate of oil wells in pressurized collection systems, including filling the measuring capacity of the calibrated volume with the production of the well with a gas line open and a closed drain liquid line, determining the hydrostatic pressure at a known height of the liquid column, gauge pressure, temperature, rate of liquid displacement by gas from the tank after closing the gas and opening the drain liquid lines to the collector and calculating the performance of liquid, oil, water and ha based on the data obtained and the known densities of oil and produced water contained in the production of the well, characterized in that the time for filling the measuring capacity with the production of the well is set in advance taking into account the maximum productivity of the device, after a predetermined time the flow of the production of the well into the measuring capacity is stopped, the production of the well contained in the measuring vessel is kept to a state of complete absence of bubble gas and foam settling, then the height of the liquid column is measured and hydrostatic pressure, and then simultaneously with the closure of the gas and the opening of the drain liquid lines to the collector, the well production is returned to the measuring tank. 2. A device for measuring the production rate of oil wells in pressurized collection systems, containing a volumetric gas separator and calibrated measuring tank equipped with sensors for its filling, hydrostatic and overpressure, a thermometer and a timer, as well as a flow switch connecting the gas lines of the separator and measuring tank, manifold and drain liquid line of the measuring tank, characterized in that the pipe fittings are made with the possibility switching the flow from the inlet from the well to the collector and from the well to the separator, for example, using a flow switch, and the filling sensor of the measuring capacitance is made analog with the ability to monitor any fluid level, for example, radar or rheostat type.

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