RU2558570C1 - Gas-liquid flow studying - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: method includes measurement of pressure, temperature, substance consumption in steady conditions of operation. Gas is injected into the plant loop until it reaches operating pressure, centrifugal gas blower is started up and by the required value of gas consumption is set by regulation of rotor rotation frequency. By means of liquid pump water is supplied to the tested string thus ensuring steady conditions in it due to monotonous growth of pressure losses until it is filled with gas-liquid flow and continuous level of pressure losses at the lower section. According to results of measurements in steady conditions volume of liquid V_l is defined in the studied gas-liquid flow as V_l=q_l·(t₂-t₁), where: t₁ is time for commencement of water inflow to the tested string; t₂ is time for beginning of steady conditions in the tested string; q_l is volumetric flow of liquid in operating conditions; and liquid speed rate reduced to cross-section of the string pipe:

where D is inner diameter of the tested vertical string; as well as volumetric water content φ in the studied gas-liquid flow. At that average actual speed of liquid w is defined on the fact that square area of liquid phase in the pipe cross-section is proportional to volumetric water content φ.

EFFECT: expanded functionality of the method that allows determining water content in the tested vertical string in real time.

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Description

The invention relates to techniques for investigating the movement of liquid flows and gas-liquid flows, for example, gas production processes in the oil and gas industry, associated with the study of the processes of gas-liquid flows in vertical pipelines and individual devices.

The prior art method for conducting gas-hydrodynamic studies of wells (see Yu.P. Korotaev, Selected Works, in three volumes, volume 1, edited by academician R.I. Vyakhirev, Moscow, Nedra, 1996, pp. 36-39, fig. 1). In the known method, studies are carried out on the effect of a liquid on resistance when gas moves through pipes. When conducting research, measurements of pressure and temperature are carried out at certain intervals until the readings become unchanged. The amount of water was measured in a volumetric way twice: before entering the mixer and after leaving the separator. Moreover, there was slightly more water at the inlet to the mixer than at the outlet. When determining the water flow rate, the average value was taken. The known method has a significant drawback, which consists in the complexity of research and the low accuracy of obtaining the result.

Closest to the proposed solution is a method of conducting gas-hydrodynamic studies (see RF patent No. 2515622 C2, E21B 47/00, 05/20/2014). The known method can be used to conduct gas-hydrodynamic studies of the movement of gas-liquid flows with the inclusion of mechanical impurities in vertical, inclined pipelines and individual devices. The known method provides the ability to observe quantitative changes and improve the quality of visualization of processes and gas-hydrodynamic experiments taking place in the volume and height of the pipe string. The radiation source in the known solution is installed with the possibility of lighting the tubing string, in which one section is made of a transparent material with divisions applied on this section. In the known method it is possible to carry out photo-recording and recording of panoramic images in the memory of the information processing unit, as well as to measure and photo-register the results of the experiment in synchronous mode. The known method allows you to identify and determine the size of gas-liquid and / or dry plugs, and / or the distances between them, and / or individual particles identified in the tubing string. However, using the known method it is not possible to determine the water content of the vertical columns in real time.

The problem solved by the invention is to develop a method for studying gas-liquid flow, which allows to study pipe multiphase hydrodynamics by measuring the liquid content in a vertical gas-liquid flow, using lift pipes with diameters from 73 to 168 mm at pressures up to 3.0 MPa and water-gas to study two-phase hydrodynamics a factor in the range of 10 ^-6 -10 ^-2 .

The technical result, which the invention is aimed at, is to expand the functionality of the proposed method, which makes it possible to determine the water content of a vertical column in real time.

The essence of the proposed method lies in the fact that the method of conducting studies of gas-liquid flow includes measuring pressure, temperature, flow rate of a substance in steady-state operating modes. Processing of the measurement results of the test is carried out on the installation containing the test column, designed to be filled with a working substance with a gas-liquid composition. Gas is pumped to the installation circuit to operating pressure, a centrifugal gas supercharger is started, and by adjusting the rotor speed of the supercharger using a frequency converter, the required gas flow rate is set. Using a liquid pump, water is supplied to the test column, providing a steady state in the column due to the monotonic increase in pressure loss over time until it is filled with a gas-liquid flow and a constant level of pressure loss in its lower section. According to the results of measurements at steady state, determine the volume of liquid V _W in the studied gas-liquid flow, as:

V _W = q _W · (t ₂ -t ₁ ),

Where:

t ₁ - the time of the beginning of receipt in the test column of water;

t ₂ - time of the beginning of the steady state in the test column;

q _W - volumetric flow rate under operating conditions;

and fluid velocity reduced to the cross section of the column pipe:

,

,

where D is the inner diameter of the vertical test column;

as well as the volumetric water content φ in the studied gas-liquid flow, as:

.

.

where V _Tr1 - the volume of the pipe section of the column, in which the process of movement of the gas-liquid flow.

In this case, the average true liquid velocity w is determined based on the fact that the area of the liquid phase occupied in the section of the column pipe is proportional to the volumetric water content φ:

.

.

The proposed method for conducting studies of gas-liquid flow is illustrated by drawings. In FIG. 1 shows a measuring circuit of a device for conducting studies of gas-liquid flow, explaining the proposed method. In FIG. 2 shows the results of measuring parameters, pressure loss ΔP, gas flow G through the column at operating pressure and liquid volume V _W in a real-time gas-liquid separator. In FIG. 3 shows the results of determining the time of filling the column with a gas-liquid mixture. In FIG. 4 shows an example of the density distribution of a gas-liquid mixture in a steady vertical gas-liquid flow.

A device for conducting studies of gas-liquid flow (Fig. 1) may contain:

- the test column (1) made of a transparent material and installed in a vertical position;

- at the base of the column is installed a gas and liquid mixer (2);

- the device has a gas inlet and outlet valve (3) connected by a pipeline to the gas outlet of the separator (4) on the one hand and to the inlet of the centrifugal gas supercharger (5) on the other;

- at the outlet of the separator liquid stream, a liquid pump (6) is installed, connected to a liquid flow meter (7);

- a centrifugal gas supercharger is connected through a gas flow meter (8) to a gas and liquid mixer;

- a block of differential pressure sensors (9) and a block of pressure and temperature sensors (10) can be installed on the test column;

- readings from the differential pressure sensor block (9) and the pressure and temperature sensor block (10), as well as from the gas flow meter, pass through the analog-to-digital conversion block (11) to the data processing and visualization unit of the observation results (12).

To implement the invention, standard equipment is used. Any liquid may be used to fill the column.

In the process of experimental research, the physical parameters of the process under study are monitored using digital information transmission channels, the processing of which is carried out in block 12.

For the implementation of the invention

- sensors with a current output of 4-20 mA can be used as differential pressure sensors and pressure and temperature sensors;

- the data processing and visualization block of the observation results can be implemented on the basis of a personal computer (PC) with the installed exchange driver, with the help of which they collect, display and store the obtained values of the technological parameters of the entire sensor system, for example, in a Microsoft Excel format file.

The signals from the pressure and temperature sensors are transmitted to an analog-to-digital converter, which is connected to a PC via RS-232 protocol.

During the experiment, gas is initially pumped into the loop circuit to the working pressure P. Then, at time t = 0 (Fig. 2, 3), the centrifugal gas supercharger (5) is turned on; by adjusting the rotor speed of the supercharger rotor by means of a frequency converter, the required gas flow rate G is established. After turning on the liquid pump (6) at time t ₁ (Fig. 3), water begins to flow into the test column (1), at the same time due to the appearance of a column of gas-liquid mixture begins to increase pressure losses ΔP in the test column, which are measured by sensors installed in its upper part, for example, at a height of 30 m. In the initial state, a certain amount of water V (in this experiment, this value is equal to 1.2 L).

The essential conditions for the behavior of a gas-liquid flow in experimental studies are (see Fig. 2):

1) pressure loss in the column up to its filling, which should monotonically increase in time, while ensuring a steady state;

2) the level of pressure loss in the lower section of the column after the column reaches the gas-liquid mixture level of 1.3 m should be maintained constant.

The fulfillment of these conditions indicates a uniform, almost piston-like, raising the column of the two-phase mixture and a constant value of local water content over almost the entire height of the column. The exception is a small upper section of the column, filled after time t> t ₂ (see Fig. 3), in which the local water content and local pressure loss are slightly less than over the entire remaining column height of the gas-liquid mixture in the tested column.

The implementation of the invention is confirmed by experiments. In FIG. 2 shows the measurement results obtained during the experiment on the monitor screen of the data processing unit and visualization of the observation results in on-line mode. The experiment in this Example was carried out on a vertical column of length L = 29,59 m with an inner diameter D = 100 mm at an operating pressure P = 1,04 MPa, a liquid flow rate q _g = 11.4 L / h, the gas flow rate G = 146 m ³ / hour. As components of a gas-liquid mixture, water and air were used. In FIG. 2 marked: ΔP (30 m) - the results of the measured pressure loss in the upper part of the column, (cm water column); curve C reflects the gas flow through the column at operating pressure, (m ³ / h); curve V reflects the volume of liquid in the separator, (l). At the same time, pressure losses were measured on the lower pipe section of the test column at a height of 1.3 m in order to determine the influence on the characteristics of the gas-liquid flow of the growing overlying column of the mixture. All the data obtained after analog-to-digital conversion in block 11 enters the data processing and visualization block of the observation results 12. Using block 12, the differential pressure sensors received from block 9 and from the pressure and temperature sensor block 10 are processed.

In FIG. 3, various phases of the experiment are marked. At the initial stage, after the gas flow rate was set at G = 146 m ³ / h, the friction pressure loss for single-phase gas over the entire column height (30 m) was 8.6 cm water. Art. At time t ₁ = 10.5 min, a liquid began to appear in the test column, which initiated the appearance and growth of a column of a gas-liquid mixture, accompanied by a monotonic increase in pressure loss.

At time t ₂ = 55 min, the column of the gas-liquid mixture (Fig. 4) reached the level of H ₁ , above which the density of the mixture somewhat decreases in the plot of H ₂ compared with the lower portion (Fig. 4). Neglecting this end effect under the conditions of the experiment, we determined the average velocity of the fluid in the pipe of the column, that is, the speed of filling the column with a gas-liquid mixture. The end of the period of filling the column ends at time t ₃ = 64 min (Fig. 3).

After filling the test column with a gas-liquid mixture to its upper part, the liquid from it is drained into the separator (4) (see curve V in Fig. 2). After some time, the mode is set in all areas of the device. In FIG. 4 shows the density distribution of a gas-liquid mixture in a steady vertical gas-liquid flow. During the time (t ₂ -t ₁ ) the column of gas-liquid mixture rises to a height of H ₁ , during the time (t ₃ -t ₂ ) the column rises along the upper section of the pipe of column II to the upper part of the pipe of the column of height L = H ₁ + H ₂ . After the regime is established, the density of the mixture in section I is almost constant (or varies very slightly), and in section II it decreases with height. Accepting Equality (1)

and, solving the equation, taking into account the given time parameters, we obtain H ₁ / L = 0.84.

The liquid volume V _W in the column in section I after filling it can be calculated based on the balance ratio (2):

where q _W is the volumetric flow rate of the liquid under operating conditions.

Given that the volume of the pipe section of the column is V _mp1 = 194 l, the volumetric water content φ in the investigated gas-liquid flow at steady state (section I of Fig. 4) is defined as:

The results of the experiments allow us to determine the average true velocity of the fluid flow w. Let v be the fluid velocity reduced to the cross section of the column pipe. In the experiment considered, it is equal to

Then, assuming that the area of the liquid phase occupied in the column section is proportional to the volumetric water content φ, we can determine the average true liquid velocity w

or w = 9 mm / sec. Thus, with an average liquid velocity in the column during the experiment under consideration, it is filled with a gas-liquid mixture, which is reflected by the slope α of the graph ΔP (30 m) in FIG. 3.

According to the described method, a series of experiments was conducted on columns whose pipe diameters were 62 and 100 mm. The aim of the research is to study the hydrodynamics of two-phase flows in relation to the operating conditions of Cenomanian wells at a late stage.

Comparison of the measured values of the volumetric water content in vertical columns with the calculated ones according to existing ratios showed that the proposed solution for determining the characteristics of ascending gas-liquid flows makes it possible to conduct practical studies of two-phase hydrodynamics in poorly studied ranges of physical parameters characteristic of the late stage of gas field development.

From the analysis of the experimental results, it follows that the local pressure loss, volumetric water content and the velocity of the liquid phase in the vertical gas-liquid flow are unambiguous functions of the column pipe diameter, liquid flow rate, gas flow rate and pressure. From the pressure measured at the wellhead, the gas flow rate and the water flow rate, one can determine the pressure and volumetric water content at any point of the working well from the bottom to the wellhead. In addition, it opens the possibility of developing new mathematical models for determining both stationary and non-stationary modes of operation of waterlogged gas wells (including, for example, crushing and blowing).

Claims (1)

A method of conducting gas-liquid flow studies, including measuring pressure, temperature, flow rate of a substance under steady-state operating conditions, while processing the test measurement results is carried out on a setup containing a test column mounted vertically and designed to be filled with a working substance with a gas-liquid composition, characterized in that the installation circuit pumps gas to operating pressure, starts the centrifugal gas supercharger and, by adjusting the rotor speed, sets the required gas flow rate is poured, water is supplied to the test column using a liquid pump, providing a steady state due to the monotonic increase in pressure loss in time until it is filled with a gas-liquid flow and a constant level of pressure loss in its lower section, according to the results of measurements at a steady state mode determine the volume of liquid V _W in the studied gas-liquid flow, as:
V _W = q _W · (t ₂ -t ₁ ),
Where:
t ₁ - the time of the beginning of receipt in the test column of water;
t ₂ - time of the beginning of the steady state in the test column;
q _W - volumetric flow rate under operating conditions;
and fluid velocity reduced to the cross section of the column pipe:

,
where D is the inner diameter of the vertical test column;
as well as the volumetric water content φ in the studied gas-liquid flow, as:

.
where V _Tr1 - the volume of the pipe section of the column, in which the process of movement of the gas-liquid stream
in this case, the average true liquid velocity w is determined on the basis that the area of the liquid phase occupied in the section of the column pipe is proportional to the volumetric water content φ:

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