WO2022119479A1

WO2022119479A1 - Controlling the condensate/gas or gas/oil ratio of a multiphase fluid

Info

Publication number: WO2022119479A1
Application number: PCT/RU2021/050411
Authority: WO
Inventors: Марат Тохтарович НУХАЕВ; Константин Васильевич РЫМАРЕНКО; Сергей Вячеславович ГРИЩЕНКО; Александр Васильевич ЗАЙЦЕВ
Original assignee: Общество с ограниченной ответственностью "АРЛИН ИНЖИНИРИНГ"
Priority date: 2020-12-02
Filing date: 2021-12-02
Publication date: 2022-06-09

Abstract

Proposed are a device and method for controlling the gas/oil or condensate/gas ratio of a multiphase fluid in a producing well, comprising a wellhead pressure sensor, a wellhead temperature sensor, a downhole pressure sensor, a downhole temperature sensor at a given depth, and a flow analysis and control unit comprising a shutoff and control valve. Said valve keeps the level of the gas/oil ratio (or condensate/gas ratio) constant by comparing it with a predetermined level. The device can also be used for regulating the performance of a gas lift producing well by controlling the flow rate of lift gas.

Description

CONTROL OF GAS CONDENSATE AND GAS RATES OF A MULTI-PHASE FLUID

Description

Technical area

The invention relates to the field of oil and gas condensate production and to measuring equipment and can be used to measure the gas condensate factor in the production of gas condensate wells and the gas factor in oil and gas wells. The main purpose of the invention is the automatic control and regulation of production wells. Production wells include gas, gas condensate, oil and wells using gas lift technology.

Prior Art

When producing multiphase hydrocarbons from oil and gas and gas condensate wells, an important task is to maintain a constant level of the phase composition in the outlet pipe. The proportion of gas in gas condensate wells depends on the current pressure and temperature of the multiphase fluid and the presence of liquid droplets, since the production of such wells consists of light hydrocarbons that undergo a phase transition under well operating conditions. A change in the phase composition of the produced fluid can be caused by the opening or closing of downhole valves, the operation of downhole pumps, and downhole operations. A sharp change in the gas condensate factor in the flow rate creates the need for additional measures to prepare the fluid (for example, the use of separators) before it is fed into the main pipeline and makes it difficult to assess the commercial value of the produced gas-liquid mixture (fluid). GOR measurement in a multi-phase mixture can be carried out using multi-phase flow meters, for example, multi-phase flow meters of the Vx series (Schlumberger). However, these flowmeters are equipped with high activity gamma sources to measure the specific gravity of the three phases, which makes such devices expensive and require special permits to work with radioactive sources. When producing using gas lift, gas is pumped under constant pressure into the tubing (through special gas lift valves), which reduces the specific gravity of the gas-liquid column, and this intensifies the flow in the vertical direction (a kind of mechanical production). It is important for the operator to maintain a constant level of gas in the produced gas-liquid fluid. Patent RU2556293 discloses a device for measuring the gas condensate factor (GCF). The device uses phase separation and includes a measuring vessel with a valve, pressure and temperature sensors, a rotary gas flow meter, a hydrate formation inhibition unit, as well as control and supply fittings. At the same time, the gas flow measurement error is less than 5%, which meets industry standards. At the same time, such a device does not allow to quickly determine and regulate the gas condensate factor during production. A device for measuring the gas factor (void fraction) in a two-phase mixture using a Venturi tube is known - patent document CN108168612. The method is based on the statistical analysis of the differential pressure signal on the Venturi tube, while the fluctuation coefficient is determined from the extreme points of the symmetrical signal decomposition.

Brief summary of the invention

The claimed device allows online measurements of the gas factor, gas condensate factor of the gas-liquid mixture (GZhM) and maintain these factors at a constant level using a control valve. The device includes pressure and temperature sensors (in the well and at the wellhead), control unit to maintain a constant level of the gas factor.

Technical task

The claimed device offers control of the gas-lift production method by means of automatic control of the specific consumption of gas-lift gas.

The solution of the problem

In the practice of the oil and gas sector, the following criteria are used to describe the composition of a multiphase fluid (gas-liquid mixture): gas factor (gasfactor or GOR) - the number of m3 of produced gas under standard conditions per 1 m3 of extracted oil; gas condensate ratio (GCR) - relative flow rates (m3/m3) of gas under standard conditions and condensate in the produced fluid; the literature also uses the gas condensate ratio (CGR) criterion, which is simply the reciprocal of the gas condensate ratio; watercut (watercut) - the proportion of water in the liquid phase of the produced fluid. The device for control (i.e. measuring and maintaining a constant level of the gas factor or gas condensate factor) includes the main components, which are displayed in the general diagram in Fig. one.

The device is used in oil and gas and gas condensate wells. The well is equipped with a casing pipe 1, tubing 2 for the production of gaseous and liquid hydrocarbons (the direction of flow is shown by an arrow), which are separated by a packer 3. On the surface there is an outlet pipe 4 for supplying hydrocarbons to a hydrocarbon transportation and preparation station. The device includes pressure sensors 5 and temperature 6 at a known depth H, pressure sensors 7 and temperature 8 at the wellhead 9. The data from the sensors is processed in the flow analysis and control unit 10.

The lower pressure sensors 5 and temperature 6 can be lowered to a given depth H with the help of a geophysical cable or on a wire. Pressure sensors 5 and temperature 6 can be installed in a special mandrel (not shown) on the tubing. Data from sensors b and b are sent to the flow analysis and control unit 10 via cable or transmitted wirelessly.

In FIG. 2 shows a general diagram of the flow analysis and control unit 10: outlet pipe 4 for transporting hydrocarbons, a shut-off and control valve, and an actuator (electric drive) 12.

According to the pressure difference between pressure sensors 5 and 7, according to the known temperature from sensors 6 and 8, and with a known difference in depth between them H, the analysis and control unit 10 calculates the specific density of the fluid.

Data on the specific density of the fluid at the wellhead and data from pressure and temperature sensors are sufficient to calculate the GOR or gas condensate factor with a known water cut of the GLS.

In this case, the calculations of the necessary factors (gas or gas condensate factor) are carried out by the analysis and flow control unit 10, which has an appropriate processor for calculation. The processor performs data filtering (smoothing of the input data) and then performs calculations in accordance with the algorithm below.

List of variables and parameters in the formulas below: a _VG is the average gas volume fraction under operating conditions for the fluid between the high and low point; oc _VL - volume fraction of liquid under operating conditions; p _G is the average density of the gas under operating conditions; p _{G v} - gas density at the upper measuring point, known or calculated on the basis of the known equation of state (PVT-properties), pressure and temperature at the upper point; p _GD is the gas density at the lower measuring point, known or calculated from the known equation of state (PVT-properties), pressure and temperature at the lower point;

PG SC ~ gas density under standard conditions; p _L is the density of the liquid; p ₀ - oil density; p _w - water density; p _/tx ~ density of the gas-liquid mixture in the pipe;

K, - slippage, or the ratio of the liquid velocity to the gas velocity in a multiphase flow;

Wet - water cut (watercut);

CGR - condensate-gas ratio, in m ^{3 of} condensate per m ^{3 of} gas (under standard conditions);

GOR - GOR, in m ^{3 of} oil per m ^{3 of} gas (under standard conditions);

H - height difference of pressure sensors, m; g - free fall acceleration;

P _D - pressure at the lower measurement point, Pa;

P _and - pressure at the upper measurement point, Pa;

T _and - temperature at the upper measurement point, °C;

T _D - temperature at the lower measurement point, °C.

Algorithm for calculating CGR and GF (CGR and GOR).

One calculation algorithm is applied to determine the GOR and GOR.

1) Calculate the average density of the gas-liquid mixture:

2) Calculate the density of the liquid (this is a mixture of condensate + water or oil + water) = P _o ( -Wct) + Wct - p _p ^AND OR p _L = p _c (l - Wct) + Wct - p _w (2)

3) From the known pressure and temperature, calculate the gas density under the conditions of the lower (pressure sensor 5 and temperature 6) and upper measurement point (pressure sensor 7 and temperature 8) p _{G and} (P _and , T _and ) and p _GD (P _D , T _D )~ on the basis of known PP7 models or the equation of state of the gas, taking into account the solubility of the gas. Next, calculate the average gas density as the arithmetic mean between the gas density under the conditions of the lower and upper measurement points

down) / 2 (3)

4) Calculate the average volume fraction of gas a _VG , condensate a _vc or oil

avo = (1 _VG )(1 - Wet) or a _{l G} = (1 - d _{l G} )(1 - Wet) (5)

Estimate phase slip according to known models:

6) Calculate CGR and GF ratios (CGR and GOR)

The method allows to additionally calculate the water cut of the mixture from the same input data for pressure and temperature.

Algorithm for calculating water cut (Wet) at constant GOR or CGR (CGR or GOR)

The calculation process is iterative up to the required accuracy in terms of water content АУсй

1) Calculate the average density of the mixture:

~ P down - P up // \

P mix = - ( ⁹ ) gH

2) Knowing the pressures and temperatures, calculate the gas density under the conditions of the lower and upper measurement points p _G ^(/^, 1^) and p _GD (P _D , T _D ) , based on known IG models or the equation of gas state, with solubility. Calculate the average gas density as the arithmetic mean between the gas density under the conditions of the lower and upper measuring points

down) / 2 (10) 3) Calculate the following liquid density approximation (condensate+water or oil+water), where water cut Wet is taken from the value obtained at the previous iteration (presumably close value or zero in the first iteration):

PL = Po ¹ ~ ^Wct ) + ^Wct - P _w ^or (11)

4) Calculate the average volume fraction of gas d _{l G} , condensate a, - or oil

Evaluate phase slip:

Calculate water cut

7) Compare the obtained water cut Wet ¹ with that used in step (3}Wct : if the obtained difference does not meet the error requirements, return to step 3 (Otherwise, use Wet ¹ as the required water cut).

The operation of the device for controlling the GOR GOR (or gas condensate factor GKF) is illustrated in FIG. 3 and is carried out as follows:

The control process involves the automated execution of the algorithm described above, except for setting the control minimum and maximum values of GOR (GORMAX^GORMIN) or GCF (SH/7 .\uS67 d//\) with a known water cut ( _c t).

In one of the embodiments of the invention, the water cut of the mixture is known from other measurements (on offset wells) or using a water cut sensor on the pipe (sensor not shown).

In this case, the position of the shut-off and control valve changes step by step according to the principle of negative feedback according to the difference between the given CGR and the calculated CGR. In the case of an oil and gas well, the position of the shut-off of the control valve is changed step by step according to the principle of negative feedback for the difference between the given GOR and the calculated GOR.

The operation of the device shown in Fig. 1-2 includes the following steps:

1) Measurement of pressure Pu and temperature Ti at the wellhead or interrogation of pressure sensors 7 and temperature8.

2) Measurement of pressure and temperature Tr in the well at depth H or interrogation of pressure sensors 5 and temperature 6

3) Determination of the average density of the gas-liquid mixture according to formula (1).

4) Definition of GF or GKF according to formulas (2)-(8).

5) Comparison of the obtained GCF or GF with control (set) values. If the coefficients are in the required range of values, then you can return to point 1 after a specified time (polling time).

6) If the operation of the device is designed to control the GCF, and the calculated GCF is below the specified lower limit, then it is required to open the control valve to the specified step (mm).

7) If the calculated GCF is higher than the specified upper limit, then it is required to close the control valve by the specified step (mm).

8) If the operation of the device is designed to control the GOR, and the calculated GOR is below the specified lower limit, it is required to close the control valve by the specified step.

9) If the operation of the device is designed to control the GOR, and the calculated GOR is higher than the specified upper limit, it is required to open the control valve by the specified step.

10) If the valve has reached one of the limit positions, the device signals this to the operator, who can decide to stop the operation of the device.

11) After a specified time (related to the characteristic time of composition changes in the well), return to point 1 and continue monitoring.

The control of the gas lift method of production consists in the fact that the control unit calculates the gas factor (GOR) for a mixture of gas lift and produced gas as described above for oil and gas wells, but the control signal from the automation unit is also applied to the gas lift valve on the tubing (not shown for you just understanding drawings) or compressor control to reduce/increase gas-lift gas flow.

While the embodiments have been illustrated and described in detail in the drawings and description, they are to be considered illustrative and not restrictive.

Positive effects of the invention

The control of the gas factor or gas condensate factor is carried out automatically, without operator intervention, which creates significant advantages over known devices and methods.

Brief description of the drawings

Further, the invention is considered with reference to the attached drawings, which show: figure 1 shows a schematic diagram of the proposed device installed on a gas or gas condensate well. The arrow shows the direction of the produced fluid flow; in fig. 2 - schematic diagram of the control and management unit; in fig. 3 is a block diagram of the operation of the control unit for maintaining a constant level of GOR or GOR.

Industrial Applicability

During field tests for gas condensate wells, it was shown that the measurement error complies with the requirements of GOST R 8.615-2005 “Measuring the amount of oil and petroleum gas extracted from the bowels. General metrological and technical requirements”.

Claims

Formula

1. A device for monitoring the gas factor of a multiphase fluid in a production well, including pressure and temperature sensors at the wellhead, a pressure and temperature sensor at a given depth in the well, a block for analyzing and controlling the flow, including a shut-off control valve, characterized in that the shut-off the control valve maintains a constant GOR.

2. A device for monitoring the gas condensate factor of a multiphase fluid in a production well, including pressure and temperature sensors at the wellhead, pressure and temperature sensors at a given depth in the well, a block for analyzing and controlling the flow, including a shut-off and control valve, characterized in that the shut-off the control valve maintains a constant gas condensate factor.

3. A device for controlling the GOR of a multiphase fluid according to claim 1, characterized in that the shut-off and control valve operates on the principle of negative feedback.

4. A device for monitoring the GOR of a multiphase fluid according to claim 1, characterized in that the device is additionally equipped with a water content sensor.

5. A device for monitoring the GOR of a multiphase fluid according to claim 1, characterized in that the distance between the two pressure sensors allows you to determine the density of the multiphase fluid in the upper part of the well.

6. A method for controlling the gas factor of a multiphase fluid in a production well, including pressure and temperature sensors at the wellhead, downhole pressure and temperature sensors at a given depth, a flow analysis and control unit, including a shut-off and control valve, characterized in that the control valve maintains a constant GOR level through comparison with a given GOR level.

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