RU2020371C1 - Method for transportation of water-gas-oil mixture - Google Patents

Abstract

FIELD: transportation of water-oil-gas mixtures. SUBSTANCE: mixture is delivered from collecting station through pipeline and through unit for cleaning it of mechanical impurities to the suction end of double-screw pump from its outlet, into a transport line. At the pump outlet the mixture is divided into liquid and gas phases by means of flow divider. The other part of liquid phase is returned through bypass pipeline with control gate to pump suction so as to maintain total gas content at the suction side below the stalling limit. EFFECT: higher efficiency. 1 dwg

Description

 The invention relates to the oil industry, and in particular to methods of transporting gas and oil mixtures and installations for their implementation.

 A known method of the main transport of gas-saturated oil or gas condensate with stepwise stabilization by throttling to a pressure within the vapor pressure of the condensate, in which the separated gas is used at the stabilization site, and often simply burn [1]. The method is applicable for pumping only very high gas condensate flow rates, is uneconomical and environmentally hazardous.

 A known method and installation for the joint transport of oily liquid and gas using a centrifugal pump [2].

 However, this method can only be used in systems for collecting and transporting oil well products with a small gas factor.

 A known method of transporting water-gas-oil mixtures in systems for the collection and preparation of oil fields, comprising supplying the mixture from the collection point via a pipeline through a filter cleansing of mechanical impurities to the intake of a twin-screw pump and from its exit to the transport highway [3].

 This method is not efficient and reliable enough, since it allows you to pump only a strictly defined volume of a gas-liquid mixture (GHS) per unit time, equal to the capacity of the pump, as well as a mixture with a gas phase content of not more than 60%. With a decrease in the volumes (expenses) of the pumped mixture, as well as with an increase in the gas content of the mixture, the pump and the installation as a whole fail and the transportation method is ineffective.

 The purpose of the invention is to increase the efficiency and reliability of transportation of the gas-oil mixture when changing its costs, as well as volumetric phase ratio.

 This goal is achieved by the fact that in the known method of transportation, the gas-oil mixture from the pump discharge is fed to a separator apparatus, from where the gas phase and part of the liquid phase are sent to the transport line, and the other part of the liquid phase, determined according to the found dependence with an empirical coefficient, is returned to reception pump, maintaining the total gas content at the reception below the maximum stall. The installation for transporting water-gas-oil mixtures additionally contains a separator apparatus installed behind the discharge line of the twin-screw pump, equipped with gas and liquid pipelines sent to the transport line, and a bypass pipeline with an adjustment valve to supply part of the liquid phase to the intake of the screw pump.

 Bypassing the liquid phase to the intake of the pump from the GHS separation unit ensures that the total gas content at the intake of the twin-screw pump is below the maximum stall regardless of the change in the flow rate of the GHS and gas content.

 The proposed system of the method for self-regulation: when the pressure (flow rate and gas content of the GHS) changes at the pump intake, the volume of the bypassed liquid changes, which ensures optimal gas content at the pump intake and, accordingly, the reliability and efficiency of the transportation process.

The capacity of the bypass line is preliminarily adjusted based on the condition that the volume of the mixture supplied to the pump intake should not exceed its capacity of 180 m ³ / h
Q _b + Q _f.ph. + Q _gas = 180, (1), where Q _b is the volume of bypassed liquid, m ³ / h;
Q _J.F. - the volume of the liquid phase of the mixture, m ³ / h

· K $\genfrac{}{}{0ex}{}{\text{г}}{\text{v}}$ , (2) где W - обводненность смеси, % , а также эмпирическую зависимость коэффициента объемного газосодержания смеси от давления на входе в насос Р_вх, МПа,
K $\genfrac{}{}{0ex}{}{\text{г}}{\text{v}}$ =

, (3) получают формулу для вычисления объема байпасируемой жидкости в зависимости от давления на входе в насос, обводненности и объема перекачиваемой жидкости
Q_б=180-Q

1+

·

. (4)
Настроив пропускную способность байпасной линии по расчетной величине Q_б (4), осуществляют следующую последовательность операций: подача и очистка (ГЖС) от мехпримесей в гравитационном отстойнике, подача смеси на прием насоса, подача смеси с выкида насоса в аппарат-разделитель, где происходит разделение ГЖС на газовую и жидкую фазы и откуда газовая и часть жидкой фазы направляются в транспортную магистраль, а другая часть жидкой фазы по байпасной линии с регулировочной задвижкой направляется на прием насоса, поддерживая общее газосодержание на приеме ниже предельного срывного вне зависимости от изменения расхода и газосодержания ГЖС за счет саморегулирования предлагаемой системы транспортирования ГЖС.Using the ratio
Q _gas = Q _oil · K $\genfrac{}{}{0ex}{}{\text{g}}{\text{v}}$ = Q

K $\genfrac{}{}{0ex}{}{\text{g}}{\text{v}}$ , (2) where W is the water cut of the mixture,%, as well as the empirical dependence of the volumetric gas content coefficient of the mixture on the pressure at the pump inlet P _in , MPa,
K $\genfrac{}{}{0ex}{}{\text{g}}{\text{v}}$ =

, (3) get a formula for calculating the volume of the bypassed liquid depending on the pressure at the inlet to the pump, the water cut and the volume of the pumped liquid
Q _b = 180-Q

1+

·

. (4)
Having adjusted the capacity of the bypass line according to the calculated value of Q _b (4), the following sequence of operations is carried out: feeding and cleaning (GLC) of mechanical impurities in the gravity settler, supplying the mixture to the pump intake, feeding the mixture from the pump discharge to the separator, where separation occurs GHS on the gas and liquid phases and from where the gas and part of the liquid phase are sent to the transport line, and the other part of the liquid phase is sent to the pump intake along the bypass line with the adjustment valve, maintaining the total gas content on reception of the lower limit shear regardless of the flow rate and gas content changes due to self-GLM GLM proposed transport system.

 The drawing shows a diagram of a method for transporting a gas-oil mixture.

 According to the collectors of the collection system, through the group metering units (GZU), the GHS comes to the installation, which contains a gravity settler 1, equipped with a discharge collector 2 and collector 3 for collecting sludge into the storage device 4, equipped with a flare line 5, with a twin-screw pump 6, equipped with a pressure collector 7 and a suction collector (discharge manifold 2 of a gravity settler 1), a gas-liquid separator 8, equipped with M-shaped partitions 9, a vertical half-wall 10, nor These 11 and 12 the upper level controls, gas discharge line 13 with a measuring device 14 and the flow controller 15, discharge manifold 16 from measuring device 17 and controller 18 the fluid flow and the bypass line 19 with a measuring device 20 and control valve 21.

 Gravity settler 1 is a gravity separator in which the incoming GHS is freed from mechanical impurities and inclusions of formation rock under the influence of the phase density and gravity, is made from a pipe with a diameter of 400-1200 mm, length 8-12 m, the dimensions are determined by the total flow rate of the gas-liquid mixture. The sump is equipped with fittings for input of well production and output of purified liquid.

 The pump of the screw brand 2VV-180/25 with an electric motor VAO-2-315M4 is made in an explosion-proof version.

Gas-liquid separator 8 is designed to separate the production of wells into liquid and gas phases. Well production through the injection pipeline enters a gas-liquid separator, in which there is a sharp drop in flow rate and phase separation. The separator with a volume of 50-200 m ³ is equipped with a volumetric switchgear in the form of M-shaped partitions 9, consisting of vertical plates that are joined to each other along the flow direction. The partition is mounted from packages of plates and forms zigzag channels in the path of fluid movement, when passing through them, the mixture speed is leveled due to hydraulic resistance, and the gas separation volume increases due to the formation of a new contact surface. The fluid level is controlled by level controls 11 and 12.

 The storage device 4 is designed to collect and accumulate sludge, as well as liquid leaks through the pipe 22 through the mechanical seals of the working pump and fluid intake in the event of an accidental discharge from the gas-liquid separator through the pipe 23. The device ensures the environmental friendliness of the process.

 Installation works as follows.

 The production of wells through pipelines through the GZU and from the general prefabricated collector enters the gravity settler 1, in which the separation of mechanical impurities takes place. The gas-liquid mixture, purified from solids, enters the pump intake, the inlet and outlet lines of which are equipped with pressure gauges, and the bearing supports are equipped with temperature sensors. In the pump housing, in the places of mechanical seal leakage, fittings for collecting leaks through the pipe 22 are cut into the storage device 4. From the discharge line of the pump 6, the gas-liquid mixture enters the gas-liquid separator, where it passes through the M-shaped partitions 9 and where there is intensive gas separation phase. At the outlet of the gas-liquid separator, the liquid phase is divided into two streams: the main (pressure header 16) and the bypass (bypass line pipe 19). The main fluid flow through the metering and control system enters the discharge manifold 24, and part of the fluid through the bypass line 19 to the pump intake. The gas phase passes through the gate valve system and the flow regulator 15 to the discharge manifold 24. When the pressure is higher than the norm established by the technological mode on the device, the emergency relief valve is activated, and through the pipe 23 the gas is vented to the storage device and then to the candle via the flare line 5 The maximum and minimum levels of the liquid phase in the gas-liquid separator are controlled by the primary converter of the lower and upper level sensor-relay.

 Self-regulation of the proposed gas-oil mixture transportation system is due to the fact that when the pressure at the pump inlet decreases, the actual volume of free gas in the pipeline increases, violating the optimal ratio between the gas and liquid phases, but the pressure drop between the separator 8 and the pump leading to the intake increases collector 2, which leads to an increase in the rate of fluid flow along the bypass line, and hence the volume of bypassed liquid. As a result, the gas and liquid phases return to the optimal ratio. Similarly, the system reacts to an increase in pressure at the pump inlet. This ensures the reliability and efficiency of the method.

 PRI me R. Pumped GZHS Kinyaminskogo field NGDU "Mayskneft".

·

= 74,6 м³/ч.Parameters of the pumped medium: Oil volume, m ³ / h 13.05 Water volume, m ³ / h 1.54 Water cut,% 10.6 Gas factor, m ³ / m ³ 69.8 Inlet pressure, MPa 1.0 Temperature pumping, K 293 Oil density, kg / m ³ 872
Using the above data, determine the volume of bypassed fluid by substituting them in the formula (4)
Q _b = 180-14.59 · (1+

·

= 74.6 m ³ / h.

= 13,05 ·

= 90,8 м³/ч - в условиях трубопровода или 908 м³/ч в нормальных условиях.The following amount of gas is pumped (3)
Q ₁ = Q _n

= 13.05

= 90.8 m ³ / h - under pipeline conditions or 908 m ³ / h under normal conditions.

Thus, the total volume of the mixture at the inlet to the pump corresponds to the capacity of the pump, i.e. 180 m ³ / h:
Q _b + Q _g + Q _n + Q _c = 74.6 + 90.8 +
+ 13.05 + 1.54 = 179.99 m ³ / h.

(5) где S_рег - площадь проходного отверстия регулировочной задвижки, м²;
Р₁ и Р₂ - давление в газожидкостном аппарате-разделителе и на приемном патрубке насоса соответственно, Па;
δ - плотность жидкости, кг/м³; рассчитывают площадь проходного отверстия регулировочной задвижки при перепаде давлений
P₁- P₂ = 2,5 - 1,0 МПа,
S_o=

·

=0,000353 м²
Соответственно максимальный переток по байпасной линии при максимальном перепаде давлений в 2,5 МПа при данной настройке составит
Q

= 0,000353 ·

= 0,0267 м³/c = 96 м³/ч .Based on the dependency
Q _b = S

(5) where S _reg is the area of the orifice of the control valve, m ² ;
P ₁ and P ₂ - pressure in the gas-liquid separator and at the inlet of the pump, respectively, Pa;
δ is the density of the liquid, kg / m ³ ; calculate the area of the bore of the control valve with a differential pressure
P ₁ - P ₂ = 2.5 - 1.0 MPa,
S _o =

·

= 0,000353 m ²
Accordingly, the maximum overflow along the bypass line with a maximum pressure drop of 2.5 MPa with this setting will be
Q

= 0,000353

= 0.0267 m ³ / s = 96 m ³ / h.

·

= 0,000852 м².Thus, the system configured for pumping the GZhS of the Kinyaminskoye field remains efficient and reliable at a pressure drop of 0 to 2.5 MPa due to self-regulation of costs along the bypass line from 0 to 96 m ³ / h. If you need to bypass large volumes, for example, up to 180 m ³ / h, you will need to reconfigure the control valve to the cross-section
S _o =

·

= 0.000852 m ² .

The proposed method and installation are effective for pumping GHS with flows from 0 to 180 m ³ / h (for pumping high costs increase the number of pump units), and it is possible to pump one gas.

The drop in the GHS consumption to a minimum up to 0 m ³ / h can be in two cases.

1. The pump is disconnected from the receiving pipeline (the valve is closed or the flow rate of the wells has decreased sharply or even equal to zero, ie the wells are stopped). In this case, the associated gas flow rate is also zero, and the pump operates in a closed cycle almost "on its own." In this case, the bypass flow rate is equal to or close to the pump capacity, i.e. 180 m ³ / h.

 The liquid circulates through the chain: inlet pipe - pump - pressure (discharge) pipe - separator - bypass line - pump inlet pipe.

The intake of 180 m ³ / h of liquid to the intake pipe through the bypass line is provided by an increasing pressure drop between the separator and the pump receiving pipe and an increase in the fluid flow rate along the bypass line.

2. The drop in fluid flow to 0 m ³ / h is accompanied by the flow of gas at an arbitrary flow rate. In this case, the liquid to ensure lubrication and cooling of the mechanical seal of the pump flows through the bypass line in quantities determined by the preliminary setting of the adjusting valve.

Due to the limited capacity of the pump for a mixture of 180 m ³ / h, the gas flow in the pipeline through the pump inlet is
Q _g = 180 - Q _b .

In the example under consideration at the Kinyaminskoye field, the gas flow in the pipeline Q _g = 180 - 74.6 = 105.4 m ³ / h - at a pressure at the pump inlet of 1.0 MPa or 1054 m ³ / h of gas under normal conditions (P _in = 0.1 MPa, T = 293 K).

 The advantages of the proposed method in comparison with the method and installation known for the prototype are determined by the possibility of pumping the GHS with a flow rate and gas content of up to 100% that vary practically from 0 to pump performance. The efficiency and reliability of the proposed method and installation reduce the risk of environmental pollution and ensure the cost-effectiveness of the transportation of gas and oil mixtures.

Claims (1)

METHOD FOR TRANSPORTING A WATER-GAS-OIL MIXTURE, comprising supplying a mixture from a collection point through a pipeline through a mechanical impurities purification unit to a twin-screw pump intake and from its outlet to a transport line, characterized in that the mixture is separated into liquid and gas phases from the pump outlet using a separator, then the gas phase and part of the liquid phase are sent to the transport line, and the other part of the liquid phase in the volume determined according to the dependence
Q _b = 180-Q

1+

,
where Q _b is the volume of bypassed liquid, m ³ / h;
Q _zhf is the volume of the liquid phase of the mixture, m ³ / h;
ω is the water content of the mixture,%;
P _I - pressure at the inlet to the pump, MPa,
return by means of a bypass pipe with an adjustment valve to the pump intake, maintaining the total gas content at the intake below the tearing limit.

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