RU2017940C1 - Well gas lift - Google Patents

Abstract

FIELD: gas and oil producing industry. SUBSTANCE: gas lift has lift. Installed successively on lift from the bottom upwards are check valve, packer, circulating baffle valve, working valve and starting valves. The latter consist of body with inlet longitudinal slots and outlet channels, charging unit and seals located in body upper part, flexible member which form together with body an airtight chamber of compressed gas, and rod with channels. Rod is connected with its upper part to flexible member, and with its lower end, to gate with channels. Starting valve is provided with magnets and seating surfaces for them. Magnets are located in upper side part of rod above its channels and magnet seating surfaces on inner surface of body of starting channel. Magnets are arranged for interaction with seating surfaces during closing and opening of gate. EFFECT: higher reliability of gas lift due to reduced number of starting valves during starting and improved reliability of their closing in course of well operation. 3 dwg

Description

 The invention relates to the oil and gas industry, in particular to gas lift oil production and can be used to automatically start and maintain optimal bottomhole pressure during operation of the well.

 A well-known downhole installation, consisting of a working and starting valves with sensitive elements of electromagnetic action and a source of DC voltage.

 A well-known well installation comprising a hoist, on which a check valve, a packer, a jamming circulation valve, a service valve and start valves are sequentially installed from bottom to top.

 The start valves contain a housing with channels, an elastic element in the form of a bellows installed in the upper part of the housing, forming a chamber for compressed gas with it, a rod connected with its upper end to the bellows, and the lower end with a shutter. This installation has a number of disadvantages that greatly affect the reliability of its operation, in particular: it requires a large number of start-up valves to automatically start the well into operation at a limited pressure of the injected gas; it is possible that the start-up valves open after start-up, that is, during the operation and regulation of the operation of the well, as a result of which multipoint gas injection occurs in the lift.

 The first reason, first of all, is connected with the fact that each upstream start valve closes prematurely during gas injection into the lift, that is, without reaching a wide range of pressure changes at the bottom, therefore, additional valves are required to automatically start the well at a given starting gas pressure.

 The second reason is also related to the fact that the range between the opening and closing pressures of the valve is small (they are practically equal), and their openings to one degree or another depend on the gas pressure, which changes quite a lot during operation and regulation of the well.

 The aim of the invention is to increase the reliability of the installation by reducing the number of start-up valves at startup and ensuring reliable closure during operation of the well.

 The positive effect of the use of the installation is to increase oil production and (or) reduce the specific gas flow rate by providing a constant point of gas injection into the lift through the operating valve during operation and regulation of the well’s work, including lowering the cost and increasing the device’s service life by reducing the number of start-up valves, and eliminating the possibility of their opening after starting the well.

 This goal is achieved by the fact that the start valves are equipped with magnets and seating surfaces for them, while the magnets are located in the upper lateral part of the rod above its channels, and the seating surfaces of the magnet are on the inner surface of the start valve body, and the magnets are placed with the possibility of interaction of the magnets with the latter closing and opening the shutter.

 Magnets perform the function of a locking unit, resisting the movement of the rod at the time of opening and closing the start valve. Moreover, these magnets can be located in the side wall of the housing, and its seating surface in the stock.

 Figure 1 presents the installation diagram; figure 2 - starting valve in the closed state; figure 3 - method of calculating the installation.

 The installation contains a column of tubing (lift) 1, which is placed from the bottom up, the nipple of the check valve 2, packer 3, a silencing valve circulating 4, working 5 and starting valves 6.

 The start valves 6 include a housing 7 with inlet longitudinal slots 8, output channels 9, a charging unit 10 and seals 11. An elastic element 12 is installed in the housing 7 in the upper part, forming with it a sealed chamber 13 of compressed gas. The upper part of the rod 14 with channels 15 is rigidly attached to the elastic element 12. The rod 14 is also rigidly connected to the shutter 16 having channels 17, seals 18 and placed in the saddle 19 of the housing 7.

 In the upper part of the housing 7 there are seating surfaces 20 and 21 of a magnet 22 mounted on the rod 14. In the lower part of the housing 7 there are sockets 23 and a ball 24 that performs the function of a check valve.

S_j-F_j=P_пзj·S $\genfrac{}{}{0ex}{}{\text{*}}{\text{j}}$ (2) где j - порядковый номер пускового клапана в установке,
j=

-1; k - номер рабочего клапана;
P_j - давление зарядки камеры 13 сжатым газом, кг/см²;
S_j и S_j ^* - площадь поперечного сечения упругого элемента 12 и затвора 16, причем S_j = S_j ^*, см²;
F_j - сила сопротивления магнита 22, кг;
P_поj и P_пзj - давление жидкости в колонне насосно-компрессорных труб, которое равно давлению открытия и закрытия j-го клапана, кг/см²;
ΔР_j - величина изменения давления в камере 13 при полном открытии j-го клапана, кг/см²;
l_j - полный ход упругого элемента 12, см;
К_j - скорость нагрузки (механической жесткости) упругого элемента 12, см/(кг/см²).The equation of the balance of forces acting on the state of each starting valve at the time of opening and closing is as follows:
P _j ˙ S _j + F _j = P by _j ˙ S _j ^* (1) (P _j + ΔP _j ) S _j +

S _j -F _j = P _pzj · S $\genfrac{}{}{0ex}{}{\text{*}}{\text{j}}$ (2) where j is the serial number of the start valve in the installation,
j =

-1; k is the number of the operating valve;
P _j is the charging pressure of chamber 13 with compressed gas, kg / cm ² ;
S _j and S _j ^* - the cross-sectional area of the elastic element 12 and the shutter 16, and S _j = S _j ^* , cm ² ;
F _j is the resistance force of the magnet 22, kg;
P _poj and P _pzj - fluid pressure in the tubing string, which is equal to the opening and closing pressure of the j-th valve, kg / cm ² ;
ΔP _j - the magnitude of the pressure change in the chamber 13 with the full opening of the j-th valve, kg / cm ² ;
l _j is the full stroke of the elastic element 12, cm;
To _j is the load speed (mechanical rigidity) of the elastic element 12, cm / (kg / cm ² ).

,, (3) где V_j - объем камеры 13 при закрытом состоянии j-го пускового клапана, см³;
ΔV_j - величина изменения объема камеры 13 при полном открытии j-го клапана, см³.The value of Δ P _j is determined from the gas law in the isothermal process
ΔP _j = P

,, (3) where V _j is the volume of the chamber 13 when the j-th starting valve is closed, cm ³ ;
ΔV _j - the magnitude of the change in the volume of the chamber 13 with the full opening of the j-th valve, cm ³ .

,, (4)
F_j= -

S_j ,, (5)

F

ΔP_j·S_j+

S_j. (6)
Пусковые клапаны открываются и закрываются от давления жидкости в подъемнике, действующей на поперечную площадь упругого элемента 12 через затвор 16. При этом влияние давления газа на состояние клапана "открыт"-"закрыт" не происходит, так как дросселирование газа происходит в продольных прорезях 8, а площадь поперечных сечений затвора 16 и упругого элемента 12 между собой равны.From equations (1), (2) and (3) are determined
P _j =

,, (4)
F _j = -

S _j ,, (5)

F

ΔP _j · S _j +

S _j . (6)
The start valves open and close from the fluid pressure in the lift acting on the transverse area of the elastic element 12 through the shutter 16. In this case, the influence of gas pressure on the state of the valve “open” - “closed” does not occur, since gas throttling occurs in longitudinal slots 8, and the cross-sectional area of the shutter 16 and the elastic element 12 are equal to each other.

In the closed state of the valve, the magnet 22, sitting on the landing surface 20, resists the movement of the shutter 16 up. At the time of its opening, the shutter 16 moves upward under the action of fluid pressure in the tubing string 1. In this case, the magnet 22, coming out of contact with the surface 20, comes into contact with the surface 21. Ultimately, the difference between the opening and closing pressures start valves in the fluid stream, and the range between them is regulated by the parameters P _j and F _j .

 The principle of operation of the installation is as follows. After the valves are lowered into the well, the wellhead is installed and the packer 3 is planted, high pressure gas is supplied to the annulus. From this moment, fluid flows from the annulus into the pipe string 1 through gas lift valves 5 and 6 (if there is no packer then through pipe shoe 1). Valves 5 and 6 are in this case open from the pressure of the liquid in the pipe string 1. Gradually, the liquid level in the annulus decreases, and the moment comes when the first start valve is exposed (j = 1) and gas flows through it into the pipe string 1. In this case, a portion of the liquid is ejected from the pipes 1 onto the surface of the well due to the energy of the expandable gas. Here, the fluid pressure at the depth of the valves, including at the bottom of the well, drops. Moreover, when the pressure value at the bottom reaches the calculated (set) value, the first start-up valve closes, and gas enters the pipes 1 through the second start-up valve (j = 2). Next, the process is repeated similarly for subsequent starting valves until gas injection into the pipe string 1 through the operating valve 5 (j = k) is achieved.

 During the operation of the well with the injection of gas into the pipe string 1 through the operating valve, the pressure in the gas-liquid mixture flow (GHS) at the depth of the start-up valves is less than the pressure of their opening, therefore they are hermetically closed. Their opening is possible only when the well is shut down and restarted.

 In the installation, the working valve is similar to the starting one, only it does not have a magnet 22 with seating surfaces 20 and 21. In this case, the working valve automatically maintains a rational (optimal) bottom-hole pressure during well operation. That is, this valve changes the gas throughput in the event of a change in pressure in the gas distribution system, oil and gas gathering and (or) reservoir. This occurs due to the additional opening, or vice versa, overlapping the cross section of the input slots 8 with the movement of the shutter 16 in the saddle 19 of the housing 7.

 The calculation of the depth of location and characteristics of the valves is as follows (figure 3).

1. For the operating valve:
- the distribution of gas pressure is calculated by the barometric formula from the wellhead to the shoe 1 with a minimum (P _r ^min ) and maximum (P _r ^max ) gas pressure (lines 1 and 2); there is a maximum gas pressure on the shoe shoe (P _GB ^max );
- the distribution of pressure in the flow of formation fluid is calculated according to the equation of motion of the GHS on the section from the bottom up at a given rational bottomhole pressure (line 3); there is pressure in the fluid flow on the shoe of pipes 1 (P _B );
- checks the possibility of a gas breakthrough through the shoe 1, that is, the inequality P _GB ^max > P _B ; if there are conditions for gas breakthrough through the shoe, then one of the following solutions is adopted: a) packer 3 descends into the well and the pipe and annulus are disconnected; b) the value of P _p ^{max is} limited by the wellhead gas pressure regulator; c) the design bottomhole pressure is set more than planned to exclude the possibility of a breakthrough of gas through the shoe 1;
- selects the installation depth of the valve (N _k ), where the liquid pressure P _pc (line 3) is less than the minimum gas pressure P _gk ^min (line 1) by ΔР _k ;
- gas _flow rates V _gi are set at intervals _{, the} distribution of pressure in the _{hydraulic fluid} is calculated for each i-th V _g from the depth of valve 5 to the wellhead at P _pc = const (lines 4-7) and the dependence P _y = f (V _g );
- using the dependence P _y = f (V _g ) is the maximum gas flow rate (V _gk ^max ) corresponding to the wellhead pressure P _y ^max ;
- determines the cross-sectional area of the longitudinal slots 8 for the operating valve at V _g ^max ; R _gk ^min and R _pc using equations describing the movement of gas through holes;
- the pressure of charging the chamber 13 with compressed gas for the operating valve is found using the force balance equations acting on its operating state.

2. For start valves:
- the distribution of pressure in the filling fluid is calculated from the wellhead to the bottom of the well at P _at ^min (line 8);
- the distribution of gas pressure in the section from the wellhead to the shoe 1 is calculated at a starting gas pressure P _pus (line 9);
- selects the installation depth of the first starting valve H ₁ , where the liquid pressure (line 8) is less than the gas pressure (line 9) by Δ P ₁ ^min ; here, the opening pressure of the valve will be equal to R _p.o1 = P _g1 - Δ P ₁ ^min <P _g1 ^max (this condition ensures automatic restart of the well at P _p ^max ; P _g1 ^max - corresponds to the gas pressure at a depth j = 1 valve at P _p ^max ;
- sets the possible rate of pumping liquid (Q _l1 ) during gas injection through a depth of H ₁ , based on the bottomhole pressure P _s1 achieved;
- calculated pressure in the liquid flow at a depth _H1 at _P1 and P Q _x1, which is taken equal to the pressure P _pz1 closing valve (line 10), wherein R _pz1> P _n1 ^max (this condition ensures reliable closure of the valve during well operation);
- the gas flow rate V _gi is set at _intervals , calculated for each i-th V _g , wellhead pressure at Р _пз1 and Q _ж1 , the dependence Р _у = f (V _g ) is built and the maximum gas flow rate V _g1 ^max corresponding to Р _у ^{min is} determined;
- determines the cross-sectional area of the inlet slots 8 for the first starting valve at V _g1 ^max , P _g1 and P _PZ1 ;
- is the charging pressure of the chamber 13 with compressed gas (P ₁ ) and the resistance force of the magnet 22 (F ₁ ) using equations (4) and (5);
- the depth of the second starting valve H ₂ is selected, where the liquid pressure (line 10) is less than the gas pressure (line 9) by Δ P ₂ ^min ; here, the opening pressure of the second valve will be equal to Р _Po2 = Р _g2 - Δ Р ₂ ^min <P _g2 ^max (Р _g2 ^max - corresponds to the gas pressure at a depth j = of the 2nd valve at Р _р ^max );
- sets the possible rate of pumping liquid (Q _W2 ) during gas injection through a depth of H ₂ , based on the bottomhole pressure P _s2 achieved;
- the distribution of pressure in the fluid flow is calculated from the bottom to the depth Н ₂ at Р _З2 and Q _ж2 and the fluid pressure is determined at this depth, which is taken to be equal to the closing pressure of the second start-up valve Р _пз2 (line 11), and Р _пз2 > Р _п2 ^max ;
the gas flow rate V _gi is set at intervals _{, the} wellhead pressure is calculated for each i-th V _g at Р _пз2 and Q _ж2 , the dependence Р _у = f (V _g ) is built and the gas flow rate V _g2 ^max corresponding to the pressure Р _у ^{min is} determined;
- is determined by the flow area inlet slots 8 for the second trigger valve when _r2 V ^max, P and P _{r2 pz2;}
- find the parameters P ₂ and F ₂ for the second start valve using formulas (4) and (5).

 The calculation for subsequent starting valves is carried out similarly to the first and second until the point of injection of gas into the pipe columns 1 through the operating valve is reached.

Claims (1)

 A GAS LIFT WELL INSTALLATION, comprising a hoist on which a check valve, a packer, a silencing circulation valve, a service valve and start valves are sequentially installed from bottom to top in the form of a housing with inlet longitudinal slots and outlet channels, a charging and sealing unit located in the upper part of the housing, resilient an element forming a sealed chamber of compressed gas with it, and a rod with channels, connected by the upper part with an elastic element, and the lower one with a shutter with channels, characterized in that, in order to increase reliability in work by reducing the number of start-up valves at start-up and ensuring their reliable closure during well operation, it is equipped with magnets and seating surfaces for them, while the magnets are located in the upper lateral part of the rod above its channels, and the magnet seating surfaces are on the inner surface the case of the starting valve, and the magnets are placed with the possibility of interaction with the seating surfaces when closing and opening the shutter.

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