RU2695394C1 - Device for hydraulic protection of an electric motor for submersible installations for maintaining formation pressure (versions) - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: group of inventions relates to oil production and can be used in installations for hydraulic protection of submersible electric motors for electric-centrifugal pumps used for pumping fluid into formation to maintain reservoir pressure in well. Hydraulic protection device includes a compensator, an electric motor, a protector and a submersible pump installed in series from top to bottom. Tread comprises a shaft with an axial bearing and radial bearings installed on it, as well as a head, a nipple, a compensating module with a housing, in which a nipple, an end seal and a compensating element are installed. Compensator comprises a housing, a nipple and a head. Inside the head and nipple of the protector there is a unit for protection of the end seal, which includes a pump device installed on the shaft, a labyrinth in the form of a static bushing installed with a radial gap in relation to the shaft with formation of a closed area, which does not have hydraulic connection with the compensating element.

EFFECT: inventions are aimed at improvement of device operation reliability.

9 cl, 4 dwg

Description

The invention relates to the field of oil production and can be used in installations for hydraulic protection of submersible electric motors for electric centrifugal pumps used to pump fluid into the reservoir to maintain reservoir pressure in the well.

For the first object from the group of inventions, the following technical solutions are known as analogues.

A device for hydraulic protection of an electric motor of a submersible borehole pump for extracting formation fluid from the description of US Pat. No. 6,307,290 B1, published October 23, 2001, IPC Н02К 5/132, F04D 13/08. The device includes a tread comprising a shaft, thrust and radial bearings and at least one stage, which includes a cylindrical body, a tube surrounding the shaft coaxially installed inside it, a first and second nipple, at least one damping sleeve, mechanical seal and annular piston mounted with the possibility of reciprocating motion in an annular chamber formed in the space between the cylindrical body and the tube, while dividing this annular chamber into two sections stka filled with dielectric and respectively arriving from the annulus formation fluids. Accordingly, the movable mechanical module, which is part of the tread, separates the formation fluid and the reservoir fluid coming from the annulus, is an annular piston.

When using the known technical solution, low reliability is found when working in a submersible installation for injecting fluid into the formation to maintain reservoir pressure in the well. In addition, there is a high probability of mechanical impurities entering the area of the mechanical seal, there is no guaranteed positive pressure difference between the oil and the injected liquid in the area of the mechanical seal, which is necessary for reliable operation of the seal. Without forced feeding, oil cannot flow arbitrarily down into the area of the mechanical seal and flow into the surrounding tread, since the density of the oil is less than the density of water.

As part of a device for hydraulic protection of a borehole pump electric motor, a tread is known that comprises a shaft, thrust and radial bearings and at least one protection stage, which includes a cylindrical body, a tube coaxially installed inside it, a tube, first and second nipples, at least one damping sleeve, mechanical seal and annular piston mounted with the possibility of reciprocating motion in an annular chamber formed in the space between the cylindrical them housing and the tube, thus dividing this annular chamber into two portions, filled, respectively, the permittivity and arriving from the annulus formation fluids. To the end face of the annular piston in contact with the formation fluid are attached two protruding protective ring elements protruding beyond the contours of the annular piston adjacent to the inner surface of the housing and to the outer surface of the tube, respectively. The space between the protective ring elements and the surface of the tread elements to which they are adjacent is filled with protective grease. Moreover, the patented device contains installed sequentially from top to bottom: pump, protector, electric motor, compensator (according to patent RU 2353812, class F04D 13/10, publ. 04/27/09).

When using the known technical solution exhibits low reliability when working in submersible installations for pumping fluid into the reservoir to maintain reservoir pressure in the well. There is a high probability of mechanical impurities entering the area of the mechanical seal; there is no guaranteed positive pressure difference between the oil and the injected liquid in the area of the mechanical seal, which is necessary for reliable operation of the seal. Without forced feeding, oil cannot flow arbitrarily down into the area of the mechanical seal and flow into the surrounding tread, since the density of the oil is less than the density of water.

For the second object from the group of inventions, the following technical solutions are known as analogues.

As part of the device for hydraulic protection of a submersible oil-filled electric motor, a compensator is known that contains an elastic oil-resistant bag, impermeable to formation fluid, located in the lower part of the motor housing, the bag being enclosed in a casing with an opening for communication with formation fluid (according to USSR copyright certificate N 118033, class H02K 5/10, 1958).

When using the analyzed device, undesirable properties are manifested. So, when operating wells in a reservoir fluid that contains free gas, the density of the gas-liquid mixture may be less than the density of the oil inside the diaphragm, this leads to the impossibility of oil flowing through the mechanical seal in order to cool and lubricate the friction pair.

As part of a device for hydraulic protection of a borehole pump electric motor, a compensator is known comprising a base, a housing, a nipple and a compensating element. In this case, the main elements of the installation are arranged as follows: from top to bottom in series: a pump, protector, electric motor and compensator (according to patent RU 2353812, class F04D 13/10, publ. 04/27/09).

The obstacle to achieving a technical result when using a device for hydraulic protection with such a compensator is that when operating wells in the reservoir fluid which contains free gas, the density of the gas-liquid mixture may be less than the density of the oil inside the compensating element, this makes it impossible to squeeze the oil out of the compensating element for due to the difference in densities that liquids have inside and outside the compensating element through the mechanical seal, for the purpose of cooling and lubrication pair of friction seals. Therefore, the known device has insufficient reliability.

As a prototype for each embodiment of the invention selected technical solution according to patent RU No. 2353812.

The proposed variants of the invention are combined in a group, because aimed at solving a technical problem, which consists in creating a device for hydraulic protection of an electric motor for submersible installations for maintaining reservoir pressure, which is reliable in operation.

For the first invention from the group, the technical problem is solved by the fact that in the device of hydraulic protection of the electric motor of the submersible installation for maintaining reservoir pressure, including a compensator, electric motor, protector, submersible pump, the protector contains a shaft with axial support and radial bearings mounted on it, as well as a head , a nipple, a compensating module with a housing in which a nipple, a mechanical seal and a compensating element are installed, and the compensator contains a housing, a nipple and a head, with a new The following are applied: a compensator, an electric motor, a tread, a submersible pump are installed sequentially from top to bottom, while inside the head and nipple of the tread there is a mechanical seal protection unit, which includes a pump device mounted on the shaft, a labyrinth in the form of a static sleeve installed with a radial clearance of relative to the shaft with the formation of a closed region that does not have a hydraulic connection with the compensating element.

Some aspects of the present invention:

- the pumping device includes a sleeve with a screw thread mounted on the shaft.

- the composition of the pumping device includes a labyrinth-screw pair.

- the pump device includes a threaded sleeve mounted on the shaft and mounted in a nipple with a radial clearance relative to the sleeve of the diaphragm support.

- the compensating element is made in the form of a diaphragm.

- the compensating element is made in the form of a piston.

For the second invention from the group, the above technical problem is solved by the fact that in the device of hydraulic protection of the electric motor of a submersible installation for maintaining reservoir pressure, including a compensator, an electric motor, a protector, a submersible pump, the protector contains a shaft with an axial support and radial bearings mounted on it, as well as a head , a nipple, a compensating module with a housing in which a nipple, a mechanical seal and a compensating element are installed, and the compensator comprises a housing, a nipple and heads ku, the following is new: the compensator, electric motor, protector, submersible pump are installed sequentially from top to bottom, the housing, the nipple and the head of the compensator form a closed region for collecting free gas, hydraulically connected to the engine and not having a hydraulic connection with the annulus, while the compensator is made with a check valve designed to drain oil and gas.

Some aspects of this invention:

- a check valve is installed in the head;

- the check valve is installed so that the oil and gas outlet is carried out in the lower direction, while the check valve can be installed in the head.

The essence of the first embodiment of the invention is illustrated as follows.

The presence of a mechanical seal protection unit inside the tread head and nipple reduces the likelihood of failure of the seal, as it provides the required positive pressure difference between the oil and the reservoir fluid and reduces the likelihood of mechanical impurities entering the seal installation area.

The lack of hydraulic connection with the compensating element reduces the likelihood of mechanical impurities entering the seal installation area, since when the unit is turned on and off, fluid from the annulus flows into the compensating module and compensates for the thermal change in the oil volume. The absence of hydraulic connection implies that the liquid will enter the compensation module through a separate channel that connects the compensation module to the annulus.

Mounted on the shaft, the pumping device creates a guaranteed positive pressure drop in the area of the mechanical seal between the oil and the annulus, which is necessary for reliable operation of the seal, there is no likelihood that the fluid injected into the formation can penetrate into the tread. At the same time, the slowly flowing oil provides lubrication and cooling of the friction pair in the seal. Without forced feeding, oil cannot flow arbitrarily down into the area of the mechanical seal and flow into the surrounding tread, since the density of the oil is less than the density of water.

The manufacture of the pumping device in the form of a screw and a sleeve, which may have a labyrinth-screw cut, a labyrinth-screw pair allows you to compactly install the device in the tread. It is possible to use a centrifugal stage as a pumping device, but its diametrical dimensions are significantly higher, which will lead to a more complicated and expensive construction.

If the pump device includes a threaded sleeve mounted on the shaft and installed in a nipple with a radial clearance in relation to the sleeve, the diaphragm support. This will reduce the cost and improve the manufacturability of the manufacture of this device.

Moreover, the diaphragm support may be connected to the pipe of the diaphragm support assembly by means of a screw or pin connection. Traditionally, the diaphragm support assembly is made by welding parts and subsequent machining of the welded part, which has a large length and low stiffness. Therefore, there are technological difficulties in ensuring the required tolerances in the pair pair. A new technological solution solves these problems.

If the labyrinth is made in the form of a static sleeve installed in the head, with a radial clearance relative to the shaft, with the formation of a closed region that does not have hydraulic connection with the compensating element, then oil or free gas will collect in this area. Contact with the annulus and with water pumped into the formation is limited by the radial clearance. This design protects the mechanical seal from contact with mechanical impurities at all stages of the installation: when lowering the hydraulic protection into the well, starting or stopping the engine. Since the pumped liquid enters the compensation module through separate channels.

The proposed arrangement of vertically installed compensator, electric motor, tread and pump is determined by the features of the installation, which pumps fluid (water) into the reservoir to maintain reservoir pressure.

The implementation of the compensating element in the form of a diaphragm allows you to make a pump device with a lower pressure, since the diaphragm, in comparison with other types of compensating elements, most easily changes its shape.

If the area between the tread body and the diaphragm has a hydraulic connection with the annulus only in its lower part, this will protect the diaphragm from contact with mechanical impurities, which, due to their higher density than the density of water, cannot move in the upper direction.

Thus, the present invention according to the first embodiment is aimed at preventing mechanical impurities from entering the installation area of the mechanical seal and ensuring a guaranteed positive pressure difference between the oil and the pumped liquid (water), which is a necessary condition for reliable operation of the seal.

For the second object from the claimed group of inventions, the possibility of a different arrangement is eliminated than the compensator, electric motor, tread and pump successively installed from top to bottom due to the fact that the tread transmits torque from the engine to the pump that pumps water into the well. And the compensator is installed on the opposite side and its task is to eliminate the probability of failure of the upper motor bearing due to the formation of a gas region in the upper part of the engine and partial leakage compensation through the mechanical seal in the tread.

The compensator in serial submersible installations for pumping fluid into the reservoir in order to increase reservoir pressure is installed above the engine, a diaphragm is used as a compensating element. Without forced feeding, oil cannot flow arbitrarily down into the area of the mechanical seal and flow into the surrounding tread, since the density of the oil is less than the density of water.

The diaphragm in these conditions only works as a reservoir, from which the oil does not have the ability to flow into the tread. The compensator is better able to cope with this task, where the body, nipple and head form a closed region hydraulically connected to the engine and not having a hydraulic connection with the annulus. A sealed metal case without a diaphragm has a lower cost and higher resource than a case with a diaphragm, the inner region of which is connected to the annulus.

In fact, the present invention leads to a new concept of operation of the hydraulic protection device, due to the design of a diaphragm-free compensator. Free gas is collected in the compensator, which can penetrate through the diaphragm in the tread. Dissolved gas penetrates the diaphragm when the unit is turned off, the oil temperature is lower than when the engine is running. When the engine is turned on, the oil temperature rises, the dissolved gas is released and collected in the free form in the upper part of the installation, in the compensator. At the first stage of work, there is enough oil in the tread, and when the engine is turned on due to a temperature change in the oil volume, free gas is removed through the check valve installed in the head into the annulus. At the second stage, the amount of oil in the tread is reduced due to the fact that the oil flows out through the mechanical seal in a planned manner. The pressure in the gas region, in the upper part of the compensator, is no longer enough to open the check valve, which opens at a pressure of about one atmosphere, but in this case, the gas region in the compensator, like a gas spring, forces the oil out of the compensator into the tread.

If the non-return valve opens in the lower direction, this reduces the likelihood of mechanical impurities entering the valve pair, which can lead to leakage. Due to their higher density, mechanical impurities cannot move upward in a liquid.

Based on the foregoing, embodiments of the invention make it possible to use a hydraulic motor protection device for submersible reservoir pressure maintenance installations in various combinations of new tread and compensator designs integrated into the corresponding hydraulic protection device separately or separately, while ensuring reliable operation of the device due to:

- separation of mechanical impurities from the installation area of the mechanical seal;

- ensuring a guaranteed pressure difference between the oil and the injected fluid in the area of the mechanical seal;

- elimination of mechanical impurities in the zone of the check valve of the compensator;

- execution of the compensator body without a diaphragm.

The invention is illustrated by figures, which depict:

FIG. 1 - submersible electric centrifugal installation for pumping fluid into the reservoir to increase reservoir pressure;

FIG. 2 - the lower part of the tread, a longitudinal section;

FIG. 3 - compensator, longitudinal section;

FIG. 4 - diagrams of pressure changes in the oil and in the annulus.

The device of hydraulic protection oil of a filled motor of a submersible installation for pumping water into the reservoir to increase reservoir pressure comprises a tread 1 with a compensating element in the form of a diaphragm 2 installed between the electric motor 3 and pump 4, and a compensator 5 mounted above the engine. The installation descends into the well on pipes 6.

The tread 1 comprises a nipple 7, inside of which a shaft 8 is mounted, a mechanical seal 9 is installed on the shaft, below which a static sleeve 11 is installed between the nipple 7 and the tread head 10, forming a closed region 12 with a nipple 7 in the area of the mechanical seal. On the shaft 8 is installed a pumping device in the form of a sleeve 13 with a helical groove. A diaphragm support 14 is installed in the nipple 7. Outside the shaft 8, a pipe 15 of the diaphragm support assembly is mounted, which is connected to the support 14 by means of a screw 16. A sleeve with a helical groove 13 and a diaphragm support 14 are interfaced by a radial clearance and form a pumping device. The hydraulic connection of the compensating element in the form of a diaphragm 2 with the annulus is carried out through the channel 17.

The compensator 5 comprises a base 18, with a channel 19, a head 20, inside which valves 21 are installed in the vertical channel 22. The head 20, the base 18 and the housing 23 installed between them form a closed area 24, hydraulically connected to the engine through the channel 19.

Line 25 is a plot of the pressure change in the oil, which is inside the tread 1, engine 3 and compensator 5.

Line 26 is a plot of the pressure change of water injected into the well.

Line 27 is a plot of the pressure change in the oil, which is located inside the tread 1, engine 3 and compensator 5, provided that there is no excess oil, the oil and water pumped into the well are separated by a mechanical seal.

Water squeezes the oil, which is located in the tread, engine and compensator up, just as water squeezes out any object of lower density due to the strength of Archimedes. If a diaphragm is installed in the compensator, it swells and, due to the elastic forces, stops the further rise of the oil. But there is no mechanism that would force the oil down. Diagrams of pressure changes 25, 26, 27 allow you to calculate the pressure drop between oil and water. The diaphragm in these conditions only works as a reservoir, from which the oil does not have the ability to flow into the tread. The compensator is better able to cope with this task, where the body, nipple and head form a closed region hydraulically connected to the engine and not having a hydraulic connection with the annulus. A sealed metal case without a diaphragm has a lower cost and higher resource than a case with a diaphragm, the inner region of which is connected to the annulus.

The hydraulic motor protection device operates as follows.

When you turn on the electric motor 3 (or increase the number of revolutions), the dielectric fluid located in its internal cavity is heated and its volume increases. The pressure of the dielectric fluid in the inner cavity of the electric motor and the inner cavity of the compensating element hydraulically connected with it in the form of a diaphragm 2 increases, so that the pressure does not cause the mechanical seal 9 to open, the check valves 21 are opened and an excess amount of oil enters the annulus. The valves open from top to bottom, in a channel that is sealed in its upper part to eliminate the possibility of mechanical impurities entering them.

When the engine is running, oil is forcibly supplied by a pumping device in the form of a sleeve with a screw thread 13, mounted with a radial clearance relative to the support of the diaphragm 14, to the mechanical seal 9.

The oil, leaving the mechanical seal 9, lubricates and cools the friction pair of the seal, and enters the region 12 between the shaft 9 and the static sleeve 11. The radial clearance between the sleeve 11 and the shaft 8 ensures minimal contact of the oil with the injected fluid, accordingly, the likelihood of mechanical impurities in region 12 and the probability of failure of the seal. If there is free gas in the annulus, region 12 will be filled with gas.

In the case of gas penetrating through the diaphragm 2, they will be collected in the sealed area 24 of the compensator 5. This will eliminate the likelihood of gas gathering in the upper part of the electric motor and failure of bearings installed in the upper part of the engine due to their operation without lubrication.

A new concept of the operation of a diaphragmless compensator. Free gas is collected in the compensator, which penetrates through the diaphragm 2 in the tread 1. At the first stage of the installation, there is enough oil in the tread, and when the temperature changes, the oil squeezes free gas through the check valves 21 installed in the head 20 into the annulus. In the second stage, when the amount of oil in the tread 1 decreases, the free gas in the compensator, like a gas spring, forces the oil out of the compensator into the tread. The maximum force is equal to the opening force of the check valves 21.

Check valves 21 open in the lower direction, which reduces the likelihood of mechanical impurities entering the valve pair, which, due to their higher density, cannot move from the bottom up.

Claims (9)

1. A device for hydraulic protection of an electric motor of a submersible installation for maintaining reservoir pressure, including a compensator, an electric motor, a tread, a submersible pump, the tread comprising a shaft with an axial support and radial bearings mounted on it, as well as a head, a nipple, a compensating module with a housing, in which a nipple, a mechanical seal and a compensating element are installed, and the compensator contains a housing, a nipple and a head, characterized in that the compensator, electric motor, protector, submersible pump they are installed sequentially from top to bottom, while inside the head and nipple of the tread there is installed a protection assembly for the mechanical seal, which includes a pumping device mounted on the shaft, a labyrinth in the form of a static sleeve installed with a radial clearance relative to the shaft with the formation of a closed region that does not have a hydraulic connection with the compensating element. 2. The device according to p. 1, characterized in that the pumping device includes a sleeve with a screw thread mounted on the shaft. 3. The device according to claim 1, characterized in that the composition of the pumping device includes a labyrinth-screw pair. 4. The device according to claim 1, characterized in that the pump device includes a sleeve with a screw thread mounted on the shaft and mounted in a nipple with a radial clearance in relation to the sleeve of the diaphragm support, the diaphragm bearing being connected to the pipe of the diaphragm support assembly by means of a screw or a pin connection. 5. The device according to p. 1, characterized in that the compensating element is made in the form of a diaphragm. 6. The device according to p. 1, characterized in that the compensating element is made in the form of a piston. 7. A device for hydraulic protection of an electric motor of a submersible installation for maintaining reservoir pressure, including a compensator, an electric motor, a tread, a submersible pump, the tread comprising a shaft with an axial support and radial bearings mounted on it, as well as a head, a nipple, a compensating module with a housing, in which a nipple, a mechanical seal and a compensating element are installed, and the compensator contains a housing, a nipple and a head, characterized in that the compensator, electric motor, protector, submersible pump become sequentially from top to bottom, and a housing pin and a compensator head form a closed region for collecting free gas fluidly coupled with the engine and having no fluid communication with the annulus, wherein the compensator is configured with a check valve designed to drain the oil and gas. 8. The device according to p. 7, characterized in that the check valve is installed in the head. 9. The device according to p. 7 or 8, characterized in that the check valve is installed so that the oil and gas outlet is carried out in the lower direction.

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