RU2789218C1 - Self-cleaning downhole filter and method of washing it without extraction - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: group of inventions relates to the oil and gas industry, in particular to a self-cleaning downhole filter and a method for washing it. The device includes a filter unit, a drain unit, and connecting pipes. The filter unit contains a filter slot element, housing with intake holes and holes for the passage of reservoir fluid. The housing is located inside the filter element, an upper outer ring sealing the space between the filter element and the housing, a plug closing the housing in the lower part and made with a groove in the end part for installing the filter element, with a stop and pressure holes in its lower part, a spool valve with axial channels communicating with the inner cavity of the housing, a locking screw installed in the plug and fixing the filter slot element. The spool valve is installed in the cavity of the plug. The intake holes are located in the lower part of the housing. The spool valve is configured to move from the lower working position, in which the valve closes the intake openings, to the upper working position, in which the axial channels of the valve coincide with the intake openings, and back. The drain unit is designed in the form of a pipe with a hole, and the connecting pipes contain seals. The lower connecting pipe connects the filter and drain nodes, and the upper connecting pipe connected to the drain node is designed to be connected to an external borehole pump.

EFFECT: present invention improves the reliability of the operation of rod borehole pumps by ensuring the cleaning of the filters of the extracted liquid, at the same time the filter design is simplified, it is can be washed without removal.

2 cl, 4 dwg

Description

Technical solutions relate to the oil and gas industry, in particular, to a self-cleaning downhole filter and a method for washing it, and are designed to improve the reliability of sucker rod pumps by cleaning the filters of the produced formation fluid.

The level of technology.

It is known from the prior art, see RF patent No. 2600224, a self-cleaning downhole filter, which contains two nipples welded to adapter rings, a filter element made of wire between the restrictive rings, while the filter element includes a wire wound spirally on longitudinal elements, and all filter elements are rotatable due to the fact that a turbine is installed inside each filter element. However, the presence of a turbine complicates the design and reduces reliability. Also, the design of such a filter does not allow the possibility of washing the filter without removing it.

Also from the prior art patent of the Russian Federation No. 134576, 20.11.2013 (prototype), well filter is known. Such a filter has a body with openings for the formation fluid passage, a filtering slotted element installed outside the body, a sealing upper outer ring, a spool valve with axial channels containing pressure openings, intake openings and a plug. In this case, the plug is made with a groove in the upper part for installing the filter element, with a stop and pressure holes in its lower part, and a spool valve is mounted in the plug cavity and it is equipped with a locking screw, while the receiving holes are located in the lower part of the housing, and the sealing upper the outer ring is connected to the body by welding.

The technical problem solved by the claimed invention consists in simplifying the design, increasing reliability, and enabling the filter to be washed without removing it.

EFFECT: increased reliability of the self-cleaning downhole filter while simplifying its design, as well as providing the possibility of washing it without removing it.

The technical result is achieved by the fact that the self-cleaning downhole filter is made with the possibility of flushing without extraction and contains a filter unit, a drain unit, connecting pipes, and the filter unit contains a filter slot element, a housing with receiving holes and openings for the passage of formation fluid, while the housing is located inside slotted filter element, the upper outer ring sealing the space between the filtering slotted element and the housing, a plug covering the housing in the lower part and made with a groove in the end part for installing the filter element, with a stop and pressure holes in its lower part, a spool valve with axial channels communicating with the internal cavity of the body, while the spool valve is installed in the cavity of the plug, the lock screw is installed in the plug and fixes the filter slot element, while the inlet holes are located in the lower part of the body, and the spool valve is not with the ability to move from the lower operating position, in which the valve closes the intake openings, to the upper operating position, in which the axial channels of the valve coincide with the intake openings, and vice versa, moreover, the drain unit is made in the form of a branch pipe with a hole, and the connecting pipes contain seals, moreover, the lower connecting pipe connects the filter and drain nodes, and the upper connecting pipe connected to the drain node is made with the possibility of connection with an external downhole pump.

The essence of the claimed technical solution is illustrated by drawings Fig. 1-4, where

- in Fig. 1 shows a general view of a self-cleaning downhole filter;

- in Fig. 2 shows a general view of the filter unit;

- in Fig. 3 shows a local view of the filter unit;

- in Fig. 4 shows general views of a self-cleaning well screen in normal and flushing modes.

The figures show:

1 - filter unit;

2 - drain unit;

3 - connecting pipes;

4 - docking head;

5 - housing of the filter unit;

6 - filter slot element;

7 - sealing upper outer ring;

8 - spool valve;

9 - axial channels;

10 - pressure holes;

11 - receiving holes;

12 - plug;

13 - emphasis;

14 - locking screw.

Below is an example of the invention.

The self-cleaning filter consists of a filter assembly 1, a drain assembly 2 and connecting pipes 3. The upper connection pipe 3 contains a docking head 4 for connection with the pump, for example, by screwing, and with its other end it is connected to the drain assembly 2. The pump (not shown in Fig. ) together with a self-cleaning filter fixed at the bottom of the pump is inserted inside the tubing string (Tubing).

The connecting pipes 3 on their outer part have seals in contact with the tubing walls in the seats, and thereby sealing the space between the tubing tubing and the self-cleaning filter from formation fluid. Those. the seals are shaped and sized to effect the above-described sealing in the seats. The lower connecting pipe 3 connects the drain unit 2 and the filter unit 1.

The seat consists of subs and a pipe and is lowered into the well as part of the tubing assembly to the depth of the rod pump installation.

The lower connecting pipe also contains a seal (the lowest, Fig. 1), which is not located in the seat in the normal mode of operation of the filter and does not provide sealing of the filter.

The filter unit 1 is fastened to the connecting pipe 3 and consists of a body 5 made of a high-strength pipe with holes along the entire length for the passage of reservoir fluid, a slotted filter element 6, for example, a frame-wire welded type of wedge-shaped stainless steel wire with a tight tolerance for the size of the gap (not more than 10 microns) installed outside of the body 1, the sealing upper outer ring 7, the spool valve 8 with axial channels 9 communicating with the internal cavity of the body 5. The filter unit 1 contains pressure holes 10, intake holes 11 and a plug 12 The plug 12 is made with a groove in the upper part for installing the filter element 6, pressure holes 10 in its lower part, and a spool valve 8 is mounted in the cavity of the plug 12 and it is equipped with a locking screw 14. The plug 12 is connected to the body 5 in its lower part. The receiving holes 11 are located in the lower part of the housing 5, and the sealing upper outer ring 7 is put on the filter slot element 6 and connected to the housing 5, for example, by welding. Stop 13 is fixed in plug 12 by welding.

The filter unit 1 cleans mechanical impurities and delivers formation fluid to the pump inlet. When the sucker rod pump is switched on, the reservoir fluid sucked in by the pump plunger passes through the filter slot element 6 and through the filter holes in the housing 5 into the internal cavity of the filter assembly 1.

The ends of the filtering slotted elements 6 are sealed to ensure operability in wells with a large curvature and are centered relative to the body 5 by the upper outer ring 7 and the plug 12. Mechanical impurities larger than the size of the filter hole in the body 5 are separated from the reservoir fluid. To ensure uninterrupted operation when the filtering holes of the housing 5 are clogged, the filter assembly 1 has inlet holes 11 in the lower part of the body 5. The formation fluid supply through these inlet holes 11 is blocked by a spool valve 8 installed in the cavity of the plug 12, under the lower end, which through pressure holes 10 under well pressure is supplied with reservoir fluid, acting on it from below, while the upper end of the spool valve 8 is affected by the pressure of the fluid flowing through the filter element 6 and through the filter holes in the housing 5 into the internal cavity of the filter.

With a normal fluid pressure drop in the well cavity and in the inner cavity of the housing 5 of the filter unit, the spool valve 8 is in the lower working position and shuts off the formation fluid supply through the intake holes 11 into the internal cavity of the housing 5 of the filter unit.

When the filter holes in the body 5 become clogged, the pressure of the formation fluid entering through these holes into the internal cavity of the body 5 of the filter unit and acting on the upper end of the spool valve 8 weakens, allowing the formation fluid supplied under well pressure through the pressure holes 10 into the cavity of the plug 12 and acting on the lower end of the spool valve 8, move the spool valve 8 up to the level of coincidence of the intake holes 11 in the body 5 with the axial channels 9 in the spool valve 8 (upper operating position), through which the reservoir fluid is supplied directly into the internal cavity of the body 5 of the filter unit bypassing clogged filter holes. Changing the direction of the flow through the filter holes (not into the internal cavity of the housing, but out of it) contributes to their self-cleaning.

After entering the internal cavity of the housing, the purified reservoir fluid moves further through the connecting pipes 3 to the drain unit 2 and further to the pump inlet.

At the same time, when the spool valve 8 is in the upper working position, the degree of purification of the reservoir fluid changes significantly, which can be used as an indicator that (for example, if the degree of purification of the reservoir fluid does not change for the better for a long time) that the filter the unit is heavily clogged, the self-cleaning agents cannot cope and it needs to be flushed.

Thus, such a design of a self-cleaning downhole filter increases its reliability while simplifying its design.

Also, to increase the filtering surface of the filter, at the request of the customer, it is possible to add several to the existing filter. To do this, before lowering into the well, the spool assembly is removed from the first filter along with the plug. The next filter is screwed onto the housing with inlets (pipe) using a coupling. On the last lowest filter, the spool assembly and plug remain.

It is known that a sucker-rod pump (SRP) used to produce reservoir fluid from a well contains two valves - suction and discharge valves. The discharge valve is open when the plunger moves down (i.e., when pressure is applied to it from below), while when the plunger moves up (pressure on the discharge valve from above), the discharge valve is closed. on the discharge valve will be on top, thereby the discharge valve will be locked, blocking the flow of water down to the filter unit. In this case, water begins to flow around the valves and passes between the plunger and the walls of the tubing pipe and further between the filter and the walls of the tubing pipe, until it is stopped by the seal between the filter and the tubing pipe, and does not enter the internal cavity of the filter to flush it. This obstruction prevents prior art filters from being washed without being removed.

Inclusion in the design of the inventive self-cleaning filter of the drain node 2 makes it possible to wash it without removing it.

The drain assembly 2 is connected on both sides to the connecting pipes 3 and is a branch pipe with a technological hole. Due to the hole, the flushing liquid, for example, water flowing between the self-cleaning filter and the tubing pipe, has the opportunity to enter the internal cavity of the filter for flushing it without extraction (see Fig. 4b).

At the same time, when flushing the self-cleaning filter, the polished rod connected to the pump plunger is raised above the pump stroke, thereby raising the self-cleaning filter in the tubing pipe and displacing the seals relative to the seats. When the polished rod is lowered to its original position, the seals get back into their seats, sealing the space between the tubing tubing and the self-cleaning filter from formation fluid.

Self-cleaning filter works as follows.

In normal mode, formation fluid moves through the filter unit 1 to the pump as shown by the arrows in Fig. 4a, the spool valve 8 is in the lower operating position, and in case of clogging of the filter holes in the body 5, the spool valve 8 moves up to the level of the inlet holes 11 in the body 5 coincide with the axial channels 9 in the spool valve 8 (upper operating position), through which formation fluid is supplied directly into the internal cavity of the housing 5 of the filter unit, bypassing the clogged filter holes. In the case of slight clogging, the change in flow direction clears the filter holes in the body, the pressures acting on the lower and upper ends of the spool valve 8 are compared and the spool valve 8 moves to the lower operating position.

If it is fixed (for example, by means of the indicator described above) that the filter assembly is heavily clogged, then by raising the polished rod, the self-cleaning filter is switched to flushing mode. In this mode, as a result of lifting the polished rod, the self-cleaning filter rises relative to the tubing pipe and the seals partially exit the seats, thereby allowing the flushing fluid to flow between the tubing pipe and the self-cleaning filter and then through the hole of the drain unit 2 to enter the internal cavity of the filter unit 1 for its cleaning (Fig. 4b, arrows show the movement of the washing liquid). Thus, in the flush mode, when the stem is raised, all seals are lifted up. The top two seals come out of their seats and stop sealing. When shifted up, the lowest seal moves into the seat and begins to seal, protecting the filter assembly. After the flushing fluid supply is stopped, the polished rod is lowered to its original position, while the pump with the self-cleaning filter attached to it is also lowered to the initial position, and the seals are put back into their seats, sealing the space between the tubing tubing and the self-cleaning filter from formation fluid.

Then the method of washing the claimed filter contains the following steps.

- The rise of the polished rod is greater than the stroke of the pump;

- Supply of washing liquid;

- Lowering the polished rod to its original position.

The plunger of the SRP pump is connected to the rod string. The last rod - the wellhead rod is special and is necessary to connect the rod string with the cable suspension of the rocking chair. It has a polished surface (which is why it is also called a polished stem) and is available with a headless thread. The polished rod is connected by wedges to the rope suspension of the rocking chair. During the operation of the rocking chair, the polished rod is lowered and raised by the amount of the working stroke. By moving the wedge clamp on the polished rod, the pump rod can be lifted above its stroke.

Since the polished rod is connected to the pump plunger through the rods, and the pump in its lower part is attached with a self-cleaning filter, when the polished rod rises more than the pump stroke, the pump itself with the self-cleaning filter attached to it also rises relative to the tubing string. As a result of the lifting of the self-cleaning filter relative to the tubing pipe, the seals partially come out of the seats, thereby allowing the flushing fluid to flow between the tubing pipe and the self-cleaning filter and then through the hole of the drain unit 2 to enter the internal cavity of the filter unit 1 for its cleaning.

After lifting the polished rod, a flushing liquid, such as water, is supplied through the shut-off valves. The supply time of the washing liquid for washing the self-cleaning filter is set by the person in charge and may be, for example, one hour.

After the supply of flushing fluid is stopped, the polished rod is lowered to its original position.

Claims (5)

1. Self-cleaning downhole filter, made with the possibility of flushing without extraction and containing a filter assembly, including a filtering slotted element, a housing with receiving holes and openings for the passage of formation fluid, while the housing is located inside the filtering slotted element, the upper outer ring sealing the space between the filtering a slotted element and a body, a plug covering the body in the lower part and made with a groove in the end part for installing a filter element with a stop and pressure holes in its lower part, a spool valve with axial channels communicating with the internal cavity of the body, while the spool valve is installed in the cavity of the plug, a locking screw is installed in the plug, which fixes the filtering slotted element, while the intake holes are located in the lower part of the body, and the spool valve is movable from the lower operating position, in which the valve closes the intake holes, to the upper operating position, in which the axial channels of the valve coincide with the receiving holes, and vice versa, characterized in that it is equipped with a drain unit and connecting pipes, and the drain unit is made in the form of a pipe with a hole, and the connecting pipes contain seals, the lower the connecting branch pipe connects the filter and drain units, and the upper connecting branch pipe connected to the drain unit is made with the possibility of connection with an external sucker rod pump (SHP), while in the flushing mode when the polished rod of the SRP is raised, the upper seals are made with the possibility of partial exit from the landing places, and the lower seal is made with the possibility of its movement into the seat. 2. The method of washing the well filter according to claim 1, including: - lifting the polished pump rod to a height greater than the working stroke of the pump; - supply of washing liquid; - lowering the polished pump rod to its original position after stopping the supply of the flushing liquid, and when the polished rod, which is part of the SRP, is raised, the flushing fluid is supplied into the space between the tubing and the filter.

Images