RU2846137C1 - Sucker-rod pump unit - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: invention relates to oil and gas industry, in particular to downhole sucker-rod pump units, and can be used for pumping from production well fluid with high gas factor containing mechanical impurities. Installation includes a tubing string, a pump consisting of a cylinder with a suction valve at the inlet, a plunger with a pressure valve at the outlet and plugged from below a hollow cylindrical casing mounted with a gap relative to the cylinder and fixedly and hermetically connected by its upper part to the cylinder, bars connecting the plunger to the ground drive, internal tube connecting the pump inlet with a casing equipped with side filter holes, which are covered from the outside with a gap by a cup-shaped semi-casing, below which centralisers are located on the casing, filter. Inner tube is equipped with well fluid fine filter. Open part of bowl-shaped semi-casing faces the well head. Filter is installed between the semi-casing and the casing above its side filtration holes, is made in the form of multi-row brushes covering the space between the cup-shaped semi-casing and the casing, fixed on the cup-shaped semi-casing and interacting with the casing. Centralisers are made in the form of external metal brushes installed uniformly along the perimeter above the formation with possibility of covering the space between the casing and well walls. Outside the fine filter there is a cup installed with a gap and facing the well bottom by its open part.

EFFECT: increasing the time between maintenance and repairs of the pumping unit for pump repair and cleaning due to fine cleaning of the liquid at the pump inlet, preliminary separation of large particles of mechanical impurities and self-cleaning of the filter.

1 cl, 1 dwg

Description

The invention relates to the oil and gas production industry, in particular to downhole sucker rod pumping units, and can be used to pump liquid with a high gas factor containing mechanical impurities from a production well.

A sucker rod pumping unit is known (patent for PM RU No. 45790, IPC F04B 47/02, published 27.05.2005 Bulletin No. 15), containing columns of sucker rods and pump pipes, a container for mechanical impurities, a casing connected to the column of pump pipes by means of a separator, perforated with holes, in which a cylinder of a sucker rod pump with a suction valve, hydraulically connected to the cavity of the casing, and a plunger with a discharge valve is placed with a gap, wherein the holes in the casing are made tangentially.

The main disadvantage of this unit is the lack of preliminary separation of large particles before collection and the lack of fine cleaning of the liquid at the pump inlet, which leads to the capture of small mechanical particles by the liquid when sucked into the pump, intensively destroying the plunger pair of the pump, and rapid filling of the container with mechanical impurities. All this leads to frequent extraction of the unit with the container due to the reduction in the time between servicing the container for cleaning and the inter-repair period of the pump.

Also known is a borehole sucker rod pump (RU patent No. 2360145, IPC F04B 47/00, published 27.06.2009 Bulletin No. 18), comprising a plunger-cylinder working pair with a discharge and suction valve installed therein, respectively, a mechanical impurity filter connected to the pump intake and provided at the bottom with a container for preliminary accumulation of mechanical impurities, wherein the mechanical impurity filter consists of concentrically arranged pipes, the upper part of the outer pipe and the lower part of the inner pipe hydraulically communicate the well bottom with the pump intake, and the container for preliminary accumulation of mechanical impurities is made in the form of a continuation of the filter's outer pipe and is provided with a spring-loaded valve installed in the lower part of the container, wherein the distance from the pump to the spring-loaded valve is greater than the distance from the pump to the perforation interval.

The main disadvantage of this installation is the lack of preliminary separation of large particles before collection and the lack of fine cleaning of the liquid at the pump inlet, which leads to the capture of small mechanical particles by the liquid when sucked into the pump, intensively destroying the plunger pair of the pump. All this leads to frequent removal of the pump due to a decrease in the inter-repair period of the pump.

The closest is a sucker-rod borehole pumping unit for oil production from wells with a sump under high gas factor conditions (RU patent No. 2360145, IPC F04B 47/00, published on 27.06.2009, Bulletin No. 18), which includes a column of oil well tubing (TUB), a column of sucker rods, a sucker-rod pump consisting of a cylinder with a suction valve, a plunger with a discharge valve, the cylinder is equipped with a plugged hollow cylindrical casing, fixedly fixed in the upper part with the cylinder, two gas bypass valves are made in the upper part of the casing, and the intake of the sucker-rod pump is equipped with an internal pipe with an open lower part, while the open lower part of the pipe is located at a distance of at least 3 m below the bottom of the perforated formation, the casing is made with filtration holes covered a cup-shaped semi-casing facing the bottom of the well with its open part, and below the cup-shaped semi-casing the casing is equipped with centralizers, wherein the filtration holes are located at a distance of not less than 1.5 m below the bottom of the perforated formation, below the level of the filtration holes on the inner pipe, upper and lower conical metal meshes are installed, wherein the upper mesh has a cell of 2 mm, the lower one has a cell of 1 mm, each gas bypass valve is connected to a polymer capillary tube fixed on the tubing string using metal clamps, wherein the length of the polymer capillary tubes is selected in such a way that the top of the tubes is 200 m above the dynamic level during operation of the unit.

The main disadvantage of this unit is the lack of preliminary separation of large particles before collection, the lack of fine cleaning of the liquid at the pump inlet and self-cleaning of the mesh during operation, which leads to the capture of small mechanical particles by the liquid when sucked into the pump, intensively destroying the plunger pair of the pump, and to the rapid clogging of the conical metal meshes, which play the role of a filter, in the casing. All this leads to frequent removal of the unit with the casing and meshes due to the reduction in time between maintenance (cleaning) of the casing with meshes for cleaning.

The technical result is the creation of a borehole sucker rod pumping unit that allows increasing the time between pumping unit maintenance for pump repair and cleaning due to fine cleaning of liquid at the pump inlet, preliminary separation of large particles of mechanical impurities and self-cleaning of filters.

The technical solution is a borehole sucker-rod pumping unit, including a lifting column lowered into the borehole to lift borehole fluid from the exposed productive formation, a pump consisting of a cylinder with a suction valve at the inlet, a plunger with a discharge valve at the outlet and a hollow cylindrical casing plugged at the bottom, installed with a gap relative to the cylinder and fixedly and hermetically connected with its upper part to the cylinder, rods connecting the plunger with a surface drive, an internal tube communicating the pump inlet with the casing equipped with side filter holes, which are blocked from the outside with a gap by a cup-shaped semi-casing, below which centralizers are located on the casing, and a filter installed in front of the inlet to the casing and designed with the possibility of cleaning the borehole fluid from mechanical impurities.

What is new is that the inner tube is equipped with a fine filter for cleaning the well fluid, the cup-shaped semi-casing faces the wellhead with its open part, the filter is installed between the semi-casing and the casing above its side filter holes, made in the form of multi-row brushes that cover the space between the cup-shaped semi-casing and the casing, fixed on the cup-shaped semi-casing and interacting with the casing, the centralizers are made in the form of large external metal brushes installed evenly along the perimeter above the formation with the possibility of covering the space between the casing and the walls of the well, while a glass is located with a gap outside the fine filter, facing the open part to the bottom of the well.

The drawing shows a diagram of a borehole sucker rod pumping unit in longitudinal section, placed in a borehole.

A borehole sucker-rod pumping unit includes a lifting column 3 lowered into a borehole 1 for lifting borehole fluid from an exposed productive formation 2, a pump consisting of a cylinder 4 with a suction valve 5 at the inlet, a plunger 6 with a discharge valve 7 at the outlet and a hollow cylindrical casing 8 plugged at the bottom, installed with a gap relative to the cylinder 4 and fixedly and hermetically connected (for example, by a connection 9 in the form of a threaded, lock or similar connection) with its upper part to the cylinder 4, rods 10 connecting the plunger 6 with a surface drive (for example, a pumping unit, a chain drive, a hydraulic drive or the like - not shown), an internal tube 11 communicating the inlet of the cylinder 4 with the casing 8 equipped with side filter holes 12, which are blocked from the outside with a gap cup-shaped semi-casing 13, below which on the casing there are centralizers in the form of large external metal brushes 14 (with a bristle length equal to the distance from the casing 8 to the walls of the well 1), and a filter made in the form of multi-row brushes 15, fixed on the cup-shaped semi-casing 13 and interacting with the casing 8, blocking the space between them. The multi-row brushes 15 of the filter are installed before the well fluid enters through the openings 12 into the casing 8 and are designed with the possibility of cleaning the well fluid from mechanical impurities. In this case, the inner tube 11 is equipped with a fine filter 16 for cleaning the well fluid (for example, a slot filter, a wire filter, etc.), and the cup-shaped half-casing 13 faces the open part towards the mouth of the well 1. Multi-row brushes 15 of the filter are installed between the cup-shaped half-casing 13 and the casing 8 above its side filter openings 12. Large metal brushes 14 of the centralizer are installed evenly along the perimeter above the productive formation 2 with the possibility of covering the space between the casing 8 and the walls of the well 1. Outside the fine filter 16, a cup 17 is located with a gap, facing the open part towards the bottom of the well 1.

Structural elements, process connections, seals, etc. that do not affect the explanation of the operation of the borehole sucker rod pumping unit are not shown in the drawing or are shown conditionally.

The borehole sucker rod pumping unit operates as follows.

On the casing 8, during manufacture, a cup-shaped half-casing 13 is installed on the outside with a gap and fixed (by thread, welding, glue, etc.) so that it faces upward with its open part and covers the filter openings 12 of the casing 8, and the multi-row brushes 15 of the filter are located above the filter openings. Below the cup-shaped half-casing 13, large metal brushes 14 are rigidly fixed (by welding, glue, etc.) on the outside of the casing to ensure the centering of the casing 8 in the well 1. The cylinder 4 of the pump with the suction valve 5 is equipped from below with an internal tube 11 with a fine filter 16 and a glass 17 facing downwards.

Before lowering into well 1, cylinder 4 of the pump with suction valve 5, inner tube 11, fine filter 16 and cup 17 is inserted into casing 8 with a gap and fixed relative to each other by upper parts using connection 9. This structure assembled on elevator column 3 is lowered into the well into the installation interval so that large metal brushes 14 are located above productive formation 2. During lowering, large metal brushes 14 interact with the walls of well 1, excluding impact of casing 8 against these walls, i.e. large metal brushes 14 play the role of centralizers. After lowering, the elevator column 3 is fixed at the wellhead 1. After which, the plunger 6 with the discharge valve 7 is lowered into the elevator column 3 on the rods 10 to the entrance to the cylinder 4, which is determined by reducing the weight of the rods 10 at the wellhead, for example, using a wellhead weight indicator (WWI - not shown). The wellhead 1 is sealed (for example, with a wellhead sealer, preventer, etc. - not shown), and the rods 10 are connected to the surface drive.

When switched on, the ground drive transmits reciprocating movements to the rods 10 with the plunger 6.

When the plunger 6 moves upward, a vacuum is created inside the cylinder 4, under the action of which the discharge valve 7 closes, the liquid above the plunger 6 rises along the lifting column 3 to the wellhead, and the suction valve 5 opens, the well fluid is sucked inside the cylinder 4 under the action of the pressure difference of the productive formation 2 and the vacuum inside the cylinder 4. In this case, the well fluid passes through large metal brushes 14, in which large fractions of mechanical impurities are retained, rises outside the casing 8 to the cup-shaped semi-casing 13, which additionally deposits fractions of mechanical impurities on the large metal brushes 14, the sedimentation rate of which is higher than the flow rate of the well fluid between the casing 8 and the walls of the well. Then the well fluid passes between the cup-shaped half-casing 13 and the walls of the well 1 through a reduced gap, in which the flow rate of the well fluid increases and (according to Bernoulli's law) the static pressure decreases, which promotes the intensive release of gas rising along the annulus of the lifting column 3 in the well 1 due to the lower density relative to the well fluid. After which the well fluid, freed from large fractions of mechanical impurities, enters the cup-shaped semi-casing 13 from the wellhead 1, passes through the multi-row brushes 15 of the filter, being cleaned of fractions of mechanical impurities larger than the gap between the bristles of the multi-row brush 15, and enters through the filter holes 12 into the casing 8, in which it descends toward the bottom of the well 1 to the cup 17, where it abruptly changes the direction of flow to the opposite (toward the wellhead), while more inertial mechanical impurities descend to the bottom of the casing 8, and most of the remaining smallest fractions of mechanical impurities are retained by the fine filter 16 and enter the inner tube 11 and then through the suction valve 5 into the cylinder 4. The fractions of mechanical impurities that do not pass through the filter holes 12 are deposited on the bottom of the cup-shaped semi-casing 13.

When plunger 6 moves downwards, excess pressure is created in cylinder 4, closing suction valve 5 and opening discharge valve 7, as a result of which well fluid from cylinder 4 flows through the open discharge valve 7 due to the decreasing volume under plunger 6 into the lifting column 3 to rise along them towards the wellhead when plunger 6 moves upwards.

Then the cycles of reciprocating movement of plunger 6 with the help of rods 10 are repeated, and the well fluid rises to the surface.

When mechanical fractions are retained by the bristles of the large metal brush 14 and the multi-row brush 15, they collide with each other and stick together, increasing in size, which increases their weight and ability to settle.

In this case, the bristles of the large metal brush 14 and the multi-row brush 15 are cleaned independently without additional operations (self-cleaning) when the plunger 5 moves in the cylinder 4 of the pump.

When the plunger 6 moves upward, a vacuum is created in the cylinder 4, which also tends to lift the cylinder 4, held by the elevator column 3, which leads to compression of the elevator column 3 within the limits of elastic deformation (approximately by 10-12 cm with a length of 1000 m) and, as a consequence, to pulling the metal brush 14 upward by the same distance. When the plunger 6 moves downward, the elevator column 3 returns to its original position due to elastic forces. In this case, the bristles of the large metal brush 14, interacting with the walls of the well 1, change their position and the distance between the bristles, which leads to a gradual downward movement of the coarse fractions along the metal brush 14 and then settles under their own weight on the bottom of the well 1, cleaning this brush 14.

When the plunger 6 moves upward in the cylinder 4, a flow of well fluid is created in the space between the cup-shaped half-casing 13 and the casing 8, which leads to the deflection of the bristles of the multi-row brush 15 downward, and when the plunger 6 moves upward, they return to their original position due to elastic forces, changing the position and distance between the bristles, which leads to the gradual lowering of the coarser fractions along the multi-row brush 15 and then settling under their own weight on the bottom of the cup-shaped half-casing 13, while cleaning this multi-row brush 15.

As practice has shown, such a borehole sucker rod pumping unit retains at least 98% of large fractions of mechanical impurities, which is at least 3 times higher than that of analogues, where it is no more than 94%, due to the self-cleaning of the metal brush 14 and the multi-row brush 15, the period between filter cleanings has increased at least 2 times, and the overhaul period of the pump, consisting of a cylinder 4 and a plunger 6, has increased 4 times due to less wear during operation.

The proposed borehole sucker rod pumping unit allows to increase the time between maintenance and repair of the pumping unit for pump repair and cleaning due to fine cleaning of liquid at the pump inlet, preliminary separation of large particles of mechanical impurities and self-cleaning of filters.

Claims (1)

A downhole sucker rod pumping unit comprising a lifting column lowered into a well for lifting well fluid from an exposed productive formation, a pump consisting of a cylinder with a suction valve at the inlet, a plunger with a discharge valve at the outlet and a hollow cylindrical casing sealed at the bottom, installed with a gap relative to the cylinder and fixedly and hermetically connected by its upper part to the cylinder, rods connecting the plunger to a surface drive, an internal tube communicating the pump inlet with the casing equipped with side filter holes, which are blocked on the outside with a gap by a cup-shaped semi-casing, below which centralizers are located on the casing, and a filter installed in front of the inlet to the casing and designed with the possibility of cleaning the well fluid from mechanical impurities, characterized in that the internal tube is equipped with a fine filter for cleaning the well fluid, the cup-shaped semi-casing faces the wellhead with its open part, the filter is installed between a semi-casing and a casing above its side filter holes, made in the form of multi-row brushes covering the space between the cup-shaped semi-casing and the casing, fixed on the cup-shaped semi-casing and interacting with the casing, the centralizers are made in the form of external metal brushes installed evenly along the perimeter above the formation with the possibility of covering the space between the casing and the walls of the well, while a glass is located with a gap outside the fine filter, facing the open part to the bottom of the well.