RU2801012C1 - Method for operating well equipped with electric submersible pump under conditions complicated by formation of asphaltene-resin-paraffin deposits, and device for its implementation - Google Patents

Abstract

FIELD: oil and gas industry,

SUBSTANCE: method of operating a well equipped with an electric centrifugal pump unit 3, in conditions complicated by the formation of asphalt, resin, and paraffin deposits (ARPD), includes lowering into the well on the main tubing string 1 of an electric centrifugal pump unit 3, containing an electric motor with hydraulic protection 2, an electric centrifugal pump 3 and a cable line 4 for connecting to a control station and transformer, check 5 and drain membrane 6 valves, placing an additional tubing string 9 inside the main tubing string 1, lifting products through the annular space between the main 1 and additional 9 tubing strings, injection of ARPD solvent through the additional tubing string 9. At the same time, polyamide centralizers 11 in the form of cones with a top turned upwards, with a base diameter 2 mm less than the inner diameter of the main tubing string 1 and with slots made on the side surface of the cone, providing the passage of liquid, are first welded onto the outer surface of the additional tubing string 9. Polyamide centralizers 11 are placed at a distance of 2 m from each other. In the lower part of the additional tubing string 9, a flushing valve 12 with a spring-loaded disk plug is installed through the coupling connection; a load catcher is rigidly installed inside the flushing valve body 12.

EFFECT: increased efficiency of operation of a well equipped with an electric submersible pump in conditions complicated by the formation of asphaltene-resin-paraffin deposits of paraffin deposits, by increasing the turbulence of the fluid flow, eliminating the formation of paraffin deposits inside the additional string of tubing, increasing the efficiency of removing paraffin deposits and eliminating complications during underground well repair.

2 cl, 8 dwg

Description

The proposal relates to the oil industry and can be used in the operation of wells equipped with an electric centrifugal pump (ESP) to prevent the formation and removal of asphaltene-resin-paraffin deposits (ARPD) in the tubing string (tubing).

In connection with the ongoing measures to optimize fluid withdrawal and reduce bottomhole pressure, the problem of formation of paraffin deposits in the tubing string of the ESP has aggravated, which leads to a decrease in the well workover period and an increase in the cost of underground workover. Carrying out backwashing with solvents or aqueous solutions of surfactants often turns out to be ineffective due to insufficient circulation through the electric centrifugal pump (especially for small sizes: from ESP-30 to ESP-80), partial absorption of the flushing fluid by the formation.

A known method for preventing the deposition of asphalt-resinous and paraffin oil components in tubing in a well and a device for its implementation (patent RU No. 2661951, publ. 07/23/2018), which consists in moving paraffin crystals released from the gas-liquid mixture to the center of the flow with subsequent coagulation and washing of the wall of the tubing for removal to the surface, while the gas-liquid flow of well products moving in the cavity of the tubing, starting from the depth of the beginning of paraffin crystallization to the wellhead, is accelerated to the quadratic flow mode by switching to transportation through tubing of small diameter, forming a turbulent mode of motion in their cavity, which, due to the swirling of the flow, continuously renews the near-wall oil film, washing out paraffin crystals from the inner surface of the pipe, and into the open end of tubing of small diameter, through the annulus in a dosed manner the remover of asphalt-resinous and paraffin deposits is injected.

The disadvantages of the method are:

- formation of a stagnant zone in the annular space between the main and inner pipe strings, in which an ARPD plug is formed, which complicates the circulation of the ARPD remover;

- in case of ARPD formation inside the additional string, there is a very high risk of ARPD plug formation when the remover is pumped through the annulus, which will lead to complications when removing the equipment during the well workover;

- uneven placement of an additional small-diameter pipe inside the main string, up to the compression of the pipes due to the curvature of the wellbore, which is typical to some extent for most wells, which leads to the formation of additional stagnant zones;

- an additional inner pipe complicates the process of knocking down the knockdown (drain) valve, which will also entail complications when lifting the equipment.

The closest to the proposed method is a method of dealing with asphaltene-resin-paraffin deposits in oilfield equipment, including lowering into the well on the column of the main tubing of an electric centrifugal pump installation containing an electric motor with hydraulic protection, a centrifugal pump, a cable line for connecting to a control station and a transformer, reverse and drain valves, placement of an additional lift pipe inside the main lift pipe, lifting products through the annular space between the main and additional pipe strings, injection of an asphaltene-resin-paraffin deposit remover along the additional pipe string (patent RU No. 2779242, publ. 09/05/2022). The placement of an additional lift pipe inside the main lift pipe ensures an increase in the rate of removal of paraffin crystals released from the gas-liquid mixture due to the formation of a turbulent motion mode in the cavity of the lift pipes, which, due to the swirl of the flow, continuously renews the near-wall oil film, washing out paraffin crystals from the surface of the pipes to the maximum. Steam is used as the ARPD remover.

Closest to the proposed device is a device for implementing a method for operating a well equipped with an electric centrifugal pump installation, in conditions complicated by the formation of asphaltene-resin-paraffin deposits, containing the main string of tubing, a centrifugal pump, an electric motor with hydraulic protection, a cable line for connecting to a control station and a transformer , check and drain valves, and an additional tubing string located inside the main tubing string (patent RU No. 2779242, publ. 09/05/2022).

The disadvantage of the known method and device is low efficiency for the following reasons:

- additional pipe string is additionally a source of formation of ARFS zones (in stagnant zones behind sleeves, inside the additional string);

- uneven placement of an additional small-diameter pipe inside the main pipe string due to the curvature of the wellbore up to pressure, which leads to the formation of additional stagnant zones;

- injection of steam into the well does not sufficiently ensure uniform heat treatment to a great depth, only the upper zone of the well will warm up;

- steam will contribute to the flow of molten ARPD along the space between the lift pipes, provoking the creation of plugs from ARPD, which will lead to complications when lifting equipment during the workover of the well;

- an additional inner pipe complicates the process of knocking down the knockdown (drain) valve, which is usually located above the check valve in ESP configurations and ensures the lifting of the tubing without liquid, which will also entail complications when lifting the equipment.

The technical result of the proposal is to increase the efficiency of operation of a well equipped with an ESP in conditions complicated by the formation of paraffin deposits, by increasing the turbulence of the fluid flow, eliminating the formation of deposits inside the additional pipe string, increasing the efficiency of removing paraffin deposits and eliminating complications during underground workover of the well.

The technical result is achieved by a method of operating a well equipped with an electric centrifugal pump unit under conditions complicated by the formation of asphaltene-resin-paraffin deposits, including lowering into the well on the main tubing string of an electric centrifugal pump unit containing an electric motor with hydraulic protection, a centrifugal pump and a cable line for connection to a control station and transformer, check and drain valves, placing an additional tubing string inside the main tubing string, lifting products through the annular space between the main and additional pipe strings, pumping the asphaltene-resin-paraffin deposit remover through the additional pipe string.

What is new is that polyamide centralizers in the form of cones with the apex facing upwards, with a base diameter 2 mm smaller than the inner diameter of the main tubing string and with slots made on the side surface of the cone, providing the passage liquids, while polyamide centralizers are placed at a distance of 2 m from each other, and a flush valve with a spring-loaded disk plug is installed in the lower part of the additional pipe string through a coupling joint, a load catcher is rigidly installed inside the valve body, and a solvent for asphaltene-resin-paraffin deposits is used as a remover.

The technical result is achieved by a device for implementing a method for operating a well equipped with an electric centrifugal pump installation, under conditions complicated by the formation of asphaltene-resin-paraffin deposits, containing the main string of tubing, a centrifugal pump, an electric motor with hydraulic protection, a cable line for connecting to a control station and a transformer, reverse and drain valves; and an additional tubing string located within the main tubing string.

What is new is that on the outer surface of the additional pipe string polyamide centralizers in the form of cones with the top facing upwards, the base diameter is 2 mm smaller than the inner diameter of the main tubing string and with slots made on the side surface of the cone, providing the passage liquids, while the polyamide centralizers are placed at a distance of 2 m from each other, in the lower part of the additional pipe string, a flushing valve with a spring-loaded disk plug and a load catcher rigidly installed inside the valve body is installed through the coupling connection, and a membrane valve is installed as a drain valve.

In FIG. 1 shows a diagram of the operation of the installation.

In FIG. 2 shows a flush valve during a liquid withdrawal.

In FIG. 3 shows the washing process.

In FIG. 4 shows the flush valve during pumping of the scale remover.

In FIG. 5 shows the preparation process before lifting the equipment.

In FIG. 6 shows the flushing valve in the process of dumping cargo (scrap).

In FIG. 7 shows a centralizer placed on an additional pipe string.

In FIG. 8 shows an A-A view of the centralizer.

1 - main tubing string, 2 - electric motor with hydraulic protection, 3 - ESP, 4 - cable line, 5 - check valve, 6 - drain membrane valve, 7 - wellhead fittings, 8 - cable entry, 9 - additional internal pipe string, 10 - valve on the inner pipe string, 11 - polyamide centralizers, 12 - flushing valve, 13 - disk plug, 14 - swivel joint, 15 - spring, 16 - catcher, 17 - load, 18 - protrusion on the load, 19 - pumping unit.

A device for implementing a method for operating a well equipped with an electric centrifugal pump installation, under conditions complicated by the formation of asphaltene-resin-paraffin deposits, contains the main string of tubing 1 (Fig. 1, 3, 5), a centrifugal pump 3, an electric motor 2 with hydraulic protection, a cable line 4 for connection to the control station and transformer, check 5 and drain 6 valves, and an additional string of tubing 9 (Fig. 1, 3, 5, 7) located inside the main string of tubing 1. The cable line 4 is led to control station and transformer through the cable gland 8 (Fig. 1, 3, 5) installed on the wellhead 7.

The additional pipe string 9 may consist of individual pipes (sections) of small diameter tubing connected to each other by threads. Polyamide centralizers 11 (Figs. 1, 3, 5, 7) in the form of cones with the top facing upwards are installed on the outer surface of the additional pipe string 9 by fusing, ensuring the alignment of the additional pipe string and additional turbulence of the well production flow. The diameter of the base of the cone is 2 mm less than the inner diameter of the main string of tubing 1. On the side surface of the cone of the centralizer 11, vertical slots 5 mm wide are made, which ensure the passage of liquid. Through-hole dimensions are calculated depending on the performance of the ESP, the slot width of 5 mm is recommended for units with standard sizes up to ESP-80. For installations of higher productivity, starting with ESP-100, in order to exclude the creation of excessive back pressure, it is recommended to increase the width of the slots, but not more than 10 mm. Polyamide centralizers 11 are placed on each tubing of an additional pipe string 9 in the amount of at least 6 pieces at a distance of 2 m from each other.

In the lower part of the additional pipe string 9, a flushing valve 12 (Figs. 1-6) is installed through a coupling connection in the form of a hollow cylindrical pipe with a disk plug 13 (Figs. 2, 4, 6), pivotally 14 connected to the flush valve body. The disk plug 13 is rigidly connected with the spring 15 to the inner surface of the body of the flush valve 12, excluding the ingress of produced products into the additional pipe string 9. The spring 15 of the flush valve is selected so that the disk plug 13 opens when an excess pressure of 0.2 MPa is created inside the additional pipe string , which allows washing with ARPD solvent.

Inside the valve body 12, a catcher 16 (Fig. 2, 4, 6) of the load 17 (scrap) (Fig. 6) is made, which is a metal ring with internal chamfers and a height of 5 cm, installed inside the valve body by welding.

As a drain valve 6, a membrane valve is used, when pressure is created inside the main pipe string 1 more than 5 MPa, the membrane breaks, which allows killing the well and lifting the main pipe string 1 with ESP without liquid.

To prevent the lifting of an additional pipe string 9 with liquid during repairs, before lifting the downhole pumping equipment (DPU), a load 17 is dropped into the additional pipe string in the form of scrap with four protrusions 18 (Fig. 6) rigidly welded on the side surface of the load, due to which scrap is caught in the catcher 16 and simultaneously opens the plug 13 of the flushing valve 12, ensuring that the liquid is drained when the additional pipe string 9 is lifted.

The proposed method is carried out in the following sequence.

1) An electric centrifugal pump installation is lowered into the well to a depth that ensures maximum production when the design bottomhole pressure is reached, on the main tubing string, containing an electric motor with hydraulic protection, a centrifugal pump and a cable line connected to the control station and transformer (in the figures not shown), check and drain valves, an additional tubing string inside the main tubing string.

An additional internal pipe string is suspended through the wellhead fitting 7 and has a valve 10 in the upper part (Fig. 1, 3, 5) for connecting the pump unit 19 (Fig. 3) when flushing with the ARPD solvent.

The length of the additional pipe string is selected in such a way that the flushing valve is located at a depth of 5 meters above the location of the drain valve, which ensures the exclusion of a stagnant zone and shock loads on the drain valve membrane when flushing with ARPD solvent.

On the outer surface of the additional pipe string, polyamide centralizers in the form of cones with the top facing upwards, the base diameter 2 mm less than the inner diameter of the main tubing string, and side slots for the passage of fluid are preliminarily welded. Polyamide centralizers are placed equidistant from each other at a distance of 2 m. This shape and placement allow for maximum turbulence of the fluid flow and at the same time eliminate complications when lifting an additional pipe string even in the presence of deposits inside the main pipe string. A flushing valve with a spring-loaded disk plug is installed in the lower part of the additional pipe string through a coupling joint, and a load catcher is rigidly installed inside the valve body.

2) Launch the ESP. When the ESP is put into operation, the produced liquid rises through the space between the inner surface of the main pipe string and the outer surface of the additional pipe string, when passing through the side slots of the centralizers, due to a decrease in the flow area and pressure drop, additional turbulence of the liquid flow occurs, which makes it possible to wash off the ARPD particles from the inner surface of the main pipe string and the outer surface of the additional pipe string, excluding their accumulation on the pipe surface.

3) When ARPD deposits accumulate on the inner surface of the main pipe string and the outer surface of the additional pipe string, indirectly determined by a decrease in the measured fluid flow rate, the pumping unit is connected to the additional pipe string through a valve and the ARPD solvent is pumped, followed by lifting through the space between the main and additional pipe strings and dissolution of ARPD. The spring of the flushing valve is selected in such a way that the disk plug opens when an excess pressure of 0.2 MPa is created inside the additional pipe string, which allows flushing with the ARPD solvent.

As a solvent, a reagent can be used that maximally dissolves all the components of ASPO, in particular asphaltenes and resins, for example, Efril-317D (TU 2458-317-74033742-2008).

4) If it is necessary to carry out underground repairs to prevent the lifting of an additional pipe string with liquid during repairs, before lifting inside the additional pipe string, a load is dropped in the form of scrap with four metal protrusions fixed on the side surface by welding, located at a distance of, for example, 0.5 meters from the bottom of the load, which ensures the simultaneous opening of the plug of the flushing valve to drain the liquid when raising an additional pipe string when scraping.

A membrane valve is used as a drain valve, when pressure inside the main pipe string exceeds 5 MPa, the membrane breaks, which makes it possible to kill the well and lift the main pipe string with ESP without liquid.

The proposed method and device, when used on the most complex category of wells equipped with ESPs, where the previously used methods of dealing with ARPD were not effective enough, especially for small sizes: from ESP-30 to ESP-80, provides an increase in the overhaul period of wells.

The proposals provide an increase in the efficiency of operation of a well equipped with an ESP in conditions complicated by the formation of paraffin deposits, by increasing the turbulence of the fluid flow, eliminating the formation of deposits inside the additional pipe string, increasing the efficiency of removing paraffin deposits and eliminating complications during underground workover of the well.

Claims (2)

1. A method for operating a well equipped with an electric centrifugal pump unit in conditions complicated by the formation of asphaltene-resin-paraffin deposits, including lowering into the well on the main tubing string of an electric centrifugal pump unit containing an electric motor with hydraulic protection, a centrifugal pump and a cable line for connecting to a control station and transformer, check and drain valves, placing an additional tubing string inside the main tubing string, lifting products through the annular space between the main and additional pipe strings, pumping the asphaltene-resin-paraffin deposit remover along the additional pipe string, characterized in that it is preliminarily on the outer the surface of the additional pipe string is fused with polyamide centralizers in the form of cones with the top facing upwards, the base diameter is 2 mm less than the inner diameter of the main tubing string and with slots made on the side surface of the cone, ensuring the passage of liquid, while the polyamide centralizers are placed on at a distance of 2 m from each other, and a flush valve with a spring-loaded disk plug is installed in the lower part of the additional pipe string through a coupling joint, a load catcher is rigidly installed inside the valve body, and a solvent for asphaltene-resin-paraffin deposits is used as a remover. 2. A device for implementing a method for operating a well equipped with an electric centrifugal pump installation, in conditions complicated by the formation of asphaltene-resin-paraffin deposits, containing the main string of tubing, a centrifugal pump, an electric motor with hydraulic protection, a cable line for connecting to a control station and a transformer, return and drain valves, and an additional tubing string located inside the main tubing string, characterized in that on the outer surface of the additional tubing string polyamide centralizers in the form of cones with the apex facing upwards are installed by welding, the base diameter is 2 mm less than the inner diameter of the main tubing string and with slots made on the side surface of the cone, ensuring the passage of fluid, while the polyamide centralizers are placed at a distance of 2 m from each other, in the lower part of the additional tubing string, a flushing valve with a spring-loaded disk plug is installed through the coupling connection and a load catcher rigidly installed inside the valve body, and a membrane valve is installed as a drain valve.