RU2661951C1 - Method for preventing deposits of asphalt-resins and paraffin components of oil in pump compressor tubes in the well and device for its implementation - Google Patents

Abstract

FIELD: oil industry.

SUBSTANCE: group of inventions refers to the oil industry and can be used in the production of oil with a high content of asphalt-resins and paraffin components of oil (heavy oil deposits). With a fountain production method or with the help of electric centrifugal pump (ESP) units, the gas-liquid flow (GVF) of the well production, moving in the tubing cavity starting from the depth of the beginning of the crystallization of paraffin to the mouth, are accelerated to the quadratic flow regime by switching to transportation along a coaxially placed additional "small diameter" tubing suspension (floppy disk drive). At the same time, from the laminar nature of the movement along the tubing in the cavity of the additional suspension of small diameter (floppy disk drive), GZHP transforms into a turbulent motion regime (quadratic flow regime). Stream turbulence continuously updates the wall oil film together with paraffin crystals and excludes their accumulation, and on the annular space of working tubing and tubing of small diameter, through the outlets of wellhead reinforcement by ground pumps (selectively), the ASPO removers are delivered.

EFFECT: reliability of the work of mechanized wells equipped with ESP in conditions of deposition of heavy oil deposits in the tubing cavity is increased.

2 cl, 2 dwg

Description

The proposed technical solutions are united by a single inventive concept and relate to the oil industry, namely, the oil production field to prevent the deposition of asphalt-resinous and paraffin oil components (AFS) on the inner surface of tubing (tubing) during fountain and mechanized methods of operating oil wells. Known methods for preventing deposits of paraffin in an oil well, protected by patents RU 2432322 (10.27.11) Bull. thirty; RU 2429344 (09/20/2011), as well as numerous methods and devices are described in the technical literature [1-6]. Each of the above methods for preventing and removing paraffin deposits on the inner surface of the tubing is aimed either at creating a protective film in the boundary layer of the reservoir fluid flow using paraffin inhibitors, or using paraffin scavengers [5], including through the use of heat treatment of wells [6] or removal of paraffin scraper scrapers [7]. As a prototype used patent RU 2263765 (10.11.2005) Bull. No. 31, in which, when operating a well equipped with an electric submersible pump (ESP) with ground and underground well equipment, ultrasonic standing waves excited by a resonator placed above a submersible electric pump are used to coagulate and flush paraffin crystals from the tubing wall.

The disadvantages of the known methods are associated, for example, with the need to heat the transported liquid above the temperature of the beginning of crystallization of paraffin (40 ° C ... 70 ° C) by heaters [6] or are aimed at using the technology of cleaning the inner cavity of tubing with mechanical scrapers [7]. Technical solutions have been implemented for applying special coatings to the inner surface of tubing (vitrification, applying fluoroplastic films), etc. [4]. Each of the known methods for the prevention and elimination of paraffin, including the patent RU 2263765, as a rule, is not universal and is applicable only in specific mining and geological conditions of an oil field, oil component composition and its temperature component. The most frequent shutdowns of production wells caused by sedimentation deposits on the inner surface of tubing are found in wells with small (up to 18 ... 20 m ³ / day) and average flow rates (up to 60 m ³ / day). In well production coming from a productive formation with low flow rates, the thermal energy of the oil and gas stream is intensively dissipated into the surrounding area when it comes in contact with cooled rocks at shallow depths (0 ... 500 m), where their temperature is much lower than the crystallization temperature of paraffin - the main component of oil paraffin. These conditions contribute to the precipitation of paraffin crystals in the oil stream and their deposition on the walls of the tubing. Ultrasonic vibrations excited during the operation of the ESP (according to the patent RU 2263765) are also scattered when the pipes are in close contact with the walls of the production string in directional wells and cannot create an effective effect on the solution of the problem of preventing deposition of paraffin deposits in tubing. As a result, the method proposed 12 years ago to prevent the deposition of paraffin in an oil well with the generation of ESP ultrasound has no commercial use.

The technical result is to increase the reliability of mechanized wells equipped with ESPs in the conditions of deposition of paraffin in the cavity of the tubing.

The purpose of the invention is to increase the effectiveness of the prevention of deposits of paraffin deposits in the tubing cavity and ensuring the smooth operation of the well.

This goal is achieved by the fact that with the fountain method of production or with the help of ESP, lowered to the calculated depth into the well at the working tubing, a gas-liquid flow (GLC) of the production of the well moving in the tubing cavity, starting from the depth of onset of paraffin crystallization (for example, from a depth of 900 m) to the mouth, accelerate to the quadratic flow mode by switching to transportation of the entire GLC through coaxially placed additional “small diameter” tubing suspension (tubing) fixed in the wellhead reinforcement with the possibility of communication with ground oil gathering system. In this case, the GLC from the laminar motion along the tubing from the ESP in the cavity of the additional suspension (tubing) of small diameter goes into a turbulent mode (quadratic flow mode). At the same time, intensive turbulization (swirling) of the flow continuously updates the wall oil film together with paraffin crystals and eliminates their accumulation, and through the annular space between the tubing and tubing of small diameter through the outlets of the wellhead fittings with ground pumps (selectively) a working agent is used - a remover of asphalt-resinous and paraffin deposits.

The quadratic regime of fluid motion in pipes arises at “high” speeds [8] (P. 23), when the Reynolds number (Re)

where: ε is the relative roughness of the pipes; ε = Δ / d, Δ is the absolute roughness; d is the inner diameter of the pipe. If we take the absolute roughness Δ = 0.3 mm for the tubing, the relative roughness of the tubing will be in the range ε = (0.00852 ... 0.0145).

The number Re, according to formula (1) for the onset of the quadratic regime of gas-liquid flow in small tubing according to GOST 633-80 [9] (27 × 3; 33 × 3.5; 42 × 3.5), is defined as:

Re for tubing 27 × 3 - 34500;

Re for tubing 33 × 3.5 - 44000;

Re for tubing 42 × 3.5 - 58660.

The hydraulic resistance coefficient λ for the quadratic flow regime according to the Shifrinson formula [10] (P. 75) is expressed by the formula:

Then for NKtmd λ will be:

λ for tubing 27 × 3 - 0.0382;

λ for tubing 33 × 3.5 - 0.0334;

λ for tubing 42 × 3.5 - 0.0323.

The pressure drop (Rtr) in the cavity of a small diameter tubing for a single-phase fluid flow can be determined by the Darcy-Weisbach formula [11] (P. 130):

where H is the length (NKtmd) of small diameter, m;

s - linear fluid velocity in the tubing - m / s

ρ is the density of the liquid, kg / m ³ ;

d is the inner diameter of the pipe, m

Taking (for example) the values included in the calculation formula (3), we determine the pressure loss in the area (H) of the additional column H = 800 m; (NKtmd 27 × 3) d = 0,0207 m; s - 1.5 m / s; ρ = 850 kg / m ³ ; λ - 0.0382.

Ptr = 0.0382 * 800 * 1.5 ² * 850 / (2 * 0.0207 * 10 ⁶ ) = 1.41 MPa.

The calculation shows that the Rtr value for the tubing of small diameter (for ESPs of modern production) does not exceed 5 ... 7% of the design head of the ESPs, and cannot serve as a limiting factor from the application of the method for preventing deposition of paraffin deposits in the regime of quadratic oil movement in a paraffin-hazardous section wellbore.

The invention is illustrated in the drawing, where in FIG. 1 shows a General view of the well in section; in FIG. 2 shows a cross section of a well for visualizing pipe columns lowered into the well.

A method of preventing deposits of paraffin deposits in the tubing string can be implemented on the well, including downhole and ground equipment. Downhole equipment includes a production casing 1, into which oil with a flow rate Qn flows from the reservoir 2 through perforations (not shown in Fig. 1). In the inner cavity of the production casing 1 there is an ESP assembly, including a submersible electric motor (PEM) 3, a centrifugal pump (ESP) 4, a check valve 5 and a drain valve 6. Above the ESP there are working tubing pipes 7. To feed the electric motor with electric energy, use an armored cable 8, which is fixed on the outer surface of the tubing 7, with the upper end of the cable 26 reaching the surface through the faceplate 11. A column head 9 is installed in the upper part of the production casing. on which all wellhead equipment is mounted: crosspiece 10, faceplate 11, tee fittings 12, additional tee fittings 13, adapter flange 14, central shutter 15, tee fittings 16, shutter 17, w the choke chamber 18, the manifold 19, which is connected to the ground flow line 20. In the cavity of the working tubing 7, an additional pipe string 21 is arranged coaxially with them, equipped with a funnel 22 from the bottom to the depth (L sp tubing md). To control the operation of the well, wellhead equipment includes: a gate valve 25 with a branch, which is cut into the manifold 19; an annular valve 27 with a non-return valve 28 with a tap that is cut into the manifold 19. A sampling valve 29 is installed on the manifold 19. To the tee fitting 13 are connected: a valve 30, a tee 31, a valve 32, a process pipe 33 and a pressure gauge 34. To the crosspiece 10 in series connected - a valve 35 with a technological pipe 36. Pressure gauges 37 and 34 are connected to the tees 16 and 31, respectively.

The task to prevent deposition of paraffin deposits in the tubing cavity during oil production by a fountain or mechanized method is solved in the following sequence and using the following devices. In the wellbore, cased with production casing 1, on the tubing 7 lower the ESP to the calculated depth (NSP ESP). With the fountain method of operation, the suspension of tubing of the ESP is not completed. The ESP (from bottom to top) includes a thermomanometric sensor 39 for transmitting via cable 8 encoded signals about the ambient temperature in the zone of operation of the SEM, the pressure at the intake of the gas separator 23 and the vibration parameter of the ESP 4 during its operation in the well. Submersible electric motor (PED) 3 through the Central shaft transmits torque to the ESP shaft, in which the impellers are located (not shown in Fig. 1). The flow of the gas-liquid mixture Qн coming from the productive formation 2 is fed to the gas separator 23, in which the associated gas is partially separated from the liquid phase (not shown in Fig. 1), and then the liquid phase is sent to the ESP cavity to increase the pressure. In the layout of the ESP, check valves 5 and drain 6 are provided. Valve 5 is designed to prevent the discharge of fluid from the tubing during ESP stops, and valve 6 is used to create a circulation of the jamming solution and draining the fluid from the tubing when lifting the ESP.

After completion of the descent ESP into the well on tubing 7 to the cable 8 (the working suspension) and fixing the CNT via threads with the flange 11, wellhead into the cavity of the working tubing 8 to the depth (H _cn tubing ppm), which revealed the beginning wax crystallization, into the working the tubing suspension 7 is lowered an additional string of tubing 21 of small diameter. An additional tubing string of small diameter 21, with a funnel 22 at the end, can be composed of separate tubing (sections) of tubing connected by a thread, or on the basis of a flexible tubing (CT). An additional string of small diameter tubing is suspended (fixed) in the wellhead using an adapter flange 14 mounted between the tee 13 and the central gate valve 15. As a result of this arrangement of the wellhead equipment, a channel is created for the movement of the GWP along the small diameter tubing through the gate 15, the tee 16, gate valve 17, choke chamber 18, manifold 19 in the flow line of the oil gathering 20.

After preparatory work is carried out in accordance with the generally accepted technology in the oil industry for testing wellhead, electrical, and auxiliary equipment that is a part of a well, determining a static level in a well, and obtaining a positive conclusion about the well’s readiness for operation, a voltage is supplied to the SEM through a cable outlet 26.

Previously, before applying electrical voltage to the SEM on the wellhead valves, open the valves 15, 17, 25, 27, 30, and the valves 32, 35 close. At the first stage of bringing the well to a stationary mode of operation, kill fluid is withdrawn (pumped out) from the ESP well. In this case, all the fluid coming from the ESP is simultaneously directed along the working tubing 7 and tubing of small diameter 21. The composition of the product coming from the well during its operation is determined by periodic sampling through the valve 29 from the manifold 19.

After the appearance of oil in the products pumped out of the well, the second stage of bringing the well to a stationary mode begins. The valve 25 is closed, and through the branch 33, after the valves 30 and 33 are brought into the open state, they are pumped in a dosed mode, the process fluid is a remover 38, for example, a paraffin scale inhibitor or a wide fraction of hydrocarbons that is between the working suspension of tubing 7 and small tubing 21 sent to the funnel 22 tubing of small diameter 21. The chemical composition of the process fluid (remover), its concentration and injection mode through outlet 33 and wellhead fittings is determined empirically.

Associated petroleum gas entering the well from the reservoir after oil separation through the ESP gas separator is passed through the annular space between the production casing 1 and the working tubing suspension 7 and sent through the valve 27 and the check valve 28 to the oil recovery flow line 20.

The laminar flow of the gas-liquid mixture 24, moving along the working tubing 7 from the ESP, at a depth of nucleation of paraffin crystals (L sp cnt _md ) is directed through a funnel 22 into the inner cavity of coaxially arranged tubing of small diameter, involving it in the turbulent mode of quadratic flow, and in the annular space of the working tubing and tubing of small diameter, using surface pumps (selectively), the working agent is removed - the paraffin paraffin remover. To control the operating mode of the well and the ESP, as well as the condition of the bore hole of the tubing cavity, the readings of pressure gauges 34, 37, data of the thermomanometric sensor 39, as well as debit measurements of the turbine meter connected to the flow line (not shown in Fig. 1) are used. In the case of paraffining of tubing of small diameter 21 through the outlet 33 of the wellhead reinforcement, the ASPO remover is pumped in the hot state (hot water, steam) through the annular space between the tubing 7 and tubing of small diameter 21 until the passage through the channel into the tubing of small diameter is completely restored.

Bibliography

1. Rogachev M.K., Strizhnev K.E. Fighting oil production complications. M .: Nedra-Business Center LLC. 2006 .-- 226 p.

2. Kovalenko K.I. et al. A method for controlling paraffin deposits in elevator pipes of oil wells and oil pipelines. Auth. Testimonial. No. 124896 of March 14, 1959, Bull. No. 24 1959.

3. Mazepa B.A. Protection of oilfield equipment from paraffin deposits. M .: Nedra, 1972.- 120 s.

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5. Islamov M.K. Development and implementation of removers of asphalt-resinous and paraffin deposits on oil equipment. Abstract of dissertation, Ph.D. Ufa: UGNTU, 2005 .-- 24 p.

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Claims (2)

1. The way to prevent deposits of asphalt-resinous and paraffin oil components on the inner surface of the tubing in the well, which consists in moving the crystals of paraffin released from the gas-liquid mixture to the center of the stream, followed by coagulation and washing the wall of the tubing for removal to the surface characterized in that the gas-liquid flow of well products moving in the cavity of the tubing, starting from the depth of onset of paraffin crystallization to the wellhead, they are reduced to the quadratic flow mode by switching to transportation through small diameter tubing, forming a turbulent mode of movement in their cavity, which continuously updates the wall-mounted oil film by swirling the stream, washing paraffin crystals from the pipe’s inner surface, and pumping -compressor pipes of small diameter, through the annular space, a remover of asphalt-resinous and paraffin deposits is metered injected. 2. A device for preventing deposits of asphalt-resinous and paraffin oil components on the inner surface of tubing in a well, containing wellhead fittings, a manifold, shut-off valves, for controlling well operation, downhole equipment, installation of an electric centrifugal pump on a suspension of working tubing pipes, characterized in that from the wellhead to the depth of the start of paraffin separation from oil in the cavity of the tubing workers, an additional pumping column is coaxially placed -compressor pipes of small diameter, suspended on the transitional flange of the wellhead reinforcement, with the possibility, through the outlets of the wellhead reinforcement and shut-off devices, to remove the asphalt-resinous and paraffin oil components into the annular space between the tubing and the tubing of small diameter.

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