RU2807169C1 - Production string disconnector - Google Patents

Abstract

FIELD: oil engineering products.

SUBSTANCE: invention can be effectively used as a disconnector for sections of production strings and liner strings at the final stage of well construction in case of complications caused by jamming during their descent and cementing. The production string disconnector includes a hollow body with an internal passage and with sealing rings and connecting threads at its ends and consists of an upper and lower parts. The upper and lower parts of the disconnector are connected to each other by a helicoidal thread. The bearing surface of the triangular profile helicoidal thread is made at an angle α, while α=0°30'-1°30' to thread centreline. The opposite face of the profile is inclined to the plane of the cross section of the disconnector, at an angle β, while β=15°-45°. Threaded helicoidal surface is made with taper k=1/20-1/50. The lower cylindrical section of the nipple is supported by a fitting ring with a height h₁ with the possibility of adjusting its height during the calibration of the disconnector and its assembly. The inner bore diameter of the disconnector is made commensurate with the inner diameter of the production string. At the upper end of the cylindrical lower body of the disconnector, at least two rectangular grooves are symmetrically located along the outer diameter D_n, with congruent locking teeth installed in them after assembly and calibration of the disconnector. The locking teeth are rigidly fixed by welds to the thrust end of the disconnector upper section with the possibility of transmitting torque from the upper part of the housing to the lower part.

EFFECT: increased efficiency of the production string disconnector.

1 cl, 3 dwg

Description

The proposed technical solution for the production casing disconnector (PEC) relates to petroleum engineering products. The production string disconnector can be effectively used as a disconnector for sections of production strings (EC) and liner strings at the final stage of well construction in conditions of complications caused by sticking during their running and cementing.

The need to include REC in the production string is justified by the fact that in recent years the spatial parameters of oil and gas wells, as well as their design, have changed; Most oil and gas wells are completed by drilling their trunks with a horizontal end. Under these conditions, the descent and advancement of the EC in the horizontal part of the wellbore to the bottom is associated with the appearance of additional loads from friction forces caused by the influence of the mass of the pipe string in contact with the lower generatrix of the horizontal section of the wellbore. The loss of mobility of the EC during its incomplete descent to the design depth, caused, most often, by complicating factors of a mining and geological nature, threatens, in the absence of a workable disconnector, with complex emergency work and loss of the wellbore, which leads to an increase in non-productive time and, in ultimately leading to higher costs for well construction. The proposed REC, if the area of its inclusion in the composition of the EC lowered into the well is reasonably chosen by specialists, will allow disconnecting the production string or liner in case of complications caused by sticking, with minimal loss of money and time.

Threaded disconnectors are known for lowering and disconnecting the lowered load-bearing string of pipes, when using which, by rotating the rotor, the lowered load-bearing string is opened. At the same time, a constant load is maintained on the hook of the traveling system of the drilling rig and the bearing column is jerked to the right, counting the number of revolutions, and the thread disconnection is checked by the value of the idle reverse rotation of the rotor [1]. The design of such a threaded disconnector is difficult to operate and does not achieve the assigned task. Due to large zenith angles in wells, disconnection requires repeated rotation of the drill string, since disconnection, as a rule, does not occur the first time, and if cement slurry has already been pumped into the well, an emergency situation occurs. In addition, a pin disconnector is also known, with the help of which drill pipes are disconnected from the casing pipes before they are cemented, after hanging the casing string on wedges while resting on the bottom [1]. Disconnection is carried out by unloading the column until the disconnector pins are cut off.

The domestic industry produces disconnectors of various designs under the codes PMP, PMPTs, PRK, RKZ, RRS, PCX, USTSOK, TsRU, etc. For example, PMP type devices are designed for lowering and hanging liners; PMPC is designed for running, cementing and hanging liners at the bottom of the production string; PRK is a suspension-disconnector with cams, for lowering and suspending hidden casing strings; RK3-cam disconnector with hydraulic shutter type RKZ; RRS - threaded disconnector for lowering hidden columns and casings with a diameter of 168 to 340 mm in difficult geological conditions; PCX - universal disconnector with trapezoidal thread with a large pitch; USTSOC is designed for joining and cementing column sections when casing deep wells in difficult conditions; CRU is a disconnector equipped with a collet; it is recommended for use when fastening wells with liners when their weight is low.

Disconnectors are known, produced, for example, by BITTEHNIKA LLC, as a tool for eliminating accidents in wells [2]. However, their use as connecting elements between EC pipes is excluded, like all of the above disconnectors, for technical reasons, because their internal diameter does not allow for the transportation of separation plugs through them if it is planned to complete the well with cementing of the liner.

When conducting patent studies of well-known technical solutions aimed at separating drilling, casing and production strings in a well, a fairly large number of intellectual property objects (inventions and utility models) were identified, which were considered as analogues, in particular: patent for an invention of the Russian Federation No. 2428557 " Disconnector", publ. 09/10/2011, bulletin. No. 25; RF patent for invention No. 2129650 “Disconnector”, publ. 04/27/1999; RF patent for invention No. 2278945 “Borehole disconnector”, publ. 06/27/2006, bulletin. No. 18; RF patent for invention No. 2425946 “Borehole disconnector”, publ. 08/10/2011, bulletin. No. 22; RF patent for invention No. 2439281 Downhole disconnector, publ. 01/10/2012, bulletin. No. 1; RF patent for invention No. 2625124 “Column disconnector”, publ. 07/11/2017, bulletin. No. 20.

The disadvantages of the above technical solutions are: the complexity of the design, as well as the inability to be built (included) into individual sections of production strings or liners due to the limited internal passage channel, which excludes the possibility of transporting process fluids with separation plugs.

The closest technical solution, in terms of technical essence, has been identified, adopted as a prototype - a drill string disconnector (RBC), protected by a patent for an invention [3], which is made as a hollow cylindrical body, with an internal passage, consisting of upper and lower parts connected between a triangular helical thread and connecting threads made in the upper and lower parts for connection with the drill pipe string, while the upper and lower parts are connected to each other by a cylindrical helical thread, with a large thread pitch of a triangular profile. In this case, the supporting surfaces of the helical thread are made at an angle to the main axis of rotation within 10°...15°. The tightness of the RBC is ensured by the use of sealing rings installed in the upper and lower parts of the RBC. The separation of the upper and lower parts of the RBC is ensured only by the relative rotation of the parts in the direction opposite to their make-up. However, despite the close similarity of the structural elements of the RBC with the claimed device, it cannot be used in production strings, since the separation of the RBC is possible only with forced rotation of the pipe string. This significantly limits and even excludes its use in the layout of production strings, since rotation of production strings in the well is not permissible.

The purpose of the invention is to create an efficient REC, with the possibility of its integration into the production casing (liner) and aimed at solving the problem that, in the event of loss of mobility of the production string in the wellbore caused by its unexpected sticking (jamming), disconnect the string at the REC installation site , will be possible by applying an axial tensile load, ensuring the disruption of the conical helical thread in the disconnector, eliminating the need to transfer torque (rotation) to the production string.

The expected positive technical result of the proposed solution is manifested:

- the possibility of connecting with elements of EC pipes, using congruent threaded connections, and ensuring that its internal diameter is equal to that of EC pipes, for the unhindered passage of separation plugs;

- the possibility of including it in the EC dimensional sections allocated by calculation and, as an option, including several disconnectors;

- in the possibility of separation, in case of stuck EK, by creating an axial tensile load on the upper part of the EK, to remove the upper (free) part of the pipes, and preserve part of the drilled wellbore;

- the ability to factory adjust the REC to the declared axial force of helical thread failure (Us);

- the ability to perform well completion work, incl. suspension of the EC in the intermediate column, using separation plugs, pumping of cement mortar and buffer fluid, as well as disconnection of the supporting column from the lowered EC, under conditions of flawless lowering of the EC (liner) to the designed depth.

The solution to the problem is achieved by the fact that the disconnector (REK) is made in the form of a cylindrical body, with connecting threads of the same name, like the production string, at its ends and includes an upper (nipple) and lower (coupling) part, which are connected to each other by a helical thread, with taper (k), length of the threaded section of the helical thread (L), with a large pitch (S) of the helical thread. In this case, the supporting surface of the helical thread of the triangular profile is made at an angle (α), within α=0°30'...1 ^o 30', to the axial (O) line of the thread, and the opposite face of the profile is inclined to the cross-sectional plane of the disconnector, at an angle (β), within β=15°...45°, and the working height of the profile (h ₂ ) of the helical thread is made from the ratio:

h ₂ =(Dн+Δ)⋅σт/(E⋅n)+S⋅k/2;

In this case, the taper of the threaded helical surface (k) is made (taking into account the recommendations of GOST 8593-81 on the choice of normal taper) in the range from k=(1/20...1/50), and the length (L) of the threaded section of the helical thread is made taking into account dependences L=Уc/((Dн-Δ)⋅π⋅Pоп⋅f⋅0.01); In addition, the lower cylindrical section of the nipple is supported in a fitting ring with a height of h ₁ , with the possibility of adjusting (changing) its height during calibration of the disconnector and its assembly, and the internal bore diameter of the disconnector is made commensurate with the internal diameter of the production string. At the upper end of the cylindrical lower body of the disconnector, there are rectangular grooves (at least two) symmetrically located along the outer diameter Dн, with retaining teeth installed in them, after assembling and calibrating the disconnector, which are fixedly fixed by welds to the upper part of the housing, with the ability to transmit torque from the upper (nipple) part of the housing to the lower (coupling) part.

The process of uncoupling (thread failure) of the EK from the axial tensile load on the EK is accompanied by overcoming the friction forces arising on the turns of the helical threaded connection of the upper and lower parts. The value of the thread breaking force depends on the initial setting of the REC, i.e. the amount of immersion when screwing the nipple (upper) part of the disconnector into the mating coupling (lower) part. And the deeper, during screwing, during the adjustment process, the nipple part with the thread is installed into the coupling part, the higher the value of the thread stripping force (Us). The failure of the helical thread of the REC, according to the invention, occurs without damaging the integrity of its component parts, as well as the thread profile of the helical threaded connection and can, if necessary, be repeated many times.

The production string disconnector according to this technical proposal is shown in the figures attached to the description (Fig. 1-3).

In fig. Figure 1 shows a diagram of the production string disconnector in a screwed-in operating state;

In fig. Figure 2 shows a fragment of a helical threaded connection of a production string disconnector;

In fig. Figure 3 shows a cross-section of the REC in the area of the end connection of the nipple and coupling parts.

The production string disconnector (Fig. 1) is made in the form of a cylindrical body, with connecting threads of the same name as the production string at its ends and includes the upper 1 (nipple) and lower 2 (coupling) parts, which are connected to each other by a helical thread ( Fig.2) with taper k=(1/20...1/50) and length (L) of the threaded section of the helical thread, taken from the ratio L=Us/((Dn-Δ)⋅π⋅Pop⋅f⋅0.01 ), with a large step (S). In fig. 2, for understanding, shows parameter (c), which determines the value of half the taper angle between the central axis of rotation O and the line of the generating cone of the helical threaded connection. The performance of the RBC is ensured by the optimal length of the threaded section of the helical thread (L), with a large thread pitch (S). On the upper part of the disconnector 1, there is a connecting pipe thread 3 and a nipple section 4, which includes an upper cylindrical section 5, which turns into an external helical thread 6, and a lower cylindrical section 7. The upper part of the disconnector 1, with a helical thread 7 in section L, is screwed with a mating internal thread of the lower (coupling) part of the disconnector 2. The body of the lower (coupling) part of the disconnector 2, in the lower part, is equipped with a nipple part 9, with a pipe connecting thread 10, for connection with the threaded connection EC. In this case, the internal diameter (din) of the nipple part 9 is made equal to the internal diameter of the EC (not shown in the figure). In the annular space between the end of the cylindrical nipple part 11 and the thrust end 12, in the inner part of the housing 2, an adjustable ring 13 is installed, with the possibility of selecting its height h ₁ during assembly and calibration of the disconnector. In the inner upper and lower parts of the disconnector body 2 there are annular grooves 14, 15, which are equipped with sealing rings 16, 17, with the possibility of creating a sealing ability for the REC. At the upper end of the disconnector housing 2, there are rectangular grooves 18 (at least two) symmetrically located along the outer diameter Dn, with retaining teeth 19 installed in them, after assembling and calibrating the disconnector. The retaining teeth 19 are connected by welds 20, with the thrust end 21 of the upper section 1.

An example of a specific design of a disconnector for a production string 168×10.6-L GOST 632-80, with the length of the lower section Lc - 500 m.

Initial data:

- wall thickness of EC pipes Δ=10.6 mm;

- yield strength (σ t) for the material “L” of the disconnector σ t = 66.80 kgf/mm ² ;

- mass (m) of one linear meter of pipes m=40.1 kg/m;

- n=1.2 - safety factor for the disconnector;

- pressure (Pop) of EC crimping, permitted by GOST 632-80 - 675 kgf/cm ² ;

- taper of helical thread k=1/30=0.0333;

- helical thread pitch S - 24 mm;

Let us determine the force (Us) of breaking the threaded connection of the disconnector for the factory setting: Us=n⋅Lc⋅m=2⋅500⋅40.1=40100 kgf=393.1 kN.

We calculate the working height of the profile (h ₂ ) of the helical thread from the ratio: h ₂ =(Dh+Δ)⋅σт/(E⋅n)+S⋅k/2S=(168+10.6)⋅66.80/(2 ,1⋅10 ⁴ ⋅1.2)+24⋅0.0333/2=0.873 mm.

The length (L) of the threaded section of the helical thread is determined from the condition

L=Uc/((DH-Δ)⋅π⋅Pop⋅f⋅0.01), mm;

where: f - 0.08 - coefficient of friction on the threaded connection;

L=40100/[(168-10.6)⋅3.14⋅675⋅0.08⋅0.01]=150.2 mm.

The internal diameter of the disconnector (Δв) is assumed to be equal to that of the EC, i.e. 147 mm.

The production string disconnector operates as follows. After lowering a set of the lower section of the EC into the well, for example, 500 m, an REC is screwed into the upper coupling part of the EC, configured to the calculated value of the helical thread shear force (Us). The make-up torque (Mkr) when connecting the EK with EK pipes must correspond to the make-up moment of the EK pipes. If there are no complications when lowering the EC into the well (plantings, tightening, oil and gas shows), it is lowered to the calculated depth and, in the future, the final work provided for in the well construction plan is carried out: hanging the EC (liner), pumping cement mortar, flushing, etc.) . In case of loss of mobility of the EC when lowering it into the wellbore and unsuccessful attempts by members of the drilling crew to restore it, the work performers may decide to disconnect the EC at the location where the EC is installed, for example, 500 m from the shoe. In this case, a tensile load is applied to the upper part of the EC that exceeds the calculated value of the thread breaking force (Us) of the EC. In this case, the upper part of the disconnector 1, with its nipple section 4, overcoming the frictional forces (not shown in the figure) on the contacts of the conical helical thread 6, breaks out in the axial direction O from the housing of the disconnector 8 and thereby disconnects the production string. Reducing the load on the tackle system (monitored by the weight indicator) of the drilling rig can serve as the basis for making a decision to raise the upper part of the EC. After disconnecting the EC at the RBC placement site, the wellbore is washed with process fluid and the free part of the EC is lifted out of the well.

The technical solutions adopted for implementation and the above-mentioned REC parameters allow the authors to assert that the proposed disconnector has manufacturability, and during assembly, with calibration on the stand, adjustment is provided for the disconnection force (breakout force) in the axial direction (without rotation) in a wide range of required disconnecting loads (30...80 tf). In this case, it is allowed to change the height of the fitting ring 13. Moreover, the internal diameter of the disconnector (Δin) is commensurate with the internal diameter of the EC and ensures the passage of the separation plugs used in the cementing process.

The proposed technical solutions in the REC, aimed at creating an efficient REC, with the possibility of its integration into the production casing (liner) and allowing the string to be disconnected by applying an axial tensile load to break the conical helical thread in the disconnector without rotation, have a novel design of the components and the required level of their perfection. They are in functional and constructive unity with each other, with the presence of signs of significant differences, which, in their totality, makes it possible to carry out the task, and the detailed design study of the components and parts of the REC testifies to its inventive level, as well as the possibility of mastering its production and successful application in the oil and gas industry.

Information sources:

1. Bulatov A.I., Izmailov L.B. and others. “Handbook for casing oil and gas wells.” M. Nedra, 1981.

2. Product catalog “Tools for eliminating accidents in wells” BITTEKHNIKA LLC 2018, Info@bittekhnika.ru.

3. Patent RU 2757481, IPC E21 V 17/06, “Drill string disconnector”, Publ. 10/18/2021 BI No. 29.

Explanations for the drawings and description of the application

1 - upper part of the disconnector;

2 - lower part of the disconnector;

3 - pipe coupling thread;

4 - nipple section of the upper part of the disconnector:

5 - cylindrical section of the upper part of the disconnector;

6 - conical section of the upper part of the disconnector with helical thread;

7 - lower cylindrical section of the upper part of the disconnector;

8 - disconnector body in the area of the internal helical tapered thread;

9 - lower nipple part of the disconnector housing;

10 - connecting pipe thread;

11 - end of the cylindrical nipple part;

12 - thrust end of the inner part of the disconnector housing;

13 - fitting ring;

14 - upper annular groove;

15 - lower annular groove;

16 - o-ring or rather;

17 - lower o-ring;

18 - rectangular groove;

19 - retaining tooth;

20 - weld;

21 - thrust end of the upper section of the disconnector;

Dн - outer diameter of the disconnector;

din - internal diameter of the disconnector;

O - axis of rotation of the disconnector;

L is the length of the threaded section of the helical thread;

h ₁ - height of the fitting ring;

h ₂ - height of the working profile of the helical thread;

k is the value of the helical thread taper;

α is the angle of inclination of the supporting surface of the helical thread profile to the axis of rotation of the disconnector;

β is the angle of inclination of the closing profile of the triangular helical thread to the plane perpendicular to the axis of rotation (O) of the disconnector;

S - helical thread pitch;

Δ - wall thickness of the pipes used in the production string, mm;

σт - yield strength of the metal of the disconnector parts, kgf/mm ² ;

E - Young's modulus, for steel (2.1⋅10 ⁴ ) kgf/mm ² ;

n - 1.2 - safety factor for disconnector parts;

Us is the thread breaking force.

Claims (16)

A production string disconnector, including a hollow body with an internal passage, consisting of upper and lower parts connected to each other by a helical thread, with sealing rings and connecting threads at its ends, characterized in that the helical thread is made conical, with a large pitch and the length of the threaded section helical thread, interconnected by mathematical relationships, while the supporting surface of the helical thread of a triangular profile is made at an angle α, with α=0°30'-1°30', to the center line of the thread, and the opposite face of the profile is inclined to the cross-sectional plane disconnector at an angle β, with β=15°-45°, and the working height of the profile h ₂ of the helical thread is made from the ratio: h ₂ =(D _n +Δ)⋅σ _t /(E⋅n)+S⋅k/2, where D _n is the outer diameter of the disconnector, mm; Δ - wall thickness of the pipes used in the production string, mm; σ _t - yield strength of the metal of the disconnector parts, kgf/mm ² ; E - Young's modulus, for steel it is 2.1⋅10 ⁴ kgf/mm ² ; n is the safety factor for the disconnector parts, equal to 1.2; S - helical thread pitch, mm; and the threaded helical surface is made with a taper k=1/20-1/50, while the length L of the threaded section of the helical thread is determined from the ratio: L=U _s /((D _n -Δ)⋅π⋅P _op ⋅f⋅0.01), where Y _c is the thread breaking force, kgf or kN; D _n - outer diameter of the disconnector, mm; Δ - wall thickness of the pipes used in the production string, mm; P _op - pressure testing of the production string, equal to 675 kgf/cm ² ; f - coefficient of friction on a threaded connection equal to 0.08; and the lower cylindrical section of the nipple is supported in an adjustable ring with a height h ₁ , with the possibility of adjusting its height during the calibration of the disconnector and its assembly, while the internal bore diameter of the disconnector is made commensurate with the internal diameter of the production string, at the upper end of the cylindrical lower body of the disconnector they are made symmetrically rectangular grooves located along the outer diameter _Dn , at least two, with congruent teeth-clamps installed in them after assembling and calibrating the disconnector, which are fixedly fixed by welds to the thrust end of the upper section of the disconnector with the possibility of transmitting torque from the upper part of the housing to the lower part .

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