RU2398091C2 - Hollow bucket rod - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: invention relates to oil producing equipment, namely to hollow bucket rods. Hollow bucket rod can be jointed to coupling element and has thread on its end to engage with that of said coupling element. Note here that proposed rod features inner diametre D1 held over entire length of the rod, outer diametre D2 at the rod center and outer diametre D3 at rod end with length L1. Note here that D3 exceeds D2. Note here that rod both ends have outer tapered thread with length L2. Aforesaid coupling element represents a coupling with inner tapered thread and outer diametre d, d-to-D1 ratio varying from 2.0 to 3.0.

EFFECT: expanded operating performances, higher efficiency, possibility to use small-diametre tubing string.

6 cl, 5 dwg, 2 tbl

Description

The invention relates to the field of oilfield engineering and is intended for use in sucker rod pumping units for oil production.

BACKGROUND OF THE INVENTION Pump rods are known in the art that are screwed into a rod string transmitting a reciprocating or rotational movement from a suspension point of a surface drive rod to a plunger of a downhole pump. The rod is a rod of circular cross section, at the ends of which there are sections with a thread for attaching the connecting elements. The rods are interconnected by couplings in a rod column. For example, GOST 13877-80 provides for the manufacture of rods with a nominal length of 8000 mm. To select the required column suspension length, shortened rods of 1000, 1200, 1500, 2000 and 3000 mm length are manufactured. To connect rods of the same size, couplings are produced, and rods of different sizes are transferable couplings. The rods are delivered with couplings screwed onto one end. The open thread of the rod and coupling is protected by caps or plugs.

A known sucker rod (RU 2169250 C1, 06/20/2001), providing the transfer of reciprocating motion from the drive to the sucker rod pump, comprising a rod made of composite polymer material, such as fiberglass, metal heads installed on both sides of the ends of the rod having a connecting part with a threaded element and an installation part with an internal cavity including annular cylindrical zones and annular conical zones, the diameters of the annular cylindrical zones and the smallest diameters The end conical zones are larger than the outer diameter of the rod, and having a thrust surface in a plane perpendicular to the axis of the head for fixing the end part of the rod on it, as well as adhesive filling the space between the surface of the inner cavity of the mounting part of the head and the outer surface of the rod with the formation of an adhesive joint and conical wedges that secure the heads to the rod. The disadvantage is the use of a polymer material, which significantly reduces the strength of the rod and can lead to the formation of microcracks on its surface.

Known metal construction of sucker rods with couplings made in the form of a rod of circular cross section, which are made in accordance with GOST R51161-2002. The main purpose of these rods is to transfer the reciprocating motion from the drive of the rocking machine located at the mouth of the oil well to the plunger of the deep-well pump located in the well. The main parameters of the known rod designs are:

1. The outer diameter of the coupling (d), which determines the necessary internal diameter of the pump pipes, inside which the reciprocating movement of the rods with the couplings. Typically, the outer diameter of the couplings is chosen so that the rod string with the couplings can move freely in the tubing string — tubing 73, for example, with a duct diameter of 62 mm or tubing 89 with a duct diameter of 76 mm.

2. The area in the minimum section (S), which determines the permissible operational loads on the rod string. The larger the cross-sectional area, the lower the level of internal stresses and the greater the margin of fatigue strength of the structure.

A disadvantage of the known rod designs is their lack of an internal longitudinal channel, which in some cases is necessary to ensure the technological processes used in oil production, for example, to provide lifting or pumping fluid from the deep pump to the wellhead along the pipe string and vice versa, as well as fluid withdrawal two layers at the same time, etc.

Known design options for sucker rods with welded heads and couplings and with an internal longitudinal channel, which are also made in accordance with GOST R51161-2002. The design of hollow rods made in accordance with GOST R51161-2002 allows the reciprocating movement from the drive of the rocking machine to the plunger of the submersible pump. When comparing hollow rods with rods made in the form of a rod of circular cross section (GOST R51161-2002), it can be seen that the rods have the same outer dimensions of the couplings (d), but a smaller area in the minimum cross section (S), which leads to their lower reliability at operation, while the rods according to GOST R51161-2002 have an internal longitudinal channel with a diameter of 8.5 to 11.0 mm. The presence of a longitudinal channel makes it possible to realize a new opportunity, namely, to pump through the longitudinal channel from the wellhead to the plunger of the deep pump various reagents that improve the properties of the pumped liquid. However, due to the limited size of the diameters of the longitudinal channel (from 8.5 mm to 11.0 mm), it is impossible to pump fluid from the reservoir to the wellhead through this channel, since in this case hydraulic losses will be from 350 to 110 atmospheres, which can lead to to the hanging of the plunger of the deep pump in the upper position, as well as to a significant excess of the pressure achieved during crimping, which is a drawback of analogues. Another disadvantage of analogues is the presence of a weld in the design of the rods. It is known that welded structures have low fatigue strength and their use in the manufacture of submersible equipment is undesirable. Another disadvantage of the analogue are cylindrical threads, which do not ensure the tightness of the threaded connection at high pressure in the channel of hollow pipes.

Significant disadvantages of the analogue - pump hollow rods with welded heads and couplings in accordance with GOST R51161-2002 - are the small area of the minimum cross-section, leakage of threaded joints, as well as the inability to pump fluid from the well through their longitudinal channel due to its small size.

Known "Extended Assembly of the column for the transmission of motion" (RU 2003129631/06 A, 2003.09.26), containing hollow sucker rods and connecting elements, connected to each other along the axis between the drive of the wellhead and a deep rotary pump located in the well, each hollow pump rod has an end with an internal thread adapted to engage with the external thread of the connecting element, while the free end of each hollow pump rod contains an annular shoulder for transmitting torque. The disadvantage of this design is the monofunctionality of the rod, namely: the use only for transmitting torque when working in the well with a rotary pump in the assembly of the string of pump pipes for pumping fluid from the well. The presence of shoulders increases the outer diameter of the rod string, which excludes its use in the string of pumping pipes of small diameter, as well as its use in the rod string to provide reciprocating movement from the rocking machine located at the wellhead to the deep rod pump. However, the design of the pump rod of this technical solution for the essential features is the closest to the problem being solved, therefore this technical solution is taken as a prototype of the claimed invention.

The technical task of the claimed invention is the provision of the transfer of reciprocating motion from the rocking machine located at the wellhead to the downhole sucker rod pump for lifting fluid from the sucker rod pump to the wellhead and pumping fluid from the wellhead to the plunger of the sucker rod pump by using a pumping string pipes of small diameter.

The technical result is achieved due to the well-known hollow pump rod, made with the possibility of connecting along the axis with a connecting element, having ends at the ends, made with the possibility of engagement with the thread of the connecting element, according to the invention, the rod has an inner diameter D1, an outer diameter D2 and sections of the length of the rod L1 located at its ends, which are made with a diameter D3 larger than D2, while on both ends of the rod an external conical thread is made with a length of L2, and L2 is always smaller than L1, and connecting the th element is made in the form of a coupling and has an internal tapered thread and an outer diameter d, the ratio of which with the inner diameter of the rod D1 is in the range from 2.0 to 3.0, while the minimum cross-sectional area of the rod S _{min is} calculated outside the sections L1 according to the formula :

,

,

and rod options are selected in accordance with table 1.

Table 1 Hollow sucker rod (claimed design) Type designation Coupling outer diameter d (mm) Rod Inside Diameter, D1 (mm) Sectional area, S (mm ² ) SHNT 27 × 4 42,2 19.0 289.0 SHNT 32 × 4,5 48.3 23.0 389.0 SHNT 36 × 5.5 52,2 25.0 490.0 SHNT 36 × 7 52,2 22 637.0

Additionally, at the ends of the rod, a square section of length L3 is made for a turnkey grip.

The invention is illustrated by drawings:

Figure 1 shows a General view of a hollow pump rod.

Figure 2 shows a diagram of the injection of fluid from the wellhead to

deep rod pump.

Figure 3 shows a diagram of the rise of fluid from a deep-well pump to the wellhead.

Figure 4 presents a graph of pressure loss in hollow sucker rods with different diameters of the longitudinal channel in comparison with analogues.

Figure 5 shows a General view of a hollow pump rod with square sections for a turnkey capture.

The claimed hollow pump rod contains a rod 1 and a connecting element 2 (figure 1) and, being an element of the rod string 3 (figure 2, 3), is used as part of the rod deep pump unit 4 (figure 2, 3). The rod 1 and the connecting element 2 are coaxial and oriented along the axis of the straight cylinder.

The rod 1 (figure 1) has an inner diameter D1, an outer diameter D2 and length sections of the rod L1 located at its ends, which are made with an outer diameter D3, while D3 is made larger than D2.

At both ends of the rod, an external conical thread with a length of L2 is made, and L2 is always smaller than L1 (Fig. 1), while the cross-sectional area of the rod S _{min is} calculated outside the sections L1. Additionally, as an option, at the ends of the rod, a square section of length L3 can be made for a turnkey capture (Fig. 5).

The connecting element is made in the form of a coupling and has an internal conical thread and an outer diameter d, the size of which depends on the size of the inner diameter of the rod D1 with a diameter difference in the range from 2.0 to 2.4. The coupling is made with the possibility of assembling the hollow sucker rods in the rod string 3 (Fig.2, 3).

The hollow pump rod in the assembly of the rod with the sleeve forms a longitudinal channel 5 (Fig. 1), while the longitudinal channel 5 forms a continuous cylindrical channel inside the column of pump pipes of small diameter 6 (Fig. 2, 3), for example, tubing 73 (channel diameter 62 mm) or of tubing 89 (channel diameter 76 mm), and by transmitting reciprocating motion from the rocking machine 7 located at the wellhead to the deep-well sucker rod pump 8, it provides pumping and dosing of process fluids (FIG. 2). Moreover, the claimed hollow pump rod due to the possibility of increasing the internal diameter of the longitudinal channel can also be used to remove technological fluids and solids from the well (Fig. 3). In addition, such a rod can be used as part of a rod column for oil production from two oil reservoirs at the same time (figure 3), which indicates its multifunctionality and that distinguishes it from the prototype.

The use of the claimed hollow pump rod makes it possible to adjust, depending on the requirements of the given technological mode of operation of the rod string, the strength of the rod string when subjected to axial tensile load and internal pressure, which depend on the cross-sectional area of the rod, which is calculated in the narrowest place. Choosing the necessary ratio of dimensional parameters, we calculate the minimum cross-sectional area of the rod according to the formula:

.

.

The data obtained are shown in table 2:

- with the inner diameter of the rod D1 measuring 19.0 mm; and the outer diameter of the coupling d of 42.2 mm in size, the cross-sectional area of the rod S _min is 289.0 mm ² ;

- with the inner diameter of the rod D1 size 22.0 mm; and the outer diameter of the coupling d of size 52.2 mm, the cross-sectional area of the rod S _min is 637.0 mm ² .

- with the inner diameter of the rod D1 measuring 23.0 mm; and the outer diameter of the coupling d of size 48.3 mm, the cross-sectional area of the rod S _min is 389.0 mm ² .

- with the inner diameter of the rod D1 measuring 25.0 mm; and the outer diameter of the coupling d is 52.2 mm, the cross-sectional area of the rod S _min is 490.0 mm.

After a comparative analysis with the known rods, we conclude that the diameters of the declared hollow sucker rods are calculated so that the minimum cross-sectional area S _min is within the dimensions of the analog rods according to GOST R51161-2002 (see table 2), and the cross-sectional area the hollow sucker rod S _{min is} calculated outside the sections L1 in the narrowest place of the hollow sucker rod.

table 2 Hollow sucker rod with coupling (in accordance with GOST R51161-2002) Symbol Coupling outer diameter d (mm) Rod Inside Diameter D1 (mm) Cross-sectional area S _min (mm ² ) SHN 19 42.0 - 286.3 SHN 22 46.0 - 386.8 SH 25 56.0 - 506.0 SH 29 60.0 - 613.4 Hollow sucker rod with welded heads and coupling (according to GOST R51161-2002) - - - - ShNPP 22 46.0 8.5 326.5 ShNPP 25 56.0 9.2 379.8 ShNPP 29 60.0 11.0 514.7 Hollow sucker rod with coupling (claimed design) SHNT 27CH × 4 42,2 19.0 289.0 SHNT 32 × 4,5 48.3 23.0 389.0 SHNT 36 × 5.5 52,2 25.0 490.0 SHNT 36 × 7 52,2 22 637.0

As can be seen from table 2, the values of the cross-sectional area of the claimed rod are within the limits established by GOST. The results obtained in comparison with the analogue in accordance with GOST R51161-2002 indicate that the claimed hollow pump rod in its characteristics is not inferior to analogues, but in terms of functionality of the prototype.

Hollow sucker rod operates as follows.

Using the coupling 2, the rod 1 (Fig. 1) is installed in the rod column 3 (Figs. 2, 3), which is an integral element of the sucker rod pumping unit 4. The reciprocating machine 7 sets the reciprocating motion with the magnitude of the stroke and frequency, corresponding to the specified operating mode of the deep-well pumping unit. The rod column 3 transmits the movement from the rocking machine 7 to the plunger of the deep rod pump 8, thus realizing the main function of the rod deep pump installation - the process of oil production, as well as pumping or pumping fluid into the well.

Hollow sucker rods are designed to transmit movement from the rocking machine drive to the plunger of the deep sucker rod pump while continuously or periodically supplying 6 corrosion inhibitors, inhibitors against deposition of paraffin, paraffin solvents, coolants, demulsifiers, and hydraulic protection fluid from the sucker rod pump into the pump pipe cavity. Oil can be pumped out both along the longitudinal channel 5 of the rod string 3 (FIGS. 2, 3) and in the annular space between the outer diameter of the rod string 3 and the inner diameter of the pump pipe string 6.

The rod string operates in difficult conditions, it is affected by an aggressive downhole environment and variable loads, leading to the accumulation of fatigue phenomena in the rod string. In addition, the rod string wears out due to friction against the inner surfaces of the pump pipes.

During operation of the rod string, the following loads act on the hollow pump rod:

- static - the weight of the rod column, taking into account the buoyancy force and the weight of the liquid column above the plunger of the deep rod pump, height from the dynamic level of the liquid, minus the volume occupied by the rod column;

- dynamic - the inertia forces of the moving masses of the rod string and fluid, since their movement is accelerated, as well as the vibration forces caused by wave phenomena occurring in the rod string during pump operation;

- frictional forces of the rod string against pipes and liquids arising from the pumping out of highly viscous fluids and emulsions, their value can be commensurate with the weight of the string;

- compressive stresses that occur during the downward movement of the hollow sucker rods during the pumping out of viscous fluids and emulsions and which adversely affect the durability of the rod string.

The destruction of the rod column is fatigue. For long-term operation of the rod column, you must be able to correctly calculate and select it.

When operating the rod string under standard conditions, hollow sucker rods with a small outer diameter are used, and under severe conditions that cause compressive stresses during the downward stroke of the rod string when pumping viscous fluids and emulsions that require reinforcing this section, hollow sucker rods of larger diameter are used.

The durability of the rod string is greatly influenced by the design and manufacturing technology of the hollow pump rod, as well as the hardening methods used in the manufacture, especially the condition of the outer surface of the rod body. The manufacture of rods without reinforcing strength can lead to the formation of microcracks on the body of the rod, which act as stress concentrates and centers of corrosion.

The claimed hollow pump rod can be made, for example, of steel grade 40X GOST 4543-71, while to increase the fatigue strength of the rod, the outer surface of the rod has two outer diameters D2 and D3, and D3, on the section of which the thread is made, is always larger than D2. Also, the design of the claimed hollow pump rod provides for the presence of sections of the length of the rod L1 at its ends, which are always greater than the length of the thread with sections L2.

The graph (figure 4) shows the pressure loss in the hollow sucker rods with different diameters of the longitudinal channel in comparison, for example, with analogues, where A is the pressure loss in the hollow sucker rods made according to GOST R51161 - 2002; B - pressure loss in the hollow sucker rods of the claimed invention. After a comparative analysis of the pressure loss inside the hollow sucker rods with different diameters of the longitudinal channel, we conclude that the pressure loss in the claimed hollow sucker rod is much less than in analogues.

The claimed hollow sucker rod has the following advantages:

1. The outer diameter of the couplings d is almost equal, and in some cases less than that of the structures of the analogue and prototype, which does not impose restrictions on the applicability of the claimed design.

2. The area in the minimum cross section S _{min is the} same or even larger than that of analogues, which guarantees high strength properties of the claimed design.

3. The diameter of the internal channel of the pump pipes from 15.5 to 35 mm ensures that when lifting the liquid, minimal hydraulic losses do not exceed the recommended pressure of pressure testing (40 atmospheres).

4. The absence of a welded joint in the claimed design eliminates the risk of premature fatigue failure.

5. The use of sealed tapered threads in a threaded connection in accordance with the procedure guarantees the tightness of threaded connections at pressures up to 200 atmospheres.

The claimed invention completely solves the technical problem. The technical result consists in the design of a hollow pump rod multifunctional with the possibility of its use in a sucker rod pump unit as a part of a sucker rod to provide reciprocating movement from the wellhead drive to a sucker rod pump, while performing functions such as pumping process fluids removal of fluid and mechanical impurities from the well, as well as pumping oil from two layers at the same time, while reducing energy expenses during underground well repair, reducing the likelihood of complications during the operation and underground repair of small-diameter wells, increasing the productivity of a sucker-rod pump installation using a string of pumping pipes of small diameter.

Claims (6)

1. The hollow pump rod made with the possibility of connection along the axis with the connecting element, having at the ends of the thread made with the possibility of engagement with the thread of the connecting element, characterized in that the rod has an inner diameter D1 made along the entire length of the rod, the outer diameter D2, made in the middle part of the rod, and the outer diameter D3, made at the ends of the rod with a length L1, and D3 is greater than D2, while at the both ends of the rod an external conical thread is made with a length of L2, moreover, L2 is always smaller than L1, and the connecting lement is designed as a sleeve and has a tapered internal thread and an outer diameter d, the ratio of which to the internal diameter D1 rod is in the range from 2.0 to 3.0 with a minimum area S _min is calculated boom section beyond the length L1 rod portions by the formula :

2. The rod according to claim 1, characterized in that the inner diameter of the rod D1 is made with a size of 19.0 mm; and the outer diameter of the coupling d is made in the size of 42.2 mm, while the cross-sectional area of the rod S _min is 289.0 mm ² . 3. The rod according to claim 1, characterized in that the inner diameter of the rod D1 is made with a size of 22.0 mm; and the outer diameter of the coupling d is made of 52.2 mm, while the cross-sectional area of the rod S _min is 637.0 mm ² . 4. The rod according to claim 1, characterized in that the inner diameter of the rod D1 is made in the size of 23.0 mm; and the outer diameter of the coupling d is made with a size of 48.3 mm, while the cross-sectional area of the rod S _min is 389.0 mm ² . 5. The rod according to claim 1, characterized in that the inner diameter of the rod D1 is made with a size of 25.0 mm; and the outer diameter of the coupling d is made of 52.2 mm, while the cross-sectional area of the rod S _min is 490.0 mm ² . 6. The rod according to claim 1, characterized in that at the ends of the rod an additional square section of length L3 is made for a turnkey capture.

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