RU2520674C1 - Downhole device for generation and transfer of flexure oscillations to productive stratum - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: device includes a sucker-rod pump unit and liner of pipes below the productive interval. The liner part covering the productive interval is assembled of resilient elements with flexural stiffness less than flexural stiffness of the pipes placed above it.

EFFECT: device is distinguished by a simple design and operational reliability; it allows essential increase in efficiency of the producing wells by generation and transfer of flexure oscillations to the productive stratum interval.

4 cl, 2 dwg, 2 ex, 1 tbl

Description

The invention relates to the oil industry and can be used to increase oil recovery in productive formations during their operation by downhole pumping installations.

A known method of operating wells with a sucker rod pump with a liner, that is, with an additional column of tubing installed under the pump in order to improve the conditions for the movement of the oil-water mixture to the pump. At the same time, the shank can be installed both in suspension and with emphasis on the face. In the latter case, the liner also provides unloading of the tubing string from excessive stresses (AS No. 1585502, class E21B 43/00, publ. 15.08.1990).

A device for wave action on the reservoir (RF patent No. 2133816, IPC E21B 28/00, E21B 43/25, publ. 07/27/1999), including a piston and a centralizer for placing them inside the production casing of the well, installed with the possibility of reciprocating along the longitudinal axis of the production casing of the well by means of a drive mounted on the day surface. The piston is made of at least two circular elements mounted on the side surface of the rod in transverse planes relative to the longitudinal axis of the production string with a longitudinal clearance 1 between them and with a radial clearance σ _{in the} transverse plane between the edge of the circular element and the inner surface of the production casing of the well, the thickness of the round element δ, the value of 1 longitudinal clearance, the value of the radial clearance σ selected satisfying the conditions of 0.1 <1 / D <100, 0.005 <δ / D <1; σ / D <0.3, where D is the inner diameter of the production string.

During the operation of the sucker rod pump, the reciprocating movement of the pump plunger causes the development of variable dynamic loads in the tubing string. The liner with emphasis transfers these dynamic loads to the environment and thus initiates the propagation of low-frequency elastic vibrations in the rock of the reservoir.

The wave effect on the productive formations leads to a decrease in the water cut of the produced products and an increase in oil recovery. In particular, the wave (or dynamic) impact on the bottom-hole zone of the reservoir helps to clean the pore space, the inner surface of the casing and perforation channels from mechanical deposits, salt deposits, asphalt-resin-paraffin deposits, and also leads to relaxation of excess stresses in the rock, reduces the effective viscosity of formation fluids, etc.

At the same time, the efficiency of transferring elastic vibrations excited by the operation of the deep well pumping unit and transmitted through the shank stop to the formation rock is low due to the quasi-vertical (parallel to the well axis) directivity of the force vector applied to the bottom of the well, remote from the reservoir to the depth of the sump of the well.

Closest to the proposed is a device for operating a well with a deep well pump with a liner (RF patent No. 2124119, IPC E21B 43/00, F04D 13/10, F04B 47/00, publ. 12/27/1998), containing a tubing string and support as part of this column. The shank is equipped with a filter and is made in the form of a support column of pipes with a length (1 m) equal to the distance from the pump intake to the rocks in the sump of the well, and the cross-section for metal (S (l _x ), mm) increasing with depth according to the law:

$$s(\underset{}{l_x)}=s_o{l}^{\alpha {\mathrm{one}}_x},$$

where S ₀ is the cross section at the beginning of the shank under the intake of the pump, mm;

α is an indicator of the rate of change of the shank section with depth, (a = l / l _x -ln (S (l _x ) / S ₀ );

l _x - the current length of the shank, m,

while the shank is made with the possibility of loading it with the weight of the tubing string to obtain pressure on the rocks in the sump (F _n , N), determined from the expression

F _n = (P _to ± ΔP) / S (l _x ) = (1.2-2) P _pl ,

where P is the weight of the entire tubing string with a shank, kg;

ΔР is the additional force of preloading or pulling up the tubing string at the mouth, N;

P _PL - reservoir fluid pressure, MPa.

In this invention, in order to change the stress field in the rock mass surrounding the borehole, the cross-sectional area of the liner pipes resting on the rock in the sump of the well increases exponentially when approaching the bottom of the well. In practice, an increase in the cross-sectional area of the liner is ensured by its stepwise layout, that is, the layout of sections of petroleum assortment pipes of various diameters with an increase in the diameter of the sections and, accordingly, an increase in their bending stiffness when approaching the bottom of the well.

A disadvantage of the known devices is that during low-frequency elastic vibrations, when the length of the excited waves significantly exceeds the characteristic dimensions of the liner (in this case, the length of the pipe sections that make it up), the transmission of elastic stresses through such a liner to the rock in the sump of the well occurs in a quasi-stationary mode, i.e. without amplification. Indeed, during the operation of the deep-pumping unit, the duration of the dynamic loading (unloading) phase of the tubing string is measured on the order of 0.5 s, and at a speed of sound in the metal of ~ 5100 m / s the characteristic length of the excited elastic wave will be approximately 2500-3000 m, which is almost an order of magnitude greater than the actual size of the shanks. This means that in reality the effect of dynamic amplification of elastic impulses when they pass through the liner with an exponentially growing section of the liner pipes will practically not occur and, in essence, such a liner will transfer the load on the rock in the well sump in a quasi-stationary mode, i.e. similar to a shank uniform in length. In addition, such a construction of the shank in the device has an additional disadvantage, namely, the extremely non-optimal direction of the vector of dynamic loads and the distance from which the loads are applied from the reservoir. Another disadvantage of the known device can be attributed to the fact that the condition for supporting the liner on the rock in the sump of the well substantially limits the scope of the device, namely: the device cannot be used in cased and cemented wells, since in such wells there cannot be open access to the rock due to artificial slaughter, which is a stop ring with a dividing plug set in it.

The technical problem solved by the invention is to increase the efficiency of production wells by optimizing the generation of wave action using the weight of the pumping unit and transmission of elastic vibrations in the interval of the reservoir.

The technical problem is solved by a downhole device for generating and transmitting elastic vibrations in the interval of the reservoir, including a rod-type pumping unit and a pipe liner with an emphasis below the production interval.

What is new is that the part of the shank that spans the production interval is composed of elastic elements with bending stiffness less than the bending stiffness of the upstream pipes.

It is also new that the elastic element is made in the form of one or more columns of sucker rods with the same or different bending stiffness.

Also new is the fact that a hollow piston with an outer diameter exceeding the diameter of the pipe part of the shank is installed in the composition of the upper pipe part of the shank.

The essence of the invention lies in the fact that in case of loss of stability of the shank due to the action of compressive longitudinal loads due to the weight of the pumping unit, its lower part takes the form of a spiral spiral with a variable pitch. During the operation of a deep-well pump installation, the amount of pressing force of the turns of the spiral part of the liner, for example, to the inner surface of the production string in the interval of the reservoir is periodically changed within certain limits, which causes the generation and transmission of dynamic stresses directly to the reservoir.

Part of the liner, composed of one or more columns of sucker rods with the possibility of overlapping the productive interval, optimally provides both high intensity of dynamic stresses transmitted to the reservoir and a large area of dynamic impact on the casing of the production string.

The value of the static load on the bottom of the well or a specially installed support with a rigid connection with the casing, due to the weight of the downhole pump unit, must exceed the amplitude of the dynamic loads propagating along the liner during operation of the downhole pump unit to prevent separation of the lower end of the liner in the stop zone under the action of dynamic loads developing in it.

The upper tubular part of the liner includes a hollow piston with an outer diameter exceeding the diameter of the tubular part of the liner to increase the intensity of the hydrodynamic pressure pulses in the well fluid.

Figure 1 shows a device with a single-column design of the part of the shank, covering the production interval.

Figure 2 shows a device with a two-column design of the part of the shank, overlapping the production interval.

The device includes a sucker-rod pumping unit 1 (Figs. 1 and 2), consisting of a sucker-rod pump 2 and an tubing string 3, and a shank 4 of pipes with an emphasis 5 (not shown on the bottom or anchor - not shown in Figs. 1 and 2) below the production interval 6. The part of the shank 4, overlapping the production interval 6, is composed of elastic elements 7. Above the junction of 8 elastic elements 7 with upstream pipes 4, through holes 9 are made in the body of its upper tubular part for the flow of formation fluid to the sucker rod pump 10 2. Elastic elements 7 (for example, pipes of a smaller diameter or rod) are made in the form of a single column 7 (Fig. 1) or several 11 and 12 (Fig. 2) with bending stiffness, lower bending stiffness of the upstream and downstream pipes 4 (Figs. 1 and 2 )

Above the through holes 9 for the flow of formation fluid to the intake 10 of the sucker rod pump 2, the upper pipe part of the shank 4 may include a hollow piston 13 (FIG. 2, not shown in FIG. 1) with an outer diameter exceeding the diameter of the pipe part of the shank 4.

The elastic elements 7 (FIG. 1) and the elastic elements 11 and 12 (FIG. 2) are configured to take the form of a single-start (FIG. 1) or multi-start (FIG. 2) helical spiral with a variable pitch when interacting with the well wall (in FIG. .1 and 2 not shown) or casing 14 under load.

The device operates as follows. The device (figure 1) is lowered into the well and at the stop 5 below the production interval 6 is unloaded by a predetermined value.

Preliminarily determine the magnitude of the lateral stresses transmitted to the reservoir by an elastic element 7, pressed against the casing 14 or the wall of the well under the action of a longitudinal load.

For engineering calculations of elastic deformations of the tubing string or rod string of elastic elements 7, the following dependence of the angle θ formed by the vertical and tangent to the elastic axis of the rod deformed in the form of a spiral at a point located at a distance z from the bottom of the well is used:

Sin ² θ = T (z) · R ^2/2 · E · J,

where T (z) = T _cf -q _w · z, where T _cf is the load on the bottom of the well, due to the weight of the downhole pumping unit (N), q _w is the weight of a unit length of the column in the borehole fluid (N), z is the vertical coordinate, counted up from the bottom of the well (m), R is the radius of the spiral (m);

E is the Young's modulus of the column material, for steel E = 2.2 · 10 ¹¹ N / m ² (2.2-10 ⁶ kg / cm ² );

J - the moment of inertia (meters ⁴⁾ of the column cross-section (J = πr ^4/4 for rods of radius r, J = π (r ⁴ -r _{FHS vntr} ⁴⁾ / 4 - Tubing with _FHS r - r _vntr and external - internal radius, EJ - column stiffness in bending).

The pressing force P _u (N / m) of the elastic rod under the action of the longitudinal compressive force T (N) to a surface with a radius of curvature R _k (m) per unit length of the contact line is expressed by the formula:

P _unit = T / R _k ,

and the curvature k = 1 / R _{k of the} helix is determined by the formula (Pogorelov A.V. Differential geometry. - M: Nauka, 1974. - 176 s):

k = Sin ² θ / R,

where R is the radius of the helix (m).

To calculate the pressing force P _u use the formula:

$${\text{P}}_{\text{units}}={\text{T (z)}}^{\text{2}}\cdot \text{R / 2}\cdot \text{E}\cdot \text{J}\text{.}\text{(one)}$$

The step L (m) of the coil of the helix is determined by the expression:

$$\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="00000005.png"\; state="\{\{state\}\}">L</figure-callout>}2=\text{8}{\mathrm{<figure-callout\; id="2"\; label="\pi "\; filenames="00000005.png"\; state="\{\{state\}\}">\pi </figure-callout>}}^{\text{2}}\cdot \text{E}\cdot \text{J / t}\text{.}\text{(2)}$$

where E is the Young's modulus of the column material, for steel E = 2.2 · 10 mN / m ² (2.2 · 10 ⁶ kg / cm ² ); J is the moment of inertia (m ⁴ ) of the cross section of the column, T is the longitudinal compressive load (N), π = 3.14159.

For the case of an elastic rod represented by a string of pipes or sucker rods (Mishchenko I.T. Well oil production: Textbook for universities. - M: FSUE Publishing House Oil and Gas named after IM Gubkin Russian State University of Oil and Gas, 2003. - 816 s), the effective radius of the helix of the elastic elements 7 is determined by the expression:

R = (D-d) / 2,

where D is the inner diameter of the casing or the diameter of the hole in an open hole (m),

d is the diameter of the rods or the outer diameter of the tubing (m).

Formula (1) is the main formula for calculating the lateral stresses transmitted to the reservoir 6 by a deformed liner 7 pressed against the casing under the action of a longitudinal load.

The calculation of the pressure drop at the intake of the pump 10, which causes a periodic load of tubing 3, is carried out taking into account the depth of the bottom of the well and reservoir 6, the depth of installation of the pump 2 of a given diameter, the depth of the dynamic liquid level (not shown), gas pressure in the annulus, water density and the density of oil, as well as their volumetric content in the mixture produced by the well.

Depending on the purpose of the impact (the bottom-hole zone of the reservoir or an extended section of the reservoir) and the principle of transferring the maximum energy of elastic vibrations to the rock of the reservoir, the structural characteristics of the elastic elements 7, covering the production interval 6, and, accordingly, the entire liner 4 as a whole, are determined.

To protect the pump 2 from lateral vibrations, it is advisable to install centralizers above and below the pump 2 (not shown in Figs. 1 and 2). If pump 2 is protected from lateral deformation by two centralizers installed above and below pump 2, then the value of the static load on the bottom of the well can be made very high - as much as possible it can be equal to the weight of the entire tubing string 3 from the bottom to the mouth (adjusted for buoyancy in liquids).

The magnitude of the compressive force of the elastic elements 7, covering the production interval 6 and composed of tubing or sucker rods, under the action of a longitudinal load equal to, for example, 40 kN, with an inner diameter of the production string 14 equal to, for example, 130 mm, are given in the table.

Table Diameter (wall thickness), mm The value of the pressing force, N / m Tubing 60.3 (5.0) 378 73.0 (5.5) 155 73.0 (7.0) 130 Sucker rods 16,0 64770 19.0 31530 22.0 17070 25.0 9940 28.0 6140

The magnitude of the pressing force of the elastic elements 7, covering the production interval 6 and composed of sucker rods, is ten times higher than the corresponding values for the layout of standard tubing, which makes the layout of the rods the most preferable for impact on the reservoir 6.

It is obvious that in order to increase the area of impact on the production casing or the walls of an open-hole well, it is advisable to elastic elements 7, overlapping the production interval 6, to assemble from at least two, 11 and 12 (figure 2) rod columns of the same or different bending stiffness as along the length of the rod columns, and along their cross section. To increase the strength of the column, it is advisable to additionally strengthen by welding the zones of the threaded connections of the rods 11 and 12, and in the zone of connection of the rods with the upstream and downstream tubing 4, install a transfer element (not shown in FIGS. 1 and 2) with an intermediate value of bending stiffness.

When applying dynamic loads developing during the operation of pump 2 (Figs. 1 and 2), on a static load, due to the weight of the downhole pump installation, the length of the turns of the contact line of the elastic elements 7 with the surface of the casing pipe 14 (open hole walls) will change there is this line will periodically move along the surface of the pipes 14 or the walls of the well. Essentially, the contact line will be a moving source of elastic impulses of stress transmitted directly to the reservoir during the operation of the sucker rod pump.

In addition, the periodic movement of this line on the surface of the casing 14 or the walls of the well will facilitate their cleaning, as well as cleaning the perforations in the production string 14 from deposits deposited on them. Note that, in this case, the area of the dynamic impact on the casing 14 or the borehole wall is not localized in a small area, but distributed over the entire productive interval 6, which contributes to a more sparing mode of impact, for example, on cement stone or rock walls.

The size of the overlapping zone of the productive interval 6 by the elastic elements 7 should be determined in accordance with the objectives of the wave impact on the reservoir. To achieve the areal effect of wave action, it is necessary to increase the size of the overlap zone to 50-100 m above the roof level of the productive formation 6 and under its sole, and to process the bottom-hole zone of the productive formation 6, it is advisable to reduce the amount of overlap from zero to several first meters, thereby increasing the amplitude dynamic impact on the bottomhole zone of the reservoir 6.

The size of the overlap zone should be selected in each case. Firstly, taking into account the size of the area of induced stresses in the rock mass around the well, caused by changes in reservoir pressure during the development of the reservoir, since the elastic energy of this region is a significant factor determining the effectiveness of long-wave action on the reservoir (Svalov AM Mechanics of drilling and oil and gas production . - M.: Book House "Librocom", 2009. - 256 s). To quantify the size of this region, it is most natural to take the size of the depression funnel, that is, the zone of low pressure formed around the existing production well, the effective radius of which can be estimated as 50-100 m. Secondly, it must be taken into account that in the overlap zone of - due to the strong pressing of the elastic elements 7 to the walls of the production string due to the action of friction forces, the amplitude of the elastic stress pulses decreases, reaching the production casing through the casing 14 and 6.

During the operation of the downhole pump unit, dynamic stresses propagating along the shank 4 will be superimposed on the stationary load due to the weight of the downhole pump unit. To prevent periodic separation of the shank 4 in the stop zone 5, it is necessary to select the value of the stationary load on the bottom or anchor based on the condition of no separation, that is, from the condition according to which the stationary load in the stop zone 5 must exceed the maximum range of dynamic loads propagating along the shank 4. The maximum range of dynamic stresses in the string is determined by the weight of the fluid raised by the pump to the wellhead, that is, it can be determined taking into account the diameter of the plunger of pump 2 and g Ubin installation and submerged under the fluid level in the well.

To increase the intensity of the hydrodynamic pressure pulses in the composition of the upstream pipes of the shank 4 - its pipe part, a hollow piston 13 (FIG. 2) is provided with an outer diameter exceeding the diameter of the pipe part of the shank 4. The hollow piston 13 is rigidly connected to the intake 10 of the pump 2 by means of the shank pipes 4, performs a reciprocating motion in the well fluid synchronously with the reverse movement of the intake 10 of the pump 2, which generates an oscillatory process of fluid particles in the well and, accordingly, in the bottom hole non-productive formation 6.

It is advisable that the through holes 9 for inflow of the well fluid to the intake 10 of the pump 2 be performed in the part of the liner from the pipes directly above the elastic elements 7 with reduced bending stiffness. This will contribute to better removal of water from the wellbore, as well as the initiation of additional fluctuations in the hydrodynamic pressure in the wellbore fluid.

An example of a specific application of the device.

The device is used in a long-running well cased with a 146 mm production casing 14 with a wall thickness of 8 mm. Productive formation 6 is re-opened by perforation in the interval 1600-1605 m, the depth of artificial slaughter is 1620 m.

The installation depth of pump 2 with a diameter of 38 mm (plunger area 11.34 cm ² ) is 1200 m. The dynamic level of the liquid exceeds the installation height of the deep pump 2 by 200 m and the gas pressure in the annulus is 8 atm (0.8 MPa).

The density of water is 1.01 g / cm, and the density of oil is 0.8 g / cm ³ . The produced mixture raised by the tubing string 3 consists of water and oil equally, and the specific gravity of this mixture is 0.9 cm ³ .

The pressure on the pump 2 from above, due to the weight of the mixture being raised, is 108 atm (10.8 MPa). The pressure from below - 20 atm (2.0 MPa) - is equal to the difference between the pressure of the oil (and gas) in the annulus and the pressure due to the weight of the liquid being lifted in the liner 4 before receiving 10 of the pump 2.

Thus, the pressure drop of 88 atm (8.8 MPa), multiplied by the plunger area of 11.34 cm ² , gives a force value of 10 kN (1 t), which causes additional periodic tension-compression of the shank 4.

The condition under which the separation of the liner 4 from the stop 5 in the well may occur when the wave process develops in the liner 4 is a static load of less than one ton. Thus, the static load on the bottom or anchor under the given conditions on the plunger of the pump 4 must be selected at least one ton.

We set the task of wave action in order to activate processes in the bottom-hole zone of the productive formation 6. We believe that the static load on the liner 4, due to the weight of the downhole pumping unit, is 40 kN at the level of the productive interval, and we calculate several examples of the liner design.

Example 1

The shank consists mainly of pipes with a diameter of 73 mm with a wall thickness of 5.5 mm. At the level of formation 6 with an overlap of 5 m above the roof and 5 m under the sole, one rod string 7 (Fig. 1) with a diameter of 28 mm is installed. The lower part of the shank (15 meters of the sump) is also composed of pipes with a diameter of 73 mm.

In this case, the lateral force (per meter of length) acting on the walls of the casing 14 at the level of the production interval 6 is 6140 N, which is approximately 40 times greater than the lateral force (~ 155 N) outside the production interval, i.e. dynamic impact on the formation 6 as much as possible exactly at the level of the formation 6.

The pitch of the helix winding at the level of the productive interval in this case is 3.62 m, and in the tubular part of the shank outside this interval is 17.0 m.

Example 2

The shank 4 consists mainly of pipes with a diameter of 73 mm with a wall thickness of 5.5 mm. At the level of formation 6 with an overlap of 5 m above the roof and 5 m under the sole, three rod columns with a diameter of 28 mm are installed (11, 12 and the third in FIG. 2 not shown), connected to each other in the upper and lower parts. The lower part of the shank 4 (15 meters of the sump) is also composed of pipes with a diameter of 73 mm.

In this case, the total lateral force over three rod columns (per meter of length) acting on the walls of the casing 14 at the level of the production interval 6 is 2047 N, i.e. more than an order of magnitude (~ 13 times) exceeds the side impact force (~ 155 N) outside the productive interval 6, i.e. dynamic impact on the formation 6 as much as possible exactly at the level of the formation 6.

The pitch of the helix of the elastic element 7 at the level of the productive interval 6 in this case is 6.27 m, and in the tubular part of the shank 4 outside this interval is 17.0 m.

Given the long period of operation of the well, the second example of the design of the liner 4 for the conditions of this well is selected.

The proposed device has a simple design, reliable in operation and can significantly increase the efficiency of production wells by generating and transmitting elastic vibrations in the interval of the reservoir. A significant improvement in the conditions for the generation and transmission of elastic vibrations in the interval of the reservoir is achieved by the fact that when the liner is unstable due to compressive longitudinal loads due to the weight of the pumping unit, its lower part takes the form of a spiral spiral with a variable pitch. During the operation of a deep-well pump installation, the amount of pressing force of the turns of the spiral part of the liner, for example, to the inner surface of the production string in the interval of the reservoir, periodically varies within certain limits, which causes the generation and transmission of dynamic stresses directly to the reservoir.

Claims (4)

1. The downhole device for generating and transmitting elastic vibrations in the interval of the reservoir, including a rod-type pumping unit and a liner of pipes with an emphasis below the production interval, characterized the fact that the part of the shank that covers the production interval is composed of elastic elements with a bending stiffness less than the bending stiffness of the upstream pipes. 2. The downhole device according to claim 1, characterized the fact that the elastic element is made in the form of one or more columns of pump rods with the same or different bending stiffness. 3. The downhole device according to claim 1 or 2, characterized in the fact that the static load at the stop of the liner, due to the weight of the compressed part of the column, exceeds the amplitude of the dynamic loads propagating along the liner during pump operation. 4. The downhole device according to claim 1 or 2, characterized the fact that a hollow piston with an outer diameter exceeding the diameter of the pipe part of the shank is installed in the composition of the upper pipe part of the shank.

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