Method and device for producing wave action on a production stratum

Abstract

A process for producing a wave action on a productive stratum consists in that a vibro-seismic action is performed on the bottom zone of a well by a hydraulic shock onto it, said shock being produced by dropping a column of well fluid (2) to the bottom (9) of a chamber (10) which is fixed in the lower part (3) of a tubing string (4) and interacts with the bottom of a well (1), wherein, during dropping, the well fluid (2) is accelerated along the length of the chamber (10). A device for producing a wave action on a productive stratum comprises a pumping unit, a tubing string (4) with an expanded perforated part (3), a chamber (10) which is fixed on the lower end of the tubing string (4), a plunger (7) arranged in the chamber (10) so that it can move axially and exit therefrom when it is in the top position thereof, linked by a rod (8) with the pumping unit, a channel (11) being provided in the plunger (7), that exits at the end surfaces of said plunger and is provided with an inverted valve which enables the fluid to flow from the chamber (10) to the expanded perforated part (3) of the tubing string (4).

Description

FIELD OF THE ART

The proposed invention relates to mining engineering and more particularly to a method for producing wave action on a productive stratum and to a device for carrying such method into effect.

PRIOR ART

Known in the art is a method for producing wave action on a productive stratum, disclosed in RU 2107814 A, comprising transmitting molecular-wave oscillations from an emitter of a hydraulic hammer installed at the well head along a flow string through its top level and along the column of fluid in the well and through the top level of the column to the productive stratum. Simultaneously with transmitting molecular-wave oscillations, pressure in the well is increased by delivering fluid from a pump with a pressure accumulator coupled with the inlet thereof to the flow string at the well head, and hydraulic impacts are created in the fluid column of the well by closing periodically the pump inlet by the emitter of the hydraulic hammer during transmitting the molecular-wave oscillations therefrom to the flow string and to the fluid column in the well.

However, using the known method involves large losses of energy during transmitting an impact pulse through the fluid wave guide whose length may reach 4500 meters.

Also known is a method for producing wave action on a productive stratum, described in SU 1710709 A, which comprises producing impacts with a dropping load onto a productive stratum and creating elastic oscillations in an oil-saturated stratum in the course of oil field exploitation, the impacts on the oil-saturated stratum being produced through the bottom of field-development wells.

The efficiency of the known method is insufficiently high due to the fact that the load, while dropping, experiences a resistance of the well fluid, which reduces its velocity and, consequently, its kinetic energy. Besides, the load found in the well fluid generates a smaller force due to the volume of fluid displaced by the load (its effective weight diminishes).

The closest analog in terms of the technical essence and attained result is the method for producing wave action on a productive stratum, described in U.S. Pat. No. 5,586,602 A, which comprises performing a vibro-seismic action on a bottom-hole zone by a hydraulic shock. Elastic oscillations in the productive stratum are generated by producing periodic shocks with a force not exceeding its limit value for elastic deformation of the hard cement behind the casing. Shocks on the well bottom are produced by a shock wave with a pressure drop at the wave front corresponding to the compression limiting strength of the perforated zone capped with a cement plug in the wave generation wells.

However, this method is also characterized by a low efficiency because the hydraulic shock is produced on a layer of fluid which damps the shock pulse.

Known in the art is a device for increasing rock permeability in the place of final resting, comprising a conical acoustic reflector connected to a generator of force waves at its end, communicated with a fluid wave guide. The wave concentrator and wave reflector are made in the form of truncated cones tightly interconnected by their larger bases and provided with a hydraulic hammer passed through the smaller base of the wave concentrator with the possibility of its reciprocation with a valve, striker and branch pipe, the wave reflector being made with an exponentially decreasing cross-section, the wave radiator being made with a cross-section diminishing in accordance with the relationship: ${\mathrm{Fu}}_0=\frac{{\rho }_u·a_u·F_u+{\rho }_L·a_L·F_L}{{\rho }_{u_0}·a_{u_0}},$
where ρ_u0, α_u0 are the density of the emitter material and the wave velocity in the emitter material in zero cross-section, respectively,

ρ_u, α_u, F_u are the same emitter parameters in the current sections of the emitter;

ρ_L, α_L, F_L are the wave guide fluid density and the reduced section of the fluid wave guide along the emitter length, respectively, the acoustic reflector having a length not smaller than the wave length.

The known device has a low effectiveness because of the necessity to transmit shock waves to a well depth which may reach 4.5 km.

Besides, there is known a device for producing wave action on a well bottom zone (see SU 1017790 A), comprising a casing equipped with ports for disposing a hot mixture and a spark plug therein, a valve shutting the ports being mounted in the casing, the space thereunder being connected with a control unit.

To the known device a limited possibility of repeated action of a well bottom zone is inherent due to the necessity of using a hot mixture whose volume is limited. The device under consideration can be employed for cleaning (repairing) well filters, because this is a non-recurrent operation on each horizon and it is necessary to perform this operation only a few times on different horizons. However, such a device is not suitable for intensifying oil recovery, i.e., for generating shock pulses with a frequency of approximately 10 Hz around the clock and during months or at least during tens of days. Besides, in this device there takes place ineffective utilization of combustion products which, issuing from the ports, affect the mud fill and are partially directed upwards along the well, i.e., the energy of this part of the combustion products is wasted.

The closest analog in terms of the technical essence and attained effect is the device for producing wave action on a productive stratum, disclosed in U.S. Pat. No. 5,586,602 A, which comprises a lifting mechanism in the form of a pumping unit installed at the well-head and a tubing string with an expanded perforated lower part, intended for suspending the device in the production well from a Christmas tree. The device further comprises a cylinder with a seating ring installed on the bottom end of the tubing string, a plunger connected to the pumping unit, installed in the cylinder so that the plunger exits from the cylinder at the top of the upstroke, a rod whose one end is connected to the pumping unit and whose other end is attached to the plunger, and also a supply device intended for mounting on the Christmas tree, and a container intended to be mounted on the day surface.

However, the effectiveness of this device is low due to the necessity of spending energy for the compression of fluid in the tubing string. Besides, the thrown fluid strikes the fluid, and the latter behaves as a damper which cushions the stroke, the wave action effectiveness being thus lowered.

DISCLOSURE OF THE ESSENCE OF THE INVENTION

The main object of the invention is to provide a method for producing wave action on a productive stratum wherein a hydraulic shock would be produced on a surface exerting minimum damping action on the shock, whereby it would be possible to raise the effectiveness of the shock and correspondingly of the wave action on the productive stratum; as well as to provide a device for carrying out this method, which would be highly effective, would have a high reliability, and would not require highly qualified service personnel.

The posed problem is solved by that in a method for producing wave action on a productive stratum, which comprises performing vibro-seismic action on a bottom-hole zone by a hydraulic shock, according to the proposed technical solution, the hydraulic shock is produced by dropping a column of well fluid to the bottom of a chamber which is fixed to the lower part of a flow string and interacts with the well bottom. During dropping, the well fluid is accelerated along the length of the chamber.

The chamber may rest directly against the well bottom or against a liner secured in the well bottom.

The hydraulic shock produced against the bottom of the chamber is transmitted to the productive stratum, damping being substantially ruled out, so that it becomes possible to raise the effectiveness of action on the productive stratum and to increase the production of oil.

The posed problem is solved also by that in the device for producing wave action on a productive stratum, which comprises a pumping unit, a tubing string with an expanded perforated lower part, a cylinder, a plunger arranged in the cylinder in such a manner that it can move axially and exit therefrom when it is in the top position thereof, a rod whose one end is connected to the plunger and whose other end is connected to the pumping unit, according to the proposed invention, the cylinder is made with solid walls and constitutes together with the plunger a chamber, the plunger being provided with one channel outgoing to its end surfaces, and with an inverted valve which enables the fluid to flow along the channel from the chamber to the perforated expanded part of the flow string.

Such an embodiment of the device makes it possible to carry the proposed method for producing wave action on a productive stratum into effect, i.e., to produce a shock pulse by raising a column of well fluid, accelerating it, and dropping thereof to the bottom of the chamber.

It is expedient to make the external surface of the bottom of the chamber such that it should rest directly against the well bottom.

With such embodiment it is possible to provide wave action on the surrounding zone of the well.

It is also possible to make the external surface of the bottom of the chamber such that it should rest against a liner secured in the well bottom. Such embodiment makes it possible to transfer the hydraulic shock pulse to a greater depth and thereby to increase the effectiveness of the wave action on the productive stratum.

It is desirable that the inverted valve should be located in the channel of the plunger. This will preclude the fluid flow in the device from the space above the plunger into the chamber and provide the fluid flow from the chamber into the space above the plunger during the plunger downstroke.

In another embodiment of the device the inverted valve may be made in the form of a resilient membrane which is secured on the upper end face of the plunger and overlaps the plunger channel

Such structural embodiment of the device, while ensuring single-direction travel of the fluid flow (from the chamber to the space above the plunger), simplifies the structure and, this being the main thing, makes it possible to use the weight of the well fluid column for pressing the membrane to the end face of the plunger, i.e., to enhance the reliability of the inverted valve operation.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further explained by a description of particular variants of embodying thereof and by the accompanying drawings, in which:

FIG. 1 shows a device for producing wave action on a productive stratum, according to the invention, installed in a well, longitudinal section;

FIG. 2 shows the same as FIG. 1, partially, with a plunger with two channels and a membrane inverted valve.

BEST VARIANTS OF EMBODYING THE INVENTION

FIG. 1 shows a device for producing wave action on a productive stratum, according to the invention, installed in a well 1 filled with a well fluid 2, secured at a required depth in a lower part 3 of a tubing string 4. The lower part 3 of the tubing string 4 is expanded and provided with perforation holes 5. Secured below the expanded part 3 of the tubing string 4 is a cylinder 6 inside which a plunger 7 is arranged reciprocatingly and secured by means of a rod 8 to a pumping unit (not shown in the drawings). The cylinder 6 is made with solid walls, has a bottom 9, and together with the plunger 7 makes up a chamber 10. The plunger 7 is arranged is such a way that it can exit from the cylinder 6 when it is in the top position thereof. A through channel 11 is provided in the body of the plunger 7 in such a way that it can exit at the end surfaces thereof. and has an expansion 12 in the middle part, which makes up a seat 13 to which a ball 16, which is the movable member of the inverted valve, is pressed by a conical spring 15.

The inverted valve may be of any design. Thus, FIG. 2 shows a structure of the inverted valve in the form of a resilient membrane 17 secured in the central portion of the upper end face of the plunger 7. In that case the plunger is provided with several through channels 11′ which communicate space 18 above the plunger and the space of the chamber 10 (the space below the plunger). The membrane 17 overlaps entrance to the channels 11′ from the side of the space 18 above the plunger. In the variant of the device embodiment shown in FIG. 1 the external surface of the bottom 9 rests against a liner, which is a tube 19 cemented in the face of the well 1. However, the external surface of the bottom 9 of the chamber 10 may rest directly against the face of the well 1 (not shown in the drawings).

The method for producing wave action on a productive stratum consists in performing a vibro-seismic action on a well bottom zone by a hydraulic shock. The hydraulic shock is produced by dropping a column of well fluid to the bottom of a chamber which is fixed in the lower part of a tubing string and interacts with the wall bottom.

The method according to the invention makes it possible to raise the effectiveness of wave action on a productive stratum due to the fact that the dropped fluid flies down with a large speed without experiencing resistance from the fluid layer with a pressure equal to the pressure of the well fluid at a corresponding depth. Besides, the shock of the dropped fluid acts on a metallic bottom, so that damping of the shock is practically ruled out. An advantage of the proposed method is also in using a column of well fluid as the shock producing mass.

The proposed method for producing wave action on a productive stratum will become better understood from the following description of the operation of the device shown in FIG. 1.

Cemented into the bottom of the well 1 is the tube 19 against which the cylinder 6 secured below the expanded part 3 of the tubing string 4 rests with its bottom 9. The plunger 7 is arranged in the cylinder 6, the space 18 above the plunger being filled with the well fluid 2. The ball 16 of the inverse valve is pressed to the seat 13, and thereby the channel 11 is overlapped, and the flow of the fluid 2 from the space 18 above the plunger to the space of the chamber 10 (the space under the plunger) is ruled out. The weight of the column of the well fluid and the spring 15 determine the force with which the ball is pressed to the seat 13 of the plunger 7.

In another structural embodiment of the inverted valve, shown in FIG. 2, tight sealing of the chamber is determined by the resilient properties of the membrane 17 which overlaps the channels 13 of the plunger 7 and by the weight of the column of the well fluid 2, found above the plunger 7.

A pumping unit lifts the plunger 7 from the cylinder 6 with the aid of the rod into the expanded part 3 of the tubing string 4. Since the diameter of the plunger 7 is smaller than the diameter of the expanded part 3 of the tubing string 4, a gap is formed between their side surfaces, into which the well fluid starts running from the space 18 above the plunger. Through the perforation holes 5 in the expanded part 3 of the tubing string 4 the well fluid 2 comes from the well 1 into the interior of the tubing string 4. As a result, the well fluid occupies all the interior of the tubing string 4. Consequently, through the gap between the side surface of the plunger 7 and the inner surface of the expanded part 3 of the tubing string 4 the well fluid 2 starts to run down and, gaining speed, drops to the bottom 9 of the chamber 10. The stroke of the plunger 7 and, consequently, the length of the chamber 10, depends on the amplitude of swinging of the pumping unit. The entire mass of the well fluid 2 located in the well 1 above the plunger 7 which is in its upper position is accelerated. The length along which the entire mass of the well fluid is accelerated is determined by the height of the chamber 10 (of the cylinder 6), and at the end of the acceleration the column of the well fluid strikes against the bottom 9 of the chamber 10.

The shock pulse thus generated is transmitted to the tube 19 (in the case when the device rests against the wall bottom, the shock pulse is transmitted directly to the wall bottom), and through said tube and the bottom of the well 1 the shock pulse acts on the productive stratum. Using the tube 19, it is possible to transmit more effectively the shock pulse to the productive stratum which lies deeper than the bottom of the well 1. The surrounding rock, being a damper, attenuates the shock pulse. Therefore the expedience of using a particular structural solution is determined by the production requirements. If it is necessary to transmit the shock pulse to a large depth, then it is expedient to use a liner—the tube 19 cemented into the bottom of the well 1. If it is necessary to act with a shock pulse on the bottom zone of the well 1, it is expedient to use a second variant, when the chamber 10 rests with its bottom 9 directly against the well bottom.

The well fluid 2 completely fills the chamber 10. In the next step the plunger 7 is lowered. The plunger descends by gravity from the expanded part 3 of the tubing string 4 into the cylinder 6. The ball 16 under the action of fluid in the chamber 10 moves away from the seat 13, compressing the spring 15 (if the latter is provided), and enters the expansion 13 of the channel 11 of the plunger 7. In principle, the device can operate without the spring 15 as well. In that case the ball 16 will be raised and lowered by the static pressure of the fluid in the chamber 10 (when the plunger 7 is lowered) and in the expanded part 3 of the tubing string 4 (when the plunger 7 is raised). The spring 15 increases the reliability of the inverted valve operation. As the plunger 7 goes down, the fluid 2 (because of its incompressibility) will flow through the channel 11 into the space 18 above the plunger, i.e., into the expanded part 3 of the tubing string 4. When the plunger 7 reaches its lower position, its raising with the aid of the rod 8 is started. Raising of the plunger 7 is performed till the plunger proves to be in the expanded part 3 of the tubing string 4. Then the cycle is repeated as described above. The shock pulse is produced by the falling column of the well fluid in each cycle. The frequency of the cycles depends on the rocking frequency of the pumping unit. Usually this frequency is up to 10-12 swingings per minute. Any hoisting unit may be used instead of the pumping unit, for example, an electromagnet, a winch, etc., which can be located on the surface or in the well 1. Taking into account the large height of the column of the well fluid, and, consequently, its large mass, the stroke of the plunger 7 can be reduced, and the frequency o shocks will be thus increased. The column of the well fluid can correspond to or be smaller than the depth of the well. In the latter case the height of the well fluid can be limited artificially by installing a packer (not shown in the drawings, because this is a commonly known technique). The well 1 for producing wave action on a productive stratum can be either drilled specially, or one of low-yield or abandoned wells can be used for this purpose.

INDUSTRIAL APPLICABILITY

The method and device for producing wave action on a productive stratum are intended for use in the oil-and-gas industry for raising the effectiveness of the oil and gas stock recovery.

Claims

1. A method for producing wave action on a productive stratum, which comprises performing a vibro-seismic action on the bottom zone of a well (1) by a hydraulic shock thereon, characterized in that the hydraulic shock is produced by dropping a column of well fluid (2) to the bottom (9) of a chamber (10) which is fixed to the lower part (3) of a tubing string (4) and interacts with the bottom of the well (1), wherein during dropping the well fluid (2) is accelerated along the length of the chamber (10).

2. The method according to claim 1, characterized in that the chamber (10) rests with its bottom (9) directly against the well bottom.

3. The method according to claim 1, characterized in that the chamber (10) rests with its bottom (9) against a liner secured in the well bottom.

4. A device for producing wave action on a productive stratum, which comprises a pumping unit, a tubing string (4) with an expanded perforated part (3), a plunger (7) arranged in a cylinder (6) so that it can move axially and exit therefrom when it is in the top position thereof, a rod (8) whose one end is connected to the plunger (7) and whose other end is connected to the pumping unit, characterized in that the cylinder (6) is made with solid walls and together with the plunger (7) makes up a chamber (10), the plunger (7) being provided with at least one channel (11) which can exit tat the end surfaces thereof and with an inverted valve inverted valve which enables the fluid to flow along the channel (11) from the chamber (10) to the expanded perforated part (3) of the tubing string (4).

5. The device according to claim 4, characterized in that the external surface of the bottom (9) of the chamber (10) is adapted to rest directly against the well bottom.

6. The device according to claim 4, characterized in that the external surface of the bottom (9) of the chamber (10) is adapted to rest against a liner secured in the well bottom.

7. The device according to claim 4, characterized in that the inverted valve is arranged in the channel (11) of the plunger (7).

8. The device according to claim 4, characterized in that the inverted valve is made in the form of a resilient membrane (17) which is secured on the upper end face of the plunger (7) and overlaps the channel (11) of the latter.