Sucker-rod screw pump lifting system and oil-water separation method thereof

Abstract

The invention belongs to the technical field of oil production engineering, and particularly relates to a sucker-rod screw pump lifting system and an oil-water separation method thereof.The sucker-rod screw pump lifting system comprises an oil-string casing arranged in an oil production well and extending downwards to an oil layer; the Christmas tree lower four-way joint, the second casing pipe four-way joint and the motor are sequentially arranged above the oil-string casing pipe; the oil pipe is arranged in an inner cavity of the oil-string casing, and the top of the oil pipe is connected with the Christmas tree lower four-way in a hanging mode; and the transmission rod is arranged in the oil pipe, upwards penetrates through the concentric cylinder and is connected with the output end of the motor, and the bottom end of the transmission rod is connected with a pump shaft of a rod screw pump arranged at the bottom of the oil pipe. The transmission rod in the system not only has a power transmission function, but also has the characteristic of a multiphase cyclone separation function after being provided with continuous or discontinuous concave-convex or threaded grooves or bulges, so that the oil-water separation of an oil layer is almost completed under the condition of not increasing the production and operation cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil production engineering, and particularly relates to a rod-screw pump lifting system and an oil-water separation method thereof. Background Art

[0002] In oilfield development, due to the coexistence relationship of oil, gas and water in the reservoir, during the process of extracting oil from the reservoir to the ground, the problem of simultaneous production of oil, gas and water always occurs. To achieve oil-water separation, it is necessary to gradually aggregate from the single-well pipelines of individual wells to the central gathering station, and then after the separation treatment of oil, water and gas, it is dispersed to each water injection well point through the water injection pump station. Currently, there are mainly the following two oil-water separation methods in the central gathering station:

[0003] 1. The fluid of a single well is aggregated into the central gathering station. After being separated by a four-phase separator in the central gathering station, the water phase enters the sewage treatment station for treatment. After primary sedimentation and secondary sedimentation in the sewage treatment station, it is then supplied to the water injection station after coarse filtration, mainly for shallow oil layers with larger pore diameters.

[0004] 2. The fluid of a single well is aggregated into the central gathering station. After being separated by a four-phase separator in the central gathering station, the water phase enters the sewage treatment station for treatment. After primary sedimentation and secondary sedimentation in the sewage treatment station, it is then supplied to the water injection station after coarse filtration and fine filtration, mainly for medium and deep oil layers with smaller pore diameters.

[0005] For the above two methods, it is necessary to aggregate first, then sediment and separate, and then disperse to the water injection points, which increases the process and operating costs and naturally increases potential safety hazards.

[0006] Currently, most oilfield development has entered the middle and late stages, and the comprehensive water cut has basically reached more than 90%. The sewage treatment equipment in the central gathering station is in a high-load operation state for a long time. If an oil-water separation method for the same well is realized, that is: oil production from this well, treatment of this well, reinjection of this well or adjacent well reinjection and blending, etc., self-use or adjacent use mode, it will surely greatly save the transportation and treatment costs of the fluid and improve the oilfield development efficiency. Summary of the Invention

[0007] The present invention utilizes the rotational force during the conduction process of the ground power of the screw pump through the transmission rod to complete the concentric separation of oil and water in the oil pipe during the lifting process of the screw pump, and then designs a concentric cylinder inside a three-way or four-way joint at the wellhead to achieve oil-water separation.

[0008] This method achieves the purpose of oil-water separation with almost no additional cost. The separated oil is aggregated step by step through the single-well pipeline and then enters the central gathering station. In this way, the diameter of the single-well pipeline can be reduced to lower the cost; the separated oil layer water can be used for injection and production of the same well after measurement, or for water blending or injection of adjacent wells in the well cluster field.

[0009] The technical solution of the present invention is realized as follows:

[0010] In a first aspect, an artificial lift system of a progressing cavity pump provided by an embodiment of the present application includes: a production casing disposed in an oil production well, and the production casing extends downward to an oil reservoir; a Christmas tree lower cross-over, a second casing cross-over, and a motor disposed above the production casing in sequence; a tubing disposed in the inner cavity of the production casing, and the top of the tubing is hung on the Christmas tree lower cross-over; a transfer rod disposed in the tubing, and the transfer rod penetrates upward through the concentric cylinder and is connected to the output end of the motor, the bottom end of the transfer rod is connected to the pump shaft of the progressing cavity pump disposed at the bottom of the tubing, and a stirring assembly is disposed at the lower part of the transfer rod.

[0011] Optionally, the stirring assembly includes concave and convex teeth, a thread groove, and a protrusion sequentially arranged along the axial direction of the transfer rod.

[0012] Optionally, the concentric cylinder extends downward into the Christmas tree lower cross-over, and the extension length is 5 - 10 cm, and the length of the concentric cylinder is 30 - 50 cm.

[0013] Optionally, an angle valve or a choke is provided on the side connection of the second casing cross-over for controlling and regulating the water volume in the concentric separation of oil and water fluid.

[0014] In a second aspect, an oil-water separation method according to the artificial lift system of a progressing cavity pump provided by an embodiment of the present application includes:

[0015] Step S1: Lower a progressing cavity pump into the production casing disposed in the oil production well, and connect the progressing cavity pump and the surface motor through a transfer rod, so that the power of the surface motor is transmitted to the pump shaft of the progressing cavity pump through the transfer rod, and then the pump shaft rotates to lift the oil-water fluid in the tubing of the production casing.

[0016] Step S2: After the progressing cavity pump lifts the oil and water in the oil reservoir to the wellhead and completes the concentric separation along the rotation axis in the tubing, install a second casing cross-over with a concentric cylinder inside above the tubing hanger of the Christmas tree lower cross-over to complete the separation of oil and water with different path directions inside and outside the concentric cylinder; then install the upper hanging of the Christmas tree and the transmission components of the progressing cavity pump and the motor on the second casing cross-over.

[0017] Optionally, the stirring assembly on the transfer rod stirs and accelerates the concentric separation of the immiscible oil and water phases along the rotation axis of the transfer rod in the tubing.

[0018] Optionally, the water cut of the oil reservoir is 60 - 95%, the temperature is 40 - 90 °C, the rotation speed of the progressing cavity pump is 60 - 150 revolutions per minute, and the pump setting depth of the progressing cavity pump is greater than or equal to 600 meters.

[0019] Optionally, the design method of the inner radius value of the concentric cylinder includes:

[0020] Calculating the inner radius value of the concentric cylinder based on the water cut of the oil reservoir in the current oil well and the inner radius of the tubing.

[0021] Optionally, the inner radius of the tubing is 28 - 34 mm, and the inner radius value of the concentric cylinder is 8 - 12 mm.

[0022] The beneficial effects of the present invention are:

[0023] The present invention utilizes the rotational force during the transmission process of the surface power of the rod-screw pump through the transmission rod to complete the concentric separation of oil and water in the tubing during the lifting process of the screw pump. Then, a concentric cylinder is designed inside the three-way or four-way at the wellhead to achieve oil-water separation.

[0024] In this method, the transmission rod not only has the function of power transmission. After installing continuous or discontinuous concave-convex or threaded grooves or protrusions on the transmission rod, it also has the function characteristics of multiphase swirl separation. It almost completes the oil-water separation of the oil reservoir without increasing the production operation cost. It effectively utilizes the self-characteristics during the lifting process of the rod-screw pump to complete the oil-water separation, improves the economic benefits, achieves the effect of leveraging and saving production, and is a creative achievement in oil-water separation. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0026] Figure 1 It is a schematic structural diagram of a rod-screw pump lifting system;

[0027] Figure 2 It is a schematic structural diagram a when the second casing four-way in the rod-screw pump lifting system is in the working state;

[0028] Figure 3 It is a schematic structural diagram b when the second casing four-way in the rod-screw pump lifting system is in the working state.

[0029] Reference Numerals in the Drawings:

[0030] 1 - oil production well; 2 - oil reservoir; 3 - oil layer casing 3; 4 - rod-screw pump; 5 - motor; 6 - transmission rod; 7 - tubing; 8 - stirring assembly; 9 - four-way under the Christmas tree; 10 - concentric cylinder; 11 - second casing four-way; 12 - round hole; 13 - side pass; 14 - oil droplet; 15 - water droplet. DETAILED DESCRIPTION OF THE INVENTION

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0032] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0033] Embodiment 1

[0034] As Figure 1 shown, this embodiment is used to provide a rod pump lifting system, including:

[0035] The production casing 3 disposed in the production well 1, and the production casing 3 extends downward to the oil reservoir 2;

[0036] The Christmas tree lower cross joint 9, the second casing cross joint 11 and the motor 5 disposed in sequence above the production casing 3;

[0037] The tubing 7 disposed in the inner cavity of the production casing 3, and the top of the tubing 7 is hung on the Christmas tree lower cross joint 9;

[0038] The transfer rod 6 disposed in the tubing 7, and the transfer rod 6 penetrates upward through the concentric cylinder 10 and is connected to the output end of the motor 5. The bottom end of the transfer rod 6 is connected to the pump shaft of the rod pump 4 disposed at the bottom of the tubing 7. A stirring assembly 8 is provided at the lower part of the transfer rod 6, and the stirring assembly 8 includes concavo-convex teeth, threaded grooves and protrusions arranged in sequence along the axial direction of the transfer rod 6.

[0039] Secondly, the concentric cylinder 10 extends downward into the Christmas tree lower cross joint 9, and the extended length is 5-10 cm, and the length of the concentric cylinder 10 is 30-50 cm.

[0040] Secondly, an angle valve or a choke is provided on the side port 13 of the second casing cross joint 11 for controlling and adjusting the water volume in the concentric separated oil-water fluid.

[0041] Embodiment 2

[0042] This embodiment is based on Embodiment 1 and is used to provide an oil-water separation method based on a rod pump lifting system. The method includes:

[0043] Step S1: Lower a rod pump 4 into the production casing 3 of the production well 1, and connect the rod pump 4 and the motor 5 through a transfer rod 6, so that the power of the motor 5 is transmitted to the pump shaft of the rod pump 4 through the transfer rod 6, and then the pump shaft rotates to lift the oil-water fluid in the tubing 7 of the production casing 3. The stirring assembly 8 on the transfer rod 6 stirs and accelerates the separation of the incompatible oil and water phases in a concentric shape along the rotation axis of the transfer rod 6 inside the tubing 7.

[0044] Step S2: After the rod pump 4 lifts the oil and water in the oil reservoir 2 to the wellhead and completes the concentric separation along the rotation axis inside the tubing 7, install a second casing cross 11 with a concentric cylinder 10 inside above the tubing hanger of the four-way 9 under the Christmas tree, and complete the separation of the oil and water in different paths inside and outside the concentric cylinder 10; then install the upper hanging of the Christmas tree and the transmission components of the rod pump 4 and the motor 5 on the second casing cross 11.

[0045] Secondly, in this embodiment, the water cut of the oil reservoir 2 is 60-95%, the temperature is 40-90 °C, the rotation speed of the rod pump 4 is 60-150 revolutions per minute, and the depth of the rod pump 4 is greater than or equal to 600 meters.

[0046] Secondly, in this embodiment, the design method of the inner radius value of the concentric cylinder 10 includes:

[0047] Calculate the inner radius value of the concentric cylinder 10 based on the water cut of the oil reservoir of the current oil well and the inner radius of the tubing 7.

[0048] Secondly, the inner radius of the tubing 7 is 28-34 mm, and the inner radius value of the concentric cylinder 10 is 8-12 mm.

[0049] Embodiment 3

[0050] To further elaborate on the above steps, this application will use a complete case to illustrate the principle:

[0051] As Figure 1As shown in the figure, an oil production well 1 is selected. The reservoir it exploits is a low associated gas reservoir. Currently, the water cut of the oil layer 2 is 90%, and the oil layer temperature is 80°C. A rod pump 4 is installed in the production casing 3 of the oil production well 1, and the pump depth is 1100 meters. The set rotation speed is 120 revolutions per minute. An electric motor 5 is installed at the wellhead of the oil production well 1. The power of the rotation of the electric motor 5 drives the transfer rod 6 in the tubing 7 to rotate and move downward to the pump shaft of the rod pump 4. The oil-water fluid in the tubing 7 in the production casing 3 is lifted by the rotation of the pump shaft. By using the different oil-water densities during the process of lifting the oil-water fluid in the tubing 7 by the rod pump 4, and the different oil-water centrifugal forces during the rotation of the transfer rod 6 of the rod pump 4, through the function of lifting and stirring by the rotation of the transfer rod 6, the incompatible oil-water phases are accelerated to complete the concentric separation along the rotation axis of the transfer rod 6 in the tubing 7. During the process of lifting the fluid in the wellbore from the tubing 7 to the wellhead, in order to accelerate the concentric separation of the oil-water fluid in the tubing 7, some stirring components 8 are continuously or discontinuously installed on the transfer rod 6. The stirring components include concave-convex teeth, thread grooves and protrusions.

[0052] Because stirring and heating will both accelerate the oil-water separation of incompatible fluids or emulsified fluids, and the temperature of the oil layer 2 is a natural existence that accelerates the oil-water separation, therefore, the fluid temperature of the oil layer 2 is also an important factor for accelerating the separation of incompatible fluids by using the density difference during the lifting process, which is beneficial to achieving the concentric separation of oil and water along the rotation axis in the tubing 7 of the oil production well 1.

[0053] After the rod pump 4 lifts the incompatible oil-water fluid in the oil layer 2 to the wellhead and completes the concentric separation along the rotation axis in the tubing 7, a second casing cross 11 with a concentric cylinder 10 inside is installed above the tubing hanger of the four-way 9 (casing four-way) under the Christmas tree, and the separation of oil and water with different path directions is completed inside and outside the concentric cylinder 10.

[0054] As Figure 2 shown, the petroleum oil droplets 14 of the oil layer 2 inside the wall of the concentric cylinder 10 enter the upper suspension of the Christmas tree through the round hole 12 left at the top of the concentric cylinder 10 and then enter the collection system.

[0055] The water droplets 15 of the water in the oil layer 2 outside the wall of the concentric cylinder 10 pass through the side port 13 of the second casing cross 11, and then pass through the metering device of the choke and the meter installed on the side port 13 of the second casing cross 11 to control and measure the discharge amount of the oil layer water. The oil layer 2 water can be used for water injection into other layers of the same well (an injection electric pump is installed below the rod pump 4) after control and measurement, or can be used for water injection and / or water blending of adjacent wells in the well cluster field, thus saving the cost of the surface pipe network.

[0056] A concentric cylinder 10 is designed inside the second casing cross joint 11. The concentric cylinder 10 is suspended on the top plane of the second casing cross joint 11. The length of the concentric cylinder 10 can be inserted into the lower cross joint (casing cross joint) 9 of the production tree by 5 - 10 cm. Generally, the length of the concentric cylinder 10 is between 30 - 50 cm for easy installation. A round hole 12 through which the transfer rod 6 and the oil droplets 14 of petroleum pass is left at the central part of the top of the concentric cylinder 10, providing conditions for the concentric separation of the oil and water from the oil layer 2 after reaching the wellhead. The metering device of the choke and the flowmeter installed on the horizontal side port 13 of the second casing cross joint 11 is used to adjust and control the amount of water in the fluid of the concentrically separated oil layer 2. During the lifting process by the rod pump 4, the concave and convex teeth, thread grooves, and protrusions 8 that serve as stirring functions are continuously or discontinuously installed on the transfer rod 6 to complete the concentric separation of the fluid of the oil layer 2 in the tubing 7 along the rotational axis of the transfer rod 6. Finally, the oil layer water is separated and discharged in the second casing cross joint 11 at the wellhead.

[0057] The oil - water separation method during the lifting process by the rod pump, and the most important application method is: simultaneous injection and production in the same well. That is, after the oil layer water separated in the second casing cross joint 11 at the wellhead is adjusted and controlled for the outflow rate through the angle valve or the choke, it is then used for water injection in the same well through the flowmeter. This method can not only control the production fluid volume of the oil layer by the rotational speed of the rod pump 4, but also calculate the amount of produced petroleum, the amount of injected water, and the water cut of the oil layer simultaneously.

[0058] There are many factors affecting the design radius of the concentric cylinder 10, such as: the depth and rotational speed of the suspension of the screw pump, the strength of oil - water emulsification, the amount of liquid production, the fluid temperature, the water cut of the oil layer, etc. Through experimental verification, the main factor is the water cut of the oil layer. The determination of the water cut of the oil layer can be based on the water cut during the previous exploitation of this oil sand body in this well, or on the water cut of the adjacent wells exploiting the same oil sand body.

[0059] Confirmation of the design radius r of the concentric cylinder:

[0060] If the water cut of the oil layer is ω%, the inner radius of the tubing is R, the lifting speed of the screw pump is V, the bottom area of the concentric cylinder is Sr, and the cross - sectional area of the tubing is SR;

[0061] Then the volume of liquid lifted by the screw pump within time t is Q = SR·V·t;

[0062] Assume that the lifting speed V of the rod pump 4 for oil and water in the tubing 7 is the same, and the radius of the transfer rod is ignored;

[0063] Then the volume of petroleum lifted by the screw pump within time t is Q_oil = Sr·V·t;

[0064] Because Q_oil = Q(1 - ω%);

[0065] That is, Sr·V·t = SR·V·t(1 - ω%); Sr = SR(1 - ω%); πr2 = πR 2 (1 - ω%);

[0066] Therefore, r = R(1 - ω%) 1 / 2 ;

[0067] If the inner radius R of the oil pipe is 31 mm, then r = 10 mm.

[0068] In this embodiment, during the conduction of the ground power of the rod pump through the transfer rod 6, the rotational force is utilized to complete the concentric separation of oil and water in the oil pipe 7 during the lifting process of the screw pump. Then, a concentric cylinder 10 is designed inside the three-way or four-way (the second casing four-way 11) at the wellhead to achieve the separation of oil and water.

[0069] In this method, the transfer rod not only has the function of power transfer. After installing continuous or discontinuous concave-convex or threaded grooves or protrusions on the transfer rod, it also has the functional characteristics of multiphase swirl separation. Almost without increasing the production operation cost, it completes the separation of oil and water in the oil reservoir. It effectively utilizes the self-characteristics during the lifting process of the rod pump to complete the separation of oil and water, improves the economic benefits, and achieves the effect of leveraging strength for cost-saving production. It is a creative achievement in oil-water separation.

[0070] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its inventive concept, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A rod pump lift system, characterized in that, it includes: A production casing (3) disposed in the production well (1), and the production casing (3) extends downward to the oil reservoir (2); A production tree lower cross-over (9), a second casing cross-over (11) and a motor (5) disposed successively above the production casing (3); A tubing (7) disposed in the inner cavity of the production casing (3), and the top of the tubing (7) is hung on the production tree lower cross-over (9); A transfer rod (6) disposed in the tubing (7), and the transfer rod (6) penetrates upward through the concentric cylinder (10) and is connected to the output end of the motor (5). The bottom end of the transfer rod (6) is connected to the pump shaft of a rod pump (4) disposed at the bottom of the tubing (7). A stirring assembly (8) is provided at the lower part of the transfer rod (6).

2. The rod pump lift system according to claim 1, characterized in that, The stirring assembly (8) includes concave and convex teeth, threaded grooves and protrusions arranged successively along the axial direction of the transfer rod (6).

3. The rod pump lift system according to claim 1, characterized in that, The concentric cylinder (10) extends downward into the production tree lower cross-over (9), and the extended length is 5 - 10 cm, and the length of the concentric cylinder (10) is 30 - 50 cm.

4. The rod pump lift system according to claim 1, characterized in that, An angle valve or a choke is provided on the side port (13) of the second casing cross-over (11) for controlling and regulating the water volume in the concentric separated oil and water fluid.

5. The oil-water separation method of the rod pump lift system according to any one of claims 1 - 3, characterized in that, The method includes: Step S1: Lower a rod pump (4) into the production casing (3) disposed in the production well (1), and connect the rod pump (4) and the motor (5) through the transfer rod (6), so that the power of the motor (5) is transmitted to the pump shaft of the rod pump (4) through the transfer rod (6), and then the pump shaft rotates to lift the oil and water fluid in the tubing (7) of the production casing (3); Step S2: After the rod pump (4) lifts the oil and water in the oil reservoir (2) to the wellhead and completes the concentric separation along the rotation axis in the tubing (7), install a second casing cross-over (11) with a concentric cylinder (10) inside on the tubing hanger of the production tree lower cross-over (9) to complete the separation of the oil and water with different path directions inside and outside the concentric cylinder (10); then install the upper hanging of the production tree and the transmission components of the rod pump (4) and the motor (5) on the second casing cross-over (11).

6. The oil-water separation method according to claim 5, characterized in that, The stirring assembly (8) on the transfer rod (6) stirs and accelerates the concentric separation of the incompatible oil and water phases along the rotation axis of the transfer rod (6) inside the tubing (7).

7. The oil-water separation method according to claim 5, characterized in that, The water cut of the oil reservoir (2) is 60 - 95%, and the temperature is 40 - 90 °C.

8. The oil-water separation method according to claim 5, wherein, the design method of the inner radius value of the concentric cylinder (10) includes: calculating the inner radius value of the concentric cylinder (10) based on the water cut of the oil layer of the current oil well and the inner radius of the tubing (7).

9. The oil-water separation method according to claim 5, wherein, the rotational speed of the rod-screw pump (4) is 60 - 150 revolutions per minute, and the depth of the rod-screw pump (4) lowered into the well is greater than or equal to 600 meters.

10. The oil-water separation method according to claim 8, wherein, the inner radius of the tubing (7) is 28 - 34 mm, and the inner radius value of the concentric cylinder (10) is 8 - 12 mm.

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