CN118564227B - A downhole multiphase separation device for injection and production in the same well - Google Patents

Abstract

The invention discloses an underground multiphase separation device for injection and production in the same well, which relates to the technical field of underground separation equipment and comprises a sleeve body, an oil pipe body, a gas-liquid separation device and a plurality of mixed gas separation devices, wherein the oil pipe body is arranged in the sleeve body, an oil sleeve annulus is arranged between the sleeve body and the oil pipe body, a liquid inlet pipe, a liquid outlet pipe and a plurality of air outlet pipes are arranged on the side wall of the sleeve body, the liquid inlet pipe is connected with the liquid inlet end of the gas-liquid separation device, liquid flowing out of the liquid outlet end of the gas-liquid separation device can flow out through the liquid outlet pipe, one end of the air outlet pipe is communicated with the first air outlet end of the mixed gas separation device, a plurality of vent holes and a converging through hole are arranged on the side wall of the oil pipe body, the second air outlet end of each mixed gas separation device is communicated with the oil sleeve annulus through a vent hole corresponding to the oil sleeve annulus, and gas in the oil sleeve annulus flows into the oil pipe body through the converging through hole. The invention can realize underground gas-liquid separation and mixed gas separation.

Description

A downhole multiphase separation device for injection and production in the same well

Technical Field

The invention relates to the technical field of downhole separation equipment, and in particular to a downhole multiphase separation device for injection and production in the same well.

Background Art

In the current petrochemical industry, the separation of produced liquids on the ground using separators and towers is a common separation method. Currently, the commonly used separators include settling tanks (separation based on the expansion of the airflow volume and the reduction of the flow rate), wire mesh gas-liquid separators (separation based on the different gas and liquid particle sizes), membrane separation (using the pressure difference of the mixed components as the power, separation through the difference in the transmission rate of the membrane), baffle separators (separation based on the inertia of the droplets, deviation from the direction of the airflow and gravity separation). All of the above methods require the produced liquid to be lifted to the ground, and the working pressure and cost-effectiveness are low. At present, there is an urgent need for low-cost and high-efficiency underground separation equipment.

The "two-stage tubular gas-liquid separator adapted to a wide range of changes in inlet gas content" mentioned in patent CN202210483236.X uses "centrifugal force + gravity" to achieve separation of gas and liquid phases, but cannot separate mixed gases; the "system for selectively absorbing and separating _CO2 gas from a mixed gas rich in _CO2 " mentioned in patent CN202322337698.3 uses "absorption tower and phase separator to selectively absorb _CO2 in the mixed gas" to achieve mixed gas separation, which has the disadvantages of large footprint and low efficiency. It can be seen from this that there is no equipment in the prior art that can be applied underground and can separate gas, liquid and mixed gases.

Therefore, there is an urgent need in the art for an underground multiphase separation device for injection and production in the same well to solve the above problems.

Summary of the invention

The purpose of the present invention is to provide an underground multiphase separation device for injection and production in the same well to solve the problems existing in the above-mentioned prior art, which can be used underground and can also perform gas-liquid separation and separation between mixed gases.

To achieve the above object, the present invention provides the following solutions:

The present invention discloses a downhole multiphase separation device for injection and production in the same well, comprising a casing body, an oil pipe body, a gas-liquid separation device and a plurality of mixed gas separation devices, wherein the oil pipe body is arranged inside the casing body, and an oil-casing annulus is formed between the casing body and the oil pipe body, the gas-liquid separation device and the plurality of mixed gas separation devices are arranged inside the oil pipe body, and the gas-liquid separation device is located below the mixed gas separation device, and a liquid inlet pipe, a liquid outlet pipe and a plurality of gas outlet pipes are arranged on the side wall of the casing body, one end of the liquid inlet pipe is located outside the casing body, and the other end of the liquid inlet pipe is connected to the liquid inlet end of the gas-liquid separation device, and the liquid flowing out of the liquid outlet end of the gas-liquid separation device can Entering into the liquid outlet pipe, one end of the liquid outlet pipe away from the gas-liquid separation device is located on the outside of the casing body, the gas separated by the gas-liquid separation device flows to the mixed gas separation device located at the bottom, and the liquid separated by the gas-liquid separation device flows out through the liquid outlet pipe, one end of the gas outlet pipe is connected with the first gas outlet end of the mixed gas separation device, a plurality of air vents and a converging through hole are provided on the side wall of the oil pipe body, the second gas outlet end of each mixed gas separation device is connected with the oil casing annulus through the corresponding air vent, the converging through hole is located above the mixed gas separation device, and the gas in the oil casing annulus flows into the oil pipe body through the converging through hole.

Preferably, the gas-liquid separation device is an axial flow cyclone.

Preferably, the liquid inlet pipe is fixed obliquely on the side wall of the sleeve body.

Preferably, the lower end of the oil pipe body is a hemispherical structure, a liquid outlet is provided at the center of the hemispherical structure, and a one-way flow control device is provided at the liquid outlet.

Preferably, the one-way flow control device is a valve body;

The valve body includes an upper polygonal plate, an intermediate cone and a lower circular plate. The upper polygonal plate is fixed to the upper end of the intermediate cone, and the lower circular plate is fixed to the lower end of the intermediate cone. The areas of the upper polygonal plate and the lower circular plate are both larger than the area of the liquid outlet, and the intermediate cone is located at the liquid outlet.

Preferably, two packers are provided between the casing body and the oil pipe body, and the two packers are respectively located at the upper and lower ends of the mixed gas separation device.

Preferably, the mixed gas separation device is a mixed gas separation membrane.

Preferably, two mixed gas separation devices are provided.

Preferably, a partition plate is provided above each of the mixed gas separation devices, and the partition plate is fixed inside the oil pipe body.

Preferably, the mixed gas separation membrane is an arc surface structure.

Compared with the prior art, the present invention has achieved the following technical effects:

The present invention is based on the tubing body and the casing body, and can be extended into the well for use, without taking the produced material to the ground for separation, thereby effectively improving the mining efficiency. The present invention can also perform gas-liquid separation and mixed gas separation on the produced liquid in the well in sequence, and finally obtain methane and transport it upward through the tubing body, realizing multiple functions through one device, and saving costs.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

FIG1 is a schematic structural diagram of a downhole multiphase separation device for injection and production in the same well according to an embodiment of the present invention;

FIG2 is a partial enlarged view of a gas-liquid separation device in a downhole multiphase separation device for injection and production in the same well according to an embodiment of the present invention;

3 is a schematic diagram of the structure of an axial flow cyclone in a downhole multiphase separation device for injection and production in the same well according to an embodiment of the present invention;

FIG4 is a schematic structural diagram of a valve body in a downhole multiphase separation device for injection and production in the same well according to an embodiment of the present invention;

5 is a schematic diagram of the structure of a mixed gas separation membrane in a downhole multiphase separation device for injection and production in the same well according to an embodiment of the present invention;

FIG6 is a diagram showing the migration path of methane in a downhole multiphase separation device for injection and production in the same well according to an embodiment of the present invention;

In the figure: 1-casing body; 2-oil pipe body; 3-axial flow cyclone; 4-liquid inlet pipe; 5-valve body; 6-liquid outlet pipe; 7-packer; 8-mixed gas separation membrane; 9-partition plate; 10-gas outlet pipe; 11-vent hole; 12-merging through hole.

DETAILED DESCRIPTION

The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

The purpose of the present invention is to provide an underground multiphase separation device for injection and production in the same well to solve the problems existing in the above-mentioned prior art, which can be used underground and can also perform gas-liquid separation and separation between mixed gases.

In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

As shown in Figures 1 to 6, the present invention provides a downhole multiphase separation device for injection and production in the same well, comprising a casing body 1, an oil pipe body 2, a gas-liquid separation device and a plurality of mixed gas separation devices, wherein the plurality of mixed gas separation devices may be one, two or more. The oil pipe body 2 is arranged inside the casing body 1, and the casing annulus is between the casing body 1 and the oil pipe body 2. The gas-liquid separation device and the plurality of mixed gas separation devices are all arranged inside the oil pipe body 2, and the gas-liquid separation device is located below the mixed gas separation device, and the plurality of mixed gas separation devices are arranged adjacent to each other up and down. The side wall of the casing body 1 is provided with a liquid inlet pipe 4, a liquid outlet pipe 6 and a plurality of gas outlet pipes 10, wherein one end of the liquid inlet pipe 4 is located outside the casing body 1, and the other end of the liquid inlet pipe 4 is connected to the liquid inlet end of the gas-liquid separation device, that is, the produced liquid outside the casing body 1 enters the gas-liquid separation device through the liquid inlet pipe 4. The liquid flowing out of the liquid outlet end of the gas-liquid separation device can enter the liquid outlet pipe 6. One end of the liquid outlet pipe 6 away from the gas-liquid separation device is located outside the sleeve body 1. The gas separated by the gas-liquid separation device flows to the mixed gas separation device located at the bottom, and the liquid separated by the gas-liquid separation device flows out through the liquid outlet pipe 6. The number of gas outlet pipes 10 is the same as the number of mixed gas separation devices and the positions are arranged one by one. The mixed gas separation device has a first gas outlet end and a second gas outlet end. The two different gases after separation are respectively located at the first gas outlet end and the second gas outlet end. One end of the gas outlet pipe 10 is connected to the first gas outlet end of the mixed gas separation device, and the other end of the gas outlet pipe 10 is located outside the sleeve body 1, so that the gas at the first gas outlet end is discharged to the outside of the sleeve body 1. A plurality of vent holes 11 and a converging through hole 12 are provided on the side wall of the oil pipe body 2. The second gas outlet end of each mixed gas separation device is connected with the oil casing annulus through the corresponding plurality of vent holes 11, that is, the gas located at the second gas outlet end of the mixed gas separation device will flow into the oil casing annulus through the vent holes 11. The converging through hole 12 is located above the mixed gas separation device, and the gas in the oil casing annulus flows into the oil pipe body 2 through the converging through hole 12.

Before the actual operation, the oil pipe body 2 equipped with the gas-liquid separation device and the mixed gas separation device is installed at the lowest end of the oil pipe below, and the lower end of the casing body 1 is also a blind end structure. During operation, the formation gas-liquid mixed phase enters from the liquid inlet pipe 4 and flows into the gas-liquid separation device through the liquid inlet pipe 4. The gas-liquid separation device separates the formation gas-liquid mixed phase into gas and liquid, wherein the gas will be discharged from the gas outlet end of the gas-liquid separation device and flow into the mixed gas separation device located at the lowest level, and the liquid will be injected back into the abandoned bottom layer through the liquid outlet pipe 6 to replenish the bottom formation energy. The gas flowing into the upper part will pass through the mixed gas separation devices in sequence. When entering the first mixed gas separation device, the separated _CO2 will be discharged to the abandoned bottom layer through the gas outlet pipe 10 to replenish the bottom formation energy; and the separated _CH4 will enter the oil-casing annulus, and enter the mixed gas separation device above it along the oil-casing annulus (if there are two or more mixed gas separation devices), and then enter the second mixed gas separation device to perform the mixed gas separation process again. The process is the same as the first time. The separated _CO2 will be discharged through the gas outlet pipe 10, and the separated _CH4 will enter the oil-casing annulus again. After all the mixed gas separation devices have performed the separation work in sequence, the _CH4 in the oil-casing annulus will flow into the upper interior of the oil pipe body 2 through the converging through hole 12, and finally be transported to the outside.

In this embodiment, the gas-liquid separation device is an existing axial flow cyclone 3 (also called a cyclone). The axial flow cyclone 3 is a device for separating gas and liquid based on the theory of centrifugal force difference between gas and liquid. The main components of the axial flow cyclone 3 are a column section and a cone section. The formation gas-liquid mixed phase enters the column section through the liquid inlet pipe 4. The spiral track inside the axial flow cyclone 3 causes the mixture to produce a rotational motion. This rotational motion causes relative motion between the gas and liquid phases, generating centrifugal force. Since the liquid has a larger density, it will be subjected to a greater centrifugal force and move toward the periphery of the axial flow cyclone 3. A liquid ring is formed between the inner wall of the axial flow cyclone 3 and the liquid, which is called a liquid ring. Under the action of the liquid ring, the liquid flows toward the cone section and flows into the bottom of the axial flow cyclone 3, and finally flows out from the bottom flow port. In contrast, the density of the gas is smaller, and the centrifugal force on the gaseous component is relatively small. Therefore, the gas will be relatively concentrated and maintained in the central part of the axial flow cyclone 3 , and move upward, and finally flow out from the overflow port at the upper end of the axial flow cyclone 3 .

In this embodiment, the liquid inlet pipe 4 is fixed obliquely on the side wall of the sleeve body 1, that is, there is an angle between the liquid inlet pipe 4 and the side wall of the sleeve body 1, and the angle is not 90°. The purpose of this setting is to allow the gas-liquid two-phase to be initially separated at the inlet of the axial flow cyclone 3, and then enter the column section of the axial flow cyclone 3, so as to achieve faster separation of the gas-liquid two-phase.

In this embodiment, the lower end of the oil pipe body 2 is a hemispherical structure, a liquid outlet is provided at the center of the hemispherical structure, and a one-way flow control device is provided at the liquid outlet. One end of the liquid outlet pipe 6 is located in the oil casing annulus, and the other end is located outside the casing body 1.

In actual operation, the liquid phase flowing out from the bottom flow port of the axial flow cyclone 3 will flow to the hemispherical structure at the bottom of the oil pipe body 2. When the one-way flow control device is opened, the liquid phase at the lower end of the oil pipe body 2 will flow into the oil casing annulus, and the liquid in the oil casing annulus will eventually flow into the external waste bottom layer through the liquid outlet pipe 6.

In this embodiment, the one-way flow control device is a valve body 5, which can be an existing valve. The specific structure of the valve body 5 in this embodiment is shown in FIG. 4 :

The valve body 5 includes an upper polygonal plate, an intermediate cone and a lower circular plate, wherein the upper polygonal plate is fixed to the upper end of the intermediate cone, and the lower circular plate is fixed to the lower end of the intermediate cone, and the diameter of the intermediate cone gradually decreases from top to bottom. The areas of the upper polygonal plate and the lower circular plate are both larger than the area of the liquid outlet, and the intermediate cone is located at the liquid outlet. Due to the limiting effect of the upper polygonal plate and the lower circular plate, the valve body 5 will never be separated from the liquid outlet.

In actual use, when there is no liquid at the bottom of the oil pipe body 2, the upper end of the middle vertebral body of the valve body 5 can block the liquid outlet due to the effect of its own weight, so that the liquid in the oil pipe body 2 cannot flow out. When the liquid separated by the axial flow cyclone 3 continuously enters the hemispherical structure at the bottom of the oil pipe body 2, the buoyancy of the liquid at the hemispherical structure at the bottom of the oil pipe body 2 will also continue to increase. When the buoyancy of the liquid is greater than the gravity of the valve body 5, the valve body 5 gradually floats up, and a gap appears between the valve body 5 and the liquid outlet, so that the liquid in the oil pipe body 2 flows into the oil casing annulus. As the liquid in the oil pipe body 2 continues to decrease, the valve body 5 will move downward again due to its own weight and block the liquid outlet again.

In this embodiment, two packers 7 are provided between the casing body 1 and the tubing body 2, and the two packers 7 are respectively located at the upper and lower ends of the mixed gas separation device. Specifically, the packer 7 located at the upper end is located above the confluent through hole 12, and the packer 7 located at the lower end is located at the lower end of the mixed gas separation device located at the lowest end. The function of the two packers 7 is to prevent CH ₄ separated by the mixed gas separation device from flowing to other places, and finally can only flow into from the confluent through hole 12.

In this embodiment, the mixed gas separation device is a mixed gas separation membrane 8, and the mixed gas separation membrane 8 is a large-area continuous dense inorganic membrane Zn ₂ BDC ₂ DABCO prepared on the basis of amino-activated porous SiO ₂ (the mixed gas separation membrane 8 is derived from the literature: Preparation and Performance Study of SiO ₂ /APTES/Zn ₂ BDC ₂ DABCO Composite Membrane). The permeation flow rates of CO ₂ and CH ₄ in the mixed gas separation membrane 8 are 1.78×10 ^-2 mol·m ^-2 ·s ^-1 and 1.50×10 ^-3 mol·m ^-2 ·s ^-1 respectively; the permeation flow rate of CO ₂ is one order of magnitude larger than that of methane, so the mixed gas separation membrane 8 can be used to purify CO ₂ in the mixed gas of CO ₂ and CH ₄ .

Each gas outlet pipe 10 is located above the corresponding mixed gas separation membrane 8 , and the vent hole 11 is located above the corresponding mixed gas separation membrane 8 .

When the mixed gas passes through the mixed gas separation membrane 8 from bottom to top, _CO2 can pass through the mixed gas separation membrane 8 and finally be discharged from the corresponding gas outlet pipe 10, while _CH4 cannot pass through the mixed gas separation membrane 8 and is discharged into the oil casing annulus from the vent hole 11 on one side and moves upward along the oil casing annulus. Due to the limiting effect of the two packers 7, the _CH4 in the oil casing annulus finally flows into the confluent through hole 12 and flows out upward along the oil pipe body 2.

In this embodiment, two mixed gas separation devices are provided, and the purpose of providing two is to further purify CH ₄ in CO ₂ to avoid some CH ₄ from being wasted by passing through the first mixed gas separation membrane 8. Of course, for further purification, those skilled in the art may also provide three, four or more mixed gas separation devices.

In this embodiment, a partition plate 9 is provided above each mixed gas separation device, and the partition plate 9 is fixed inside the oil pipe body 2. Since there are two mixed gas separation membranes 8 in total, two partition plates 9 are also provided. The partition plate 9 can prevent the CO ₂ passing through the mixed gas separation membrane 8 from flowing upward, thereby ensuring that the CO ₂ can only flow out along the outlet pipe 10.

In this embodiment, as shown in FIG. 5 , the mixed gas separation membrane 8 is an arc surface structure, the purpose of which is to increase the contact area between the mixed gas separation membrane 8 and the mixed gas, thereby improving the separation effect of the mixed gas.

The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims (8)

1. A downhole multiphase separation device for injection and production in the same well, characterized in that it comprises a casing body (1), an oil pipe body (2), a gas-liquid separation device and a plurality of mixed gas separation devices, the oil pipe body (2) being arranged inside the casing body (1), an oil-casing annulus being formed between the casing body (1) and the oil pipe body (2), the gas-liquid separation device and the plurality of mixed gas separation devices being arranged inside the oil pipe body (2), the gas-liquid separation device being located below the mixed gas separation device, a liquid inlet pipe (4), a liquid outlet pipe (6) and a plurality of gas outlet pipes (10) being provided on the side wall of the casing body (1), one end of the liquid inlet pipe (4) being located outside the casing body (1), the other end of the liquid inlet pipe (4) being connected to the liquid inlet end of the gas-liquid separation device, and the liquid flowing out of the liquid outlet end of the gas-liquid separation device can enter the liquid outlet pipe (6), one end of the liquid outlet pipe (6) away from the gas-liquid separation device is located outside the casing body (1), the gas separated by the gas-liquid separation device flows to the mixed gas separation device located at the bottom, and the liquid separated by the gas-liquid separation device flows out through the liquid outlet pipe (6), one end of the gas outlet pipe (10) is connected to the first gas outlet end of the mixed gas separation device, a plurality of vents (11) and a merging through hole (12) are provided on the side wall of the oil pipe body (2), the second gas outlet end of each mixed gas separation device is connected to the oil casing annulus through the corresponding vent (11), the merging through hole (12) is located above the mixed gas separation device, and the gas in the oil casing annulus flows into the oil pipe body (2) through the merging through hole (12); The lower end of the oil pipe body (2) is a hemispherical structure, a liquid outlet is provided at the center of the hemispherical structure, and a one-way flow control device is provided at the liquid outlet; The one-way flow control device is a valve body (5); The valve body includes an upper polygonal plate, an intermediate cone and a lower circular plate. The upper polygonal plate is fixed to the upper end of the intermediate cone, and the lower circular plate is fixed to the lower end of the intermediate cone. The areas of the upper polygonal plate and the lower circular plate are both larger than the area of the liquid outlet, and the intermediate cone is located at the liquid outlet. 2. The downhole multiphase separation device for injection and production in the same well according to claim 1, characterized in that: the gas-liquid separation device is an axial flow cyclone (3). 3. The downhole multiphase separation device for injection and production in the same well according to claim 1, characterized in that: the liquid inlet pipe (4) is fixed obliquely on the side wall of the casing body (1). 4. The downhole multiphase separation device for injection and production in the same well according to claim 1 is characterized in that two packers (7) are arranged between the casing body (1) and the oil pipe body (2), and the two packers (7) are respectively located at the upper and lower ends of the mixed gas separation device. 5. The downhole multiphase separation device for injection and production in the same well according to claim 1, characterized in that: the mixed gas separation device is a mixed gas separation membrane (8). 6. The downhole multiphase separation device for injection and production in the same well according to claim 5, characterized in that: two mixed gas separation devices are provided. 7. The downhole multiphase separation device for injection and production in the same well according to claim 5, characterized in that a partition plate (9) is provided above each of the mixed gas separation devices, and the partition plate (9) is fixed inside the oil pipe body (2). 8. The downhole multiphase separation device for injection and production in the same well according to claim 5, characterized in that the mixed gas separation membrane (8) is a circular arc surface structure.