A stable gathering and transportation system and method for oilfield salt crystal produced fluid

Abstract

The present invention relates to a stable collection and transportation system and method for produced liquid containing salt crystals in an oil field. The stable collection and transportation system for produced liquid containing salt crystals in an oil field comprises a piston cylinder, a piston, a one-way valve, a centrifuge, a connecting pipe and a joint station. The side wall of the piston cylinder is connected to the produced liquid output port of the oil well Christmas tree through a connecting pipe with a one-way valve; a liquid outlet is provided at the bottom of the piston cylinder, and the liquid outlet is connected to the inlet of a centrifuge with a refrigeration function through a liquid pipeline; the piston is arranged in the piston cylinder cavity and is connected to a piston connecting rod, which extends from the upper end of the piston cylinder and can drive the piston to move up and down to open or block the liquid outlet, thereby pushing the fluid in the piston cylinder to flow to the centrifuge; the centrifuge outlet is connected to the pipeline to the joint station through a pipeline, the joint station is connected to a water-containing crude oil storage tank through a pipeline, the water-containing crude oil storage tank is connected to a finished crude oil tank and a water tank respectively, and the sewage tank is connected to a sewage treatment system and a water evaporation device in sequence through a pipeline.

Description

Technical Field

[0001] The present invention relates to the technical field of oil fields, and in particular to a stable gathering and transportation system and method for oil field salt-containing crystal produced fluid. Background Art

[0002] Due to the limitations of reservoir characteristics, the concentration of sodium carbonate and sodium bicarbonate in the produced water of a certain oil field is too high, reaching 13% to 25%, and the total mineralization is 250,000 to 450,000 mg / L. After the produced fluid is lifted from the oil well to the surface, the dissolved salt in the produced water will precipitate due to changes in its existence state, causing pipeline blockage due to salt crystallization, which seriously affects the development of the oil field.

[0003] To address this issue, appropriate methods are needed to inhibit the crystallization of sodium bicarbonate and sodium carbonate at the wellhead. Common methods for inhibiting crystallization include: 1. Reducing the salt concentration below saturation; 2. Adding salt crystallization inhibitors to prevent salt crystal precipitation; 3. Raising the temperature to increase salt solubility. These methods are difficult to implement due to the impact of wellhead desalination on the technical system. Summary of the Invention

[0004] In order to solve one or more technical problems existing in the prior art, the present invention provides a stable gathering and transportation system and method for oilfield salt crystal produced fluid.

[0005] The technical solution of the present invention for solving the above-mentioned technical problems is as follows: A stable gathering and transportation system for produced liquid from salt-containing crystals in an oil field, comprising a piston cylinder, a piston, a one-way valve, a centrifuge, a connecting pipe and a joint station, wherein the side wall of the piston cylinder is connected to the produced liquid output port of the oil well Christmas tree through a connecting pipe with a one-way valve; a liquid outlet is provided at the bottom of the piston cylinder, and the liquid outlet is connected to the inlet of a centrifuge with a refrigeration function through a liquid pipeline; the piston is arranged in the cavity of the piston cylinder and is connected to a piston connecting rod, the piston connecting rod extends from the upper end of the piston cylinder and can drive the piston to move up and down to open or block the liquid outlet, thereby pushing the fluid in the piston cylinder to flow to the centrifuge; the outlet of the centrifuge is connected and communicated with the pipeline to the joint station through a pipeline, the joint station is connected to a water-containing crude oil storage tank through a pipeline, the water-containing crude oil storage tank is connected and communicated with a finished crude oil tank and a water tank respectively, the sewage tank is connected to a sewage treatment system through a pipeline, and the water outlet of the sewage treatment system is connected and communicated with a water evaporation device.

[0006] The present invention has the following beneficial effects: A system and method for stably collecting and transporting produced fluid containing salt crystals from an oilfield is provided. The pumping unit ascends to lift the oil-water mixture at the bottom of the oil well to the surface. After the water-containing crude oil is extracted at the wellhead, a one-way valve installed on a pipe connected to the production fluid outlet of the Christmas tree opens, allowing produced fluid to enter the piston cylinder through the connecting pipe. Driven upward by the piston connecting rod, the piston in the piston cylinder moves upward, leaving space for the solid-liquid mixture extracted from the oil well to enter the piston cylinder smoothly. When the pumping unit descends (without lifting the oil-water mixture in the oil well), the piston, driven downward by the piston connecting rod, pushes the produced fluid that has entered the piston cylinder into a centrifuge with a refrigeration function. As the piston advances into the centrifuge, the one-way valve closes, preventing the oil-water mixture in the piston cylinder from re-entering the oil well through the connecting pipe. The centrifuge can be used to separate salt crystals from the oil-water mixture, eliminating the impact of salt crystals on the stability of produced fluid collection and transportation, thereby achieving stable and continuous collection and transportation of oilfield produced fluid. After the produced liquid is separated into solid and liquid by a centrifuge, the separated liquid is added with a salt crystallization inhibitor and then enters the pipeline to the joint station for subsequent oil-water separation, water treatment and slag treatment.

[0007] On the basis of the above technical solution, the present invention can also be improved as follows.

[0008] Furthermore, the centrifuge is located directly below the piston cylinder.

[0009] The beneficial effect of adopting the above further solution is that the centrifuge is arranged directly below the piston cylinder, so that the oil-water mixture in the piston cylinder can smoothly enter the centrifuge.

[0010] Furthermore, the piston-cylinder body is arranged side by side with the oil well Christmas tree, and the inner cavity volume of the piston-cylinder body is 1.2 to 1.5 times the rated flow rate of the pumping unit.

[0011] The beneficial effect of adopting the above further solution is: providing sufficient accommodation space for each fluid lift, thereby preventing the fluid from flowing back each time it is lifted.

[0012] Furthermore, the one-way valve is an interlocking one-way valve.

[0013] Furthermore, the connecting pipe is arranged near the upper end of the piston cylinder; the connecting pipe is arranged horizontally or inclined; when the connecting pipe is arranged inclined, the end of the connecting pipe connected to the piston cylinder is lower than the end of the connecting pipe connected to the oil well Christmas tree.

[0014] Furthermore, the outer diameter of the piston is smaller than the inner diameter of the piston cylinder; an upper sealing gasket is provided on the upper end surface of the piston, and a lower sealing gasket is provided on the lower end surface of the piston; the piston connecting rod is movably connected to the upper end of the piston cylinder in a sealing manner.

[0015] The beneficial effect of adopting the above further solution is to prevent salt from precipitating between the piston circumference and the piston cylinder body, which may affect the normal use of the piston. By providing sealing gaskets on both the upper end face and the lower end face of the piston, the sealing contact between the piston and the piston cylinder body is facilitated.

[0016] A method for stably collecting and transporting oilfield produced fluids is implemented using the above-mentioned system for stably collecting and transporting oilfield salt crystal produced fluids, and includes the following steps:

[0017] S1: When the produced fluid is lifted upward from the oil well through the pumping unit, the one-way valve opens, and the produced fluid enters the piston cylinder through the connecting pipe with the one-way valve. When the produced fluid enters the piston cylinder, the piston moves upward under the drive of the piston connecting rod, and the produced fluid smoothly enters the space below the piston; when the pumping unit descends, the one-way valve closes, and the piston moves downward under the drive of the piston connecting rod, pushing the produced fluid in the piston cylinder into the centrifuge;

[0018] S2, after the produced liquid is cooled and solid-liquid separated in a centrifuge, the separated liquid is added with a salt crystallization inhibitor and then enters the water-containing crude oil tank of the joint station. In the water-containing crude oil tank, it is mixed with an emulsifier and then separated into oil and water. The separated crude oil enters the finished crude oil storage tank. The separated produced water is flocculated and filtered before entering the water evaporation equipment for evaporation and concentration;

[0019] S3, the waste salt generated after the evaporation of the produced water is mixed with the solid salt residue separated by the centrifuge and then enters the waste salt calcination equipment for calcination to form sodium carbonate crude salt, which can be used as a material for tertiary oil recovery liquid or a raw material for solid fire extinguishing agent; the water phase generated by the evaporation of the produced water is recycled after treatment.

[0020] The beneficial effects of the present invention are as follows: the oilfield produced fluid stable collection and transportation method of the present invention can realize the stable and continuous collection and transportation of oil well produced fluid, and can perform subsequent treatment on the produced fluid to realize oil-water separation and the recycling of slag salt and water phase.

[0021] Furthermore, the concentration of the salt crystallization inhibitor is 50-300 mg / L.

[0022] Furthermore, in S2, the flocculants used for flocculation of produced water are PAC and PAM, the addition amount of PAC is 200~400 mg / L, the addition amount of PAM is 5~15 mg / L, the cationic degree of PAM is 5%~25%, and the molecular weight range of PAM is 8 million~16 million.

[0023] Furthermore, in S2, the filter used for produced water filtration includes a three-stage filter composed of 0.3-0.5 mm granular quartz sand, modified fiber balls and an ultrafiltration filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1This is a schematic diagram of the structural principle of the oilfield salt crystal produced fluid stable gathering and transportation system of the present invention;

[0025] Figure 2 The figure is a schematic diagram of the process flow of the stable gathering and transportation system of the oilfield salt crystal produced fluid according to the present invention.

[0026] In the accompanying drawings, the components represented by the reference numerals are as follows:

[0027] 1. Piston cylinder; 11. Infusion tube; 2. Piston; 21. Piston connecting rod; 3. One-way valve; 4. Centrifuge; 5. Connecting pipe; 6. Sucker rod; 7. Oil well Christmas tree; 8. Pumping unit. DETAILED DESCRIPTION

[0028] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0029] like Figure 1 As shown, a stable collection and transportation system for produced liquid from salt crystals in an oil field in this embodiment includes a piston cylinder 1, a piston 2, a one-way valve 3, a centrifuge 4, a connecting pipe 5 and a joint station. The side wall of the piston cylinder 1 is connected to the produced liquid output port of the oil well Christmas tree through the connecting pipe 5, and the connecting pipe 5 is provided with a one-way valve 3; the bottom of the piston cylinder 1 is provided with a liquid outlet, and the liquid outlet is connected to the inlet of the centrifuge 4 with a refrigeration function through a liquid pipeline. The piston 2 is arranged in the cavity of the piston cylinder 1 and is connected to a piston connecting rod 21, the piston connecting rod 21 extends from the upper end of the piston cylinder 1 and can drive the piston 2 to move up and down to open or block the liquid outlet, pushing the fluid in the piston cylinder 1 to flow to the centrifuge 4; the outlet of the centrifuge 4 is connected to and communicated with the pipeline to the joint station through a pipeline, and the joint station is connected to the water-containing crude oil storage tank through pipelines, and the water-containing crude oil storage tank is connected to and communicated with the finished crude oil tank and the water tank respectively. The sewage tank is connected to the sewage treatment system through a pipeline, and the water outlet of the sewage treatment system is connected to and communicated with the water evaporation equipment.

[0030] like Figure 1 As shown, a preferred solution of this embodiment is that the centrifuge 4 is located directly below the piston cylinder 1. By arranging the centrifuge directly below the piston cylinder, the oil-water mixture in the piston cylinder can be smoothly introduced into the centrifuge.

[0031] like Figure 1 As shown, a preferred solution of this embodiment is that the outer diameter of the piston 2 is smaller than the inner diameter of the piston cylinder 1. This prevents salt from precipitating between the piston periphery and the piston cylinder and affecting the normal use of the piston.

[0032] Preferably, the one-way valve 3 is an interlocking one-way valve.

[0033] Optional, such as Figure 1 As shown, the connecting pipe 5 is arranged horizontally or tilted; when the connecting pipe 5 is tilted, the end of the connecting pipe 5 connected to the piston cylinder 1 is lower than the end of the connecting pipe 5 connected to the oil well Christmas tree 7.

[0034] like Figure 1 As shown, specifically, the connecting pipe 5 is arranged near the upper end of the piston cylinder 1.

[0035] Preferably, in this embodiment, the piston 2 is provided with an upper sealing gasket on its upper end surface, and a lower sealing gasket on its lower end surface. Both the upper and lower sealing gaskets may be made of fluororubber. The piston connecting rod 21 is in a sealing and movable connection with the upper end of the piston cylinder 1. Providing sealing gaskets on both the upper and lower end surfaces of the piston facilitates the sealed contact between the piston and the cylinder. Both the upper and lower sealing gaskets are annular.

[0036] In this embodiment, a Christmas tree 7 of the oil well is provided with a sucker rod 6 and a pumping unit 8. The pumping unit 8 is in transmission connection with the sucker rod 6. The sucker rod 6 is arranged in the Christmas tree 7 of the oil well. The sucker rod 6 is mechanically driven by a pump to lift the fluid (produced liquid) in the oil well upward to the connecting pipe 5 through the produced liquid outlet connected to the Christmas tree 7 of the oil well.

[0037] like Figure 1 As shown, the piston-cylinder 1 of this embodiment is arranged side by side with the oil well Christmas tree 7. The internal volume of the piston-cylinder 1 is 1.2 to 1.5 times the rated flow rate of the pumping unit 8 (the rated flow rate of the oil skimmer). This provides sufficient space for each fluid lift and prevents backflow of the fluid during each lift.

[0038] Specifically, in this embodiment, the piston connecting rod 21 can be connected to a drive device consisting of a motor and a reducer. When the sucker rod 6 is electrically driven upward by the pumping unit 8 (motor + reducer), the piston connecting rod 21 drives the piston 2 to move rapidly upward to the uppermost end of the piston cylinder 1, leaving space for the oil well fluid to enter the cavity of the piston cylinder 1. The electric drive device driving the piston connecting rod 21 operates intermittently, that is, it moves rapidly upward when the sucker rod is raised and rapidly downward when the sucker rod is lowered, pushing the fluid in the cavity of the piston cylinder 1 into the centrifuge 4. The cavity of the piston cylinder 1 where the piston 2 is located is a circular cavity. The volume of the circular cavity is related to the model of the pumping unit 8 and is generally 1.2 to 1.5 times the rated flow rate of the pumping unit 8.

[0039] Preferably, the centrifuge 4 is a low-temperature refrigerated centrifuge. The bottom of the piston cylinder 1 is connected to the top of the centrifuge 4 through an infusion tube 11.

[0040] In the stable collection and transportation system for produced fluid containing salt crystals in the oil field of the present embodiment, the pumping unit drives the sucker rod upward to lift the oil-water mixture at the bottom of the oil well to the ground. After the water-containing crude oil is produced at the wellhead of the oil well, the one-way valve provided on the pipe connected to the produced fluid external transmission port of the oil tree is opened, and the produced fluid enters the piston cylinder through the connecting pipe. The piston in the piston cylinder moves upward under the drive of the piston connecting rod, leaving space for the solid-liquid mixture produced from the oil well to enter the piston cylinder smoothly. When the pumping unit drives the oil pump downward (without lifting the oil-water mixture in the oil well), the piston is pushed downward by the piston connecting rod to push the produced fluid from the oil well into a centrifuge with a refrigeration function. During the process of the piston advancing into the centrifuge, the one-way valve closes, preventing the oil-water mixture in the piston cylinder from re-entering the oil well through the connecting pipe. A centrifuge with a refrigeration function can be used to cool the oil-water mixture and rapidly form salt crystals in the produced fluid. Salt crystals are then separated from the oil-water mixture under the action of the centrifuge, eliminating the impact of salt crystals on the stability of produced fluid collection and transportation. The centrifuge with a refrigeration function can reduce the produced fluid temperature from approximately 60-65°C to 35-40°C. The stable oilfield produced fluid collection and transportation device of this embodiment, by providing a piston cylinder, a piston, a one-way valve, a centrifuge, and a connecting pipe, can use a centrifuge to separate salt crystals from the oil-water mixture, eliminating failures in the produced fluid collection and transportation system caused by salt crystals clogging the pipeline, thereby achieving stable and continuous collection and transportation of oilfield produced fluid. After the produced fluid is separated into solid and liquid by the centrifuge, the separated liquid, after adding a certain concentration of salt crystallization inhibitor, enters the pipeline to the joint station for subsequent oil-water separation, water treatment, and slag treatment.

[0041] like Figure 2 As shown, this embodiment also provides a method for stable collection and transportation of oilfield produced fluid, which is implemented using the above-mentioned oilfield salt crystal produced fluid stable collection and transportation system, and includes the following steps:

[0042] S1, when the produced fluid is lifted from the oil well by the pumping unit 8, the one-way valve 3 is opened, and the produced fluid enters the piston cylinder 1 through the connecting pipe 5 with the one-way valve 3. When the produced fluid enters the piston cylinder 1, the piston 2 moves upward under the drive of the piston connecting rod 21, and the produced fluid smoothly enters the space below the piston 2. When the pumping unit 8 descends, the one-way valve 3 is closed, and the piston 2 moves downward under the drive of the piston connecting rod 21, pushing the produced fluid in the piston cylinder 1 into the centrifuge 4.

[0043] In step S2, the produced fluid passes through centrifuge 4 for cooling and solid-liquid separation. A certain concentration of salt crystallization inhibitor is then added to the separated liquid before entering the combined station's water-containing crude oil tank. There, it is mixed with a demulsifier for oil-water separation. The separated crude oil (with a water content of less than 0.5%) enters the crude oil storage tank. The separated produced water undergoes flocculation and filtration before entering a water evaporation unit for evaporation and concentration. The salt crystallization inhibitor concentration is 50-300 mg / L. The flocculants used for produced water flocculation are PAC and PAM. The PAC dosage is 200-400 mg / L, and the PAM dosage is 5-15 mg / L. The cationicity of PAM is 5%-25%, and the molecular weight of PAM ranges from 8 to 16 million. The produced water filtration system includes a three-stage filter consisting of 0.3-0.5 mm quartz sand, modified fiber balls, and an ultrafiltration filter.

[0044] S3, the waste salt generated after the evaporation of the produced water is mixed with the solid salt residue separated by the centrifuge 4, and then enters the waste salt calcination equipment and is calcined at 650°C~780°C to form sodium carbonate crude salt, which can be used as a material for tertiary oil recovery liquid preparation or a raw material for solid fire extinguishing agent; the water phase generated by the evaporation of the produced water is recycled after treatment; specifically, the sodium carbonate crude salt is used as a material for tertiary oil recovery liquid preparation and a raw material for solid fire extinguishing agent.

[0045] In this embodiment, demulsifiers are added at a joint station. The primary function of a joint station is to separate the four phases of oil, water, gas, and solids. Therefore, each station has dedicated space and equipment for adding demulsifiers, following the same demulsifier addition process as existing oilfield joint stations. Water-containing crude oil enters the joint station and, under the action of the added demulsifier, undergoes oil-water separation in a settling tank. The dehydrated crude oil is then pumped to a finished crude oil storage tank. The separated oily wastewater enters the oily wastewater treatment system.

[0046] After the water phase mineralization of the evaporated water is reduced to below 1000 mg / L, the suspended solids content is reduced to 5.0 mg / L, and the oil content is reduced to below 8.0 mg / L, it can be used to reinject the reservoir or as condensate during the evaporation of waste brine. The resulting slag salt, when added at a dosage of 1% to 5% and sodium petroleum sulfonate at 0.3% to 0.7%, constitutes a liquid preparation material for tertiary oil recovery. The resulting slag salt, when added at a dosage of 25% to 35%, potassium bicarbonate at 30% to 35%, and potassium phosphate as the remainder, constitutes a solid fire extinguishing material for firefighting.

[0047] A specific solution of this embodiment is described, taking an oilfield block as an example: produced fluid from an oil well is pushed by a powered piston in a piston cylinder into a centrifuge with a cooling function (the cooling temperature is 60-65°C for the produced fluid, which can be reduced to 35-40°C in the centrifuge). After being processed at 2000-2500 rpm for 5-10 minutes, the residue enters a temporary storage area. After adding a salt crystallization inhibitor synthesized from polyvinylamine-halogenated polyol at a dosage of 50-300 mg / L, the oil-water mixture is pumped to a combined station. After demulsification by adding 100-300 mg / L of a demulsifier using an alkylphenol-formaldehyde resin as an initiator and an ethylene oxide-propylene oxide block copolymer with a molecular weight of 5000-7000 Daltons, the water content of the crude oil is reduced to below 0.5% and enters the finished crude oil tank. The separated aqueous phase is added with PAC and PAM (the amount is as mentioned above) and filtered, and then enters a three-stage evaporation device. The solid phase component obtained after the evaporated concentrate is cooled is mixed with the slag produced by solid-liquid separation, and is calcined at 650-780°C for 40-90 minutes to form slag salt. After the mineralization of the evaporated water phase is reduced to below 1000 mg / L, and the suspended matter content and oil content are reduced to below 5.0 mg / L and 8.0 mg / L respectively, it is used for reinjection into the reservoir or for condensate water in the evaporation process of waste brine. The obtained slag salt constitutes a material for tertiary oil recovery when the addition amount is 1%-5% and the addition amount of sodium petroleum sulfonate is 0.3-0.7%; the slag salt constitutes a solid fire extinguishing material for fire extinguishing when the addition amount is 25%-35%, the addition amount of potassium bicarbonate is 30-35%, and the addition amount of potassium phosphate is the remainder.

[0048] The stable collection and transportation method of oilfield salt crystal produced fluid of this embodiment can realize stable and continuous collection and transportation of oil well produced fluid, and can perform subsequent treatment on the produced fluid to realize oil-water separation and recycling of slag salt and water phase.

[0049] In the description of the present invention, it should be understood that the terms "lateral", "upper", "lower", "inner", "outer", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are 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 cannot be understood as a limitation on the present invention.

[0050] In the present invention, unless otherwise specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediate medium; internal communication between two elements, or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0051] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0052] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0053] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for stable collection and transportation of produced fluid containing salt crystals in oil fields, characterized in that: The invention adopts a stable collection and transportation system for produced liquid of salt crystals in oil fields, which comprises a piston cylinder, a piston, a one-way valve, a centrifuge, a connecting pipe and a joint station. The side wall of the piston cylinder is connected to the produced liquid output port of the oil well Christmas tree through a connecting pipe with a one-way valve; a liquid outlet is provided at the bottom of the piston cylinder, and the liquid outlet is connected to the inlet of a centrifuge with a refrigeration function through a liquid pipeline; the piston is arranged in the cavity of the piston cylinder and is connected to a piston connecting rod, which extends from the upper end of the piston cylinder and can drive the piston to move up and down to open or block the liquid outlet, thereby pushing the fluid in the piston cylinder to flow to the centrifuge; the outlet of the centrifuge is connected and communicated with the pipeline to the joint station through a pipeline, the joint station is connected to a water-containing crude oil storage tank through a pipeline, the water-containing crude oil storage tank is connected and communicated with the finished crude oil tank and the water tank respectively, the sewage tank is connected to the sewage treatment system through a pipeline, and the water outlet of the sewage treatment system is connected and communicated with the water evaporation equipment; The method for stably gathering and transporting produced fluid containing salt crystals in oil fields comprises the following steps: S1: When the produced fluid is lifted upward from the oil well through the pumping unit, the one-way valve opens, and the produced fluid enters the piston cylinder through the connecting pipe with the one-way valve. When the produced fluid enters the piston cylinder, the piston moves upward under the drive of the piston connecting rod, and the produced fluid smoothly enters the space below the piston; when the pumping unit descends, the one-way valve closes, and the piston moves downward under the drive of the piston connecting rod, pushing the produced fluid in the piston cylinder into the centrifuge; S2, after the produced liquid is cooled and solid-liquid separated in a centrifuge, the separated liquid is added with a salt crystallization inhibitor and then enters the water-containing crude oil tank of the joint station. In the water-containing crude oil tank, it is mixed with an emulsifier and then separated into oil and water. The separated crude oil enters the finished crude oil storage tank. The separated produced water is flocculated and filtered before entering the water evaporation equipment for evaporation and concentration; S3, the waste salt generated after the evaporation of the produced water is mixed with the solid salt residue separated by the centrifuge and then enters the waste salt calcination equipment for calcination to form sodium carbonate crude salt, which is used as a material for tertiary oil recovery liquid or a raw material for solid fire extinguishing agent; the water phase generated by the evaporation of the produced water is recycled after treatment.

2. The method for stable collection and transportation of produced fluid containing salt crystals in oil fields according to claim 1, characterized in that: The centrifuge is located directly below the piston cylinder.

3. The method for stable collection and transportation of produced salt crystals from oil fields according to claim 1, characterized in that: The piston cylinder is arranged side by side with the oil well Christmas tree, and the inner cavity volume of the piston cylinder is 1.2 to 1.5 times the rated flow of the pumping unit.

4. The method for stable collection and transportation of produced fluid containing salt crystals in oil fields according to claim 1, characterized in that: The one-way valve is an interlocking one-way valve.

5. The method for stable collection and transportation of produced fluid containing salt crystals in oil fields according to claim 1, characterized in that: The connecting pipe is arranged near the upper end of the piston cylinder; the connecting pipe is arranged horizontally or inclined; when the connecting pipe is arranged inclined, the end of the connecting pipe connected to the piston cylinder is lower than the end of the connecting pipe connected to the oil well Christmas tree.

6. The method for stably collecting and transporting produced fluid containing salt crystals in oil fields according to claim 1, characterized in that: The outer diameter of the piston is smaller than the inner diameter of the piston cylinder; an upper sealing gasket is provided on the upper end surface of the piston, and a lower sealing gasket is provided on the lower end surface of the piston; the piston connecting rod is movably connected to the upper end of the piston cylinder in a sealed manner.

7. The method for stably collecting and transporting produced fluid containing salt crystals in oil fields according to claim 1, characterized in that: The concentration of the salt crystallization inhibitor is 50-300 mg / L.

8. The method for stably collecting and transporting produced fluid containing salt crystals in oil fields according to claim 1, characterized in that: In S2, the flocculants used for produced water flocculation are PAC and PAM. The addition amount of PAC is 200~400 mg / L, the addition amount of PAM is 5~15 mg / L, the cationic degree of PAM is 5%~25%, and the molecular weight range of PAM is 8~16 million.

9. The method for stable collection and transportation of produced fluid containing salt crystals in oil fields according to claim 1, characterized in that: In S2, the filter used for produced water filtration includes a three-stage filter consisting of 0.3~0.5mm particle quartz sand, modified fiber balls and ultrafiltration filter.

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