A double-tower shale oil crude stabilizer

Abstract

A dual-tower shale oil stabilization device relates to the field of oilfield purified shale oil stabilization technology. It includes a stabilization tank with two flash towers arranged side-by-side at the top. The middle of each flash tower is connected to the purified shale oil inlet. Each flash tower has a spray plate connected to the liquid inlet. Packing material is located below the spray plate, and a wire mesh demister is located above it. The top of each flash tower is connected to a negative pressure screw compressor, which has an outlet for flash-evaporized associated gas. A sieve-plate liquid distribution plate is located inside the stabilization tank. A stripping gas inlet is located on one side of the upper part of the stabilization tank. A sludge outlet and a stabilized shale oil outlet are located at the bottom of the stabilization tank. This invention combines the effects of gas stripping and negative pressure flash stabilization on crude oil stabilization, enabling short-process, skid-mounted processing of purified shale oil, avoiding safety risks and oil and gas losses during transportation, and achieving efficient and stable shale oil processing.

Description

Technical Field

[0001] This invention relates to the field of oilfield purification and shale oil stabilization technology, specifically to a dual-tower shale oil crude oil stabilization device. Background Technology

[0002] In the early stages of shale oil development, some shale oil wells or well groups are located far from existing pipeline networks or stations, making it difficult to connect them to existing integrated stations for dehydration treatment. Furthermore, shale oil is extracted using fracturing, resulting in produced fluids containing large amounts of fracturing flowback fluid in the initial stages of well operation, which is challenging to process. Additionally, shale oil in some blocks has smaller particle size, higher interfacial film pressure, and higher emulsification than conventional crude oil, making dehydration difficult. Directly supplying it to existing integrated stations would completely paralyze the station's gathering, transportation, and processing systems. Therefore, considering these challenges in shale oil development and production, some shale oil blocks utilize high-efficiency dehydration equipment to process the oil on-site into purified oil before transporting it to existing stations, unloading it into purified oil tanks, or selling it directly. However, the purified shale oil after dehydration is unstabilized crude oil, which does not meet the requirement of "Crude Oil" (GB 36170-2018) for a saturated vapor pressure of ≤66.7 kPa for transported crude oil. Therefore, the dehydrated shale oil needs to be stabilized to ensure that the purified shale oil does not escape during transportation and to reduce safety and environmental risks during transportation.

[0003] Conventional crude oil stabilization systems have long processes and many pieces of equipment, making them unsuitable for the stabilization needs of small-area shale oil well sites. Such shale oil well sites often have the following requirements for stabilization process design: (1) skid-mounted, modular, intensive, and easy to relocate; (2) large fluctuation range of shale oil production and high flexibility in equipment operation; (3) reduce the site area and lower investment in ground construction projects.

[0004] The purified oil separated from the wellhead produced fluid by the front-end dehydration process needs to be processed into stable crude oil with saturated vapor pressure that meets the transportation requirements. There are three commonly used crude oil stabilization processes: negative pressure crude oil stabilization process, slightly positive pressure crude oil stabilization process, and fractionation process. However, the conventional crude oil stabilization process is relatively complex, with a large number of auxiliary equipment, high management difficulty, high cost of the whole set of equipment, and large footprint.

[0005] Therefore, for shale oil in independent blocks (well sites) that need to be stabilized before being transported and sold, a shale oil stabilization device with simplified process, reliable equipment, high operational flexibility, and easy relocation needs to be designed. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of this invention is to provide a dual-tower shale oil crude oil stabilization device, which can solve the problems of relatively complex conventional crude oil stabilization processes, a large number of auxiliary equipment, high management difficulty, high cost of the whole set of equipment, and large footprint.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A dual-tower shale oil crude oil stabilization device includes a stabilization tank with two flash towers arranged side-by-side on the top. The middle of each flash tower is connected to the inlet of purified shale oil. Inside each flash tower is a double-layered spray plate connected to the inlet. The upper layer of the spray plate consists of spray heads with an arc-shaped lower surface and circular spray nozzles. The lower layer of the spray plate consists of a herringbone-shaped collision plate. Packing material is located below the spray plate, and baffles and a wire mesh demister are located above it. Removable flanges are installed on the tower walls above the wire mesh demister and below the spray plate. The top of the flash tower is connected to a negative pressure screw compressor, and the negative pressure screw compressor is connected to a flash-generated associated gas outlet. Both the flash-generated associated gas outlet and the flash tower are connected to an air vent outlet. The stabilizing tank is equipped with a sieve-plate liquid distribution plate. A gas stripping inlet is provided on one side of the upper part of the stabilizing tank. The gas stripping inlet is connected to a gas distribution pipeline, which is located between two layers of sieve-plate liquid distribution plates and consists of three gas distribution branch pipes. Double rows of 45° downward gas distribution holes are evenly arranged on the gas distribution branch pipes. The bottom of the stabilizing tank is equipped with a sludge discharge outlet and a stabilized shale oil outlet.

[0008] Preferably, the negative pressure screw compressor is a water-cooled screw compressor, and the water-cooled screw compressor is connected to a cooling water inlet.

[0009] Preferably, the flash tower is equipped with a container safety valve, and the associated gas outlet of the flash is equipped with a compressor outlet safety valve.

[0010] Preferably, the pipeline at the gas lift inlet is equipped with a vortex flow meter and an electric regulating valve for the gas lift.

[0011] Preferably, a booster pump is installed on the pipeline at the outlet of the stabilized shale oil; the stabilization tank is equipped with a local magnetic level gauge and a remote dual-flange level gauge, and the remote dual-flange level gauge is interlocked with the booster pump.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention combines the effects of gas stripping and negative pressure stabilizing flash evaporation on crude oil stabilization, and can realize short-process, skid-mounted processing of purified shale oil, avoiding safety risks and oil and gas losses during the transportation of purified shale oil, and achieving efficient and stable processing of shale oil. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0014] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the spray disc structure of the present invention; Figure 3 This is a schematic diagram of the gas distribution pipeline structure of the present invention.

[0015] Explanation of reference numerals in the attached figures: 1-Stabilizing tank, 2-Flash tower, 3-Spray tray, 4-Packing, 5-Wire mesh demister, 6-Sieve plate liquid distribution tray, 7-Local magnetic level gauge, 8-Remote double flange level gauge, 9-Negative pressure screw compressor, 10-Lift pump, 11-Swirl flow meter, 12-Gas stripping gas electric regulating valve, 13-Container safety valve, 14-Compressor outlet safety valve, 15-Purified shale oil inlet, 16-Stabilized shale oil outlet, 17-Flash evaporation associated gas outlet, 18-Gas stripping gas inlet, 19-Vent air outlet, 20-Sewage outlet, 21-Cooling water inlet, 22-Flange, 23-Baffle plate, 24-Gas distribution pipe, 25-Spray head, 26-Spray nozzle, 27-Collision plate, 28-Gas distribution hole. Detailed Implementation

[0016] The invention will now be described in detail with reference to the accompanying drawings, by way of example. Obviously, the described embodiments are only some embodiments of the invention, and not all embodiments.

[0017] like Figures 1 to 3As shown, this invention discloses a dual-tower shale oil crude oil stabilization device, including a stabilization tank 1. Two flash towers 2 are installed at the top of the stabilization tank 1. The middle of each flash tower 2 is connected to the purified shale oil inlet 15. A double-layer spray plate 3 is installed inside each flash tower 2 and connected to the liquid inlet. The upper layer of the double-layer spray plate 3 is a spray head 25, the lower surface of which is arc-shaped and has a circular spray nozzle 26 to ensure uniform spraying and atomization. A herringbone-shaped collision plate 27 is installed at the lower layer of the spray plate 3 to facilitate gas-liquid separation during spraying. The sprayed liquid flows onto the packing 4 installed at the bottom of the flash tower 2. A baffle 23 and a wire mesh demister 5 are installed above the spray plate 3. The tower wall of the flash tower 2 has removable baffles above the wire mesh demister 5 and below the spray plate 3. The liquid phase of the flash tower 2 is connected to the negative pressure screw compressor 9 through the baffle plate 23 and the wire mesh demister 5. The liquid flowing down through the packing 4 flows to the sieve plate liquid distribution plate 6 at the top of the stabilizer tank 1. The gas distribution pipe 24, which is connected through the gas lift inlet 18, adopts a three-pipe design. Each gas distribution branch pipe is equipped with double rows of downward 45° gas distribution holes 28. The gas distribution pipe 24 is located in the middle of the double-layer sieve plate liquid distribution plate 6. The gas flows evenly through the gas distribution holes 28 of the gas distribution pipe 24, so that the gas lift gas can fully exchange heat and mass with the upper sieve plate and packing. This ensures that the light components in the liquid phase, after passing through the double-layer sieve plate liquid distribution plate 6, packing 4, baffle plate 23, and wire mesh demister 5, exit the flash tower 2 and enter the negative pressure screw compressor 9 for pressurization before flashing out the associated gas outlet 17. The gas is then cooled by the cooling water inlet 21. The flash tower 2 and the associated gas outlet 17 are respectively equipped with a container safety valve 13 and a compressor outlet safety valve 14, leading to the vent outlet 19. A stripper gas inlet 18 is installed on the upper side of the stabilizer tank 1. The stripper gas volume is controlled by a vortex flow meter 11 on the stripper gas inlet 18 pipeline, interlocked with an electric regulating valve 12 on the stripper gas inlet 18 pipeline. The liquid flowing down through the double-layer screen plate distribution tray 6 reaches the lower part of the stabilizer tank 1, and is then pumped out via a remote dual-flange level gauge 8 interlocked with a booster pump 10, and discharged through the stabilized shale oil outlet 16. A local magnetic level gauge 7 is used to calibrate the height of the remote dual-flange level gauge 8. Simultaneously, a sludge outlet 20 is installed at the bottom of the stabilizer tank 1.

[0018] Working Principle: The purified shale oil inlet 15 is evenly distributed to two flash towers 2. The inlet liquid is atomized by a double-layer spray plate 3 and separated into gas and liquid by a herringbone collision plate 27. The separated gas phase first passes through a baffle 23, where large droplets are separated by collision. Then, small droplets are coalesced by a wire mesh demister 5, ensuring the dryness of the gas phase exiting flash tower 2. Removable flanges are installed on the walls of flash tower 2 above the wire mesh demister 5 and below the spray plate 3 for easy disassembly and maintenance. The top of flash tower 2 is connected to a negative pressure screw compressor 9, ensuring negative pressure within the stabilizing tank 1 and flash tower 2. When the purified shale oil inlet 15 enters flash tower 2, it undergoes a pressure reduction process through the spray plate 3. Flash evaporation allows for a primary gas-liquid separation of some light components in the incoming liquid. The liquid is then uniformly sprayed onto the packing 4. Gas is introduced through the rising gas inlet 18 and distributed via a three-pipe design in the gas distribution pipe 24. Each branch pipe features a double-row, downward-sloping 45° gas distribution hole design to ensure uniform gas distribution. The gas distribution pipe 24 is positioned between the double-layer sieve plate liquid distribution plate 6, allowing for mass and heat transfer processes on both the upper sieve plate liquid distribution plate 6 and the surface of the packing 4. This achieves secondary volatilization of the light components in the liquid, further reducing the saturated vapor pressure of the liquid phase. The liquid passing through the packing 4 then descends onto the sieve plate liquid distribution plate 6. By remaining on the large-area, low-flow-rate sieve plate liquid distribution plate 6, a tertiary volatilization of the light components in the liquid phase is achieved, ensuring that the liquid passing through the sieve plate liquid distribution plate 6 meets the saturated vapor pressure requirements for transport.

[0019] The stabilized shale oil flowing to the bottom of the stabilization tank 1 is interlocked with the frequency converter of the booster pump 10 through the remote dual-flange level gauge 8. The discharge rate of the booster pump 10 after stabilization at the shale oil outlet 16 is controlled by the stabilized shale oil level in the stabilization tank 1, ensuring the relative stability of the liquid level in the stabilization tank 1. At the same time, a local magnetic level gauge 7 is installed on the stabilization tank 1 to check the height of the remote dual-flange level gauge 8.

[0020] The gas lift inlet 18 is equipped with a vortex flow meter 11, which is interlocked with the gas lift inlet 18 pipeline electric regulating valve 12 to adjust the gas lift volume according to the liquid volume of the purified shale oil inlet 15.

[0021] A container safety valve 13 and a compressor outlet safety valve 14 are respectively installed on the outlet manifold of the two flash towers 2 and the compressor outlet pipeline, which are discharged to the vent outlet 19; a sewage outlet 20 is installed at the bottom of the stabilizer tank 1 for periodic sewage discharge or drainage when the stabilizer tank 1 is shut down.

[0022] The negative pressure screw compressor 9 is a water-cooled screw compressor. The temperature of the purified shale oil inlet 15 needs to be controlled at around 65℃, and the inlet temperature of the associated gas entering the negative pressure screw compressor 9 needs to be <65℃, which is 10℃ to 20℃ lower than the conventional negative pressure flash evaporation process. The gas phase separated at the top of the flash tower 2 can be directly connected to the negative pressure screw compressor 9, so that negative pressure is formed in the stabilization unit, simplifying the auxiliary system of the original stabilization unit. The temperature of the pressurized associated gas is kept <85℃ by cooling water. Compared with the conventional negative pressure crude oil stabilization process, the heating system before the stabilization tower, the gas phase negative pressure condenser after the stabilization tower, and the negative pressure separator can be reduced, realizing the optimization and simplification of the original stabilization system.

[0023] Meanwhile, this device adopts a double flash tower design, which can select to use two flash towers at the same time or use only one flash tower according to the fluctuation of the production of a single shale oil well or well group, so as to ensure the stability of the device operation when the production of a single shale oil well or well group changes. The overall operational flexibility of the device can reach 30% to 120%.

[0024] This invention combines the effects of gas stripping and negative pressure stabilizing flash evaporation on crude oil stabilization, enabling short-process, skid-mounted processing of purified shale oil. This avoids safety risks and oil and gas losses during the transportation of purified shale oil, achieving efficient and stable shale oil processing.

[0025] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and application concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A dual-tower shale oil crude oil stabilization device, comprising a stabilization tank (1), characterized in that: The stabilizer (1) has two flash towers (2) arranged side by side on the top. The middle of the flash tower (2) is connected to the purified shale oil inlet (15). The flash tower (2) has a double-layer spray plate (3) connected to the liquid inlet. The upper layer of the double-layer spray plate (3) is a spray head (25). The lower surface of the spray head (25) is provided with a circular spray nozzle (26). The lower layer is a "V"-shaped collision plate (27). The spray plate (3) is provided with packing (4) below and baffle (23) and wire mesh demister (5) above. The tower wall of the flash tower (2) is provided with a detachable flange (22) above the wire mesh demister (5) and below the spray plate (3). The top of the flash tower (2) is connected to the negative pressure screw. The negative pressure screw compressor (9) is connected to a flash gas outlet (17), and the flash gas outlet (17) and the flash tower (2) are both connected to the air vent outlet (19); the stabilizer (1) is provided with a sieve plate liquid distribution plate (6); the stabilizer (1) is provided with a gas lift inlet (18) on one side of the upper part; the gas lift inlet (18) is connected to the gas distribution pipe (24), the gas distribution pipe (24) is located between two layers of sieve plate liquid distribution plates (6), and is composed of three gas distribution branches, with double rows of 45° downward gas distribution holes (28) evenly arranged on the gas distribution branches; the stabilizer (1) is provided with a sewage outlet (20) and a stabilized shale oil outlet (16) at the bottom.

2. The dual-tower shale oil crude oil stabilization device as described in claim 1, characterized in that: The negative pressure screw compressor (9) is connected to a cooling water inlet (21).

3. The dual-tower shale oil crude oil stabilization device as described in claim 1, characterized in that: The flash tower (2) is equipped with a container safety valve (13), and the flash gas outlet (17) is equipped with a compressor outlet safety valve (14).

4. The dual-tower shale oil crude oil stabilization device as described in claim 1, characterized in that: The gas lift inlet (18) is equipped with a vortex flow meter (11) and a gas lift electric regulating valve (12).

5. The dual-tower shale oil crude oil stabilization device as described in claim 1, characterized in that: A booster pump (10) is installed on the pipeline of the stabilized shale oil outlet (16); a local magnetic level gauge (7) and a remote double flange level gauge (8) are installed on the stabilizing tank (1), and the remote double flange level gauge (8) is interlocked with the booster pump (10).

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