An oil and gas recovery system and method

Abstract

This application provides an oil and gas recovery system and method, relating to the field of crude oil and gas recovery technology in underground water-sealed oil caverns. The oil and gas recovery system includes: a pre-absorption tower, a membrane separation device, an adsorption device, and a desorption gas treatment device; the membrane separation device is connected to the top of the pre-absorption tower and is used to perform membrane separation treatment on the unabsorbed oil and gas in the pre-absorption tower to obtain organic oil and gas; the adsorption device includes a vacuum pump and at least two adsorption-desorption towers, the bottom of the adsorption-desorption towers is connected to the membrane separation device through an organic oil and gas pipeline and to the vacuum pump through a desorption pipeline; the desorption gas treatment device is connected to the vacuum pump. Based on the characteristics of crude oil and gas in caverns, this application solves the problem of crude oil and gas recovery in underground water-sealed rock cavern oil depots by setting up a pre-absorption tower and utilizing the advantages of existing single processes, and by rationally combining the various devices in a specific sequence.

Description

Technical Field

[0001] This application relates to the field of crude oil and gas recovery technology in underground water-sealed oil caverns, and particularly to an oil and gas recovery system and method. Background Technology

[0002] Most of the crude oil storage facilities currently under construction or planned are water-sealed cavern oil storage facilities. The oil and gas generated when crude oil enters the cavern can have a certain impact on the normal production and operation of the cavern. Direct discharge into the atmosphere will also cause environmental pollution. Therefore, it is necessary to recover the discharged oil and gas.

[0003] Currently, the principles of oil and gas recovery in crude oil storage caverns all utilize the kinetic energy generated during the descent of the oil to recover the oil and gas within the storage tank. However, this process requires increasing storage pressure and expanding the gas space volume, while ensuring that oil and gas are not released during operation. Furthermore, this method is suitable for scenarios with small storage capacity and high crude oil turnover rates. Since caverns typically only rotate crude oil once every 5-10 years, the turnover frequency is low, making this method a significant investment for larger caverns.

[0004] Conventional oil and gas recovery processes often employ a combination of adsorption and absorption, but this approach is difficult to apply to crude oil and gas recovery. Firstly, crude oil and gas recovery involves a larger scale compared to gasoline-based recovery, requiring larger individual equipment, which presents challenges in manufacturing, transportation, installation, and maintenance. Secondly, the direct entry of large amounts of oil and gas into the adsorption tower without necessary regulation can lead to overload and subsequent shutdowns. This is especially true for underground crude oil storage, where factors such as oil mixing, transportation processes, batch sizes, and intervals all have an impact. In particular, the non-methane components in the non-condensable gas returning from the top of the absorber tower during the initial intake or each batch can reduce the tower's capacity. Furthermore, underground storage facilities are often located in remote areas with limited land and development difficulties, lacking suitable conditions for setting up absorption systems. Using common absorbents like kerosene, gasoline, or light diesel requires additional systems, and the rich oil after absorption has no outlet, making conventional absorbents unsuitable for underground oil and gas recovery.

[0005] Existing oil and gas recovery processes for large-scale oil and gas volumes sometimes involve adding one or more adsorption / desorption towers, ultimately increasing investment and operational complexity. Given the characteristics of underground crude oil, such as large-scale oil and gas volatilization, low concentrations (total hydrocarbon molar fraction approximately 20%), and the presence of methane and ethane, some methods, such as condensation or composite oil and gas recovery methods with condensation located upstream, are also used. However, these methods require very low condensation temperatures, resulting in high energy consumption and are therefore unsuitable for underground crude oil and gas recovery.

[0006] Therefore, in order to meet stringent emission standards and reduce investment and operating costs, it is necessary to find a suitable oil and gas recovery technology for underground water-sealed rock cavern oil depots. Summary of the Invention

[0007] The purpose of this application is to provide an oil and gas recovery system and method suitable for underground water-sealed rock cavern oil depots. Based on the characteristics of crude oil and gas in caverns, and utilizing the advantages of various existing processes, a pre-absorption and membrane separation process is added. This solves the problem that in the initial stage of each batch of oil intake, a large amount of oil and gas saturates the adsorbent in the adsorption tower, leading to excessive emissions of oil and gas. At the same time, the membrane separation process has a relatively stable processing efficiency and can play a smooth transition role between the pre-absorption and adsorption processes, which is beneficial to the absorption effect of the adsorption tower, thereby solving the problem of crude oil and gas recovery.

[0008] To achieve the above objectives, the technical solution of this application is as follows:

[0009] This application provides an oil and gas recovery system for use in underground water-sealed rock cavern oil depots, comprising:

[0010] A pre-absorption tower is used to receive crude oil from the oil depot and to absorb the oil and gas collected at the bottom of the pre-absorption tower using the crude oil.

[0011] A membrane separation device is connected to the top of the pre-absorption tower and is used to perform membrane separation treatment on the oil and gas that has not been absorbed in the pre-absorption tower to obtain organic oil and gas.

[0012] An adsorption device includes a vacuum pump and at least two adsorption-desorption towers. The adsorption-desorption towers are used to adsorb the organic oil and gas. The vacuum pump is used to desorb and regenerate the adsorption-desorption towers when they reach saturation. The bottom of the adsorption-desorption towers is connected to the membrane separation device through an organic oil and gas pipeline and to the vacuum pump through a desorption pipeline.

[0013] A desorption gas treatment device, connected to the vacuum pump, is used to treat the desorption gas obtained after desorption and regeneration.

[0014] Preferably, the oil and gas recovery system satisfies at least one of the following conditions:

[0015] a. The top of the pre-absorption tower is connected to the membrane separation device via an outlet pipeline and to the oil depot via a return oil depot pipeline;

[0016] b. The top of the pre-absorption tower is also equipped with a non-methane total hydrocarbon concentration meter to monitor the concentration of non-methane total hydrocarbons in the gas at the top of the pre-absorption tower;

[0017] c. The pre-absorption tower is provided with trays and / or packing inside, and a wire mesh demister is provided above the trays and / or packing;

[0018] d. The bottom of the pre-absorption tower is connected to the crude oil and gas in the oil depot via an air inlet pipe;

[0019] e. The bottom of the pre-absorption tower is provided with a first rich oil outlet for discharging the rich oil after absorbing oil and gas.

[0020] More preferably, the oil and gas recovery system also satisfies at least one of the following conditions:

[0021] f. The outlet pipeline and the return oil depot pipeline are each equipped with an independent shut-off valve;

[0022] g. The air inlet pipeline is also equipped with a mixer and a blower. The mixer is used to mix the crude oil gas in the oil depot with the gas treated by the desorbed gas treatment device. The blower is used to pressurize the mixed gas in the mixer and send it into the pre-absorption tower.

[0023] h. The oil inlet of the pre-absorption tower is located between the wire mesh demister and the tower plate and / or packing;

[0024] i. The inlet of the pre-absorption tower is located between the first rich oil outlet and the tower plate and / or packing.

[0025] Preferably, when the number of days with a maximum temperature ≥30℃ in the area where the oil depot is located is not less than 30 days per year, the desorbed gas treatment device is a gas-liquid separator;

[0026] Alternatively, if the number of days with a maximum temperature ≥30℃ in the area where the oil depot is located is less than 30 days per year, the desorbed gas treatment device is an absorption tower.

[0027] More preferably, when the desorbed gas treatment device is an absorption tower, the oil and gas recovery system satisfies at least one of the following conditions:

[0028] j. The absorption tower is provided with a crude oil inlet for receiving crude oil from the oil depot and using the crude oil to absorb the desorbed gas;

[0029] k. The top of the absorption tower is connected to the bottom of the pre-absorption tower via a gas recovery pipeline;

[0030] 1. The bottom of the absorption tower is connected to the vacuum pump;

[0031] m. The bottom of the absorption tower is provided with a second rich oil outlet.

[0032] More preferably, when the desorbed gas treatment device is a gas-liquid separator, the oil and gas recovery system satisfies at least one of the following conditions:

[0033] n. A cryogenic cooler is also provided between the gas-liquid separator and the vacuum pump;

[0034] o. The gas outlet of the gas-liquid separator is connected to the bottom of the pre-absorption tower;

[0035] p. The liquid outlet of the gas-liquid separator is connected to the liquid hydrocarbon pipeline.

[0036] Preferably, the tops of the membrane separation device and the adsorption-desorption tower are respectively connected to an exhaust pipe.

[0037] This application also provides an oil and gas recovery method, applicable to underground water-sealed rock cavern oil depots, including:

[0038] The crude oil and crude oil gas from the oil depot are introduced into the pre-absorption tower respectively, and the crude oil is used to absorb the crude oil gas.

[0039] The unabsorbed oil and gas in the pre-absorption tower are transported to the membrane separation unit, where organic oil and gas are obtained through membrane separation.

[0040] The organic oil gas is introduced into the first adsorption-desorption tower of the adsorption device, which has not reached the saturation adsorption state, for adsorption and separation. After the first adsorption-desorption tower reaches the saturation adsorption state, the organic oil gas is automatically switched to the second adsorption-desorption tower, which has not reached the saturation adsorption state. Then, the first adsorption-desorption tower, which has reached the saturation adsorption state, is desorbed and regenerated by a vacuum pump to obtain desorbed gas.

[0041] The desorbed gas is transported to a desorbed gas treatment device for desorbed gas recovery.

[0042] Preferably, the oil and gas recovery method satisfies at least one of the following conditions:

[0043] q. When the crude oil is introduced into the absorption tower, the gauge pressure of the crude oil is 0.1 MPa - 0.2 MPa;

[0044] r. When the crude oil gas is introduced into the absorption tower, the gauge pressure of the crude oil gas is 0.1 MPa - 0.2 MPa;

[0045] s. After the crude oil and gas undergo dehydration and desulfurization, they are mixed with the desorbed gas and then introduced into the pre-absorption tower;

[0046] The desorption and regeneration process includes: firstly, using the vacuum pump to evacuate the first adsorption-desorption tower to provide negative pressure; when the organic components on the adsorbent begin to desorb, introducing an inert gas into the first adsorption-desorption tower to maintain the vacuum pressure and perform vacuum cleaning to obtain a desorbed gas after mixing the organic components with the inert gas; then, pressurizing the desorbed gas with the vacuum pump and introducing it into the desorbed gas treatment device.

[0047] u. When the desorbed gas treatment device is a gas-liquid separator, it includes: pre-cooling the crude oil using liquid hydrocarbons separated by the gas-liquid separator before introducing the crude oil into the pre-absorption tower.

[0048] Preferably, the oil and gas recovery method further includes:

[0049] The top of the pre-absorption tower is equipped with a non-methane total hydrocarbon concentration meter. When the concentration value displayed on the non-methane total hydrocarbon concentration meter is greater than a set value, the unabsorbed oil and gas is transferred to the oil storage tank. When the concentration value is less than or equal to the set value, the unabsorbed oil and gas is then transferred to the membrane separation device.

[0050] The beneficial effects of this application are:

[0051] This application, based on a traditional integrated oil and gas recovery device combining adsorption and absorption, incorporates a pre-absorption tower and a membrane separation unit. The pre-absorption tower addresses the issue of large volumes of oil and gas at the initial stage of each batch of oil intake, which can saturate the adsorbent in the adsorption unit and lead to excessive emissions. This reduces the impact of investment and future upgrades to oil and gas emission standards. The membrane separation unit separates some air, increasing the hydrocarbon concentration in the oil and gas and improving the adsorption efficiency of the adsorption unit. This oil and gas recovery device is suitable not only for newly built underground water-sealed rock cavern oil depots but also for upgrading existing conventional oil and gas recovery processes.

[0052] In the oil and gas recovery method of this application, pre-absorption is carried out using a pre-absorption tower before the adsorption process, especially by using crude oil from underground water-sealed rock cave oil depots to achieve pre-recovery of oil and gas. This solves the technical problem that the oil and gas emitted from the adsorption device is prone to exceed the standard in the early stage of oil intake, and also reduces investment costs and the impact of subsequent upgrades to oil and gas emission standards. At the same time, membrane separation treatment can increase the concentration of organic hydrocarbons in the oil and gas, improve the adsorption effect, and further improve the oil and gas recovery efficiency. Attached Figure Description

[0053] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0054] Figure 1 This is a schematic diagram of the oil and gas recovery system of the underground water-sealed rock cavern oil depot in Example 1;

[0055] Figure 2 This is a schematic diagram of the oil and gas recovery system of the underground water-sealed rock cavern oil depot in Example 2.

[0056] Explanation of icon numbers:

[0057] 100-Pre-absorption tower; 1001-Tower tray and / or packing; 1002-Wire mesh demister; 1003-Oil inlet; 1004-Air inlet; 1005-First rich oil outlet; 1006-Non-methane total hydrocarbon concentration meter;

[0058] 200-Membrane separation unit;

[0059] 300 - Adsorption device; 301 - Vacuum pump; 302 - First adsorption-desorption tower; 303 - Second adsorption-desorption tower; 304 - Cryogenic cooler;

[0060] 400 - Desorbed gas treatment unit; 401 - Absorption tower; 4011 - Crude oil inlet; 4012 - Second rich oil outlet; 402 - Gas-liquid separator; 4021 - Gas outlet; 4022 - Liquid outlet;

[0061] 500 - Mixer; 600 - Blower; 700 - Shut-off valve; 900 - Crude oil delivery pipeline; 901 - Inlet pipeline; 902 - Outlet pipeline; 903 - Return pipeline to oil depot; 904 - Organic oil and gas pipeline; 905 - Desorption pipeline; 906 - Desorbed gas pipeline; 907 - Gas recovery pipeline; 908 - Exhaust pipeline; 909 - Liquid hydrocarbon pipeline. Detailed Implementation

[0062] As used in this article:

[0063] "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such a composition, step, method, article, or apparatus. The conjunction "composed of" excludes any unnamed elements, steps, or components.

[0064] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0065] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0066] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0067] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions are followed.

[0068] Example 1

[0069] Figure 1 A schematic diagram of an oil and gas recovery system applied to an underground water-sealed rock cavern oil depot, as provided in Embodiment 1 of this application, is shown. (Refer to...) Figure 1 The oil and gas recovery system includes: a pre-absorption tower 100, a membrane separation device 200, an adsorption device 300, and a desorbed gas treatment device 400. Among them, the desorbed gas treatment device 400 is an absorption tower 401.

[0070] It should be noted that the desorbed gas treatment device 400 of this application is mainly used to recover and treat the desorbed gas formed after desorption and regeneration. It can be used either an absorption tower 401 or a gas-liquid separator 402 for recovery and treatment. The choice between these two devices is mainly based on the climate environment of the area where the underground water-sealed rock cavern oil depot is located.

[0071] If the area where the cavern is located experiences few high-temperature days per year, for example, fewer than 30 days with a maximum temperature ≥30℃, then absorption tower 401 is selected. This is because the absorbent used in the absorption tower of this application is crude oil from the cavern, not commonly used kerosene, gasoline, or light diesel oil. Caverns are generally buried 100m below the surface, where the temperature of the stored crude oil can be maintained at around 20℃. The crude oil taken from the bottom of the cavern, after being pressurized to a certain pressure by a submersible pump, is relatively "unsaturated" and can absorb crude oil vapors. When the ambient temperature is not high, the temperature of the desorbed gas obtained in the adsorption device 300 will also be relatively low, and this desorbed gas can be absorbed by the low-temperature crude oil. However, when the ambient temperature is too high, on the one hand, the temperature of the desorbed gas itself is high, and on the other hand, the temperature of the crude oil entering absorption tower 401 is also high, making it easy to volatilize into gas, thus making it difficult to effectively absorb oil vapors. Therefore, if the area where the cave is located experiences many high-temperature days each year, for example, if the number of days with a maximum temperature of ≥30℃ is not less than 30 days, then the gas-liquid separator 402 should be used for cooling and recovery treatment.

[0072] The pre-absorption tower 100 in this embodiment is mainly used to receive crude oil from the underground water-sealed rock cave oil depot and to use the crude oil to absorb the oil and gas collected at the bottom of the pre-absorption tower 100.

[0073] The crude oil extracted from the lower part of the cavern, after being pressurized to a certain pressure by a submersible pump, is relatively "unsaturated." It can be used as the absorbent in the pre-absorption tower 100 to absorb a portion of the oil and gas. Calculations show that crude oil at room temperature, under a pressure of 0.1 MPa, can absorb more than one times its own volume of oil and gas. Therefore, using the crude oil from the cavern to absorb a portion of the oil and gas in the pre-absorption tower 100 can reduce the problem of excessive gas flow leading to absorbent saturation and excessive emissions when the gas enters the adsorption unit 300.

[0074] The pre-absorption tower 100 has a first rich oil outlet 1005 at the bottom for discharging the rich oil after absorbing oil and gas; the pre-absorption tower 100 has a tray and / or packing 1001 inside, and a wire mesh demister 1002 is also provided above the tray and / or packing 1001; the oil inlet 1003 of the pre-absorption tower 100 is located between the wire mesh demister 1002 and the tray and / or packing 1001, and the air inlet 1004 of the pre-absorption tower 100 is located between the tray and / or packing 1001 and the first rich oil outlet 1005.

[0075] The air inlet 1004 at the bottom of the pre-absorption tower 100 is connected to the crude oil and gas in the underground water-sealed rock cave oil depot via the air inlet pipe 901.

[0076] A mixer 500 and a blower 600 are also provided on the air intake pipe 901. The mixer 500 is used to mix the crude oil and gas in the underground water-sealed rock cave oil depot with the gas treated by the desorption gas treatment device 400. The blower 600 is used to pressurize the mixed gas in the mixer 500 and send it into the pre-absorption tower 100.

[0077] The membrane separation device 200 is connected to the top of the pre-absorption tower 100 and is used to perform membrane separation treatment on the unabsorbed oil and gas in the pre-absorption tower 100 to obtain concentrated organic oil and gas. This organic oil and gas enters the adsorption device 300 and can be effectively adsorbed by the adsorbent. The air separated by the membrane separation device 200 can be discharged into the atmosphere or transferred to the adsorption device 300 for desorption and regeneration of the adsorbent.

[0078] It is understandable that the oil and gas recovery system of this application is mainly aimed at oil and gas recovery in underground water-sealed rock cavern oil depots. Therefore, the characteristic of this oil and gas is its low concentration. Thus, if the oil and gas that has not been absorbed by crude oil in the pre-absorption tower 100 is directly sent to the adsorption device 300 for subsequent adsorption and other processes, the adsorbent will find it difficult to fully adsorb the low-concentration oil and gas. Therefore, adding a membrane separation device 200 can increase the concentration of the subsequently transmitted oil and gas, making it easier for the adsorbent to adsorb and recover it.

[0079] In addition to being connected to the membrane separation unit 200 via the gas outlet pipeline 902, the top of the pre-absorption tower 100 is also connected to the underground water-sealed rock cave oil depot via the return oil depot pipeline 903.

[0080] The top of the pre-absorption tower 100 is also equipped with a non-methane total hydrocarbon concentration meter 1006, which is used to monitor the concentration of non-methane total hydrocarbons in the gas at the top of the pre-absorption tower 100.

[0081] Furthermore, each of the gas outlet pipeline 902 and the return oil depot pipeline 903 is independently equipped with a shut-off valve 700. When the concentration value displayed on the non-methane total hydrocarbon concentration meter 1006 is higher than the set value, it indicates that the total hydrocarbon organic matter content in the oil and gas at the top of the tower is too high. This means that the low-temperature crude oil in the pre-absorption tower 100 has not fully absorbed the hydrocarbon organic matter in the crude oil and gas. At this time, the shut-off valve 700 on the gas outlet pipeline 902 can be closed, allowing the oil and gas to return to the underground water-sealed rock cavern oil depot through the return oil depot pipeline 903. By adjusting the amount of crude oil introduced into the pre-absorption tower 100, until the concentration value displayed on the non-methane total hydrocarbon concentration meter at the top of the tower is lower than or equal to the set value, the shut-off valve 700 on the return oil depot pipeline 903 is closed, and the gas outlet pipeline 902 is opened, allowing the oil and gas to enter the membrane separation unit 200 through the gas outlet pipeline 902.

[0082] The adsorption device 300 includes a vacuum pump 301 and two mutually switching adsorption-desorption towers 302 and 303. The adsorption-desorption towers are mainly used to adsorb the organic oil and gas separated in the membrane separation device 200, while the vacuum pump 301 is used to desorb and regenerate the adsorption-desorption towers that have reached saturation.

[0083] In this embodiment, there are two adsorption / desorption towers. However, in other embodiments, there may be three, four, or more adsorption / desorption towers.

[0084] In this embodiment, the bottom of the first adsorption-desorption tower 302 and the second adsorption-desorption tower 303 are both connected to the membrane separation device 200 through an organic oil and gas pipeline 904, and the bottom of the towers are also connected to the vacuum pump 301 through a desorption pipeline 905.

[0085] In this embodiment, when oil and gas enter the first adsorption-desorption tower 302 in the adsorption state through the organic oil and gas pipeline 904, under normal temperature and pressure conditions, the organic components in the oil and gas that are easily adsorbed are adsorbed by the adsorbent in the first adsorption-desorption tower 302, while the gas that is not easily adsorbed can be directly discharged into the atmosphere through the exhaust pipeline 908 if it passes the tail gas test.

[0086] When the adsorbent in the first adsorption-desorption tower 302 reaches a certain adsorption saturation, the first adsorption-desorption tower 302 and the second adsorption-desorption tower 303 automatically switch to the desorption-regeneration state, while the second adsorption-desorption tower 303, which has completed desorption-regeneration, switches to the adsorption state.

[0087] The specific process of desorption and regeneration includes: first, vacuum pump 301 is used to evacuate the first adsorption-desorption tower 302. The organic components on the adsorbent are desorbed by the negative pressure provided by vacuum pump 301. Then, a certain amount of inert gas is introduced to maintain the vacuum pressure and perform vacuum cleaning so that all the organic components on the adsorbent can be desorbed, and the desorbed gas after mixing the organic components with the inert gas is obtained. Then, the desorbed gas is extracted by vacuum pump 301, thereby realizing the desorption and regeneration of the first adsorption-desorption tower 302.

[0088] The absorption tower 401 is connected to the vacuum pump 301 via a desorption gas pipeline 906; the absorption tower 401 is also equipped with a crude oil inlet 4011 for receiving crude oil from the underground water-sealed rock cave oil depot, and a second rich oil outlet 4012 for discharging crude oil that has absorbed the desorption gas.

[0089] The top of the absorption tower 401 is connected to the bottom of the pre-absorption tower 100 via a gas recovery pipeline 907, which is used to return the unabsorbed desorbed gas to the pre-absorption tower 100 for further oil and gas recovery. Furthermore, the gas recovery pipeline 907 first passes through a mixer 500, and then through a blower 600 into the pre-absorption tower 100.

[0090] The oil and gas recovery system of this embodiment solves the problem that in the initial stage of each oil intake of crude oil in the underground water-sealed cavern oil depot, the large volume of oil and gas can easily saturate the adsorbent in the adsorption device 300, leading to excessive exhaust gas. Furthermore, by using the crude oil from the underground water-sealed cavern oil depot as the absorbent in the pre-absorption tower 100 and the absorption tower 401, the investment cost of the entire system is greatly reduced.

[0091] Example 2

[0092] Figure 2 A schematic diagram of an oil and gas recovery system for an underground water-sealed rock cavern oil depot provided in Embodiment 2 of this application is shown.

[0093] like Figure 2 As shown, the oil and gas recovery system in this embodiment is basically similar to the oil and gas recovery system in embodiment 1. The difference is that the desorbed gas treatment device 400 in this embodiment is a gas-liquid separator 402. The organic matter in the desorbed gas is converted into liquid hydrocarbons by using a condensation method. Therefore, there is no crude oil inlet on the gas-liquid separator 402.

[0094] Understandably, when the temperature in the area where the underground water-sealed cavern oil depot is located is high, the temperature of each device in the oil and gas recovery system will also increase, and the oil and gas content in the underground water-sealed cavern oil depot will also increase. When crude oil, acting as the absorbent, comes into contact with high-temperature oil and gas, its absorption efficiency is significantly lower than its absorption efficiency for low-temperature oil and gas. Therefore, in high-temperature environments, to improve oil and gas recovery efficiency, it is more suitable to use a gas-liquid separator 402 to condense and recover the desorbed gas.

[0095] The gas-liquid separator 402 is connected to the vacuum pump 301 via a desorption gas pipeline 906. A cryogenic cooler 304 is also provided on the desorption gas pipeline 906 to cool the desorbed gas obtained from desorption and regeneration in advance.

[0096] The gas-liquid separator 402 is also equipped with a gas outlet 4021 and a liquid outlet 4022. The condensed residual gas enters the gas recovery pipeline 907 through the gas outlet 4021 and ultimately flows into the pre-absorption tower 100. The condensed liquid enters the liquid hydrocarbon pipeline 909 through the liquid outlet 4022.

[0097] Furthermore, the temperature of the condensed liquid hydrocarbon is very low. By utilizing the thermal conduction effect, the liquid hydrocarbon pipeline 909 can be brought into close contact with the crude oil pipeline 900 to pre-cool the crude oil in the crude oil pipeline 900, preventing the crude oil temperature from being too high and affecting the absorption efficiency.

[0098] Compared to Example 1, the oil and gas recovery system in this example solves the problem of low absorption efficiency when using crude oil as an absorbent in a high-temperature environment by replacing the absorption tower 401 with a gas-liquid separator 402.

[0099] Example 3

[0100] This embodiment takes an underground water-sealed cavern oil depot in northern China (where summer temperatures are low) as an example and provides a method for oil and gas recovery in an underground water-sealed cavern oil depot. This method uses the oil and gas recovery system of Embodiment 1.

[0101] The total storage capacity of this underground water-sealed rock cavern oil depot is 3000 dams. 3 The computing capacity is 3200 dam. 3 The stored crude oil is light crude oil. Three crude oil storage tanks were constructed, each consisting of three chambers, all with interconnected roofs. The maximum storage pressure in each tank is P = 0.1 MPa, and the minimum storage pressure is 0.01 MPa. The operating temperature of the crude oil and oil vapor inside the tanks is 15°C, and the total recovered oil vapor is 1200 Nm³. 3 / h, total hydrocarbon content 20% (V).

[0102] The oil and gas recovery methods for this underground water-sealed cavern oil depot include:

[0103] (1) After the crude oil and gas in the underground water-sealed rock cave oil depot are dehydrated and desulfurized, they are pressurized to 0.2 MPa by blower 600 and then enter the pre-absorption tower 100. The crude oil in the underground water-sealed rock cave oil depot is compressed to 0.2 MPa by submersible pump from the bottom of the cave and then extracted into the pre-absorption tower 100. The crude oil absorbs the soluble components in the crude oil and gas in the tower plates and / or packing 1001 in the pre-absorption tower. The operating pressure of the pre-absorption tower is set at 0.17 MPa.

[0104] (2) A non-methane total hydrocarbon concentration meter 1006 is installed at the top of the pre-absorption tower 100. When the concentration value displayed on the meter is greater than the set value, the gas at the top of the tower that does not meet the requirements is returned to the underground water-sealed rock cavern oil depot through the return oil depot pipeline 903. By adjusting the crude oil extraction rate, when the concentration value displayed on the meter is less than or equal to the set value, the shut-off valve 700 on the return oil depot pipeline 903 is closed, allowing the gas to enter the membrane separation device 200. After membrane separation treatment, organic oil gas is obtained, and the air separation efficiency is 20%-80%. This set value can be flexibly set according to the oil gas recovery situation. Taking the non-methane total hydrocarbon concentration at the top of the pre-absorption tower as an example of 12.5 g / ml, according to the simulation calculation, when the crude oil extraction rate reaches 5 t / h, the diameter of the pre-absorption tower is 0.5 m.

[0105] (3) The organic oil and gas after membrane separation is introduced into the first adsorption-desorption tower 302, which has not reached the saturated adsorption state, for adsorption. Specifically, the adsorption-desorption tower is filled with 30m³ of adsorption-desorption material. 3 Activated carbon is used for adsorption. During the process of organic oil and gas passing through the adsorption-desorption tower, the organic matter with stronger adsorption capacity is adsorbed by the adsorbent, while the inert gas components with weaker adsorption capacity become the tail gas. If the non-methane total hydrocarbon concentration is ≤25g / m³, the adsorption is successful. 3 When the non-methane total hydrocarbon recovery rate is >97%, the tail gas is directly discharged into the atmosphere through the adsorption-desorption tower. After the first adsorption-desorption tower 302 reaches saturation adsorption, the organic oil gas is automatically switched to the second adsorption-desorption tower 303, which has not yet reached saturation adsorption, with a switching time ≤30 minutes. After the switching is completed, the first adsorption-desorption tower 302, which has reached saturation adsorption, is desorbed and regenerated using a vacuum pump 301. Specifically, a negative pressure is provided by evacuation. When the organic components on the adsorbent begin to desorb, an inert gas is introduced into the first adsorption-desorption tower 302 to maintain the vacuum pressure and perform vacuum cleaning, desorbing the organic matter adsorbed on the adsorbent to obtain desorbed gas, while restoring the adsorption activity of the adsorbent.

[0106] (4) The desorbed gas is passed through a pump with a flow rate of 3000m³. 3 The gas is pressurized by a vacuum pump at a rate of / h and sent to the absorption tower 401. Crude oil from the underground water-sealed cavern oil depot is then used as the absorbent to absorb the organic matter in the desorbed gas. The organic matter is absorbed and liquefied by the crude oil, becoming rich oil, which is then returned to the cavern. Meanwhile, the non-condensable gas at the top of the absorption tower 401 enters the mixer 500 along the gas recovery pipeline 907. After mixing with the crude oil gas, it is pressurized by the blower 600 and sent to the pre-absorption tower 100 for further adsorption treatment.

[0107] Example 4

[0108] This embodiment takes an underground water-sealed cavern oil depot in southern China (where high temperatures are common) as an example and provides a method for oil and gas recovery in an underground water-sealed cavern oil depot. This method uses the oil and gas recovery system of Embodiment 2.

[0109] The total storage capacity of this underground water-sealed rock cavern oil depot is 3000 dams. 3 The computing capacity is 3200 dam. 3 The stored crude oil is light crude oil. Three crude oil storage tanks were constructed, each consisting of three chambers, all with interconnected roofs. The maximum storage pressure in each tank is P = 0.1 MPa, and the minimum storage pressure is 0.01 MPa. The operating temperature of the crude oil and oil vapor inside the tanks is 15°C, and the total recovered oil vapor is 1500 Nm³. 3 / h, total hydrocarbon content 20% (V).

[0110] The method for oil and gas recovery in this cavern is the same as in Example 3, except that:

[0111] In step (4), the desorbed gas is pressurized by vacuum pump 301, first sent to cryogenic cooler 304 for cooling, and then sent to gas-liquid separator 402 for gas-liquid separation. The separated liquid hydrocarbons enter liquid hydrocarbon pipeline 909 to pre-cool the crude oil in crude oil delivery pipeline 900, reducing the crude oil temperature by 5℃-10℃ to improve the absorption effect in pre-absorption tower 100. The non-condensable gas enters mixer 500 along gas recovery pipeline 907, mixes with crude oil gas, and is then pressurized by blower 600 before being sent to pre-absorption tower 100 for adsorption treatment again.

[0112] According to the simulation results of the system, when the desorbed gas with a concentration of 70% is cooled to -35℃, the liquid recovery rate reaches about 90%.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0114] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, any of the embodiments claimed above can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. An oil and gas recovery system, applied to an underground water-sealed rock cavern oil depot, characterized in that, include: A pre-absorption tower is used to receive crude oil from the oil depot and to absorb the oil and gas collected at the bottom of the pre-absorption tower using the crude oil. A membrane separation device is connected to the top of the pre-absorption tower and is used to perform membrane separation treatment on the oil and gas that has not been absorbed in the pre-absorption tower to obtain organic oil and gas. An adsorption device includes a vacuum pump and at least two adsorption-desorption towers. The adsorption-desorption towers are used to adsorb the organic oil and gas. The vacuum pump is used to desorb and regenerate the adsorption-desorption towers when they reach saturation. The bottom of the adsorption-desorption towers is connected to the membrane separation device through an organic oil and gas pipeline and to the vacuum pump through a desorption pipeline. A desorption gas treatment device, connected to the vacuum pump, is used to treat the desorption gas obtained after desorption and regeneration; A desorption gas treatment device, connected to the vacuum pump, is used to treat the desorption gas obtained after desorption and regeneration; When the number of days with a maximum temperature ≥30℃ in the area where the oil depot is located is not less than 30 days per year, the desorbed gas treatment device is a gas-liquid separator. Alternatively, if the number of days with a maximum temperature ≥30℃ in the area where the oil depot is located is less than 30 days per year, the desorbed gas treatment device is an absorption tower.

2. The oil and gas recovery system as described in claim 1, characterized in that, At least one of the following conditions must be met: a. The top of the pre-absorption tower is connected to the membrane separation device via an outlet pipeline and to the oil depot via a return oil depot pipeline; b. The top of the pre-absorption tower is also equipped with a non-methane total hydrocarbon concentration meter to monitor the concentration of non-methane total hydrocarbons in the gas at the top of the pre-absorption tower; c. The pre-absorption tower is provided with trays and / or packing inside, and a wire mesh demister is provided above the trays and / or packing; d. The bottom of the pre-absorption tower is connected to the crude oil and gas in the underground water-sealed rock cavern oil depot via an air inlet pipe; e. The bottom of the pre-absorption tower is provided with a first rich oil outlet for discharging the rich oil after absorbing oil and gas.

3. The oil and gas recovery system as described in claim 2, characterized in that, It also meets at least one of the following conditions: f. The outlet pipeline and the return oil depot pipeline are each equipped with an independent shut-off valve; g. The air inlet pipeline is also equipped with a mixer and a blower. The mixer is used to mix the crude oil gas in the oil depot with the gas treated by the desorbed gas treatment device. The blower is used to pressurize the mixed gas in the mixer and send it into the pre-absorption tower. h. The oil inlet of the pre-absorption tower is located between the wire mesh demister and the tower plate and / or packing; i. The inlet of the pre-absorption tower is located between the first rich oil outlet and the tower plate and / or packing.

4. The oil and gas recovery system as described in claim 1, characterized in that, When the desorbed gas treatment device is an absorption tower, at least one of the following conditions must be met: j. The absorption tower is provided with a crude oil inlet for receiving crude oil from the oil depot and using the crude oil to absorb the desorbed gas; k. The top of the absorption tower is connected to the bottom of the pre-absorption tower via a gas recovery pipeline; 1. The bottom of the absorption tower is connected to the vacuum pump; m. The bottom of the absorption tower is provided with a second rich oil outlet.

5. The oil and gas recovery system as described in claim 1, characterized in that, When the desorbed gas treatment device is a gas-liquid separator, at least one of the following conditions must be met: n. A cryogenic cooler is also provided between the gas-liquid separator and the vacuum pump; o. The gas outlet of the gas-liquid separator is connected to the bottom of the pre-absorption tower; p. The liquid outlet of the gas-liquid separator is connected to the liquid hydrocarbon pipeline.

6. The oil and gas recovery system according to any one of claims 1-5, characterized in that, The tops of the membrane separation device and the adsorption-desorption tower are respectively connected to the exhaust pipe.

7. An oil and gas recovery method applied to an underground water-sealed rock cavern oil depot, characterized in that, include: The crude oil and crude oil gas from the oil depot are introduced into the pre-absorption tower respectively, and the crude oil is used to absorb the crude oil gas. The unabsorbed oil and gas in the pre-absorption tower are transported to the membrane separation unit, where organic oil and gas are obtained through membrane separation. The organic oil gas is introduced into the first adsorption-desorption tower of the adsorption device, which has not reached the saturation adsorption state, for adsorption. After the first adsorption-desorption tower reaches the saturation adsorption state, the organic oil gas is switched to the second adsorption-desorption tower, which has not reached the saturation adsorption state. Then, the first adsorption-desorption tower, which has reached the saturation adsorption state, is desorbed and regenerated by a vacuum pump to obtain desorbed gas. The desorbed gas is transported to a desorbed gas treatment device for desorbed gas recovery; When the number of days with a maximum temperature ≥30℃ in the area where the oil depot is located is not less than 30 days per year, the desorbed gas treatment device is a gas-liquid separator. Alternatively, if the number of days with a maximum temperature ≥30℃ in the area where the oil depot is located is less than 30 days per year, the desorbed gas treatment device is an absorption tower.

8. The oil and gas recovery method as described in claim 7, characterized in that, At least one of the following conditions must be met: q. When the crude oil is introduced into the absorption tower, the gauge pressure of the crude oil is 0.1 MPa - 0.2 MPa; r. When the crude oil gas is introduced into the absorption tower, the gauge pressure of the crude oil gas is 0.1 MPa - 0.2 MPa; s. After the crude oil and gas undergo dehydration and desulfurization, they are mixed with the desorbed gas and then introduced into the pre-absorption tower; The desorption and regeneration process includes: firstly, using the vacuum pump to evacuate the first adsorption-desorption tower to provide negative pressure; when the organic components on the adsorbent begin to desorb, introducing an inert gas into the first adsorption-desorption tower to maintain the vacuum pressure and perform vacuum cleaning to obtain a desorbed gas mixture of the organic components and the inert gas; then, pressurizing the desorbed gas with the vacuum pump and introducing it into the desorbed gas treatment device. u. When the desorbed gas treatment device is a gas-liquid separator, it includes: pre-cooling the crude oil using liquid hydrocarbons separated by the gas-liquid separator before introducing the crude oil into the pre-absorption tower.

9. The oil and gas recovery method as described in claim 7 or 8, characterized in that, Also includes: The top of the pre-absorption tower is equipped with a non-methane total hydrocarbon concentration meter. When the concentration value displayed on the non-methane total hydrocarbon concentration meter is greater than the set value, the unabsorbed oil and gas is transferred to the oil storage tank. When the concentration value is less than or equal to the set value, the unabsorbed oil and gas are then transferred to the membrane separation device.

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