Low-energy consumption heat exchange system for crude oil heating

Abstract

The present invention belongs to the technical field of crude oil exploitation applications, and particularly relates to a low-energy consumption heat exchange system for crude oil heating. It includes a crude oil storage tank, an oil pipeline, a crude oil heater, and an expansion tank. A heat transfer fluid is provided in the expansion tank. The expansion tank is connected to the crude oil heater through a pipeline. The crude oil heater heats the crude oil in the crude oil storage tank and the oil pipeline through the heat transfer fluid. It also includes a heating device for heating the heat transfer fluid in the expansion tank. The heating device includes a heat storage device and a controlled oxidation device for casing gas. The present invention realizes the harmless utilization of casing gas by using the setting of high-temperature oxidation treatment of casing gas. At the same time, with the setting of a phase-change heat storage device, the heat energy can be better stored. Furthermore, even when the amount of casing gas is large and unstable, it can ensure the normal heating of crude oil. Thus, while solving the problem of casing gas, it also solves the problem of crude oil heating, achieving the purpose of low energy consumption and environmental protection treatment.

Description

Technical Field

[0001] The present invention belongs to the technical field of crude oil exploitation applications, and particularly relates to a low-energy consumption heat exchange system for crude oil heating. Background Art

[0002] For a long time, most of the crude oil exploited in China belongs to "three-high" crude oil (high wax content, high pour point, high viscosity), with poor fluidity at normal temperature. During the gathering and transportation and processing processes, heating and heat preservation are required. In the processes of oil production, gathering and transportation in oilfields, at least 20% of the energy consumption is used for crude oil heating and processing. Traditional technologies use methods such as burning coal, oil, natural gas, and electric heating to achieve crude oil heating, resulting in a large amount of energy consumption problems.

[0003] During the process of crude oil production in oilfields, many oil wells have no pipeline to transport crude oil, and vehicles are used to transport crude oil regularly. Therefore, near the installation of the well site, storage tanks with a volume of 40 - 50 m³ are installed to temporarily store the produced crude oil in the tanks, and the temperature of the crude oil needs to be maintained at 35 - 45 °C. Since the temperature of the crude oil in the storage tank drops quickly, especially in cold regions, the viscosity of the crude oil increases after cooling, resulting in inability to transport. Therefore, it is necessary to heat the crude oil in the storage tank.

[0004] During the process of oil exploitation, as the pressure of the natural gas dissolved in the oil decreases, it will separate from the crude oil. Part of the gas is pumped out by the oil pump together with the well fluid, and part of it enters the oil casing to form casing gas. The entry of natural gas increases the casing pressure, and too high casing pressure will force the dynamic liquid level to drop. When the dynamic liquid level drops to the pump suction inlet, the gas rushes into the deep well pump, resulting in gas invasion, reducing the pump efficiency, and in severe cases, gas locking occurs, causing the oil well to stop production.

[0005] Therefore, there are mainly three methods for treating casing gas: 1. Directly venting or igniting the flare at the well site. This method not only pollutes the environment but also wastes resources; 2. Adopting the method of transporting compressed natural gas (CNG) externally. That is, after the natural gas is pretreated such as dehydration, dehydrocarbonization (desulfurization is also required if containing sulfur), it is pressurized to 20 - 25 MPa by a compressor and filled and transported externally by a tank truck. The advantage of this method is that it does not require a pipeline, is flexible in operation, and can collect natural gas from short-cycle wells such as exploration wells and maintenance wells. However, due to the need for pretreatment equipment such as dehydration, dehydrocarbonization, and desulfurization, the device cost is high, and it is only economical for wells with a certain gas volume scale (5000 - 50000 cubic meters per day); 3. Installing a gas generator at the well site and using casing gas as fuel for power generation, which can directly supply power to the pumping units in the field or feed power into the grid. However, due to the unstable gas volume of casing gas and its rapid attenuation over the years, this method has great limitations. Therefore, how to effectively utilize casing gas and apply it to crude oil heating, so that not only the problem of energy consumption for crude oil heating is solved, but also the utilization of casing gas is convenient. Summary of the Invention

[0006] In view of the technical problems of resource waste caused by the above-mentioned crude oil heating and resource waste caused by the treatment of casing gas, the present invention provides an energy-efficient low-energy consumption heat exchange system for crude oil heating that comprehensively utilizes crude oil heating and casing gas, has low energy consumption and no pollution.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows: The present invention provides a low-energy consumption heat exchange system for crude oil heating, including a crude oil storage tank, an oil pipeline, a crude oil heater, and an expansion tank. A heat-conducting fluid is provided in the expansion tank. The expansion tank is connected to the crude oil heater through a pipeline. The crude oil heater heats the crude oil in the crude oil storage tank and the oil pipeline through the heat-conducting fluid. The system further includes a heating device for heating the heat-conducting fluid in the expansion tank. The heating device includes a heat storage device and a controllable oxidation device for casing gas. Among them, the heat storage device is a phase change type heat storage device, and the controllable oxidation device for casing gas is used to perform high-temperature oxidation treatment on the casing gas and provide heat to the heat storage device.

[0008] Preferably, the expansion tank is provided with heat exchange between the heat storage device and the controllable oxidation device for casing gas respectively.

[0009] Preferably, the system further includes an auxiliary heating device, and the auxiliary heating device is provided with heat exchange between the expansion tank and the heat storage device respectively.

[0010] Preferably, the auxiliary heating device is an air source heat pump heating device.

[0011] Preferably, the auxiliary heating device is an electric heating device.

[0012] Preferably, the auxiliary heating device is a solar heating device.

[0013] Preferably, the auxiliary heating device includes an air source heat pump heating device, an electric heating device, and a solar heating device, and the air source heat pump heating device, the electric heating device, and the solar heating device are connected in parallel.

[0014] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0015] 1. The present invention provides a low-energy consumption heat exchange system for crude oil heating. By using the setting of high-temperature oxidation treatment of casing gas, harmless utilization of casing gas is realized. At the same time, with the setting of the phase change type heat storage device, heat energy can be better stored. Furthermore, even when the amount of casing gas is large and unstable, normal heating of crude oil can be ensured. Thus, while solving the problem of casing gas, the problem of crude oil heating is also solved, achieving the purpose of low energy consumption and environmental protection treatment. Description of the Drawings

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0017] Figure 1 Structural schematic diagram of the low - energy - consumption heat - exchange system for crude oil heating provided for Embodiment 1;

[0018] Figure 2 Structural schematic diagram of the casing gas controllable oxidation device provided for Embodiment 1. Detailed implementation manners

[0019] In order to more clearly understand the above - mentioned objects, features, and advantages of the present invention, the following further describes the present invention in conjunction with the drawings and embodiments. It should be noted that, without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other.

[0020] In the following description, many specific details are set forth to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Therefore, the present invention is not limited by the specific embodiments disclosed in the following specification.

[0021] Embodiment 1, as Figure 1 shown, this embodiment aims to provide a heat - exchange system with low energy consumption that can simultaneously solve the problems of crude oil heating and casing gas utilization. For this purpose, the low - energy - consumption heat - exchange system for crude oil heating provided in this embodiment includes a crude oil storage tank, an oil pipeline, a crude oil heater, and an expansion tank. Among them, a heat - conducting fluid is provided in the expansion tank. The heat - conducting fluid can be water or heat - conducting oil. In this embodiment, the heat - conducting fluid is selected as heat - conducting oil. The crude oil heater is a heat exchanger. The expansion tank and the crude oil heater are connected through a pipeline. In this way, the crude oil in the oil pipeline exchanges heat with the heat - conducting oil through the crude oil heater, and its temperature meets the requirements for transportation. At the same time, the crude oil in the crude oil storage tank exchanges heat with the heat - conducting oil through the crude oil heater, and its temperature meets the requirements for storage. In this embodiment, considering that the heat - exchange pipelines of the crude oil storage tank and the oil pipeline cannot be the same and both pass through the crude oil heater for heat exchange, which may lead to an increase in the volume of the crude oil heater. Therefore, the heat - exchange pipeline of the crude oil storage tank directly passes through the expansion tank for heat exchange.

[0022] Considering that the heat of the heat-conducting fluid decreases after heat exchange, it is necessary to supplement heat to it. Therefore, the entire system also includes a heating device for heating the heat-conducting fluid in the expansion tank. Considering that the main component of the casing gas is natural gas and it has the characteristic of unstable gas volume, in this embodiment, the heating device includes a heat storage device and a controllable oxidation device for the casing gas. The purpose is to use the heat storage device to store heat and then exchange heat with the heat-conducting fluid in case of unstable casing gas. The controllable oxidation device for the casing gas mainly performs high-temperature oxidation on the casing gas, generating heat while discharging carbon dioxide and water. It is mainly an inverted U-shaped container. In the cavities on the two vertical sides of the container, there are heat storage ceramic beds filled. Each vertical side has a lift valve, and an inlet pipe and an outlet pipe are set on the lift valve. Only one of the inlet pipe and the outlet pipe of the lift valve is open. If the inlet pipe of the lift valve on one side is open, the outlet pipe of the lift valve on the other side is open. The inlet pipe is used for the entry of the casing gas, and the outlet pipe is used for discharging water and carbon dioxide. A combustion chamber is set at the top of the container, and a high-temperature gas outlet is set at its top. When in use, first preheat the ceramic packing bed on the side of the inlet pipe to 1000 °C by an electric heating method, then introduce the casing gas into the ceramic packing bed. The casing gas preheated by the ceramic packing bed enters the combustion chamber to undergo an oxidation reaction, and then passes through the heat storage ceramic bed on the other side and discharges low-temperature gas. The heat generated by the oxidation of the casing gas is stored in the heat storage ceramic bed on the side of the exhaust pipe for preheating the casing gas during the next reverse cycle to maintain the self-thermal balance of the system. The excess heat is discharged from the smoke outlet at the top of the combustion chamber in the form of high-temperature flue gas. And the excess heat is used to provide heat to the heat storage device.

[0023] Considering the instability of the starting volume and concentration of the casing gas, in this embodiment, the casing gas is first transported to a container to adjust its concentration, and at the same time, it also plays a role in stabilizing the output. At the same time, the heat storage device is a phase-change heat storage device, and a solid-liquid phase-change heat storage device is preferably used. The heat storage capacity of the phase-change heat storage device can be multiple times that of water under the same volume. In this way, using its energy storage can ensure effective heat exchange for a long time, and further ensure the stability of the system.

[0024] Considering the working process of the controllable oxidation device for the casing gas, in addition to being used for heat storage in the heat storage device, a large amount of heat is wasted. Therefore, heat exchange is provided between the expansion tank and the heat storage device and the controllable oxidation device for the casing gas respectively. In this way, during the working period of the controllable oxidation device for the casing gas, the heat generated by it is divided into two parts. One part is used for heat storage in the heat storage device, and the other part is used for heat exchange with the heat-conducting fluid.

[0025] Considering the problem of the attenuation of casing gas over the years, an auxiliary heating device is also provided. The auxiliary heating device is arranged for heat exchange between the expansion tank and the heat accumulator respectively. In this way, the auxiliary heating device can directly exchange heat with the heat-conducting fluid or supply heat to the heat accumulator to ensure the stability of the system. The auxiliary heating device can be an air-source heat pump heating device. The auxiliary heating device can be an electric heating device. The auxiliary heating device can also be a solar heating device.

[0026] In this embodiment, the auxiliary heating device includes an air-source heat pump heating device, an electric heating device and a solar heating device, and the air-source heat pump heating device, the electric heating device and the solar heating device are arranged in parallel.

[0027] In this way, five heating devices, namely the air-source heat pump heating device, the electric heating device, the solar heating device, the casing gas controllable oxidation device and the heat accumulator, are used to exchange heat with the heat-conducting fluid to ensure the stability of the heat exchange system, and further ensure production safety. The setting of the casing gas controllable oxidation device effectively realizes the effective utilization of casing gas with low cost and low environmental requirements.

[0028] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention in other forms. Any person skilled in the art may use the disclosed technical content to make changes or modifications into equivalent embodiments with equivalent changes and apply them to other fields. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention still belong to the protection scope of the technical solution of the present invention.

Claims

1. A low - energy - consumption heat - exchange system for crude oil heating, comprising a crude oil storage tank, an oil pipeline, a crude oil heater, and an expansion tank. There is heat - conducting fluid in the expansion tank. The expansion tank and the crude oil heater are connected in a circulating manner through a pipeline. The crude oil heater heats the crude oil in the oil pipeline through the heat - conducting fluid. After the heat - conducting fluid exchanges heat with the crude oil in the oil pipeline in the crude oil heater and cools down, it returns to the expansion tank to be heated and then enters the crude oil heater again to heat the crude oil to form a cycle. There is a heat - exchange pipeline in the crude oil storage tank, and the heat - exchange pipeline is connected in a circulating manner with the expansion tank. The heat - conducting fluid in the heat - exchange pipeline exchanges heat with the crude oil in the crude oil storage tank in the crude oil storage tank, cools down, and then returns to the expansion tank to be heated and then enters the crude oil storage tank again to heat the crude oil to form a cycle. It is characterized in that, It further includes a heating device for heating the heat-conducting liquid in the expansion tank. The heating device includes a heat storage device and a casing gas controllable oxidation device. Among them, the heat storage device is a phase-change type heat storage device, and the casing gas controllable oxidation device is used to perform high-temperature oxidation treatment on the casing gas and provide heat to the heat storage device.

2. The low - energy - consumption heat - exchange system for crude oil heating according to claim 1, characterized in that, The expansion tank is arranged for heat exchange between the heat storage device and the casing gas controllable oxidation device respectively.

3. The low - energy - consumption heat - exchange system for crude oil heating according to claim 1 or 2, characterized in that, It further includes an auxiliary heating device, and the auxiliary heating device is arranged for heat exchange between the expansion tank and the heat storage device respectively.

4. The low - energy - consumption heat - exchange system for crude oil heating according to claim 3, characterized in that, The auxiliary heating device is an air source heat pump heating device.

5. The low - energy - consumption heat - exchange system for crude oil heating according to claim 3, characterized in that, The auxiliary heating device is an electric heating device.

6. The low - energy - consumption heat - exchange system for crude oil heating according to claim 3, characterized in that, The auxiliary heating device is a solar heating device.

7. The low - energy - consumption heat - exchange system for crude oil heating according to claim 3, characterized in that, The auxiliary heating device includes an air source heat pump heating device, an electric heating device and a solar heating device, and the air source heat pump heating device, the electric heating device and the solar heating device are arranged in parallel.

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