Downhole radio frequency heating apparatus and method

Abstract

The application belongs to the technical field of oil and gas development, and discloses a downhole radio frequency heating device and method. The downhole radio frequency heating device comprises a radio frequency antenna, a heating control short section, a frequency modulation module and an oil production rate measuring instrument. The radio frequency antenna is placed in the wellbore of the reservoir area through the oil pipe and radiates electromagnetic waves outward to heat oil and gas. The heating control short section is arranged at the top of the radio frequency antenna and is electrically connected with the radio frequency antenna. The heating control short section is used for adjusting the working voltage of the radio frequency antenna. The frequency modulation module is connected between the ground power supply and the heating control short section, and is used for adjusting the frequency of the output current of the ground power supply to the heating frequency of the radio frequency antenna. The oil production rate measuring instrument is arranged at the top of the oil pipe and is used for measuring the oil production rate in real time. The application adopts the downhole radio frequency antenna heating mode for thermal recovery, solves the problem of excessive heating in a short distance or insufficient heating in a long distance existing in the radio frequency heating, and is beneficial to improving the thermal recovery efficiency.

Description

Technical Field

[0001] This invention relates to the field of oil and gas development technology, and in particular to a downhole radio frequency heating device and method. Background Technology

[0002] Statistics show that global heavy oil and bitumen reserves account for more than half of the world's oil reserves, possessing broad development and utilization prospects. However, their high viscosity and poor fluidity hinder the efficient development of these abundant unconventional resources. Because crude oil viscosity is sensitive to temperature, thermal recovery methods are primarily used in oilfields.

[0003] Currently, the most widely used technologies include steam injection, steam drive, and steam-assisted gravity drainage (SAGD). However, these conventional downhole thermal recovery technologies are unsuitable for exploiting low-permeability, deep, and thin oil layers. They also suffer from significant heat losses in pipelines, wellbores, and non-reservoir areas, resulting in low extraction efficiency and high costs. Especially in the context of low oil prices in the international environment, many oil companies experienced losses. Therefore, the development of new and efficient viscosity-reducing technologies is urgently needed.

[0004] Radio frequency (RF) heating, with its advantages of being clean, low-carbon, and highly efficient, has become one of the key technologies for the future development of unconventional oil and gas resources such as heavy oil and asphalt. Downhole RF antennas radiate electromagnetic waves into the reservoir after being supplied with an alternating current of a certain frequency. Due to the absorption of these electromagnetic waves by the reservoir, some of the electromagnetic energy is converted into heat energy, causing a decrease in the viscosity of the crude oil within the reservoir. Compared with traditional downhole steam thermal recovery technology, which mainly relies on heat conduction, RF heating technology also has the advantage of simultaneously heating both the inside and outside of the reservoir, and features rapid heating and volumetric heating. However, RF heating may suffer from overheating or underheating, therefore, there is an urgent need for RF heating control devices and methods tailored to the specific characteristics of the reservoir. Summary of the Invention

[0005] The purpose of this invention is to provide a downhole radio frequency heating device and method to solve the problems of overheating over short distances or insufficient heating over long distances in radio frequency heating.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] This invention first provides a downhole radio frequency heating device, comprising:

[0008] A radio frequency antenna is placed inside the wellbore in the reservoir area through an oil pipe and radiates electromagnetic waves to heat oil and gas.

[0009] A heating control section is provided at the top of the radio frequency antenna and electrically connected to the radio frequency antenna. The heating control section is used to adjust the operating voltage of the radio frequency antenna.

[0010] A frequency modulation module is connected between the ground power supply and the heating control section. The frequency modulation module is used to adjust the frequency of the output current of the ground power supply to the heating frequency of the radio frequency antenna.

[0011] An oil production rate measuring instrument is installed at the top of the oil pipe to measure the oil production rate in real time.

[0012] Optionally, the radio frequency antenna includes:

[0013] The antenna housing has a sealed bottom and an electrically insulating short section at the top opening for sealing, and the heating control short section is mounted on the electrically insulating short section.

[0014] The lower antenna is located inside the antenna housing. The top of the lower antenna has a lower antenna terminal, and the lower antenna single-stage power supply connection line is connected to the lower antenna terminal.

[0015] An inter-antenna electrical insulating block is disposed at the top of the lower antenna. The inter-antenna electrical insulating block has a first inner hole, and the single-stage power supply connection line of the lower antenna passes through the first inner hole.

[0016] An upper antenna is located at the top of the electrical insulating block between the antennas. The upper antenna has a second inner hole. The single-stage power supply connection line of the lower antenna passes through the second inner hole. The top of the upper antenna is provided with an upper antenna terminal, and the single-stage power supply connection line of the upper antenna is connected to the upper antenna terminal.

[0017] An antenna power supply connection accessory is provided at the top of the upper antenna. The antenna power supply connection accessory has a third inner hole. The lower antenna single-stage power supply connection line and the upper antenna single-stage power supply connection line both pass through the third inner hole and are connected to the antenna power supply line. The antenna power supply line is connected to the heating control section.

[0018] Optionally, the radio frequency antenna further includes:

[0019] A lower antenna stabilizer is disposed between the lower antenna and the antenna housing to fix the lower antenna.

[0020] An upper antenna stabilizer is disposed between the upper antenna and the antenna housing to fix the upper antenna.

[0021] Optionally, the inter-antenna electrical insulating block includes a base and a guide rod, the first inner hole penetrates the base and the guide rod, the base sits on the top of the lower antenna and is connected to the lower antenna, and the guide rod is inserted into the second inner hole and aligned with the top of the upper antenna.

[0022] Optionally, the antenna power supply connection accessory includes a plug-in part and a positioning part, the third inner hole passes through the plug-in part and the positioning part, the plug-in part is inserted into the first inner hole and abuts against the lower antenna, the electrically insulating short section is connected to the antenna housing and abuts against the positioning part, and the antenna power supply line is connected to the lower antenna single-stage power supply connection line and the upper antenna single-stage power supply connection line at the positioning part.

[0023] Optionally, the radio frequency antenna further includes a filler material that fills the space between the lower antenna and the antenna housing, and between the upper antenna and the antenna housing, and is sealed by the electrically insulating short section.

[0024] Optionally, the downhole radio frequency heating device further includes a measuring section, which is located at the top of the radio frequency antenna, and a heating control section is located on the measuring section. The measuring section is used to measure the dielectric constant of the reservoir region.

[0025] The present invention also provides a downhole radio frequency heating method using the aforementioned downhole radio frequency heating device, comprising the following steps:

[0026] S1, During initial oil production, the radio frequency antenna is placed in the wellbore in the reservoir area, the initial heating frequency f1 of the radio frequency antenna is set, and thermal production is carried out;

[0027] S2, measure the oil production rate in real time and compare the oil production rate with the rate threshold;

[0028] S3, if the oil production rate is lower than the rate threshold, then reduce the initial heating frequency f1 to the current heating frequency f. n Then continue thermal extraction, proceed to step S2, until extraction is complete.

[0029] Optionally, the initial heating frequency is reduced in a segmented manner, and the current heating frequency f n The following condition is satisfied between the initial heating frequency f1 and the initial heating frequency f1: n =f1-nδ, where n is the number of times the initial heating frequency is reduced, and δ is the heating frequency difference.

[0030] Optionally, during the thermal recovery process, a measuring subsection measures the dielectric constant ε of the reservoir region and, based on the current heating frequency f... n The electromagnetic wavelength λ of the radio frequency antenna is obtained. n :

[0031]

[0032] Where c is the speed of light in a vacuum;

[0033] According to the electromagnetic wavelength λ n The heating frequency difference δ is adjusted so that the radio frequency antenna heats a specified range within the reservoir area.

[0034] The beneficial effects of this invention are:

[0035] The downhole radio frequency heating device of the present invention includes a radio frequency antenna, which is placed in the wellbore in the reservoir area through the tubing to radiate electromagnetic waves outward, thereby heating the oil and gas in the reservoir area to achieve thermal recovery. By setting a heating control sub and a frequency modulation module, the operating voltage and heating frequency of the radio frequency antenna can be adjusted. By setting an oil production rate measuring instrument, the oil production rate of thermal recovery can be measured in real time, and the heating frequency can be adjusted according to the oil production rate, achieving effective control of the heating frequency of the radio frequency antenna. Because a lower heating frequency results in a longer wavelength of electromagnetic waves and a longer propagation distance, the electromagnetic energy loss within the reservoir area is smaller (most of the electromagnetic energy loss is converted into heat energy), and less heat energy is converted from electromagnetic energy. This prevents overheating in the nearby reservoir area, but prolonged heating increases the amount of heat energy converted from electromagnetic energy, raising the temperature of the reservoir at a greater distance, thus allowing crude oil in the more distant reservoir to be extracted, increasing the oil production rate. This effectively avoids the problems of overheating in the short distance or insufficient heating at a long distance that exist with radio frequency heating, and is beneficial to improving thermal recovery efficiency.

[0036] The downhole radio frequency heating method of the present invention adjusts the current heating frequency of the radio frequency antenna by measuring the oil production rate in real time, and then adjusts the radiation heating range by reducing the heating frequency. This can prevent overheating in short distances and achieve heating over long distances by extending the heating time, thereby improving thermal recovery efficiency. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structure of the downhole radio frequency heating device provided in an embodiment of the present invention;

[0038] Figure 2 This is a schematic diagram of the structure of the radio frequency antenna in the downhole radio frequency heating device provided in an embodiment of the present invention;

[0039] Figure 3 This is a schematic diagram of the structure of the inter-antenna electrical insulation block in the radio frequency antenna provided in an embodiment of the present invention;

[0040] Figure 4 This is a schematic diagram of the upper antenna structure in the radio frequency antenna provided in an embodiment of the present invention;

[0041] Figure 5 This is a schematic diagram of the antenna power supply connection accessory in the radio frequency antenna provided in an embodiment of the present invention.

[0042] In the picture:

[0043] 100. Oil pipe; 101. Oil pump; 1011. Oil pump power supply line; 102. Oil outlet; 103. Oil outlet pipeline; 104. Oil storage equipment; 200. Ground power supply; 201. Power cord;

[0044] 1. Radio frequency antenna; 2. Heating control section; 21. Antenna power supply line; 3. Frequency modulation module; 4. Oil production rate measuring instrument; 5. Measurement section; 51. Signal line; 6. Software module; 11. Antenna housing; 111. Electrically insulated section; 12. Lower antenna; 121. Lower antenna terminal block; 122. Lower antenna single-stage power supply connection line; 13. Inter-antenna electrical insulation block; 131. First inner hole; 132. Base; 133. Guide rod; 14. Upper antenna; 141. Second inner hole; 142. Upper antenna terminal block; 143. Upper antenna single-stage power supply connection line; 15. Antenna power supply connection accessory; 151. Third inner hole; 152. Plug-in part; 153. Positioning part; 16. Lower antenna straightener; 17. Upper antenna straightener; 18. Filler. Detailed Implementation

[0045] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0046] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0047] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0048] In the description of this embodiment, the terms "upper," "lower," "left," and "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0049] This invention provides a downhole radio frequency heating device, such as... Figure 1 As shown, the downhole radio frequency heating device includes a radio frequency antenna 1, a heating control sub 2, a frequency modulation module 3, and an oil production rate measuring instrument 4. The radio frequency antenna 1 is placed in the wellbore in the reservoir area through the tubing 100 to radiate electromagnetic waves to heat the oil and gas. The heating control sub 2 is located at the top of the radio frequency antenna 1 and is electrically connected to the radio frequency antenna 1. The heating control sub 2 is used to adjust the operating voltage of the radio frequency antenna 1. The frequency modulation module 3 is connected between the surface power supply 200 and the heating control sub 2. The frequency modulation module 3 is used to adjust the frequency of the output current of the surface power supply 200 to the heating frequency of the radio frequency antenna 1. The oil production rate measuring instrument 4 is located at the top of the tubing 100 and is used to measure the oil production rate in real time.

[0050] The downhole radio frequency heating device of the present invention includes a radio frequency antenna 1, which is placed in the wellbore in the reservoir area through an oil pipe 100 to radiate electromagnetic waves outward, thereby heating the oil and gas in the reservoir area to achieve thermal recovery. Changing the heating frequency of the radio frequency antenna 1 changes the wavelength of the electromagnetic waves, thereby adjusting and controlling the heating range of the reservoir area. Therefore, in this embodiment of the invention, by setting a heating control sub-section 2 and a frequency modulation module 3, the operating voltage and heating frequency of the radio frequency antenna 1 can be adjusted to achieve adjustment and control of the thermal recovery range. By setting an oil production rate measuring instrument 4, the oil production rate of thermal recovery can be measured in real time, and the heating frequency can be adjusted according to the oil production rate to ensure that the required oil production rate is provided, improve thermal recovery efficiency, provide a basis for adjusting the heating frequency of the radio frequency antenna 1, and perform effective control. Because the lower the heating frequency, the longer the wavelength of the electromagnetic wave, and the farther the propagation distance, the less electromagnetic energy loss occurs in the reservoir area (most of the electromagnetic energy loss is converted into heat energy). The less heat energy is converted from electromagnetic energy, the less overheating will occur in the nearby reservoir area. However, prolonged heating will increase the amount of heat energy converted from electromagnetic energy, increase the temperature of the reservoir at a distance, and thus allow the crude oil in the distant reservoir to be extracted, increasing the oil production rate. Therefore, the downhole radio frequency heating device provided in this embodiment of the invention can effectively avoid the problems of overheating in the short distance or insufficient heating in the long distance that exist in radio frequency heating, which is conducive to improving thermal recovery efficiency.

[0051] It should be noted that, for example Figure 1 As shown, an oil pump 101 is installed on the oil pipe 100. The oil pump 101 is fixed between the heating control section 2 and the oil pipe 100. The oil pump 101 is connected to the ground power supply 200 through the oil pump power supply line 1011. The ground part of the oil pipe 100 has an oil outlet 102, which is connected to an oil outlet pipeline 103. The oil outlet pipeline 103 connects the oil outlet 102 of the oil pipe 100 and the oil storage device 104. The oil production rate measuring instrument 4 is installed on the oil outlet pipeline 103 to measure the oil production rate in the oil outlet pipeline 103 and record and upload it as the oil production rate of thermal recovery, providing a reference for the adjustment of radio frequency heating frequency and wavelength. After the oil pump 101 is powered, it can pump crude oil to the oil outlet 102, then flow through the oil production rate measuring instrument 4 and the oil outlet pipeline 103, and finally be collected in the oil storage device 104. If, after the radio frequency antenna 1 has been performing thermal extraction at the current heating frequency for a period of time, the oil extraction rate drops to the minimum set threshold, the heating frequency needs to be reduced to increase the thermal extraction range. The ground power supply 200 is connected to the frequency modulation module 3 via power cable 201. The frequency modulation module 3 is connected to the heating control sub-section 2 via antenna power supply cable 21.

[0052] Optionally, the downhole radio frequency heating device also includes a measuring section 5, which is located at the top of the radio frequency antenna 1, and a heating control section 2 is located on the measuring section 5. The measuring section 5 is used to measure the dielectric constant of the reservoir region.

[0053] like Figure 1 As shown, the reservoir node constant measurement module is installed inside the measuring section 5, which can measure the dielectric constant of the reservoir in real time at different heating stages. It is connected to the software module 6 on the ground through the signal line 51. The software module 6 has a built-in calculation model to receive the dielectric constant collected by the measuring section 5, and calculates the electromagnetic wavelength in the reservoir area by using the dielectric constant and the current heating frequency of the radio frequency antenna 1, so as to provide a reference for the adjustment of the heating frequency.

[0054] Optionally, the RF antenna 1 includes an antenna housing 11, a lower antenna 12, an inter-antenna electrical insulation block 13, an upper antenna 14, and an antenna power supply connection accessory 15. The bottom of the antenna housing 11 is sealed, and the top is open and has an electrical insulation short section 111 for sealing. A measuring short section 5 is installed on the electrical insulation short section 111, and a heating control short section 2 is installed on the measuring short section 5. The electrical insulation short section 111 achieves insulation isolation between the measuring short section 5 and the RF antenna 1. The electrical insulation short section 111 is threadedly connected and fixed to the antenna housing 11, and the lower antenna 12, the inter-antenna electrical insulation block 13, the upper antenna 14, and the antenna power supply connection accessory 15 are sequentially pressed and fixed inside the antenna housing 11. The lower antenna 12 is located inside the antenna housing 11. The top of the lower antenna 12 has a lower antenna terminal 121, to which a single-stage power supply connection line 122 is connected. An inter-antenna electrical insulating block 13 is located at the top of the lower antenna 12. The inter-antenna electrical insulating block 13 has a first inner hole 131 through which the single-stage power supply connection line 122 passes. The upper antenna 14 is located at the top of the inter-antenna electrical insulating block 13. The upper antenna 14 has a second inner hole 141, through which the single-stage power supply connection line 122 passes. Wiring 122 passes through the second inner hole 141. The top of the upper antenna 14 is provided with an upper antenna terminal 142, and the upper antenna terminal 142 is connected to the upper antenna single-stage power supply connection line 143. The antenna power supply connection accessory 15 is provided at the top of the upper antenna 14. The antenna power supply connection accessory 15 has a third inner hole 151. The lower antenna single-stage power supply connection line 122 and the upper antenna single-stage power supply connection line 143 both pass through the third inner hole 151 and are connected to the antenna power supply line 21. The antenna power supply line 21 is connected to the heating control section 2.

[0055] like Figures 1-4As shown, the lower antenna 12 and the upper antenna 14 are housed within the antenna housing 11, which provides protection. The lower antenna 12 is a solid cylindrical structure. Its top end is connected to the lower antenna single-stage power supply line 122 via a lower antenna terminal 121, enabling electrical connection with the heating control section 2. This allows the heating control section 2 and the frequency modulation module 3 to apply operating voltage and heating frequency to the lower antenna 12. The upper antenna 14 is a cylindrical structure with a second inner hole 141. The upper antenna terminal 142 is located at its top end and connected to the upper antenna single-stage power supply line 143, enabling electrical connection with the heating control section 2. This also allows the heating control section 2 and the frequency modulation module 3 to apply operating voltage and heating frequency to the upper antenna 14.

[0056] Optionally, the radio frequency antenna 1 also includes a lower antenna stabilizer 16 and an upper antenna stabilizer 17. The lower antenna stabilizer 16 is disposed between the lower antenna 12 and the antenna housing 11 to fix the lower antenna 12; the upper antenna stabilizer 17 is disposed between the upper antenna 14 and the antenna housing 11 to fix the upper antenna 14.

[0057] Optionally, the inter-antenna electrical insulating block 13 includes a base 132 and a guide rod 133. A first inner hole 131 passes through the base 132 and the guide rod 133. The base 132 sits on the top of the lower antenna 12 and is connected to the lower antenna 12. The guide rod 133 is inserted into the second inner hole 141 and aligned with the top of the upper antenna 14.

[0058] like Figure 3 As shown, the base 132 and guide rod 133 are an integral structure. The outer diameters of the base 132 and guide rod 133 are different, thus forming a stepped surface between their outer walls. During installation, the base 132 abuts against the top of the lower antenna 12, and the upper antenna 14 is fitted with the guide rod 133, with its bottom end abutting against the stepped surface for positioning. It can be understood that the length of the upper antenna 14 is equal to the length of the guide rod 133 to facilitate assembly and positioning. The electrical insulation block 13 between the antennas provides electrical insulation between the lower antenna 12 and the upper antenna 14, preventing short circuits and ensuring that the lower antenna 12 and the upper antenna 14 can successfully radiate electromagnetic waves to the oil and gas reservoir.

[0059] Optionally, the antenna power supply connection accessory 15 includes a plug-in part 152 and a positioning part 153. A third inner hole 151 passes through the plug-in part 152 and the positioning part 153. The plug-in part 152 is inserted into the first inner hole 131 and abuts against the lower antenna 12. The electrically insulating short section 111 is connected to the antenna housing 11 and abuts against the top of the positioning part 153. The antenna power supply line 21 is connected to the lower antenna single-stage power supply connection line 122 and the upper antenna single-stage power supply connection line 143 in the positioning part 153.

[0060] like Figure 2 and Figure 5The connector 152 is inserted from top to bottom into the first inner hole 131 and abuts against the top of the lower antenna 12, so that the lower antenna terminal 121 and the lower antenna single-stage power supply connection line 122 are confined within the third inner hole 151 and connected to the antenna power supply line 21. This ensures the insulation protection of the electrical connection and provides electrical isolation to prevent the electromagnetic waves radiated by the lower antenna 12 and the upper antenna 14 from affecting the electrical connection. Figure 5 As shown, the insertion part 152 and the positioning part 153 are an integral structure. The outer diameters of the insertion part 152 and the positioning part 153 are different, thus forming a stepped surface. During installation, the top of the upper antenna 14 and the electrical insulation block 13 between the antennas both abut against this stepped surface to achieve a tight and sealed installation. The upper antenna terminal 142 and the upper antenna single-stage power supply connection line 143 provided at the top of the upper antenna 14 are both connected to the antenna power supply line 21 at the positioning part 153. It can be understood that, in order to facilitate the connection of the upper antenna single-stage power supply connection line 143, a through hole can be provided on the stepped surface of the positioning part 153 to facilitate the passage of the upper antenna single-stage power supply connection line 143. A groove is provided on the end face of the positioning part 153 opposite to the insertion part 152 to facilitate the installation and connection of the antenna power supply line 21.

[0061] Optionally, the RF antenna 1 further includes a filler 18, which fills the space between the lower antenna 12 and the antenna housing 11, and between the upper antenna 14 and the antenna housing 11, and is sealed by an electrically insulating short section 111. The filler 18 is made of a high-temperature resistant material to ensure the normal operation of the RF antenna 1 and to ensure electrical insulation between the RF antenna 1 and the upper measuring short section 5, preventing short circuits and eliminating the influence of the electromagnetic waves of the RF antenna 1 on the normal operation of the measuring short section 5. In addition, the electrically insulating short section 111 is hollow inside for the antenna power supply line 21 to pass through and be led out.

[0062] This invention also provides a downhole radio frequency heating method using the above-mentioned downhole radio frequency heating device, comprising the following steps:

[0063] S1, During initial oil production, the radio frequency antenna 1 is placed in the wellbore in the reservoir area, the initial heating frequency f1 of the radio frequency antenna 1 is set, and thermal production is carried out;

[0064] Generally, a higher heating frequency f1 is used for the initial heating. Due to the early heating, the reservoir around the radio frequency antenna 1 is rich in oil and gas. At the same time, due to the higher heating frequency and shorter wavelength, the electromagnetic energy loss in the reservoir is greater (most of the electromagnetic energy loss is converted into heat energy). The more heat energy is converted from electromagnetic energy, the more crude oil flows to the wellbore, and therefore the oil production rate is greater.

[0065] S2, measures the oil production rate in real time and compares the oil production rate with the rate threshold;

[0066] The rate threshold can be preset according to the actual situation, and is generally a range of values. When using high-frequency continuous heating, the electromagnetic wave wavelength is short, and the heat energy is concentrated in a short area. The reservoir at a distance does not absorb the heat energy and the temperature does not rise. Therefore, the oil production rate gradually decreases in the later stage of high-frequency heating, and it may also cause overheating, which leads to a decrease in reservoir porosity and a significant decrease in oil production rate.

[0067] S3, if the oil production rate is lower than the rate threshold, then reduce the initial heating frequency f1 to the current heating frequency f. n Then continue thermal extraction, proceed to step S2, until extraction is complete.

[0068] The reason for increasing the oil recovery rate by lowering the radio frequency heating frequency is that the lower the heating frequency, the longer the wavelength of the electromagnetic wave. Although the propagation distance is longer, the electromagnetic energy loss within the reservoir is smaller (most of the electromagnetic energy loss is converted into heat energy). The less heat energy is converted from electromagnetic energy, the less overheating will occur in the nearby reservoir area. However, prolonged heating will increase the amount of heat energy converted from electromagnetic energy, increase the temperature of the reservoir at a greater distance, and thus the crude oil in the more distant reservoir will be extracted, thereby increasing the oil recovery rate.

[0069] The downhole radio frequency heating method of the present invention adjusts the current heating frequency of the radio frequency antenna 1 by measuring the oil production rate in real time, and then adjusts the radiation heating range by reducing the heating frequency. This can both prevent overheating in short distances and achieve heating in long distances by extending the heating time, thereby improving thermal recovery efficiency.

[0070] Optionally, the initial heating frequency is reduced in a segmented manner, and the current heating frequency f n The following relationship is satisfied with the initial heating frequency f1: n =f1-nδ, where n is the number of times the initial heating frequency is reduced, and δ is the difference in heating frequency.

[0071] The heating frequency difference δ is an empirical value given based on the relationship between heating frequency and oil production rate. Generally, a small value can be selected so that the heating frequency is reduced in stages for easy control. In actual thermal recovery, in the early stage, due to the abundance of oil and gas in the reservoir, the heating frequency is reduced by a larger heating frequency difference δ each time. In the middle and later stages, because heating over a greater distance is required, a smaller heating frequency difference δ is used to reduce the heating frequency multiple times to avoid overheating, which is beneficial to improving the oil production rate.

[0072] Optionally, during the thermal recovery process, the dielectric constant ε of the reservoir region is measured in section 5, and adjusted according to the current heating frequency f. n Obtain the electromagnetic wavelength λ of the radio frequency antenna n :

[0073]

[0074] Where c is the speed of light in a vacuum;

[0075] According to electromagnetic wavelength λ n Adjusting the heating frequency difference allows the radio frequency antenna to heat a specified area within the reservoir region.

[0076] It is understandable that the properties of the reservoir will change dynamically as heating proceeds. Calculating the electromagnetic wavelength by measuring the dielectric constant in section 5 helps to determine the actual heating range within the reservoir, facilitating the adjustment of the heating frequency and operating voltage. Based on the actual oil production process, the heating wavelength is adjusted in real time by regulating the heating frequency to achieve heating at the maximum distance and with the highest thermal energy. This means comprehensively considering both heating distance and heat output to achieve maximum heating distance and maximum heat release.

[0077] The downhole radio frequency heating method of the present invention satisfies the requirements of achieving maximum efficiency with low power consumption and meets the needs of low-carbon and green oil and gas development, providing technical support for the future integration and development of new energy power and oil and gas development technologies.

[0078] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A downhole radio frequency heating device, characterized in that, include: Radio frequency antenna (1), which is placed in the wellbore of the reservoir area through the oil pipe (100) and radiates electromagnetic waves to heat oil and gas; A heating control section (2) is provided at the top of the radio frequency antenna (1) and electrically connected to the radio frequency antenna (1). The heating control section (2) is used to adjust the operating voltage of the radio frequency antenna (1). Frequency modulation module (3), the frequency modulation module (3) is located between the ground power supply (200) and the heating control section (2), the frequency modulation module (3) is used to adjust the frequency of the output current of the ground power supply (200) to the heating frequency of the radio frequency antenna (1); By setting the heating control section (2) and the frequency modulation module (3), the operating voltage and heating frequency of the radio frequency antenna (1) can be adjusted to achieve the adjustment and control of the heat sampling range; The oil production rate measuring instrument (4) is located at the top of the oil pipe (100) and is used to measure the oil production rate in real time. It can then adjust the heating frequency according to the oil production rate to ensure that the required oil production rate is provided, improve the thermal recovery efficiency, provide a basis for adjusting the heating frequency of the radio frequency antenna (1), and perform effective control. The radio frequency antenna (1) includes: Antenna housing (11), the bottom of the antenna housing (11) is sealed, and the top opening is provided with an electrically insulating short section (111) for sealing, and the heating control short section (2) is installed on the electrically insulating short section (111); The lower antenna (12) is located inside the antenna housing (11). The top of the lower antenna (12) has a lower antenna terminal (121), and the lower antenna terminal (121) is connected to the lower antenna single-stage power supply connection line (122). An inter-antenna electrical insulating block (13) is disposed at the top of the lower antenna (12). The inter-antenna electrical insulating block (13) has a first inner hole (131). The single-stage power supply connection line (122) of the lower antenna passes through the first inner hole (131). An upper antenna (14) is located at the top of the inter-antenna electrical insulating block (13). The upper antenna (14) has a second inner hole (141). The lower antenna single-stage power supply connection line (122) passes through the second inner hole (141). The top of the upper antenna (14) is provided with an upper antenna terminal (142). The upper antenna terminal (142) is connected to the upper antenna single-stage power supply connection line (143). Antenna power supply connection accessory (15) is provided at the top of the upper antenna (14). The antenna power supply connection accessory (15) has a third inner hole (151). The lower antenna single-stage power supply connection line (122) and the upper antenna single-stage power supply connection line (143) are both passed through the third inner hole (151) and connected to the antenna power supply line (21). The antenna power supply line (21) is connected to the heating control section (2). A measuring section (5) is provided at the top of the radio frequency antenna (1), and a heating control section (2) is provided on the measuring section (5). The measuring section (5) is used to measure the dielectric constant of the reservoir region.

2. The downhole radio frequency heating device according to claim 1, characterized in that, The radio frequency antenna (1) also includes: A lower antenna stabilizer (16) is disposed between the lower antenna (12) and the antenna housing (11) to fix the lower antenna (12); An upper antenna stabilizer (17) is disposed between the upper antenna (14) and the antenna housing (11) to fix the upper antenna (14).

3. The downhole radio frequency heating device according to claim 2, characterized in that, The inter-antenna electrical insulating block (13) includes a base (132) and a guide rod (133). The first inner hole (131) passes through the base (132) and the guide rod (133). The base (132) sits on the top of the lower antenna (12) and is connected to the lower antenna (12). The guide rod (133) is inserted into the second inner hole (141) and aligned with the top of the upper antenna (14).

4. The downhole radio frequency heating device according to claim 3, characterized in that, The antenna power supply connection accessory (15) includes a plug-in part (152) and a positioning part (153). The third inner hole (151) passes through the plug-in part (152) and the positioning part (153). The plug-in part (152) is inserted into the first inner hole (131) and abuts against the lower antenna (12). The electrically insulating short section (111) is connected to the antenna housing (11) and abuts against the positioning part (153). The antenna power supply line (21) connects the lower antenna single-stage power supply connection line (122) and the upper antenna single-stage power supply connection line (143) at the positioning part (153).

5. The downhole radio frequency heating device according to claim 3, characterized in that, The radio frequency antenna (1) also includes a filler (18) that fills the space between the lower antenna (12) and the antenna housing (11), and between the upper antenna (14) and the antenna housing (11), and is sealed by the electrically insulating short section (111).

6. A downhole radio frequency heating method, characterized in that, The downhole radio frequency heating device according to any one of claims 1-5, wherein the downhole radio frequency heating method comprises the following steps: S1, during initial oil production, the radio frequency antenna (1) is placed in the wellbore in the reservoir area, the initial heating frequency f1 of the radio frequency antenna (1) is set, and thermal production is carried out; S2, measure the oil production rate in real time and compare the oil production rate with the rate threshold; S3, if the oil production rate is lower than the rate threshold, then reduce the initial heating frequency f1 to the current heating frequency f. n Then continue thermal extraction, proceed to step S2, until extraction is complete.

7. The downhole radio frequency heating method according to claim 6, characterized in that, The initial heating frequency is reduced in a segmented manner, and the current heating frequency f n The following condition is satisfied between the initial heating frequency f1 and the initial heating frequency f1: n =f1-nδ, where n is the number of times the initial heating frequency is reduced, and δ is the heating frequency difference.

8. The downhole radio frequency heating method according to claim 7, characterized in that, During the thermal recovery process, the measuring section (5) measures the dielectric constant ε of the reservoir region and, based on the current heating frequency f, n The electromagnetic wavelength of the radio frequency antenna (1) is obtained. : Where c is the speed of light in a vacuum; According to the electromagnetic wavelength Adjust the heating frequency difference δ so that the radio frequency antenna (1) heats a specified range within the reservoir area.

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