A downhole porous media combustion heater

Abstract

This invention discloses a downhole porous medium combustion heater, comprising an inlet chamber shell, a combustion chamber shell, and an exhaust chamber shell. The inlet chamber shell, combustion chamber shell, and exhaust chamber shell each form an inlet chamber cavity, a combustion chamber cavity, and an exhaust chamber cavity, respectively. An air inlet is located at the top of the inlet chamber cavity, and a stainless steel wire mesh is installed at the top of the inlet chamber cavity. A first porous alumina straight-hole mesh gasket is installed at the bottom of the inlet chamber cavity. Porous alumina particles are filled between the stainless steel wire mesh and the first porous alumina straight-hole mesh gasket within the inlet chamber cavity. This invention overcomes the problems of low heating efficiency, short service life, and high energy consumption of traditional electrically heated downhole heaters, while also solving the technical bottlenecks of difficult control and low recovery rate of conventional combustion heaters. The device utilizes convective heat transfer to transfer heat to the reservoir, significantly improving the heat transfer rate and energy utilization efficiency.

Description

Technical Field

[0001] This invention relates to the field of downhole porous media combustion heating technology, specifically to a downhole porous media combustion heater. Background Technology

[0002] While unconventional oil and gas resources possess enormous reserves, their complex reservoir geological structures make traditional geological exploration and development theories and conventional oil and gas technologies difficult to apply directly. For unconventional oil and gas resources such as heavy oil, oil sands, extra-heavy oil, oil shale, and deep oil, downhole thermal injection has proven to be the most efficient development method. Therefore, developing specialized heaters adapted to complex downhole environments and meeting the needs of unconventional oil and gas extraction is of paramount importance for achieving efficient utilization of these resources.

[0003] Existing downhole heating technologies are mainly divided into two categories based on energy supply methods: electric heating and combustion heating. While electric heating technology is mature and easy to operate, encompassing various methods such as resistance heating, electromagnetic / infrared radiation heating, and high-voltage arc breakdown, it suffers from significant drawbacks including slow heating rates, low thermal efficiency, short lifespan of core components, and high energy consumption, making it difficult to meet the economic and long-term development needs of unconventional oil and gas reservoirs. In contrast, while combustion heating offers advantages in efficiency and speed, traditional in-situ ignition and combustion pyrolysis processes face technical bottlenecks such as uncontrollable reaction processes and the potential for secondary combustion of produced oil and gas resources, thus reducing recovery rates. In conclusion, traditional heating extraction methods are no longer adequate for the practical requirements of efficient and safe extraction of unconventional oil and gas resources.

[0004] In summary, existing downhole heating technologies are insufficient to meet the requirements for efficient development of unconventional oil and gas reservoirs. Therefore, developing a novel downhole combustion heater that utilizes the excellent heat storage properties of porous media and its characteristics as a catalyst carrier, based on the efficient catalytic combustion of low-calorific-value gases, heats the reservoir via convection, and possesses controllable reaction processes, is of significant theoretical and engineering application value for improving the efficiency of unconventional oil and gas resource extraction. Summary of the Invention

[0005] The present invention aims to provide a downhole porous medium combustion heater to effectively overcome the defects of existing electric heating technology, such as low heating efficiency, short component life and high operating energy consumption, while solving the key technical bottlenecks of traditional combustion heating technology, such as difficulty in controlling the reaction process and low oil and gas recovery rate.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a downhole porous medium combustion heater, comprising an inlet chamber shell, a combustion chamber shell, and an exhaust chamber shell, wherein an inlet chamber cavity, a combustion chamber cavity, and an exhaust chamber cavity are respectively formed inside the inlet chamber shell, the combustion chamber shell, and the exhaust chamber shell; an air inlet is provided at the top of the inlet chamber cavity, and a stainless steel wire mesh is provided at the top of the interior of the inlet chamber cavity; a first porous medium alumina straight hole mesh gasket is installed at the bottom of the interior of the inlet chamber cavity; and porous medium alumina granules are filled between the stainless steel wire mesh and the first porous medium alumina straight hole mesh gasket in the inlet chamber cavity. A high-energy igniter is symmetrically installed at the top of the inner wall of the combustion chamber, and a second porous alumina straight hole mesh gasket is installed below the high-energy igniter in the combustion chamber, and a third porous alumina straight hole mesh gasket is installed at the bottom of the combustion chamber. A porous media layer is provided between the second and third porous alumina straight hole mesh gaskets in the combustion chamber. The combustion chamber cavity is equipped with a first high-temperature resistant temperature sensor, a second high-temperature resistant temperature sensor, a third high-temperature resistant temperature sensor, a fourth high-temperature resistant temperature sensor, and a fifth high-temperature resistant temperature sensor, which are arranged alternately. The exhaust gas outlet is provided at the bottom of the exhaust gas chamber cavity.

[0007] Preferably, the air inlet is configured as a gas inlet channel, and the exhaust outlet is used to directly discharge the high-temperature exhaust gas generated by combustion in the combustion chamber.

[0008] Preferably, the quality control structure on the first porous alumina straight-hole mesh pad is uniformly distributed, and its mesh diameter is smaller than the particle size of the porous alumina particles.

[0009] Preferably, flanges are provided on the outer side of the bottom end of the intake chamber housing, the outer side of the top and bottom ends of the combustion chamber cavity, and the outer side of the top end of the exhaust gas chamber cavity. The intake chamber housing and the combustion chamber housing, as well as the combustion chamber housing and the exhaust gas chamber housing, are fixedly connected by the flanges.

[0010] Preferably, the high-energy igniter is connected to a cable at one end outside the combustion chamber cavity, and an ignition rod is provided at one end of the high-energy igniter located inside the combustion chamber cavity, with the end of the ignition rod extending into the combustion chamber cavity. The ignition rod is located above the second porous alumina straight hole mesh gasket. The outer side of the combustion chamber cavity is symmetrically provided with first threaded holes, and the outer side of the ignition rod is provided with an external thread that mates with the first threaded holes. The ignition rod is threadedly connected to the first threaded holes.

[0011] Preferably, the stainless steel wire mesh is fixedly connected to the inner wall of the air intake chamber by welding, and the corresponding cavity below the air intake is designed with an expanded capacity.

[0012] Preferably, the intake chamber shell, combustion chamber shell, and exhaust chamber shell are all made of stainless steel high-temperature resistant material, and the stainless steel high-temperature resistant material has high-temperature resistance of not less than ℃ and excellent compressive load-bearing capacity.

[0013] Preferably, the first, second, third, fourth, and fifth high-temperature resistant temperature sensors are connected to an electrical signal line at one end outside the combustion chamber cavity, and an alumina tube is connected to one end of each sensor located in the combustion chamber cavity. The alumina tubes at the ends of the first, second, third, fourth, and fifth high-temperature resistant temperature sensors extend into the porous medium layer. The alumina tube at the end of the fifth high-temperature resistant temperature sensor is located below the third porous medium alumina straight-hole mesh gasket. A second threaded hole is provided on the outer side of the combustion chamber cavity, and an external thread that mates with the second threaded hole is provided on the outer side of the alumina tube. The alumina tube and the combustion chamber cavity are connected by threads.

[0014] Preferably, the connections between the intake chamber housing and the combustion chamber housing, between the combustion chamber housing and the exhaust chamber housing, between the high-energy igniter and the combustion chamber cavity, and between the corundum tube and the combustion chamber cavity are all sealed with high-temperature resistant putty and high-temperature resistant tape.

[0015] Compared with existing technologies, the advantages of this invention are as follows: This invention uses downhole porous media combustion technology to achieve thermal recovery of the target reservoir, effectively overcoming the drawback of continuous high energy consumption of electric heating technology, consuming only a small amount of electrical energy during the ignition and temperature monitoring stages. Compared with traditional in-situ combustion reservoir processes, this device confines the combustion process within the heater by adjusting the gas parameters on the ground and uses convective heat transfer to transfer heat to the reservoir, which not only significantly improves the heat transfer rate and energy utilization efficiency but also has excellent process controllability. This technology can be widely applied to the in-situ extraction of unconventional oil and gas resources such as heavy oil, oil sands, extra-heavy oil, oil shale, and deep oil. Attached Figure Description

[0016] Figure 1 This is a cross-sectional view of the present invention. Figure 2 This is a schematic diagram of the overall structure of the present invention; Figure 3 This is an enlarged structural diagram of point A in the present invention; Figure 4 This is an enlarged structural schematic diagram of section B of the present invention; Figure 5 This is a top view structural diagram of the present invention; Figure 6 This is a bottom view structural diagram of the present invention.

[0017] In the diagram: 1. Air inlet; 2. Stainless steel wire mesh; 3. Air inlet chamber; 4. Porous alumina particles; 5. First porous alumina straight-hole mesh gasket; 6. Flange; 7. High-energy igniter; 71. Cable; 72. First threaded hole; 73. Ignition rod; 8. Second porous alumina straight-hole mesh gasket; 9. First high-temperature sensor; 10. Combustion chamber; 11. Porous medium layer; 12. Third porous alumina straight-hole mesh gasket; 13. Exhaust chamber; 14. Exhaust outlet; 15. Air inlet shell; 16. Combustion chamber shell; 17. Exhaust chamber shell; 18. Second high-temperature sensor; 19. Third high-temperature sensor; 20. Fourth high-temperature sensor; 21. Fifth high-temperature sensor; 22. Second threaded hole; 23. Corundum tube; 24. Electrical signal line. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Please see Figure 1 , Figure 2 , Figure 5 and Figure 6 The present invention provides a technical solution: a downhole porous medium combustion heater, comprising an air inlet chamber shell 15, a combustion chamber shell 16, and an exhaust gas chamber shell 17. The air inlet chamber shell 15, the combustion chamber shell 16, and the exhaust gas chamber shell 17 respectively form an air inlet cavity 3, a combustion chamber cavity 10, and an exhaust gas chamber cavity 13. An air inlet 1 is provided at the top of the air inlet cavity 3, and a stainless steel wire mesh 2 is provided at the top of the air inlet cavity 3. A first porous medium alumina straight hole mesh gasket 5 is installed at the bottom of the air inlet cavity 3. Porous medium alumina granules 4 are filled between the stainless steel wire mesh 2 and the first porous medium alumina straight hole mesh gasket 5 in the air inlet cavity 3. A high-energy igniter 7 is symmetrically installed at the top of the inner wall of the combustion chamber 10, and a second porous alumina straight hole mesh gasket 8 is installed below the high-energy igniter 7 inside the combustion chamber 10, and a third porous alumina straight hole mesh gasket 12 is installed at the bottom of the combustion chamber 10. A porous medium layer 11 is provided inside the combustion chamber 10 between the second porous alumina straight hole mesh gasket 8 and the third porous alumina straight hole mesh gasket 12. The combustion chamber cavity 10 is equipped with a first high-temperature resistant temperature sensor 9, a second high-temperature resistant temperature sensor 18, a third high-temperature resistant temperature sensor 19, a fourth high-temperature resistant temperature sensor 20, and a fifth high-temperature resistant temperature sensor 21, which are arranged alternately. The exhaust gas chamber cavity 13 is provided with an exhaust gas outlet 14 at the bottom.

[0020] It should be noted that, in this embodiment, the present invention provides a downhole porous media combustion heating technology device specifically for in-situ extraction of unconventional oil and gas resources such as heavy oil, oil sands, extra-heavy oil, oil shale, and deep oil. A stainless steel wire mesh 2 is welded and fixed inside the air inlet shell 15. The inner diameter of its air inlet 1 is significantly smaller than the inner diameter of the lower flow channel, forming a funnel-shaped structure. Porous alumina particles 4 are placed below the stainless steel wire mesh 2 and sealed and fixed by a first porous alumina straight-hole mesh gasket 5. The optimized thickness of the first porous alumina straight-hole mesh gasket 5 is approximately five millimeters. Both the porous alumina particles 4 and the first porous alumina straight-hole mesh gasket 5 possess heat resistance to withstand temperatures above 1000°C and excellent impact and pressure resistance. High-energy igniters 7 are symmetrically distributed on the left and right sides of the combustion chamber shell 16 via internal thread connections, maintaining a 3-5 cm staggered arrangement in the vertical direction, aiming to significantly improve the ignition success rate through multi-point coordinated ignition. The high-energy igniter 7 is connected via an external cable 71, and its ignition rod 73 is inserted into the combustion chamber cavity 10, and has the ability to withstand temperatures above 1300°C. In the fixing structure of the porous media layer 11, a second porous media alumina straight-hole mesh gasket 8 and a third porous media alumina straight-hole mesh gasket 12 are used to clamp the porous media layer 11 from top to bottom. The thickness of the third porous media alumina straight-hole mesh gasket 12 is designed to be 5-10 cm. This size optimization fully considers the gravity load during the downhole vertical deployment process, as well as the mechanical stability requirements under complex working conditions such as acoustic vibration, thermal stress, and thermal impulse during combustion operation. The filling porous media layer 11 material must have the ability to withstand high temperatures above 1000°C. Its morphology can be selected as granular, fibrous, or straight-hole according to requirements, and its heat storage characteristics are used to help maintain combustion stability. Alternatively, a porous media loaded with a noble metal catalyst can be used for catalytic combustion. When the medium is preheated to the ignition temperature, the gas can be introduced to trigger a high-efficiency reaction. In addition, a temperature sensor with a high temperature resistance of up to 1600°C is installed in the combustion chamber cavity 10. The sensor is fixed by a threaded connection, and its corundum tube 23 temperature measuring end is inserted into the porous media layer 11. Among them, the bottom temperature sensor is located below the third porous alumina straight hole mesh gasket 12, which has the dual function of monitoring exhaust gas temperature and supporting the internal structure. The sensor is connected to the ground monitoring device in real time through the electrical signal line 24. When the porous media layer 11 is loaded with a noble metal catalyst, its core function is to reduce the activation energy of combustible components in the fuel gas, significantly accelerate the chemical reaction rate, thereby improving the fuel gas conversion efficiency and effectively reducing the injection cost. If an inert porous media is used, the heat transfer process is enhanced mainly by strengthening the turbulence disturbance of the mixed gas, thereby improving the overall thermal efficiency of the heater. In addition, the porous media layer 11 can also rapidly homogenize the temperature field in the combustion zone, maintain a stable temperature gradient, and effectively suppress the formation of nitrogen oxides while reducing the local maximum combustion temperature.

[0021] In terms of assembly structure, the inner diameter of the flange 6 at the upper end of the combustion chamber shell 16 is smaller than the inner diameter of the flange 6 of the intake chamber shell 15. The stepped structure formed by this size difference can axially limit the first porous alumina straight hole mesh gasket 5 after installation, thereby effectively preventing the porous alumina particles 4 from falling into the combustion chamber cavity 10. The combustion chamber shell 16 is pre-installed with a first threaded hole 72 and a second threaded hole 22 for installing the high-energy igniter 7 and the first high-temperature resistant temperature sensor 9. The two high-energy igniters 7 are arranged alternately, with a vertical spacing of 3-5 cm to ensure ignition effectiveness. In addition, the ignition rod 73 of the high-energy igniter 7 and the corundum tube 23 of the first high-temperature resistant temperature sensor 9 must not be cut or bent during installation. The porous media layer 11 filled inside the combustion chamber cavity 10 can be made of inert material to achieve heat storage function, or a porous media catalyst can be used for catalytic combustion. The porous media bed is positioned at both the upper and lower ends of the combustion chamber shell 16 by a second porous media alumina straight hole mesh gasket 8 and a third porous media alumina straight hole mesh gasket 12. The outer diameter of the gasket should be tightly fitted with the inner diameter of the combustion chamber shell 16. The third porous media alumina straight hole mesh gasket 12 at the exhaust gas outlet 14 needs to have sufficient thickness, with a design range of 5-10 cm, to ensure structural stability. The exhaust chamber shell 17 is designed in a funnel shape to guide the high-temperature exhaust gas generated by combustion to the target reservoir via the exhaust outlet 14 through convective heat transfer. In terms of assembly structure, the inner diameter of the flange 6 of the exhaust chamber shell 17 is designed to be smaller than the inner diameter of the flange 6 of the combustion chamber shell 16.

[0022] Please see Figure 1 and Figure 2 The air inlet 1 is constructed as a gas inlet channel, and the exhaust outlet 14 is used to directly discharge the high-temperature exhaust gas generated by combustion in the combustion chamber cavity 10.

[0023] It should be noted that in this embodiment, when the gas backfires to the air inlet 1, a high-speed airflow field is formed by the small-diameter structure of the air inlet 1, thereby achieving dynamic suppression of the backfire phenomenon; the exhaust outlet 14 is used to directly discharge the high-temperature exhaust gas generated by combustion in the combustion chamber, and the high-temperature exhaust gas is used to heat the oil layer being extracted.

[0024] Please see Figure 1 The quality control structure on the first porous alumina straight hole mesh pad 5 is uniformly arranged and distributed, and its mesh diameter is smaller than the particle size of the porous alumina granules 4.

[0025] It should be noted that, in this embodiment, the porous alumina particles 4 have efficient heat storage characteristics. When the backfire gas flows through the porous alumina particles 4, the gas temperature can be quickly reduced to below its ignition point, thereby achieving forced extinguishing of the backfire gas. Alternatively, when the gas backfires to the inlet 1, a high-speed airflow field is formed by the small-diameter structure of the inlet 1, thereby achieving dynamic suppression of the backfire phenomenon. The first porous alumina straight-hole mesh gasket 5 is disposed at the bottom of the inner side of the inlet chamber shell 15. The quality control structure on the first porous alumina straight-hole mesh gasket 5 is uniformly distributed, and its mesh diameter is smaller than the particle size of the porous alumina particles 4, which is used to limit and block the porous alumina particles 4.

[0026] Please see Figure 2 Flanges 6 are provided on the outer side of the bottom end of the intake chamber housing 15, the outer side of the top and bottom ends of the combustion chamber cavity 10, and the outer side of the top end of the exhaust chamber cavity 13. The intake chamber housing 15 and the combustion chamber housing 16, and the combustion chamber housing 16 and the exhaust chamber housing 17 are all fixedly connected by flanges 6.

[0027] It should be noted that, in this embodiment, in terms of assembly and connection, the flange 6 on the intake chamber housing 15 and the flange 6 on the combustion chamber housing 16 are fastened with bolts and a high-temperature resistant putty is used for primary sealing. Then, high-temperature resistant tape is pasted at the sealing point to implement secondary sealing and reinforcement to ensure the airtightness of the device.

[0028] Please see Figure 1 and Figure 3 A high-energy igniter 7 is connected to a cable 71 at one end outside the combustion chamber cavity 10. An ignition rod 73 is provided at one end of the high-energy igniter 7 located outside the combustion chamber cavity 10, and the end of the ignition rod 73 extends into the combustion chamber cavity 10. The ignition rod 73 is located above the second porous medium alumina straight hole mesh gasket 8. A first threaded hole 72 is symmetrically opened on the outer side of the combustion chamber cavity 10. An external thread that mates with the first threaded hole 72 is provided on the outer side of the ignition rod 73. The ignition rod 73 is threadedly connected in the first threaded hole 72.

[0029] It should be noted that in this embodiment, the two high-energy igniters 7 are arranged in an alternating manner, with the vertical spacing controlled at 3-5cm to ensure the effectiveness of ignition. When installing the high-energy igniters 7, the high-energy igniters 7 are installed to the combustion chamber housing 16 by bolts. After installation, the second porous medium alumina straight hole mesh gasket 8 is placed until it touches the high-energy igniters 7.

[0030] Please see Figure 1 The stainless steel wire mesh 2 is fixedly connected to the inner wall of the air intake chamber 3 by welding process, and the corresponding cavity below the air intake 1 has an expanded design.

[0031] It should be noted that in this embodiment, the flow channel below the air inlet 1 adopts an enlarged diameter structure, which aims to increase the flow cross-sectional area and prevent backfire caused by the flame propagation speed being greater than the airflow speed by adjusting the flow field parameters.

[0032] Please see Figure 1 The intake chamber shell 15, combustion chamber shell 16 and exhaust chamber shell 17 are all made of stainless steel high temperature resistant material, and the stainless steel high temperature resistant material has a high temperature resistance of not less than 1200℃ and excellent compressive load-bearing capacity.

[0033] It should be noted that in this embodiment, the intake chamber housing 15, the combustion chamber housing 16, and the exhaust chamber housing 17 are all made of stainless steel high-temperature resistant material, which has excellent heat resistance and can withstand high temperature environments above 1200°C, while also having extremely high mechanical strength and pressure resistance.

[0034] Please see Figure 1 and Figure 4 The first high-temperature resistant temperature sensor 9, the second high-temperature resistant temperature sensor 18, the third high-temperature resistant temperature sensor 19, the fourth high-temperature resistant temperature sensor 20, and the fifth high-temperature resistant temperature sensor 21 are connected to an electrical signal line 24 at one end outside the combustion chamber cavity 10. A corundum tube 23 is connected to one end of each of these sensors. The corundum tube 23 at the ends of the first, second, third, and fourth high-temperature resistant temperature sensors 9, 18, 20, and 21 extends into the porous medium layer 11. The corundum tube 23 at the end of the fifth high-temperature resistant temperature sensor 21 is located below the third porous medium alumina straight-hole mesh gasket 12. A second threaded hole 22 is provided on the outer side of the combustion chamber cavity 10, and an external thread that mates with the second threaded hole 22 is provided on the outer side of the corundum tube 23. The corundum tube 23 and the combustion chamber cavity 10 are connected by threads.

[0035] It should be noted that, in this embodiment, when installing the first high-temperature resistant temperature sensor 9, the second high-temperature resistant temperature sensor 18, the third high-temperature resistant temperature sensor 19, and the fourth high-temperature resistant temperature sensor 20, regarding the filling of the porous media layer 11, if a rigid stopper with a straight hole, fiber, or foam structure is selected, holes need to be pre-drilled at the corresponding positions. Then, the porous media layer 11 is placed in, and the first high-temperature resistant temperature sensor 9, the second high-temperature resistant temperature sensor 18, the third high-temperature resistant temperature sensor 19, and the fourth high-temperature resistant temperature sensor 20 are inserted. At this time, it is necessary to confirm whether the corundum tube 23 is completely inserted into the combustion chamber cavity 10 and whether the external thread of the corundum tube 23 is screwed in place. If the installation is obstructed, the above steps need to be repeated. If a particulate porous media layer 11 is selected, the first high-temperature resistant temperature sensor 9, the second high-temperature resistant temperature sensor 18, the third high-temperature resistant temperature sensor 19, and the fourth high-temperature resistant temperature sensor 20 need to be completely inserted into the combustion chamber cavity 10 first, and then the porous media layer 11 is poured in. During the filling process, the shell is continuously shaken to ensure uniform filling. Subsequently, the third porous alumina straight hole mesh gasket 12 is laid on the uniformly filled porous medium layer 11, and the fifth high temperature sensor 21 is connected and fixed to the combustion chamber shell 16 through the external thread on the outside of the corundum tube 23.

[0036] Please see Figure 1 High-temperature resistant putty and high-temperature resistant tape are used to seal the connections between the intake chamber housing 15 and the combustion chamber housing 16, between the combustion chamber housing 16 and the exhaust chamber housing 17, between the high-energy igniter 7 and the combustion chamber cavity 10, and between the corundum tube 23 and the combustion chamber cavity 10.

[0037] It should be noted that in this embodiment, all connecting parts of the shell are sealed using a combination of high-temperature resistant putty and high-temperature resistant tape to ensure the airtightness of the device, thereby optimizing the combustion environment and significantly improving the reliability and safety of the heater operation.

[0038] The installation steps of this invention are as follows: First, invert the intake chamber housing 15 and fill it with a sufficient amount of porous alumina granules 4. Then, cover the granule layer with a first porous alumina straight hole mesh gasket 5. Connect the flanges 6 of the combustion chamber housing 16 and the exhaust chamber housing 17 with bolts. After connection, flip the assembly back to its original position and check for leaks in the porous alumina granules 4. If a leak is found, the flanges 6 need to be separated, readjusted, and reconnected. If the seal is good, invert the assembly again.

[0039] The high-energy igniter 7 is bolted to the combustion chamber housing 16. After installation, the second porous alumina straight-hole mesh gasket 8 is inserted until it touches the high-energy igniter 7. Regarding the filling of the porous medium layer 11, if a rigid structure such as straight-hole, fibrous, or foam is selected, holes need to be pre-drilled at the corresponding positions. Then, the porous medium layer 11 is inserted, and the first high-temperature resistant temperature sensor 9, the second high-temperature resistant temperature sensor 18, the third high-temperature resistant temperature sensor 19, and the fourth high-temperature resistant temperature sensor 20 are inserted. At this time, it is necessary to confirm whether the corundum tube 23 is fully inserted into the combustion chamber cavity 10 and whether the external thread of the corundum tube 23 is screwed in place. If the installation is obstructed, the above steps need to be repeated. If a particulate porous medium layer 11 is selected, the first high-temperature resistant temperature sensor 9, the second high-temperature resistant temperature sensor 18, the third high-temperature resistant temperature sensor 19, and the fourth high-temperature resistant temperature sensor 20 need to be fully inserted into the combustion chamber cavity 10 first, and then the porous medium layer 11 is poured in. During the filling process, the housing is continuously shaken to ensure uniform filling. Subsequently, the third porous alumina straight-hole mesh gasket 12 is laid on top of the uniformly filled porous media layer 11, and the fifth high-temperature resistant temperature sensor 21 is connected and fixed to the combustion chamber housing 16 through the external thread on the outside of the corundum tube 23. After the temperature sensor and porous media layer 11 assembly are installed and filled, the exhaust gas chamber housing 17 is connected to the combustion chamber housing 16. The entire device is flipped and reset, and it is checked whether the porous media layer 11 has fallen off inside the combustion chamber housing 16. If it has fallen off, the exhaust gas chamber housing 17 needs to be disassembled and the fifth high-temperature resistant temperature sensor 21 needs to be removed. It is then checked whether the third porous alumina straight-hole mesh gasket 12 is placed stably. If it has not fallen off, it indicates that the downhole porous media combustion heater has been successfully installed. Finally, high-temperature resistant putty and high-temperature resistant tape are used to perform secondary sealing and reinforcement treatment on the multiple connection seals on the heater housing.

[0040] The experimental process and operating methods of this invention are as follows: Connect the external gas pipeline tightly to the gas inlet 1, then vertically lower the heater into the target reservoir. During the lowering process, ensure that the cable 71 of the high-energy igniter 7 and the electrical signal lines 24 of the first high-temperature resistant temperature sensor 9, the second high-temperature resistant temperature sensor 18, the third high-temperature resistant temperature sensor 19, the fourth high-temperature resistant temperature sensor 20, and the fifth high-temperature resistant temperature sensor 21 are not tangled or worn. Introduce a specific ratio and flow rate of gas mixture from the ground, start the high-energy igniter 7, and closely monitor the changes in the readings of each temperature sensor. If the sensor readings do not respond, check for faults in the cable 71 and the electrical signal lines 24; if the temperature shows an upward trend, it indicates that the circuit connection is normal, and the high-energy igniter 7 can be turned off. After the combustion conditions stabilize, the reading of the fifth high-temperature sensor 21 is used to determine whether the exhaust gas temperature has reached the preset target. If it has not reached the target, the gas mixture ratio or other key process parameters need to be fine-tuned. If the required high-temperature exhaust gas temperature is reached, the current reaction parameters should be kept stable and the generated high-temperature exhaust gas should be directly injected into the reservoir for heating.

[0041] If the gas is exhausted during the test, the test should be suspended. After the gas is replenished, the gas mixture can be directly introduced to resume the test due to the heat storage effect of the porous medium layer 11. If the reading of the first high-temperature sensor 9 does not change significantly at this time, the high-energy igniter 7 needs to be activated for auxiliary ignition. If the test needs to be terminated, simply cut off the supply of the gas mixture and continuously monitor the temperature changes of the first high-temperature sensor 9, the second high-temperature sensor 18, the third high-temperature sensor 19, the fourth high-temperature sensor 20, and the fifth high-temperature sensor 21. If a slow cooling rate is observed, only air can be introduced to accelerate the cooling process. After the temperature at each measuring point drops to a stable state, the heater can be lifted to complete the entire test procedure.

[0042] The working principle of this invention is as follows: After the gas mixture is prepared on the surface, it is pumped into the downhole heater through the well input pipeline at a set flow rate. The gas mixture passes through porous alumina particles 4 with backfire suppression function and the first porous alumina straight-hole mesh gasket 5 before entering the combustion chamber cavity 10. The high-energy igniter 7 is then activated, and feedback data from the detection sensors is monitored. Once the internal temperature of the porous media layer 11 rises to the auto-ignition point or catalytic ignition temperature of the gas mixture, the gas mixture ratio and flow parameters are fine-tuned by the surface control equipment to optimize combustion conditions. Based on the reading of the fifth high-temperature resistant temperature sensor 21, high-temperature exhaust gas that meets the reservoir heating requirements is obtained. Finally, the high-temperature gas in the exhaust gas chamber 13 is used to achieve efficient heating of the reservoir through convective heat transfer.

[0043] In summary, this invention effectively overcomes the problems of low heating efficiency, short service life and high energy consumption of traditional electric heating downhole heaters. At the same time, it solves the technical bottlenecks of difficult control and low recovery rate of conventional combustion heaters. The device uses convective heat transfer to transfer heat to the reservoir, which not only significantly improves the heat transfer rate and energy utilization efficiency, but also has the advantages of convenient process and strong controllability.

[0044] Furthermore, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first," "second," "third," or "fourth" may explicitly or implicitly include at least one of those features.

[0045] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "setting," "connection," "fixing," "screw connection," etc., 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 connection of two components or the interaction between two components. Unless otherwise explicitly limited, those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0046] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A downhole porous medium combustion heater, characterized in that, The system includes an intake chamber shell (15), a combustion chamber shell (16), and an exhaust chamber shell (17). The intake chamber shell (15), the combustion chamber shell (16), and the exhaust chamber shell (17) respectively form an intake chamber cavity (3), a combustion chamber cavity (10), and an exhaust chamber cavity (13). An air inlet (1) is provided at the top of the intake chamber cavity (3), and a stainless steel wire mesh (2) is provided at the top of the inside of the intake chamber cavity (3). A first porous alumina straight hole mesh gasket (5) is installed at the bottom of the inside of the intake chamber cavity (3). The space between the stainless steel wire mesh (2) and the first porous alumina straight hole mesh gasket (5) in the intake chamber cavity (3) is filled with porous alumina granules (4). A high-energy igniter (7) is symmetrically installed at the top of the inner wall of the combustion chamber cavity (10), and a second porous alumina straight hole mesh gasket (8) is installed below the high-energy igniter (7) in the combustion chamber cavity (10), and a third porous alumina straight hole mesh gasket (12) is installed at the bottom of the combustion chamber cavity (10). A porous medium layer (11) is provided between the second porous alumina straight hole mesh gasket (8) and the third porous alumina straight hole mesh gasket (12) in the combustion chamber cavity (10). The combustion chamber cavity (10) is equipped with a first high temperature resistant temperature sensor (9), a second high temperature resistant temperature sensor (18), a third high temperature resistant temperature sensor (19), a fourth high temperature resistant temperature sensor (20), and a fifth high temperature resistant temperature sensor (21) in sequence on the inner wall. The first high temperature resistant temperature sensor (9), the second high temperature resistant temperature sensor (18), the third high temperature resistant temperature sensor (19), the fourth high temperature resistant temperature sensor (20), and the fifth high temperature resistant temperature sensor (21) are arranged alternately. The exhaust gas chamber cavity (13) is provided with an exhaust gas outlet (14) at the bottom.

2. The downhole porous medium combustion heater according to claim 1, characterized in that: The air inlet (1) is constructed as a gas inlet channel, and the exhaust outlet (14) is used to directly discharge the high-temperature exhaust gas generated by combustion in the combustion chamber cavity (10).

3. The downhole porous medium combustion heater according to claim 1, characterized in that: The quality control structure on the first porous alumina straight hole mesh pad (5) is uniformly arranged and distributed, and its mesh diameter is smaller than the particle size of the porous alumina granules (4).

4. A downhole porous medium combustion heater according to claim 1, characterized in that: Flanges (6) are provided on the outer side of the bottom end of the intake chamber housing (15), the outer side of the top and bottom ends of the combustion chamber cavity (10), and the outer side of the top end of the exhaust gas chamber cavity (13). The intake chamber housing (15) and the combustion chamber housing (16), and the combustion chamber housing (16) and the exhaust gas chamber housing (17) are fixedly connected by the flanges (6).

5. A downhole porous medium combustion heater according to claim 1, characterized in that: The high-energy igniter (7) is connected to a cable (71) at one end outside the combustion chamber cavity (10). An ignition rod (73) is provided at one end of the high-energy igniter (7) located in the combustion chamber cavity (10), and the end of the ignition rod (73) extends into the combustion chamber cavity (10). The ignition rod (73) is located above the second porous medium alumina straight hole mesh gasket (8). The outer side of the combustion chamber cavity (10) is symmetrically provided with a first threaded hole (72). The outer side of the ignition rod (73) is provided with an external thread that mates with the first threaded hole (72). The ignition rod (73) is threadedly connected in the first threaded hole (72).

6. A downhole porous medium combustion heater according to claim 1, characterized in that: The stainless steel wire mesh (2) is fixedly connected to the inner wall of the air inlet chamber (3) by welding process, and the corresponding cavity below the air inlet (1) is designed with an expanded capacity.

7. A downhole porous medium combustion heater according to claim 1, characterized in that: The intake chamber shell (15), combustion chamber shell (16) and exhaust chamber shell (17) are all made of stainless steel high temperature resistant material, and the stainless steel high temperature resistant material has a high temperature resistance of not less than 1200℃ and excellent compressive bearing capacity.

8. A downhole porous medium combustion heater according to claim 1, characterized in that: The first high-temperature resistant temperature sensor (9), the second high-temperature resistant temperature sensor (18), the third high-temperature resistant temperature sensor (19), the fourth high-temperature resistant temperature sensor (20), and the fifth high-temperature resistant temperature sensor (21) are connected to an electrical signal line (24) at one end outside the combustion chamber cavity (10), and the first high-temperature resistant temperature sensor (9), the second high-temperature resistant temperature sensor (18), the third high-temperature resistant temperature sensor (19), the fourth high-temperature resistant temperature sensor (20), and the fifth high-temperature resistant temperature sensor (21) are connected to a corundum tube (23) at one end of the combustion chamber cavity (10). The corundum tubes (23) at the ends of the sensor (9), the second high-temperature resistant temperature sensor (18), the third high-temperature resistant temperature sensor (19), and the fourth high-temperature resistant temperature sensor (20) extend into the porous medium layer (11). The corundum tube (23) at the end of the fifth high-temperature resistant temperature sensor (21) is located below the third porous medium alumina straight hole mesh gasket (12). A second threaded hole (22) is provided on the outer side of the combustion chamber cavity (10). An external thread that mates with the second threaded hole (22) is provided on the outer side of the corundum tube (23). The corundum tube (23) and the combustion chamber cavity (10) are connected by threads.

9. A downhole porous medium combustion heater according to claim 8, characterized in that: High-temperature resistant putty and high-temperature resistant tape are used to seal the connections between the intake chamber housing (15) and the combustion chamber housing (16), between the combustion chamber housing (16) and the exhaust chamber housing (17), between the high-energy igniter (7) and the combustion chamber cavity (10), and between the corundum tube (23) and the combustion chamber cavity (10).

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