Device and method for heavy oil viscosity reduction and huff-and-puff production by injecting natural gas into the well for downhole pressurization.

Abstract

This invention relates to the field of heavy oil reservoir development technology, and particularly to a device and method for achieving viscosity reduction and huff-and-puff production of heavy oil through downhole natural gas injection pressurization. The technical solution is as follows: a gas supply pipeline is installed in the annulus between the casing and the pump barrel. The upper end of the gas supply pipeline is connected to a natural gas injection device on the surface, and the lower end is connected to the inlet of a downhole natural gas booster pump. A gas injection packer is installed on the lower side of the pump barrel, and an oil inlet is provided on the pipe wall below the gas injection packer. The lower end of the gas injection packer is connected to the downhole natural gas booster pump via a transition connector. Its advantages are: this invention can simultaneously increase the pressure of natural gas, allowing it to dynamically miscible and dissolve in the heavy oil, significantly reducing its viscosity. The increased pressure due to volume expansion facilitates flow into the wellbore. Furthermore, it can create a foam oil effect, thereby reducing viscosity and increasing production in heavy oil reservoirs. Its overall operating cost is lower than that of steam thermal recovery, and its safety is also significantly improved.

Description

Technical Field

[0001] This invention relates to the field of heavy oil reservoir development technology, and in particular to an apparatus and method for achieving viscosity reduction and huff-and-puff development of heavy oil through natural gas injection downhole pressurization. Background Technology

[0002] Heavy oil, accounting for approximately 70% of the world's remaining petroleum resources, is becoming a crucial energy source for countries to ensure energy security. However, heavy oil has high viscosity and poor fluidity at room temperature, making it impossible to extract like ordinary crude oil. Currently, the mainstream extraction method involves heating to reduce viscosity and improve fluidity. Specifically, this involves injecting high-temperature, high-pressure steam into the well, allowing it to simmer for several days to dissipate heat, and then opening the well to extract oil using steam injection. However, this method is prone to problems such as steam channeling and a decrease in the oil-steam ratio, and it is also costly to develop. Furthermore, subsequent transportation requires heating, leading to high energy consumption and safety hazards. A second development method involves using chemical agents for cold extraction of heavy oil, altering its molecular structure and reducing viscosity. For example, adding oil-soluble surfactants or mixed aromatics can significantly reduce the amount of light oil added and improve fluidity. However, this method requires subsequent treatment of the chemical agents, resulting in high refining costs and affecting product quality. A third development method involves mixing light oil into heavy oil for cold extraction, directly reducing the overall viscosity and improving flow properties. However, this method is also costly and dependent on the external supply of light oil resources. For example, our company applied for Chinese patent number 202110859238X on July 28, 2021, entitled "A Device and Method for Continuously Injecting Light Oil to Achieve Cold Extraction of Heavy Oil." The technical solution is as follows: a double-layer injection isolation pipe is connected to the lower end of the pump barrel; an injection suction distributor is connected to the lower end of the double-layer isolation pipe; a suction floating ball is installed in the inner cavity of the double-layer isolation pipe; an injection diluent is connected to the lower end of the injection suction distributor; a multi-functional constant pressure isolation plate is installed in the lower part of the inner cavity of the injection suction distributor; a packer seat pressure plate is installed in the upper part of the inner cavity of the packer; and a pump plunger is installed inside the pump barrel. The advantages of this invention are that there is no risk of burns during construction; because it uses a cold extraction process for heavy oil, it also avoids the risk of pipeline blockage due to temperature drop during the gathering and transportation of extracted heavy oil; the dilution source uses light oil, which can be continuously injected, and compared with chemical dilution sources, light oil is more abundant and less expensive. However, its shortcomings are: using light oil as the medium for cold extraction of heavy oil is relatively more expensive than natural gas. In particular, the more heavy hydrocarbon components such as propane and butane are in natural gas, the stronger their ability to dissolve in heavy oil. Therefore, if natural gas can be used as the medium to reduce the viscosity of heavy oil, and then natural gas is injected using coiled tubing technology, the production cost will be more advantageous. In addition, natural gas has the advantage of helping to lift the liquid upwards, which can improve the efficiency of oil extraction.For example, our company filed Chinese patent application No. 2026102676257 on March 6, 2026, entitled "A Device and Method for Cold Extraction of Heavy Oil by Injecting Natural Gas into Continuous Tubing." The technical solution is as follows: the upper end of the continuous tubing is connected to a natural gas storage tank via a gas booster pump, and the other end is lowered into the production tubing and connected to a pneumatic production pump. A gas-liquid separator is connected to one side of the wellhead on the surface. The lower side of the gas-liquid separator is connected to the oil pipeline, and the upper part is connected to the upper side of the natural gas storage tank. Natural gas is pressurized and injected downhole along the continuous tubing. The pneumatic production pump then extracts the oil to the gas-liquid separator on the surface. After separation, the natural gas is recycled, and the separated oil enters the oil pipeline. This invention utilizes the property of natural gas to reduce the viscosity of heavy oil to achieve cold extraction. Furthermore, it utilizes the ability of natural gas to lift liquids upwards, thereby improving extraction efficiency and reducing the cost of cold extraction of heavy oil. It should be noted that the main purpose of this invention is to use natural gas to reduce the viscosity of heavy oil entering the casing before extracting it to the surface. The natural gas injected in this invention is not sent into the heavy oil reservoir for huff and puff to reduce the viscosity of the heavy oil in the reservoir. Furthermore, deeper heavy oil reservoirs require greater natural gas injection pressure, which places higher demands on the natural gas injection equipment on the surface and increases costs. Summary of the Invention

[0003] The purpose of this invention is to address the aforementioned deficiencies in existing technologies by providing a device and method for injecting natural gas into the well to achieve viscosity reduction and production of heavy oil. This method involves installing a downhole natural gas booster pump inside the well to increase the pressure of the natural gas, allowing it to enter deeper heavy oil reservoirs through the perforations in the wellbore. The natural gas comes into contact with the heavy oil in the reservoir, dynamically miscible, and dissolves in the oil, significantly reducing its viscosity. The increased pressure due to volume expansion also helps the crude oil flow into the wellbore. Furthermore, it creates a foaming oil effect, thereby reducing viscosity and increasing production in the heavy oil reservoir. The overall operating cost is lower than that of steam thermal recovery, and safety is also significantly improved.

[0004] The device for downhole pressurization via natural gas injection to achieve viscosity reduction and huff-and-puff extraction of heavy oil, mentioned in this invention, comprises a pump barrel and a plunger pump. The pump barrel is installed inside the casing, and the plunger pump is installed inside the pump barrel. The device also includes a downhole natural gas booster pump, a gas supply pipeline, a ball seat, a gas injection packer, and a transition connector. The ball seat is installed on the upper inner side of the pump barrel. The gas supply pipeline is installed in the annulus between the casing and the pump barrel. The upper end of the gas supply pipeline is connected to the surface natural gas injection device, and the lower end is connected to the downhole... The inlet of the natural gas booster pump is connected; a gas injection packer is installed on the lower middle side of the pump barrel, and an oil inlet is provided on the pipe wall below the gas injection packer. The lower end of the gas injection packer is connected to the downhole natural gas booster pump through a transition conversion joint; natural gas is injected into the downhole natural gas booster pump through the gas supply pipeline and the gas injection packer. After being pressurized by the downhole natural gas booster pump, it is sent into the heavy oil reservoir along the perforation area on the lower side of the casing. Through continuous contact with the heavy oil in the heavy oil reservoir, the viscosity of the heavy oil is reduced.

[0005] Preferably, the downhole natural gas booster pump includes a booster piston, a low-pressure sealing cylinder liner, a high-pressure sealing cylinder liner, an anti-jamming check valve, a large-displacement gas injection check valve, a plug, a main natural gas inlet, a low-pressure cylinder liner inlet, a booster gas exchange main channel, a booster gas inlet channel, and an auxiliary spring. The lower part of the low-pressure sealing cylinder liner is connected to the high-pressure sealing cylinder liner, and a plug is installed on the top of the low-pressure sealing cylinder liner. The booster piston is installed inside the low-pressure sealing cylinder liner and the high-pressure sealing cylinder liner, with the upper part of the booster piston located within the low-pressure sealing cylinder liner. Inside the sleeve, the lower part is located inside the high-pressure sealing cylinder sleeve, and an auxiliary spring is installed between the upper part of the booster piston and the bottom of the low-pressure sealing cylinder sleeve. A large-displacement gas injection check valve is installed inside the booster piston. The upper end of the side wall of the low-pressure sealing cylinder sleeve is provided with a natural gas main inlet. The upper side of the low-pressure sealing cylinder sleeve is provided with a low-pressure cylinder sleeve air inlet, and the lower side is provided with a gas exchange channel. The side wall of the high-pressure sealing cylinder sleeve is provided with a booster gas exchange main channel, and the lower side is provided with a booster air inlet channel. An anti-jamming check valve is provided at the lower end of the high-pressure sealing cylinder sleeve.

[0006] Preferably, the lower part of the aforementioned natural gas main inlet is connected to a natural gas exchange channel, and the bottom of the natural gas exchange channel is connected to the exchange channel via a second differential pressure check valve; the lower part of the booster gas exchange main channel is connected to a booster air intake channel via a first differential pressure check valve, and the upper end of the booster gas exchange main channel is connected to a low-pressure sealing cylinder liner.

[0007] Preferably, the above-mentioned large-displacement gas injection one-way valve includes a first ball seat, a first ball, a first compression spring, and a first support body. The first ball seat is located at the top of the central cavity of the booster piston, and the first ball is installed at the lower part of the first ball seat. The lower end of the first ball is connected to the first support body through the first compression spring, and the first support body is threadedly connected to the lower end of the central cavity of the booster piston.

[0008] Preferably, the first differential pressure check valve includes a second ball seat, a second ball, a second compression spring, and a second support. The second ball seat is located at the lower end of the main pressure-boosting ventilation channel and above the main pressure-boosting intake channel. The second ball and the second ball seat contact and cooperate to close the main pressure-boosting ventilation channel and the main pressure-boosting intake channel. The lower end of the second ball is connected to the second support through the second compression spring, and the second support is threaded to the lower end of the high-pressure sealing cylinder liner.

[0009] Preferably, the aforementioned gas-injection packer includes a central tube, a cylinder liner, a piston, a seated shear pin, a sealing rubber sleeve, a release pressure transmission sleeve, a pressure transmission control piston, an oil inlet / outlet control valve, a return spring, and a packer gas injection channel. The outer wall of the central tube has an axial packer gas injection channel. A cylinder liner is installed outside the central tube. The annular space formed between the cylinder liner and the outer surface of the central tube is used to install the piston via the seated shear pin. A sealing rubber sleeve is installed at the lower end of the piston. A release pressure transmission sleeve is installed at the lower part of the sealing rubber sleeve. The lower end of the release pressure transmission sleeve has a gas injection channel outlet. The lower inner wall of the sleeve is located on the outer wall of the oil inlet / outlet control valve. The oil inlet / outlet control valve is sleeved on the outer wall of the central tube and is used to open and close the oil inlet. A return spring is installed below the oil inlet / outlet control valve. A pressure transmission control piston is installed on the upper part of the oil inlet / outlet control valve. When natural gas is injected into the gas injection channel of the packer, the pressure transmission control piston moves down, causing the oil inlet / outlet control valve to move down to the oil inlet to form a closed state. Natural gas enters the gas supply pipeline below through the annulus formed between the unsealing pressure transmission sleeve and the central tube and the gas injection channel outlet.

[0010] Preferably, the lower end of the return spring is connected to the spring seat, and the upper end of the unsealing pressure transmission sleeve is connected to the outer wall of the central tube through an unsealing shear pin.

[0011] Preferably, the upper part of the central tube is provided with a sealing hole, and the outer end of the sealing hole is located above the piston; a constant pressure ball seat is installed in the inner cavity of the central tube, and the constant pressure ball seat is located below the inner end of the sealing hole to control the expansion of the sealing rubber sleeve and realize the setting of the gas-injected packer.

[0012] The method of using the device for natural gas injection downhole pressurization to achieve viscosity reduction and huff-and-puff production of heavy oil mentioned in this invention includes the following process:

[0013] 1. Lower the downhole natural gas booster pump, transition adapter, gas supply pipeline, pressure-regulating ball seat carrying the gas, gas injection packer, and pump barrel to the designated position downhole; pressurize the pump barrel at the wellhead on the surface to allow liquid to enter the downhole along the pump barrel and push the piston along the sealing hole to shear the sealing shear pin, and continue to push the sealing rubber sleeve downward to expand, thus achieving the setting of the gas injection packer; then, continue pressurizing to knock off the pressure-regulating ball seat and let it fall into the inner cavity of the transition adapter, and the lower end of the transition adapter is a closed plug head structure; then, lower the plunger pump into the pump barrel to complete the installation;

[0014] Second, natural gas is injected into the gas supply pipeline through the surface natural gas pressurization injection device. The natural gas enters the heavy oil reservoir along the gas injection packer and the downhole natural gas booster pump. The pressurized natural gas is in continuous contact with the heavy oil, which reduces the viscosity of the heavy oil and increases its fluidity. Then, it is extracted to the surface by the plunger pump.

[0015] When natural gas passes through the gas injection channel of the gas injection packer, the natural gas pushes the pressure transmission control piston to move down, which in turn moves the oil inlet / outlet control valve down to the oil inlet to form a closed state. At the same time, the return spring stores elastic potential energy. As the pressure transmission control piston moves down, the natural gas enters the gas supply pipeline below through the annulus formed between the unsealed pressure transmission sleeve and the central tube and the gas injection channel outlet, and then enters the downhole natural gas booster pump.

[0016] In addition, after natural gas enters the main inlet of the downhole natural gas booster pump, the natural gas pushes the large-volume gas injection check valve to open, and at the same time drives the booster piston to move down to the lower dead point. Then, the natural gas pushes open the anti-sticking check valve, allowing the natural gas to enter the cavity formed between the artificial well bottom, casing and gas injection packer, and then enter the heavy oil reservoir along the perforation area distributed on the casing.

[0017] Once the pressure of the natural gas from the surface reaches equilibrium with the pressure of the natural gas injected into the heavy oil reservoir, the booster injection mode is activated. The large-volume injection check valve returns to its closed position under the action of the first compression spring. The booster piston moves upward to its initial position under the action of the auxiliary spring. At the same time, natural gas flows downward along the natural gas exchange channel, opening the second differential pressure check valve, and then enters the low-pressure sealing cylinder liner along the exchange channel. Then, due to the area difference, the booster piston continues to move downward to the lower dead center, boosting the natural gas in the high-pressure sealing cylinder liner. Simultaneously, the natural gas between the low-pressure sealing cylinder liner and the booster piston flows downward along the booster exchange main channel, opening the first differential pressure check valve, and then enters the high-pressure sealing cylinder liner along the booster intake channel. The boosted natural gas is then sent into the heavy oil reservoir. The booster piston then cycles back and forth until equilibrium is finally reached, completing the booster injection of natural gas and increasing the viscosity reduction range of the heavy oil reservoir.

[0018] 3. After the natural gas pressurization injection is completed, the injection is stopped. At this time, the gas supply pressure in the gas supply pipeline is released. Due to the high formation pressure in the heavy oil reservoir, backflow will occur. At this time, the anti-sticking check valve is closed to prevent oil from entering the downhole natural gas booster pump. At the same time, due to the disappearance of the pressure in the gas supply pipeline, the return spring pushes the oil inlet / outlet control valve upward, causing it to leave the oil inlet and become open. The viscosity-reduced oil in the heavy oil reservoir enters the pump barrel cavity through the oil inlet, and then the plunger pump extracts the viscosity-reduced oil to the surface. As the viscosity-reduced oil is continuously extracted, the viscosity of the remaining heavy oil continuously increases until it is no longer suitable for extraction. At this time, the plunger pump stops working, and natural gas is injected again to continue reducing the viscosity of the heavy oil in the heavy oil reservoir. This cycle is repeated to achieve the extraction of heavy oil.

[0019] Preferably, when well workover operations are required, the tubing string is lifted to cut the unsealing shear pins, disconnecting the unsealing pressure transmission sleeve from the central tube, causing the unsealing pressure transmission sleeve to shift, thereby separating the expanded sealing rubber sleeve from the inner wall of the casing. Then, the entire tubing string, downhole natural gas booster pump, transition conversion joint, gas supply line, gas injection packer, and pump barrel are lifted to the surface as a whole.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] I. This invention employs a dedicated gas-injection packer. While achieving packing and setting, it also incorporates an axial gas injection channel designed on the side wall of the central tube, along with a release pressure transmission sleeve, a pressure control piston, and an oil inlet / outlet control valve. This allows for the closing of the oil inlet during natural gas injection, with the gas being fed downhole into a natural gas booster pump via the gas supply pipeline, achieving downhole boosting of natural gas before injection into the heavy oil reservoir. When it is necessary to extract the oil after its viscosity has been reduced by natural gas, the natural gas injection is stopped, and the oil inlet is opened simultaneously. The reduced-viscosity oil enters the pump barrel and is then extracted to the surface via a plunger pump. This ingeniously designed gas-injection packer simultaneously achieves the functions of packing and setting, injecting natural gas, and allowing the reduced-viscosity oil to enter the pump barrel.

[0022] Second, this invention reduces the requirements for surface natural gas injection equipment by installing a downhole natural gas booster pump inside the well, eliminating the need for higher surface natural gas injection pressure, effectively reducing costs and the risk index of the surface well site. The booster pump can further increase the pressure of natural gas, allowing it to enter deeper heavy oil reservoirs and better contact with the heavy oil within the reservoir. This enables the natural gas to dynamically miscible and dissolve in the heavy oil, significantly reducing the viscosity of the heavy oil. The increased pressure due to volume expansion helps the viscosity-reduced oil flow into the wellbore. In addition, it can also create a foaming oil effect, thereby playing a role in reducing viscosity and increasing production in heavy oil reservoirs.

[0023] Third, this invention achieves viscosity reduction and cold production of heavy oil by injecting natural gas. Its total operating cost is lower than that of steam thermal production, and its safety is greatly improved. It also reduces the cost of transporting the viscosity-reduced oil. In addition, the integrated design of the oil extraction and natural gas injection structure facilitates the one-time lifting and retrieval of tools during well workover, avoiding repeated operations, reducing labor intensity, and increasing the efficiency of the process. Attached Figure Description

[0024] Figure 1 This is a structural diagram of the entire construction process of the present invention;

[0025] Figure 2 This is a schematic diagram of the initial state of the downhole natural gas booster pump;

[0026] Figure 3 This is a schematic diagram of a downhole natural gas booster pump injecting natural gas at a large displacement.

[0027] Figure 4 This is a schematic diagram of the process of the booster piston of the downhole natural gas booster pump resuming its upward movement;

[0028] Figure 5 This is a schematic diagram of the pressurization process of the downhole natural gas booster pump's piston moving downwards;

[0029] Figure 6 This is a schematic diagram of the gas-filled packer;

[0030] Figure 7 This is a schematic diagram showing the state of the gas-filled packer after it has been set.

[0031] Figure 8 This is a schematic diagram showing the state of the oil inlet / outlet control valve after natural gas has been injected into the gas-injected packer and the packer has moved down.

[0032] Figure 9 This is a schematic diagram showing the state of the gas-injected packer when extracting oil.

[0033] Figure 10 yes Figure 8 Schematic diagram of section AA in the diagram;

[0034] Figure 11 This is a schematic diagram of the transition adapter;

[0035] In the diagram: 1. Heavy oil reservoir; 2. Artificial well bottom; 3. Casing; 4. Downhole natural gas booster pump; 5. Gas supply pipeline; 6. Ball seat; 7. Gas injection packer; 8. Pump barrel; 9. Plunger pump; 10. Transition joint.

[0036] 3.1 Perforation area; 4.1 Booster piston; 4.2 Low-pressure sealing cylinder liner; 4.3 High-pressure sealing cylinder liner; 4.4 First differential pressure check valve; 4.5 Anti-jamming check valve; 4.6 Large-displacement gas injection check valve; 4.7 Second differential pressure check valve; 4.8 Plug head; 4.9 Main natural gas inlet; 4.10 Low-pressure cylinder liner inlet; 4.11 Natural gas gas exchange channel; 4.12 Booster gas exchange main channel; 4.13 Booster gas inlet channel; 4.14 Auxiliary spring; 4.15 Gas exchange channel.

[0037] First ball seat 4.6.1, first ball 4.6.2, first compression spring 4.6.3, first support body 4.6.4;

[0038] Second ball seat 4.4.1, second ball 4.4.2, second compression spring 4.4.3, second support body 4.4.4;

[0039] 7.1 Central tube, 7.2 Cylinder liner, 7.3 Piston, 7.4 Sealing shear pin, 7.5 Sealing sleeve, 7.6 Unsealing shear pin, 7.7 Unsealing pressure transmission sleeve, 7.8 Pressure transmission control piston, 7.9 Oil inlet / outlet control valve, 7.10 Return spring, 7.11 Spring seat, 7.12 Packer air injection channel, 7.13 Oil inlet, 7.14 Sealing hole, 7.15 Constant pressure ball seat, 7.7.1 Air injection channel outlet. Detailed Implementation

[0040] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0041] Example 1, referring to Figures 1-11 The device for downhole pressurization via natural gas injection to achieve viscosity reduction and huff-and-puff extraction of heavy oil, mentioned in this invention, includes a pump barrel 8 and a plunger pump 9. The pump barrel 8 is lowered into the casing 3, and the plunger pump 9 is lowered into the pump barrel 8. The device also includes a downhole natural gas booster pump 4, a gas supply line 5, a ball seat 6, a gas injection packer 7, and a transition connector 10. The ball seat 6 is installed on the upper inner side of the pump barrel 8. The gas supply line 5 is lowered into the annulus between the casing 3 and the pump barrel 8. The upper end of the gas supply line 5 is connected to the natural gas injection device on the surface, and the lower end is connected to the downhole natural gas booster pump. The air inlet of pump 4 is connected; a gas injection packer 7 is installed on the lower middle side of pump barrel 8, and an oil inlet hole 7.13 is provided on the pipe wall on the lower side of the gas injection packer 7. The lower end of the gas injection packer 7 is connected to the downhole natural gas booster pump 4 through the transition conversion joint 10; natural gas is injected into the downhole natural gas booster pump 4 through the gas supply line 5 and the gas injection packer 7. After being pressurized by the downhole natural gas booster pump 4, it is sent into the heavy oil reservoir 1 along the perforation area 3.1 on the lower side of the casing 3. Through continuous contact with the heavy oil in the heavy oil reservoir 1, the viscosity of the heavy oil is reduced.

[0042] Reference Figures 2-5The downhole natural gas booster pump 4 mentioned in this invention includes a booster piston 4.1, a low-pressure sealing cylinder liner 4.2, a high-pressure sealing cylinder liner 4.3, an anti-jamming check valve 4.5, a large-displacement gas injection check valve 4.6, a plugging head 4.8, a main natural gas inlet 4.9, a low-pressure cylinder liner inlet 4.10, a booster gas exchange main channel 4.12, a booster gas inlet channel 4.13, and an auxiliary spring 4.14. The lower part of the low-pressure sealing cylinder liner 4.2 is connected to the high-pressure sealing cylinder liner 4.3, and the plugging head 4.8 is installed on the top of the low-pressure sealing cylinder liner 4.2. The booster piston 4.1 is installed inside the low-pressure sealing cylinder liner 4.2 and the high-pressure sealing cylinder liner 4.3, with the upper part of the booster piston 4.1 located at the low pressure. Inside the sealing cylinder liner 4.2, the lower part is located inside the high-pressure sealing cylinder liner 4.3, and an auxiliary spring 4.14 is installed between the upper part of the booster piston 4.1 and the bottom of the low-pressure sealing cylinder liner 4.2. A large-displacement gas injection check valve 4.6 is installed inside the booster piston 4.1. The upper end of the side wall of the low-pressure sealing cylinder liner 4.2 is provided with a natural gas main inlet 4.9. The upper side of the low-pressure sealing cylinder liner 4.2 is provided with a low-pressure cylinder liner air inlet 4.10, and the lower side is provided with a gas exchange channel 4.15. The side wall of the high-pressure sealing cylinder liner 4.3 is provided with a booster gas exchange main channel 4.12, and the lower side is provided with a booster air inlet channel 4.13. An anti-jamming check valve 4.5 is provided at the lower end of the high-pressure sealing cylinder liner 4.3.

[0043] The lower part of the aforementioned natural gas main inlet 4.9 is connected to the natural gas exchange channel 4.11, and the bottom of the natural gas exchange channel 4.11 is connected to the exchange channel 4.15 through the second differential pressure check valve 4.7; the lower part of the booster gas exchange main channel 4.12 is connected to the booster air intake channel 4.13 through the first differential pressure check valve 4.4, and the upper end of the booster gas exchange main channel 4.12 is connected to the low-pressure sealing cylinder liner 4.2.

[0044] The aforementioned large-displacement air injection check valve 4.6 includes a first ball seat 4.6.1, a first ball 4.6.2, a first compression spring 4.6.3, and a first support body 4.6.4. The first ball seat 4.6.1 is located at the top of the central cavity of the booster piston 4.1. The first ball 4.6.2 is installed at the lower part of the first ball seat 4.6.1. The lower end of the first ball 4.6.2 is connected to the first support body 4.6.4 through the first compression spring 4.6.3. The first support body 4.6.4 is threadedly connected to the lower end of the central cavity of the booster piston 4.1.

[0045] Furthermore, the aforementioned first differential pressure check valve 4.4 includes a second ball seat 4.4.1, a second ball 4.4.2, a second compression spring 4.4.3, and a second support body 4.4.4. The second ball seat 4.4.1 is located at the lower end of the booster ventilation main channel 4.12 and above the booster intake channel 4.13. The second ball 4.4.2 contacts and cooperates with the second ball seat 4.4.1 to close the booster ventilation main channel 4.12 and the booster intake channel 4.13. The lower end of the second ball 4.4.2 is connected to the second support body 4.4.4 through the second compression spring 4.4.3, and the second support body 4.4.4 is threadedly connected to the lower end of the high-pressure sealing cylinder liner 4.3.

[0046] Reference Figures 6-8 The gas-injection packer 7 mentioned in this invention includes a central tube 7.1, a cylinder liner 7.2, a piston 7.3, a seat seal shear pin 7.4, a sealing rubber sleeve 7.5, a release pressure transmission sleeve 7.7, a pressure transmission control piston 7.8, an oil inlet / outlet control valve 7.9, a return spring 7.10, and a packer gas injection channel 7.12. The outer wall of the central tube 7.1 is provided with an axial packer gas injection channel 7.12. The cylinder liner 7.2 is installed outside the central tube 7.1. The annular space formed between the cylinder liner 7.2 and the outer side of the central tube 7.1 is used to install the piston 7.3 through the seat seal shear pin 7.4. The sealing rubber sleeve 7.5 is installed at the lower end of the piston 7.3. The release pressure transmission sleeve 7.7 is installed at the lower part of the sealing rubber sleeve 7.5. The lower end of the release pressure transmission sleeve 7.7 is provided with a gas injection channel outlet. 7.7.1 The lower inner wall of the unsealing pressure transmission sleeve 7.7 is located on the outer wall of the oil inlet / outlet control valve 7.9. The oil inlet / outlet control valve 7.9 is sleeved on the outer wall of the central tube 7.1 and is used to open and close the oil inlet port 7.13. A return spring 7.10 is installed below the oil inlet / outlet control valve 7.9. A pressure transmission control piston 7.8 is installed on the upper part of the oil inlet / outlet control valve 7.9. When natural gas is injected into the packer injection channel 7.12, the pressure transmission control piston 7.8 moves down, causing the oil inlet / outlet control valve 7.9 to move down to the oil inlet port 7.13 to form a closed state. Natural gas enters the lower gas supply pipeline 5 through the annulus formed between the unsealing pressure transmission sleeve 7.7 and the central tube 7.1 and the injection channel outlet 7.7.1.

[0047] The lower end of the return spring 7.10 is connected to the spring seat 7.11, and the upper end of the release pressure transmission sleeve 7.7 is connected to the outer wall of the central tube 7.1 through the release shear pin 7.6.

[0048] In addition, a sealing hole 7.14 is provided in the upper middle part of the central tube 7.1, and the outer end of the sealing hole 7.14 is located above the piston 7.3; a constant pressure ball seat 7.15 is installed in the inner cavity of the central tube 7.1, and the constant pressure ball seat 7.15 is located below the inner end of the sealing hole 7.14, controlling the expansion of the sealing rubber sleeve 7.5 to realize the setting of the gas injection packer 7.

[0049] The method of using the device for natural gas injection downhole pressurization to achieve viscosity reduction and huff-and-puff production of heavy oil mentioned in this invention includes the following process:

[0050] 1. Lower the downhole natural gas booster pump 4, transition adapter 10, gas supply pipeline 5, pressure-regulating ball seat 7.15, gas injection packer 7, and pump barrel 8 to the designated positions in the well. At the surface wellhead, pressurize the pump barrel 8 to allow liquid to enter the well along the pump barrel 8, and push the piston 7.3 along the sealing hole 7.14 to cut the sealing shear pin 7.4. Continue pushing downwards to expand the sealing rubber sleeve 7.5, thus achieving the setting of the gas injection packer 7. (Refer to...) Figure 7 Then, continue pressurizing to knock off the constant pressure ball seat 7.15 and let it fall into the inner cavity of the transition adapter 10. The lower end of the transition adapter 10 is a closed plug structure, as shown in the reference. Figure 11 The upper part is used to receive the detached pressure ball seat 7.15, and the lower end is used to connect to the upper end of the downhole natural gas booster pump 4; then, the plunger pump 9 is lowered into the pump barrel 8 to complete the installation.

[0051] Second, natural gas is injected into the gas supply pipeline 5 through the surface natural gas pressurization injection device. The natural gas enters the heavy oil reservoir 1 through the gas injection packer 7 and the downhole natural gas booster pump 4. The pressurized natural gas is in continuous contact with the heavy oil to reduce the viscosity of the heavy oil and increase its fluidity. Then, the viscosity-reduced oil is extracted to the surface through the plunger pump 9.

[0052] When natural gas passes through the gas injection channel 7.12 of the gas injection packer 7, the natural gas pushes the pressure transmission control piston 7.8 to move downwards, causing the oil inlet / outlet control valve 7.9 to move downwards to the oil inlet port 7.13, forming a closed state. (Refer to...) Figure 8 Meanwhile, the return spring 7.10 stores elastic potential energy, and as the pressure transmission control piston 7.8 moves down, natural gas enters the gas supply pipeline 5 below through the annulus formed between the unsealed pressure transmission sleeve 7.7 and the central pipe 7.1 and the gas injection channel outlet 7.7.1, and then enters the downhole natural gas booster pump 4.

[0053] Additionally, refer to Figure 2 After natural gas enters the main natural gas inlet 4.9 of the downhole natural gas booster pump 4, the natural gas pushes the large-volume gas injection check valve 4.6 to open, and at the same time drives the booster piston 4.1 to move downward to the lower dead point. Then, the natural gas pushes open the anti-sticking check valve 4.5, so that the natural gas enters the cavity formed between the artificial well bottom 2, the casing 3 and the gas injection packer 7, and then enters the heavy oil reservoir 1 along the perforation area 3.1 distributed on the casing 3.

[0054] Once the pressure of the natural gas from the surface reaches equilibrium with the pressure of the natural gas injected into heavy oil reservoir 1, the pressurized injection mode is activated. The large-volume injection check valve 4.6, under the action of the first compression spring 4.6.3, returns to its closed position. (Refer to...) Figure 3 The booster piston 4.1, under the action of the auxiliary spring 4.14, moves upward to its initial upper position, as shown in the reference. Figure 4 Simultaneously, natural gas flows downwards along the natural gas exchange passage 4.11, opening the second differential pressure check valve 4.7, and then enters the low-pressure sealing cylinder liner 4.2 along the exchange passage 4.15. Then, due to the area difference, the booster piston 4.1 continues to move downwards to the bottom dead center, pressurizing the natural gas in the high-pressure sealing cylinder liner 4.3. (Refer to...) Figure 5 Meanwhile, the natural gas between the low-pressure sealing cylinder liner 4.2 and the booster piston 4.1 flows downward along the booster gas exchange main channel 4.12. After opening the first differential pressure check valve 4.4, it enters the high-pressure sealing cylinder liner 4.3 along the booster air intake channel 4.13. The boosted natural gas is then sent into the heavy oil reservoir 1. The booster piston 4.1 then cycles back and forth until it finally reaches equilibrium, completing the booster injection of natural gas and increasing the viscosity reduction range of the heavy oil reservoir 1.

[0055] 3. After the natural gas pressurization injection is completed, the injection is stopped. At this time, the gas supply pressure of the gas supply pipeline 5 is released. Due to the high formation pressure in the heavy oil reservoir 1, backflow will occur. At this time, the anti-sticking check valve 4.5 is closed to prevent oil from entering the downhole natural gas booster pump 4. Simultaneously, due to the disappearance of pressure in the gas supply pipeline 5, the return spring 7.10 pushes the oil inlet / outlet control valve 7.9 upward, causing it to move away from the oil inlet port 7.13 and become open. Refer to... Figure 9 The viscosity-reduced oil in heavy oil reservoir 1 enters the inner cavity of pump barrel 8 through oil inlet 7.13, and then the viscosity-reduced oil is extracted to the surface by the operation of plunger pump 9. As the viscosity-reduced oil is continuously extracted, the viscosity of the remaining heavy oil increases until it is no longer suitable for extraction. At this point, the operation of plunger pump 9 is stopped, and natural gas is injected again to continue reducing the viscosity of the heavy oil in heavy oil reservoir 1. This cycle is repeated to achieve the extraction of heavy oil.

[0056] The principle of this invention, which uses natural gas injection into heavy oil reservoir 1 to reduce the viscosity of heavy oil, is as follows:

[0057] First, dissolution and viscosity reduction: Under high pressure, natural gas continuously contacts heavy oil, allowing for dynamic miscibility and significant dissolution in the heavy oil, resulting in a substantial reduction in viscosity by 1 to 2 orders of magnitude. Second, volume expansion and pressurization: After dissolving natural gas, the heavy oil expands in volume, increasing formation pressure and enhancing displacement, which helps the viscosity-reduced oil flow into the wellbore. Third, the foaming oil effect: When the pressure decreases from high to low, the non-equilibrium bubble point pressure is lower, and gas remains in the oil, forming "foaming oil," which improves the fluidity of the viscosity-reduced oil and expands its reach.

[0058] Example 2, the method of using the device for natural gas injection downhole pressurization to achieve viscosity reduction and huff-and-puff production of heavy oil mentioned in this invention, further includes the following well workover operation process:

[0059] When well workover is required, the tubing string is lifted to shear the release shear pin 7.6, disconnecting the release pressure transmission sleeve 7.7 from the central tube 7.1, causing the release pressure transmission sleeve 7.7 to shift, thereby separating the expanded sealing sleeve 7.5 from the inner wall of the casing 3. Then, the entire tubing string, downhole natural gas booster pump 4, transition adapter 10, gas supply line 5, gas injection packer 7, and pump barrel 8 are lifted to the surface as a whole.

[0060] The above description is merely a partial preferred embodiment of the present invention. Any person skilled in the art can modify the above-described technical solutions or modify them into equivalent technical solutions. Therefore, any simple modifications or equivalent transformations made based on the technical solutions of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A device for injecting natural gas into a well to increase pressure and achieve viscosity reduction and huff-and-puff production of heavy oil, comprising a pump barrel (8) and a plunger pump (9), wherein the pump barrel (8) is lowered into the casing (3), and the plunger pump (9) is lowered into the pump barrel (8), characterized in that: It also includes a downhole natural gas booster pump (4), a gas supply line (5), a ball seat (6), a gas injection packer (7), and a transition connector (10). The ball seat (6) is installed on the upper inner side of the pump barrel (8). The gas supply line (5) is lowered into the annulus between the casing (3) and the pump barrel (8). The upper end of the gas supply line (5) is connected to the natural gas injection device on the surface, and the lower end is connected to the air inlet of the downhole natural gas booster pump (4). The gas injection packer (7) is installed on the lower middle side of the pump barrel (8). (7) An oil inlet hole (7.13) is provided on the lower side of the pipe wall. The lower end of the gas injection packer (7) is connected to the downhole natural gas booster pump (4) through the transition conversion joint (10). Natural gas is injected into the downhole natural gas booster pump (4) through the gas supply line (5) and the gas injection packer (7). After being pressurized by the downhole natural gas booster pump (4), it is sent into the heavy oil reservoir (1) along the perforation area (3.1) on the lower side of the casing (3). Through continuous contact with the heavy oil in the heavy oil reservoir (1), the viscosity of the heavy oil is reduced. The downhole natural gas booster pump (4) includes a booster piston (4.1), a low-pressure sealing cylinder liner (4.2), a high-pressure sealing cylinder liner (4.3), an anti-jamming check valve (4.5), a large-displacement gas injection check valve (4.6), a plug (4.8), a main natural gas inlet (4.9), a low-pressure cylinder liner inlet (4.10), a booster gas exchange main channel (4.12), a booster gas inlet channel (4.13), and an auxiliary spring (4.14). The lower part of the low-pressure sealing cylinder liner (4.2) is connected to the high-pressure sealing cylinder liner (4.3), and the plug (4.8) is installed on the top of the low-pressure sealing cylinder liner (4.2). The booster piston (4.1) is installed inside the low-pressure sealing cylinder liner (4.2) and the high-pressure sealing cylinder liner (4.3). The upper part of the booster piston (4.1) is located in the low-pressure sealing cylinder liner. Inside the pressure-sealed cylinder liner (4.2), the lower part is located inside the high-pressure sealed cylinder liner (4.3), and an auxiliary spring (4.14) is installed between the upper part of the booster piston (4.1) and the bottom of the low-pressure sealed cylinder liner (4.2). A large-displacement gas injection check valve (4.6) is installed inside the booster piston (4.1). The upper end of the side wall of the low-pressure sealed cylinder liner (4.2) is provided with a natural gas main inlet (4.9). The upper side of the low-pressure sealed cylinder liner (4.2) is provided with a low-pressure cylinder liner air inlet (4.10), and the lower side is provided with a gas exchange channel (4.15). The side wall of the high-pressure sealed cylinder liner (4.3) is provided with a booster gas exchange main channel (4.12), and the lower side is provided with a booster air inlet channel (4.13). An anti-jamming check valve (4.5) is provided at the lower end of the high-pressure sealed cylinder liner (4.3).

2. The apparatus for injecting natural gas into the well to increase pressure and achieve viscosity reduction and huff-and-puff production of heavy oil according to claim 1, characterized in that: The lower part of the natural gas main inlet (4.9) is connected to the natural gas exchange channel (4.11), and the bottom of the natural gas exchange channel (4.11) is connected to the exchange channel (4.15) through the second differential pressure check valve (4.7); the lower part of the booster exchange main channel (4.12) is connected to the booster intake channel (4.13) through the first differential pressure check valve (4.4), and the upper end of the booster exchange main channel (4.12) is connected to the low-pressure sealing cylinder liner (4.2).

3. The apparatus for injecting natural gas into the well to increase pressure and achieve viscosity reduction and huff-and-puff production of heavy oil according to claim 2, characterized in that: The large-displacement air injection check valve (4.6) includes a first ball seat (4.6.1), a first ball (4.6.2), a first compression spring (4.6.3), and a first support body (4.6.4). The first ball seat (4.6.1) is located at the top of the central cavity of the booster piston (4.1). The first ball (4.6.2) is installed at the lower part of the first ball seat (4.6.1). The lower end of the first ball (4.6.2) is connected to the first support body (4.6.4) through the first compression spring (4.6.3). The first support body (4.6.4) is threadedly connected to the lower end of the central cavity of the booster piston (4.1).

4. The apparatus for injecting natural gas into the well to increase pressure and achieve viscosity reduction and huff-and-puff production of heavy oil according to claim 3, characterized in that: The first differential pressure check valve (4.4) includes a second ball seat (4.4.1), a second ball (4.4.2), a second compression spring (4.4.3), and a second support (4.4.4). The second ball seat (4.4.1) is located at the lower end of the main pressure-boosting ventilation channel (4.12) and above the boosting intake channel (4.13). The second ball (4.4.2) contacts and cooperates with the second ball seat (4.4.1) to close the main pressure-boosting ventilation channel (4.12) and the boosting intake channel (4.13). The lower end of the second ball (4.4.2) is connected to the second support (4.4.4) through the second compression spring (4.4.3), and the second support (4.4.4) is threadedly connected to the lower end of the high-pressure sealing cylinder liner (4.3).

5. The apparatus for injecting natural gas into the well to increase pressure and achieve viscosity reduction and huff-and-puff production of heavy oil according to claim 4, characterized in that: The gas-injecting packer (7) includes a central tube (7.1), a cylinder liner (7.2), a piston (7.3), a seated shear pin (7.4), a sealing sleeve (7.5), a release pressure transmission sleeve (7.7), a pressure transmission control piston (7.8), an oil inlet / outlet control valve (7.9), a return spring (7.10), and a packer gas injection channel (7.12). The outer wall of the central tube (7.1) is provided with an axial packer gas injection channel (7.12). The cylinder liner (7.2) is installed outside the central tube (7.1). The annular space formed between the cylinder liner (7.2) and the outer side of the central tube (7.1) is used to install the piston (7.3) through the seated shear pin (7.4). The sealing sleeve (7.5) is installed at the lower end of the piston (7.3). The release pressure transmission sleeve (7.7) is installed at the lower part of the sealing sleeve (7.5). The lower end of the release pressure transmission sleeve (7.7) is provided with a gas injection port. The lower inner wall of the unsealing pressure transmission sleeve (7.7) is located on the outer wall of the oil inlet / outlet control valve (7.9). The oil inlet / outlet control valve (7.9) is sleeved on the outer wall of the central tube (7.1) and is used to open and close the oil inlet (7.13). A return spring (7.10) is installed below the oil inlet / outlet control valve (7.9). A pressure transmission control piston (7.8) is installed on the upper part of the oil inlet / outlet control valve (7.9). When natural gas is injected into the packer gas injection channel (7.12), the pressure transmission control piston (7.8) moves down, causing the oil inlet / outlet control valve (7.9) to move down to the oil inlet (7.13) to form a closed state. Natural gas enters the gas supply line (5) below through the annulus formed between the unsealing pressure transmission sleeve (7.7) and the central tube (7.1) and the gas injection channel outlet (7.7.1).

6. The apparatus for injecting natural gas into the well to increase pressure and achieve viscosity reduction and huff-and-puff production of heavy oil according to claim 5, characterized in that: The lower end of the return spring (7.10) is connected to the spring seat (7.11), and the upper end of the release pressure transmission sleeve (7.7) is connected to the outer wall of the central tube (7.1) through the release shear pin (7.6).

7. The apparatus for injecting natural gas into the well to increase pressure and achieve viscosity reduction and huff-and-puff production of heavy oil according to claim 6, characterized in that: The upper middle part of the central tube (7.1) is provided with a sealing hole (7.14), and the outer end of the sealing hole (7.14) is located above the piston (7.3); a constant pressure ball seat (7.15) is installed in the inner cavity of the central tube (7.1), and the constant pressure ball seat (7.15) is located below the inner end of the sealing hole (7.14), controlling the expansion of the sealing rubber sleeve (7.5) to realize the setting of the gas-injected packer (7).

8. A method of using the apparatus for injecting natural gas into the well to increase pressure and achieve viscosity reduction and huff-and-puff production of heavy oil as described in claim 7, characterized in that: Includes the following processes:

1. Lower the downhole natural gas booster pump (4), transition adapter (10), gas supply pipeline (5), pressure-regulating ball seat (7.15), gas injection packer (7), and pump barrel (8) to the designated position in the well. At the wellhead on the surface, pressurize the pump barrel (8) to allow liquid to enter the well along the pump barrel (8) and push the piston (7.3) along the sealing hole (7.14) to cut the sealing shear pin (7.4). Continue to push the sealing rubber sleeve (7.5) downward to expand it and achieve the setting of the gas injection packer (7). Then, continue to pressurize to knock off the pressure-regulating ball seat (7.15) and let it fall into the inner cavity of the transition adapter (10), and the lower end of the transition adapter (10) is a closed plug head structure. Then, lower the plunger pump (9) into the pump barrel (8) to complete the installation. Second, natural gas is injected into the gas supply pipeline (5) through the surface natural gas pressurization injection device. The natural gas enters the heavy oil reservoir (1) along the gas injection packer (7) and the downhole natural gas booster pump (4). The pressurized natural gas is in continuous contact with the heavy oil to reduce the viscosity of the heavy oil and increase its fluidity. Then, it is extracted to the surface by the plunger pump (9). When natural gas passes through the gas injection channel (7.12) of the gas injection packer (7), the natural gas pushes the pressure transmission control piston (7.8) to move down, causing the oil inlet / outlet control valve (7.9) to move down to the oil inlet (7.13) to form a closed state. At the same time, the return spring (7.10) stores elastic potential energy. As the pressure transmission control piston (7.8) moves down, the natural gas enters the gas supply pipeline (5) below through the annulus formed between the unsealed pressure transmission sleeve (7.7) and the central tube (7.1) and the gas injection channel outlet (7.7.1), and then enters the downhole natural gas booster pump (4). In addition, after natural gas enters the main natural gas inlet (4.9) of the downhole natural gas booster pump (4), the natural gas pushes the large-displacement gas injection check valve (4.6) to open, and at the same time drives the booster piston (4.1) to move downward to the lower stop point. Then, the natural gas pushes open the anti-sticking check valve (4.5), so that the natural gas enters the cavity formed between the artificial bottom (2), the casing (3) and the gas injection packer (7), and then enters the heavy oil reservoir (1) along the perforation area (3.1) distributed on the casing (3). When the pressure of the natural gas from the ground balances with the pressure of the natural gas injected into the heavy oil reservoir (1), the booster injection mode is activated. The large-displacement gas injection check valve (4.6) returns to its closed position under the action of the first compression spring (4.6.3). The booster piston (4.1) moves upward to its initial position under the action of the auxiliary spring (4.14). At the same time, natural gas will move downward along the natural gas exchange channel (4.11) and open the second differential pressure check valve (4.7), and then enter the low-pressure sealed cylinder liner (4.2) along the exchange channel (4.15). Then, the booster piston (4.1) due to... Under the influence of the area difference, it continues to move downward to the lower dead point, pressurizing the natural gas in the high-pressure sealing cylinder liner (4.3). At the same time, the natural gas between the low-pressure sealing cylinder liner (4.2) and the pressurizing piston (4.1) moves downward along the pressurizing gas exchange main channel (4.12). After opening the first differential pressure check valve (4.4), it enters the high-pressure sealing cylinder liner (4.3) along the pressurizing gas inlet channel (4.13). Then, the pressurized natural gas is sent into the heavy oil reservoir (1). Then, the pressurizing piston (4.1) moves back and forth until it finally reaches equilibrium, completing the pressurization injection of natural gas and increasing the viscosity reduction range of the heavy oil reservoir (1).

3. After the natural gas pressurization injection is completed, the gas injection is stopped. At this time, the gas supply pressure of the gas supply pipeline (5) is released. Due to the high formation pressure in the heavy oil reservoir (1), backflow will occur. At this time, the anti-sticking check valve (4.5) is closed to prevent oil from entering the downhole natural gas booster pump (4). At the same time, due to the disappearance of the pressure in the gas supply pipeline (5), the oil inlet / outlet control valve (7.9) is pushed upward by the return spring (7.10) to move away from the oil inlet hole. (7.13) When the oil is in the open state, the viscosity-reduced oil in the heavy oil reservoir (1) enters the inner cavity of the pump barrel (8) through the oil inlet hole (7.13), and then the viscosity-reduced oil is extracted to the surface by the plunger pump (9). As the viscosity-reduced oil is continuously extracted, the viscosity of the remaining heavy oil increases until it is not suitable for extraction. Then the operation of the plunger pump (9) is stopped, and natural gas is injected again to continue to reduce the viscosity of the heavy oil in the heavy oil reservoir (1). The cycle is repeated to realize the extraction of heavy oil.

9. The method of using the device for injecting natural gas into the well to increase pressure and achieve viscosity reduction and huff-and-puff production of heavy oil according to claim 8, characterized in that: When well workover is required, the tubing string is lifted up to cut the unsealing shear pin (7.6), disconnecting the unsealing pressure transmission sleeve (7.7) from the central tube (7.1), causing the unsealing pressure transmission sleeve (7.7) to shift, thereby causing the expanded sealing rubber sleeve (7.5) to separate from the inner wall of the casing (3). Then, the entire tubing string, downhole natural gas booster pump (4), transition adapter (10), gas supply line (5), gas injection packer (7), and pump barrel (8) are lifted to the surface as a whole.

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