A device and method for gas power fracturing thermal oxidation of plugging of a polymer injection well

Abstract

The application discloses a device and method for gas power fracturing thermal oxidation plugging removal of a polymer injection well, in which, two sealing rubbers are synchronously set by bridge plug gunpowder control, isolation of the oil layer and the wellbore is realized, high-temperature gas mainly containing oxygen generated by combustion of a solid chemical oxygen generating agent is injected into the annulus and the oil layer which has been isolated under the condition of upper and lower plugging, and the high-temperature and high-pressure gas reaches the fracturing pressure of the stratum, so that the stratum is fractured and new fractures are generated in the oil layer; with continuous combustion of the solid chemical oxygen generating agent, heat and oxygen penetrate and expand to the deep part of the oil layer through the perforation hole and the fractures, and the range of thermal oxidation degradation is further expanded; after the combustion of the agent is completed, the agent remains in the downhole and keeps the set state for 24-48 hours; then, the set state is removed by secondary ignition, the device is pulled out through a cable, the PT instrument in the device is taken out, and the pressure and temperature data in the isolated space from 30 minutes before the first ignition are read on a computer.

Description

Technical Field

[0001] This invention relates to fracturing of polymer injection wells in oil fields and thermal oxidation degradation and unblocking of polymer gels, belonging to the field of tertiary oil recovery technology. Background Technology

[0002] While injecting polymer-infused aqueous solutions into oil reservoirs for tertiary oil recovery revitalizes wells, it inevitably introduces the technological challenge of polymer gel blockage. The blockage typically consists of a mixture of organic and inorganic scale, primarily polymer gel. The main cause of polymer gel formation is the cross-linking and complexation effect of divalent and trivalent metal ions (such as iron, magnesium, and calcium) in the injection pipeline and formation, primarily occurring in the near-wellbore zone near the polymer solution injection point. Formation blockage leads to increased injection pressure and difficulties in water injection.

[0003] Research and experimentation on polymer gel deblocking began abroad in the 1980s, while related work in China started around 2000. Domestic and international research and experiments have shown that oxidative degradation of the gel is the most effective and practical deblocking technique. Domestic oilfields previously used strong oxidants such as hydrogen peroxide and chlorine dioxide for gel deblocking, but this method was discontinued due to pipeline explosions and injuries that occurred during injection. Subsequently, weak oxidants such as sulfides and peroxides (CN103881673A), surfactants (CN102925128B), and a deblocking technique that generates chlorine dioxide downhole (CN112852396A) were used. However, due to the complexity of the formulation and construction process, and the limitation on the concentration of the injected deblocking agent due to pipeline and equipment corrosion, a simple and efficient polymer gel deblocking method has yet to be found.

[0004] In order to explore a simple, efficient, and rapid polymer gel deblocking technology to solve the headache of the lack of a low-cost, fast, and effective deblocking method in tertiary oil recovery production, the inventors started from the physical and chemical properties of polymer aqueous solutions and their gels. Based on the common characteristics of all polymer aqueous solutions and their gels, namely that the viscosity of all polymer aqueous solutions and their gels decreases rapidly with increasing temperature, and that oxygen in the air and ultraviolet light can also significantly reduce their viscosity and increase their fluidity during storage, and considering the theoretical characteristics that the combined effect of heat and oxygen can rapidly reduce the viscosity of polymer aqueous solutions and rapidly thermally oxidize and degrade the gel to restore its fluidity, and that this thermal oxidative degradation chemical reaction is irreversible, the inventors developed a device and method for efficient deblocking. Summary of the Invention

[0005] To overcome the aforementioned problems, the inventors conducted in-depth research and designed a device and method for thermal oxidation unblocking of polymer injection wells using gas-fired dynamic fracturing. In this device and method, two sealing rubbers are simultaneously set by a bridge plug propellant, isolating the oil layer from the wellbore. High-temperature gas, primarily composed of oxygen, generated by the combustion of a solid chemical oxygen generator is injected into the already sealed annulus and oil layer, even with both upper and lower seals. The instantaneous high-temperature, high-pressure gas reaches the formation fracturing pressure, first fracturing the formation and then creating new fractures in the oil layer. As the solid chemical oxygen generator continues to burn, heat and oxygen are released through the perforation channels... The fractures penetrate and extend into the deeper oil layer, further expanding the reach of thermal oxidative degradation. After the propellant charge burns out, although the pressure of the sealed system decreases, the heat and oxygen in the sealed state continue to degrade the surrounding polymer gel. The device remains in the well for 24-48 hours to maintain its set state, allowing all the heat and oxygen to be used for the thermal degradation of the polymer gel, thus relieving blockage in more distant formations. The set state is then released by secondary ignition, and the device is pulled out via cable. The PT instrument in the device is retrieved, and the pressure and temperature data in the sealed space from 30 minutes before the first ignition are interpreted on a computer, thus completing the invention.

[0006] Specifically, the purpose of this invention is to provide a device for thermal oxidation unblocking of gas-fired fracturing in polymer injection wells. The device includes, from top to bottom, a diffuser sealing device 1, a combustion chamber 2, a diffuser sealing device 2 3, and a PT instrument protective sleeve 4.

[0007] The diffuser sealing device 1 and the diffuser sealing device 2 both include a sealing rubber sleeve. The sealing rubber is deformed by the bridge plug gunpowder 16, and then simultaneously sets the seal at the upper and lower ends of the combustion chamber 2 to achieve isolation between the oil layer and the wellbore.

[0008] The combustion chamber 2 is filled with a ignition block 14 and a solid chemical oxygen generator (SOG) column 5. The SOG column 5 can be ignited by the ignition block 14. A pressure relief hole 6 is provided on the SOG column 5. After the SOG column 5 is ignited, it generates a high-temperature gas mainly composed of oxygen. This gas is directly injected into the sealed annulus and oil layer through the pressure relief hole 6. The instantaneous high-temperature and high-pressure gas reaches the formation fracturing pressure and first causes formation fracturing, then creates new fractures in the oil layer. As the SOG column continues to burn, the high-temperature gas penetrates and expands into the deeper oil layer through perforations and fractures, further expanding the scope of thermal oxidation degradation.

[0009] The PT instrument 7 is installed in the PT instrument protective sleeve 4;

[0010] A first through hole 8 is provided in the second diffuser sealing device 3. One end of the first through hole 8 is connected to the protective sleeve 22 of the PT instrument, and the other end is connected to the outside of the device. The connection position is between the two sealing points. This is to enable the PT instrument 7 to measure the pressure and temperature near the device after the solid chemical oxygen generator column 5 is ignited.

[0011] The device is equipped with a centering device 9 and a guide head 10 at its lower end, and a centering device 9 and a magnetic positioning connector 11 at its upper end.

[0012] After the diffuser sealing device 1 and the diffuser sealing device 2 are set, the built-in bridge plug gunpowder 19 can be ignited by the second ignition head 17, which increases the internal pressure. The high pressure then pushes off the sealing plug 21, and the internal pressure is released through the pressure relief channel 20, thereby releasing the set seal. Then the device can be lifted out of the ground.

[0013] The present invention also provides a method for thermal oxidation unblocking of gas-fired fracturing in polymer injection wells, which is implemented by the apparatus described above for thermal oxidation unblocking of gas-fired fracturing in polymer injection wells.

[0014] The method includes the following steps:

[0015] Step 1: Assemble the gas-fired fracturing thermal oxidation unblocking device for polymer injection wells into a long cylindrical shape according to a predetermined sequence, and add bridge plug explosive and solid chemical oxygen generator charge to it;

[0016] Step 2: Lower the assembled self-sealing gas-powered fracturing reservoir unit to the reservoir location via cable;

[0017] Step 3: The ignition head ignites the bridge plug propellant 16. The gas from the bridge plug propellant 16 pushes the pressure sealing rubber sleeves on the diffuser sealing device 1 and the diffuser sealing device 2 through the gas passage 15 to achieve simultaneous upper and lower sealing, thereby isolating the oil layer from the wellbore. The gas from the bridge plug propellant also cuts the safety pin device 12 and impacts and ignites the impact ignition head 13. The impact ignition head 13 ignites the ignition transfer block 14, which in turn ignites the solid chemical oxygen generator column 5.

[0018] Step 4: After the dwell time is reached, the device is ignited a second time to release the setting seal, the device is lifted to the ground, and the data information obtained from the PT instrument is read.

[0019] In step 3, after the solid chemical oxygen generator 5 is ignited, the resulting high-temperature and high-pressure gas, mainly composed of oxygen, is directly injected into the already sealed annulus and oil layer through the pressure relief hole 6 of the device. The instantaneous high-temperature and high-pressure gas reaches the formation fracturing pressure, causing the formation to fracture and creating new fractures in the oil layer. As the solid chemical oxygen generator 5 continues to burn, the high-temperature and high-pressure gas penetrates and expands into the deeper oil layer through the perforation channels and fractures, further expanding the scope of thermal oxidation degradation. After the solid chemical oxygen generator 5 has finished burning, although the pressure of the closed system has decreased, the high-temperature and high-pressure gas, mainly composed of oxygen, can continue to degrade the surrounding polymer gel in the closed state.

[0020] In step 4, the residence time is 24h-48h.

[0021] The beneficial effects of this invention include:

[0022] (1) The apparatus and method for thermal oxidation unblocking of polymer injection wells by gas-powered fracturing according to the present invention can effectively degrade polymer gel by high-temperature oxygen, thereby achieving unblocking.

[0023] (2) According to the apparatus and method for thermal oxidation unblocking of polymer injection wells by gas-powered fracturing provided by the present invention, the apparatus and method can slowly release hot oxygen for a long time and can continuously seal for 24h-48h in order to unblock formations in a more distant range.

[0024] (3) According to the apparatus and method for thermal oxidation unblocking of polymer injection wells by gas-powered fracturing provided by the present invention, the apparatus and method degrade polymer gel in situ and quantitatively in the annulus and oil layer closed environment. Since no other chemical additives are injected into the oil layer except for hot oxygen and a small amount of gas during construction, the backflow and well washing procedures can be eliminated after the thermal oxidation degradation unblocking construction. Attached Figure Description

[0025] Figure 1 This is a cross-sectional view of the overall structure of the apparatus for thermal oxidation unblocking of gas-fired fracturing in polymer injection wells according to this application;

[0026] Figure 2 Show Figure 1 A magnified view of a portion of region A in the middle;

[0027] Figure 3 Show Figure 1 A magnified view of a portion of region B in the middle;

[0028] Figure 4 Show Figure 1 A magnified view of a portion of region C in the middle;

[0029] Figure 5 Show Figure 1A magnified view of a portion of region D.

[0030] Explanation of reference numerals in the attached figures

[0031] 1-Diffuser-type sealing device

[0032] 2-Combustion Chamber

[0033] 3-Diffuser Sealing Device II

[0034] 4-PT instrument protective cover

[0035] 5-Solid Chemical Oxygen Generator Column

[0036] 6-Pressure relief hole

[0037] 7-PT instrument

[0038] 8-First through hole

[0039] 9-Center

[0040] 10-Guide Head

[0041] 11-Magnetic positioning connector

[0042] 12-Safety pin device

[0043] 13-Impact Igniter

[0044] 14-Ignition Powder Block

[0045] 15-Gas passage

[0046] 16-Bridge plug gunpowder

[0047] 17-Second electric ignition head

[0048] 18-First Electric Ignition Head

[0049] 19-Built-in bridge plug gunpowder

[0050] 20-Unloading gas passage

[0051] 21-Sealing plug

[0052] 22-PT instrument protective cover Detailed Implementation

[0053] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Through these descriptions, the features and advantages of the present invention will become clearer and more apparent.

[0054] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments. Although various aspects of embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated otherwise.

[0055] This invention provides a device for thermal oxidation unblocking of polymer injection wells via gas-fired fracturing, such as... Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 As shown in the figure, the device includes, from top to bottom, a diffuser sealing device 1, a combustion chamber 2, a diffuser sealing device 2 3, and a PT instrument protective sleeve 4;

[0056] Both the diffuser-type sealing device 1 and the diffuser-type sealing device 3 include sealing rubber sleeves. The sealing rubber is deformed by the propellant 16 of the bridge plug, thereby simultaneously setting the seal at both ends of the combustion chamber 2, isolating the oil layer from the wellbore. This allows the gas discharged from the combustion chamber 2 to be directly injected into the annulus and oil layer, achieving efficient unblocking. In this application, "setting the seal" refers to sealing the tubing or well to achieve vertical separation.

[0057] The combustion chamber 2 is filled with a ignition block 14 and a solid chemical oxygen generator (SOG) column 5. The SOG column 5 can be ignited by the ignition block 14. A pressure relief hole 6 is provided on the SOG column 5. After the SOG column 5 is ignited, it generates a high-temperature gas mainly composed of oxygen. This gas is directly injected into the sealed annulus and oil layer through the pressure relief hole 6. The instantaneous high-temperature and high-pressure gas reaches the formation fracturing pressure and first causes formation fracturing, then creates new fractures in the oil layer. As the SOG column continues to burn, the high-temperature gas penetrates and expands into the deeper oil layer through perforations and fractures, further expanding the scope of thermal oxidation degradation.

[0058] The solid chemical oxygen generator propellant column comprises a solid chemical oxygen generator, which is a chemical oxygen-generating agent. Its principle is to produce oxygen through the chemical reaction of chlorate. This solid chemical oxygen generator is a solid oxygen source with high oxygen storage capacity, easy storage, and safe and convenient use; its oxygen storage capacity is approximately three times that of compressed oxygen of the same volume. It is now widely used in emergency oxygen supply for civil aviation passengers, backup oxygen for space stations, and emergency oxygen supply for rescue. The solid chemical oxygen generator in this invention not only does not require cooling and filtration, but also maintains the oxygen at a high temperature of 600-1000℃ inside the device, while the temperature gradually decreases outside the device. Therefore, the solid chemical oxygen generator used in this invention is specifically called a "solid chemical thermal oxygen generator." The solid chemical thermal oxygen generator is made into solid propellant columns and sequentially loaded into the combustion chamber of the device. The number and amount of propellant columns are determined by the scalability of thermal oxidation degradation.

[0059] The solid chemical oxygen generator propellant column in this application has the characteristics of low burning rate, moderate burning temperature, and high oxygen content in the fuel gas.

[0060] In a preferred embodiment, a PT instrument 7 is disposed in the PT instrument protective sleeve 4;

[0061] A first through hole 8 is provided in the diffuser-type sealing device 3. One end of the first through hole 8 is connected to the protective sleeve 4 of the PT instrument, and the other end is connected to the outside of the device. The connection position is between the two setting points. This allows the PT instrument 7 to measure the pressure and temperature near the device after the solid chemical oxygen generator column 5 is ignited. The PT instrument in this application only needs to be able to measure temperature and pressure and store the data.

[0062] In a preferred embodiment, a centering device 9 and a guide head 10 are provided at the lower end of the device, and a centering device 9 and a magnetic positioning connector 11 are provided at the upper end of the device, thereby facilitating the lowering of the device into the oil well in the form of a columnar structure.

[0063] In a preferred embodiment, after the diffuser sealing device 1 and the diffuser sealing device 2 3 are set, the setting can be released by secondary ignition, thereby lifting the device out of the ground.

[0064] The present invention also provides a method for thermal oxidation unblocking of gas-fired fracturing in polymer injection wells, which is implemented by the aforementioned apparatus for thermal oxidation unblocking of gas-fired fracturing in polymer injection wells.

[0065] Preferably, the method includes the following steps:

[0066] Step 1: Assemble the gas-fired fracturing thermal oxidation unblocking device for polymer injection wells into a long cylindrical shape according to a predetermined sequence, and add bridge plug explosive and solid chemical oxygen generator charge to it;

[0067] Step 2: Lower the assembled self-sealing gas-powered fracturing reservoir unit to the reservoir location via cable;

[0068] Step 3: The first ignition head 18 is turned on to ignite the bridge plug explosive 16. The gas from the bridge plug explosive 16 pushes the pressure sealing rubber sleeves on the diffuser sealing device 1 and the diffuser sealing device 2 to achieve simultaneous upper and lower sealing, thereby isolating the oil layer from the wellbore. The gas from the bridge plug explosive 16 also cuts the safety pin device 12 and impacts and ignites the ignition block 14, while simultaneously igniting the solid chemical oxygen generator column 5.

[0069] Step 4: After the dwell time is reached, the device is ignited a second time to release the setting seal, and the device is lifted out of the ground. The data stored in the PT instrument is then read by a computer.

[0070] Preferably, in step 3, after the solid chemical oxygen generator column 5 is ignited, the generated high-temperature and high-pressure gas, mainly composed of oxygen, is directly injected into the already sealed annulus and oil layer through the pressure relief hole 6 of the device. The instantaneous high-temperature and high-pressure gas reaches the formation fracturing pressure, causing the formation to fracture and creating new fractures in the oil layer. As the solid chemical oxygen generator column continues to burn, the high-temperature and high-pressure gas penetrates and expands into the deeper oil layer through the perforation channels and fractures, further expanding the scope of thermal oxidation degradation. After the solid chemical oxygen generator column has finished burning, although the pressure of the closed system has decreased, the high-temperature and high-pressure gas, mainly composed of oxygen, in the closed state can continue to degrade the surrounding polymer gel.

[0071] Preferably, in step 4, the retention time is 24h-48h, preferably 48 hours, in order to fully unblock the blockage.

[0072] Example

[0073] A solid chemical oxygen generator column was installed in a heat exchanger and ignited. The gas produced by its combustion was controlled to be introduced into a thick-walled quartz experimental tube containing polyacrylamide gel at 80°C and 60°C to carry out a thermo-oxygen reaction. The pressure was 0.25 MPa. The specific reaction table is as follows:

[0074] Table 1. Thermo-oxidative reaction of polyacrylamide gel

[0075] 1 0.25 80 3 minutes The congestion was reduced by approximately 0.5%. visual observation 2 0.25 80 10 minutes The congestion was reduced by about 2%. visual observation 3 0.25 80 15 minutes Congestion eased by approximately 21%. visual observation 4 0.25 80 20 minutes The congestion has been reduced by about 75%. visual observation 5 0.25 80 25 minutes The congestion was reduced by approximately 1.5%. visual observation

[0076] Table 2. Thermo-oxidative reaction of polyacrylamide gel

[0077]

[0078]

[0079] Experimental results

[0080] At 80°C, hot oxy-fuel gas causes the gel surface to melt and flow within 2-3 minutes, becomes fluid within 15 minutes, and flows almost completely within 20 minutes.

[0081] At 60°C, hot oxy-fuel gas causes the gel surface to melt and flow within 3-5 minutes, becomes fluid within 18 minutes, and flows almost completely within 25 minutes.

[0082] The results above show that hot oxygen at 60℃-80℃ can effectively deblock polyacrylamide gel. The solid chemical oxygen generator column provided in this application can generate hot oxygen at 600℃-1000℃ in the device. The temperature of the hot oxygen will drop significantly after entering the formation. The degree of temperature drop varies depending on the formation temperature, but most of the hot oxygen can be maintained above 60℃. Moreover, the higher the temperature, the better the degradation effect. Therefore, it can be seen that the solid chemical oxygen generator column provided in this application can effectively relieve the problem of polymer gel blockage.

[0083] The present invention has been described above with reference to preferred embodiments; however, these embodiments are merely exemplary and illustrative. Various substitutions and modifications can be made to the present invention based on these embodiments, all of which fall within the scope of protection of the present invention.

Claims

1. A device for thermal oxidation unblocking of polymer injection wells using gas-fired fracturing, characterized in that, The device consists of, from top to bottom, a diffuser sealing device one (1), a combustion chamber (2), a diffuser sealing device two (3), and a PT instrument protective sleeve (4). Among them, the first diffuser sealing device (1) and the second diffuser sealing device (3) both include sealing rubber and bridge plug gunpowder. The sealing rubber is deformed by the bridge plug gunpowder, and then simultaneously set at the upper and lower ends of the combustion chamber (2) to achieve the isolation of the oil layer from the wellbore. The combustion chamber (2) is filled with a ignition block (14) and a solid chemical oxygen generator (5). The ignition block (14) is equipped with an impact igniter (13) and a safety pin device (12). The solid chemical oxygen generator (5) can be ignited by the detonated bridge plug propellant. The gas from the bridge plug propellant (16) shears off the safety pin device (12) and impacts the impact igniter (13), thereby igniting the ignition block (14) and simultaneously igniting the solid chemical oxygen generator (5). A pressure relief hole (6) is provided for the solid chemical oxygen generator column (5). After the solid chemical oxygen generator column (5) is ignited, it generates a high-temperature gas mainly composed of oxygen. The gas is directly injected into the sealed annulus and oil layer through the pressure relief hole (6). The instantaneous high-temperature and high-pressure gas reaches the formation fracturing pressure and first causes the formation to fracture, causing new fractures in the oil layer. As the solid chemical oxygen generator column continues to burn, the high-temperature gas penetrates and expands into the deeper part of the oil layer through the perforation channel and fractures, further expanding the scope of thermal oxidation degradation. After the diffuser sealing device one (1) and the diffuser sealing device two (3) are set, the setting can be released by secondary ignition, thereby lifting the device out of the ground.

2. The apparatus for thermal oxidation unblocking of polymer injection wells using gas-fired dynamic fracturing according to claim 1, characterized in that, A PT instrument (7) is installed in the PT instrument protective sleeve (4); A first through hole (8) is provided in the second diffuser sealing device (3). One end of the first through hole (8) is connected to the protective sleeve (4) of the PT instrument, and the other end is connected to the outside of the thermal oxidation unblocking device. The connection position is between the two setting points. This is so that the PT instrument (7) can measure the pressure and temperature near the thermal oxidation unblocking device after the solid chemical oxygen generator column (5) is ignited.

3. The apparatus for thermal oxidation unblocking of fuel gas-fired fracturing in polymer injection wells according to claim 1, characterized in that, A centering device and a guide head are also provided at the lower end of the thermal oxidation unblocking device, and a centering device and a magnetic positioning connector are also provided at the upper end of the thermal oxidation unblocking device.

4. A method for thermal oxidation unblocking of polymer injection wells via gas-fired fracturing, characterized in that, This method is achieved using the apparatus for thermal oxidation unblocking of gas-fired fracturing in polymer injection wells as described in any one of claims 1 to 3.

5. The method for thermal oxidation unblocking of a polymer injection well via gas-fired fracturing according to claim 4, characterized in that, The method includes the following steps: Step 1: Assemble the gas-fired fracturing thermal oxidation unblocking device for polymer injection wells into a long cylindrical shape according to a predetermined sequence, and add bridge plug explosive and solid chemical oxygen generator charge to it; Step 2: Lower the assembled self-sealing gas-powered fracturing reservoir unit to the reservoir location via cable; Step 3: The ignition head is turned on to ignite the bridge plug propellant. The gas from the bridge plug propellant pushes the pressure sealing rubber on the first (1) and the second (3) diffuser sealing devices to achieve simultaneous upper and lower sealing, thereby isolating the oil layer from the wellbore. The gas from the bridge plug propellant also cuts off the safety pin device and ignites the solid chemical oxygen generator propellant column (5). Step 4: After the dwell time is reached, the device is ignited a second time to release the setting seal, the device is lifted to the ground, and the data information obtained from the PT instrument is read.

6. The method for thermal oxidation unblocking of a polymer injection well via gas-fired fracturing according to claim 5, characterized in that, In step 3, after the solid chemical oxygen generator (5) is ignited, the high-temperature and high-pressure gas generated, which is mainly composed of oxygen, is directly injected into the annulus and oil layer that have been set up through the pressure relief hole (6) of the device. The instantaneous high-temperature and high-pressure gas reaches the formation fracturing pressure and causes the formation to fracture, resulting in new fractures in the oil layer. As the solid chemical oxygen generator continues to burn, the high-temperature and high-pressure gas penetrates and expands into the deep part of the oil layer through the perforation channel and fractures, further expanding the scope of thermal oxidation degradation. After the solid chemical oxygen generator has finished burning, although the pressure of the closed system has decreased, the high-temperature and high-pressure gas, which is mainly composed of oxygen, can continue to degrade the surrounding polymer gel in the closed state.

7. The method for thermal oxidation unblocking of a polymer injection well via gas-fired fracturing according to claim 5, characterized in that, In step 4, the residence time is 24h-48h.

Images