A method for underground in-situ combustion of low permeability oil reservoirs, oil shales and shale oil reservoirs based on chemical spontaneous ignition

Abstract

The invention discloses an underground in-situ combustion method for low permeability oil reservoirs, oil shale and shale oil reservoirs based on chemical spontaneous ignition, and relates to the technical field of oil and gas extraction. The method comprises: injecting a chemical spontaneous ignition composition and an oxidant into the oil reservoir, and the chemical spontaneous ignition composition comprises, by mass percentage, ignition agent 20%-45%, fuel additive 10%-20%, combustion improver 8%-12%, catalyst 3%-5%, emulsifier 2%-3%, and the balance is water. The invention discloses an underground in-situ combustion method for low permeability oil reservoirs, oil shale and shale oil reservoirs based on chemical spontaneous ignition, and through the optimized combination of ignition agent, combustion improver, catalyst, emulsifier and fuel additive, a spontaneous combustion reaction can be quickly induced in the oil reservoir, and a stable high-temperature combustion process can be maintained; the method is applicable to the exploitation of low permeability oil reservoirs, oil shale, shale oil reservoirs and sandstone oil reservoirs, and can significantly improve the recovery rate, and is particularly applicable to complex oil reservoir conditions where conventional oil displacement technology is difficult to effectively apply.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas exploitation, and in particular to an underground in-situ combustion method for low-permeability oil reservoirs, oil shale and shale oil reservoirs based on chemical spontaneous ignition. Background Art

[0002] Low permeability reservoirs, oil shales and shale reservoirs are unconventional oil and gas resources with low reservoir permeability and small porosity. Conventional oil production technology has poor application effect in these reservoirs, resulting in low recovery rate.

[0003] Low permeability reservoirs refer to reservoirs with a permeability of less than 1mD. They usually have a dense reservoir structure and poor fluid mobility. Conventional oil production methods are difficult to achieve high recovery rates in these reservoirs. In low permeability reservoirs, it is difficult for oil and gas to flow through the pores and cracks of the reservoir, so conventional water drive and gas drive methods are less efficient. In order to improve the recovery rate of low permeability reservoirs, fracturing technology is widely used in such reservoirs to increase the flow channels of oil and gas through the formation of cracks. However, it is still difficult to overcome the low permeability of the reservoir by simply relying on fracturing or injecting external energy. How to provide additional energy inside the reservoir to promote the flow of oil and gas has become an urgent problem to be solved.

[0004] Oil shale is a sedimentary rock with a high content of organic matter (called kerogen), which has the potential to be decomposed by heating to produce combustible liquid and gaseous fuels. However, due to the extremely low permeability of oil shale, it is almost impossible to directly obtain oil and gas resources through conventional mining technology. Traditional oil shale mining methods include ground pyrolysis and underground heating. Among them, underground heating (such as underground in-situ combustion) is considered to be a more economical development method, which can use the heat generated by underground combustion to promote the pyrolysis reaction of oil shale and release shale oil. However, in actual applications, underground in-situ combustion technology faces problems such as difficulty in ignition, uneven propagation of the combustion front, and difficulty in effectively utilizing the thermal effect, which limits the breadth of application of this technology. Therefore, it is of great significance to find an efficient and economical ignition method and combustion process control method to achieve effective mining of oil shale.

[0005] Shale oil reservoirs refer to oil and gas resources existing in shale layers rich in organic matter. Unlike conventional oil reservoirs, shale oil reservoirs have extremely low permeability and porosity, and the oil and gas occurrence state is complex. In recent years, the combination of fracturing and horizontal well technology has enabled the large-scale development of shale oil and gas resources. However, due to the dense structure of shale oil reservoirs, while fracturing technology increases fracture channels, it is still difficult to improve the fluidity of oil and gas on a large scale, resulting in a low recovery rate. Shale oil reservoirs are rich in resources, but due to the physical properties of the reservoir, conventional production-increasing measures have limited effects. Therefore, how to introduce additional energy into shale oil reservoirs to improve oil and gas fluidity has become a key technical bottleneck for improving shale oil recovery.

[0006] In-Situ Combustion (ISC) is an enhanced oil recovery technology that ignites part of the crude oil or organic matter inside the reservoir and uses the heat and gas generated by the combustion to drive the remaining oil and gas to flow to the production well. This technology has great potential for application in oil shale, low permeability reservoirs and shale reservoirs. The combustion process can not only generate a large amount of heat to reduce the viscosity of the crude oil in the reservoir, but also promote the flow of oil and gas through the gas generated by the combustion.

[0007] Although underground in-situ combustion has shown good prospects in improving oil and gas recovery, its application still faces a series of technical challenges, including:

[0008] (1) Ignition is difficult. Traditional underground in-situ combustion ignition methods (such as electric heating, injection burners, etc.) are complex and costly, and it is difficult to achieve uniform ignition in low permeability reservoirs.

[0009] (2) The ignition process is poorly controllable, which may result in the inability to start combustion or unstable combustion propagation.

[0010] (3) The propagation of the combustion front is difficult to control. In heterogeneous reservoirs, the propagation speed and direction of the combustion reaction are difficult to accurately control, which can easily lead to incomplete or uncontrolled combustion, thus affecting the overall recovery effect.

[0011] (4) The thermal utilization efficiency of the oil reservoir is low. In low-permeability and dense reservoirs, the heat generated by combustion is difficult to be fully conducted in the reservoir, resulting in low thermal energy utilization, which affects the oil recovery effect.

[0012] In response to the ignition difficulties and combustion process control problems of underground in-situ combustion technology, researchers have proposed an underground in-situ combustion technology based on chemical spontaneous ignition. This method injects specific chemical reagents (such as oxidants and reductants) to cause chemical reactions in underground oil reservoirs, releasing a large amount of heat and inducing spontaneous combustion of oil shale, shale oil or crude oil in the reservoir. Compared with traditional external ignition methods, this technology has the advantages of simple operation, low cost, and a more uniform and controllable ignition process.

[0013] In oil shale and shale reservoirs, chemical spontaneous ignition can effectively overcome the problem of insufficient heat conduction due to low permeability, ensuring that the combustion reaction can be evenly expanded in the reservoir. In addition, by adjusting the type and injection amount of chemical reagents, the propagation speed and range of the combustion front can be accurately controlled to avoid problems such as runaway combustion or excessive cooling, thereby improving thermal energy utilization efficiency and recovery rate. Summary of the invention

[0014] To solve the above problems, the present invention provides an underground in-situ combustion method for low permeability oil reservoirs, oil shales and shale oil reservoirs based on chemical spontaneous ignition. The spontaneous chemical reaction of specific chemical reagents is used to trigger an exothermic reaction in the underground oil reservoir to generate sufficient heat to make the organic matter or shale oil in the oil shale reach the autoignition temperature, thereby forming a combustion reaction. The high temperature generated by the combustion further promotes the thermal decomposition or flow of oil and gas, and the gas released by the combustion reaction plays an oil displacement role, pushing the remaining oil and gas in the oil reservoir to the production well, thereby achieving efficient oil recovery.

[0015] To achieve the above-mentioned purpose, the present invention provides an underground in-situ combustion method for low-permeability oil reservoirs, oil shales and shale oil reservoirs based on chemical spontaneous ignition, which is achieved by injecting a chemical spontaneous ignition composition and an oxidant into the oil reservoir, wherein the chemical spontaneous ignition composition comprises, by mass percentage, 20%-45% ignition agent, 10%-20% fuel additive, 8%-12% combustion aid, 3%-5% catalyst, 2%-3% emulsifier, and the balance is water; the oxidant is air or oxygen.

[0016] Preferably, the ignition agent is one or a combination of hydrogen peroxide, sodium peroxide, potassium permanganate.

[0017] Preferably, the fuel additive is alcohol and / or low alkyl derivatives of boron, aluminum, zinc and / or organic peroxide and / or hypergolic liquid;

[0018] The lower alkyl derivatives of boron, aluminum and zinc include trimethylborane, triethylborane, triisopropylborane, tributylborane, trimethylaluminum, triethylaluminum, diisobutylaluminum hydride, triisobutylaluminum, diethylzinc, di-n-butylzinc or diisopropylzinc;

[0019] Organic peroxides include benzoyl peroxide, dicumyl peroxide, tert-butyl perbenzoate, tert-butyl peroxyacetate, tert-butyl peroxyisobutyrate, tert-butyl peroxycyclohexanecarboxylate or methyl isobutyl ketone peroxide;

[0020] Spontaneous ignition liquids include linseed oil, linoleic acid, tung oil and mixtures thereof with tall oils or unsaturated fatty compounds.

[0021] Preferably, the combustion improver includes potassium nitrate, sodium nitrate, and ammonium nitrate.

[0022] Preferably, the catalyst comprises a transition metal oxide, an organometallic compound, cobalt octoate, or iron octoate;

[0023] Transition metal oxides include Fe2O3, CuO, Fe3O4, MnO2, NiO, CrO2;

[0024] The organometallic compounds include iron naphthenate, cobalt naphthenate, nickel naphthenate, and copper naphthenate.

[0025] Preferably, the emulsifier includes anionic surfactants and nonionic surfactants;

[0026] Anionic surfactants include sodium lauryl sulfate and sodium alkylbenzene sulfonate;

[0027] Non-ionic surfactants include polyethylene glycol, Tween series, and alkylphenol polyoxyethylene ether.

[0028] Preferably, the injection method of the chemical spontaneous ignition composition includes a staged injection method and a co-injection method.

[0029] Preferably, when the reservoir structure is heterogeneous, layered or fractured, a staged injection method is used to first inject the oxidant and catalyst into the reservoir, then inject the ignition agent, combustion aid and emulsifier at different depths and locations through staged injection, and finally inject the fuel additive.

[0030] Fuel additives are usually injected after the ignition agent and the combustion aid are injected. The purpose of this is to ensure that the oxidant and catalyst in the reservoir have been distributed first, and after the combustion precursor conditions at different depths and locations are achieved, the fuel additives are injected to facilitate smooth ignition and improve the efficiency and stability of combustion.

[0031] Preferably, when the reservoir structure is uniform and dense, a co-injection method is used, and the chemical spontaneous ignition composition is premixed according to a formula and then injected through the injection well at one time.

[0032] Preferably, the process of injecting the chemical spontaneous ignition composition into the oil reservoir and then recovering the oil and gas resources comprises:

[0033] S1. After the chemical spontaneous ignition composition is injected into the oil reservoir, it spontaneously ignites. The heat released by the spontaneous ignition heats the crude oil or shale oil in the reservoir. When the temperature reaches the autoignition point, the oil and gas in the reservoir begin to burn;

[0034] S2. Continuously inject oxidants to steadily advance the combustion front. The high-temperature gas generated during the combustion process forms a high-pressure drive in the reservoir, pushing the oil and gas flow to the production wells.

[0035] S3. Extract the oil and gas mixture through the production well, and recover the oil and gas after ground separation.

[0036] Preferably, the oxidant is air or oxygen.

[0037] The invention discloses an underground in-situ combustion method for low permeability oil reservoirs, oil shale and shale oil reservoirs based on chemical spontaneous ignition, which has the following beneficial effects:

[0038] (1) Chemical spontaneous ignition avoids the use of traditional external ignition equipment, simplifies the operation process, and is particularly suitable for the exploitation of low permeability, tight reservoirs and oil shale;

[0039] (2) Compared with the traditional external heating method, the equipment required by the present invention is simple, has strong adaptability, and can reduce mining costs;

[0040] (3) The high temperature generated by combustion can not only promote the pyrolysis of oil shale and release shale oil, but also improve the oil recovery efficiency by reducing the viscosity of crude oil and increasing fluidity. The gas generated by combustion further increases the oil recovery pressure and optimizes the oil recovery effect.

[0041] (4) In low permeability reservoirs, oil shales and shale reservoirs, the formation and expansion of fracture networks are crucial; the present invention optimizes the injection path of chemical reagents by combining fracturing technology, ensuring that the combustion process can cover a larger area and maximize the recovery rate;

[0042] (5) The present invention is applicable to complex reservoir environments such as low permeability reservoirs, oil shales and shale reservoirs, and can effectively cope with the challenges brought by reservoir heterogeneity. By flexibly adjusting the injection rate and ratio of chemical reagents, it can ensure stable combustion reactions in complex reservoirs.

[0043] (6) The CO2 and other gases generated during the combustion process can not only be used for oil recovery, but also be injected back into the oil reservoir to reduce CO2 emissions and achieve resource recycling. The present invention can also be combined with other secondary and tertiary oil recovery technologies (such as CO2 oil recovery technology) to further improve the recovery rate and reduce environmental impact.

[0044] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a temperature field distribution diagram of the chemical composition in Example 1 in a 1-meter one-dimensional combustion tube;

[0046] Figure 2 The temperature field distribution diagram of the chemical composition in Example 2 in a 1-meter one-dimensional combustion tube;

[0047] Figure 3 This is the temperature field distribution diagram of the chemical composition in Example 3 in a 1-meter one-dimensional combustion tube;

[0048] Figure 4 This is the temperature field distribution diagram of the chemical composition in Example 4 in a 1-meter one-dimensional combustion tube. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical scheme and advantages disclosed in the embodiments of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the embodiments of the present invention and are not intended to limit the embodiments of the present invention. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0050] Embodiment 1

[0051] A hydrogen peroxide and sodium nitrate ignition agent formula, wherein hydrogen peroxide (H2O2, 40%) is used as an ignition agent, sodium nitrate (NaNO3, 10%) is used as a combustion aid, Fe2O3 (5%) is used as a catalyst and polyethylene glycol (PEG, 3%) is used as an emulsifier. The chemical composition is shown in Table 1:

[0052] Table 1 List of formulas for preparing chemical compositions

[0053] ;

[0054] The addition of emulsifier PEG helps to improve the stability of the mixture and ensure the uniformity of the combustion front.

[0055] Using a one-dimensional fire drive combustion tube, add oil shale powder, pressurize it through a press, and then fractur it under high pressure to form cracks. The composition is injected into the target area of ​​the one-dimensional combustion tube through a high-pressure displacement pump. The air injection rate is 5L / min, and the production pressure is maintained at 8.0MPa. The test parameters are shown in Table 2:

[0056] Table 2 Test parameters

[0057] ;

[0058] The test results are shown in Table 3:

[0059] Table 3 Comparison of test results

[0060] ;

[0061] The test results show that the average temperature of the average combustion front is quite high, reaching 406°C, indicating that the fire drive can effectively maintain a high-temperature combustion front. The average combustion front speed is 0.39cm / min, indicating that the combustion process is relatively slow, which is a common phenomenon in shale oil with high thermal inertia.

[0062] like Figure 1As shown, it is the temperature field distribution diagram of the chemical composition in this embodiment in a 1-meter one-dimensional combustion tube. Among them, there are significant differences in the temperature peaks at different time points, and some temperature peaks exceed 400°C, especially in the curves of 240min and 360min. In the range of 0-40cm, the temperature changes relatively stably with time, indicating that this area is the main heat source area of ​​the combustion front. At 100cm, the temperature began to drop significantly after 420min, indicating that the advancement of the combustion front has reached its limit.

[0063] This shows that the chemical composition in this embodiment can effectively improve the self-ignition efficiency of H2O2, produce a continuous combustion effect, and successfully simulate the fire drive process of shale oil under high pressure and high temperature conditions. From the test results, the combustion front can maintain a high temperature, and the injection of oxidant (air) also maintains the combustion process. Although the oxygen rate is low, indicating that the combustion speed is slow, the fire drive is successful overall, with good temperature distribution and combustion effect.

[0064] Embodiment 2

[0065] A combined ignition agent formula of sodium peroxide and potassium permanganate, wherein sodium peroxide (Na2O2, 30%) and potassium permanganate (KMnO4, 15%) are added as a combined ignition agent, ammonium nitrate (NH4NO3, 10%) is added as a combustion aid, CuO (3%) is used as a catalyst, and sodium dodecyl sulfate (2%) is used as an emulsifier, as shown in Table 4:

[0066] Table 4 List of formulas for preparing chemical compositions

[0067] ;

[0068] Using a one-dimensional fire drive combustion tube, add oil shale powder, pressurize it through a press, and then fracturize it under high pressure to form cracks. The composition is injected into the target area of ​​the one-dimensional combustion tube through a high-pressure displacement pump. The air injection rate is 5L / min, and the production pressure is maintained at 8.0MPa. The test parameters are shown in Table 5:

[0069] Table 5 Test parameters

[0070] ;

[0071] The test results are shown in Table 6:

[0072] Table 6 Comparison of test results

[0073] ;

[0074] The test results show that the temperature at the combustion front is relatively high, reaching 472°C, indicating that the fire drive process at the combustion front is relatively intense. The oxygen rate before combustion (0.31 cm / min) is slightly lower than that in Example 1, indicating that the combustion process in this test is relatively slower. The high H / C atomic ratio (2.63) indicates that the shale oil has a high oil production potential, and the combustion process is relatively complete, generating more heat.

[0075] like Figure 2 As shown, it is the temperature field distribution diagram of the chemical composition in this embodiment in a 1-meter one-dimensional combustion tube.

[0076] The results show that within 60 minutes, the temperature of the combustion front is low and the initial temperature rise is not obvious, but as time goes by, the temperature of the combustion front increases significantly. After 240 minutes, the temperature at a distance of 40 cm rises rapidly to about 500 ° C, indicating that the advancement speed of the combustion front is significantly accelerated at this time. As the combustion front gradually advances to 1m from the one-dimensional fire drive combustion tube, the temperature peak gradually decreases, indicating that the combustion front begins to weaken.

[0077] At a reservoir temperature of 95°C, sodium peroxide and potassium permanganate decompose to produce oxygen, which triggers a spontaneous combustion reaction under high temperature conditions. Ammonium nitrate further provides oxidant support, and CuO accelerates the chemical reaction, continuously raising the formation temperature. Sodium dodecyl sulfate acts as an emulsifier to improve the fluidity within the oil layer.

[0078] The combined ignition agent formula of hydrogen peroxide and potassium permanganate in this embodiment can effectively initiate and maintain the combustion of shale oil through the combination of oxidant and combustion aid. The addition of catalyst CuO helps to increase the reaction rate and ensure the efficient combustion process.

[0079] The combined ignition agent formula can effectively improve the combustion efficiency of shale oil. The high temperature distribution and high combustion front temperature (472°C) in the test indicate that the advancement of the combustion front is relatively ideal. Although the oxygen rate is slightly lower, it can still maintain the advancement of the combustion front. The higher H / C atomic ratio (2.63) shows that shale oil contains a higher hydrogen content, which helps to generate more heat and energy during combustion.

[0080] Compared with the first embodiment, the second embodiment optimizes the combination of the ignition agent, potassium permanganate and the catalyst, so that the reaction speed is accelerated and the spontaneous combustion effect is significant, and the embodiment is suitable for medium and high temperature oil reservoirs.

[0081] Embodiment 3

[0082] A potassium permanganate and diethyl zinc ignition flooding system, wherein potassium permanganate (KMnO4, 20%) is used as an ignition agent, diethyl zinc (DEZ, 10%) is used as a fuel additive, potassium nitrate (KNO3, 8%) is used as a combustion aid, NiO (4%) is used as a catalyst, and Tween80 (2%) is used as an emulsifier. The composition formula is shown in Table 7:

[0083] Table 7 List of formulas for preparing chemical compositions

[0084] ;

[0085] Using a one-dimensional combustion tube model, a fire drive test was conducted by injecting air at a high pressure. This setting simulates the actual way of shale oil extraction, using oxygen in the air to maintain the combustion front, and the initial temperature and pressure provide ideal conditions for combustion. The test parameters are shown in Table 8:

[0086] Table 8 Test parameters

[0087] ;

[0088] The test results are shown in Table 9:

[0089] Table 9 Comparison of test results

[0090] ;

[0091] The test data showed that the temperature of the combustion front reached 406°C, indicating that the combustion reaction in the fire drive test was stable. The oxygen rate was 0.39 cm / min, indicating that the combustion process was relatively slow, but the continuous high temperature could maintain the effective advancement of the combustion front. The H / C atomic ratio was 2.48, indicating that the shale oil had a high hydrogen-carbon ratio and had good oil production potential.

[0092] like Figure 3 The figure shows the temperature field distribution diagram of the chemical composition in this embodiment in a 1-meter one-dimensional combustion tube. It shows the temperature change of the combustion front with distance at different time points: the temperature of the combustion front is relatively low at 60 minutes, and the temperature gradually increases as time goes by.

[0093] The peak temperature of the 240-min and 360-min curves is close to 450°C, indicating that the combustion is most intense during this period and the advancement speed of the combustion front is also accelerating. The combustion front gradually weakens at a distance of 1m in the one-dimensional combustion tube, indicating that the heat gradually decays with increasing distance during the fire drive process.

[0094] The test data showed that the combustion temperature could be maintained above 400°C with the ignition agent combination of potassium permanganate and diethyl zinc, the average pre-combustion oxygen rate was moderate, and the combustion process was relatively continuous and stable. The higher H / C ratio further proved that shale oil has good combustion and oil production potential.

[0095] The chemical composition is injected into the sand-filled model tube, and air is continuously injected. Potassium permanganate and diethyl zinc undergo a redox reaction, releasing a large amount of heat and inducing a spontaneous combustion effect. Potassium nitrate acts as a combustion aid to promote the combustion reaction, and NiO acts as a catalyst to accelerate the reaction rate. Tween 80 acts as an emulsifier to reduce interfacial tension and improve the fluidity of crude oil.

[0096] Effect: Through the synergistic effect of potassium permanganate and diethyl zinc, the ignition agent formula and conditions in Example 3 can effectively maintain the high temperature and advancement speed of the combustion front, and the fire drive process is stable. The temperature distribution curve shows that the advancement of the combustion front is relatively uniform and the combustion reaction is relatively ideal.

[0097] Embodiment 4

[0098] An ignition combination of hydrogen peroxide and triethylaluminum, wherein hydrogen peroxide (H2O2, 35%) is used as an ignition agent, triethylaluminum (TEA, 15%) is used as a fuel additive, potassium nitrate (KNO3, 8%) is used as a combustion aid, CrO2 (3%) is used as a catalyst and polyoxyethylene alkylphenol ether (3%) is used as an emulsifier, and the chemical composition formula is shown in Table 10:

[0099] Table 10 List of formulas for preparing chemical compositions

[0100] ;

[0101] Using a one-dimensional combustion tube model, a fire drive test was conducted at a lower pressure (4.0 MPa) and a higher initial temperature (80 ° C) by injecting air. At this test pressure and initial temperature, it is helpful to improve the efficiency of the combustion reaction, especially for heavy oil types. These conditions are conducive to combustion and oil movement. The test parameters are shown in Table 11:

[0102] Table 11 Test parameters

[0103] ;

[0104] The test results are shown in Table 12:

[0105] Table 12 Comparison of test results

[0106] ;

[0107] The test data showed that the temperature of the combustion front was as high as 512°C, indicating that the combustion reaction was relatively violent. The oxygen rate of 0.35 cm / min indicated that the combustion front was advancing slowly, but it was able to maintain stable combustion. The higher pre-combustion temperature (512°C) means that a large amount of heat is released during the combustion process, which has a better extraction effect on heavy oil. The H / C atomic ratio is 2.43, indicating that the oil has a good hydrogen-carbon ratio and good oil production potential.

[0108] like Figure 4 As shown, it is a temperature field distribution diagram of the chemical composition in this embodiment in a 1-meter one-dimensional combustion tube, which shows the temperature change of the combustion front with distance at different time points: at 60 minutes, the temperature of the combustion front is low, but rises rapidly and reaches a peak at a distance of 40 cm.

[0109] At 180 minutes, the temperature reached over 600°C, which was the highest point of the combustion front in the test, indicating that the combustion was most intense at this moment. The combustion front gradually weakened after 300 minutes, but still maintained a high temperature at 540 minutes.

[0110] When the reservoir temperature is 110°C, hydrogen peroxide decomposes rapidly, and triethylaluminum reacts with the released oxygen to produce a strong exothermic reaction. Potassium nitrate, as a combustion aid, enhances the combustion reaction, and CrO2 provides a catalytic effect to accelerate the ignition process. The emulsifier enables the chemical reagent and crude oil to form a stable emulsified system, improves the fluidity of the crude oil, significantly enhances the oil displacement effect, and increases the recovery rate by 30%.

[0111] Effect: The chemical composition in this embodiment utilizes the strong oxidation and combustion properties of hydrogen peroxide and triethylaluminum to effectively ignite the combustion process of heavy oil. The addition of potassium nitrate ensures the continuous advancement of the combustion front, and chromium dioxide, as a catalyst, improves the efficiency of the combustion reaction. The ignition agent combination using hydrogen peroxide and triethylaluminum showed a high combustion temperature (over 500°C) in the fire drive test, indicating that the combustion front is relatively strong and steadily advancing. Although the oxygen rate before combustion is slightly slow, the high temperature ensures the continuity and depth of combustion. The combination of hydrogen peroxide and triethylaluminum effectively accelerates the spontaneous combustion reaction, is suitable for heavy oil reservoirs, and has excellent oil recovery effects.

[0112] Embodiment 5

[0113] An ignition agent formula of a combination of sodium peroxide and an organic peroxide, wherein sodium peroxide (Na2O2, 25%) is used as a main ignition agent, benzoyl peroxide (BPO, 10%) is used as an organic peroxide, nitric acid (NH4NO3, 12%) is used as a combustion aid, Fe3O4 (4%) is used as a catalyst, and Span 80 (2%) is used as a non-ionic emulsifier.

[0114] Table 13 List of formulas for preparing chemical compositions

[0115] ;

[0116] The ignition agent system is injected into a shale oil reservoir at a depth of 2,500 meters through a dedicated injection well, and the reservoir temperature is 140°C.

[0117] The core of this composition is to achieve effective ignition through the combined action of inorganic (sodium peroxide) and organic peroxide (benzoyl peroxide). Sodium peroxide and benzoyl peroxide decompose rapidly at a reservoir temperature of 140°C, releasing oxygen and free radicals, and producing a spontaneous combustion reaction. Ammonium nitrate acts as a combustion aid to further promote the combustion process, and Fe3O4 accelerates the reaction, significantly increasing the formation temperature.

[0118] Sodium peroxide provides a strong oxidizing environment to start the reaction quickly, while organic peroxides help maintain the advancement of the combustion front. Ammonium nitrate, as a combustion aid, further enhances the combustion reaction and ensures that the combustion process can be sustained under mine conditions. The catalyst Fe3O4 increases the overall reaction rate, making the fire flooding effect more significant.

[0119] The non-ionic emulsifier Span 80 optimizes the interaction between chemical reagents and crude oil, reduces interfacial tension, and increases crude oil recovery by approximately 22%.

[0120] Embodiment 6

[0121] A hydrogen peroxide and tung oil ignition flooding combination, wherein hydrogen peroxide (H2O2, 30%) is used as an ignition agent, tung oil (Tung Oil, 20%) is used as a fuel additive, sodium nitrate (NaNO3, 10%) is used as a combustion aid, MnO2 (3%) is used as a catalyst, and sodium dodecylbenzene sulfonate (SDBS, 2%) is used as an emulsifier. The composition formula is shown in Table 14:

[0122] Table 14 List of formulas for preparing chemical compositions

[0123] ;

[0124] The ignition system is injected into a shale oil reservoir at a depth of 3,500 meters through a special injection well, and the reservoir temperature is 160°C. It is injected into the target layer in a certain oil reservoir through a water injection well, and undergoes a spontaneous combustion reaction in the formation.

[0125] In field tests, this ignition agent combination can show good combustion performance:

[0126] (1) Rapid ignition: The action of hydrogen peroxide and the catalyst enables the ignition reaction to start quickly. Under mining conditions, hydrogen peroxide, as a strong oxidant, quickly releases oxygen, starting the combustion process.

[0127] (2) High temperature combustion. Tung oil, as a fuel additive, generates high heat when burned, which helps to increase the temperature of the combustion front. It is especially suitable for combustion in mines where high temperature is required to promote the flow of crude oil in the oil layer.

[0128] (3) The combustion front advances stably. Sodium nitrate acts as a combustion aid to ensure that the combustion front advances stably and will not be extinguished midway due to lack of oxygen during combustion. At the same time, the catalytic effect of manganese dioxide improves the combustion efficiency, making the front advance relatively fast.

[0129] (4) Uniform distribution: The emulsification effect of SDBS ensures that the various components of the ignition agent are evenly distributed in the oil layer, avoiding the phenomenon of local combustion being too fast or too slow.

[0130] When the reservoir temperature is 160℃, hydrogen peroxide decomposes to release oxygen. Tung oil as a fuel additive reacts with oxygen to generate strong heat. Sodium nitrate further enhances the combustion reaction. MnO2 as a catalyst improves the reaction efficiency. SDBS as an emulsifier reduces the interfacial tension of the liquid in the reservoir, promotes the fluidity of crude oil, and increases the recovery rate by 28%.

[0131] Effect: The combination of the ignition agent, the combustion aid and the catalyst in this embodiment effectively accelerates the spontaneous combustion reaction, is particularly suitable for medium and deep oil reservoirs, and improves the crude oil recovery rate.

[0132] The present invention can quickly induce a spontaneous combustion reaction in an oil reservoir and maintain a stable high-temperature combustion process through an optimized combination of an ignition agent, an combustion aid, a catalyst, an emulsifier and a fuel additive. The method is suitable for the exploitation of low-permeability oil reservoirs, oil shales, shale oil reservoirs and sandstone oil reservoirs, and can significantly improve the recovery rate. It is particularly suitable for complex oil reservoir conditions where conventional oil recovery technologies are difficult to effectively apply.

[0133] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for underground in-situ combustion of low permeability oil reservoirs, oil shales and shale oil reservoirs based on chemical spontaneous ignition, characterized in that: The method is achieved by injecting a chemical spontaneous ignition composition and an oxidant into the oil reservoir, wherein the chemical spontaneous ignition composition comprises, by mass percentage, 20%-45% ignition agent, 10%-20% fuel additive, 8%-12% combustion improver, 3%-5% catalyst, 2%-3% emulsifier, and the balance is water; the oxidant is air or oxygen; The ignition agent is one or a combination of hydrogen peroxide, sodium peroxide, potassium permanganate; The fuel additive includes one of triethylaluminum, diethylzinc, benzoyl peroxide, and tung oil; The combustion aid includes one of potassium nitrate, sodium nitrate and ammonium nitrate; The catalyst includes one of Fe2O3, CuO, Fe3O4, MnO2, NiO, and CrO2; The emulsifier includes one of sodium dodecyl sulfate, sodium alkylbenzene sulfonate, polyethylene glycol, Tween series, and alkylphenol polyoxyethylene ether.

2. The underground in-situ combustion method of low permeability oil reservoirs, oil shales and shale oil reservoirs based on chemical spontaneous ignition according to claim 1, characterized in that: The injection method of the chemical spontaneous ignition composition includes a staged injection method and a co-injection method; When the reservoir structure is heterogeneous, layered or fractured, the staged injection method is used to inject the oxidant and catalyst into the reservoir first, and then inject the ignition agent, combustion aid and emulsifier at different depths and positions by staged injection, and finally inject the fuel additive; When the reservoir structure is uniform and dense, the co-injection method is used, and the chemical spontaneous ignition composition is premixed according to the formula and then injected through the injection well at one time.

3. The underground in-situ combustion method for low permeability oil reservoirs, oil shales and shale oil reservoirs based on chemical spontaneous ignition according to claim 1, characterized in that: The process of extracting oil and gas resources after injecting the chemical spontaneous ignition composition into the oil reservoir includes: S1. After the chemical spontaneous ignition composition is injected into the oil reservoir, it spontaneously ignites. The heat released by the spontaneous ignition heats the crude oil or shale oil in the reservoir. When the temperature reaches the autoignition point, the oil and gas in the reservoir begin to burn; S2. Continuously inject oxidants to steadily advance the combustion front. The high-temperature gas generated during the combustion process forms a high-pressure drive in the reservoir, pushing the oil and gas flow to the production wells. S3. Extract the oil and gas mixture through the production well, and recover the oil and gas after ground separation.

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