A fire drive extinguishing well re-ignition process

Abstract

The application discloses a fire-fighting well repeated ignition process in fire-flooding, and belongs to the field of heavy oil fire-flooding exploitation. For the well group in which the formation is extinguished in the fire-flooding process, the combustion radius is determined, the safety risk of the well bore is evaluated, the liquid safety isolation measure is taken, the well is shut in after high-temperature steam is injected, then the well is opened for mining, the high-temperature steam is used to break the blockage of the low-temperature oxidized coking matter to the formation, the crude oil in the deep part of the formation is backflowed to the well bore to improve the crude oil saturation near the well bore, sufficient fuel is provided for the repeated ignition, the formation is heated to accelerate the reaction rate of the oxygen remaining in the burned area and the backflowed crude oil, and the oxygen is depleted to provide a safe operation environment for the repeated ignition. In the ignition process, the deposition amount of the high-temperature pyrolytic coke in the crude oil is increased by means of rapid heating and increasing the ignition temperature, sufficient fuel is provided for the near-wellbore zone, and the final ignition success rate is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of heavy oil fire flooding exploitation, and relates to a repeated ignition process for fire flooding extinguishing well. BACKGROUND

[0002] Fire flooding is a heavy oil thermal recovery technology by continuously injecting air and igniting the oil layer, burning 10% of the heavy components that are difficult to be recovered, generating high-temperature modification, combustion flue gas and water vapor multiple displacement effect, and has the characteristics of high thermal efficiency, high recovery efficiency, energy saving and environmental protection. The key to the successful implementation is to achieve high-temperature ignition and continuous and stable combustion in the oil layer. However, during the implementation in the mine field, due to the differences in oil layer properties, as well as problems in technology, equipment, management and other aspects, part of the successful ignition wells appear formation fire extinguishing after turning into normal production, which is specifically manifested as that the pressure of the gas injection well continuously increases, the gas injection speed decreases, the oil production of the production well rapidly decreases, and high-concentration oxygen and combustible gas are continuously produced, which exists explosion risk hidden danger, and the fire flooding production process is forced to terminate. At this time, repeated ignition measures need to be taken to restore the high-temperature combustion state of the formation, so that the fire flooding exploitation process can continue.

[0003] The paper "Main Controlling Factors and Ignition Strategies for Secondary Ignition in Heavy Oil Fire Flooding" (Journal of Shenyang University of Technology, January 2017) discloses a strategy for secondary ignition in fire-extinguishing wells. Based on the combustion radius and crude oil saturation near the wellbore, three methods are adopted: direct resumption of gas injection, crude oil injection to increase saturation in the near-wellbore zone before ignition, and ignition at a different wellbore. However, these strategies are not considered, such as the formation blockage caused by dense coke formed by low-temperature oxidation near the combustion zone after extinguishing the fire, the inability of air to penetrate the blocked area after resuming gas injection, and the air cavity formed in the burned zone (overfire zone) between the gas injection well and the combustion front, which can mix with light hydrocarbons and flow back into the wellbore, leading to explosions. Therefore, this strategy is not practical. Regarding the characteristics of dense coke, the paper "Analysis and Solutions for Soft Stuck in Gravity Fire Flooding" (Science, Technology and Engineering, December 2016) studied its causes and measures to prevent soft stuck during production, but did not provide a solution for unblocking the blockage after fire extinguishing. Regarding the lower limit of fire flooding ignition saturation, the paper "Displacement Characteristics and Well Pattern Selection of Vertical Well Fire Flooding in Old Heavy Oil Areas" (Acta Petrolei Sinica, August 2017) determined a lower limit of ignition of residual oil saturation greater than 25% based on indoor simulation experiments. However, it did not provide a method for improving the ignition success rate under low oil saturation conditions. In terms of the reaction characteristics of crude oil and oxygen, the document "Characteristics and Development Methods of Crude Oil Oxidation Reaction in the Full Temperature Range of Air Injection" (Petroleum Exploration and Development, 2020.04) clarified based on indoor research results that heavy oil can achieve medium-temperature and high-temperature oxidation in the two ranges of 200-400°C and 400-600°C, and there are two exothermic peaks. It also recommends that heavy oil with lower viscosity can be driven by medium-temperature fire by chemical ignition, and high-viscosity oil requires electric ignition to achieve high-temperature fire drive above 450°C, but does not provide a method for safely consuming oxygen in a high-temperature environment; Regarding the determination of the explosion limit of the fire drive mixture, foreign literature has measures to shut down the well when the oxygen concentration is greater than 5%, but there is no method for determining the critical explosion limit under mixed gas conditions such as methane, carbon monoxide, combustion flue gas, and air.

[0004] In summary, we continue to develop a practical, safe and efficient fire-driven fire-fighting well repeated ignition process technology. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art, that is, the repeated ignition of a fire-driven fire-extinguishing well is poor in practical operability and low in safety, and to provide a repeated ignition process for a fire-driven fire-extinguishing well.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A fire-driven fire-extinguishing well repeated ignition process comprises the following steps:

[0008] Step 1) obtaining the combustion radius of the fire extinguishing well group;

[0009] Step 2) Obtaining gas sampling results, injecting high-temperature steam based on the oxygen and methane concentrations in the mixed gas in the wellbore, and then soaking the well;

[0010] Step 3) Assess the wellbore safety risk and, based on the analysis of wellhead gas sampling results after the well is shut down, decide whether to continue injecting high-temperature steam or open the well for production;

[0011] Step 4) analyzing the oil saturation of the near-wellbore area, determining repeated ignition process parameters based on the oil saturation, and performing repeated ignition operations based on the repeated ignition process parameters.

[0012] Preferably, in step 1), the calculation process of the combustion radius of the fire extinguishing well group is:

[0013]

[0014] Where R is the combustion radius of the fire extinguishing well group, V a is the total amount of air injected, C is the amount of air consumed per unit of crude oil combustion, S o is the oil saturation, is the porosity of the oil layer, and h is the effective thickness of the oil layer.

[0015] Preferably, in step 1), after obtaining the combustion radius of the fire extinguishing well group, the method further includes:

[0016] when When , directly go to step 4) and repeat the ignition operation;

[0017] when When , go to step 2);

[0018] When R≥30m, the well group cannot be re-ignited, and the adjacent high oil saturation well group should be re-selected for re-ignition.

[0019] Among them, R is the combustion radius of the fire extinguishing well group, in meters; h is the effective thickness of the oil layer, in meters.

[0020] Preferably, the process of injecting high-temperature steam in step 2) is:

[0021] Get gas sampling results,

[0022] If the oxygen concentration in the mixed gas in the wellbore is greater than 8% and the methane concentration is greater than 5%, the wellbore should be flushed and pressurized with a well-flushing fluid. After the wellbore is filled with the well-flushing fluid, clean water twice the volume of the wellbore should be injected into the formation, followed by high-temperature steam.

[0023] If the oxygen concentration in the mixed gas in the wellbore is ≤5%, high-temperature steam is directly injected into the wellbore.

[0024] Preferably, in step 2), the volume of the injected high-temperature steam is:

[0025]

[0026] Where V is the volume of high-temperature steam injected, V a is the total amount of air injected, C is the amount of air consumed per unit of crude oil combustion, S o is the oil saturation, is the porosity of the oil layer.

[0027] Preferably, the process of injecting high temperature steam is:

[0028] First, inject 1 / 4V to 1 / 3V volume of high-temperature steam, then hold the well for 5-10 days, then open the well for production. According to step 4), determine whether the saturation meets the repeated ignition conditions. If not, repeat this step and inject the remaining volume of high-temperature steam.

[0029] Preferably, the temperature of the high-temperature steam is above 200°C.

[0030] Preferably, in step 3), the specific process of assessing wellbore safety risk is:

[0031] Analyze based on wellhead gas sampling results;

[0032] When the oxygen concentration in the mixed gas in the wellbore is ≥5%, return to step 2) and continue to inject high-temperature steam and soak the well until the oxygen concentration in the mixed gas in the wellbore is <5%;

[0033] When the oxygen concentration in the mixed gas in the wellbore is less than 5%, the well is opened for production.

[0034] Preferably, in step 4), the oil saturation of the area near the wellbore is analyzed, and when the oil saturation is greater than 25%, a rapid temperature rise ignition process is adopted;

[0035] In the rapid temperature rise ignition process, the temperature rise rate is 8-10°C / min, the ignition temperature is greater than 450°C, and the igniter outlet is set in the lower middle part of the oil layer.

[0036] Preferably, during the repeated ignition operation in step 4), the combustion dynamics of the ignition process and the composition of the gas produced by the surrounding production wells are calculated to determine whether the repeated ignition is successful;

[0037] When the effective heating radius around the wellbore is greater than 450℃ and exceeds 0.5m, and the oxygen concentration in the mixed gas of the surrounding production wells is less than 1%, the carbon dioxide concentration is greater than 9%, and the nitrogen concentration is greater than 70%, the repeated ignition is successful, otherwise the repeated ignition fails.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The present invention aims to provide a repeated ignition process technology for fire-driven fire-extinguishing wells. For well groups that experience formation extinguishing during fire-driven ...

[0040] Furthermore, due to the overlap of the fire line, the fire cavity expands outward in the shape of an inverted cone in the longitudinal direction starting from the ignition well. The fire drive ignition process is to form a stable high-temperature area above the ignition point of crude oil around the wellbore through artificial heating (electric heating, chemical heating agent, burner) (during the heating process, there is a evaporation phase change of oil and water. Before the ignition temperature is reached, a large amount of crude oil and water have been vaporized and flowed, and only a small amount of heavy components with poor fluidity are left to serve as fuel. Therefore, there is a fuel shortage problem in the low-saturation oil layer. When the injected compressed air flows through this area, it undergoes a high-temperature oxidation reaction (i.e., combustion) with the heavy components of crude oil retained on the surface of the rock particles. When a stable high-temperature oxidation zone is formed, it indicates that the ignition is successful. The so-called high-temperature combustion of the oil layer is the oxidation reaction of the coke converted from oxygen and heavy components in the porous structure, which is similar to the smoldering state of a cigarette butt.

[0041] Furthermore, considering the special air injection production process of fire drive, there are conditions where light hydrocarbons and oxygen coexist in the wellbore during the process switching of steam injection and other production links, which poses an explosion risk. It is necessary to take necessary safety measures. The specific approach is to assess the risk of the wellbore according to the explosion limit evaluation standard, and adopt low-temperature liquid isolation measures to avoid contact between high-temperature fluid and mixed gases with explosion risks in the wellbore (the wellbore can be regarded as a pressure vessel of a certain volume, and there is a possibility of flash explosion of the mixed gas, while the formation has a porous structure, the flame propagation speed in it is slow, and there is no gas explosion phenomenon), so as to ensure the safety and controllability of the operation process.

[0042] Furthermore, laboratory experiments have shown that optimizing ignition parameters for low-saturation reservoirs increases coke deposition by increasing the heating rate. Successful ignition is impossible below 25% oil saturation, while a heating rate greater than 8°C / min is required for successful ignition at 25% oil saturation. Based on this understanding, repeated ignitions require first determining the oil saturation near the wellbore. Considering that existing ignition processes typically utilize electric heaters, excessive heating rates and ignition temperatures can lead to excessive heat load on the igniter surface, potentially damaging the equipment. Therefore, the heating rate is controlled between 8 and 10°C / min and the ignition temperature is 450°C. Given the higher oil saturation in the lower reservoir, the igniter and ignition string should be lowered into the lower-middle portion of the reservoir to ensure the initial high-temperature ignition occurs there. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is the oxygen consumption rate diagram of heavy oil oxidation reaction in different temperature ranges;

[0044] Figure 2 Flow chart of the repeated ignition process for fire-fighting wells. DETAILED DESCRIPTION

[0045] The present invention is described in further detail below with reference to the accompanying drawings:

[0046] Example 1

[0047] A fire-driven fire-extinguishing well repeated ignition process comprises the following steps:

[0048] Step 1) obtaining the combustion radius of the fire extinguishing well group;

[0049] when When , directly go to step 4) and repeat the ignition operation;

[0050] when When , go to step 2);

[0051] When R≥30m, the well group cannot be re-ignited, and the fire extinguishing well group should be re-selected for re-ignition.

[0052] Among them, R is the combustion radius of the fire extinguishing well group, in meters; h is the effective thickness of the oil layer, in meters.

[0053] Step 2) Obtain gas sampling results and inject high-temperature steam based on the oxygen and methane concentrations in the mixed gas in the wellbore.

[0054] If the oxygen concentration in the mixed gas in the wellbore is greater than 8% and the methane concentration is greater than 5%, the wellbore should be flushed and pressurized with a well-flushing fluid. After the wellbore is filled with the well-flushing fluid, clean water twice the volume of the wellbore should be injected into the formation, followed by high-temperature steam.

[0055] If the oxygen concentration in the mixed gas in the wellbore is ≤5%, high-temperature steam is directly injected into the wellbore.

[0056] Then stew the well;

[0057] Step 3) Assess the wellbore safety risk and, based on the analysis of wellhead gas sampling results after the well is shut down, decide whether to continue injecting high-temperature steam or open the well for production;

[0058] When the oxygen concentration in the mixed gas in the wellbore is ≥5%, return to step 2) and continue to inject high-temperature steam and soak the well until the oxygen concentration in the mixed gas in the wellbore is <5%;

[0059] When the oxygen concentration in the mixed gas in the wellbore is less than 5%, the well is opened for production.

[0060] Step 4) analyzing the oil saturation of the near-wellbore area, determining repeated ignition process parameters based on the oil saturation, and performing repeated ignition operations based on the repeated ignition process parameters.

[0061] Example 2

[0062] A fire-driven fire-extinguishing well repeated ignition process, such as Figure 2 As shown, the following steps are included:

[0063] 1. Determine the combustion radius of the fire extinguishing well group and analyze the oil saturation in the area near the wellbore.

[0064] Using the formula The combustion radius R of the fire extinguishing well group can be calculated, where: V a is the total amount of air injected, in m 3 , C is the air consumption per unit crude oil combustion, unit is m 3 / m 3 , S o is the oil saturation, %, is the oil layer porosity, %, and h is the effective thickness of the oil layer, in meters. Usually, due to the overlapping of the fire line, the fire cavity morphology expands outward in the vertical direction from the ignition well in the form of an inverted cone (table).

[0065] (1) If the combustion radius h is the effective oil layer thickness. If there is still unused crude oil with high saturation in the lower part of the oil layer near the wellbore, then repeated ignition operation can be carried out directly according to step 5).

[0066] (2) If the combustion radius Then proceed to step 2) inject steam to perform huff and puff, soak the well, and recover the oil, so that the crude oil flows back into the wellbore and then repeat the ignition operation.

[0067] (3) If the combustion radius R ≥ 30 m, the heat loss of the injected steam is too large to effectively heat the low-temperature oxidation area. At this time, it can be determined that the well group cannot be repeatedly ignited, and the ignition well should be replaced to carry out ignition operations in the high-crude oil saturation area.

[0068] 2. Assess wellbore safety risks.

[0069] Gas sampling analysis indicates that if the oxygen concentration in the wellbore gas mixture exceeds 8% and the methane concentration exceeds 5%, direct injection of high-temperature steam poses an explosion risk. Therefore, the wellbore must first be flushed and killed with a circulating well-flushing fluid. Once the wellbore is filled with the fluid, clean water (twice the wellbore volume) is injected into the formation before high-temperature steam is injected. This creates a barrier between the hazardous gases and the high-temperature steam, preventing a flashover. If the oxygen concentration in the wellbore gas mixture is ≤5%, steam injection proceeds directly.

[0070] 3. Inject a certain amount of high-temperature steam to simmer the well.

[0071] According to the formula The volume of the combustion space, V a is the total amount of air injected, in m 3 , C is the air consumption per unit crude oil combustion, unit is m 3 / m 3 ,S o is the oil saturation, %, is the porosity of the oil layer, %. Based on the heat transfer and seepage characteristics of steam in porous media, and considering economic factors, 1 / 4 to 1 / 3V volume of high-temperature steam above 200°C is first injected, and then the well is shut down for 5-10 days. There are three purposes. The first is the results of the literature. After the low-temperature oxidation reaction of crude oil and oxygen, dense and viscous coke will be generated. The large amount of coke accumulated in the formation will cause the gas injection channel to be blocked, and the injection pressure will gradually increase, and the air cannot be injected. This type of coke cannot melt at less than 100°C, begins to soften at 150°C, and has fluidity above 200°C. Therefore, the injected high-temperature and high-pressure steam can melt the low-temperature coke and restore the connectivity of the formation; the second is based on the reaction rate of crude oil with oxygen in different temperature ranges (such as Figure 1 As shown in Figure 2, there are two peaks in crude oil oxygen consumption: between 200-300°C and above 450°C. Therefore, injecting high-temperature steam and then soaking the well for a period of time can accelerate the reaction between oxygen in the air cavity and the crude oil, depleting the oxygen in the formation and avoiding the risk of explosion in the wellbore during recovery. Thirdly, by heating the formation, crude oil in areas not affected by the fire flooding is heated and flows back into the wellbore, increasing the oil saturation near the wellbore and providing the necessary fuel for repeated ignition.

[0072] 4. Assess the safety risk of the wellbore and conduct mining.

[0073] After the well is soaked, according to the analysis of the wellhead gas sampling results, if the oxygen concentration in the mixed gas in the wellbore is ≥5%, the steam injection and soaking are repeated according to step 3 until the oxygen concentration in the mixed gas in the wellbore is less than 5%. The well is opened for recovery, and the crude oil flows back into the wellbore, which increases the crude oil saturation near the wellbore and provides fuel for re-ignition.

[0074] 5. Analyze the oil saturation in the near-wellbore area and determine the repeated ignition process parameters.

[0075] If the minimum water content in the recovered fluid reaches below 75%, then based on literature results, it can be determined that the oil saturation in the near-wellbore zone is above 25%, meeting the lower ignition limit. Considering that the returned crude oil has a lower viscosity and lower heavy component content compared to the original formation crude oil, this means that less components can be deposited to form solid coke, which is the primary fuel for fire flooding ignition and combustion. Therefore, to increase the amount of fuel deposited during the ignition process, a rapid heating ignition process is required. Based on laboratory experiments and field experience, this invention requires a heating rate of 8-10°C / min. Furthermore, since the recovery process carries a large amount of combustion fumes, density differences occur during the flow process, which can cause gravitational separation, with gas accumulating in the upper part of the oil layer and oil and water accumulating in the lower and middle parts of the layer. Therefore, the ignition string should be lowered to the bottom of the oil layer to ensure that the initial ignition point and high-temperature area are concentrated in the lower and middle parts of the oil layer to improve the ignition success rate.

[0076] 6. Carry out repeated ignition operations to determine whether the formation has successfully reignited.

[0077] After recovery is complete, the ignition string is lowered to the bottom of the reservoir and ignition is performed in accordance with the China National Petroleum Corporation standard "Technical Specification for Ignition of Heavy Oil Fire Drive" (Q / SY 01868-2020). During the ignition process, the heating rate must meet 8-10°C / min and the ignition temperature must be greater than 450°C. Five to seven days after ignition, a comprehensive assessment is made based on the combustion dynamics monitoring software during the ignition process and the composition of the gas produced from surrounding production wells. If the software calculates that the effective heating radius around the wellbore greater than 450°C exceeds 0.5m, and the oxygen concentration in the produced gas from surrounding production wells is less than 1%, the carbon dioxide concentration is greater than 9%, and the nitrogen concentration is greater than 70%, then the repeated ignition is considered successful, the formation has returned to a high-temperature combustion state, and the fire drive oil production process can be restarted.

[0078] Example 3

[0079] In a heavy oil reservoir, the average porosity is 25.4%, the permeability is 1000mD, the viscosity of the degassed crude oil at 50℃ is 800mPa·s, and the density of the crude oil is 0.94g / cm 3 , oil saturation 67%, effective oil layer thickness 8m. A certain ignition well continuously injected 890000m 3After that, the gas was stopped for one week due to a compressor failure. After the gas injection was resumed, the pressure increased from 2.2MPa to 7MPa, and the daily gas injection volume increased from 10000m 3 Dropped to less than 1000m 3 The oxygen concentration in the gas produced by the production well was 8% and no liquid was produced, so the well was forced to shut down and stop production. According to laboratory data, the reservoir consumes 11.5m3 of air per kilogram of crude oil. 3 The maximum consumption of crude oil during combustion is 15%. According to the formula, the average combustion radius is 12.2m. The sampling results of the gas injection well are: oxygen 15%, methane 5%, and there is a risk of explosion. After the well is killed by circulating the well washing fluid, clean water is injected into the formation for 50m 3 , and then inject high-temperature steam into the formation for 800m 3 After seven days of shut-in, gas samples were taken from the wellhead, revealing 0.5% oxygen and 12% methane. The wellbore was in a safe state. The well was opened for drainage, and the minimum water cut was measured at 65%, meeting the conditions for repeated ignition. Ignition parameters were set at a heating rate of 10°C / min and an ignition temperature of 480°C. The ignition string was deepened to the reservoir bottom, and after well flushing and test injection, the ignition process was initiated. Seven days after ignition, the heating radius was calculated to be 0.56m. Gas measurements from surrounding production wells showed 0% oxygen, 11% carbon dioxide, and 76% nitrogen. The well was deemed successfully repeated, and normal fireflooding production was resumed.

[0080] In terms of the development of the fire line, since air is less dense than crude oil and water, air injected into the oil reservoir tends to accumulate upward, resulting in a faster combustion rate in the upper part of the oil reservoir than in the lower part. This is known as "fire line overlap," and its morphology resembles an inverted frustum that gradually expands outward. Due to significant variations in permeability, porosity, and oil and water saturation across the formation, the fire line actually advances irregularly. During actual fireflooding production, various factors, such as compressor outages, production well failures, high formation water content, and poorly developed flue gas pathways, can lead to unstable combustion and even extinguishment of the fire line. Because the fire line advances within the formation, its combustion state cannot be directly observed and can only be assessed indirectly, using parameters such as the injection rate (also known as ventilation intensity) and pressure of individual wells and the compositional characteristics of the combustion gases discharged from production wells. Laboratory studies have also shown that the coke (coke) formed by crude oil at high temperatures (>350°C) is porous and loose, with little impact on formation seepage resistance. However, at low temperatures (<200°C), crude oil reacts with oxygen to form dense coke, which can block the formation and wellbore. Field production has found that formation fire extinguishing often has a lag, with large amounts of air injected into the formation for a period of time after extinguishing the fire. This inevitably leads to the formation clogging at the oxygen-oil contact front, where a large amount of low-temperature coke forms. If repeated ignitions are considered, low oil saturation around the wellbore and coke blockage must be addressed. Low oil saturation can be addressed by recovering crude oil (i.e., returning crude oil from distant formations to the wellbore), while low-temperature coke can be removed by melting it with high-temperature heating or dissolving it with chemical agents. Furthermore, given the large amount of unburned air trapped in the burned zone, the risk of explosion exists if light hydrocarbons carried over from recovered crude oil mix with air, so oxygen control is a key issue. Taking all the above factors into consideration, the use of high-temperature and high-pressure steam for huff and puff (a heavy oil recovery process that includes several steps such as oil injection, well soaking, and recovery) is the best solution. It can simultaneously increase the crude oil saturation near the wellbore, break the blockage of low-temperature coke, and accelerate the consumption of oxygen in the air cavity.

[0081] In summary, the present invention addresses the problems of low-temperature oxidation coke clogging the formation, lack of combustibles in the near-wellbore area, and explosion hazards caused by large amounts of oxygen accumulated in the air cavity during the ignition of such wells. Based on the results of indoor research on crude oil oxidation characteristics and the migration characteristics of formation fluids, a process technology for repeated ignition of fire-driven fire-extinguishing wells is proposed. This technology achieves repeated ignition of fire-extinguishing wells while ensuring safety, restores the high-temperature combustion state of the formation, improves the supporting process technology for fire-driven ignition, and provides reliable support for the promotion and application of fire-driven technology.

[0082] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A fire-driven fire-extinguishing well repeated ignition process, characterized in that: The steps include: Step 1) Obtain the combustion radius of the fire extinguishing well group; when When , go directly to step 4) and repeat the ignition operation; when , then go to step 2); when When the well group is not able to be ignited repeatedly, the adjacent well group with high oil saturation should be selected for ignition repeatedly. in, is the combustion radius of the fire extinguishing well group, in m; is the effective thickness of the oil layer, in m; Step 2) Obtain gas sampling results and, based on the oxygen and methane concentrations in the mixed gas in the wellbore, inject high-temperature steam, followed by soaking the well. The high-temperature steam injection process is as follows: Get gas sampling results, If the oxygen concentration in the mixed gas in the wellbore is greater than 8% and the methane concentration is greater than 5%, the wellbore should be flushed and pressurized with a well-flushing fluid. After the wellbore is filled with the well-flushing fluid, clean water twice the volume of the wellbore should be injected into the formation, followed by high-temperature steam. If the oxygen concentration in the mixed gas in the wellbore is ≤5%, high-temperature steam is directly injected into the wellbore; The volume of high-temperature steam injected is: in, V is the volume of high-temperature steam injected, is the total amount of air injected, is the amount of air consumed per unit of crude oil combustion, is the oil saturation, is the oil layer porosity; When injecting high-temperature steam, first inject 1 / 4V to 1 / 3V of high-temperature steam, then hold the well for 5-10 days, then open the well for production, and determine whether the saturation meets the repeated ignition conditions according to step 4). If not, repeat this step and inject the remaining volume of high-temperature steam. Step 3) Assess wellbore safety risks and, based on the analysis of wellhead gas sampling results after the well is shut down, decide whether to continue injecting high-temperature steam or open the well for production. Step 4) analyzing the oil saturation of the near-wellbore area, determining re-ignition process parameters based on the oil saturation, and performing re-ignition operations based on the re-ignition process parameters.

2. The repeated ignition process for fire-driven fire-extinguishing wells according to claim 1, characterized in that: In step 1), the calculation process of the combustion radius of the fire extinguishing well group is: Where, is the combustion radius of the fire extinguishing well group, is the total amount of air injected, is the amount of air consumed per unit of crude oil combustion, is the oil saturation, is the oil layer porosity, is the effective thickness of the oil layer.

3. The repeated ignition process for fire-driven fire-extinguishing wells according to claim 1, characterized in that: The temperature of the high-temperature steam is 200°C or higher.

4. The repeated ignition process for fire-driven fire-extinguishing wells according to claim 1, characterized in that: In step 3), the specific process of assessing wellbore safety risks is as follows: Analyze based on wellhead gas sampling results; When the oxygen concentration in the mixed gas in the wellbore is ≥5%, return to step 2) and continue to inject high-temperature steam and soak the well until the oxygen concentration in the mixed gas in the wellbore is <5%; When the oxygen concentration in the mixed gas in the wellbore is less than 5%, the well is opened for production.

5. The repeated ignition process for fire-driven fire-extinguishing wells according to claim 1, characterized in that: In step 4), the oil saturation in the area near the wellbore is analyzed. When the oil saturation is greater than 25%, a rapid temperature rise ignition process is adopted; In the rapid temperature rise ignition process, the heating rate is 8~10℃ / min, the ignition temperature is greater than 450℃, and the igniter outlet is set in the lower middle part of the oil layer.

6. The repeated ignition process for fire-driven fire-extinguishing wells according to claim 1, characterized in that: During the repeated ignition operation in step 4), the combustion dynamics of the ignition process and the composition of the gas produced by the surrounding production wells are calculated to determine whether the repeated ignition is successful; When the effective heating radius around the wellbore is greater than 450℃ and exceeds 0.5m, and the oxygen concentration in the mixed gas of the surrounding production wells is less than 1%, the carbon dioxide concentration is greater than 9%, and the nitrogen concentration is greater than 70%, the repeated ignition is successful, otherwise the repeated ignition fails.

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