A method and system for enhanced recovery of carbonate reservoirs

Abstract

The application discloses a carbonate rock oil reservoir recovery improvement method and system, and performs thermal gravity analysis on crude oil extracted from a light oil reservoir, divides the whole process of crude oil oxidation according to a DSC curve peak value and an inflection point; different oxygen concentration reduction oxygen air is configured for the divided whole process of crude oil oxidation; oxygen concentration, gas injection amount and oxidation time of the different oxygen concentration reduction oxygen air are changed based on reservoir temperature and pressure, the different oxygen concentration reduction oxygen air is injected into a stratum, and influence on crude oil oxidation characteristics is analyzed; the best reduction oxygen air injection parameter suitable for the light oil reservoir is determined according to the influence of the different oxygen concentration reduction oxygen air on the crude oil oxidation characteristics, and the recovery of the carbonate rock oil reservoir is improved. The crude oil production is greatly improved, and the application prospect is wide.

Description

Technical Field

[0001] This invention belongs to the field of petroleum extraction engineering technology, specifically relating to a method and system for improving the recovery rate of carbonate oil reservoirs. Background Technology

[0002] The discontinuous and highly heterogeneous spatial distribution of fractured-vuggy carbonate reservoirs makes it impossible to apply mature development theories and technologies to sandstone reservoirs. Carbonate oil and gas reservoirs occupy an important position among conventional oil reservoirs; 40% of the world's large oil reservoirs are carbonate oil and gas reservoirs, accounting for approximately 60% of the total geological reserves and 50% of the total production of conventional oil reservoirs. Fractured-vuggy carbonate reservoirs mainly consist of large caverns and dissolution cavities as the primary reservoir spaces, with fractures serving as the main flow channels.

[0003] Gas is an excellent displacement medium for oil displacement and replenishing formation energy. Air-driven technology, which uses air as a medium, has significant advantages such as easy injection, abundant gas supply, low cost, and environmental friendliness. The field application of air-driven technology abroad has achieved great success and high economic benefits, which is of great significance for the production and recovery rate of fractured-vuggy carbonate reservoirs.

[0004] Air injection is applicable to a wide range of reservoir types, depths, and areas due to its wide availability, lack of geographical and spatial limitations, abundant gas resources, and low cost (compared to CO2, N2, and flue gas). Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method and system for improving the recovery rate of carbonate reservoirs, which is applicable to fractured-vuggy carbonate reservoirs and improves the recovery rate, in order to address the shortcomings of the prior art.

[0006] The present invention adopts the following technical solution:

[0007] This invention discloses a method for improving oil recovery in carbonate reservoirs, comprising the following steps:

[0008] S1. Identify fractured-vuggy carbonate reservoirs and determine whether they are light oil reservoirs based on the relative density of crude oil.

[0009] S2. Perform field measurements on the light oil reservoir determined in step S1 to determine the formation temperature and pressure of the oil reservoir in a single well, and determine the oil reservoir temperature and pressure based on the formation temperature and pressure of the oil reservoir in a single well.

[0010] S3. Perform thermogravimetric analysis on the crude oil extracted from the light oil reservoir in step S2, and divide the entire crude oil oxidation process according to the peak value and inflection point of the DSC curve; for each divided crude oil oxidation process, configure deoxygenated air with different oxygen concentrations.

[0011] S4. Based on the reservoir temperature and pressure determined in step S2, change the oxygen concentration, injection volume and oxidation time of the oxygen-deoxygenated air with different oxygen concentrations configured in step S3, inject the oxygen-deoxygenated air with different oxygen concentrations into the formation, and analyze the impact on the oxidation characteristics of crude oil.

[0012] S5. Based on the influence of different oxygen concentrations of deoxygenated air on the oxidation characteristics of crude oil in step S4, determine the optimal deoxygenated air injection parameters suitable for light oil reservoirs to improve the recovery rate of carbonate reservoirs.

[0013] Specifically, in step S1, the actual reserves and stratigraphic rock composition of the oil reservoir are detected, seismic waves are generated on the ground, and the reflection information of the underground geological body is received by the geophone to determine the distribution of the oil reservoir; the reflection information of the geological body is reconstructed based on the simulation of the field seismic data acquisition process according to the stratigraphic attribute parameters, and then the reflection information reconstructed by the wavefield is compared and analyzed with the reflection information actually acquired in the field to determine the fracture-vuggy carbonate reservoir.

[0014] Specifically, in step S1, when the relative density of crude oil is less than or equal to 0.852, the fractured-vuggy carbonate reservoir is a light reservoir.

[0015] Specifically, step S2 is as follows:

[0016] S201. Based on the well depth data and the measured formation temperature of the light oil reservoir in step S1, perform statistical regression analysis to determine the relationship between temperature and well depth; substitute the depth data of the middle part of the reservoir into the formula for the relationship between temperature and well depth to determine the temperature of the middle part of the reservoir, and convert the unit of the temperature of the middle part of the reservoir from Celsius to thermodynamic temperature.

[0017] S202. Perform statistical regression analysis based on the measured pressure and well depth data of each well to determine the relationship between pressure and well depth; substitute the depth data of the middle part of the reservoir into the formula for the relationship between pressure and well depth to determine the reservoir pressure.

[0018] Furthermore, the specific relationship between temperature t and well depth h is as follows:

[0019] t = 0.031h + 17.2

[0020] The specific relationship between pressure P and well depth h is as follows:

[0021] P = 0.014h - 23.2

[0022] Specifically, in step S3, the TG and DTG curves are analyzed. Based on the peak value and inflection point of the DSC curve, the entire crude oil oxidation process is divided into four stages: light hydrocarbon volatilization, low-temperature oxidation, fuel deposition, and high-temperature oxidation.

[0023] Specifically, in step S3, air and nitrogen are mixed to prepare oxygen-reduced air. If the oxygen concentration is greater than the set value, the amount of nitrogen injected is increased; if the oxygen concentration is less than the set value, the amount of air injected is increased, thus obtaining oxygen-reduced air with different oxygen concentrations.

[0024] Specifically, in step S5, when the reservoir temperature is below 120°C, oxygen-reducing air drive technology is used to reduce the oxygen concentration of the injected air to less than 10%; when the reservoir temperature is above 120°C, air drive technology is used.

[0025] Specifically, after step S5 is completed, the influence of different formation conditions on crude oil oxidation characteristics is analyzed. Combined with the influence of optimal deoxygenated air injection parameters on crude oil oxidation characteristics, the effect of deoxygenated air on enhanced oil recovery is analyzed. Secondly, this invention provides a system for enhancing oil recovery in carbonate reservoirs, including:

[0026] The reservoir module identifies fractured-vuggy carbonate reservoirs and determines whether they are light reservoirs based on the relative density of crude oil.

[0027] The measurement module performs measurements on the light reservoirs identified by the reservoir determination module to determine the formation temperature and pressure of a single well in the reservoir, and then determines the reservoir temperature and pressure based on the formation temperature and pressure of the single well.

[0028] The crude oil produced from the light oil reservoir in the measured module is divided into modules. Thermogravimetric analysis is performed on the crude oil. The entire oxidation process of crude oil is divided according to the peak value and inflection point of the DSC curve. For each divided crude oil oxidation process, deoxygenated air with different oxygen concentrations is configured.

[0029] The analysis module, based on the reservoir temperature and pressure determined by the measurement module, changes the oxygen concentration, injection volume, and oxidation time of the deoxygenated air with different oxygen concentrations configured in the division module, injects deoxygenated air with different oxygen concentrations into the formation, and analyzes the impact on the oxidation characteristics of crude oil.

[0030] The recovery module, based on the influence of different oxygen concentrations of deoxygenated air on the oxidation characteristics of crude oil obtained from the analysis module, determines the optimal deoxygenated air injection parameters suitable for light oil reservoirs, thereby improving the recovery rate of carbonate oil reservoirs.

[0031] Compared with the prior art, the present invention has at least the following beneficial effects:

[0032] This invention discloses a method for enhancing oil recovery in carbonate reservoirs. The low-temperature oxidation reaction of crude oil is complex and difficult to represent with a single chemical reaction equation. On one hand, O2 in the air reacts with crude oil to generate organic compounds such as aldehydes, ketones, alcohols, and carboxylic acids. On the other hand, crude oil undergoes bond-breaking reactions to generate associated gas components such as CO and CO2. The low-temperature oxidation process of crude oil includes both oxygenation and bond-breaking reactions. In static oxidation experiments, some light components in the crude oil participate in the oxidation reaction, and the gas is the excess phase, resulting in an increase in the final viscosity of the crude oil. However, in dynamic displacement, the crude oil is the excess phase, and the contact between the crude oil and air in the core is limited to the displacement front. Locally, the crude oil viscosity increases behind the displacement front (in the positive displacement direction), while the area in front of the displacement front remains unaffected. Conversely, the heat generated by the oxidation reaction is transferred to the front of the displacement edge. On the one hand, the crude oil expands due to heat, driving it to flow towards the production end; on the other hand, the viscosity of the crude oil decreases due to heat, which is conducive to the flow of crude oil. Low-temperature oxidation can generate some CO, CO2, and CH4 gases, forming flue gas drive in the reservoir. It has certain effects on miscibility, viscosity reduction, and reduction of interfacial tension. After implementation, it will greatly improve the utilization of low-grade reserves and the recovery rate of "high-oil-quality, high-temperature, and high-efficiency" reservoirs, thereby significantly increasing crude oil production. It has broad application prospects.

[0033] Furthermore, in reflection wave seismic exploration, seismic waves are generated at the surface, and geophones receive the reflection information from underground geological bodies. The obtained reflection information is then processed and interpreted through a series of seismic data steps to obtain various attributes in the depth domain, thereby determining the distribution of oil reservoirs. Based on the obtained stratigraphic attribute parameters, the reflection information of geological bodies is reconstructed by simulating the field seismic data acquisition process (this process of reconstructing the reflection information of underground geological bodies is also called wavefield reconstruction). Then, the reflection information reconstructed from the wavefield is compared and analyzed with the actual reflection information acquired in the field to determine the underground oil and gas reservoir structure.

[0034] Furthermore, the air injection development of light and heavy oil reservoirs differs in its mechanism of action, leading to different development methods. Therefore, density measurements are conducted to determine the reservoir properties.

[0035] Furthermore, to determine the optimal oxygen concentration for deoxygenation air in the reservoir, laboratory experiments are needed. These experiments will be conducted in a reactor to simulate formation conditions, namely formation temperature and pressure, as closely as possible. Understanding formation temperature and pressure is crucial for mimicking these conditions and determining the effectiveness of crude oil oxidation.

[0036] Furthermore, based on the peak value and inflection point of the DSC curve, the entire crude oil oxidation process is divided into four stages: light hydrocarbon volatilization, low-temperature oxidation (LTO), fuel deposition (FD), and high-temperature oxidation (HTO). After air is injected into the reservoir, it undergoes a complex exothermic oxidation reaction with the crude oil, and the reaction mechanism and thermal effect change with temperature. During the air injection development of the reservoir, different development methods correspond to different reaction temperature ranges, and the development mechanism is controlled by the crude oil oxidation mechanism within that temperature range.

[0037] Furthermore, during the indoor oxygen-reduced air experiment, it cannot be determined whether the oxygen content is most effective for crude oil oxidation. It is necessary to prepare oxygen-reduced air with different oxygen contents and conduct experiments one by one to determine the optimal oxygen content for the block.

[0038] Furthermore, when the reservoir temperature is below 120℃, the heat release from the oxygenation reaction between air and crude oil is minimal. Under reservoir conditions, the heat released from the reaction is difficult to accumulate, and oxygen cannot be fully consumed under formation conditions. If the oxygen content in the production well exceeds 10%, there is a risk of explosion. The main operational strategy for this type of reservoir is to reduce the oxygen concentration of the injected air to below 10%, employing deoxygenated air drive technology. When the reservoir temperature is above 120℃, low-temperature oxidation gradually becomes the main reaction type. Oxygen is fully consumed within the reservoir, and the heat released from the reaction can be effectively accumulated, which can increase the reservoir temperature, reduce crude oil viscosity, and increase crude oil fluidity. When light oil reservoirs are in this temperature range, air drive technology can be used for safe development. Due to differences in reservoir mineral catalysis, oil oxidation characteristics, reservoir pressure, injection-production well spacing, and fracture conditions, when the reservoir temperature is around 120℃, specific analysis is required to determine whether to use deoxygenated air drive or air drive for development.

[0039] Furthermore, the low-temperature oxidation stage requires the lowest activation energy; the oxygen concentration in the reacting gases is negatively correlated with the activation energy required for the reaction—the higher the oxygen concentration, the lower the average activation energy required for the oxidation reaction. The low-temperature oxidation reaction between crude oil and oxygen-containing air generates a large amount of heat energy, as well as some CO, CO2, and CH4 gases, forming flue gas drive within the reservoir. This has certain effects on miscibility, viscosity reduction, lowering interfacial tension, and promoting crude oil expansion, thus contributing to improved oil recovery. Under suitable reservoir temperatures, for all pore-throat regions at all scales, deoxygenated air drive yields higher recovery rates than nitrogen drive; therefore, air / deoxygenated air drive development should be the preferred method.

[0040] It is understood that the beneficial effects of the second and third aspects mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here.

[0041] In summary, this invention addresses the challenges of air injection for energy replenishment and enhanced oil recovery in oilfield development. It provides a more comprehensive understanding of low-temperature crude oil conditions and offers a scientifically reliable basis for effectively preventing safety accidents during air injection / oxygen-reduced air injection operations. Solving safety issues, its implementation will significantly improve the utilization of low-grade reserves and the recovery rate of high-temperature, high-volume, and high-yield oil reservoirs, thereby substantially increasing crude oil production. Its application prospects are broad.

[0042] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0043] Figure 1 A schematic diagram of the stratigraphic structure of a fractured-vuggy carbonate oil reservoir;

[0044] Figure 2 This is a schematic diagram of the process of the present invention;

[0045] Figure 3 This is a schematic diagram of a computer device provided according to an embodiment of the present invention. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] In the description of this invention, it should be understood that the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0048] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0049] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations. For example, A and / or B can represent three cases: A alone, A and B simultaneously, and B alone. Additionally, the character " / " in this document generally indicates that the preceding and following objects have an "or" relationship.

[0050] It should be understood that although terms such as first, second, third, etc., may be used in the embodiments of the present invention to describe the preset range, these preset ranges should not be limited to these terms. These terms are only used to distinguish the preset ranges from one another. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0051] Depending on the context, the word "if" as used here can be interpreted as "when," "when," "in response to determination," or "in response to detection." Similarly, depending on the context, the phrase "if determination" or "if detection (of the stated condition or event)" can be interpreted as "when determination," "in response to determination," "when detection (of the stated condition or event)," or "in response to detection (of the stated condition or event)."

[0052] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0053] Please see Figure 1 The three-layer fractured-vuggy carbonate reservoir is a model that scales down the reservoir block to show the approximate distribution of fractures and vuggies in each layer.

[0054] This invention provides a method for improving oil recovery in carbonate reservoirs. Thermogravimetric analysis (TGA) is used to perform TGA on dehydrated crude oil. Based on the peak value and inflection point of the DSC curve, the entire crude oil oxidation process can be divided into four stages: light hydrocarbon volatilization, low-temperature oxidation (LTO), fuel deposition (FD), and high-temperature oxidation (HTO). When the reservoir temperature is below 120°C, the heat release from the oxygenation reaction between air and crude oil is minimal. Under reservoir conditions, the heat release from the reaction is difficult to accumulate, and oxygen cannot be fully consumed under formation conditions. If the oxygen content in the production well exceeds 10%, there is a risk of explosion. The main operational strategy for this type of reservoir is to reduce injection... When the oxygen concentration in the air is below 10%, deoxygenated air drive technology is used. When the reservoir temperature is above 120℃, low-temperature oxidation gradually becomes the main reaction type. Oxygen is fully consumed in the reservoir, and the exothermic reaction can be effectively accumulated, which can increase the reservoir temperature, reduce the viscosity of crude oil, and increase the fluidity of crude oil. When the light oil reservoir is in this temperature range, air drive technology is used to achieve safe development. Due to the different conditions such as reservoir mineral catalysis, oil oxidation characteristics, reservoir pressure, injection-production well spacing, and fractures, when the reservoir temperature is 120℃, the specific situation is analyzed to determine whether to use deoxygenated air drive or air drive for development. This study aims to determine the effectiveness of deoxygenated air in enhancing oil recovery in fractured-vuggy carbonate reservoirs; address the need for laboratory experiments to understand the low-temperature oxidation of crude oil in existing carbonate reservoir blocks to determine the optimal injection parameters (oxygen concentration, injection volume, and oxidation time); resolve the insufficient understanding of the low-temperature oxidation process of crude oil; address the insufficient understanding of the influence of formation conditions on the crude oil oxidation process; overcome the challenges of large workload, long duration, technical complexity, and high cost of laboratory experiments; and resolve the issue of insufficient funding preventing the implementation of experiments.

[0055] Gas chromatography was used to analyze changes in the carbon composition of crude oil, extraction method was used to analyze changes in the group components of crude oil, viscoelasticity tester was used to analyze changes in the viscosity of crude oil before and after oxidation, gas chromatography was used to analyze the content of each component in the gas after oxidation, and pressure sensor was used to monitor changes in the overall process pressure.

[0056] Crude oil viscosity is the most direct indicator reflecting changes in crude oil properties. The relative content of crude oil group components is the direct cause of changes in crude oil viscosity. In particular, non-hydrocarbon and asphaltenes contain large amounts of large polar compounds such as sulfur, nitrogen, and oxygen, which easily increase crude oil viscosity. O2 is still present in associated gas after low-temperature oxidation. In actual production processes, attention should be paid to controlling the O2 concentration in associated gas to avoid safety accidents.

[0057] Please see Figure 2 The present invention discloses a method for improving the recovery rate of carbonate oil reservoirs, comprising the following steps:

[0058] S1. Determine whether the reservoir is a fractured-vuggy carbonate reservoir. Determine whether the fractured-vuggy carbonate reservoir is a light oil reservoir based on the relative density of the crude oil.

[0059] Conduct a comprehensive geological exploration of the oil reservoir in the block, detect the actual reserves of the reservoir, analyze the composition of the strata rocks, determine whether it is a carbonate reservoir, and explore the strata void volume and porosity.

[0060] In reflection wave seismic exploration, we generate seismic waves at the surface and use geophones to receive the reflection information from underground geological bodies. The obtained reflection information is then processed and interpreted to obtain various depth-domain attributes, thereby determining the distribution of oil reservoirs. Based on the obtained stratigraphic attribute parameters, the reflection information of geological bodies is reconstructed by simulating the field seismic data acquisition process (this process of reconstructing the reflection information of underground geological bodies is also called wavefield reconstruction). The reconstructed reflection information is then compared and analyzed with the actual reflection information acquired in the field to determine the underground oil and gas reservoir structure.

[0061] Determining whether a fractured-vuggy carbonate reservoir is a light oil reservoir based on the relative density of crude oil is as follows:

[0062] Crude oil samples are obtained from the wellhead of the oil reservoir that requires air injection. The relative density of the crude oil is then measured to obtain the relative density of the crude oil. When the measured relative density of the crude oil is less than or equal to 0.852, the fractured-vuggy carbonate reservoir is a light oil reservoir. The air injection mechanism and development method of light oil reservoir and heavy oil reservoir are different. Therefore, the density measurement of the oil reservoir is necessary to confirm the nature of the oil reservoir.

[0063] S2. Conduct field measurements on the light oil reservoir determined in step S1 to determine the formation temperature and pressure of the oil reservoir in a single well. Based on the formation temperature and pressure of the oil reservoir in a single well, determine the oil reservoir temperature and pressure as the basic experimental conditions for carrying out the indoor research experiment in step S4.

[0064] Downhole temperature and pressure sensors were installed in the middle of the oil layer of each production and injection well to measure downhole temperature, temperature gradient, pressure, and pressure gradient.

[0065] S201. Based on the measured formation temperature and well depth data of each well, perform statistical regression analysis to derive the formula for the relationship between temperature and well depth; substitute the depth data of the middle part of the reservoir into the formula for the relationship between temperature and well depth to determine the temperature of the middle part of the reservoir, and convert the unit of the temperature of the middle part of the reservoir from Celsius to thermodynamic temperature.

[0066] The specific formula for the relationship between temperature and well depth is as follows:

[0067] Statistical regression analysis of well temperature and depth data yielded the formula for the relationship between temperature and well depth: t = 0.031h + 17.2. From this formula, the reservoir depth is 6800m, and substituting this into the temperature-depth formula, the reservoir temperature is determined to be 160℃.

[0068] h represents the well depth, 0.031 is the coefficient between well depth and temperature, and 17.2 is a constant.

[0069] S202. Based on the measured pressure and well depth data of each well, perform statistical regression analysis to derive the formula for the relationship between pressure and well depth; substitute the depth data of the middle part of the reservoir into the formula for the relationship between pressure and well depth to determine the reservoir pressure.

[0070] The specific formula for the relationship between pressure and well depth is as follows:

[0071] Statistical regression analysis of well temperature and depth data yielded the formula for the relationship between temperature and well depth: t = 0.031h + 17.2. From this formula, the reservoir depth is 6800m, and substituting this into the temperature-depth formula, the reservoir temperature is determined to be 160℃.

[0072] h represents the well depth, 0.031 is the coefficient between well depth and temperature, and 17.2 is a constant.

[0073] S3. Perform thermogravimetric analysis on the crude oil extracted from the light oil reservoir in step S2. Based on the peak value and inflection point of the DSC curve, the entire process of crude oil oxidation can be divided into four stages: light hydrocarbon volatilization, low temperature oxidation (LTO), fuel deposition (FD), and high temperature oxidation (HTO). Different oxygen-depleted air with different oxygen concentrations is prepared for each stage.

[0074] The extracted crude oil is dehydrated, and then thermogravimetric analysis (TGA) is performed on the dehydrated crude oil in the full temperature range of 0–700℃. The TG and DTG curves are analyzed, and the temperature range of 0–700℃ is divided into three stages: low-temperature oxidation, fuel deposition, and high-temperature oxidation.

[0075] The specific steps for configuring oxygen-depleted air with different oxygen concentrations are as follows:

[0076] The process involves mixing air and nitrogen to create oxygen-reduced air. Air is readily available locally, while nitrogen is purchased. The two gases are mixed, and a gas analyzer is used to analyze the oxygen content of the mixture.

[0077] If the oxygen concentration is greater than the set value, increase the amount of nitrogen injected to reduce the oxygen concentration.

[0078] If the oxygen concentration is lower than the set value, increase the amount of air injected to increase the oxygen concentration.

[0079] S5. Change the oxygen concentration, injection volume, and oxidation time of the deoxygenated air configured in step S4, inject the deoxygenated air with different oxygen concentrations into the formation, and analyze the impact on the oxidation characteristics of crude oil. The characteristic parameters of crude oil (viscosity, group component content, total hydrocarbon content, and gas component concentration) change with the oxygen concentration of the deoxygenated air. Based on the impact of deoxygenated air with different oxygen concentrations on the oxidation characteristics of crude oil, determine the optimal deoxygenated air injection parameters suitable for light oil reservoirs to improve the recovery rate of carbonate oil reservoirs.

[0080] After determining the parameters, the influence of the geological conditions of the block on the low-temperature oxidation process of crude oil should also be considered, mainly the influence of geological conditions (water content and filling degree) on the characteristic parameters of crude oil oxidation.

[0081] By varying the oxygen concentration, oxidation time, and injection volume (based on the reservoir crude oil volume, which is the ratio of the injected deoxygenated air volume to the reservoir crude oil volume) and injecting these parameters into the formation, the characteristic parameters of crude oil oxidation (crude oil carbon composition, group composition, crude oil viscosity, oxygen concentration of injected deoxygenated air, and pressure changes during the reaction stage) are analyzed.

[0082] Based on the analysis of TG and DTG curves and oxidation characteristic parameters, the optimal injection parameters suitable for the block are analyzed. Combined with the influence of different formation conditions (water-bearing, sand-bearing) on ​​the oxidation characteristics of crude oil (crude oil carbon composition, group composition, crude oil viscosity, oxygen concentration of injected deoxygenated air, and pressure changes during the reaction stage), the effect of deoxygenated air on improving the recovery rate of fractured-vuggy carbonate reservoirs is analyzed.

[0083] After the experiment, the harvesting effect was verified, mainly by viscosity, group component content, and gas component content.

[0084] S6. Analyze the influence of different formation conditions (water-bearing, sand-bearing) on ​​the oxidation characteristics of crude oil;

[0085] Based on the optimal deoxygenated air injection parameters suitable for the block, the effects of formation water content (reservoir water cut) and sand content (formation fracture and cavity filling degree) on crude oil oxidation characteristic parameters (crude oil carbon composition, group composition, crude oil viscosity, oxygen concentration of injected deoxygenated air, and pressure changes during the reaction stage) are analyzed.

[0086] S7. Combining the optimal deoxygenated air injection parameters obtained in step S5 and the influence of formation conditions on crude oil oxidation characteristics in step S6, analyze the effect of deoxygenated air on improving oil recovery.

[0087] Based on the analysis of the optimal deoxygenated air injection parameters applicable to the block and the formation conditions (water-bearing, sand-bearing) on ​​the characteristic parameters of crude oil oxidation, this paper further analyzes the method of implementing deoxygenated air drive to improve oil recovery in fractured-vuggy carbonate rocks.

[0088] In another embodiment of the present invention, a system for enhancing the recovery rate of carbonate reservoirs is provided. This system can be used to implement the above-mentioned method for enhancing the recovery rate of carbonate reservoirs. Specifically, the system for enhancing the recovery rate of carbonate reservoirs includes a reservoir module, a measurement module, a division module, an analysis module, and a recovery module.

[0089] Among them, the reservoir module identifies fractured-vuggy carbonate reservoirs and determines whether fractured-vuggy carbonate reservoirs are light reservoirs based on the relative density of crude oil.

[0090] The measurement module performs measurements on the light reservoirs identified by the reservoir determination module to determine the formation temperature and pressure of a single well in the reservoir, and then determines the reservoir temperature and pressure based on the formation temperature and pressure of the single well.

[0091] The crude oil produced from the light oil reservoir in the measured module is divided into modules. Thermogravimetric analysis is performed on the crude oil. The entire oxidation process of crude oil is divided according to the peak value and inflection point of the DSC curve. For each divided crude oil oxidation process, deoxygenated air with different oxygen concentrations is configured.

[0092] The analysis module, based on the reservoir temperature and pressure determined by the measurement module, changes the oxygen concentration, injection volume, and oxidation time of the deoxygenated air with different oxygen concentrations configured in the division module, injects deoxygenated air with different oxygen concentrations into the formation, and analyzes the impact on the oxidation characteristics of crude oil.

[0093] The recovery module, based on the influence of different oxygen concentrations of deoxygenated air on the oxidation characteristics of crude oil obtained from the analysis module, determines the optimal deoxygenated air injection parameters suitable for light oil reservoirs, thereby improving the recovery rate of carbonate oil reservoirs.

[0094] In another embodiment of the present invention, a terminal device is provided, comprising a processor and a memory. The memory stores a computer program, the computer program including program instructions, and the processor executes the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions to achieve a corresponding method flow or corresponding function. The processor described in this embodiment of the present invention can be used in the operation of a method for improving the recovery rate of carbonate oil reservoirs, including:

[0095] This study identifies fractured-vuggy carbonate reservoirs and determines whether they are light oil reservoirs based on the relative density of the crude oil. It then conducts field measurements on the light oil reservoirs to determine the formation temperature and pressure of individual wells, and subsequently determines the reservoir temperature and pressure. Thermogravimetric analysis (TGA) is performed on the crude oil produced from the light oil reservoirs, and the entire oxidation process is divided based on the peak and inflection points of the DSC curves. For each of the defined oxidation processes, deoxygenated air with different oxygen concentrations is injected. Based on the reservoir temperature and pressure, the oxygen concentration, injection rate, and oxidation time of the deoxygenated air are varied, and the impact on the oxidation characteristics of the crude oil is analyzed. Based on the influence of different oxygen concentrations of deoxygenated air on the oxidation characteristics of crude oil, the optimal deoxygenated air injection parameters suitable for light oil reservoirs are determined to improve the recovery rate of carbonate reservoirs.

[0096] In another embodiment of the present invention, a storage medium is also provided, specifically a computer-readable storage medium (memory). This computer-readable storage medium is a memory device in a terminal device used to store programs and data. It is understood that the computer-readable storage medium here can include both the built-in storage medium in the terminal device and extended storage media supported by the terminal device. The computer-readable storage medium provides storage space that stores the terminal's operating system. Furthermore, this storage space also stores one or more instructions suitable for loading and execution by a processor. These instructions can be one or more computer programs (including program code). It should be noted that the computer-readable storage medium here can be high-speed RAM or non-volatile memory, such as at least one disk storage device.

[0097] One or more instructions stored in a computer-readable storage medium can be loaded and executed by a processor to implement the corresponding steps of the method for improving the recovery rate of carbonate reservoirs in the above embodiments; one or more instructions in the computer-readable storage medium are loaded and executed by the processor in the following steps:

[0098] This study identifies fractured-vuggy carbonate reservoirs and determines whether they are light oil reservoirs based on the relative density of the crude oil. It then conducts field measurements on the light oil reservoirs to determine the formation temperature and pressure of individual wells, and subsequently determines the reservoir temperature and pressure. Thermogravimetric analysis (TGA) is performed on the crude oil produced from the light oil reservoirs, and the entire oxidation process is divided based on the peak and inflection points of the DSC curves. For each of the defined oxidation processes, deoxygenated air with different oxygen concentrations is injected. Based on the reservoir temperature and pressure, the oxygen concentration, injection rate, and oxidation time of the deoxygenated air are varied, and the impact on the oxidation characteristics of the crude oil is analyzed. Based on the influence of different oxygen concentrations of deoxygenated air on the oxidation characteristics of crude oil, the optimal deoxygenated air injection parameters suitable for light oil reservoirs are determined to improve the recovery rate of carbonate reservoirs.

[0099] Please see Figure 3 As shown, the computer device 60 in this embodiment includes a processor 61, a memory 62, and a computer program 63 stored in the memory 62 and executable on the processor 61. When the processor 61 executes the computer program 63, it implements the method for enhancing the recovery rate of carbonate reservoirs in this embodiment. To avoid repetition, these details are not elaborated here. Alternatively, when the processor 61 executes the computer program 63, it implements the functions of each model / unit in the system for enhancing the recovery rate of carbonate reservoirs in this embodiment. To avoid repetition, these details are not elaborated here.

[0100] Computer device 60 can be a desktop computer, laptop, handheld computer, cloud server, or other computing device. Computer device 60 may include, but is not limited to, a processor 61 and a memory 62. Those skilled in the art will understand that... Figure 3 This is merely an example of computer device 60 and does not constitute a limitation on computer device 60. It may include more or fewer components than shown, or combine certain components, or different components. For example, computer device may also include input / output devices, network access devices, buses, etc.

[0101] The processor 61 may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor.

[0102] The memory 62 can be an internal storage unit of the computer device 60, such as a hard disk or RAM of the computer device 60. The memory 62 can also be an external storage device of the computer device 60, such as a plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, etc., provided on the computer device 60.

[0103] Furthermore, the memory 62 may include both internal storage units of the computer device 60 and external storage devices. The memory 62 is used to store computer programs and other programs and data required by the computer device. The memory 62 can also be used to temporarily store data that has been output or will be output.

[0104] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0105] Current indoor experimental studies mainly focus on the low-temperature oxidation mechanism, influencing factors, safety control, and kinetic characteristics. However, the gas composition and crude oil composition change after air injection and low-temperature oxidation in light oil reservoirs, leading to alterations in crude oil properties. Currently, there is limited research on these two aspects. Conducting low-temperature oxidation experiments, analyzing the changes in gas composition and crude oil physicochemical properties after the low-temperature oxidation reaction, and understanding the impact of low-temperature oxidation on the properties of the gas and crude oil before and after the reaction are of greater significance for understanding the changes in light oil reservoir conditions after air injection and for gaining a deeper understanding of the displacement mechanism.

[0106] To address the development challenges posed by the accelerated rate of water cut increase and the combined and natural decline rates after the reservoir entered the mid-water-cut stage, the Wuliwan No. 1 Block of the Changqing Jing'an Oilfield conducted pilot and scale-up tests of deoxygenated air drive in December 2009. By the end of 2013, a large-scale industrial test area with 15 injection and 63 production wells had been established. The tests showed that deoxygenated air drive was superior to water drive in replenishing formation energy, improving water drive performance, and expanding the planar sweep area. Field tests yielded good results. The test area produced 60 effective wells with a success rate of 95.2%. By the end of 2019, the cumulative oil production increase during the test period was 6.3 × 10⁻⁶. 4 t, predicting that the final recovery rate could be increased by 10%.

[0107] Liaohe Oilfield conducted an air drive test in the Shen 625 block (reservoir temperature 123℃). The test results showed that the seven well groups in the test area cumulatively increased oil production by 3.4 × 10⁻⁶. 4 t demonstrates good development results and application prospects.

[0108] In summary, the present invention provides a method and system for enhancing oil recovery in carbonate reservoirs, which has the following characteristics:

[0109] 1. The low-temperature oxidation section requires the lowest activation energy; the oxygen concentration in the reacting gas is negatively correlated with the activation energy required for the reaction. The higher the oxygen concentration, the lower the average activation energy required for the oxidation reaction.

[0110] 2. Crude oil undergoes a low-temperature oxidation reaction with oxygen-containing air, generating a large amount of heat energy and producing some CO, CO2, and CH4 gases. This forms a flue gas drive within the reservoir, which has certain effects on miscibility, viscosity reduction, reduction of interfacial tension, and promotion of crude oil expansion, thus helping to improve the recovery rate.

[0111] 3. Under suitable reservoir temperature conditions, for all sizes of pore throat regions, the recovery rate of deoxygenated air drive is higher than that of nitrogen drive, and the air / deoxygenated air drive development method should be given priority.

[0112] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0113] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0114] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0115] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1The steps of the function specified in one or more boxes.

[0116] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for improving oil recovery in carbonate reservoirs, characterized in that, Includes the following steps: S1. Identify fractured-vuggy carbonate reservoirs and determine whether they are light oil reservoirs based on the relative density of crude oil. S2. Perform field measurements on the light oil reservoir determined in step S1 to determine the formation temperature and pressure of the oil reservoir in a single well, and determine the oil reservoir temperature and pressure based on the formation temperature and pressure of the oil reservoir in a single well. S3. Perform thermogravimetric analysis on the crude oil extracted from the light oil reservoir in step S2, and divide the entire crude oil oxidation process according to the peak value and inflection point of the DSC curve; for each divided crude oil oxidation process, configure deoxygenated air with different oxygen concentrations. S4. Based on the reservoir temperature and pressure determined in step S2, change the oxygen concentration, injection volume and oxidation time of the oxygen-deoxygenated air with different oxygen concentrations configured in step S3, inject the oxygen-deoxygenated air with different oxygen concentrations into the formation, and analyze the impact on the oxidation characteristics of crude oil. S5. Based on the influence of different oxygen concentrations of deoxygenated air on the oxidation characteristics of crude oil in step S4, determine the optimal deoxygenated air injection parameters suitable for light oil reservoirs to improve the recovery rate of carbonate reservoirs.

2. The method for enhancing oil recovery in carbonate reservoirs according to claim 1, characterized in that, In step S1, the actual reserves and stratigraphic rock composition of the oil reservoir are detected. Seismic waves are generated on the ground, and the reflection information of the underground geological body is received by the geophone to determine the distribution of the oil reservoir. The reflection information of the geological body is reconstructed based on the simulation of the field seismic data acquisition process according to the stratigraphic attribute parameters. Then, the reflection information reconstructed by the wavefield is compared and analyzed with the reflection information actually acquired in the field to determine the fracture-vuggy carbonate reservoir.

3. The method for enhancing oil recovery in carbonate reservoirs according to claim 1, characterized in that, In step S1, when the relative density of crude oil is less than or equal to 0.852, the fractured-vuggy carbonate reservoir is a light reservoir.

4. The method for enhancing oil recovery in carbonate reservoirs according to claim 1, characterized in that, Step S2 is as follows: S201. Based on the well depth data and the measured formation temperature of the light oil reservoir in step S1, perform statistical regression analysis to determine the relationship between temperature and well depth; substitute the depth data of the middle part of the reservoir into the formula for the relationship between temperature and well depth to determine the temperature of the middle part of the reservoir, and convert the unit of the temperature of the middle part of the reservoir from Celsius to thermodynamic temperature. S202. Perform statistical regression analysis based on the measured pressure and well depth data of each well to determine the relationship between pressure and well depth; substitute the depth data of the middle part of the reservoir into the formula for the relationship between pressure and well depth to determine the reservoir pressure.

5. The method for enhancing oil recovery in carbonate reservoirs according to claim 4, characterized in that, The specific relationship between temperature t and well depth h is as follows: t = 0.031h + 17.2 The specific relationship between pressure P and well depth h is as follows: P = 0.014h - 23.

2.

6. The method for enhancing oil recovery in carbonate reservoirs according to claim 1, characterized in that, In step S3, the TG and DTG curves are analyzed. Based on the peak value and inflection point of the DSC curve, the entire crude oil oxidation process is divided into four stages: light hydrocarbon volatilization, low-temperature oxidation, fuel deposition, and high-temperature oxidation, within the range of 0 to 700℃.

7. The method for enhancing oil recovery in carbonate reservoirs according to claim 1, characterized in that, In step S3, air and nitrogen are mixed to prepare deoxygenated air. If the oxygen concentration is greater than the set value, the amount of nitrogen injected is increased. If the oxygen concentration is less than the set value, the amount of air injected is increased to obtain deoxygenated air with different oxygen concentrations.

8. The method for improving oil recovery in carbonate reservoirs according to claim 1, characterized in that, In step S5, when the reservoir temperature is below 120°C, oxygen-reducing air drive technology is used to reduce the oxygen concentration of the injected air to less than 10%; when the reservoir temperature is above 120°C, air drive technology is used.

9. The method for enhancing oil recovery in carbonate reservoirs according to claim 1, characterized in that, After step S5 is completed, the influence of different formation conditions on crude oil oxidation characteristics is analyzed. Combined with the influence of the optimal deoxygenated air injection parameters on crude oil oxidation characteristics, the effect of deoxygenated air on improving oil recovery is analyzed.

10. A system for enhancing oil recovery in carbonate reservoirs, characterized in that, include: The reservoir module identifies fractured-vuggy carbonate reservoirs and determines whether they are light reservoirs based on the relative density of crude oil. The measurement module performs measurements on the light reservoirs identified by the reservoir determination module to determine the formation temperature and pressure of a single well in the reservoir, and then determines the reservoir temperature and pressure based on the formation temperature and pressure of the single well. The crude oil produced from the light oil reservoir in the measured module is divided into modules. Thermogravimetric analysis is performed on the crude oil. The entire oxidation process of crude oil is divided according to the peak value and inflection point of the DSC curve. For each divided crude oil oxidation process, deoxygenated air with different oxygen concentrations is configured. The analysis module, based on the reservoir temperature and pressure determined by the measurement module, changes the oxygen concentration, injection volume, and oxidation time of the deoxygenated air with different oxygen concentrations configured in the division module, injects deoxygenated air with different oxygen concentrations into the formation, and analyzes the impact on the oxidation characteristics of crude oil. The recovery module, based on the influence of different oxygen concentrations of deoxygenated air on the oxidation characteristics of crude oil obtained from the analysis module, determines the optimal deoxygenated air injection parameters suitable for light oil reservoirs, thereby improving the recovery rate of carbonate oil reservoirs.

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