Reservoir modifying agent for carbon dioxide oil displacement system and application of reservoir modifying agent

Abstract

The invention relates to the related technical field of oil well carbon dioxide oil displacement, and particularly provides a reservoir modifying agent for a carbon dioxide oil displacement system and application of the reservoir modifying agent. The reservoir modifying agent comprises a first component and a second component, the first component comprises RCOOH and a first solvent; r is selected from substituted or unsubstituted C1-6 alkyl groups; the second component comprises M < 1 > M < 2 > CO < 3 > and a second solvent; m1 and M2 are independently selected from Li < + >, Na < + >, K < + > or H < + >, and at least one of M1 and M2 is not H < + >. The first component and the second component are injected into the stratum, the first component and the second component chemically react in the stratum to generate CO2, and the CO2 serves as a chemical oil displacement agent for improving the recovery ratio, has the effect of protecting ground equipment and a casing pipe and has extremely high oil displacement capacity.

Description

Technical Field

[0001] This application relates to the technical field of carbon dioxide flooding in oil wells, and specifically provides a reservoir modifier for carbon dioxide flooding systems and its applications. Background Technology

[0002] Carbon dioxide flooding in oil wells is an enhanced oil recovery technology that reduces crude oil viscosity and improves its fluidity by injecting supercritical CO2. Under high pressure, CO2 dissolves in crude oil, weakening intermolecular forces and significantly reducing viscosity (by 80%-90%). Simultaneously, it expands in volume nearly eightfold, generating expansion pressure that drives crude oil to migrate towards the production well. Dissolved CO2 can also react with crude oil components through esterification and cracking reactions, generating polar substances that improve rheological properties. In porous reservoir media, CO2 can achieve miscible displacement by reducing interfacial tension (as low as 0.1 mN / m), improving microscopic oil displacement efficiency. Furthermore, CO2 can be geologically stored after escaping, achieving carbon emission reduction and offering both economic and environmental benefits. The mechanism of surfactant-based oil well flooding is mainly based on its ability to reduce oil-water interfacial tension and improve wettability. Surfactant molecules (such as anionic and nonionic surfactants) with amphiphilic structures (hydrophilic groups and hydrophobic chains) adsorb at the oil-water interface, significantly reducing interfacial tension (down to below 0.1 mN / m), weakening the adhesion between crude oil and rock, and promoting the stripping of crude oil from pore surfaces. Simultaneously, surfactants alter rock wettability, making the rock surface more hydrophilic, reducing the relative permeability of the oil phase, and driving residual oil to migrate towards the production well. Furthermore, surfactants can emulsify crude oil to form microemulsions, optimizing displacement efficiency by reducing the mobility ratio.

[0003] The main challenges in supercritical CO2 injection for oil well flooding are as follows: First, high-pressure injection exacerbates corrosion of manifolds and wellbores, requiring frequent maintenance or replacement of corrosion-resistant materials, increasing costs. Second, CO2 reacts with formation water to form carbonic acid, easily causing scaling near the wellbore and clogging pore channels. Third, uneven injection profiles, with CO2 mobility exceeding that of crude oil, easily lead to gas channeling, requiring additional profile control operations with limited effectiveness. Fourth, maintaining a high-pressure environment in deep reservoirs may induce reservoir compaction or particulate migration, reducing permeability. Fifth, CO2-associated hydrocarbons in the produced gas require efficient separation and recovery, a complex process with leakage risks. Sixth, dynamic control of construction parameters (such as injection rate and pressure) is difficult, requiring precise matching to geological conditions to avoid ineffective displacement. Furthermore, the technology for real-time on-site monitoring of CO2 distribution and reaction processes is still imperfect, affecting construction safety and efficiency. Summary of the Invention

[0004] In view of this, this application provides a reservoir modifier for a carbon dioxide flooding system and its application. This application involves injecting a first component and a second component into the formation. The first and second components undergo a chemical reaction in the formation to produce CO2. This CO2, as an enhanced oil recovery chemical flooding agent, not only protects surface equipment and casing but also possesses extremely strong oil displacement capabilities.

[0005] In a first aspect, this application provides a reservoir modifier for a carbon dioxide flooding system, the reservoir modifier comprising a first component and a second component; The first component comprises RCOOH and a first solvent; R is selected from substituted or unsubstituted C. 1-6 alkyl; The second component comprises M1M2CO3 and a second solvent; M1 and M2 are each independently selected from Li + Na + K + or H + And at least one of M1 and M2 is not H + ; H is one of M1 and M2. + The other one is not H + When the molar ratio of RCOOH in the first component to M1M2CO3 in the second component is (1-1.2):1 (e.g., 1:1, 1.01:1, 1.02:1, 1.03:1, 1.04:1, 1.05:1, 1.06:1, 1.07:1, 1.08:1, 1.09:1, 1.1:1, 1.11:1, 1.12:1, 1.13:1, 1.14:1, 1.15:1, 1.16:1, 1.17:1, 1.18:1, 1.19:1, or 1.2:1, etc.), the ratio of RCOOH in the first component to M1M2CO3 in the second component is (1-1.2):1. In both M1 and M2, H is not equal to H. +When the molar ratio of RCOOH in the first component to M1M2CO3 in the second component is (2-2.4):1 (e.g., 2:1, 2.01:1, 2.02:1, 2.03:1, 2.04:1, 2.05:1, 2.06:1, 2.07:1, 2.08:1, 2.09:1, 2.1:1, 2.11:1, 2.12:1, 2.13:1, 2.14:1, 2.15:1, 2.16:1, 2.1...), the ratio of RCOOH in the first component to M1M2CO3 in the second component is (2-2.4):1 (e.g., 2:1, 2.11:1, 2.12:1, 2.13:1, 2.14:1, 2.15:1, 2.16:1, 2.1...). 7:1, 2.18:1, 2.19:1, 2.2:1, 2.21:1, 2.22:1, 2.23:1, 2.24:1, 2.25:1, 2.26:1, 2.27:1, 2.28:1, 2.29:1, 2.3:1, 2.31:1, 2.32:1, 2.33:1, 2.34:1, 2.35:1, 2.36:1, 2.37:1, 2.38:1, 2.39:1, or 2.4:1, etc.

[0006] In some alternative embodiments, the RCOOH comprises R1COOH and R2COOH; wherein R1 is selected from substituted or unsubstituted C 1-3 Alkyl group, R2 is selected from substituted or unsubstituted C2 groups. 4-6 alkyl.

[0007] In some alternative embodiments, the RCOOH comprises R1COOH and R2COOH in a weight ratio of 1:(1-1.5); for example, 1:1, 1:1.1, 1:1.11, 1:1.12, 1:1.13, 1:1.14, 1:1.15, 1:1.16, 1:1.17, 1:1.18, 1:1.19, 1:1.2, 1:1.21, 1:1.22, 1:1.23, 1:1.24, 1:1.25, 1:1.26, 1:1.27, 1:1.28, 1:1.29, 1:1.3, 1:1.4, or 1:1.5, etc.

[0008] In some alternative embodiments, the RCOOH comprises R1COOH and R2COOH in a weight ratio of 1:(1.1-1.3).

[0009] In some alternative implementations, R1 is selected from C 2-4 Alkyl groups; such as methyl, ethyl, or propyl (including n-propyl and isopropyl). In some alternative embodiments, R1 is selected from C1. 1-3 Straight-chain alkyl groups.

[0010] In some specific implementations, the R1COOH is selected from propionic acid (CAS No. 79-09-4).

[0011] In some alternative implementations, R2 is selected from C4-6 Alkyl groups; such as butyl, pentyl, or hexyl. In some alternative embodiments, R2 is selected from C10. 4-6 Straight-chain alkyl groups.

[0012] In some specific implementations, the R2COOH is selected from valeric acid (CAS No. 109-52-4).

[0013] In some alternative embodiments, neither M1 nor M2 in M1M2CO3 is H. + .

[0014] In some alternative embodiments, M1 and M2 in M1M2CO3 are each independently selected from Na. + or K + In some specific implementations, M1 and M2 in M1M2CO3 are both selected from K. + In some other specific embodiments, M1 and M2 in M1M2CO3 are both selected from Na. + (The M1M2CO3 mentioned is selected from Na2CO3).

[0015] In some alternative implementations, the first solvent includes water.

[0016] In some alternative embodiments, the second solvent includes water.

[0017] Secondly, this application provides the use of the reservoir modifier described in the first aspect in a carbon dioxide flooding system.

[0018] This application has the following beneficial effects: This application injects the first and second components into the formation, where the first and second components undergo a chemical reaction to produce CO2. This CO2, as a chemical flooding agent to enhance oil recovery, not only protects surface equipment and casing but also has a strong oil displacement capability. Detailed Implementation

[0019] This application discloses a reservoir modifier for carbon dioxide flooding systems and its uses. Those skilled in the art can refer to this document to appropriately modify process parameters to achieve the desired results. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this application. The methods and applications of this application have been described through preferred embodiments. Those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this application to realize and apply the technology of this application.

[0020] To make the objectives, technical solutions, and advantages of this application clearer, the implementation schemes of this application will be further described in detail below with reference to the embodiments.

[0021] Preparation Examples 1-8: The ingredient list of the reservoir modifiers in Examples 1-8 is shown in Table 1.

[0022] Table 1. Ingredients of reservoir modifiers in Preparation Examples 1-3:

[0023] The preparation method of the reservoir modification agent specifically includes the following steps: RCOOH is dissolved in the first solvent to obtain the first component; M1M2CO3 is dissolved in a second solvent to obtain a second component; The first and second components are mixed evenly to obtain the reservoir modifier.

[0024] Pour the first component (50g) and the second component (5g) into test tubes respectively, add n-decane (3g), heat the test tubes to 40℃, shake by hand for 2 minutes, and observe the emulsification of oil and water. Then place the oil-water emulsion at 40℃ and observe the demulsification of the oil-water emulsion. The time when the oil and water phases are completely separated and the interface is clear is the demulsification time.

[0025] Those skilled in the art should understand that the shorter the demulsification time, the easier it is for the formed emulsion to demulsify, and the smaller the impact of the reservoir modifier on subsequent demulsification.

[0026] The performance test results of the reservoir modifiers prepared in Examples 1-8 are shown in Table 2.

[0027] Table 2. Performance test results of reservoir modifiers prepared in Examples 1-8:

[0028] As can be seen from Table 2, this application injects the first component and the second component into the formation. The first component and the second component undergo a chemical reaction in the formation to produce CO2. This CO2 serves as a chemical flooding agent to enhance oil recovery and has good demulsification performance. Therefore, this application not only has the function of protecting surface equipment and casing, but also has a very strong oil displacement capability.

[0029] By comparing preparation examples 3 and 7-8, it can be seen that the demulsification performance of the reservoir modifier of this application can be significantly improved by using a combination of propionic acid and valeric acid in the first component.

[0030] By comparing preparation examples 1-6, it can be seen that as the weight ratio of propionic acid and valeric acid in the first component increases from 1:1 to 1:1.5, the demulsification performance of the reservoir modifier of this application "first increases and then decreases". The demulsification performance of the reservoir modifier of this application reaches the optimum when the weight ratio of propionic acid and valeric acid is 1:1.2. Example

[0031] RCOOH is dissolved in a first solvent to obtain the first component; M1M2CO3 is dissolved in a second solvent to obtain the second component; using a skid-mounted device, the first and second components are injected alternately. The first and second components react in the reservoir. The oil well is shut down and left to simmer for 12-24 hours. After the well is opened (the discharge from the well is observed; initially, the discharge is usually residual liquid, and normal oil production, self-flowing, and pumping are resumed once oil is seen; during normal production, the material is transferred from the gathering pipeline to the gathering station), water is directly injected. There are no extra steps, thereby increasing reservoir pressure, stabilizing the formation clay, improving oil displacement efficiency, and increasing oil well production.

[0032] The above provides a detailed description of a reservoir modifier for a carbon dioxide flooding system and its applications. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of these embodiments are merely for the purpose of helping to understand the method and core ideas of this application. It should be noted that those skilled in the art can make various improvements and modifications to this application without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this application.

Claims

1. A reservoir modifier for use in carbon dioxide flooding systems, characterized in that, The reservoir modification agent comprises a first component and a second component; The first component comprises RCOOH and a first solvent; R is selected from substituted or unsubstituted C. 1-6 alkyl; The second component comprises M1M2CO3 and a second solvent; M1 and M2 are each independently selected from Li + Na + K + or H + And at least one of M1 and M2 is not H + ; H is one of M1 and M2. + The other one is not H + At that time, the molar ratio of RCOOH in the first component to M1M2CO3 in the second component was (1-1.2):1; In both M1 and M2, H is not equal to H. + At that time, the molar ratio of RCOOH in the first component and M1M2CO3 in the second component was (2-2.4):

1.

2. The reservoir modifier according to claim 1, characterized in that, The RCOOH comprises R1COOH and R2COOH; wherein R1 is selected from substituted or unsubstituted C. 1-3 Alkyl group, R2 is selected from substituted or unsubstituted C2 groups. 4-6 alkyl.

3. The reservoir modifier according to claim 2, characterized in that, The RCOOH comprises R1COOH and R2COOH in a weight ratio of 1:(1-1.5).

4. The reservoir modifier according to claim 3, characterized in that, The RCOOH comprises R1COOH and R2COOH in a weight ratio of 1:(1.1-1.3).

5. The reservoir modifier according to any one of claims 1 to 4, characterized in that, R1 is selected from C 1-3 alkyl.

6. The reservoir modifier according to claim 5, characterized in that, The R1COOH is selected from propionic acid.

7. The reservoir modifier according to any one of claims 1 to 4, characterized in that, R2 is selected from C 4-6 alkyl.

8. The reservoir modifier according to claim 7, characterized in that, The R2COOH is selected from valeric acid.

9. The reservoir modifier according to claim 1, characterized in that, In the M1M2CO3, neither M1 nor M2 is H. + .

10. The use of the reservoir modifier according to claims 1 to 9 in a carbon dioxide flooding system.

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