A reservoir modification agent for carbon dioxide flooding systems and use thereof

Abstract

The application relates to the technical field of oil well carbon dioxide flooding, and particularly provides a reservoir reconstruction agent for a carbon dioxide flooding system and application thereof. The reservoir reconstruction 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 + . The first component and the second component are injected into a stratum, the first component and the second component chemically react in the stratum to generate CO2, the CO2 is used as a chemical oil displacement agent for enhanced oil recovery, not only has the effect of protecting ground equipment and casings, but also has extremely strong oil displacement capacity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil well carbon dioxide flooding, and specifically provides a reservoir modification agent for a carbon dioxide flooding system and application thereof. BACKGROUND

[0002] Oil well carbon dioxide flooding is an enhanced oil recovery technology that reduces the viscosity of crude oil and improves its flowability by injecting supercritical CO2. CO2 dissolves in crude oil under high pressure, weakening intermolecular forces and significantly reducing viscosity (by up to 80-90%), while expanding nearly 8 times in volume to generate expansion pressure to drive crude oil to the production well. Dissolved CO2 can also react with crude oil components to generate polar substances through esterification and cracking, improving rheological properties. In the porous medium of the reservoir, CO2 can achieve miscible displacement by reducing interfacial tension (as low as 0.1 mN / m), improving microscopic oil displacement efficiency. In addition, CO2 can be stored geologically after escaping, achieving carbon emission reduction, and having both economic and environmental benefits. The mechanism of oil well surfactant flooding is mainly based on its effect of reducing oil-water interfacial tension and improving wettability. The amphiphilic structure (hydrophilic group and hydrophobic chain) of surfactant molecules (such as anions and non-ions) adsorbs on the oil-water interface, significantly reducing the interfacial tension (which can be reduced to below 0.1 mN / m), weakening the adhesion of crude oil to the rock, and promoting the separation of crude oil from the pore surface. At the same time, surfactants change the wettability of the rock, making the rock surface tend to be hydrophilic, reducing the relative permeability of the oil phase, and driving the remaining oil to migrate to the production well. In addition, surfactants can emulsify crude oil to form microemulsions, optimizing displacement efficiency by reducing the mobility ratio.

[0003] During the construction process of oil well injection of supercritical CO2 flooding, the following problems are mainly faced: first, high-pressure injection leads to accelerated corrosion of the manifold and wellbore, which requires frequent maintenance or replacement of corrosion-resistant materials, increasing costs; second, the reaction of CO2 with formation water generates carbonic acid, which easily causes fouling in the near-wellbore zone, blocking pore channels; third, the injection profile is not balanced, CO2 has a higher mobility than crude oil, which easily causes gas channeling, requiring additional profile control operations but with limited effect; fourth, deep reservoirs require a high-pressure environment, which may induce reservoir compaction or particle migration, reducing permeability; fifth, CO2-associated hydrocarbons in the produced gas need to be efficiently separated and recovered, which is a complex process with the risk of leakage; sixth, it is difficult to dynamically regulate construction parameters (such as injection rate and pressure), which need to be accurately matched with geological conditions to avoid ineffective displacement. In addition, the technology for real-time monitoring of CO2 distribution and reaction process is not yet perfect, affecting construction safety and efficiency. SUMMARY

[0004] In view of this, the present application provides a reservoir modification agent for carbon dioxide flooding system and its use. The present application injects a first component and a second component into a formation, the first component and the second component chemically react in the formation to produce CO2, which acts as a chemical flooding agent for enhanced oil recovery, not only having the effect of protecting surface equipment and casing, but also having a strong oil displacement capacity.

[0005] In a first aspect, the present application provides a reservoir modification agent for carbon dioxide flooding system, the reservoir modification agent comprising a first component and a second component;

[0006] The first component comprises RCOOH and a first solvent; R is selected from substituted or unsubstituted C 1-6 alkyl;

[0007] The second component comprises M1M2CO3 and a second solvent; M1and M2are each independently selected from Li + , Na + , K + or H + , and at least one of M1and M2is not H + ;

[0008] When one of M1and M2is H + , and the other is not H + , 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.);

[0009] When neither M1nor M2is H +In some embodiments, the molar ratio of RCOOH in the first component and M1M2C03 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, 2.17:1, 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.).

[0010] In some alternative embodiments, the RCOOH comprises R1COOH and R2COOH; wherein R1 is selected from a substituted or unsubstituted C 1-3 alkyl, and R2 is selected from a substituted or unsubstituted C 4-6 alkyl.

[0011] In other alternative embodiments, the RCOOH comprises R1COOH and R2COOH in a weight ratio of 1:(1-1.5); e.g., 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.

[0012] In other alternative embodiments, the RCOOH comprises R1COOH and R2COOH in a weight ratio of 1:(1.1-1.3).

[0013] In some alternative embodiments, R1 is selected from a C 2-4 alkyl; e.g., methyl, ethyl, or propyl (including n-propyl and isopropyl), etc. In other alternative embodiments, R1 is selected from a C 1-3 straight-chain alkyl.

[0014] In some particular embodiments, R1COOH is selected from propionic acid (CAS No. 79-09-4).

[0015] In some alternative embodiments, R2 is selected from a C4-6 alkyl; for example, butyl, pentyl, or hexyl, and the like. In other alternative embodiments, the R2is selected from the group consisting of C 4-6 linear alkyl.

[0016] In some specific embodiments, the R2COOH is selected from the group consisting of pentanoic acid (CAS No. 109-52-4).

[0017] In some alternative embodiments, the M1and M2in the M1M2CO3are not both H + .

[0018] In other alternative embodiments, the M1and M2in the M1M2CO3are each independently selected from the group consisting of Na + or K + In some specific embodiments, the M1and M2in the M1M2CO3are both selected from the group consisting of K + In other specific embodiments, the M1and M2in the M1M2CO3are both selected from the group consisting of Na + (the M1M2CO3is selected from Na2CO3).

[0019] In some alternative embodiments, the first solvent comprises water.

[0020] In some alternative embodiments, the second solvent comprises water.

[0021] In a second aspect, the present application provides use of the reservoir modification agent of the first aspect in a carbon dioxide flooding system.

[0022] The present application has the following beneficial effects:

[0023] The present application injects the first component and the second component into the formation, and the first component and the second component chemically react in the formation to produce CO2, which is a chemical oil displacement agent for enhanced oil recovery. The CO2 not only has the effect of protecting the surface equipment and the casing, but also has a strong oil displacement capacity. DETAILED DESCRIPTION

[0024] The present application discloses a reservoir modification agent for a carbon dioxide flooding system and use thereof, and those skilled in the art can refer to the content herein to appropriately improve the process parameters for implementation. It is particularly pointed out that all similar replacements and changes are obvious to those skilled in the art, and they are all regarded as included in the present application. The method and application of the present application have been described by the preferred embodiments, and the relevant personnel can obviously make changes or appropriate changes and combinations to the method and application described herein without departing from the content, spirit and scope of the present application, to realize and apply the technology of the present application.

[0025] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further described in detail below with examples.

[0026] Preparation 1-8:

[0027] The ingredient table of the reservoir reconstruction agent in Preparation Example 1-8 is shown in Table 1.

[0028] Table 1, ingredient table of the reservoir reconstruction agent in Preparation Example 1-3:

[0029]

[0030] The preparation method of the reservoir reconstruction agent specifically comprises the following steps:

[0031] dissolving RCOOH in the first solvent to obtain a first component;

[0032] dissolving M1M2CO3 in the second solvent to obtain a second component;

[0033] mixing the first component and the second component uniformly to obtain the reservoir reconstruction agent.

[0034] The first component (50 g) and the second component (5 g) are respectively poured into a test tube, n-decane (3 g) is added, the test tube is heated to 40℃, and the test tube is shaken by hand for 2 minutes, it is found that the oil and water are emulsified, then the oil-water emulsion is placed at 40℃, and the demulsification condition of the oil-water emulsion is observed, the time when the oil and water two phases are completely separated and the interface is clear is the demulsification time.

[0035] It should be understood by those skilled in the art that the shorter the demulsification time is, the more easily the emulsion is broken, and the smaller the influence of the reservoir reconstruction agent on subsequent demulsification is.

[0036] The performance detection results of the reservoir reconstruction agents of Preparation Examples 1-8 are shown in Table 2.

[0037] Table 2, performance detection results of the reservoir reconstruction agents of Preparation Examples 1-8:

[0038]

[0039] It can be seen from Table 2 that the first component and the second component are injected into the formation, the first component and the second component react chemically in the formation to produce CO2, the CO2 is used as a chemical oil displacement agent for enhanced oil recovery, and the demulsification performance is good, therefore, the present application not only has the effect of protecting the ground equipment and the casing, but also has a strong oil displacement capacity.

[0040] It can be known by comparing Preparation Example 3 and Preparation Examples 7-8 that by using the combination of propionic acid and valeric acid in the first component, the demulsification performance of the reservoir reconstruction agent of the present application can be significantly improved.

[0041] As can be seen by comparing Preparation Examples 1-6, with the weight ratio of propionic acid and valeric acid in the first component changing from 1:1 to 1:1.5, the demulsification performance of the reservoir modification agent of the application "first increases and then decreases", wherein when the weight ratio of propionic acid and valeric acid is 1:1.2, the demulsification performance of the reservoir modification agent of the application reaches the optimum. Embodiment

[0042] The RCOOH is dissolved in the first solvent to obtain the first component; the M1M2CO3 is dissolved in the second solvent to obtain the second component; the first component and the second component are separately injected at intervals by using a skid-mounted device, the first component and the second component react in the reservoir, the oil well is closed for 12-24 hours, and then opened (after the well is opened, the condition of the discharge of the oil well is observed, generally the residual liquid is injected at the beginning of spraying, and after oil is seen, normal oil production, self-spraying and oil pumping are restored, and the object is transported from the oil gathering pipeline to the oil gathering station during normal production), the water well is directly injected, and there is no extra process, thereby improving the reservoir pressure, stabilizing the formation clay, improving the oil displacement efficiency, and improving the oil well production.

[0043] The above describes in detail the reservoir modification agent for the carbon dioxide oil displacement system and the use thereof. The principles and implementation modes of the application are described by using specific examples, and the above description of the embodiments is only used to help understand the method and the core idea of the application. It should be pointed out that for those skilled in the art, without departing from the principles of the application, the application can be improved and modified in several ways, and these improvements and modifications also fall within the protection scope of the claims of the 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; the RCOOH comprises R1COOH and R2COOH in a weight ratio of 1:(1-1.5), wherein the R1COOH is selected from propionic acid and the R2COOH is selected from valeric acid; The second component comprises M1M2CO3 and a second solvent; both M1 and M2 are selected from Na. + ; The molar ratio of RCOOH in the first component to M1M2CO3 in the second component is (2-2.4):

1.

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

3. The use of the reservoir modifier according to any one of claims 1 to 2 in a carbon dioxide flooding system.

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