Preparation method of temperature-resistant, salt-resistant and oil-resistant foaming agent for low-permeability reservoir

Abstract

The invention discloses a temperature-resistant, salt-resistant and oil-resistant foaming agent for thermal recovery of heavy oil in a low-permeability reservoir and a preparation method thereof, and the foaming agent comprises the following components in percentage by mass: 0.12-0.5% of anionic and nonionic surfactants, 0.1-3% of zwitterionic surfactants, 0.1-5% of foam stabilizers, 3-5% of inorganic salt and auxiliaries, and the balance of water. The foaming agent provided by the invention adopts a mixture of an anionic surfactant and a zwitterionic surfactant, so that the foaming agent has good temperature resistance and salt resistance, has good migration and stabilization capabilities in oil, can be used for low-permeability reservoir balanced inter-well displacement, and improves the water flooding recovery efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of oil reservoirs, and in particular relates to a low-permeability oil reservoir temperature-resistant, salt-resistant and oil-resistant foaming agent and a preparation method thereof. Background Art

[0002] In the thermal development of low-permeability heavy oil reservoirs, due to the influence of factors such as heterogeneity between and within the reservoir layers and gravity differentiation, during the steam stimulation process, the injected high-temperature steam tends to rise to the top of the reservoir, forming steam overlap and crossflow in large pores and high permeability layers, reducing the steam utilization rate and volume sweep coefficient, resulting in uneven steam absorption profiles. At the same time, due to the influence of the interface characteristics of the rock, crude oil, and water system, a large part of the heavy oil cannot be stripped from the rock surface simply by relying on thermal effects. In addition, factors such as complex water environment and thin interlayer reservoirs have also affected the development effect of conventional steam stimulation to a certain extent. The use of heat-resistant, salt-resistant, and oil-resistant foaming agents for suction profile adjustment and anti-channeling technology is the mainstream technology currently used, with the advantages of less reservoir damage, good temperature resistance, selective plugging, and simple process.

[0003] At present, a large number of foam flooding field tests have been carried out in China, and significant effects of increasing oil production and controlling water have been achieved. However, due to the harsh reservoir conditions, the foam flooding oil production effect in some mines is low, and even gas channeling occurs. For example, low permeability reservoirs have very high capillary pressures, which make the foam liquid film easy to rupture (Yang Xingli, 2018), and high-temperature and high-salt reservoirs reduce the activity of chemical reagents and cannot form stable foams. For deep ordinary heavy oil reservoirs, not only does the foam need to adapt to the harsh reservoir environment of high temperature (101°C) and high salt (6000mg / L), but it also requires the foam to have a higher viscosity to achieve fluidity control. Therefore, it is urgent to develop new foaming and foam stabilizing products, and to form foam fluids that can be used in a variety of production operations to meet the production needs of low-pressure permeability reservoirs. Summary of the invention

[0004] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0005] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0006] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a foaming agent that is resistant to temperature, salt and oil for low permeability oil reservoirs.

[0007] To solve the above technical problems, the present invention provides the following technical solution: a heat-resistant, salt-resistant and oil-resistant foaming agent for low-permeability oil reservoirs, characterized in that: the components of the foaming agent include, by mass fraction, 0.12% to 0.5% of anionic non-ionic surfactant, 0.1% to 3% of zwitterionic surfactant, 0.1% to 5% of foam stabilizer, 3% to 5% of inorganic salts and additives, and the rest is water.

[0008] As a preferred embodiment of the foaming agent of the present invention, the anionic nonionic surfactant is at least one of sodium fatty alcohol polyoxyethylene ether sulfate AES and sodium fatty alcohol polyoxyethylene ether carboxylate AEC.

[0009] As a preferred embodiment of the foaming agent of the present invention, the zwitterionic surfactant is at least one of cocamidopropyl betaine CAB, cocamidopropyl hydroxysulfobetaine CHSB and octadecyl hydroxysulfobetaine DHSB.

[0010] As a preferred embodiment of the foaming agent of the present invention, the foam stabilizer is at least one of partially hydrolyzed polyacrylamide HPAM and hydrophobic associating polymer PAAO-1.

[0011] As a preferred embodiment of the foaming agent of the present invention, the auxiliary agent is at least one of methanol, ethanol, dodecanol and tetradecanol.

[0012] Another object of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing a foaming agent that is resistant to heat, salt and oil in low permeability reservoirs, which is characterized by comprising:

[0013] Under high temperature and high pressure conditions, anionic nonionic surfactant, zwitterionic surfactant, stabilizer, auxiliary agent and water are stirred into a uniform single-phase liquid to obtain the temperature-resistant, salt-resistant and oil-resistant foaming agent for low-permeability oil reservoirs.

[0014] As a preferred embodiment of the preparation method of the present invention, the process is carried out under high temperature and high pressure conditions, wherein the high temperature and high pressure conditions are 101°C and 5.5MPa.

[0015] As a preferred embodiment of the preparation method of the present invention, the stirring is performed until a uniform single-phase liquid is obtained, wherein the stirring rate is 6000 r / min.

[0016] Another object of the present invention is to overcome the deficiencies in the prior art and provide a low permeability reservoir temperature-resistant, salt-resistant and oil-resistant foaming agent for use in thermal recovery of low permeability heavy oil reservoirs.

[0017] As a preferred solution of the application of the present invention, the foaming agent has good migration and stability capabilities in oil, and can be used for balanced inter-well displacement in low-permeability oil reservoirs to improve water drive recovery.

[0018] Beneficial effects of the present invention:

[0019] The present invention provides a heat-resistant, salt-resistant and oil-resistant foaming agent for heavy oil thermal use in low-permeability oil reservoirs and a preparation method thereof. Compared with the prior art, the foaming agent of the present invention adopts a mixture of anionic surfactants and zwitterionic surfactants, so that the foaming agent of the present invention has good temperature and salt resistance and good migration and stability capabilities in oil, and can be used for balanced inter-well displacement in low-permeability oil reservoirs to improve water drive recovery. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0021] Figure 1 It is a comparison chart of foam half-life in the examples.

[0022] Figure 2 It is a comparison chart of the comprehensive foam index in the embodiments.

[0023] Figure 3 These are the main instruments and supporting equipment for the parallel displacement experiment in Example 10.

[0024] Figure 4 This is the core model connection method in Example 10.

[0025] Figure 5 This is a comparison chart of foam volumes at different mineralization degrees in Example 11.

[0026] Figure 6 This is a comparison chart of foam half-lives at different salinities in Example 11.

[0027] Figure 7 This is a comparison chart of the permeability differences in Example 12. DETAILED DESCRIPTION

[0028] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0029] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0030] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0031] Example 1

[0032] This embodiment is a preparation of a heat-resistant, salt-resistant and oil-resistant foaming agent for heavy oil in low-permeability reservoirs, specifically:

[0033] 3 g of fatty alcohol polyoxyethylene ether sodium sulfate AES, 2.5 g of cocamidopropyl betaine CAB, 3 g of hydrolyzed polyacrylamide HPAM, 0.375 g of tetradecanol and water were added into the reactor in sequence, stirred at a speed of 6000 r / min for 2 min, and the temperature was controlled at 101°C to obtain a temperature-resistant, salt-resistant and oil-resistant foaming agent for heavy oil in low-permeability reservoirs.

[0034] In Examples 2 to 8, long-chain fatty alcohols were used as additives for the compound system. 0.015 wt % of dodecanol, tetradecanol and hexadecanol were added to the compound system (CHSB:AES 0.5:0.5, 0.12 wt %), respectively, to study the effects of different additive types and concentrations on the foam properties of the compound system. The preparation method was the same as that of Example 1, except that the component types and concentrations in the foaming agent compound system were different, as shown in Table 1.

[0035] The foam volume at different times was recorded, and the time when the foam volume dropped to half was the foam half-life, which was used as an indicator of foam stability.

[0036] The calculation method of the comprehensive foam index is shown in the following formula. This index reflects both the foaming ability and foam stability of the foaming agent.

[0037]

[0038] Wherein, FCI is the foam comprehensive index, mL·s; Vf is the foam volume, mL; t 1 / 2 is the bubble half-life, s.

[0039] Table 1

[0040]

[0041]

[0042] The half-life results of the experimental foam are as follows Figure 1 As shown, FCI Figure 2 As shown in Table 1 and Figure 1 , 2It can be seen that when the effective concentration is 0.1wt%, the foam performance of the compound system of the zwitterionic foaming agent and the anionic nonionic foaming agent is increased compared with the corresponding single agent, indicating that the foam performance is improved and enhanced by compounding two different types of foaming agents. In the compound system, the foam volume is the largest in 0.12wt% (HPAM+AES / AEC)+0.015% dodecanol, the foam half-life is the highest, and the comprehensive foam index is also the most preferred.

[0043] When the effective concentration is 0.1wt%, the foam performance of the compound system of zwitterionic foaming agent and anionic nonionic foaming agent is increased compared with the corresponding single agent, indicating that the foam performance is improved and enhanced by compounding two different types of foaming agents. In the compound system, the foam volume is the largest in 0.12wt% (HPAM+AES / AEC)+0.015% dodecanol, the foam half-life is the highest, and the comprehensive foam index is also the most preferred.

[0044] Comparative Example 1

[0045] The difference between this comparative example and Example 1 is that AES is replaced by AEC, and the remaining steps are the same as those in Example 1.

[0046] Comparative Example 2

[0047] The difference between this comparative example and Example 1 is that 3 g of fatty alcohol polyoxyethylene ether sodium sulfate AES and 2.5 g of cocamidopropyl betaine CAB are replaced with 5.5 g of AES, and the remaining steps are the same as in Example 1.

[0048] Comparative Example 3

[0049] The difference between this comparative example and Example 1 is that CAB is replaced by CHSB, and the remaining steps are the same as those in Example 1.

[0050] Comparative Example 4

[0051] The difference between this comparative example and Example 1 is that 3 g of fatty alcohol polyoxyethylene ether sodium sulfate AES and 2.5 g of cocamidopropyl betaine CAB are replaced with 5.5 g of CAB, and the remaining steps are the same as in Example 1.

[0052] The performance of the foaming agents prepared in Example 1 and Comparative Examples 1 to 4 was tested, and the results are shown in Table 2.

[0053] Table 2

[0054]

[0055] Example 9

[0056] The difference between this embodiment and embodiment 1 is that the temperature is replaced with 80° C., and the remaining steps are the same as those in embodiment 1.

[0057] Example 10

[0058] The difference between this embodiment and embodiment 1 is that the temperature is replaced with 120° C., and the remaining steps are the same as those in embodiment 1.

[0059] Comparative Example 5

[0060] The difference between this comparative example and Example 1 is that the temperature is replaced with 25° C., and the remaining steps are the same as those in Example 1.

[0061] Comparative Example 6

[0062] The difference between this comparative example and Example 1 is that the temperature is replaced with 150° C., and the remaining steps are the same as those in Example 1.

[0063] The performance of the foaming agents prepared in Examples 1, 9, 10 and Comparative Examples 5, 6 was tested, and the results are shown in Table 3.

[0064] Table 3

[0065] Foam volume (mL) Foam half-life (min) Example 1 232 17 Example 9 218 20 Example 10 245 15 Comparative Example 5 204 25 Comparative Example 6 235 13

[0066] Embodiment 11

[0067] During the water injection development process of oil fields, due to the influence of permeability heterogeneity, the high permeability layer in the oil layer absorbs a large amount of injected water (formation water), and the mineralization gradually decreases, while the medium and low permeability layers absorb less injected water (formation water) or have not even started, and the mineralization decreases slightly, and it may still be original formation water with high mineralization.

[0068] Since the original system (zwitterionic surfactant) and the compound system (zwitterionic / anionic nonionic surfactant) are both salt-resistant surfactants, they are less affected by electrolytes and have good salt resistance. Figure 5 , 6 As shown in the figure, when the mineralization is 20000 mg / L, the viscosity of the foaming liquid reaches a maximum value under this mineralization condition, resulting in the smallest foam volume of the compound system and the largest foam half-life. When the mineralization reaches 200000 mg / L, the foam half-life of the compound system is greater than 1600s, which still remains the highest, indicating that the salt resistance of the compound system is the strongest.

[0069] Example 12

[0070] This example is a foam flooding parallel double-tube foam flooding gas characteristics and oil displacement effect evaluation experiment conducted under the reservoir conditions of the X block foam test area, to study the influence of permeability difference on foam flooding gas characteristics and oil displacement effect. The main instruments and supporting equipment of the parallel displacement experiment are as follows: Figure 3 Specifically:

[0071] (1) Use a high-pressure automatic compaction device to fill cores with different permeability differences (average permeability is 20-105mD), calculate the porosity and permeability of the cores by water drive, and saturate with crude oil.

[0072] (2) The core model is Figure 4 Connect well and drive with water until there is no oil output and the comprehensive water content reaches 98%. Record the experimental data such as oil production and liquid production during the displacement process.

[0073] (3) After the water flooding is completed, foam flooding is carried out, and a foam generator is used to stir and foam to displace the parallel cores. The parameters of the composite foam system are: effective concentration 0.12wt% (HPAM+AES / AEC)+0.015% dodecanol, gas-liquid ratio 1:1, injection linear velocity 1m / d, and injection foam segment plug 0.5PV.

[0074] In the process of subsequent water flooding after foam flooding, the oil production, water production and liquid production of the high permeability pipe and the low permeability pipe are continuously recorded until the comprehensive water content of the two pipes reaches more than 98%. The final recovery degree is calculated and the production gas-oil ratio curve of the foam as a whole is drawn.

[0075] The results of foam flooding experiments using two systems of water flooding and a composite system of 0.12wt% (HPAM+AES / AEC)+0.015% dodecanol are as follows: Figure 7 As shown in the figure, the water drive recovery factor and the final recovery degree of foam drive both show a trend of decreasing with the increase of the formation permeability difference. For the water drive recovery degree curve of the composite system displacement experiment, within the range of permeability difference of 1 to 14.6, as the permeability difference increases, the water drive recovery degree decreases rapidly. It drops from 43.78% when the permeability difference is 1 to 29.12% when the permeability difference is 14.6. However, the permeability difference is about 15 percentage points higher than that of water drive.

[0076] When the permeability difference is in the range of 1 to 14.6, although the slow-buffering gas channeling characteristics of foam flooding begin to appear when the compound system is used, the foam can still effectively adjust and improve the water absorption profile. The foam flooding enhanced oil recovery value also reached 13.88%. However, when the permeability difference is too high, gas channeling and gas-liquid differentiation of "gas going through the gas path and liquid going through the liquid path" occur during the displacement experiment, resulting in a further decrease in the final recovery degree of foam flooding and the recovery value of foam flooding compared with water flooding, down to 9.6%, but the oil recovery effect of the compound system is still better than that of water flooding.

[0077] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the present invention.

Claims

1. A heat-resistant, salt-resistant and oil-resistant foaming agent for low-permeability oil reservoirs, characterized in that: Calculated by mass fraction, the components of the foaming agent include 0.12-0.5% of anionic nonionic surfactant, 0.1%-3% of zwitterionic surfactant, 0.1%-5% of foam stabilizer, 3%-5% of inorganic salt and auxiliary agent, and the rest is water.

2. The foaming agent according to claim 1, characterized in that: The anionic nonionic surfactant is at least one of sodium fatty alcohol polyoxyethylene ether sulfate AES and sodium fatty alcohol polyoxyethylene ether carboxylate AEC.

3. The foaming agent according to claim 1, characterized in that: The zwitterionic surfactant is at least one of cocamidopropyl betaine CAB, cocamidopropyl hydroxysulfobetaine CHSB, and octadecyl hydroxysulfobetaine DHSB.

4. The foaming agent according to claim 1, characterized in that: The foam stabilizer is at least one of partially hydrolyzed polyacrylamide HPAM and hydrophobic associating polymer PAAO-1.

5. The foaming agent according to claim 1, characterized in that: The auxiliary agent is at least one of methanol, ethanol, dodecanol and tetradecanol.

6. The method for preparing a heat-resistant, salt-resistant and oil-resistant foaming agent for low-permeability oil reservoirs according to any one of claims 1 to 5, characterized in that: include, Under high temperature and high pressure conditions, anionic nonionic surfactant, zwitterionic surfactant, stabilizer, auxiliary agent and water are stirred into a uniform single-phase liquid to obtain the temperature-resistant, salt-resistant and oil-resistant foaming agent for low-permeability oil reservoirs.

7. The preparation method according to claim 6, characterized in that: The process is carried out under high temperature and high pressure conditions, wherein the high temperature and high pressure conditions are 101° C. and 5.5 MPa.

8. The preparation method according to claim 6, characterized in that: The stirring is performed until a uniform single-phase liquid is obtained, wherein the stirring rate is 6000 r / min.

9. Use of the temperature-resistant, salt-resistant and oil-resistant foaming agent for low-permeability oil reservoirs as claimed in any one of claims 1 to 5 in thermal recovery development of low-permeability heavy oil reservoirs.

10. The use according to claim 9, characterized in that: The foaming agent has good migration and stability capabilities in oil, and can be used for balanced inter-well displacement in low-permeability oil reservoirs to improve water drive recovery.

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