A salt-sensitive reservoir protection system and a preparation method and application thereof

Abstract

The application discloses a salt-sensitive reservoir protection system and a preparation method and application thereof. The protection system comprises the following component raw materials in percentage by mass: an anti-swelling agent 1-3%, a scale inhibitor 1-2%, a solubilizing agent 0.3-0.6%, and the balance being water; wherein the anti-swelling agent is oligomeric quaternary ammonium salt DETA-FP; the scale inhibitor is EDTA; and the solubilizing agent is alkyl glucoside APG. The salt-sensitive reservoir protection system has an anti-swelling rate of 93%, a scale inhibition rate of 81.3%, and an oil washing rate of 95.6% in indoor evaluation. When the protection system is applied in field injection, after 2% of the protection system is added into a front section of a water injection well, the apparent water injection index of clear water injection into a formation is obviously increased, and the formation water injection starting pressure is reduced by 2.7 MPa. The salt-sensitive reservoir protection system is suitable for a salt-sensitive reservoir water injection well with a temperature of 150 DEG C or lower and a salinity of 220000 mg / L or lower.

Description

Technical Field

[0001] This invention relates to a salt-sensitive reservoir protection system, its preparation method, and its application. Background Technology

[0002] The Xinghua Block of the Bayan Oilfield serves as a potential replacement area for increasing reserves and production in the North China Oilfield. This block is a high-temperature, high-salinity oil reservoir with a reservoir temperature of 150℃ and a formation water salinity of 8×10⁻⁶. 4 mg / L~22×10 4 The crude oil concentration is mg / L, exhibiting a strong tendency for self-scaling. The wax content is 19.4%, the gum content is 27.2%, and the freezing point is 50℃. The main producing layer in this block is the Linhe Formation reservoir, which typically exhibits strong water sensitivity and extremely strong salt sensitivity. Because the oilfield is in its early development stage, the produced fluid from the wells cannot meet the water injection requirements. To supplement formation energy, other water sources need to be injected into the formation. However, the injection of external water can easily cause reservoir damage.

[0003] Currently, commonly used reservoir protectants for water injection wells include high-polymer anti-swelling agents, inorganic salt KCl, and surfactants. However, these protectants are difficult to maintain at 150℃ and 22×10⁻⁶ ℃. 4 Used under conditions of mg / L mineralization.

[0004] Patent CN106281288A discloses a pressure-reducing and injection-enhancing agent for water injection wells in low-permeability reservoirs. It utilizes a compound of fluorocarbon surfactants, alkyl ammonium chloride, and fatty alcohol polyoxyethylene ether to form an anti-swelling main agent, with sodium ethylenediaminetetramethylene phosphate as a slow-release scale inhibitor and dimethyl ketoxime as a bactericide. However, this pressure-reducing and injection-enhancing agent is not suitable for high-temperature reservoirs. Patent CN109913193A discloses a pressure-reducing and injection-enhancing agent for water injection wells in low-permeability reservoirs, employing a compound of dehydrogenated rosin-based anionic surfactants and cationic surfactants to form an anti-swelling main agent. Betaine amphoteric surfactants and cetyl alcohol, as rock wetting agents, mainly utilize the wetting effect of surfactants on rock surfaces to reduce water injection resistance, but they have no inhibitory effect on formation fluid scaling. Patent CN111117586A discloses a pressure-reducing and injection-enhancing active system with reservoir protection properties and high-temperature and salt resistance. It uses cationic surfactant alkyl quaternary ammonium salts to reduce interfacial tension, organic anti-swelling agents such as polyurethane ethers to reduce clay hydration swelling, and scale inhibitors to reduce scale formation in injected water. This pressure-reducing and injection-enhancing active system is only suitable for 120℃ and 20×10⁻⁶ conditions. 4 For water injection wells with a concentration of mg / L, the temperature and salt resistance still need to be improved. Summary of the Invention

[0005] To at least partially address the aforementioned technical problems in the prior art, embodiments of the present invention provide a salt-sensitive reservoir protection system, its preparation method, and its application, suitable for use at 150℃ and 22×10⁻⁶ ℃. 4 Conditions for mg / L mineralization.

[0006] As one aspect of the present invention, a salt-sensitive reservoir protection system is provided, the protection system comprising, by mass percentage: 1-3% anti-swelling agent, 1-2% scale inhibitor, 0.3-0.6% solubilizer, and the balance being water;

[0007] The anti-swelling agent is the oligomeric quaternary ammonium salt DETA-FP; the scale inhibitor is EDTA; and the solubilizer is alkyl glucoside APG.

[0008] In one or more possible embodiments, the oligomeric quaternary ammonium salt DETA-FP is a mixture of dimeric quaternary ammonium salt DETA-FP2 and tetrameric quaternary ammonium salt DETA-FP4 in any mass ratio.

[0009] In one or more possible embodiments, according to claim 2, the salt-sensitive reservoir protection system is characterized in that the mass ratio of the diquaternary ammonium salt DETA-FP2 to the tetraquaternary ammonium salt DETA-FP4 is 1:(1~2).

[0010] In one or more possible embodiments, the dimeric quaternary ammonium salt DETA-FP2 is as shown in formula (I):

[0011] (I);

[0012] The tetrameric quaternary ammonium salt DETA-FP4 is as shown in formula (II):

[0013] (II).

[0014] In one or more possible embodiments, the alkyl glucoside APG is selected from C10-C12 alkyl glucosides.

[0015] In one or more possible embodiments, the salt-sensitive reservoir protection system is suitable for water injection wells in salt-sensitive reservoirs with temperatures ≤150℃ and salinity ≤220000mg / L.

[0016] As another aspect of the present invention, a method for preparing the above-mentioned salt-sensitive reservoir protection system is provided, the method comprising:

[0017] According to the formula, oligoquaternary ammonium salt is added to water under stirring conditions. After dissolving, EDTA is added to the solution and stirred until dissolved. Then, alkyl glucoside is added to obtain a salt-sensitive reservoir protection system.

[0018] In one or more possible embodiments, the preparation of the oligomeric quaternary ammonium salt includes:

[0019] Add 2,3-epoxypropyltrimethylammonium chloride to water, stir until dissolved, heat to a certain temperature, add hydrochloric acid dropwise, and mix to react; then add the reacted liquid dropwise to diethylenetriamine, stir at a constant temperature for a certain time, cool, extract, and distill the aqueous phase under reduced pressure to obtain oligomeric quaternary ammonium salt.

[0020] As another aspect of the present invention, the application of the above-mentioned salt-sensitive reservoir protection system in oilfield development is involved.

[0021] As another aspect of the present invention, a method for oilfield exploitation is provided, characterized in that the method uses the above-mentioned salt-sensitive reservoir protection system, comprising:

[0022] Inject 2-3 wt% of salt-sensitive reservoir protection system slugs;

[0023] Betting suspended for 3-5 days;

[0024] Water injection section plug.

[0025] The beneficial effects of the above-mentioned technical solutions provided in the embodiments of this application include at least the following:

[0026] The reservoir protection system of this invention, by synthesizing oligomeric quaternary ammonium salts as anti-swelling agents, EDTA as scale inhibitors, and alkyl glucosides as solubilizers, enables the protection system of this invention to effectively inhibit clay hydration and swelling under high temperature and high salinity environments when applied to water injection wells, and also to react with Ca... 2+ Mg 2+ The metal ions form chelated five-membered rings, resulting in a maximum temperature resistance of 150°C. Furthermore, the reservoir protection system of this invention exhibits excellent solubility limiting effects, not only reducing the adverse effects of inorganic scale produced by external fluids on the reservoir, but also reducing the blockage effects of crude oil, colloids, asphalt, and other particles in the reservoir channels.

[0027] In indoor evaluation, the anti-soil-sensitive reservoir protection system of the present invention showed an anti-swelling rate of 93%, a scale inhibition rate of 81.3%, and an oil washing rate of 95.6%. In field trial injection, after adding 2% of the protection system to the pre-injection stage, the apparent water absorption index of the injected water significantly increased, and the formation water injection start-up pressure decreased by 2.7 MPa.

[0028] The salt-sensitive reservoir protection system of the present invention is applicable to water injection wells in salt-sensitive reservoirs with a temperature ≤150℃ and a salinity ≤220000mg / L.

[0029] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained in accordance with the structures particularly pointed out in the description, claims and drawings. Attached Figure Description

[0030] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0031] Figure 1 This is a graph showing the variation of core permeability with different displacement media in Example 2 of the present invention.

[0032] Figure 2 This is a water absorption indicator curve from the injection test of Embodiment 2 of the present invention. Detailed Implementation

[0033] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0034] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0035] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0036] In the description of this invention, it should be noted that the terms "comprising", "including", "having", "containing", etc., are all open-ended terms, meaning that they include but are not limited to.

[0037] The present invention will be further described below with reference to specific embodiments. The scope of protection of the present invention is not limited by the following embodiments. The main materials involved in the embodiments or preparation examples are all commercially available industrial-grade products.

[0038] The oligomeric quaternary ammonium salts used in the following examples were all prepared by the following steps.

[0039] Preparation Example 1

[0040] This preparation example provides a method for preparing the diquaternary ammonium salt DETA-FP2, including the following steps:

[0041] (1) Add 50g of 2,3-epoxypropyltrimethylammonium chloride and 50ml of water to a three-necked flask, stir until dissolved, heat to 50℃, then add 165.5ml of 2mol / L hydrochloric acid, stir for 60min to obtain the product;

[0042] (2) Add 16.98g of diethylenetriamine to a three-necked flask, heat to 70°C, and slowly add the product from step (1) while stirring magnetically. Stir at a constant temperature for 8 hours to obtain a brown liquid. After cooling to room temperature, add toluene, glycerol and water for extraction, retain the aqueous phase, and distill under reduced pressure at 150°C to obtain a white solid, which is the diquaternary ammonium salt DETA-FP2.

[0043] The relative molecular mass of the diquaternary ammonium salt DETA-FP2 synthesized in this preparation example is 335.

[0044] Preparation Example 2

[0045] This preparation example provides a method for preparing the tetrameric quaternary ammonium salt DETA-FP4, including:

[0046] (1) Add 50g of 2,3-epoxypropyltrimethylammonium chloride and 50ml of water to a three-necked flask, stir until dissolved, heat to 50℃, then add 165.5ml of 2mol / L hydrochloric acid, stir for 60min to obtain the product;

[0047] (2) Add 8.49 g of diethylenetriamine to a three-necked flask, heat to 70°C, and slowly add the product from step (1) while stirring magnetically. Stir at a constant temperature for 8 hours to obtain a brown liquid. After cooling to room temperature, add toluene, glycerol and water for extraction, retain the aqueous phase, and distill under reduced pressure at 150°C to obtain a white solid, which is tetrameric quaternary ammonium salt DETA-FP4.

[0048] The tetrameric quaternary ammonium salt DETA-FP4 synthesized in this preparation example has a relative molecular mass of 567.

[0049] The following are embodiments of the present invention. The oligomeric quaternary ammonium salts used in the embodiments are all selected from the above preparation examples. Examples 1 and 2 respectively provide a salt-sensitive reservoir protection system.

[0050] Example 1

[0051] The salt-sensitive reservoir protection system GCYFP-C in this embodiment is prepared through the following steps:

[0052] At room temperature, add 1.5g each of diquaternary ammonium salt DETA-FP2 and tetraquaternary ammonium salt DETA-FP4 to 100g of water, stir to dissolve, add 2g of EDTA, continue stirring to dissolve, and then slowly add 0.6g of dodecyl glucoside. The resulting light yellow liquid is the salt-sensitive reservoir protection system GCYFP-C.

[0053] High-temperature anti-swelling treatment was performed on the salt-sensitive reservoir protection system GCYFP-C prepared in Example 1.

[0054] Sexual tests, specifically including:

[0055] The experimental temperature was set at 90℃, and the bentonite soaking time was 12 hours. The anti-swelling rate was evaluated using a centrifugation test method according to SY / T 5971-2016, "Performance Evaluation Method of Clay Stabilizers for Fracturing, Acidizing, and Water Injection in Oil and Gas Fields". Furthermore, three commonly used water injection well protective agents were compared with the salt-sensitive reservoir protection system GCYFP-C prepared in Example 1 of this invention. The test results are recorded in Table 1 below.

[0056] Table 1 Test data on the anti-swelling effect of different types of protection systems

[0057]

[0058] The test results in Table 1 show that the salt-sensitive reservoir protection system prepared in Example 1 of this invention exhibits superior anti-swelling effects compared to conventional protective agent systems on the market, at 90°C and a concentration range of 1-3%. This demonstrates that the salt-sensitive reservoir protection system prepared in this invention possesses excellent anti-swelling properties.

[0059] Example 2

[0060] The salt-sensitive reservoir protection system GCYFP-C in this embodiment is prepared through the following steps:

[0061] Add 5g of anti-swelling agent DETA-FP2 and 10g of anti-swelling agent DETA-FP4 to 500g of water, stir to dissolve, then add 10g of EDTA, and continue stirring before adding 1.5g of dodecyl glucoside APG to obtain a light yellow liquid anti-salt-sensitive reservoir protection system.

[0062] The salt-sensitive reservoir protection system prepared in this embodiment has the following properties: pH value of 6 and density of 1.12 g / cm³. 3 It is miscible with water without precipitation and has a viscosity of 1.2 mPa·s.

[0063] The performance of the salt-sensitive reservoir protection system prepared in Example 2 was tested as follows.

[0064] Test 1: Evaluation of Erosion Resistance

[0065] This test references the static evaluation method in Q / SH 0053-2010 "Technical Requirements for Clay Stabilizers" and designs a dynamic scour resistance evaluation method for the reservoir protection system: Formation water (mineralization 190,000 mg / L), a 2% GCYFP-C solution prepared with clean water, and clean water (mineralization 700 mg / L) are poured into parallel intermediate containers ①, ②, and ③, respectively. The constant flow pump is set to a flow rate of 0.2 ml / min, and the core holder temperature is 90℃. An alternating injection method of the reservoir protection system and clean water is adopted, and the changes in core permeability are observed. The results are as follows: Figure 1 As shown.

[0066] Test results: (Refer to) Figure 1 The core permeability variation curves with different displacement media are shown in the figure. From the alternating injection, the core permeability changes as follows: after injecting 2% GCYFP-C slugs, when the volume of the first water flush is approximately 20 times the volume of the reservoir protection system, the core permeability decreases by 30%; when the volume of the second water flush is approximately 8 times the volume of the reservoir protection system, the core permeability decreases by 30%. Therefore, the inventors believe that the salt-sensitive reservoir protection system GCYFP-C prepared in this invention exhibits good erosion resistance.

[0067] Test 2: Scale Inhibition Performance Evaluation Test

[0068] Referring to the performance evaluation method of slow-release scale inhibitors for oilfield use in Q / SY17126-2019, the scale inhibition rate of the salt-sensitive reservoir protection system prepared in Example 2 was tested. Formation water from a certain block with a salinity of 67000 mg / L, containing Ca... 2+ Concentration 21870 mg / L, HCO3 - With a concentration of 172.4 mg / L and a free CO2 concentration of 12.4 mg / L, it is a CaCl2 water type and has a strong tendency to form CaCO3 scale. The scale inhibition effect of oilfield slow-release scale inhibitor HZ-3 was compared, and the results are shown in Table 2.

[0069] Table 2. Scale inhibition test data of different types of protective agent systems

[0070]

[0071] Test results: As shown in Table 2, the scale inhibition performance of the agent decreased with increasing temperature. However, the scale inhibition performance of the developed reservoir protection system GCYFP-C reached 84.5% at a high temperature of 120℃, which is better than that of the commonly used slow-release scale inhibitor HZ-3.

[0072] Test of three-wash oil performance evaluation test

[0073] Referring to the method for evaluating the oil-washing performance of surfactants in Q / SY17583-2018, the oil-washing rate of the salt-sensitive reservoir protection system prepared in Example 2 was tested. Crude oil from a certain block, with a wax content of 19.4%, a gum content of 27.2%, and a pour point of 50℃, was used. The oil-washing rate of different concentrations of GCYFP-C was tested at an experimental temperature of 40℃, and the results are shown in Table 3.

[0074] Table 3. Scale inhibition test data of different types of protective agent systems

[0075] Test results: As shown in Table 3, the developed reservoir protection system GCYFP-C has excellent oil washing performance in the concentration range of 0.3% to 0.6%, and can effectively reduce the cold damage caused by the entry of external low-temperature liquid into the reservoir during water injection.

[0076] Test of the effect of four water injections

[0077] The salt-sensitive reservoir protection system GCYFP-C prepared in Example 2 was applied to a salt-sensitive reservoir field with a reservoir temperature of 150℃, a salinity of 220,000 mg / L, and a critical salinity of 50,000 mg / L. The water injection effect of the GCYFP-C reservoir protection system was tested. Specifically, a clean water injection test was conducted in a water injection well. 1100 cubic meters of 2% reservoir protection system solution were injected during the initial stage of increasing the flow rate, followed by the injection of 6000 cubic meters of clean water. The test results are as follows: Figure 2 As shown.

[0078] Test results: (Refer to) Figure 2 The water absorption indicator curve shown in the test injection diagram reveals that by injecting the reservoir protection system during the increasing discharge phase, the apparent water absorption index measured during the decreasing discharge phase significantly increases, the formation water injection start-up pressure decreases by 2.7 MPa, and the injection pressure stabilizes in the later stages of the test, indicating the test was successful. This demonstrates that the salt-sensitive reservoir protection system prepared in this invention achieves good pressure reduction and increased injection effects during mine construction.

[0079] In summary, the salt-sensitive reservoir protection system of the present invention has excellent comprehensive performance, with an anti-swelling rate of up to 93%, a scale inhibition rate of no less than 81.3%, and an oil washing rate of 95.6%. During field trial injection, after adding 2% of the agent in the pre-injection stage, the apparent water absorption index of the injected water in the formation increased significantly, and the formation water injection start-up pressure decreased by 2.7 MPa.

[0080] Although the invention has been described in considerable detail and particularly with regard to several of the described embodiments, it is not intended to limit itself to any of these details or embodiments or any particular embodiment, thereby effectively covering the intended scope of the invention. Furthermore, the invention has been described above with respect to embodiments foreseeable by the inventors in order to provide a useful description, and non-substantial modifications to the invention that have not yet been foreseen may still represent equivalent modifications.

[0081] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0082] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A salt-sensitive reservoir protection system, characterized in that, The protection system comprises, by mass percentage, the following raw materials: 1-3% anti-swelling agent, 1-2% scale inhibitor, 0.3-0.6% solubilizer, and the balance being water; The anti-swelling agent is oligomeric quaternary ammonium salt DETA-FP; the scale inhibitor is EDTA; and the solubilizer is alkyl glucoside APG. The oligomeric quaternary ammonium salt DETA-FP is a mixture of dimeric quaternary ammonium salt DETA-FP2 and tetrameric quaternary ammonium salt DETA-FP4; wherein the mass ratio of the dimeric quaternary ammonium salt DETA-FP2 to the tetrameric quaternary ammonium salt DETA-FP4 is 1:(1~2). The dimerized quaternary ammonium salt DETA-FP2 is as shown in formula (I): （Ⅰ）； The tetrameric quaternary ammonium salt DETA-FP4 is as shown in formula (II): （Ⅱ）。 2. The salt-sensitive reservoir protection system according to claim 1, characterized in that, The alkyl glucosinolate APG is selected from C10-C12 alkyl glucosinolates.

3. The salt-sensitive reservoir protection system according to claim 1, characterized in that, The salt-sensitive reservoir protection system is suitable for water injection wells in salt-sensitive reservoirs with temperatures ≤150℃ and salinity ≤220000mg / L.

4. A method for preparing a salt-sensitive reservoir protection system as described in any one of claims 1 to 3, characterized in that, The method includes: According to the formula, oligoquaternary ammonium salt is added to water under stirring conditions. After dissolving, EDTA is added to the solution and stirred until dissolved. Then, alkyl glucoside is added to obtain a salt-sensitive reservoir protection system.

5. The method for preparing the salt-sensitive reservoir protection system according to claim 4, characterized in that, The preparation of the oligomeric quaternary ammonium salt includes: Add 2,3-epoxypropyltrimethylammonium chloride to water, stir until dissolved, heat to a certain temperature, add hydrochloric acid dropwise, and mix to react; then add the reacted liquid dropwise to diethylenetriamine, stir at a constant temperature for a certain time, cool, extract, and distill the aqueous phase under reduced pressure to obtain oligomeric quaternary ammonium salt.

6. The application of the salt-sensitive reservoir protection system as described in any one of claims 1 to 3 in oilfield development.

7. A method for oilfield extraction, characterized in that, The method uses the salt-sensitive reservoir protection system as described in any one of claims 1 to 3, comprising: Inject 2-3 wt% of salt-sensitive reservoir protection system slugs; Betting suspended for 3-5 days; Water injection section plug.

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