Foamed acid plugging removal system and preparation method thereof

Abstract

The application relates to the technical field of plugging removing agents for oilfield recovery, in particular to a foamed acid plugging removing system and a preparation method thereof. The foamed acid plugging removing system comprises a foamed acid component, a foaming agent and a gas phase component, and the foamed acid component comprises, in mass ratio, oxalic acid, phosphoric acid, triethanolamine, dimethyl diallyl ammonium chloride, acetic acid, disodium phosphate and sodium nitrite in a mass ratio of (10-12):(3-5):4:2:(1.5-2.5):0.05:0.05:1. The total weight m1 of the foamed acid component and the total weight m2 of the foaming agent satisfy the relationship m1:m2=100:(1.5-2.5). The volume V1 of the gas phase component and the total volume V2 of the foamed acid component satisfy the relationship V1:V2>=40:1. The foamed acid plugging removing system can improve the plugging removing effect of an acid plugging removing agent in a heterogeneous formation, so that the plugging material dissolution rate is above 65%, the dissolution rate is above 1.20g / (m 2 ·h), the foaming multiple is above 4.0, and the stable foaming time is above 420s.

Description

Technical Field

[0001] This application relates to the field of unblocking agents for oilfield recovery, and in particular to a foam acid unblocking system and its preparation method. Background Technology

[0002] After long-term production, oil wells are susceptible to intrusion of external fluids during the production process. In addition, mineral hydration of formation clay and deposition of heavy components may occur during production. These factors can contaminate the oil layer and cause blockage. Therefore, regular unblocking is an important technique to relieve damage to the near-wellbore oil layer.

[0003] However, the process of unblocking is often affected by the vertical heterogeneity of the oil reservoir and the development status. If conventional unblocking techniques are used, the problem of single-layer breakthrough will be aggravated, which will undoubtedly affect the effectiveness and specificity of the unblocking effect. Taking the Du66 fire-drive block as an example, this block is a typical thin interbedded reservoir with a total of 396 production wells. Among these production wells, 35% of the production wells experience the phenomenon of not being able to inject steam during the injection process. However, during the acid unblocking process, a "backflow" phenomenon occurs, which causes a large amount of unblocking agent to enter the lost circulation zone and high-permeability zone. As a result, the low-permeability zone cannot be effectively acidified, and it may even further increase the difference in physical properties between the low-permeability and high-permeability zones. In addition, conventional acid unblocking agents have the problems of fast reaction rate, small treatment radius, and large amount of acid slag generated. Under the influence of formation heterogeneity, acid unblocking agents will have fingering problems, which makes it impossible for the acid unblocking agent to be evenly distributed in the formation. As a result, the damaged well section cannot be effectively unblocked, affecting the effectiveness of the unblocking measures. Summary of the Invention

[0004] This application provides a foam acid unblocking system and its preparation method to solve the following technical problem: how to improve the unblocking efficiency of acidic unblocking agents in heterogeneous layers.

[0005] In a first aspect, this application provides a foam acid unblocking system, which includes a foam acid component, a foaming agent, and a gaseous component. The foam acid component includes oxalic acid, phosphoric acid, triethanolamine, dimethyl diallyl ammonium chloride, acetic acid, disodium phosphate, and sodium nitrite. The total weight m1 of the foam acid component and the total weight m2 of the foaming agent satisfy the following formula: m1:m2 = 100:(1.5~2.5). The volume V1 of the gaseous component and the total volume V2 of the foam acid component satisfy the following formula: V1:V2 ≥ 40:1.

[0006] The weights of oxalic acid (m3), phosphoric acid (m4), triethanolamine (m5), dimethyldiallylammonium chloride (m6), foaming agent (m2), acetic acid (m7), disodium phosphate (m8), and sodium nitrite (m9) satisfy the following relationship: m3:m4:m5:m6:m2:m7:m8:m9=(10~12):(3~5):4:2:(1.5~2.5):0.05:0.05:1.

[0007] Optionally, the foaming agent includes sodium dodecyl sulfate and / or cocamidopropyl betaine.

[0008] Optionally, when the foaming agent includes sodium dodecyl sulfate and cocamidopropyl betaine, the weight m11 of the sodium dodecyl sulfate and the weight m12 of the cocamidopropyl betaine satisfy the relationship: m11:m12=(20~30):(5~10).

[0009] Optionally, the gaseous components include nitrogen and / or carbon dioxide.

[0010] Secondly, this application provides a method for preparing the foam acid unblocking system described in the first aspect, the method comprising:

[0011] Oxalic acid, phosphoric acid, triethanolamine, dimethyldiallylammonium chloride and acetic acid are mixed to obtain crude foam acid component;

[0012] Preparation of foaming agents;

[0013] The foaming agent and the coarse foaming acid component are first stirred and mixed to obtain a first mixture;

[0014] Sodium disodium phosphate and sodium nitrite were added sequentially to the first mixture and stirred to obtain the liquid phase component.

[0015] The gas phase component and the liquid phase component are mixed at a preset flow rate ratio to obtain a foam acid unblocking system.

[0016] Optionally, the step of mixing oxalic acid, phosphoric acid, triethanolamine, dimethyldiallyl ammonium chloride, and acetic acid to obtain a crude foam acid component includes the following steps:

[0017] Oxalic acid and phosphoric acid are mixed again by stirring to obtain a second mixture;

[0018] Triethanolamine and the second mixture are then stirred and mixed in a third stirring process to obtain a third mixture.

[0019] Dimethyl diallyl ammonium chloride and the third mixture are subjected to a fourth stirring and mixing to obtain a fourth mixture.

[0020] Acetic acid and the fourth mixture are stirred and mixed in the fourth manner to obtain a crude foam acid component.

[0021] Optionally, the second stirring speed is 100 r / min to 150 r / min, and the second stirring time is 15 min to 20 min;

[0022] The third stirring speed is 150 r / min to 200 r / min, and the third stirring time is 20 min to 25 min;

[0023] The speed of the fourth stirring and mixing is 200 r / min to 250 r / min, and the time of the fourth stirring and mixing is 25 min to 30 min.

[0024] Optionally, the first stirring speed is 100 r / min to 150 r / min, and the first stirring time is 20 min to 25 min.

[0025] Optionally, the preset flow rate ratio is (500-800):(3-5).

[0026] Optionally, the preparation of the foaming agent includes the following steps:

[0027] Heat the water, then add sodium dodecyl sulfate to the heated water and stir to mix, thus obtaining a sodium dodecyl sulfate solution.

[0028] The cocamidopropyl betaine and the sodium dodecyl sulfate solution are mixed by the fifth stirring to obtain a foaming agent; wherein the stirring speed of the fifth stirring is 30 r / min to 60 r / min, and the stirring time of the fifth stirring is 10 min to 15 min.

[0029] The technical solutions provided in this application have the following advantages compared with the prior art:

[0030] This application provides a foam acid unblocking system in which the total weight m1 of the foam acid component and the total weight m2 of the foaming agent satisfy the following formula: m1:m2=100:(1.5~2.5), and the volume V1 of the gas phase component and the total volume V2 of the foam acid component satisfy the following formula: V1:V2≥40:1. Sufficient foam can be generated through the interaction between the gas phase component and the foaming agent. This sufficient foam promotes the formation of a uniformly distributed dispersed phase of the foam acid component. The foam acid component in the uniformly distributed dispersed phase not only has… The fluid properties of foam and the acidic corrosiveness of acid cause this foam-acid unblocking system to generate a gas blocking effect in the channel of heterogeneous reservoirs. This gas blocking effect allows the foam-acid unblocking system to penetrate the low-permeability layer of the heterogeneous reservoir, thereby improving the unblocking effect of the acid unblocking agent. Furthermore, the weights of oxalic acid (m3), phosphoric acid (m4), triethanolamine (m5), dimethyl diallyl ammonium chloride (m6), foaming agent (m2), acetic acid (m7), disodium phosphate (m8), and sodium nitrite (m9) satisfy the following relationship:

[0031] The formula m3:m4:m5:m6:m2:m7:m8:m9=(10~12):(3~5):4:2:(1.5~2.5):0.05:0.05:1 can enhance the transport effect of the foam acid component on heavy components and clay, and further promote the uniform dispersion of the foam acid component in the heterogeneous layer, thereby improving the unblocking effect of the acid unblocking agent in the heterogeneous layer. Attached Figure Description

[0032] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0033] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic flowchart of a method for preparing a foam acid unblocking system provided in an embodiment of this application;

[0035] Figure 2 This is a detailed flowchart illustrating a method for preparing a foam acid unblocking system, as provided in an embodiment of this application. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0037] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range; for example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range such as 1, 2, 3, 4, 5, and 6, regardless of the range; in addition, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.

[0038] In this document, terms such as "comprising" mean "including but not limited to". Relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. "And / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone; where A and B can be singular or plural. Unless otherwise specified, all raw materials, reagents, instruments, and equipment used in this application are commercially available or can be prepared using existing methods.

[0039] It should be noted that the main causes of oil layer blockage are as follows:

[0040] ① When water-sensitive minerals in the oil reservoir encounter incompatible fluids during thermal recovery operations, they will expand and migrate, thus clogging the oil reservoir;

[0041] ② When metal ions in the oil layer come into contact with external fluids, they will undergo a chemical reaction to form inorganic scale, which will then clog the oil layer;

[0042] ③ During the oilfield production process, the heavy components of crude oil will continuously precipitate and form sediments. These sediments will block the pores of the formation, thereby affecting the production effect;

[0043] ④ Due to the continuous scouring during the water injection stage of the mining process, the rock pore structure and cementation state of the strata will change during the scouring process, resulting in the generation of solid particles. These solid particles will block the rock pore structure of the strata.

[0044] Therefore, regular unblocking has become an important technique for relieving damage to oil reservoirs in the near-wellbore zone.

[0045] Foam acid acidification technology involves adding foaming agents and foam stabilizers to a conventional acid system and mixing it with a gas (usually nitrogen or carbon dioxide) through a foam generator. During this mixing process, the acid system adheres to the surface of the foam and forms a dispersed phase. This dispersed phase not only possesses the characteristics of foam fluid but also has acidic corrosion capabilities, ensuring that the acid components in the foam are uniformly dispersed within the heterogeneous layer. This, in turn, improves the unblocking effect of acidic unblocking agents in heterogeneous layers.

[0046] This application provides a foam acid unblocking system, which includes a foam acid component, a foaming agent, and a gaseous component. The foam acid component includes oxalic acid, phosphoric acid, triethanolamine, dimethyldiallylammonium chloride, acetic acid, disodium phosphate, and sodium nitrite. The total weight m1 of the foam acid component and the total weight m2 of the foaming agent satisfy the following formula: m1:m2 = 100:(1.5~2.5). The volume V1 of the gaseous component and the total volume V2 of the foam acid component satisfy the following formula: V1:V2 ≥ 40:1.

[0047] The weights of oxalic acid (m3), phosphoric acid (m4), triethanolamine (m5), dimethyldiallylammonium chloride (m6), foaming agent (m2), acetic acid (m7), disodium phosphate (m8), and sodium nitrite (m9) satisfy the following relationship: m3:m4:m5:m6:m2:m7:m8:m9=(10~12):(3~5):4:2:(1.5~2.5):0.05:0.05:1.

[0048] The total weight m1 of the foam acid component and the total weight m2 of the foaming agent satisfy the following: m1:m2 = 100:1.5, 100:2.0 or 100:2.5.

[0049] The weights of the diacid (m3), phosphoric acid (m4), triethanolamine (m5), dimethyldiallylammonium chloride (m6), foaming agent (m2), acetic acid (m7), disodium phosphate (m8), and sodium nitrite (m9) satisfy the following relationships: m3:m4:m5:m6:m2:m7:m8:m9 = 10:3:4:2:1.5:0.05:0.05:1, 10:3:4:2:2.0:0.05:0.05:1, 10:3:4:2:2.5:0.05:0.05:1, 10:4:4:2:1.5 :0.05:0.05:1、10:4:4:2:2.0:0.05:0.05:1、10:4:4:2:2.5:0.05:0.05:1、10:5:4:2:1.5:0.05:0.05:1、10:5:4:2:2.0:0.05:0.05:1、10:5:4:2:2.5:0.05:0.05:1、11:3:4:2:1.5:0.05:0.05:1、11:3:4:2:2.0:0.05:0.05:1、11:3:4:2 :2.5:0.05:0.05:1、11:4:4:2:1.5:0.05:0.05:1、11:4:4:2:2.0:0.05:0.05:1、11:4:4:2:2.5:0.05:0.05:1、11:5:4:2:1.5:0.05:0.05:1、11:5:4:2:2.0:0.05:0.05:1、11:5:4:2:2.5:0.05:0.05:1、12:3:4:2:1.5:0.05:0.05:1、12:3 :4:2:2.0:0.05:0.05:1、12:3:4:2:2.5:0.05:0.05:1、12:4:4:2:1.5:0.05:0.05:1、12:4:4:2:2.0:0.05:0.05:1、12:4:4:2:2.5:0.05:0.05:1、12:5:4:2:1.5:0.05:0.05:1、12:5:4:2:2.0:0.05:0.05:1 or 12:5:4:2:2.5:0.05:0.05:1.

[0050] It should be noted that the gaseous component can be an inert gas.

[0051] In some alternative embodiments, the foaming agent comprises sodium dodecyl sulfate and / or cocamidopropyl betaine;

[0052] In these embodiments, the foaming agent may include sodium dodecyl sulfate and / or cocamidopropyl betaine. Foaming agents such as sodium dodecyl sulfate and cocamidopropyl betaine, which are salt-resistant, acid-resistant, and temperature-resistant, can promote the interaction between the gas phase component and the foam acid component to generate sufficient foam. This sufficient foam will promote the formation of a uniformly distributed dispersed phase of the foam acid component, which can improve the unblocking effect of the acid unblocking agent in heterogeneous strata.

[0053] In some alternative embodiments, when the foaming agent comprises sodium dodecyl sulfate and cocamidopropyl betaine, the weight m11 of the sodium dodecyl sulfate and the weight m12 of the cocamidopropyl betaine satisfy the relationship: m11:m12=(20~30):(5~10);

[0054] In these embodiments, when the foaming agent includes sodium dodecyl sulfate and cocamidopropyl betaine, the weight m11 of sodium dodecyl sulfate and the weight m12 of cocamidopropyl betaine can satisfy the relationship: m11:m12=(20~30):(5~10), which can improve the salt resistance, acid resistance and temperature resistance of the foaming agent, so that the interaction between the gas phase component and the foam acid component generates sufficient foam. This sufficient foam will promote the formation of a uniformly distributed dispersed phase of the foam acid component, which can improve the unblocking effect of the acid unblocking agent in heterogeneous layers.

[0055] The weights m11 of sodium dodecyl sulfate and m12 of cocamidopropyl betaine can satisfy the following relationship: m11:m12 = 20:5, 20:6, 20:7, 20:8, 20:9, 20:10, 25:5, 25:6, 25:7, 25:8, 25:9, 25:10, 30:5, 30:6, 30:7, 30:8, 30:9, or 30:10.

[0056] In some alternative embodiments, the gaseous component includes nitrogen and / or carbon dioxide;

[0057] In these embodiments, the gaseous component may include nitrogen and / or carbon dioxide, which can generate sufficient foam through the interaction between the gaseous component and the foaming agent. This sufficient foam will promote the formation of a uniformly distributed dispersed phase of the foam acid component, which can improve the unblocking effect of the acid unblocking agent in heterogeneous strata.

[0058] Figure 1 An exemplary schematic diagram of a method for preparing a foam acid unblocking system provided in an embodiment of this application is shown;

[0059] Based on a general inventive concept, such as Figure 2As shown, this application provides a method for preparing the foam acid unblocking system, the method comprising:

[0060] S1. Oxalic acid, phosphoric acid, triethanolamine, dimethyldiallylammonium chloride and acetic acid are mixed to obtain crude foam acid component;

[0061] S2. Preparation of foaming agent;

[0062] S3. The foaming agent and the coarse foaming acid component are first stirred and mixed to obtain a first mixture;

[0063] S4. Sodium disodium phosphate and sodium nitrite are added sequentially to the first mixture and stirred to obtain a liquid phase component;

[0064] S5. Mix the gas phase component and the liquid phase component according to a preset flow rate ratio to obtain a foam acid unblocking system.

[0065] This method is for the preparation of the foam acid unblocking system described above. The specific composition of the foam acid unblocking system can be referred to in the above embodiments. Since this method adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0066] Figure 2 A detailed flowchart illustrating a method for preparing a foam acid unblocking system provided in an embodiment of this application is shown by way of example.

[0067] In some alternative implementations, such as Figure 2 As shown, the step of mixing oxalic acid, phosphoric acid, triethanolamine, dimethyldiallyl ammonium chloride, and acetic acid to obtain a crude foam acid component includes the following steps:

[0068] S101. Oxalic acid and phosphoric acid are mixed by a second stirring to obtain a second mixture;

[0069] S102. Triethanolamine and the second mixture are stirred and mixed in a third stirring process to obtain a third mixture;

[0070] S103. Dimethyl diallyl ammonium chloride and the third mixture are subjected to a fourth stirring and mixing to obtain a fourth mixture;

[0071] S104. Acetic acid and the fourth mixture are stirred and mixed in the fourth stirring process to obtain a crude foam acid component;

[0072] In these embodiments, by staged stirring and mixing of oxalic acid, phosphoric acid, triethanolamine, dimethyldiallylammonium chloride and acetic acid in the foam acid component, a coarse foam acid component with uniform component distribution can be obtained, which facilitates the subsequent obtaining of a foam acid unblocking system with uniform component distribution, so as to finally obtain a foam acid unblocking system in a uniformly distributed dispersed phase.

[0073] In some optional embodiments, the second stirring speed is 100 r / min to 150 r / min, and the second stirring time is 15 min to 20 min;

[0074] The third stirring speed is 150 r / min to 200 r / min, and the third stirring time is 20 min to 25 min;

[0075] The speed of the fourth stirring and mixing is 200 r / min to 250 r / min, and the time of the fourth stirring and mixing is 25 min to 30 min;

[0076] In these embodiments, the second stirring speed can be 100 r / min to 150 r / min, and the second stirring time can be 15 min to 20 min. The second stirring promotes thorough mixing between oxalic acid and phosphoric acid, resulting in a uniformly dispersed second mixture. The third stirring speed can be 150 r / min to 200 r / min, and the third stirring time can be 20 min to 25 min. The third stirring promotes thorough mixing between oxalic acid, phosphoric acid, and triethanolamine, resulting in a uniformly dispersed third mixture. The fourth stirring speed can be 200 r / min to 250 r / min, and the fourth stirring time can be 25 min to 30 min. The fourth stirring promotes thorough mixing between dimethyl diallyl ammonium chloride, acetic acid, oxalic acid, phosphoric acid, and triethanolamine, resulting in a uniformly dispersed coarse foam acid component.

[0077] The second stirring speed can be 100 r / min, 110 r / min, 120 r / min, 130 r / min, 140 r / min or 150 r / min.

[0078] The second mixing time can be 15 min, 16 min, 17 min, 18 min, 19 min, or 20 min.

[0079] The third stirring speed can be 150 r / min, 160 r / min, 170 r / min, 180 r / min, 190 r / min or 200 r / min.

[0080] The third mixing time can be 20 min, 21 min, 22 min, 23 min, 24 min, or 25 min.

[0081] The speed of the fourth stirring and mixing can be 200 r / min, 210 r / min, 220 r / min, 230 r / min, 240 r / min or 250 r / min.

[0082] The fourth mixing time can be 25 min, 26 min, 27 min, 28 min, 29 min, or 30 min.

[0083] It should be noted that the first stirring and mixing, the second stirring and mixing, the third stirring and mixing, the fourth stirring and mixing, and the fifth stirring and mixing refer to different stages of stirring and mixing. As is well known to those skilled in the art, these stirring and mixing processes can all be carried out using the same stirring device.

[0084] In some optional embodiments, the first stirring speed is 100 r / min to 150 r / min, and the first stirring time is 20 min to 25 min;

[0085] In these embodiments, the first stirring speed can be 100 r / min to 150 r / min, and the first stirring time can be 20 min to 25 min. The foaming agent and foam acid component are stirred evenly through the first stirring, thereby obtaining a liquid phase component with uniform component composition.

[0086] The rotation speed of the first stirring and mixing can be 100 r / min, 110 r / min, 120 r / min, 130 r / min, 140 r / min or 150 r / min.

[0087] The first mixing time can be 20 min, 21 min, 22 min, 23 min, 24 min, or 25 min.

[0088] In some optional implementations, the preset flow rate ratio is (500-800):(3-5);

[0089] In these embodiments, the preset flow rate ratio can be (500-800):(3-5). By using the preset flow rate ratio, the liquid phase component and the gas phase component can be fully mixed, thereby obtaining a foam acid unblocking system with uniform component distribution.

[0090] The preset flow rate ratio can be 500:3, 500:4, 500:5, 600:3, 600:4, 600:5, 700:3, 700:4, 700:5, 800:3, 800:4, or 800:5.

[0091] In some alternative implementations, such as Figure 2 As shown, the preparation of the foaming agent includes the following steps:

[0092] S201. Heat the water, then add sodium dodecyl sulfate to the heated water and stir to mix, to obtain a sodium dodecyl sulfate solution;

[0093] S202. Cocamidopropyl betaine and the sodium dodecyl sulfate solution are mixed by the fifth stirring to obtain a foaming agent; wherein the stirring speed of the fifth stirring is 30 r / min to 60 r / min, and the stirring time of the fifth stirring is 10 min to 15 min;

[0094] In these embodiments, the fifth stirring speed can be 30 r / min to 60 r / min, and the fifth stirring time can be 10 min to 15 min. By mixing sodium dodecyl sulfate, water and cocamidopropyl betaine thoroughly through the fifth stirring, a foaming agent that is salt-resistant, acid-resistant and temperature-resistant can be obtained.

[0095] The fifth stirring speed can be 30 r / min, 40 r / min, 50 r / min or 60 r / min.

[0096] The fifth mixing time can be 10 min, 11 min, 12 min, 13 min, 14 min or 15 min.

[0097] The present application is further illustrated below with reference to specific embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to industry standards; if no corresponding industry standard exists, they are performed according to general international standards, conventional conditions, or conditions recommended by the manufacturer.

[0098] Example 1

[0099] like Figure 1 As shown, a foam acid unblocking system includes a foam acid component, a foaming agent, and a gas phase component. The foam acid component includes oxalic acid, phosphoric acid, triethanolamine, dimethyl diallyl ammonium chloride, acetic acid, disodium phosphate, and sodium nitrite. The total weight m1 of the foam acid component and the total weight m2 of the foaming agent satisfy the formula: m1:m2 = 100:1.5. The volume V1 of the gas phase component and the total volume V2 of the foam acid component satisfy the formula: V1:V2 = 40:1.

[0100] The weights of oxalic acid (m3), phosphoric acid (m4), triethanolamine (m5), dimethyl diallyl ammonium chloride (m6), foaming agent (m2), acetic acid (m7), disodium phosphate (m8), and sodium nitrite (m9) satisfy the following relationship: m3:m4:m5:m6:m2:m7:m8:m9 = 10:3:4:2:1.5:0.05:0.05:1.

[0101] The foaming agent includes sodium dodecyl sulfate and cocamidopropyl betaine. The weights of sodium dodecyl sulfate (m11) and cocamidopropyl betaine (m12) satisfy the relationship: m11:m12 = 20:5.

[0102] The gaseous components include nitrogen and / or carbon dioxide.

[0103] like Figure 2 As shown, a method for preparing a foam acid unblocking system includes:

[0104] S101. Oxalic acid and phosphoric acid are mixed by a second stirring to obtain a second mixture;

[0105] S102. Triethanolamine and the second mixture are stirred and mixed for the third time to obtain a third mixture;

[0106] S103. Dimethyl diallyl ammonium chloride and the third mixture are stirred and mixed in a fourth stirring process to obtain a fourth mixture;

[0107] S104. Acetic acid and the fourth mixture are stirred and mixed in a fourth stirring process to obtain a crude foam acid component;

[0108] S201. Heat the water to 45°C, then add sodium dodecyl sulfate to the heated water and stir to mix, to obtain a sodium dodecyl sulfate solution;

[0109] S202. Cocamidopropyl betaine and sodium dodecyl sulfate solution are mixed by a fifth stirring to obtain a foaming agent; wherein, the stirring speed of the fifth stirring is 45 r / min and the stirring time is 12 min;

[0110] S3. The foaming agent and the coarse foaming acid component are mixed by first stirring to obtain the first mixture;

[0111] S4. Sodium disodium phosphate and sodium nitrite are added sequentially to the first mixture and stirred for the first time to obtain the liquid phase component;

[0112] S5. Mix the gas phase component and the liquid phase component according to the preset flow rate ratio to obtain the foam acid unblocking system.

[0113] The preset flow rate ratio is 500:3.

[0114] The second stirring speed is 120 r / min, and the second stirring time is 15 min;

[0115] The third stirring speed is 180 r / min, and the third stirring time is 20 min;

[0116] The fourth mixing speed is 220 r / min, and the fourth mixing time is 25 min.

[0117] Example 2

[0118] Based on the content disclosed in Example 1, the following modifications are made:

[0119] The total weight m1 of the foaming acid component and the total weight m2 of the foaming agent satisfy the following formula: m1:m2=100:1.5; the volume V1 of the gas phase component and the total volume V2 of the foaming acid component satisfy the following formula: V1:V2=40:1;

[0120] The weights of oxalic acid (m3), phosphoric acid (m4), triethanolamine (m5), dimethyldiallylammonium chloride (m6), foaming agent (m2), acetic acid (m7), disodium phosphate (m8), and sodium nitrite (m9) satisfy the following relationship: m3:m4:m5:m6:m2:m7:m8:m9 = 12:5:4:2:2.5:0.05:0.05:1.

[0121] The foaming agent includes sodium dodecyl sulfate and cocamidopropyl betaine. The weights of sodium dodecyl sulfate (m11) and cocamidopropyl betaine (m12) satisfy the relationship: m11:m12 = 30:10.

[0122] The fifth mixing speed is 30 r / min, and the fifth mixing time is 10 min.

[0123] The preset flow rate ratio is 800:5.

[0124] The second stirring speed is 100 r / min, and the second stirring time is 15 min;

[0125] The third stirring speed is 150 r / min, and the third stirring time is 25 min;

[0126] The fourth mixing speed is 200 r / min, and the fourth mixing time is 30 min.

[0127] Example 3

[0128] Based on the content disclosed in Example 1, the following modifications are made:

[0129] The total weight m1 of the foaming acid component and the total weight m2 of the foaming agent satisfy the following formula: m1:m2=100:2.0; the volume V1 of the gas phase component and the total volume V2 of the foaming acid component satisfy the following formula: V1:V2=40:1;

[0130] The weights of oxalic acid (m3), phosphoric acid (m4), triethanolamine (m5), dimethyldiallylammonium chloride (m6), foaming agent (m2), acetic acid (m7), disodium phosphate (m8), and sodium nitrite (m9) satisfy the following relationship: m3:m4:m5:m6:m2:m7:m8:m9 = 11:4:4:2:2.0:0.05:0.05:1.

[0131] The foaming agent includes sodium dodecyl sulfate and cocamidopropyl betaine. The weights of sodium dodecyl sulfate (m11) and cocamidopropyl betaine (m12) satisfy the relationship: m11:m12 = 25:7.

[0132] The fifth stirring speed is 50 r / min, and the fifth stirring time is 15 min.

[0133] The preset flow rate ratio is 600:4.

[0134] The second stirring speed is 130 r / min, and the second stirring time is 18 min;

[0135] The third stirring speed is 185 r / min, and the third stirring time is 22 min;

[0136] The fourth mixing speed was 230 r / min, and the fourth mixing time was 28 min.

[0137] Comparative Example 1

[0138] Based on the content disclosed in Example 1, the following modifications are made:

[0139] The total weight m1 of the foaming acid component and the total weight m2 of the foaming agent satisfy the following formula: m1:m2=100:2.0; the volume V1 of the gas phase component and the total volume V2 of the foaming acid component satisfy the following formula: V1:V2=40:1;

[0140] The weights of oxalic acid (m3), phosphoric acid (m4), triethanolamine (m5), dimethyldiallylammonium chloride (m6), foaming agent (m2), acetic acid (m7), disodium phosphate (m8), and sodium nitrite (m9) satisfy the following relationship: m3:m4:m5:m6:m2:m7:m8:m9=14:4:4:2:2.0:0.05:0.05:1.

[0141] The foaming agent includes sodium dodecyl sulfate and cocamidopropyl betaine. The weights of sodium dodecyl sulfate (m11) and cocamidopropyl betaine (m12) satisfy the relationship: m11:m12 = 25:7.

[0142] The fifth mixing speed was 40 r / min, and the fifth mixing time was 13 min.

[0143] The preset flow rate ratio is 600:4.

[0144] The second stirring speed is 145 r / min, and the second stirring time is 20 min;

[0145] The third stirring speed is 175 r / min, and the third stirring time is 23 min;

[0146] The fourth mixing speed was 225 r / min, and the fourth mixing time was 27 min.

[0147] Comparative Example 2

[0148] Based on the content disclosed in Example 1, the following modifications are made:

[0149] The total weight m1 of the foaming acid component and the total weight m2 of the foaming agent satisfy the following formula: m1:m2=100:2.0; the volume V1 of the gas phase component and the total volume V2 of the foaming acid component satisfy the following formula: V1:V2=40:1;

[0150] The weights of oxalic acid (m3), phosphoric acid (m4), triethanolamine (m5), dimethyl diallyl ammonium chloride (m6), foaming agent (m2), acetic acid (m7), disodium phosphate (m8), and sodium nitrite (m9) satisfy the following relationship: m3:m4:m5:m6:m2:m7:m8:m9=6:4:4:2:2.0:0.05:0.05:1.

[0151] The foaming agent includes sodium dodecyl sulfate and cocamidopropyl betaine. The weights of sodium dodecyl sulfate (m11) and cocamidopropyl betaine (m12) satisfy the relationship: m11:m12 = 25:7.

[0152] The fifth mixing speed was 35 r / min, and the fifth mixing time was 12 min.

[0153] The preset flow rate ratio is 600:4.

[0154] The second stirring speed is 110 r / min, and the second stirring time is 14 min;

[0155] The third stirring speed is 165 r / min, and the third stirring time is 18 min;

[0156] The fourth mixing speed was 210 r / min, and the fourth mixing time was 22 min.

[0157] Relevant experimental and effect data:

[0158] 1. The foam acid deblocking systems obtained from each embodiment and comparative example were applied in practice, and their deblocking performance was statistically analyzed. The results are shown in Table 1.

[0159] Table 1. Declogging performance of the foam declogging systems in each embodiment and comparative example.

[0160]

[0161] As shown in Table 1, the foam acid unblocking system provided in this application embodiment allows the foam acid unblocking system to enter the low-permeability layer of the heterogeneous layer through the interaction between the foam acid component, the foaming agent, and the gas phase component, thereby improving the unblocking effect of the acid unblocking agent in the heterogeneous layer. Furthermore, refining the specific composition of the foam acid component to include oxalic acid, phosphoric acid, triethanolamine, dimethyl diallyl ammonium chloride, acetic acid, disodium phosphate, and sodium nitrite further promotes the uniform dispersion of the foam acid component within the heterogeneous layer, thereby improving the unblocking effect of the acid unblocking agent in the heterogeneous layer. Its blockage dissolution rate is above 65%, and its dissolution rate is 1.20 g / (m³). 2 The foaming ratio is above 4.0 times and the stable foaming time is above 420 seconds.

[0162] In Comparative Example 1, the high concentration of oxalic acid resulted in an excessively fast dissolution rate for the foam acid unblocking system. However, the high concentration of oxalic acid made it difficult to ensure the safety of the construction process, and it also significantly reduced the foaming performance of the foaming agent within the system. Furthermore, the insufficient oxalic acid content in Comparative Example 2 resulted in an excessively low dissolution rate, making it difficult to use the foam acid unblocking system of Comparative Example 2 in actual production.

[0163] 2. Practical applications of foam acid unblocking systems:

[0164] The foam acid unblocking system obtained in Example 3 was then put into practical application:

[0165] Well Du 212-Xing H230 was selected. Well Du 212-Xing H230 is an extra-heavy oil well in the Du 212 Xinglongtai reservoir. It began steam injection development in April 2011. Initially, the steam injection pressure remained high. Viscosity-reducing and drainage-aiding measures were implemented for 2-5 production cycles, resulting in improved production. However, during the 6th steam injection cycle in July 2014, the pressure rose to 16.9 MPa, indicating reservoir damage. Therefore, a foam acid unblocking system was used for foam acidizing.

[0166] After foam acidizing, the injection pressure of the production well decreased by nearly 1 MPa, the production days were extended by 7 days, and fluid production increased by 576 tons within the cycle. The production-injection ratio and oil-steam ratio also improved significantly. A comparison of the well temperature curves before and after the treatment revealed that the initial section was better utilized, accounting for about 1 / 4 of the entire well section. After the treatment, the length of the well section with good utilization increased to about 2 / 3. This indicates that the foam acidizing technology using the foam acid unblocking system uniformly treated the entire well section, and the steam absorption in the horizontal section was generally improved. Furthermore, the well's subsequent production performance was also positively affected after the treatment, with a steady increase in production.

[0167] As can be seen from the above examples, conventional acidizing and unblocking technologies have problems such as fast reaction rate, small treatment radius, and large amount of acid residue generated. At the same time, due to the special structure of horizontal wells, acid cannot be evenly distributed in the horizontal well section, resulting in the damaged section not being treated, which affects the effectiveness of acidizing and unblocking technologies.

[0168] The foam acid unblocking system provided in this application not only possesses the characteristics of foam fluid but also has the ability to acidify and corrode. This results in the following main advantages of using the foam acid unblocking system in heavy oil horizontal wells: The foam acid unblocking system generates a gas-blocking effect in the channels of heterogeneous reservoirs, allowing it to penetrate into the low-permeability layers of the heterogeneous reservoir and react with the rock. Simultaneously, the foam generated by the foam acid unblocking system significantly increases the volume of the foam acid components, improving the treatment area and thus achieving deep acidification. Furthermore, after the foam expands due to gas, it provides energy for the return of residual acid, ensuring more thorough return and preventing secondary precipitation. Therefore, the overall unblocking effect of the foam acid unblocking system in heterogeneous reservoirs can be comprehensively improved.

[0169] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed in this application.

Claims

1. A foam acid unblocking system, characterized in that, The foam acid unblocking system includes a foam acid component, a foaming agent, and a gaseous component. The foam acid component includes oxalic acid, phosphoric acid, triethanolamine, dimethyl diallyl ammonium chloride, acetic acid, disodium phosphate, and sodium nitrite. The total weight m1 of the foam acid component and the total weight m2 of the foaming agent satisfy the following formula: m1:m2 = 100:(1.5~2.5). The volume V1 of the gaseous component and the total volume V2 of the foam acid component satisfy the following formula: V1:V2 ≥ 40:

1. The weights of oxalic acid (m3), phosphoric acid (m4), triethanolamine (m5), dimethyldiallylammonium chloride (m6), foaming agent (m2), acetic acid (m7), disodium phosphate (m8), and sodium nitrite (m9) satisfy the following relationship: m3:m4:m5:m6:m2:m7:m8:m9=(10~12):(3~5):4:2:(1.5~2.5):0.05:0.05:

1.

2. The foam acid unblocking system according to claim 1, characterized in that, The foaming agent includes sodium dodecyl sulfate and / or cocamidopropyl betaine.

3. The foam acid unblocking system according to claim 1 or 2, characterized in that, When the foaming agent includes sodium dodecyl sulfate and cocamidopropyl betaine, the weight m11 of the sodium dodecyl sulfate and the weight m12 of the cocamidopropyl betaine satisfy the relationship: m11:m12=(20~30):(5~10).

4. The foam acid unblocking system according to claim 1, characterized in that, The gaseous components include nitrogen and / or carbon dioxide.

5. A method for preparing the foam acid unblocking system as described in any one of claims 1 to 4, characterized in that, The method includes: Oxalic acid, phosphoric acid, triethanolamine, dimethyldiallylammonium chloride and acetic acid are mixed to obtain crude foam acid component; Preparation of foaming agents; The foaming agent and the coarse foaming acid component are first stirred and mixed to obtain a first mixture; Sodium disodium phosphate and sodium nitrite were added sequentially to the first mixture and stirred to obtain the liquid phase component. The gas phase component and the liquid phase component are mixed at a preset flow rate ratio to obtain a foam acid unblocking system.

6. The method according to claim 5, characterized in that, The step of mixing oxalic acid, phosphoric acid, triethanolamine, dimethyldiallyl ammonium chloride, and acetic acid to obtain a crude foam acid component includes the following steps: Oxalic acid and phosphoric acid are mixed again by stirring to obtain a second mixture; Triethanolamine and the second mixture are then stirred and mixed in a third stirring process to obtain a third mixture. Dimethyl diallyl ammonium chloride and the third mixture are subjected to a fourth stirring and mixing to obtain a fourth mixture. Acetic acid and the fourth mixture are stirred and mixed in the fourth manner to obtain a crude foam acid component.

7. The method according to claim 6, characterized in that, The second stirring speed is 100 r / min to 150 r / min, and the second stirring time is 15 min to 20 min; The third stirring speed is 150 r / min to 200 r / min, and the third stirring time is 20 min to 25 min; The speed of the fourth stirring and mixing is 200 r / min to 250 r / min, and the time of the fourth stirring and mixing is 25 min to 30 min.

8. The method according to claim 5, characterized in that, The first stirring speed is 100 r / min to 150 r / min, and the first stirring time is 20 min to 25 min.

9. The method according to claim 5, characterized in that, The preset flow rate ratio is (500~800):(3~5).

10. The method according to claim 5, characterized in that, The preparation of the foaming agent includes the following steps: Heat the water, then add sodium dodecyl sulfate to the heated water and stir to mix, thus obtaining a sodium dodecyl sulfate solution. The cocamidopropyl betaine and the sodium dodecyl sulfate solution are mixed by the fifth stirring to obtain a foaming agent; wherein the stirring speed of the fifth stirring is 30 r / min to 60 r / min, and the stirring time of the fifth stirring is 10 min to 15 min.

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