Retarded acid for carbonate reservoir and application thereof

Abstract

The invention relates to retarded acid for a carbonate rock reservoir and application thereof, and aims to solve the problems of poor high temperature resistance and too high acid rock reaction rate of the current retarded acid for the carbonate rock reservoir. The retarded acid for the carbonate rock reservoir comprises an acid agent, a functional aid and water; the acid agent comprises inorganic acid, organic acid, a chelating agent and organic ester in a mass ratio of 1: (10-13): (5-6): (3-4). According to the retarded acid provided by the invention, the acid agent is specifically designed, and the inorganic acid, the organic acid, the chelating agent and the organic ester in a specific ratio are matched, so that the retarded acid has high temperature resistance, and meanwhile, the problem that the acid-rock reaction rate is too high is avoided. And the deep transformation of the acid liquid in the reservoir is realized under the clamping of a low acid rock reaction rate. And by means of the high resistance reduction capacity after weight increasing, it is guaranteed that the construction operation pressure is reduced in the deep well and ultra-deep well reservoir transformation process, and therefore the efficient reservoir transformation capacity is achieved.

Description

Technical Field

[0001] The invention relates to the field of oilfield chemical additives, and in particular to a slow-release acid for carbonate reservoirs and a use thereof. Background Art

[0002] At present, acidizing is one of the main technological measures for stabilizing and increasing production of oil and gas wells, and stabilizing and increasing injection of water injection wells. It is a production-increasing measure that uses acid to remove pollutants near the bottom of production wells and water injection wells, restore the permeability of the formation, or dissolve the rock cement of the formation to increase the permeability of the formation. The purpose is to use acid to remove the damage to the formation near the wellbore caused by drilling, completion, well repair and injection, and to dredge the liquid seepage channel, thereby restoring and improving the production capacity of oil and gas wells.

[0003] CN110564398A discloses a slow-down acid system, the components of which include alkyl trimethyl ammonium chloride and water-soluble calcium salt; the alkyl group is a long-chain alkyl group with 8-22 carbon atoms. The components also include a corrosion inhibitor Mannich base and an iron ion stabilizer, both of which are added in an amount of 1%. In practical applications, the mass percentage of alkyl trimethyl ammonium chloride is 0.12-0.95%. The dosage concentration of calcium salt is 10-100mmol / L. Alkyl trimethyl ammonium chloride acts on the rock surface through physical adsorption, covers the rock surface, and performs hydrophobic wetting modification on it, so that the hydrophilic H+ is not easy to contact the rock surface, controls the reaction surface rate, prolongs the acid-rock reaction time, and thus achieves the slow-down effect. The slow-down acid component of the present invention has a low molecular weight, small formation damage, and low viscosity of the acid system. It can enter small-scale cracks to perform non-uniform etching on its wall surface, increase the complexity of the crack network, and improve the construction effect.

[0004] However, the effect of acidizing, especially the acidizing effect of high-temperature, low-permeability deep wells, depends to a large extent on the acid additives and acidizing working fluids used. Conventional acidizing operations can generally only eliminate the permeability damage around the wellbore, and the oil and gas production increase effect is unsatisfactory and the effective time is short. This is because the acid-rock reaction is too fast and the active acid does not fully penetrate the formation. It may also cause serious corrosion in the area around the wellbore, causing formation blockage and affecting oil and gas production. Whether it is the reaction of hydrochloric acid with carbonate rock or soil acid with sandstone formation, the chemical reaction rate is very fast, and the deep part cannot be properly acidified. The reaction process between acid and formation can be divided into three steps: ① H in the liquid phase + Diffusion to the rock surface; ②H +③ The reaction products diffuse from the rock surface into the liquid phase. With the deepening of people's understanding of the formation damage mechanism and the acid-formation reaction mechanism, as well as the growing development of the world's chemical industry, various oil and gas fields at home and abroad have targetedly developed and promoted a variety of chemical retarded acid systems. The research focuses on changing the chemical properties of the acid, especially the colloidal chemical properties, further expanding the depth and range of acid treatment, reducing formation damage, and improving the acidizing effect.

[0005] Currently, more and more unconventional oil and gas fields need to be developed. Unlike conventional oil and gas fields, these oil fields have poor reservoir conditions, low permeability, high oil and gas layer pressure and high temperature. Therefore, there is an urgent need to develop an ultra-high temperature aggravable super-retarded acid system. Summary of the invention

[0006] In view of the problems existing in the prior art, the purpose of the present invention is to provide a retarded acid for carbonate reservoirs and its use, so as to solve the problems of poor high temperature resistance and excessively fast acid-rock reaction rate of the current retarded acid for carbonate reservoirs.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a retarded acid for carbonate reservoirs, the retarded acid for carbonate reservoirs comprising an acid agent, a functional additive and water;

[0009] The acid agent includes an inorganic acid, an organic acid, a chelating agent and an organic ester in a mass ratio of 1:(10-13):(5-6):(3-4).

[0010] The retarded acid provided by the present invention is specifically designed for the acid agent, and is matched with inorganic acid, organic acid, chelating agent and organic ester in a specific ratio, so that the retarded acid has high temperature resistance and also avoids the problem of too fast acid-rock reaction rate. The deep transformation of the acid in the reservoir is achieved with the support of low acid-rock reaction rate. The high drag reduction capacity after weighting ensures that the construction pressure is reduced during the transformation of deep well and ultra-deep well reservoirs, thereby achieving efficient reservoir transformation capabilities.

[0011] As a preferred technical solution of the present invention, the retarding acid for carbonate reservoirs comprises, by weight, 10-25 parts of an acid agent, 0.2-22 parts of a functional additive and 50-70 parts of water.

[0012] As a preferred technical solution of the present invention, the inorganic acid includes one or a combination of at least two of hydrochloric acid, hydrofluoric acid, nitric acid or sulfuric acid.

[0013] As a preferred technical solution of the present invention, the organic acid includes a combination of at least three of citric acid, malic acid, formic acid, acetic acid, aminosulfonic acid, tartaric acid, glutamic acid or oxalic acid.

[0014] As a preferred technical solution of the present invention, the chelating agent includes one or a combination of at least two of ethylenediaminetetraacetic acid, methylglycine diacetic acid, diethylenetriamine pentaacetic acid or 1,3-propylenediamine-N,N,N,N-tetraacetic acid.

[0015] As a preferred technical solution of the present invention, the organic ester includes one or a combination of at least two of methyl formate, methyl acetate, methyl trifluoroacetate, methyl 2-bromopropionate, methyl thioglycolate or chloromethyl isopropyl carbonate.

[0016] As a preferred technical solution of the present invention, the functional additive includes one or a combination of at least two of a modified drag reducer, a corrosion inhibitor or a weighting agent.

[0017] As a preferred technical solution of the present invention, the modified drag reducer in the functional additive is 0.2-0.5 parts by weight.

[0018] Preferably, the corrosion inhibitor in the functional additive is 2-5 parts by weight.

[0019] Preferably, the weighting agent in the functional additive is 14-16.5 parts by weight.

[0020] As a preferred technical solution of the present invention, the modified drag reducer comprises acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, N,N'-dimethylacrylamide and N-dodecylacrylamide copolymerized by a step-by-step inverse emulsion polymerization method.

[0021] Preferably, the corrosion inhibitor comprises a Mannich base corrosion inhibitor.

[0022] Preferably, the weighting agent comprises one or a combination of at least two of potassium chloride, potassium bromide, calcium chloride, calcium bromide, sodium sulfate, calcium sulfate, sodium formate or cesium formate.

[0023] In a second aspect, the present invention provides a use of the slow-rate acid for carbonate reservoirs as described in the first aspect, wherein the use comprises performing a transformation operation on the carbonate reservoir using the slow-rate acid for carbonate reservoirs.

[0024] Compared with the prior art solutions, the present invention has the following beneficial effects:

[0025] (1) The weightable super slow acid system provided by the present invention still has the resistance reduction capability after weighting, can effectively reduce the construction pressure and can be used for ultra-high temperature carbonate reservoir transformation.

[0026] (2) The super slow acid system provided by the present invention has low corrosion performance, which can reduce the damage of acid to the wellbore and ensure the safety of reservoir transformation operations.

[0027] (3) The super slow acid system provided by the present invention has an ultra-low acid-rock reaction rate and a good corrosion effect, and can be used for deep reservoir transformation.

[0028] (4) The super slow acid system provided by the present invention has high temperature resistance and can maintain a low corrosion rate under ultra-high temperature conditions to ensure the safety of the wellbore tubing. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a photograph of a P110 steel sheet before being corroded by the slow acid obtained in Example 1;

[0030] Figure 2 This is a photo of a P110 steel sheet corroded by the slow acid obtained in Example 1;

[0031] Figure 3 This is a photograph of a P110 steel sheet before being corroded by the slow acid obtained in Example 2;

[0032] Figure 4 This is a photo of a P110 steel sheet corroded by the slow acid obtained in Example 2;

[0033] Figure 5 This is a photo of marble before being corroded by the slow acid obtained in Example 1;

[0034] Figure 6 This is a photo of marble after being corroded by the slow acid obtained in Example 1;

[0035] Figure 7 This is a photo of marble before being corroded by the slow acid obtained in Example 2;

[0036] Figure 8 This is a photo of marble after being corroded by the slow acid obtained in Example 2;

[0037] Fig. 9 This is a photo of marble before being corroded by hydrochloric acid of the corresponding concentration of the slow acid obtained in Example 1;

[0038] Fig.10 This is a photo of marble corroded by hydrochloric acid of the corresponding concentration of the slow acid obtained in Example 1;

[0039] Fig.11 This is a photo of marble before being corroded by hydrochloric acid of the corresponding concentration of the slow acid obtained in Example 2;

[0040] Fig.12 This is a photograph of marble corroded by hydrochloric acid of the corresponding concentration of the slow acid obtained in Example 2.

[0041] The present invention is further described in detail below. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims. DETAILED DESCRIPTION

[0042] To better illustrate the present invention and facilitate understanding of the technical solution of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0043] This embodiment provides a slow-release acid for carbonate reservoirs, wherein the slow-release acid for carbonate reservoirs comprises an acid agent, a functional additive and water;

[0044] The acid agent includes an inorganic acid, an organic acid, a chelating agent and an organic ester in a mass ratio of 1:(10-13):(5-6):(3-4).

[0045] In the present invention, the acid agent includes an inorganic acid, an organic acid, a chelating agent and an organic ester in a mass ratio of 1:(10-13):(5-6):(3-4), for example, it can be 1:10:5:3, 1:11:5:3, 1:12:5:3, 1:10:6:3, 1:11:6:3, 1:12:3:3, 1:13:5:4, 1:10:6:4, 1:11:6:4 or 1:12:6:3, but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0046] In the present invention, the amount of water added can be selected according to the density of the desired slow acid.

[0047] Wherein, the inorganic acid includes one or a combination of at least two of hydrochloric acid, hydrofluoric acid, nitric acid or sulfuric acid.

[0048] Wherein, the organic acid comprises a combination of at least three of citric acid, malic acid, formic acid, acetic acid, aminosulfonic acid, tartaric acid, glutamic acid or oxalic acid.

[0049] In the present invention, by using a combination of multiple organic acids, the speed difference in the process of corroding the rock formation is achieved, so that the fast-reacting acid can react first to form a dominant channel, and the slow-reacting acid can go deeper, thus forming a deep transformation.

[0050] The chelating agent includes one or a combination of at least two of ethylenediaminetetraacetic acid, methylglycine diacetic acid, diethylenetriamine pentaacetic acid or 1,3-propylenediamine-N,N,N,N-tetraacetic acid.

[0051] The organic ester includes one or a combination of at least two of methyl formate, methyl acetate, methyl trifluoroacetate, methyl 2-bromopropionate, methyl thioglycolate or chloromethyl isopropyl carbonate.

[0052] Specifically, the slow-rate acid for carbonate reservoirs comprises, by weight, 10-25 parts of an acid agent, 0.2-22 parts of a functional additive and 50-70 parts of water.

[0053] Among them, the slow acid neutralizer for carbonate reservoirs is calculated in parts by weight as 10-25 parts, for example, it can be 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 18 parts, 20 parts, 22 parts, 24 parts or 25 parts, etc., but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0054] Among them, the functional additive for slow acid in carbonate reservoirs is calculated in parts by weight at 0.2-22 parts, for example, it can be 0.2 parts, 0.5 parts, 1 parts, 2 parts, 4 parts, 6 parts, 8 parts, 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts or 22 parts, but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0055] Among them, the slow acid water for carbonate reservoirs is calculated in parts by weight as 50-70 parts, for example, it can be 50 parts, 52 parts, 54 parts, 56 parts, 58 parts, 60 parts, 62 parts, 64 parts, 66 parts, 68 parts or 70 parts, but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0056] The functional additives include one or a combination of at least two of modified drag reducers, corrosion inhibitors or weighting agents. For example, depending on the usage scenario, one of the functional additives can be selected alone, such as a modified drag reducer, corrosion inhibitor or weighting agent, or a combination of two functional additives, such as a combination of a modified drag reducer and a corrosion inhibitor, or a combination of a corrosion inhibitor and a weighting agent, or a combination of a modified drag reducer and a weighting agent, or three functional additives, such as a combination of a modified drag reducer, a corrosion inhibitor and a weighting agent; the specific amount of addition can be selected based on the actual situation in the field, and the present invention exemplarily provides the following indicators of the amount of addition that can be used.

[0057] Specifically, the modified drag reducer in the functional additive is 0.2-0.5 parts by weight, for example, it can be 0.2 parts, 0.3 parts, 0.4 parts or 0.5 parts, but it is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0058] Specifically, the corrosion inhibitor in the functional additive is 2-5 parts by weight, for example, 2 parts, 3 parts, 4 parts or 5 parts, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0059] Specifically, the weighting agent in the functional additive is 14-16.5 parts by weight, for example, it can be 14 parts, 14.5 parts, 15 parts, 15.5 parts, 16 parts or 16.5 parts, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0060] Specifically, the modified drag reducer is copolymerized from acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), N,N'-dimethylacrylamide (DMAM) and N-dodecylacrylamide (DAM) by a step-by-step inverse emulsion polymerization method. The specific preparation process can refer to the prior art CN115725290A.

[0061] In the present invention, the molecular weight of the prepared modified drag reducer is 6-8 million.

[0062] Specifically, the corrosion inhibitor includes a Mannich base corrosion inhibitor, which can be a commercially available product or synthesized using existing technology, such as a corrosion inhibitor obtained by the synthesis process disclosed in CN115043822A.

[0063] Specifically, the weighting agent includes one or a combination of at least two of potassium chloride, potassium bromide, calcium chloride, calcium bromide, sodium sulfate, calcium sulfate, sodium formate or cesium formate.

[0064] Furthermore, the present invention provides a method for preparing the aforementioned retarding acid for carbonate reservoirs, which specifically comprises first mixing an aqueous solution of the acid agent and a corrosion inhibitor according to a formula, then performing a second mixing with a weighting agent, and then performing a third mixing with a modified drag reducer to obtain a retarding acid for carbonate reservoirs.

[0065] Among them, the purpose of mixing in the specific preparation process is to mix the components evenly. The stirring rate and stirring time in the mixing process can be selected according to the conventional requirements in the field. For example, the stirring rate of the first mixing is 300-400r / min, and the stirring time is 30-40min; the stirring rate of the second mixing is 200-400r / min, and the stirring time is 0.5-1.5h; the stirring rate of the third mixing is 400-600r / min, and the stirring time is 1-2h; at the same time, the aqueous solution of the acid agent is prepared according to the mass ratio of the formula and then mixed in water, and the mixing stirring rate is 300-400r / min, and the time is 20-30min.

[0066] Furthermore, the present invention provides a use of a slow-rate acid for a carbonate reservoir, specifically comprising using a slow-rate acid for a carbonate reservoir to perform a transformation operation on the carbonate reservoir.

[0067] In order to further illustrate the excellent effect of slow acid on carbonate reservoirs provided by the present invention, the following specific examples are provided:

[0068] The reagents used in the following examples are all commercially available reagents, wherein the modified drag reducer and corrosion inhibitor are prepared according to the prior art CN115725290A and CN115043822A, respectively.

[0069] Example 1

[0070] This embodiment provides a slow acid for carbonate reservoirs, and the specific preparation process is as follows:

[0071] (1) Add inorganic acid (hydrochloric acid), organic acid (citric acid, malic acid and formic acid in a mass ratio of 1:10:10), chelating agent (ethylenediaminetetraacetic acid) and organic ester (methyl acetate) in a mass ratio of 1:10:5:4 into a beaker containing 60 parts of deionized water to prepare an aqueous phase solution. Stir the mixture thoroughly in a 40°C water bath with a stirrer to fully dissolve the mixture, and prepare a super slow acid concentrated solution with a mass fraction of 40%;

[0072] (2) Take a certain amount of the above 40% super slow acid concentrated solution, add the corrosion inhibitor in a mass ratio of 98:2 and stir thoroughly at 40°C;

[0073] (3) adding deionized water to the solution obtained in step (2) at a mass ratio of 1:1 and stirring thoroughly;

[0074] (4) The solution obtained in step (3) was mixed with a designed density (1.7 g / cm 3 ) Add weighting agent and stir thoroughly;

[0075] (5) Adding a drag reducer to the solution obtained in step (4) at a mass ratio of 99.7:0.3 during stirring, and stirring the mixture thoroughly, the resulting liquid is a weightable super retarder acid.

[0076] Example 2

[0077] This embodiment provides a slow acid for carbonate reservoirs, and the specific preparation process is as follows:

[0078] (1) Add inorganic acid (hydrofluoric acid), organic acid (citric acid, malic acid, formic acid and acetic acid in a mass ratio of 1:1:2:4), chelating agent (methylglycine diacetic acid) and organic ester (methyl trifluoroacetate) in a mass ratio of 1:13:6:3 into a beaker containing 60 parts of deionized water to prepare an aqueous phase solution. Stir the mixture thoroughly in a 40°C water bath with a stirrer to fully dissolve the mixture, and prepare a super slow acid concentrated solution with a mass fraction of 40%;

[0079] (2) Take a certain amount of the above 40% super slow acid concentrated solution, add the corrosion inhibitor in a mass ratio of 98:2 and stir thoroughly at 40°C;

[0080] (3) adding deionized water to the solution obtained in step (2) at a mass ratio of 1:1 and stirring thoroughly;

[0081] (4) The solution obtained in step (3) was mixed with a designed density (1.5 g / cm 3 ) Add weighting agent and stir thoroughly;

[0082] (5) Adding a drag reducer to the solution obtained in step (4) at a mass ratio of 99.7:0.3 during stirring, and stirring the mixture thoroughly, the resulting liquid is a weightable super retarder acid.

[0083] Example 3

[0084] This embodiment provides a slow acid for carbonate reservoirs, and the specific preparation process is as follows:

[0085] (1) Add inorganic acid (nitric acid), organic acid (acetic acid, aminosulfonic acid, tartaric acid, glutamic acid, heat exchange oxalic acid in a mass ratio of 1:2:3:1:4), chelating agent (diethylenetriaminepentaacetic acid) and organic ester (isopropyl chloromethyl carbonate) in a mass ratio of 1:11:5:3 into a beaker containing 60 parts of deionized water to prepare an aqueous phase solution. Stir the mixture thoroughly in a 40°C water bath with a stirrer to fully dissolve the mixture, and prepare a super slow acid concentrated solution with a mass fraction of 40%;

[0086] (2) Take a certain amount of the above 40% super slow acid concentrated solution, add the corrosion inhibitor in a mass ratio of 98:2 and stir thoroughly at 40°C;

[0087] (3) adding deionized water to the solution obtained in step (2) at a mass ratio of 1:1 and stirring thoroughly;

[0088] (4) The solution obtained in step (3) was mixed with a designed density (1.3 g / cm 3 ) Add weighting agent and stir thoroughly;

[0089] (5) Adding a drag reducer to the solution obtained in step (4) at a mass ratio of 99.7:0.3 during stirring, and stirring the mixture thoroughly, the resulting liquid is a weightable super retarder acid.

[0090] Example 4

[0091] This embodiment provides a slow acid for carbonate reservoirs, and the specific preparation process is as follows:

[0092] (1) Add inorganic acid (sulfuric acid), organic acid (tartaric acid, glutamic acid and oxalic acid in a mass ratio of 1:3:5), chelating agent (1,3-propylenediamine-N,N,N,N-tetraacetic acid) and organic ester (methyl 2-bromopropionate) in a mass ratio of 1:12:6:4 into a beaker containing 60 parts of deionized water to prepare an aqueous phase solution. Stir the mixture thoroughly in a 40°C water bath with a stirrer to fully dissolve the mixture, and prepare a super slow acid concentrated solution with a mass fraction of 40%;

[0093] (2) Take a certain amount of the above 40% super slow acid concentrated solution, add the corrosion inhibitor in a mass ratio of 98:2 and stir thoroughly at 40°C;

[0094] (3) Add deionized water to the solution obtained in step 2 at a mass ratio of 1:1 and stir thoroughly;

[0095] (4) The solution obtained in step 3 was mixed according to the designed density (1.1 g / cm 3 ) Add weighting agent and stir thoroughly;

[0096] (5) Add drag reducer to the solution obtained in step 4 in a mass ratio of 99.7:0.3 during stirring, and stir thoroughly to obtain a liquid that is a weightable super retarder acid.

[0097] Comparative Example 1

[0098] The only difference from Example 1 is that the inorganic acid, ie, hydrochloric acid, is not added to the acid agent. At this time, the amount of water added is adaptively adjusted to ensure that the mass concentration of the solute in the solution remains unchanged.

[0099] Comparative Example 2

[0100] The only difference from Example 1 is that no organic acid, namely citric acid, malic acid and formic acid in a mass ratio of 1:1:1, is added to the acid agent. At this time, the amount of water added is adaptively adjusted to ensure that the mass concentration of the solute in the solution remains unchanged.

[0101] Comparative Example 3

[0102] The only difference from Example 1 is that no chelating agent, namely ethylenediaminetetraacetic acid, is added to the acid agent. At this time, the amount of water added is adaptively adjusted to ensure that the mass concentration of the solute in the solution remains unchanged.

[0103] Comparative Example 4

[0104] The only difference from Example 1 is that no organic ester, namely methyl acetate, is added to the acid agent. At this time, the amount of water added is adaptively adjusted to ensure that the mass concentration of the solute in the solution remains unchanged.

[0105] Comparative Example 5

[0106] The only difference from Example 1 is that the mass ratio of the inorganic acid, the organic acid, the chelating agent and the organic ester in the acid agent is 10:1:5:4.

[0107] Comparative Example 6

[0108] The only difference from Example 1 is that the mass ratio of the inorganic acid, the organic acid, the chelating agent and the organic ester in the acid agent is 1:10:4:5.

[0109] Comparative Example 7

[0110] The only difference from Example 1 is that the mass ratio of the inorganic acid, the organic acid, the chelating agent and the organic ester in the acid agent is 1:5:5:4.

[0111] Comparative Example 8

[0112] The only difference from Example 1 is that the organic acids are citric acid and malic acid in a mass ratio of 1:1.

[0113] The compatibility performance evaluation, weighting effect evaluation, and dissolution evaluation of the slow-acting acids obtained in Examples 1-4 and Comparative Examples 1-8 are as follows:

[0114] I. Compatibility performance evaluation

[0115] Take some of the slow acids prepared according to Examples 1-4 and Comparative Examples 1-8 and place them in beakers for 48 hours to observe the solution phenomenon. If there is no precipitation, stratification or crystal precipitation after 48 hours, the compatibility is good. Otherwise, the compatibility is not suitable. The specific results are shown in Table 1.

[0116] Table 1

[0117] precipitation Layering Crystal precipitation Compatibility Example 1 none none none qualified Example 2 none none none qualified Example 3 none none none qualified Example 4 none none none qualified Comparative Example 1 have none none Failure Comparative Example 2 none have none Failure Comparative Example 3 none none have Failure Comparative Example 4 none none none qualified Comparative Example 5 none none none qualified Comparative Example 6 none none none qualified Comparative Example 7 none none none qualified Comparative Example 8 none none none qualified

[0118] II. Evaluation of the aggravating effect

[0119] Some of the retarded acids prepared according to Examples 1-4 and Comparative Examples 1-8 were placed in beakers and the density of the system was measured at 20° C. using a HTD-300BH medium-high viscosity liquid density tester. The test results are detailed in Table 2.

[0120] Table 2

[0121] <![CDATA[System density / g / cm 3 > Example 1 1.7 Example 2 1.5 Example 3 1.3 Example 4 1.1 Comparative Example 1 1.7 Comparative Example 2 1.5 Comparative Example 3 1.3 Comparative Example 4 1.1 Comparative Example 5 1.7 Comparative Example 6 1.5 Comparative Example 7 1.3 Comparative Example 8 1.1

[0122] III. Dissolution evaluation

[0123] Specifically including: taking part of the slow acid prepared according to Examples 1-4 and Comparative Examples 1-8, referring to step 7.8.3 in SY 17814-2021 "Technical Specifications for Solid Acids for Acidification", the system temperature is 230°C, the dissolution time is 2h, and the results are detailed in Table 3.

[0124] Table 3

[0125]

[0126]

[0127] Furthermore, the dissolution of calcium carbonate was evaluated. Specifically, 50 g of slow acid was added to 10.00 g of dried calcium carbonate powder and reacted at 230° C. for 2 h. The results are shown in Table 4.

[0128] Table 4

[0129]

[0130]

[0131] Furthermore, the corrosion of P110 steel sheet was evaluated. Specifically, the steel was placed in slow acid and reacted at 230°C for 4 hours to measure the static corrosion rate. The results are shown in Table 5. Figure 1-Figure 4 The photos are of the corrosion of P110 steel sheet by slow acid before and after the corrosion of P110 steel sheet by slow acid in Example 1 and Example 2. There is no pitting corrosion, which indicates that the system has less corrosion to the material under high temperature conditions.

[0132] Table 5

[0133]

[0134]

[0135] Furthermore, the dissolution rate of marble was tested. Specifically, the marble was placed in slow acid at 25°C for 3 days for dissolution. For comparison, the marble was dissolved for 4 hours using hydrochloric acid of equal concentration to ensure the same solid-liquid ratio. The dissolution results are shown in Table 6. Among them, the hydrochloric acid of equal concentration has the same mass concentration as the slow acid neutralizer. Figure 5-Figure 12 These are comparison photos of marble before and after corrosion. Figure 5 This is a photo of the marble before being corroded by the slow acid obtained in Example 1. Figure 6 This is a photo of marble after being corroded by the slow acid obtained in Example 1. Figure 7 This is a photo of the marble before being corroded by the slow acid obtained in Example 2. Figure 8This is a photo of marble after being corroded by the slow acid obtained in Example 2. Fig. 9 This is a photo of the marble before being corroded by hydrochloric acid of the corresponding concentration of the slow acid obtained in Example 1. Fig.10 This is a photo of marble corroded by hydrochloric acid of the corresponding concentration of the slow acid obtained in Example 1. Fig.11 This is a photo of the marble before being corroded by hydrochloric acid of the corresponding concentration of the slow acid obtained in Example 2. Fig.12 This is a photograph of marble corroded by hydrochloric acid of the corresponding concentration of the slow acid obtained in Example 2. The system dissolves 47.81% of the marble in 3 days, and the hydrochloric acid dissolves 51.55% of the marble in 4 hours, indicating that the system has good deep penetration ability.

[0136] Table 6

[0137]

[0138]

[0139] From the above results, it can be seen that the slow-rate acid provided by the present invention realizes the high temperature resistance, low corrosion, high weighting, and low acid-rock reaction rate of the acid system for reservoir transformation, which can ensure the safe acid measures transformation of the wellbore pipe string under ultra-high temperature conditions, and realize the deep transformation of the acid in the reservoir under the support of low acid-rock reaction rate. Through the high drag reduction capacity after weighting, it is guaranteed to reduce the construction pressure during the deep well and ultra-deep well reservoir transformation process, thereby realizing efficient reservoir transformation capabilities.

[0140] It is stated that the present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0141] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0142] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0143] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A slow acid for carbonate reservoirs, characterized in that: The slow acid for carbonate reservoirs comprises an acid agent, a functional additive and water; The acid agent includes an inorganic acid, an organic acid, a chelating agent and an organic ester in a mass ratio of 1:(10-13):(5-6):(3-4).

2. The slow acid for carbonate reservoirs according to claim 1, characterized in that: The retarding acid for carbonate reservoirs comprises, by weight, 10-25 parts of an acid agent, 0.2-22 parts of a functional additive and 50-70 parts of water.

3. The slow acid for carbonate reservoirs according to claim 1 or 2, characterized in that: The inorganic acid includes one or a combination of at least two of hydrochloric acid, hydrofluoric acid, nitric acid or sulfuric acid.

4. The slow acid for carbonate reservoirs according to any one of claims 1 to 3, characterized in that: The organic acid comprises a combination of at least three of citric acid, malic acid, formic acid, acetic acid, aminosulfonic acid, tartaric acid, glutamic acid or oxalic acid.

5. The slow acid for carbonate reservoirs according to any one of claims 1 to 4, characterized in that: The chelating agent includes one or a combination of at least two of ethylenediaminetetraacetic acid, methylglycine diacetic acid, diethylenetriamine pentaacetic acid or 1,3-propylenediamine-N,N,N,N-tetraacetic acid.

6. The slow acid for carbonate reservoirs according to any one of claims 1 to 5, characterized in that: The organic ester includes one or a combination of at least two of methyl formate, methyl acetate, methyl trifluoroacetate, methyl 2-bromopropionate, methyl thioglycolate or chloromethyl isopropyl carbonate.

7. The slow acid for carbonate reservoirs according to any one of claims 1 to 6, characterized in that: The functional additive comprises one or a combination of at least two of a modified drag reducer, a corrosion inhibitor or a weighting agent.

8. The slow acid for carbonate reservoirs according to claim 7, characterized in that: The modified drag reducer in the functional additive is 0.2-0.5 parts by weight; Preferably, the corrosion inhibitor in the functional additive is 2-5 parts by weight; Preferably, the weighting agent in the functional additive is 14-16.5 parts by weight.

9. The slow acid for carbonate reservoirs according to claim 7 or 8, characterized in that: The modified drag reducer is prepared by copolymerizing acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, N,N'-dimethylacrylamide and N-dodecylacrylamide by a step-by-step inverse emulsion polymerization method; Preferably, the corrosion inhibitor comprises a Mannich base corrosion inhibitor; Preferably, the weighting agent comprises one or a combination of at least two of potassium chloride, potassium bromide, calcium chloride, calcium bromide, sodium sulfate, calcium sulfate, sodium formate or cesium formate.

10. A use of a slow acid for carbonate reservoirs as claimed in any one of claims 1 to 9, characterized in that: The use includes using slow-rate acid for carbonate reservoirs to transform carbonate reservoirs.

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