Solid diverting acid and application thereof

Abstract

The invention provides solid diverting acid and application thereof. The solid diverting acid comprises the following components in parts by mass: 30-90 parts of high-solubility solid acid, 10-30 parts of a low-solubility solid diverting agent, 0.2-0.9 part of a powder drag reducer and 1-2 parts of a solid corrosion inhibitor. All the components of the solid diverting acid are solid, the solid diverting acid is convenient to transport, the using method is simple, and the problems that the carbonate reservoir is heterogeneous and high in reaction rate at high temperature can be effectively solved.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas field development, and in particular to a solid diverting acid and an application thereof. Background Art

[0002] Deep carbonate reservoirs have high temperatures and strong heterogeneity. Conventional acid is easy to enter high permeability layers or microcracks during acidizing or acid fracturing construction, and the acid reacts quickly with rocks at high temperatures, resulting in poor construction results. Hydrochloric acid-based acid is difficult to transport over long distances, and it is severely corrosive to tank trucks, liquid distribution tanks, petroleum equipment, etc. At present, the commonly used acid systems are gelled acid, cross-linked acid, diverting acid, and autogenous acid. Gelled acid and cross-linked acid are polymer-based retarded acids with high viscosity. After breaking the gel, they will block the pore throat and damage the reservoir. The applicable temperature of diverting acid is low, generally less than 140°C, and the diverting step difference is less than 15. Autogenous acid is easy to produce formaldehyde, which is not environmentally friendly, and the acid generation effect is poor when it is mixed unevenly. For deep high-temperature heterogeneous carbonate reservoirs, the existing acid systems have limitations such as poor temperature resistance, inconvenient transportation, and poor high-temperature diverting ability, which limits the effect of acidizing or acid fracturing transformation.

[0003] At present, the focus of research on the difficult problems of high-temperature slowdown and strong reservoir heterogeneity is the use of coated solid acid. Coated solid acid is a solid acid wrapped with a layer of film on the outside, which is controlled by the film to release hydrogen ions to achieve the purpose of slowing down. CN102533244B uses solid hydrochloric acid and citric acid as the core, and uses guar gum as a binder to make capsule slow-release acid, which is suitable for temperatures of 50 to 60°C. The solid acid described in CN110218559B is composed of amino acid salts, halogenated acid salts, polyaldehydes and inorganic ammonium salts. It relies on hydrolysis and reaction to generate acid to produce hydrogen ions. It is suitable for 180°C formations, but has poor acid production capacity.

[0004] Through the analysis of the above existing technologies, it can be seen that the main function of solid acid is to slow down and solve the problem of difficult on-site transportation, and the coating process is mainly used. However, the coating process will reduce the effective acid content of the solid acid, increase the cost, and make it impossible to use it on a large scale on site.

[0005] Therefore, the oil and gas field development field urgently needs a solid diversion acid with a simple preparation method and suitable for high temperature environments and carbonate rocks. Summary of the invention

[0006] In order to solve the above problems in the prior art, the present invention aims to provide a solid diverting acid and its application. The solid diverting acid components are all solid, easy to transport, simple to use, and can effectively improve the problems of heterogeneity of carbonate reservoirs and fast reaction rate at high temperature.

[0007] In order to achieve the above object, according to a first aspect of the present invention, a solid diversion acid is provided, which comprises the following components in parts by mass:

[0008] 30-90 parts of high-solubility solid acid, 10-30 parts of low-solubility solid diverter, 0.2-0.9 parts of powder drag reducer, 1-2 parts of solid corrosion inhibitor;

[0009] At 25° C., the solubility of the high-solubility solid acid in water is greater than 0.8 g / mL;

[0010] The low-solubility solid diverter is a low-solubility solid small molecule acid and / or a solid acidic polymer that is soluble in water and shows acidity after degradation. At 25° C., the solubility of the low-solubility solid diverter in water is less than 0.05 g / mL.

[0011] In some preferred embodiments of the present invention, the viscosity average molecular weight of the solid acidic polymer is in the range of 3000-100000.

[0012] The present invention uses a high-solubility solid acid as a main component and mixes a low-solubility solid diverter. The low-solubility solid diverter is in a solid form when injected and becomes an acidic liquid after degradation or dissolution over time. The proportioning of the present invention is also conducive to increasing the effective acid concentration in the diverter acid.

[0013] In application, after the low-solubility solid diverter reaches the crack, it blocks the crack and forces the subsequent acid to divert. After the diversion, as the reaction and production proceed, the dissolution equilibrium of the low-solubility solid acid shifts to the right, automatically dissolves or releases, and there is no secondary damage. At the same time, the high-solubility solid acid dissolved in situ will further acid-etch the temporarily blocked cracks and increase the transformation volume.

[0014] Different from traditional solid temporary plugging agents, liquid diverting acids and liquid retarding acids, the present invention is essentially a solid acid system that is easy to transport and store. The purpose of temporary plugging, diverting and high-temperature retarding is achieved by regulating the high-solubility solid acid and low-solubility solid diverting agent in the system.

[0015] Preferably, the solid diverting acid of the present invention comprises the following components in parts by mass:

[0016] 60-90 parts of high-solubility solid acid, 10-20 parts of low-solubility solid diverting agent, 0.3-0.8 parts of powder drag reducer, 1-2 parts of solid corrosion inhibitor.

[0017] In some preferred embodiments of the present invention, the high-solubility solid acid includes one or a combination of two or more of chloroacetic acid, hydroxylamine hydrochloride, oxalic acid, malonic acid, succinic acid, citric acid, glutaric acid, adipic acid, pimelic acid, and aminosulfonic acid.

[0018] In some preferred embodiments of the present invention, the low-solubility solid diverting agent includes one or a combination of two or more of nitrilotriacetic acid, polyglycolic acid, polylactic acid, and succinic anhydride.

[0019] In some preferred embodiments of the present invention, the powder drag reducer comprises polyacrylamide.

[0020] Preferably, the viscosity-average molecular weight of the polyacrylamide is 9 million to 11 million.

[0021] Preferably, the polyacrylamide is obtained by polymerizing acrylamide, cationic monomers, anionic monomers, and nonionic monomers under the action of an initiator. The detailed polymerization method is well known to those skilled in the art and will not be described in detail here.

[0022] In some preferred embodiments of the present invention, the solid corrosion inhibitor includes an organic solid corrosion inhibitor and / or an inorganic solid corrosion inhibitor. Preferably, the solid corrosion inhibitor includes one or a combination of two or more of benzaldehyde, acetaldehyde, coumarin, and arsenic trioxide.

[0023] According to another aspect of the present invention, there is also provided a diversion acid, which comprises the above-mentioned solid diversion acid and water. The mass ratio of the solid diversion acid to the water is 1:20 to 1:5.

[0024] In some preferred embodiments of the present invention, when preparing the steering acid, firstly, the high-solubility solid acid is mixed with water in a mass ratio of 1:20 to 1:5 to obtain a solid acid solution;

[0025] Secondly, the solid acid solution, the solid corrosion inhibitor and the powder drag reducer are mixed to obtain a first mixed solution;

[0026] Secondly, the first mixed solution is mixed with the low-solubility solid diverting agent to obtain the diverting acid.

[0027] Mixing the highly soluble solid acid with water first helps to avoid local supersaturation causing crystallization.

[0028] The solid corrosion inhibitor and the powder drag reducer can be added together to simplify the preparation steps; or the solid corrosion inhibitor can be added first and then the powder drag reducer to achieve a more favorable dispersion effect.

[0029] Preferably, the specific on-site use method includes mixing the high-solubility solid acid with water according to the use ratio in a liquid preparation tank, adding the solid corrosion inhibitor, and stirring evenly. During on-site construction, the low-solubility solid diverter and powder drag reducer are sucked into the sand mixing truck in real time, mixed online, and pumped into the well.

[0030] In the above preparation method, there is no specific requirement for the stirring speed, and the stirring speed will not affect the final system effect.

[0031] The present invention also provides application of the above-mentioned diverting acid in the development of carbonate reservoirs.

[0032] In some preferred embodiments of the present invention, the temperature of the carbonate reservoir is 140-200°C.

[0033] In some preferred embodiments of the present invention, the permeability difference of the carbonate reservoir is ≥50. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The effective acid content distribution diagram of the diverted acid of the examples of the present invention and the comparative examples at different temperatures is shown.

[0035] Figure 2 A comparison chart of the dynamic acid-rock reaction rates of the diverted acids of the embodiments of the present invention and the comparative examples at different temperatures is shown.

[0036] Figure 3 A comparison chart of the maximum diversion capabilities of the diverting acids of the embodiments of the present invention and the comparative examples is shown. DETAILED DESCRIPTION

[0037] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be construed as limiting the applicable scope of the present invention.

[0038] Example 1

[0039] This embodiment provides a divert acid and a preparation method thereof.

[0040] Calculated by weight, the solid diverting acid includes: 88 parts of high-solubility solid acid, 10 parts of low-solubility solid diverting agent, 0.5 parts of powder drag reducer, and 1.5 parts of solid corrosion inhibitor.

[0041] Among them, the high-solubility solid acid includes: 60% glutaric acid, 20% hydroxylamine hydrochloride, 10% succinic acid, and 10% citric acid. The low-solubility solid diverter is 100% nitrilotriacetic acid. The powder drag reducer is 30% hydrolyzed polyacrylamide and copolymer, and the viscosity-average molecular weight is about 12 million. The solid corrosion inhibitor is a mixture of benzaldehyde, acetaldehyde, coumarin, and arsenic trioxide (mass ratio is 2:6:1:1).

[0042] The preparation process of the steering acid of the present embodiment is as follows:

[0043] Add 80 parts by mass of water to the liquid preparation tank, add high-solubility solid acid and solid corrosion inhibitor under stirring, and stir until dissolved. Then add powder drag reducer under stirring, stir evenly, and no fish eyes are generated. Finally, add low-solubility solid diverter, mix evenly to obtain diverter acid prepared by all-solid components.

[0044] Example 2

[0045] This embodiment provides a divert acid and a preparation method thereof.

[0046] Calculated by weight, the solid diverting acid includes: 80 parts of high-solubility solid acid, 18 parts of low-solubility solid diverting agent, 0.9 parts of powder drag reducer, and 1.1 parts of solid corrosion inhibitor.

[0047] Among them, high-solubility solid acids include: 50% glutaric acid, 15% hydroxylamine hydrochloride, 15% succinic acid, 10% chloroacetic acid, and 10% citric acid. Low-solubility solid diverters are 50% nitrilotriacetic acid and 50% polyglycolic acid. Powder drag reducers are 30% hydrolyzed polyacrylamide and copolymers, with a viscosity-average molecular weight of about 12 million. Solid corrosion inhibitors are a mixture of benzaldehyde, acetaldehyde, coumarin, and arsenic trioxide (mass ratio is 2:5:2:1).

[0048] The preparation process of the steering acid in this embodiment is the same as that in Example 1.

[0049] Example 3

[0050] This embodiment provides a divert acid and a preparation method thereof.

[0051] Calculated by weight, the solid diverting acid includes: 73.5 parts of high-solubility solid acid, 25 parts of low-solubility solid diverting agent, 0.5 parts of powder drag reducer, and 1 part of solid corrosion inhibitor.

[0052] Among them, high-solubility solid acids include: 40% glutaric acid, 25% hydroxylamine hydrochloride, 20% chloroacetic acid, 10% succinic acid, and 5% aminosulfonic acid. Low-solubility solid diverters are 40% nitrilotriacetic acid, 40% polyglycolic acid, and 20% polylactic acid. Powder drag reducers are 30% hydrolyzed polyacrylamide and copolymers, with a viscosity-average molecular weight of about 12 million. Solid corrosion inhibitors are a mixture of benzaldehyde, acetaldehyde, coumarin, and arsenic trioxide (mass ratio is 1:7:1:1).

[0053] The preparation process of the steering acid in this embodiment is the same as that in Example 1.

[0054] Comparative Example 1

[0055] It is basically the same as Example 1, except that there is no low-solubility solid diverting agent in the solid diverting acid, and its original proportion is replaced by a high-solubility solid acid.

[0056] The diverting acid comprises: 98 parts of high-solubility solid acid, 0.5 parts of powder drag reducer, and 1.5 parts of solid corrosion inhibitor.

[0057] Among them, the high-solubility solid acid includes: 60% glutaric acid, 20% hydroxylamine hydrochloride, 10% succinic acid, and 10% citric acid. The powder drag reducer is 30% hydrolyzed polyacrylamide and copolymer, and the viscosity-average molecular weight is about 12 million. The solid corrosion inhibitor is a mixture of benzaldehyde, acetaldehyde, coumarin, and arsenic trioxide (mass ratio is 2:6:1:1).

[0058] The preparation process of the steering acid in this comparative example is the same as that in Example 1.

[0059] Comparative Example 2

[0060] It is basically the same as Example 1, except that there is no high-solubility solid acid in the solid diverting acid, and its original proportion is replaced by a low-solubility solid diverting agent.

[0061] The diverting acid includes: 98 parts of low-solubility solid diverting agent, 0.5 parts of powder drag reducer, and 1.5 parts of solid corrosion inhibitor. Among them, the low-solubility solid diverting agent is 100% nitrilotriacetic acid. The powder drag reducer is 30% hydrolyzed polyacrylamide and copolymer, and the viscosity-average molecular weight is about 12 million. The solid corrosion inhibitor is a mixture of benzaldehyde, acetaldehyde, coumarin, and arsenic trioxide (mass ratio is 3:5:1:1).

[0062] The preparation process of the steering acid in this comparative example is the same as that in Example 1.

[0063] Comparative Example 3

[0064] Calculated by weight, the solid diverting acid includes: 20 parts of high-solubility solid acid, 78 parts of low-solubility solid diverting agent, 0.5 parts of powder drag reducer, and 1.5 parts of solid corrosion inhibitor.

[0065] The high-solubility solid acid includes: 60% glutaric acid, 20% hydroxylamine hydrochloride, 10% succinic acid, and 10% citric acid. The low-solubility solid diverter is 100% nitrilotriacetic acid.

[0066] The preparation process of the steering acid in this comparative example is the same as that in Example 1.

[0067] For different embodiments and comparative examples, effective acid content, dynamic acid-rock reaction rate, and diversion ability tests were performed.

[0068] Test Example 1:

[0069] For the effective acid content test, the test steps are as follows:

[0070] Weigh m grams of solid steering acid (accurate to 0.0001 g) into a conical flask, add 30 mL of distilled water, and completely dissolve the sample;

[0071] Add 2 to 3 drops of phenolphthalein solution into the conical flask and shake well;

[0072] Transfer the sodium hydroxide solution into the rinsed alkaline burette and record the initial liquid level position;

[0073] While shaking the conical flask, drip the sodium hydroxide solution and observe the color change of the liquid in real time. Be careful not to drip too fast.

[0074] When the solution turns red and does not fade within half an hour, it indicates that the titration has reached the endpoint, and the volume V of the sodium hydroxide solution used is recorded;

[0075] The above process was repeated twice and the measurements were made three times to reduce the experimental error.

[0076] The effective acid content of the solid steering acid is converted into a percentage under HCl for easy comparison, specifically according to the following formula:

[0077]

[0078] W-effective acid content of solid diverting acid, expressed as a percentage

[0079] P-consumed NaOH solution volume, mL

[0080] c NaOH -NaOH solution molar concentration, mol / L

[0081] M-molar mass value of hydrochloric acid (36.5), g / mol

[0082] m-mass of solid diverted acid taken, g

[0083] The test results of effective acid content are as follows: Figure 1 As shown. The effective acid content is basically stable or slightly increases with temperature. In the examples, except for Example 3, which has an effective acid content of 49% at 25°C, the effective acid content of Example 3 at other temperatures and the effective acid content of other examples are all greater than 50%. Among the comparative examples, the effective acid content of Comparative Example 2 is the lowest, which indicates that the large-scale use of low-solubility solid diverting agents will reduce the effective acid concentration, so low-solubility solid diverting agents cannot be used as the main component for acid etching in carbonate reservoir reconstruction.

[0084] Test Example 2:

[0085] For the dynamic acid-rock reaction rate test, the test steps are as follows:

[0086] Use a thermoplastic tube to fix a mass mb The core is placed in the reaction container, 550 mL of the prepared solid diverting acid solution is injected into the liquid storage container, and the reaction container and the liquid storage container are heated to the specified temperature at the same time; after the acid in the liquid storage container is transferred to the reaction container by pressurizing at 1 MPa, the whole is pressurized to 7.5 MPa.

[0087] The speed was set to 800 rpm and the experiment was started. During the experiment, the pressure was ensured to be no less than 7.5 MPa.

[0088] After the experiment, the core was taken out and the surface was slowly cleaned with deionized water, and then placed in an oven at 105°C for 24 hours. The mass m was weighed. a .

[0089] The solid-to-acid dynamic acid-rock reaction rate is calculated according to the following formula:

[0090]

[0091] DR w -Solid-turned-acid dynamic acid-rock reaction rate, mol / (cm 2 ·s)

[0092] m b -Mass of core before reaction, g

[0093] m a -Mass of core after reaction, g

[0094] - Relative molecular weight of calcium carbonate, take 100g / mol

[0095] A-core surface area, cm 2

[0096] t-reaction time, s

[0097] - Core porosity, %

[0098] According to the above steps, the mass concentration of the diverting acid is 20%, and the gelling acid (KMS-G) and the cross-linking acid (KMS-C) with the same hydrogen ion concentration are used to compare the high-temperature dynamic acid-rock reaction rate. Figure 2As shown. The test results show that at 140°C, the acid-rock reaction rate of the diverting acid of the three embodiments is one order of magnitude lower than that of the gelling acid and cross-linking acid at the same temperature and acid concentration. When the temperature is raised to 180°C and 200°C, the reaction rates of the diverting acids provided in the embodiments are lower than those of the gelling acid and cross-linking acid at the same acid concentration of 140°C. This result shows that the solid diverting acid of the present invention is suitable for ultra-high temperature reservoir environments at 200°C. In the comparative examples, the reaction rate of the diverting acid of comparative example 1 is higher than that of example 1, and the diverting acid of comparative example 2 has the lowest reaction rate among all systems, so it can be proved that the low-solubility diverting agent has a certain effect of enhancing the slowing down. However, in comparative examples 2 and 3, due to the large amount of low-solubility solid diverting agents used, a large amount of white secondary precipitates appear at the bottom of the solution at the end of the reaction, so the amount of low-solubility solid diverting agent used needs to be strictly controlled in proportion.

[0099] Test Example 3:

[0100] For the steering ability test, the test steps are as follows:

[0101] Two cores with different permeabilities are selected, and the permeability difference is defined as the ratio of the permeability of the relatively high permeability core to the permeability of the relatively low permeability core.

[0102] The core was placed in a parallel acidifier and a confining pressure of 30 MPa was applied.

[0103] The equipment was heated to a specified temperature of 180°C.

[0104] The solid diverting acid in the above-mentioned embodiment and comparative example is injected into the two cores at the same time, and the transformation effect of the relatively low permeability core is used as the judgment standard for the success of diverting. When the permeability improvement rate of the relatively low permeability core exceeds 200%, it indicates that the diverting acid is successfully diverted and acidized under this permeability difference, and the maximum injection pressure at this time is the maximum plugging pressure.

[0105]

[0106] KI-relative permeability increase rate of low permeability core, %

[0107] K1-relatively low permeability core permeability before acidizing, mD

[0108] K2-relative low permeability core permeability after acidification, mD

[0109] The mass concentration of the solid diverting acid used is 20%. The diverting ability test results are as follows Figure 3As shown. By adjusting the low-solubility solid diverter component and proportion, the diverting capacity of the system can be adjusted. Under different low-solubility solid diverter components and proportions, the plugging pressure is different, the degradation or dissolution time is also different, and the plugging time can also be regulated accordingly. Under the three embodiments, the plugging pressure exceeds 18MPa, and the maximum diverting step difference exceeds 50. The diverting acid in Comparative Example 1 has no diverting ability, which shows the necessity of low-solubility solid diverters. The diverting ability of the diverting acid in Comparative Examples 2 and 3 is not greatly improved compared with the embodiments, and the construction is difficult when a large amount of low-solubility solid diverters are used, and the acid concentration is low, resulting in precipitation and contamination of the reservoir. This proves that it is necessary to determine the proportion of each component in the present invention.

Claims

1. A solid divert acid, characterized in that: In parts by mass, it includes the following components: 30-90 parts of high-solubility solid acid, 10-30 parts of low-solubility solid diverter, 0.2-0.9 parts of powder drag reducer, 1-2 parts of solid corrosion inhibitor; At 25° C., the solubility of the high-solubility solid acid in water is greater than 0.8 g / mL; The low-solubility solid diverter is a low-solubility solid small molecule acid and / or a solid acidic polymer that is soluble in water and shows acidity after degradation. At 25° C., the solubility of the low-solubility solid diverter in water is less than 0.05 g / mL.

2. The solid diverting acid according to claim 1, characterized in that: The high-solubility solid acid includes one or a combination of two or more of chloroacetic acid, hydroxylamine hydrochloride, oxalic acid, malonic acid, succinic acid, citric acid, glutaric acid, adipic acid, pimelic acid, and aminosulfonic acid.

3. The solid diverting acid according to claim 1, characterized in that: The low-solubility solid diverting agent includes one or a combination of two or more of nitrilotriacetic acid, polyglycolic acid, polylactic acid, and succinic anhydride.

4. The solid diverting acid according to claim 1, characterized in that: The viscosity average molecular weight of the solid acidic polymer is in the range of 3000-100000.

5. The solid diversion acid according to claim 1, characterized in that: The powder drag reducer includes polyacrylamide.

6. The solid diversion acid according to claim 1, characterized in that The solid corrosion inhibitor includes an organic solid corrosion inhibitor and / or an inorganic solid corrosion inhibitor.

7. A diverting acid, characterized in that The invention comprises the solid steering acid according to any one of claims 1 to 6 and water; the mass ratio of the solid steering acid to the water is 1:20 to 1:

5.

8. The diversion acid according to claim 7, characterized in that When preparing the steering acid, firstly, the high-solubility solid acid and water are mixed in a mass ratio of 1:20 to 1:5 to obtain a solid acid solution; Secondly, the solid acid solution, the solid corrosion inhibitor and the powder drag reducer are mixed to obtain a first mixed solution; Secondly, the first mixed solution is mixed with the low-solubility solid diverting agent to obtain the diverting acid.

9. Use of the diverting acid according to claim 7 or 8 in the development of carbonate reservoirs.

10. The use according to claim 9, characterized in that: The temperature of the carbonate reservoir is 20-200°C; And / or, the permeability difference of the carbonate reservoir is ≥50.

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