Solid mud acid system and preparation method thereof

Abstract

The invention discloses a solid mud acid system and a preparation method thereof. The solid mud acid system comprises solid hydrogen release acid, solid fluorine release acid and a solid acidification additive; the total mass of the solid hydrogen release acid and the solid fluorine release acid accounts for more than 60% of the total mass of the solid mud acid system, and the balance is the solid acidification additive. The solid mud acid system is solid powder particles which are stable under normal temperature and normal pressure conditions, when the solid mud acid system is used on site, 20-30% by mass of solid mud acid powder is directly diluted with fresh water and stirred for 10 min, and a solid mud acid solution can be obtained and used for plugging removal of an oil-water well in an oil field. The acidizing agent is used for acidizing construction of the offshore operation time and space limited platform, can replace an existing land solid acid system, has the advantages of being high in effective ingredient content, small in dosage, convenient to store and transport, easy to construct and the like, and can effectively solve the problem that conventional acidizing of the offshore operation time and space limited platform cannot be normally carried out.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield acidizing and plugging removal, and in particular to a solid soil acid system and a preparation method thereof. Background Art

[0002] Acidification and deblocking is a conventional measure to increase production and injection, and is widely used in various oil fields. Conventional acidification is mostly liquid acidification. Conventional liquid acidification construction equipment includes acidification pumps, acidification tanks, reagent tanks, etc. The construction site area is generally more than 100 square meters, and a professional acidification construction team is required. Considering construction safety, cross-operation is not allowed on site. For conventional acidification measures on offshore platforms, due to the limitations of platform construction time and space conditions, conventional acidification construction on some platforms with saturated operations cannot be carried out normally, which limits the efficient development of development wells that need to be deblocked. Offshore platforms urgently need to develop solid acid products and acidification technologies that have a small construction footprint, simple construction process, do not occupy the top operating deck, and can be cross-constructed with other operations.

[0003] In addition, some solid acid acidification technologies have been developed in onshore oil fields, such as solid acid esters, solid organic acids, solid nitric acid, solid autogenous acid, solid aminosulfonic acid and other technologies, but there are problems such as harsh acid release conditions, low acid release efficiency, low dissolution rate, and poor applicability to non-carbonate reservoirs. For example, solid acid esters and solid organic acids generally require high temperatures above 90°C to activate and release, and have low acid release efficiency. Solid nitric acid is highly corrosive, solid autogenous acid requires a two-liquid method for construction, and solid aminosulfonic acid has low acid generation efficiency and is prone to sulfate precipitation. The current solid acid system is basically not suitable for acidification of non-carbonate reservoirs, and more efficient and convenient solid acid products and technologies need to be developed on site.

[0004] There are currently no mature solid acid products and technologies for solid acid acidizing of non-high-temperature sandstone reservoirs. In particular, for small platforms with oversaturated operations in some offshore oil fields and limited construction space, there is an urgent need to develop solid soil acid acidizing technology suitable for sandstone reservoirs that is efficient in unblocking and simple in construction, to fill the research gap in this field. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a solid soil acid system and a preparation method, which are used for offshore sandstone reservoirs, especially for the normal implementation of acidizing measures on platforms with oversaturated operations and limited construction space. It can also be used for solid acid acidizing of terrestrial sandstone reservoirs. The system has the advantages of convenient product transportation and storage, simple preparation, high effective acid concentration, good unblocking effect and low construction requirements, solves the problem of the lack of solid soil acid system for sandstone reservoirs, and fills the technical gap in this field.

[0006] In a first aspect, the present invention provides a solid soil acid system, which is achieved by adopting the following technical solution.

[0007] A solid soil acid system comprises solid hydrogen-releasing acid, solid fluoride-releasing acid and a solid acidifying additive; the total mass of the solid hydrogen-releasing acid and the solid fluoride-releasing acid accounts for more than 60% of the total mass of the solid soil acid system, and the remainder is the solid acidifying additive.

[0008] Furthermore, the mass ratio of the solid hydrogen-releasing acid to the solid fluorine-releasing acid is (5-7.2):(1-2).

[0009] Furthermore, the preparation method of the solid hydrogen-releasing acid is as follows: add 2-4 times the volume of a precipitant to 1 times the volume of a hydrogen-releasing acid solution, drip an acid-binding agent under low temperature conditions until the precipitate no longer increases, stop dripping the acid-binding agent, and dry the precipitate to obtain solid hydrogen-releasing acid; the hydrogen-releasing acid solution uses HCl. Preferably, add 3 times the volume of a precipitant to 1 times the volume of a hydrogen-releasing acid solution. The solid hydrogen-releasing acid of the present application is a product obtained by solidifying liquid hydrogen-releasing acid. The solid hydrogen-releasing acid is a solid powder that is stable at room temperature and pressure. After being diluted with fresh water at room temperature, it is completely dissolved within 10 minutes, and the equivalent hydrochloric acid concentration of a 30wt% solid hydrogen-releasing acid solution is not less than 20%.

[0010] Furthermore, the preparation method of the solid fluorine-releasing acid is as follows: add 1-3 times the volume of a precipitant to 1 times the volume of a fluorine-releasing acid solution, drip an acid-binding agent under low temperature conditions until the precipitate no longer increases, stop dripping the acid-binding agent, and dry the precipitate to obtain solid fluorine-releasing acid; the fluorine-releasing acid solution uses HF. Preferably, add 2 times the volume of a precipitant to 1 times the volume of a fluorine-releasing acid solution. The solid fluorine-releasing acid of the present application is a product obtained by solidifying liquid fluorine-releasing acid. The solid fluorine-releasing acid is a solid powder that is stable at room temperature and pressure. After being diluted with fresh water at room temperature, it is completely dissolved within 10 minutes, and the equivalent hydrofluoric acid concentration of 30wt% solid fluorine-releasing acid is not less than 15%.

[0011] Furthermore, the low temperature is 0-5°C; the precipitant is anhydrous methanol and / or ≥95% ethanol; the acid binding agent is one or more of urea, fatty amine, hydrazine, and aromatic amine; and the drying method is vacuum filtration drying.

[0012] Furthermore, the solid acidifying additives are all solid powders or particles, and the solid acidifying additives include solid anti-water washing stabilizers, solid iron stabilizers, solid cationic surfactants, solid preservatives, solid anti-caking agents and solid organic phosphine chelating agents.

[0013] Furthermore, the solid anti-washing stabilizer is selected from one or more of ammonium chloride, potassium chloride, choline chloride, and polydiallyl dimethyl ammonium chloride, and the mass of the solid anti-washing stabilizer accounts for 1% to 3% of the total mass of the solid soil acid system;

[0014] The solid iron stabilizer is selected from one or more of citric acid, EDTA, HETDA, and sodium hexametaphosphate, and the mass of the solid iron stabilizer accounts for 1% to 3% of the total mass of the solid earth acid system;

[0015] The solid cationic surfactant is selected from one or more of octadecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, and dodecyltrimethylammonium chloride, and the mass of the solid cationic surfactant accounts for 0.1% to 1% of the total mass of the solid earth acid system;

[0016] The solid preservative is selected from one or more of propargyl alcohol, urotropine, and alkynol, and the mass of the solid preservative accounts for 2% to 4% of the total mass of the solid earth acid system;

[0017] The solid anti-caking agent is selected from one of potassium ferrocyanide, white carbon black, and cellulose nanocrystals, and the mass of the solid anti-caking agent accounts for 1% to 2% of the total mass of the solid soil acid system;

[0018] The solid organic phosphine chelating agent is selected from one of HEDP, NTA, ATMP, EDTMP and DTPMPA.

[0019] Specifically, a solid soil acid system includes the following components in mass percentage:

[0020] Solid release of hydrogen acid 50% to 72%;

[0021] Solid fluoride-releasing acid 10% to 20%;

[0022] Solid anti-washing stabilizer 1% to 3%;

[0023] Solid iron stabilizer 1% to 3%;

[0024] Solid cationic surfactant 0.1% to 1%;

[0025] Solid preservatives 2% to 4%;

[0026] Solid anticaking agent 1% to 2%;

[0027] The balance is solid organic phosphine chelating agent.

[0028] In a second aspect, the present invention provides a method for preparing a solid clay acid system, which is achieved by adopting the following technical scheme.

[0029] A preparation method of the above-mentioned solid earth acid system comprises the following steps: under low-temperature drying conditions, solid hydrogen-releasing acid, solid fluoride-releasing acid, solid water-resistant stabilizer, solid iron stabilizer, solid cationic surfactant, solid preservative, solid anti-caking agent and solid organic phosphine chelating agent are uniformly mixed according to a formula ratio and crushed to obtain a solid earth acid system.

[0030] The solid mud acid system of the present invention is a solid powder particle that is stable under normal temperature and pressure conditions. When used on site, the solid mud acid powder is directly diluted with fresh water at a mass percentage of 20% to 30% and stirred for 10 minutes to obtain a solid mud acid solution, which is used for unblocking oil and water wells in oil fields.

[0031] This application has the following beneficial effects.

[0032] (1) The present invention solidifies liquid fluoride-releasing acid for the first time, and cooperates with solid hydrogen-releasing acid and solid acidizing additives to form a solid soil acid product. The product can be widely used in sandstone reservoir blockage removal, filling the gap in solid soil acid acidizing technology in the industry;

[0033] (2) All components in the solid soil acid system of the present invention are solid powders with high content of effective ingredients. The solid powders are not acidic at room temperature and pressure, are easy to store and transport, and are highly safe. When used on site, the liquid soil acid system can be obtained by simply diluting and dissolving it in proportion with fresh water, which effectively saves storage and transportation costs. During the construction process, the acidification construction can be completed using small-scale stirring and online injection equipment, which has low requirements for construction space and is particularly suitable for acidification and deblocking of oversaturated platforms and small platforms in offshore oil field operations;

[0034] (3) The effective content of solid hydrochloric acid HCl in the solid soil acid system of the present invention can reach more than 65%, which is more than twice the concentration of conventional 31% industrial hydrochloric acid. The effective acid content is high, and the on-site dosage can be reduced by more than 1 time compared with liquid acid. After the solid hydrochloric acid is diluted in fresh water, HCl can be completely released. Different from liquid hydrochloric acid, the product storage, transportation and use are not regulated, and it is easy to use; compared with the currently used solid organic acids and organic acid esters, it does not require high temperature activation of more than 90°C to release acid; compared with the currently used solid aminosulfonic acid, the equivalent hydrochloric acid concentration of the saturated solution of solid aminosulfonic acid is about 6%, which is more than 1 times lower than the equivalent hydrochloric acid concentration of solid hydrochloric acid; compared with the currently used two-liquid method solid autogenous acid, solid hydrochloric acid can be constructed using the single-liquid method, and the construction process is simpler; compared with solid acid sticks, the scale dissolving and plugging removal performance is improved by more than 10 times;

[0035] (4) The principle of the present invention is reliable and the method is feasible. It effectively solves the problem of low effective acid content of liquid acid, especially liquid industrial hydrochloric acid. It cooperates with solid fluoride-releasing acid and solid acidifying additives to form a solid soil acid system with high effective content, small on-site usage, convenient storage and transportation, simple construction, and can complete acidification construction and achieve conventional acidification effect by using small online mixing and injection construction equipment without affecting other operations of the platform. It can also replace the currently used solid aminosulfonic acid and other inefficient solid acid products, and overcome the problems of conventional solid acid sandstone reservoirs being unsuitable or poorly applicable, and easily forming secondary damage such as calcium sulfate. The solid soil acid system of the present invention supplements the acidification product series in the industry and fills the technical gap in this field. DETAILED DESCRIPTION

[0036] The present patent application is further described below in conjunction with embodiments.

[0037] Unless otherwise specified, the experimental methods used in the following preparation examples and examples are all conventional methods; the materials, reagents, etc. used in the following preparation examples and examples are all commercially available unless otherwise specified.

[0038] Example 1

[0039] A method for preparing a solid clay acid system comprises the following steps:

[0040] Step 1: Add 100 mL of 37% HCl solution and 300 mL of anhydrous methanol into an acid-resistant sealed container under ice water stirring, and add hydrazine solution dropwise until the precipitate in the container no longer increases, and filter the precipitate by vacuum filtration with filter paper. After filtration, the precipitate is dried and crushed at low temperature to obtain a solid hydrogen-releasing acid powder.

[0041] Step 2: Under ice water stirring conditions, add 100 mL of 40% HF solution and 200 mL of anhydrous methanol into an acid-resistant sealed container, and add hydrazine solution dropwise until the precipitate in the container no longer increases, and filter the precipitate by vacuum filtration with filter paper. After filtration, the precipitate is dried and crushed at low temperature to obtain a solid hydrogen-releasing acid powder.

[0042] Step 3: Evenly mix the solid hydrogen-releasing acid, solid fluorine-releasing acid and solid acidifying additive powders according to the following mass percentages:

[0043]

[0044]

[0045] The mixture is crushed under low temperature drying conditions to obtain a solid clay acid system.

[0046] The performance test results of the solid clay acid system prepared by the above method are as follows:

[0047]

[0048] Note: The determination standards of montmorillonite dissolution rate and core powder dissolution rate refer to SY / T 5886 "Evaluation Method of Acidizing Working Fluid Performance";

[0049] The determination standard of surface tension refers to SY / T 5755 "Performance Evaluation Method of Discharge Aids for Fracturing Acidification";

[0050] The corrosion rate determination standard refers to SY / T5405 "Performance Test Methods and Evaluation Indicators for Acidification Corrosion Inhibitors".

[0051] Example 2

[0052] A method for preparing a solid clay acid system comprises the following steps:

[0053] Step 1: Under ice water stirring conditions, add 100 mL of 37% HCl solution and 300 mL of anhydrous ethanol into an acid-resistant sealed container, and add hydrazine solution dropwise until the precipitate in the container no longer increases, and filter the precipitate by vacuum filtration with filter paper. After filtration, the precipitate is dried and crushed at low temperature to obtain a solid hydrogen-releasing acid powder.

[0054] Step 2: Under ice water stirring conditions, add 100 mL of 40% HF solution and 200 mL of anhydrous ethanol into an acid-resistant sealed container, and add hydrazine solution dropwise until the precipitate in the container no longer increases, and filter the precipitate by vacuum filtration with filter paper. After filtration, the precipitate is dried and crushed at low temperature to obtain a solid hydrogen-releasing acid powder.

[0055] Step 3: Evenly mix the solid hydrogen-releasing acid, solid fluorine-releasing acid and solid acidifying additive powders according to the following mass percentages:

[0056]

[0057] The mixture is crushed under low temperature drying conditions to obtain a solid clay acid system.

[0058] The performance test results of the solid clay acid system prepared by the above method are as follows:

[0059]

[0060] Example 3

[0061] A method for preparing a solid clay acid system comprises the following steps:

[0062] Step 1: Under ice water stirring conditions, add 100 mL of 31% industrial hydrochloric acid and 300 mL of 95% industrial ethanol in an acid-resistant sealed container, and add hydrazine solution dropwise until the precipitate in the container no longer increases, and filter the precipitate with filter paper under vacuum. After filtration, the precipitate is low-temperature dried and crushed to obtain a solid hydrogen-releasing acid powder.

[0063] Step 2: Under ice water stirring conditions, add 100 mL of 40% industrial hydrofluoric acid and 200 mL of 95% industrial ethanol in an acid-resistant sealed container, and add hydrazine solution dropwise until the precipitate in the container no longer increases, and filter the precipitate by vacuum filtration with filter paper. After filtration, the precipitate is low-temperature dried and crushed to obtain a solid hydrochloric acid-releasing powder.

[0064] Step 3: Evenly mix the solid hydrogen-releasing acid and the solid acidifying additive powder according to the following mass percentages:

[0065]

[0066] The mixture is crushed under low temperature drying conditions to obtain a solid hydrogen acid releasing system.

[0067] The performance test results of the solid hydrogen-releasing acid system prepared by the above method are as follows:

[0068]

[0069] Step 4: Evenly mix the solid hydrogen-releasing acid, solid fluorine-releasing acid and solid acidifying additive powder according to the following mass percentages:

[0070]

[0071]

[0072] The mixture is crushed under low temperature drying conditions to obtain a solid clay acid system.

[0073] The performance test results of the solid clay acid system prepared by the above method are as follows:

[0074]

[0075] Step 5. Use solid acid online deblocking and injection skid and high-pressure injection skid (displacement 30 cubic meters / hour, maximum pumping pressure 20MPa) and other construction equipment. During the on-site construction, transport 5 tons of solid hydrogen-releasing acid system and 5 tons of solid soil acid system to the site, connect the wellhead construction pipeline, first use 3 tons of solid hydrogen-releasing acid system, according to the ratio of 1:3 to the mass ratio of fresh water, adopt the construction method of preparing and pumping at the same time to complete the pre-acid squeezing, then use 5 tons of solid soil acid system, according to the ratio of 1:3 to the mass ratio of fresh water, adopt the construction method of preparing and pumping at the same time to complete the main treatment acid squeezing, finally use 2 tons of solid hydrogen-releasing acid system, according to the ratio of 1:3 to the mass ratio of fresh water, adopt the construction method of preparing and pumping at the same time to complete the post-acid squeezing and complete the solid soil acid acidification construction.

[0076] In an offshore water injection well, the injection pressure at the wellhead before acidizing was 9.8 MPa, and the daily injection volume was 260 m 3 / d, using solid acid online plugging removal and injection skid and high-pressure injection skid for construction, squeezing and injecting 11 cubic meters of pre-acid (3 tons of solid hydrogen-releasing acid system diluted with 9 cubic meters of fresh water), squeezing and injecting 18 cubic meters of main treatment acid (5 tons of solid soil acid system diluted with 15 cubic meters of fresh water), squeezing and injecting 7.6 cubic meters of post-acid (2 tons of solid hydrogen-releasing acid system diluted with 6 cubic meters of fresh water). After squeezing and injecting, the wellhead was restored and the flow was turned on for normal water injection. The initial wellhead injection pressure after the measures was 0.8MPa, and the daily injection volume was 262m 3 / d, the effect of lowering blood pressure and increasing injection is significant.

[0077] In summary, the present invention realizes the solidification of liquid hydrogen-releasing acid and liquid fluoride-releasing acid. The solid soil acid system consists of solid hydrogen-releasing acid, solid fluoride-releasing acid and solid acidizing additives. The finished product is a solid powder that is stable under normal conditions and is easily soluble in water. The performance after dissolution in water is consistent with that of liquid soil acid. The product has the advantages of high effective acid concentration, convenient storage and transportation, simple construction, etc. It can effectively overcome the shortcomings of low acid production efficiency, harsh use conditions and unsuitability for sandstone reservoirs of existing solid acids. In combination with construction equipment such as solid acid online deblocking and injection skids and high-pressure injection skids, it can ensure the normal development of acidizing construction on offshore sandstone reservoir construction platforms with limited space and time. As an additional supplement to liquid acid acidification, it enriches the acidizing product series, fills the technical gap in the industry, and has great value for promotion and application.

[0078] The embodiments of this specific implementation method are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A solid soil acid system, characterized in that: It comprises solid hydrogen-releasing acid, solid fluoride-releasing acid and solid acidifying additive; the total mass of the solid hydrogen-releasing acid and solid fluoride-releasing acid accounts for more than 60% of the total mass of the solid earth acid system, and the remainder is the solid acidifying additive.

2. A solid soil acid system according to claim 1, characterized in that: The mass ratio of the solid hydrogen-releasing acid to the solid fluorine-releasing acid is (5-7.2):(1-2).

3. A solid soil acid system according to claim 1, characterized in that: The preparation method of the solid hydrochloric acid comprises: adding 2-4 times the volume of a precipitant to 1 times the volume of a hydrochloric acid solution, dripping an acid-binding agent under low temperature conditions until the precipitate no longer increases, stopping dripping the acid-binding agent, and drying the precipitate to obtain the solid hydrochloric acid; the hydrochloric acid solution is HCl.

4. A solid soil acid system according to claim 1, characterized in that: The preparation method of the solid fluoride-releasing acid comprises: adding 1-3 times the volume of a precipitant to 1 times the volume of a fluoride-releasing acid solution, dripping an acid-binding agent under low temperature conditions until the precipitate no longer increases, stopping dripping the acid-binding agent, and drying the precipitate to obtain the solid fluoride-releasing acid; the fluoride-releasing acid solution uses HF.

5. A solid soil acid system according to claim 3 or 4, characterized in that: The low temperature is 0-5°C; the precipitant is anhydrous methanol and / or ethanol ≥95%; the acid binding agent is one or more of urea, fatty amine, hydrazine and aromatic amine; and the drying method is vacuum filtration drying.

6. A solid soil acid system according to claim 1, characterized in that: The solid acidifying additive comprises a solid anti-water-washing stabilizer, a solid iron stabilizer, a solid cationic surfactant, a solid preservative, a solid anticaking agent and a solid organic phosphine chelating agent.

7. A solid soil acid system according to claim 6, characterized in that: The solid anti-water-washing stabilizer is selected from one or more of ammonium chloride, potassium chloride, choline chloride, and polydiallyldimethylammonium chloride, and the mass of the solid anti-water-washing stabilizer accounts for 1% to 3% of the total mass of the solid soil acid system; The solid iron stabilizer is selected from one or more of citric acid, EDTA, HETDA, and sodium hexametaphosphate, and the mass of the solid iron stabilizer accounts for 1% to 3% of the total mass of the solid earth acid system; The solid cationic surfactant is selected from one or more of octadecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, and dodecyltrimethylammonium chloride, and the mass of the solid cationic surfactant accounts for 0.1% to 1% of the total mass of the solid earth acid system; The solid preservative is selected from one or more of propargyl alcohol, urotropine, and alkynol, and the mass of the solid preservative accounts for 2% to 4% of the total mass of the solid earth acid system; The solid anti-caking agent is selected from one of potassium ferrocyanide, white carbon black, and cellulose nanocrystals, and the mass of the solid anti-caking agent accounts for 1% to 2% of the total mass of the solid soil acid system; The solid organic phosphine chelating agent is selected from one of HEDP, NTA, ATMP, EDTMP and DTPMPA.

8. A method for preparing the solid clay acid system according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: under low-temperature drying conditions, solid hydrogen-releasing acid, solid fluoride-releasing acid, solid water-resistant stabilizer, solid iron stabilizer, solid cationic surfactant, solid preservative, solid anti-caking agent and solid organic phosphine chelating agent are uniformly mixed according to a formula ratio and crushed to obtain a solid earth acid system.

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