High-temperature slow-release authigenic acid system and use method thereof

Abstract

The invention discloses a high-temperature slow-release authigenic acid system and a use method thereof. The high-temperature slow-release authigenic acid system comprises the following components in percentage by mass: 1-5% of an oxidizing agent, 10-20% of polyglycolic acid resin and 75-85% of chlorinated polyvinyl chloride resin. The high-temperature slow-release authigenic acid and water or a carrying fluid containing a thickening agent are mixed according to the mass ratio of (3-4): 10 to prepare the high-temperature slow-release authigenic acid, the high-temperature slow-release authigenic acid can be used for deep stratum acidification, the preparation process is simple, no acid is generated under the normal-temperature condition, site construction is convenient, and the cost is low. And after being injected into the stratum, the chlorinated resin is promoted to hydrolyze at high temperature to release hydrochloric acid by utilizing the synergistic efficient catalysis and promotion effect of organic acid generated by hydrolyzing the oxidant and the polyester in the underground high-temperature environment, so that the controllable generation and release of the hydrochloric acid in the underground high-temperature environment are realized, and the deep stratum acidification is carried out. The high-temperature slow-release authigenic acid system is low in cost, environment-friendly and wide in application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield chemistry, and in particular to a high-temperature slow-release autogenous acid system and a use method thereof. Background Art

[0002] Acidizing is a widely used measure to increase production and injection in oil fields. It is to restore or improve the permeability of formation pores and fractures through the dissolution and corrosion of rock cements or blockages in formation pores and fractures by acid. The acid commonly used in the acidizing process is hydrochloric acid or a mixed acid with hydrochloric acid as the main component. With the rapid increase in demand for oil and natural gas energy and the increasing depletion of shallow oil and gas resources, deep oil and gas exploration and development has become an important way for the sustainable development of the oil industry in the future. Oil and gas exploration and development are constantly moving towards deep oil reservoirs, the formation temperature is getting higher and higher, and there are more and more high-temperature (≥150℃) wells. However, in high-temperature reservoirs, the conventional acid system reacts very quickly with the formation rock, the pipe column is severely corroded, the filtration loss is large, and the effective action distance of the acid is too short to reach the deep fractures or pores, which makes the traditional acidizing system based on hydrochloric acid extremely limited in the transformation effect of deep reservoirs.

[0003] In response to the above problems faced by the traditional hydrochloric acid-based acidizing system and to meet the stringent performance requirements of deep high-temperature reservoir acidizing, domestic and foreign researchers have carried out a large number of unconventional acid systems, mainly autogenous acid, thickened acid, emulsified acid and ground cross-linked acid, among which autogenous acid has incomparable characteristics of other acidic fluids. Autogenous acid is not acidic or weakly acidic on the ground, and it undergoes chemical reactions in high-temperature formations to generate acid on site, and the acid production is gradual, so that the acid-rock reaction speed is slowed down, which can effectively overcome the high-temperature deep well carbonate reservoir acid-rock reaction speed, solve the problem of short high-temperature acid fracturing distance, greatly improve the acidizing efficiency, and reduce the corrosion of pipelines and equipment. Therefore, autogenous acid is very suitable for high-temperature formations.

[0004] At present, autogenous acids mainly include autogenous acid systems based on hydrolysis of esters and anhydrides, autogenous acid systems based on aldehyde-ammonium reactions, and autogenous acid systems based on hydrolysis of chlorinated organics, such as the Chinese invention patent applications with publication numbers CN102899012A, CN103450872A, CN103805159A, CN108384529A, and CN 110903821A. Although these autogenous acids have made some progress in increasing the penetration distance and reducing pipeline corrosion, their application in deep underground high temperature (≥150°C) environments still faces many challenges. For example, the autogenous acid systems based on hydrolysis of esters and anhydrides not only have high raw material costs, but also the acids generated by hydrolysis are all organic acids with weak acidity, low acid corrosion ability for calcium carbonate, and easy generation of organic calcium salt precipitation. The widely studied and reported autogenous acid system based on aldehyde-ammonium reaction is based on the reaction of formaldehyde or polyformaldehyde with ammonium chloride to generate hydrochloric acid. However, the applicable temperature of this system is relatively low, and a large amount of acid is generated at 70°C or even at room temperature, so the delayed acid generation is poor, which is difficult to meet the acidification needs of high-temperature (≥150°C) oil reservoirs. In addition, aldehydes have high biological toxicity and are highly harmful to the health of construction workers and the surrounding environment. Currently reported autogenous acid systems based on hydrolysis of chlorinated organic matter mostly use chlorine-containing organic matter, such as halogenated hydrocarbons, halogenated alkanes, halogenated aromatic hydrocarbons, etc. These chlorinated organic matter have the disadvantages of high toxicity and poor environmental protection. Moreover, these halogenated hydrocarbons are immiscible with water and cannot be compatible with traditional sand-carrying fracturing systems. It is difficult to use the traditional injection method for formation construction, which brings great inconvenience to acidification operations and increases the difficulty of construction. Moreover, these small-molecule halogenated hydrocarbons have large filtration losses and are difficult to apply to deep oil reservoirs. Therefore, the development of a low-cost, environmentally friendly, slow-release autogenous acid system that is easy to construct under complex conditions of high temperature (≥150°C) in deep oil reservoirs is a technical difficulty and important challenge currently faced by both China and abroad. It has important significance and application value for the exploration and development of deep oil and gas resources. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a high-temperature slow-release autogenous acid system and a method of use. The present invention utilizes the synergistic and efficient catalytic and promoting effect of the oxidant and polyester hydrolysis to produce organic acid in the underground high-temperature (≥150°C) environment, promotes the high-temperature hydrolysis of the chlorinated resin to release hydrochloric acid, and realizes the controllable generation and release of hydrochloric acid in the underground high-temperature environment. The high-temperature slow-release acid system of the present invention can ensure that no or a small amount of acidic substances are released during the surface pumping process and in the initial stage of acidification, reduce the corrosion of pipelines and equipment, and increase the acid etching distance, significantly improving the acidification performance in the high-temperature (≥150°C) environment of deep formations.

[0006] In a first aspect, the present invention provides a high-temperature sustained-release autogenous acid system, which is achieved by adopting the following technical scheme.

[0007] A high-temperature slow-release autogenous acid system comprises the following components in percentage by mass: 1-5% oxidant, 10-20% polyglycolic acid resin and 75-85% chlorinated polyvinyl chloride resin.

[0008] By adopting the above technical scheme, polyester, oxidant and chlorinated resin are mixed in a certain proportion, and the obtained mixture is injected into the formation along with the carrying fluid. The synergistic and efficient catalytic and promoting effect of the oxidant and organic acid in the high-temperature underground environment can be utilized to promote the high-temperature hydrolysis of the chlorinated resin to release hydrochloric acid, thereby realizing the controllable generation and release of hydrochloric acid in the high-temperature underground environment.

[0009] Furthermore, the oxidant is potassium bromate or sodium bromate, preferably potassium bromate. The oxidant selected in the present application is stable under high temperature environment.

[0010] Furthermore, the molecular weight of the polyglycolic acid resin is 30,000 to 100,000, preferably 50,000; the particle size of the polyglycolic acid resin is less than 300 μm or is less than 300 μm after being crushed and sieved by a pulverizer.

[0011] Furthermore, the chlorine content of the chlorinated polyvinyl chloride resin is 60-72%, preferably 70-72%; the particle size of the chlorinated polyvinyl chloride resin is less than 300 μm or the particle size is less than 300 μm after being crushed and sieved by a crusher.

[0012] In a second aspect, the present invention provides a method for preparing a high-temperature sustained-release autogenous acid system, which is achieved by adopting the following technical scheme.

[0013] A method for preparing the high temperature sustained release autogenous acid system is to uniformly mix a specified amount of oxidant, polyglycolic acid resin and chlorinated polyvinyl chloride resin powders with a stirrer at room temperature to obtain the high temperature sustained release autogenous acid system.

[0014] In a third aspect, the present invention provides a method for using a high-temperature sustained-release autogenous acid system, which is achieved by adopting the following technical solution.

[0015] A method for using the high-temperature slow-release autogenous acid system is to mix the high-temperature slow-release autogenous acid system with a carrier fluid in a mass ratio of 3 to 4:10, inject the mixture into a formation, and deeply etch carbonate rocks by acidification induced by the high temperature of the formation.

[0016] Furthermore, the carrier fluid is water or an aqueous solution containing a thickener, and the amount of the thickener added is 0.1 to 0.5 wt %.

[0017] Furthermore, the thickener is guar gum or xanthan gum.

[0018] By adopting the above technical solution, adding a thickener to water can increase the suspension stability, and the experimental results show that the high-temperature slow-release autogenous acid system of the present invention has good compatibility with the commonly used thickening carrier liquid.

[0019] Furthermore, the stratum is a carbonate rock stratum with a depth of 5000 to 8000 m and a temperature of 150 to 180°C.

[0020] The present invention achieves the following beneficial effects.

[0021] (1) The high-temperature slow-release autogenous acid system of the present invention can be injected once, which greatly facilitates the on-site construction of oil fields;

[0022] (2) The high temperature slow release autogenous acid system of the present invention is suspended in a carrier liquid in the form of powder, which not only solves the problem of incompatibility between autogenous acid based on the hydrolysis of small molecular halogenated hydrocarbons and water systems, but also effectively solves the filtration loss problem faced by traditional liquid acidification systems;

[0023] (3) The high-temperature slow-release self-acid system of the present invention reacts slowly below 150°C, and generates acid significantly above 150°C, and the acid generation is relatively slow, with an acid generation time of more than 2 hours; at high formation temperatures (≥150°C), the acid generation rate of the system is significantly accelerated, so it is suitable for corrosion of carbonates in formations with a depth of 5000 to 8000m and a temperature of 150 to 180°C;

[0024] (4) The high-temperature slow-release autogenous acid system of the present invention has low corrosion to pipelines and does not require the addition of additional additives such as corrosion inhibitors and iron ion stabilizers;

[0025] (5) The high-temperature slow-release autogenous acid system of the present invention is dispersed in water to prepare an acidizing working solution, and the acidizing working solution is placed in a high-pressure closed hydrothermal autoclave with an excess of calcium carbonate cores. The dissolution rate of the calcium carbonate cores at 150 to 180° C. is used to investigate the speed and concentration of hydrochloric acid produced by the high-temperature slow-release autogenous acid system at different temperatures. The experimental results show that the capacity of the high-temperature slow-release autogenous acid system is equivalent to 7 to 12% hydrochloric acid when reacted at 150 to 180° C. for 2 to 6 hours, and the higher the temperature, the higher the concentration of effective hydrochloric acid produced. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a curve diagram of equivalent hydrochloric acid concentration at different temperatures for the high temperature sustained-release autogenous acid system of the present invention;

[0027] Figure 2 The figure is a curve diagram of the dissolution rate of the high temperature slow-release autogenous acid system and 12% hydrochloric acid on the calcium carbonate core. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be clearly and completely described below through specific implementation methods.

[0029] Example 1

[0030] Polyglycolic acid with a molecular weight of about 30,000 and chlorinated polyvinyl chloride with a chlorine content of about 60% were selected, crushed by a high-speed pulverizer, and sieved with a sieve with a mesh of 50 mesh to obtain polyglycolic acid resin powder and chlorinated polyvinyl chloride resin powder with a particle size of less than 300 μm. Subsequently, 85g of chlorinated polyvinyl chloride resin powder, 14g of polyglycolic acid resin powder and 1g of potassium bromate powder were weighed, and the above substances were placed in a blender and stirred for 10 minutes to obtain a high-temperature sustained-release autogenous acid sample.

[0031] Example 2

[0032] Polyglycolic acid with a molecular weight of about 50,000 and chlorinated polyvinyl chloride with a chlorine content of about 65% were selected, crushed by a high-speed grinder, and sieved with a sieve with a mesh of 50 mesh to obtain polyglycolic acid resin powder and chlorinated polyvinyl chloride resin powder with a particle size of less than 300 μm. Subsequently, 80g of chlorinated polyvinyl chloride resin powder, 15g of polyglycolic acid resin powder and 5g of sodium bromate powder were weighed, and the above substances were placed in a blender and stirred for 10 minutes to obtain a high-temperature sustained-release autogenous acid sample.

[0033] Example 3

[0034] Polyglycolic acid with a molecular weight of about 100,000 and chlorinated polyvinyl chloride with a chlorine content of about 72% were selected, crushed by a high-speed grinder, and sieved with a sieve with a mesh of 50 mesh to obtain polyglycolic acid resin powder and chlorinated polyvinyl chloride resin powder with a particle size of less than 300 μm. Subsequently, 75g of chlorinated polyvinyl chloride resin powder, 20g of polyglycolic acid resin powder and 5g of sodium bromate powder were weighed, and the above substances were placed in a blender and stirred for 10 minutes to obtain a high-temperature sustained-release autogenous acid sample.

[0035] Example 4

[0036] Polyglycolic acid with a molecular weight of about 50,000 and chlorinated polyvinyl chloride with a chlorine content of about 70% were selected, crushed by a high-speed pulverizer, and sieved with a sieve with a mesh of 50 mesh to obtain polyglycolic acid resin powder and chlorinated polyvinyl chloride resin powder with a particle size of less than 300 μm. Subsequently, 80g of chlorinated polyvinyl chloride resin powder, 17g of polyglycolic acid resin powder and 3g of potassium bromate powder were weighed, and the above substances were placed in a blender and stirred for 10 minutes to obtain a high-temperature sustained-release autogenous acid sample.

[0037] Example 5

[0038] Polyglycolic acid with a molecular weight of about 60,000 and chlorinated polyvinyl chloride with a chlorine content of about 72% were selected, crushed by a high-speed pulverizer, and sieved with a sieve with a mesh of 50 mesh to obtain polyglycolic acid resin powder and chlorinated polyvinyl chloride resin powder with a particle size of less than 300 μm. Subsequently, 85g of chlorinated polyvinyl chloride resin powder, 10g of polyglycolic acid resin powder and 5g of sodium bromate powder were weighed, and the above substances were placed in a blender and stirred for 10 minutes to obtain a high-temperature sustained-release autogenous acid sample.

[0039] 30g of the high-temperature sustained-release authiogenic acid samples prepared in Examples 1 to 5 were selected respectively, mixed with 100g of clean water and stirred to form a suspension. To ensure the stability of the suspension, 1g of xanthan gum thickener was added. After sufficient stirring and dissolution, a high-temperature sustained-release authiogenic acid system was obtained. 20mL of the configured high-temperature sustained-release authiogenic acid system was taken and placed in a hydrothermal reactor, and then a columnar calcium carbonate core was added to the reactor. The closed hydrothermal reactor was placed in an oil bath at 160°C for 6h and then taken out to study the dissolution of the calcium carbonate core at different reaction times. As shown in Table 1, the results show that the higher the chlorine content of the chlorinated polyvinyl chloride used, the greater the equivalent hydrochloric acid concentration, the smaller the molecular weight of the chlorinated polyvinyl chloride used, and the greater the equivalent hydrochloric acid concentration.

[0040] Table 1

[0041] High temperature slow release autogenous acid system Equivalent hydrochloric acid concentration (%) Example 1 6.8 Example 2 7.0 Example 3 7.5 Example 4 7.2 Example 5 7.8

[0042] Examples 6-10

[0043] Indoor preparation method of high temperature sustained release autogenous acid:

[0044] (1) Preparation of a high-temperature sustained-release autogenous acid sample with optimized formula: Polyglycolic acid with a molecular weight of about 50,000 and chlorinated polyvinyl chloride with a chlorine content of about 72% were selected, crushed by a high-speed pulverizer, and sieved with a sieve with a mesh of 50 mesh to obtain polyglycolic acid resin powder and chlorinated polyvinyl chloride resin powder with a particle size of less than 300 μm. Subsequently, a certain amount of chlorinated polyvinyl chloride resin powder, polyglycolic acid resin powder and potassium bromate powder were weighed, and the above substances were placed in a blender and stirred for 10 minutes to obtain a high-temperature sustained-release autogenous acid sample.

[0045] (2) Then, a certain amount of the high temperature sustained release autogenous acid sample was weighed, mixed with clean water and stirred thoroughly to form a suspension. To ensure the stability of the suspension, an appropriate amount of thickener was added, and after stirring and dissolving thoroughly, a high temperature sustained release autogenous acid system was obtained. The proportions of the components in Examples 6-10 are shown in Table 2.

[0046] Table 2

[0047]

[0048]

[0049] Performance test 1

[0050] The concentration of hydrochloric acid produced by the high temperature slow-release autogenous acid system prepared by the present invention at different temperatures was investigated. 20 mL of the high temperature slow-release autogenous acid system configured in Example 6 was taken and placed in a high pressure hydrothermal reactor, and then a columnar calcium carbonate core was added to the reactor. The closed hydrothermal reactor was placed in an oil bath pot with a set temperature for reaction for 6 hours. By studying the dissolution of the calcium carbonate core at different reaction temperatures, the equivalent hydrochloric acid concentration produced by the autogenous acid reaction for 6 hours was measured (with reference to the petroleum standard QSYXJ0040-2001 oil field acidizing fluid performance evaluation method), and the experimental results are shown in Table 3.

[0051] Table 3

[0052]

[0053] As can be seen from Table 2, the high temperature slow-release acid system of the present invention basically does not generate acidity below 150°C, and has almost no obvious dissolution effect on the calcium carbonate core, but begins to generate obvious acidity above 150°C, which can cause significant dissolution of the calcium carbonate core, and the higher the temperature, the greater the concentration of hydrochloric acid generated.

[0054] Performance test 2

[0055] The concentration of hydrochloric acid produced by the high-temperature slow-release autogenous acid system prepared by the present invention at different temperatures was investigated. 20 mL of the high-temperature slow-release autogenous acid system prepared in Example 7 was taken and placed in a high-pressure hydrothermal reactor, and then a columnar calcium carbonate core was added to the reactor. The closed hydrothermal reactor was placed in an oil bath pot with a set temperature for 4 hours. By studying the dissolution of the calcium carbonate core at different reaction temperatures, the equivalent hydrochloric acid concentration produced by the autogenous acid reaction for 4 hours was measured. The experimental results are shown in Table 4.

[0056] Table 4

[0057]

[0058] It can be seen from Table 3 that the high temperature slow-release acid system of the present invention basically does not generate acidity below 150°C, and has almost no obvious dissolution effect on the calcium carbonate core, but begins to generate obvious acidity above 150°C, which can cause significant dissolution of the calcium carbonate core, and the higher the temperature, the greater the concentration of hydrochloric acid generated.

[0059] Performance test 3

[0060] The concentration of hydrochloric acid produced by the high-temperature slow-release autogenous acid system prepared by the present invention at different temperatures was investigated. 20 mL of the high-temperature slow-release autogenous acid system prepared in Example 8 was taken and placed in a high-pressure hydrothermal reactor, and then a columnar calcium carbonate core was added to the reactor. The closed hydrothermal reactor was placed in an oil bath pot with a set temperature for 2 hours. By studying the dissolution of the calcium carbonate core at different reaction temperatures, the equivalent hydrochloric acid concentration produced by the autogenous acid reaction for 2 hours was measured. The experimental results are shown in Table 5.

[0061] Table 5

[0062]

[0063] It can be seen from Table 4 that the high temperature slow-release acid system of the present invention basically does not generate acidity below 150°C, and has almost no obvious dissolution effect on the calcium carbonate core, but begins to generate obvious acidity above 150°C, which can cause significant dissolution of the calcium carbonate core, and the higher the temperature, the greater the concentration of hydrochloric acid generated.

[0064] Performance test 4

[0065] The concentration of hydrochloric acid produced by the high-temperature slow-release autogenous acid system prepared by the present invention at different temperatures was investigated. 20 mL of the high-temperature slow-release autogenous acid system prepared in Example 10 was taken and placed in a high-pressure hydrothermal reactor, and then a columnar calcium carbonate core was added to the reactor. The closed hydrothermal reactor was placed in an oil bath pot with a set temperature for reaction for 6 hours. By studying the dissolution of the calcium carbonate core at different reaction temperatures, the equivalent hydrochloric acid concentration produced by the autogenous acid reaction for 6 hours was measured, and the experimental results are shown in Table 6.

[0066] Table 6

[0067]

[0068] It can be seen from Table 5 that the high temperature slow-release acid system of the present invention basically does not generate acidity below 150°C, and has almost no obvious dissolution effect on the calcium carbonate core. However, it begins to generate obvious acidity above 150°C, and can cause significant dissolution of the calcium carbonate core. Moreover, the higher the temperature, the greater the concentration of hydrochloric acid generated.

[0069] Performance test 5

[0070] The concentration of hydrochloric acid produced by the high-temperature slow-release autogenous acid system prepared by the present invention at different temperatures and different reaction times was investigated. 20 mL of the high-temperature slow-release autogenous acid system prepared in Example 9 was taken and placed in a hydrothermal reactor, and then a columnar calcium carbonate core was added to the reactor. The sealed hydrothermal reactor was placed in an oil bath pot with a set temperature and reacted for different time periods. The equivalent hydrochloric acid concentration produced by the autogenous acid was measured by studying the dissolution of the calcium carbonate core at different reaction times. The experimental results are shown in FIG. Figure 1 .

[0071] Depend on Figure 1 It can be seen that the high temperature sustained release acid system of the present invention basically does not produce acidity below 150°C, and begins to produce obvious acidity above 150°C, and the higher the temperature, the greater the concentration of hydrochloric acid produced. Figure 1 It can also be seen that the high-temperature sustained-release autogenous acid system prepared by the present invention also has a good sustained-release effect under high-temperature environment.

[0072] Performance test 6

[0073] The slow dissolution performance of the acid produced by the high-temperature slow-release autogenous acid system prepared by the present invention at 160°C on the calcium carbonate core was investigated. Take 20 mL of the high-temperature slow-release autogenous acid system prepared in Example 9 and place it in a hydrothermal reactor, and then add columnar calcium carbonate cores into the reactor. The closed hydrothermal reactor was placed in an oil bath at 160°C and taken out for different reaction times to study the dissolution of the calcium carbonate core at different reaction times. For comparison, the dissolution of the calcium carbonate core at room temperature with a 12% hydrochloric acid solution was also measured. The experimental results are shown in the figure. Figure 2 .

[0074] Depend on Figure 2 It can be seen that the high-temperature slow-release acid system of the present invention produces obvious acidity at 160°C, and as the reaction time increases, more hydrochloric acid is produced, and the dissolution of the calcium carbonate core is greater. The dissolution of the calcium carbonate core is a slowly controllable process, which is beneficial to the acidification of deep formations and prolongs the acidification action distance.

[0075] The embodiments described above are merely descriptions of preferred implementation modes of the present invention, and are not intended to limit the concept and scope of the present invention. Without departing from the design concept of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary engineering technicians in the field should fall within the protection scope of the present invention. The technical contents for which protection is sought in the present invention have been fully recorded in the technical requirements.

Claims

1. A high temperature sustained release autogenous acid system, characterized in that: The invention comprises the following components in percentage by mass: 1-5% of oxidant, 10-20% of polyglycolic acid resin and 75-85% of chlorinated polyvinyl chloride resin.

2. A high temperature sustained release autogenous acid system according to claim 1, characterized in that: The oxidant is potassium bromate or sodium bromate.

3. A high temperature sustained release autogenous acid system according to claim 1, characterized in that: The molecular weight of the polyglycolic acid resin is 30,000 to 100,000, and the particle size is less than 300 μm.

4. A high temperature sustained release autogenous acid system according to claim 1, characterized in that: The chlorine content of the chlorinated polyvinyl chloride resin is 60-72%, and the particle size is less than 300 μm.

5. A method for using the high temperature sustained-release autogenous acid system according to any one of claims 1 to 4, characterized in that: The high-temperature slow-release autogenous acid system is mixed with a carrier fluid in a mass ratio of 3 to 4:10, and injected into the formation, so as to deeply etch the carbonate rock by inducing acid generation through the high temperature of the formation.

6. The method of use according to claim 5, characterized in that: The carrier fluid is water or an aqueous solution containing a thickener, and the amount of the thickener added is 0.1-0.5 wt %.

7. The method of use according to claim 6, characterized in that: The thickener is guar gum or xanthan gum.

8. The method of use according to claim 5, characterized in that: The stratum is a carbonate rock stratum with a depth of 5000 to 8000 m and a temperature of 150 to 180° C.

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