High-temperature carbonate reservoir thickening acid liquid system and preparation method thereof

Abstract

The invention belongs to the technical field of oil and gas field exploitation, and discloses a high-temperature carbonate reservoir thickening acid liquid system and a preparation method. The thickening acid liquid system comprises 10-30% of acid liquid, 0.05-3% of a high-temperature-resistant thickening agent, 0.005-0.05% of a high-temperature stabilizer, 0.5-3.5% of a retarder, 1-6% of a corrosion inhibitor, 0.5-2.5% of a corrosion inhibition synergist, 0.5-3.5% of an iron ion stabilizer, 3-10% of a cosolvent, 0.5-3.5% of a discharge aiding agent and the balance of water; the high-temperature-resistant thickening agent comprises the following components in percentage by weight: 0.5-2.5% of a central agent, 5-20% of a flowable agent, 0.05-1.5% of an inner net polymer, 10-60% of a monomer, 0.01-0.2% of an initiator and the balance of water. The thickening acid liquid system is good in high-temperature stability, the acid-rock reaction speed is obviously lower than that of common thickening acid, and the thickening acid liquid system has good retarding performance, high resistance reduction rate and high flowability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oil and gas field exploitation, and more particularly relates to a high-temperature carbonate reservoir thickened acid liquid system and a preparation method. BACKGROUND

[0002] The purpose of carbonate reservoir acidification is to form acid-etched holes and acid-etched cracks by dissolving formation minerals, to dredge oil and gas seepage channels, and to obtain high-speed channels for oil and gas seepage. Deep carbonate reservoirs generally have characteristics such as deep burial, high temperature, high pressure, high fracture pressure, and developed fractures, and the application of conventional acidification acid liquid systems faces many challenges. In order to delay the acid-rock reaction speed under high temperature conditions and reduce acid liquid filtration, a thickening agent, a surfactant, an emulsifier, or a crosslinking agent is often added to increase the viscosity of the acid liquid to achieve the purpose of slowing down. Typical examples include thickened acid (gelled acid), crosslinked acid, emulsified acid, and surfactant acid. Selecting a suitable acid liquid system to reduce the acid-rock reaction speed, reduce high-temperature corrosion, reduce friction, reduce filtration, and reduce reservoir damage is one of the key technologies for improving the acidification effect of high-temperature carbonate reservoirs. Crosslinked acid is difficult to break, and after breaking, there are many polymer residues, which cause secondary damage to the reservoir. Emulsified acid is sensitive to formation salinity and temperature, and has high friction, which limits the injection displacement of the acid liquid. Surfactant acid is not resistant to high temperature, and the amount of surfactant added is large, which results in high cost. Gelled acid is a non-crosslinked high-molecular polymer (thickening agent) added to a conventional acid system, which greatly increases the viscosity of the acid liquid to achieve the purpose of reducing the acid-rock reaction speed and acid liquid filtration. In addition, a small amount of linear polymer molecules are added, which have the effect of reducing friction. It is one of the most widely used acid liquid systems at home and abroad.

[0003] At present, thickening agents for thickened acid mainly include synthetic polymer and biopolymer (natural polymer). Because synthetic polymer thickening agents have good temperature resistance, many scholars have studied them more. Although existing synthetic polymer and natural polymer thickening agents can effectively increase the viscosity of the acid liquid, the natural polymer thickening agent contains a large amount of biological residues after breaking, which can easily cause acid-etched crack damage and affect the acidification effect. In addition, the molecular chains of natural polymers such as guar gum and other polymers shrink and even separate in the acid liquid, which seriously affects the performance of the acid liquid; synthetic polymer thickening agents have good high-temperature resistance and require a small amount of addition, but the synthesis process is complex, the cost is high, the shear stability is poor, and there are still many insoluble colloids after breaking, which can easily carbonize under high temperature and cause reservoir damage.

[0004] Overall, the problems of poor high-temperature stability and high friction of these thickened acids have not been solved, which limits their application in the acidification and reconstruction of high-temperature deep carbonate reservoirs, and the performance of acid liquid thickening agents still needs to be further improved. Therefore, developing a high-temperature carbonate reservoir thickened acid liquid system with good high-temperature stability, fluidity, low friction, and low damage characteristics is still one of the problems to be solved in the field. SUMMARY

[0005] The present application aims at the deficiencies of the prior art and provides a high-temperature carbonate reservoir thickened acid liquid system and a preparation method.

[0006] To achieve the above-mentioned purpose, the present application provides a high-temperature carbonate reservoir thickened acid liquid system, which comprises, based on the total weight of the thickened acid liquid system, 10-30% acid liquid, 0.05-3% high-temperature resistant thickening agent, 0.005-0.05% high-temperature stabilizer, 0.5-3.5% retarder, 1-6% corrosion inhibitor, 0.5-2.5% corrosion inhibitor synergist, 0.5-3.5% iron ion stabilizer, 3-10% cosolvent, 0.5-3.5% cleanup agent, and the rest is water.

[0007] The high-temperature resistant thickening agent comprises, based on the total weight of the high-temperature resistant thickening agent, 0.5-2.5% central agent, 5-20% flow agent, 0.05-1.5% internal network polymer, 10-60% monomer, 0.01-0.2% initiator, and the rest is water.

[0008] The flow agent is at least one of tributyl citrate, isoamyl citrate and trioctyl citrate.

[0009] According to the present application, preferably, the temperature of the high-temperature carbonate reservoir is 120-240℃.

[0010] According to the present application, preferably, the acid liquid is at least one of hydrochloric acid, acetic acid, formic acid and oxalic acid. Since the purpose of carbonate reservoir acidification is to form acid-etched holes and acid-etched seams by dissolving formation minerals, to dredge oil and gas seepage channels and to obtain high-speed oil and gas seepage channels. Therefore, the conventional acid liquid is economical, effective and most suitable.

[0011] According to the present application, preferably, the high-temperature stabilizer is at least one of N,N'-methylenebisacrylamide, ethyleneimine and polycarbodiimide.

[0012] In the present application, the high-temperature stabilizer is preferably N,N'-methylenebisacrylamide (MBAM). Carbonate reservoir acidification is beneficial to the thickened acid to achieve two purposes, the first is to reduce the friction loss required in the wellbore during injection, and the second is to reduce the H +The mass transfer rate is reduced, and the acid-rock reaction rate is reduced. However, it is an indisputable fact that the high-temperature polymer chain is broken, the high-temperature stabilizer can strengthen the tension between molecules to improve the temperature resistance of the acid liquid system, and after the chain is broken, a relatively small gel group exists, instead of a dilute acid liquid with completely broken polymer chains, thereby helping the acid liquid system to adapt to a higher temperature formation environment.

[0013] According to the present application, preferably, the retarder is at least one of dodecyl trimethyl ammonium chloride, tetradecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium chloride, octadecyl trimethyl ammonium chloride, oleic acid, and sodium oleate. In the present application, a big difficulty in high-temperature carbonate reservoir acidification is that the acid-rock reaction rate is too fast, which easily leads to the fact that the acid liquid is completely consumed in the near wellbore zone, and therefore, the chemical substance (the retarder) that can be adsorbed on the surface of the carbonate reservoir mineral is selected, which can effectively reduce the contact area between the acid liquid and the rock and reduce the acid-rock reaction rate.

[0014] According to the present application, preferably, the corrosion inhibitor is a high-temperature acid pickling corrosion inhibitor and / or an acidification corrosion inhibitor; further preferably, the corrosion inhibitor is at least one of aldehyde ketone amine condensate, acetylenic alcohol, thiourea, and imidazoline derivative.

[0015] According to the present application, preferably, the corrosion synergist is at least one of nano silicon dioxide, nano titanium oxide, and diantimony trioxide.

[0016] According to the present application, preferably, the iron ion stabilizer is at least one of citric acid, EDTA, NTA, DTPA, and HEDP.

[0017] According to the present application, preferably, the cosolvent is at least one of acetone, ethanol, methanol, isopropyl alcohol, propanol, ethylene glycol, and benzyl alcohol.

[0018] According to the present application, preferably, the cleanup agent is a fluorocarbon surfactant and / or a fluorosilicon surfactant.

[0019] According to the present application, preferably, the high-temperature resistant thickening agent comprises, based on the total weight of the high-temperature resistant thickening agent: 0.5-2.5% of a central agent, 11-20% of a flow agent, 0.05-1.5% of an internal network polymer, 10-60% of a monomer, 0.01-0.2% of an initiator, and the rest is water.

[0020] According to the present application, preferably, the central agent is at least one of citric acid fatty acid glyceride, glycerol stearate, and polyoxyethylene sorbitan monooleate.

[0021] According to the present application, preferably, the inner network polymer is at least one of xanthan gum, cellulose, modified cellulose, guanidine gum and modified guanidine gum. In the present application, the role of the inner network polymer is that the inner network polymer is first broken at high temperature, acting as a sacrificial agent, the mechanism of which is that the double-network wound inner network can reduce the stretching state of the outer network during injection, thereby realizing the effect of the buffer stretching segment of the outer network after temperature rise, and after the inner network is broken, locally holding the outer network to realize the temperature resistance effect of the gelled acid system.

[0022] According to the present application, preferably, the monomer is at least one of acrylamide (AM), 2-acrylamido-2-methylpropane sulfonic acid (AMPS), acryloyloxyethyl trimethyl ammonium chloride, octadecyl methacrylate and dodecyl methacrylate.

[0023] According to the present application, preferably, the initiator is at least one of potassium persulfate, ammonium persulfate and sodium sulfite.

[0024] In the present application, the flow agent is a key agent for the performance of the synergistic system. First, the gel or weak gel state of the polymer system of the gelled acid system formed by covalent bond, hydrogen bond and other forces is easy to cause injection difficulty and also easy to cause polymer chain breakage, and the flow agent can increase the lubricating effect of the gelled acid system to make the gelled acid system easy to flow, thereby reducing the injection difficulty. Second, the flowability of the flow agent in the whole gelled acid system can effectively improve the self-assembly performance of the gelled acid system to improve the high-temperature stability of the gelled acid system. Third, the flow agent is a small molecule, the molecular structure of which will not be destroyed at the formation temperature and has stability, and meanwhile, the flowability of the flow agent can be accelerated with the increase of temperature, thereby improving the self-repairing function of the gelled acid system.

[0025] According to the present application, preferably, the high-temperature resistant thickening agent is a double-network polymer high-temperature resistant thickening agent, and the preparation method of the high-temperature resistant thickening agent comprises the following steps:

[0026] (1) Preparation of inner network

[0027] The water and the central agent are mixed, the pH of the mixed system is adjusted to 7-8, and the mixed system is heated and stirred uniformly to obtain a stirring system; the stirring system, the flow agent and the inner network polymer are sequentially and uniformly stirred and mixed to obtain an inner network solution;

[0028] (2) Preparation of high-temperature main agent outer network

[0029] The inner network solution and the monomer are stirred and mixed, and nitrogen is introduced to remove oxygen while stirring; the cooling liquid and the initiator are stirred and mixed, nitrogen is introduced to remove oxygen while stirring, and the temperature is raised and reacted under the condition of continuous nitrogen introduction to obtain the high-temperature resistant thickening agent.

[0030] According to the present application, preferably, in step (1):

[0031] The pH of the mixed system is adjusted to 7-8 using an aqueous sodium hydroxide solution.

[0032] The temperature of the heated stirring is 50-60 DEG C.

[0033] According to the present application, preferably, in step (2): the temperature of the reaction is 60-65 DEG C, and the time is 5-10 h.

[0034] Another aspect of the present application provides a preparation method of the high-temperature carbonate reservoir thickened acid liquid system, and the preparation method comprises the following steps:

[0035] S1: mixing and stirring the acid liquid, the cosolvent and water uniformly to obtain a first mixture;

[0036] S2: mixing and stirring the first mixture and the corrosion inhibition synergist uniformly to obtain a second mixture;

[0037] S3: mixing and stirring the first mixture, the second mixture, the corrosion inhibitor, the retarder, the iron ion stabilizer, the cleanup agent and the high-temperature stabilizer uniformly to obtain a third mixture;

[0038] S4: mixing and stirring the third mixture and the high-temperature thickening agent uniformly to obtain the high-temperature carbonate reservoir thickened acid liquid system.

[0039] In the present application, steps S1-S4 are carried out at the ground normal temperature, and after the high-temperature carbonate reservoir thickened acid liquid system is prepared, the high-temperature carbonate reservoir thickened acid liquid system is directly injected into the target reservoir.

[0040] The present application has the following beneficial effects:

[0041] The double-network structure of the high-temperature thickening agent of the present application can improve the strength and stability of the gel system, and thus is widely used in various industries, including the petroleum related field. However, the application in high-temperature deep wells is limited because of the long well section and large injection friction, so that the high-viscosity acid liquid is difficult to inject. The thickened acid liquid system of the present application has improved temperature resistance because of the double-network structure. Meanwhile, the flow agent has a similar effect of "plasticizer", so that the high-viscosity system has good fluidity, and can be effectively used in the acidizing operation of high-temperature deep wells. The double-network structure will also be destroyed at high temperature, and the present application introduces the high-temperature thickened acid system with easy injection and multiple synergistic effects of flow enhancement and high-temperature self-repairing function mechanism on the basis of the double-network structure. The high-temperature resistance and easy injection mechanism includes:

[0042] (1) The dual-network structure and high-temperature stabilizer can improve the stability of the spatial network through non-covalent interaction, which can effectively improve the temperature resistance of the system. Compared with the conventional hydrophobic associative thickened acid system, it can improve the temperature resistance by 80℃ and can be applied to high-temperature deep wells above 220℃.

[0043] (2) In high-temperature deep wells, acid injection is difficult due to the long well sections, especially for double-network or cross-linked systems due to high friction. Therefore, stable viscosity and high friction are inherent characteristics of high-viscosity systems, making cross-linked and double-network systems unsuitable for high-temperature deep wells. The introduction of a flow agent effectively improves the system's fluidity through a mechanism similar to a plasticizer, thereby reducing the friction of the acid system and enabling the application of double-network acid in high-temperature deep wells. The synergistic effect of the flow agent and the double-network structure facilitates injection of the gel system while effectively reducing the acid-rock reaction rate and increasing the acid penetration distance by reducing filtration loss.

[0044] (3) High temperature accelerates the movement of the fluid in the system, while the hydrophobic association between the fluid and the double network structure can realize the system destruction-reassembly process and maintain the high temperature stability of the acid system.

[0045] (4) After the flow agent is injected into the formation, it forms a multi-layered organic adsorption layer on the rock surface through intermolecular self-assembly and the retarder, thereby reducing H + The probability of contact with rocks is reduced, effectively lowering the acid-rock reaction rate.

[0046] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0047] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of the invention.

[0048] Figure 1 The diagram shows a high-temperature shear test of a thickened acid system for a high-temperature carbonate reservoir provided in Embodiment 1 of the present invention.

[0049] Figure 2 The diagram shows a high-temperature shear test of a thickened acid system for a high-temperature carbonate reservoir provided in Embodiment 2 of the present invention.

[0050] Figure 3 The diagram shows a high-temperature shear resistance test of a thickened acid system for a high-temperature carbonate reservoir provided in Embodiment 3 of the present invention.

[0051] Figure 4 The diagram shows the temperature shear resistance test of a high-temperature carbonate reservoir thickened acid system provided in Embodiment 4 of the present invention.

[0052] Figure 5 The diagram shows a high-temperature shear test of a thickened acid system for a high-temperature carbonate reservoir provided in Comparative Example 1 of the present invention. Detailed Implementation

[0053] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0054] In the following embodiments:

[0055] The concentration of hydrochloric acid is 15%;

[0056] The corrosion inhibitor is a complex of thiourea and an imidazoline derivative (thiourea and imidazoline derivative in a mass ratio of 3:7, prepared by simple mixing of the two). The corrosion inhibitor exhibits a dynamic corrosion rate ≤100 g / (m²) at 220°C. 2 •h), which belongs to the first level specified in the industry standard "SY / T5405-1996 Test Methods and Evaluation Indicators for Performance of Corrosion Inhibitors for Acidification";

[0057] The fluorocarbon surfactant is DuPont Chemours FS-3100;

[0058] Dodecyltrimethylammonium chloride, N,N'-methylenebisacrylamide, glyceryl citrate, tributyl citrate, trioctyl citrate, xanthan gum, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and octadecyl methacrylate are all commercially available.

[0059] Example 1

[0060] This embodiment provides a thickened acid system for high-temperature carbonate reservoirs. The thickened acid system, by total weight, comprises: 15% hydrochloric acid, 0.5% high-temperature thickener, 0.01% high-temperature stabilizer (N,N'-methylenebisacrylamide), 1% retarder (dodecyltrimethylammonium chloride), 5% corrosion inhibitor (a complex of thiourea and imidazoline derivatives), 1% corrosion synergist (antimony trioxide), 1% iron ion stabilizer (EDTA), 5% co-solvent (ethanol), 1% drainage aid (fluorocarbon surfactant), and 70.49% water.

[0061] Based on the total weight of the high-temperature resistant thickener, the high-temperature resistant thickener comprises: 1% centering agent (glyceryl citrate fatty acid ester), 15% flow agent (tributyl citrate), 1% inner network polymer (xanthan gum), 50% monomer (40% acrylamide + 5% 2-acrylamido-2-methylpropanesulfonic acid + 5% octadecyl methacrylate), 0.12% initiator (ammonium persulfate and sodium sulfite added in a weight ratio of 1:1), and 32.88% water; the preparation method of the high-temperature resistant thickener includes the following steps:

[0062] (1) Preparation of internal network

[0063] Water and the central agent are mixed, and the pH of the mixture is adjusted to 7-8 using sodium hydroxide aqueous solution. The mixture is heated to 50-60℃ and stirred until homogeneous to obtain a stirred system. The stirred system is then mixed with the flow agent and the inner network polymer in sequence until homogeneous to obtain the inner network solution.

[0064] (2) Preparation of the outer mesh of the high-temperature main agent

[0065] The inner network solution is stirred and mixed with the monomer, and nitrogen gas is introduced to remove oxygen while stirring to obtain a coolant; the coolant is stirred and mixed with the initiator, and nitrogen gas is introduced to remove oxygen while stirring, and the temperature is raised to 60-65℃ and reacted for 5-10 hours under continuous nitrogen gas introduction to obtain the high-temperature resistant thickener.

[0066] The preparation method of the high-temperature carbonate reservoir thickened acid system in this embodiment includes the following steps:

[0067] First, add the acid and co-solvent to the water and stir until homogeneous. Then, add the corrosion inhibitor and synergist, stirring until homogeneous again. Next, add the corrosion inhibitor, retarder, iron ion stabilizer, drainage aid, and high-temperature stabilizer in any order, stirring until homogeneous. Finally, add the high-temperature thickener and stir until homogeneous. The solution is then directly injected into the target reservoir during the application process.

[0068] The high-temperature carbonate reservoir thickening acid system of this embodiment is suitable for acidizing carbonate reservoirs with a temperature of 140℃ and a well depth of ≤6000m.

[0069] Example 2

[0070] This embodiment provides a thickened acid solution system for high-temperature carbonate reservoirs. The only difference between this embodiment and Embodiment 1 is that:

[0071] Based on the total weight of the thickened acid system, the thickened acid system comprises: 15% hydrochloric acid, 1% high-temperature thickener, 0.03% high-temperature stabilizer, 2% retarder, 5% corrosion inhibitor, 1% corrosion inhibitor synergist, 1% iron ion stabilizer, 5% solubilizer, 2% drainage aid, and 67.97% water.

[0072] The flow agent is trioctyl citrate:

[0073] The high-temperature carbonate reservoir thickening acid system of this embodiment is suitable for acidizing carbonate reservoirs with a temperature of 180℃ and a well depth of ≤7000m.

[0074] Example 3

[0075] This embodiment provides a thickened acid solution system for high-temperature carbonate reservoirs. The only difference between this embodiment and Embodiment 1 is that:

[0076] Based on the total weight of the thickened acid system, the thickened acid system comprises: 15% hydrochloric acid, 1.5% high-temperature resistant thickener, 0.05% high-temperature stabilizer, 3% retarder, 5% corrosion inhibitor, 1% corrosion inhibitor synergist, 1% iron ion stabilizer, 5% solubilizer, 3% drainage aid, and 65.45% water.

[0077] The flow agent is trioctyl citrate;

[0078] The high-temperature carbonate reservoir thickening acid system of this embodiment is suitable for acidizing carbonate reservoirs at 220℃ and with a well depth ≤8000m.

[0079] Example 4

[0080] This embodiment provides a thickened acid solution system for high-temperature carbonate reservoirs. The only difference between this embodiment and Embodiment 3 is that:

[0081] Based on the total weight of the thickened acid system, the thickened acid system comprises: 15% hydrochloric acid, 1.5% high-temperature resistant thickener, 0.05% high-temperature stabilizer, 3% retarder, 5% corrosion inhibitor, 1% corrosion inhibitor synergist, 1% iron ion stabilizer, 5% solubilizer, 2% drainage aid, and 66.45% water.

[0082] Based on the total weight of the high-temperature resistant thickener, the high-temperature resistant thickener comprises: 1% centering agent, 10% flow agent, 1% internal network polymer, 50% monomer, 0.12% initiator, and 37.88% water;

[0083] Comparative Example 1

[0084] This comparative example provides a thickened acid solution system for high-temperature carbonate reservoirs. The only difference between this example and Example 1 is that:

[0085] Based on the total weight of the thickened acid system, the thickened acid system comprises: 15% hydrochloric acid, 1.5% common thickener (polymerized from acrylamide and 2-acrylamido-2-methylpropanesulfonic acid, with a mass ratio of acrylamide to 2-acrylamido-2-methylpropanesulfonic acid of 4:1), 0.05% high-temperature stabilizer, 3% retarder, 5% corrosion inhibitor, 1% corrosion inhibitor synergist, 1% iron ion stabilizer, 5% cosolvent, 3% drainage aid, and 65.45% water.

[0086] Test Example 1 investigates the temperature and shear resistance of thickened acid fluid systems in high-temperature carbonate reservoirs.

[0087] This test example uses high-temperature rheological experiments to test the rheological properties of the thickened acid solution systems of Examples 1-4 and Comparative Example 1 at different temperatures. The results are shown in the figures below. Figures 1-5 ;

[0088] The experimental setup was HAAKE MARSⅢ; the initial temperature for all experiments was room temperature (25℃); and the heating rate was the instrument's standard heating rate. The shear rate was 170 s⁻¹. -1 .

[0089] Depend on Figures 1-3 It can be seen that Examples 1, 2, and 3 exhibit stable shear resistance under high temperature conditions of 140℃, 180℃, and 220℃, respectively. After shearing for 90 minutes, the liquid viscosity retention rate is relatively high, indicating that the liquid has good high temperature stability.

[0090] Depend on Figure 4 and Figure 3 The comparison shows that the acid system with 10% flow agent in Example 4 has poorer temperature resistance than the acid system with 15% flow agent in Example 3. In Example 4, the viscosity decreases rapidly with increasing temperature, while in Example 3, the viscosity decreases slowly and the viscosity retention rate is high. This indicates that adding flow agent can synergistically enhance the temperature resistance of the acid system with the double-network structure.

[0091] Depend on Figure 5 and Figure 3 The comparison shows that the temperature resistance of the ordinary thickener acid system in Comparative Example 1 is not as good as that of the double-network acid system in Example 3. This indicates that the thickened acid system greatly improves the temperature resistance of the acid system due to the synergistic effect of the double-network structure and the flow agent.

[0092] Test Example 2: Evaluation of Acid-Rock Reaction Kinetics Experiment

[0093] Acid-rock reaction kinetics experiments were conducted using outcrop cores of the Maokou Formation limestone to test Examples 1-4 and Comparative Example 1. The data are shown in Table 1.

[0094] As can be seen from Table 1, the addition of a flow agent can synergistically slow down the acid-rock reaction rate in the dual network. In Comparative Example 1, the acid-rock reaction rate is the fastest because the ordinary thickener is not resistant to high temperatures.

[0095] Table 1

[0096]

[0097]

[0098] Test Example 3: Experimental Evaluation of Friction Performance of Thickened Acid System in High-Temperature Carbonate Reservoir

[0099] In this test case, pipeline friction tests were conducted on Examples 1-4 and Comparative Example 1, and the data are shown in Table 2.

[0100] Table 2

[0101] Acid liquor Example 4 Comparative Example 1 Example 1 Example 2 Example 3 Resistance reduction rate, % 43.5 40.1 58.2 60.8 62.7

[0102] As can be seen from Table 2, the introduction of the fluidizing agent in this invention effectively improves the fluidity of the thickened acid solution system and reduces the friction of the thickened acid solution system.

[0103] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A thickened acid solution system for high-temperature carbonate reservoirs, characterized in that, Based on the total weight of the thickened acid system, the thickened acid system comprises: 10-30% acid, 0.05-3% high-temperature resistant thickener, 0.005-0.05% high-temperature stabilizer, 0.5-3.5% retarder, 1-6% corrosion inhibitor, 0.5-2.5% corrosion inhibitor synergist, 0.5-3.5% iron ion stabilizer, 3-10% co-solvent, 0.5-3.5% drainage aid, and the remainder is water; Based on the total weight of the high-temperature resistant thickener, the high-temperature resistant thickener comprises: 0.5-2.5% centering agent, 5-20% flow agent, 0.05-1.5% internal network polymer, 10-60% monomer, 0.01-0.2% initiator, and the remainder is water; The flow agent is at least one of tributyl citrate, isoamyl citrate, and trioctyl citrate.

2. The high-temperature carbonate reservoir thickened acid system according to claim 1, wherein, The temperature of high-temperature carbonate reservoirs is 120-240℃.

3. The high-temperature carbonate reservoir thickened acid system according to claim 1, wherein, The acid solution is at least one of hydrochloric acid, acetic acid, formic acid, and oxalic acid; The high-temperature stabilizer is at least one of N,N'-methylenebisacrylamide, ethyleneimine, and polycarbodiimine; The retarder is at least one of dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, octadecyltrimethylammonium chloride, oleic acid, and sodium oleate. The corrosion inhibitor is a high-temperature pickling corrosion inhibitor and / or an acidification corrosion inhibitor; The corrosion inhibitor is at least one of nano-silica, nano-titanium oxide and antimony trioxide; The iron ion stabilizer is at least one of citric acid, EDTA, NTA, DTPA, and HEDP; The co-solvent is at least one of acetone, ethanol, methanol, isopropanol, propanol, ethylene glycol, and benzyl alcohol; The drainage aid is a fluorocarbon surfactant and / or a fluorosilicone surfactant.

4. The high-temperature carbonate reservoir thickened acid system according to claim 3, wherein, The corrosion inhibitor is at least one of aldehyde-ketone-amine condensates, alkynols, thiourea, and imidazoline derivatives.

5. The high-temperature carbonate reservoir thickened acid system according to claim 1, wherein, Based on the total weight of the high-temperature resistant thickener, the high-temperature resistant thickener comprises: 0.5-2.5% centering agent, 11-20% flow agent, 0.05-1.5% internal network polymer, 10-60% monomer, 0.01-0.2% initiator, and the remainder is water.

6. The high-temperature carbonate reservoir thickened acid system according to claim 1, wherein, The central agent is at least one of citrate fatty acid glyceride, glyceryl stearate and polyoxyethylene sorbitan monooleate; The inner network polymer is at least one of xanthan gum, cellulose, modified cellulose, guar gum, and modified guar gum; The monomer is at least one selected from acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acryloyloxyethyltrimethylammonium chloride, octadecyl methacrylate and dodecyl methacrylate; The initiator is at least one of potassium persulfate, ammonium persulfate, and sodium sulfite.

7. The high-temperature carbonate reservoir thickened acid system according to claim 1, wherein, The high-temperature resistant thickener is a double-network polymer high-temperature resistant thickener, and the preparation method of the high-temperature resistant thickener includes the following steps: (1) Preparation of internal network Water and the central agent are mixed, the pH of the mixture is adjusted to 7-8, and the mixture is heated and stirred until homogeneous to obtain a stirred system; the stirred system is then mixed with the flow agent and the inner network polymer in sequence until homogeneous to obtain an inner network solution; (2) Preparation of the outer mesh of the high-temperature main agent The inner network solution is stirred and mixed with the monomer, and nitrogen gas is introduced to remove oxygen while stirring to obtain a coolant; the coolant is stirred and mixed with the initiator, and nitrogen gas is introduced to remove oxygen while stirring, and the temperature is raised and reacted under continuous nitrogen gas supply to obtain the high-temperature resistant thickener.

8. The high-temperature carbonate reservoir thickened acid system according to claim 7, wherein, In step (1): The pH of the mixture was adjusted to 7-8 using an aqueous sodium hydroxide solution. The heating and stirring temperature is 50-60℃.

9. The high-temperature carbonate reservoir thickening acid system according to claim 7, wherein, In step (2): the reaction temperature is 60-65℃ and the time is 5-10h.

10. A method for preparing the high-temperature carbonate reservoir thickened acid system according to any one of claims 1-9, characterized in that, The preparation method includes the following steps: S1: Mix the acid solution, co-solvent, and water thoroughly to obtain a first mixture; S2: Mix the first mixture and the corrosion inhibitor evenly to obtain the second mixture; S3: Mix the first mixture, the second mixture, the corrosion inhibitor, the retarder, the iron ion stabilizer, the drainage aid, and the high temperature stabilizer evenly to obtain the third mixture; S4: Mix the third mixture with the high-temperature thickener until homogeneous to obtain the high-temperature carbonate reservoir thickened acid system.

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