Efficient gelling agent for acidification and preparation method thereof

Abstract

The invention relates to the technical field of compositions for drilling or well drilling, and particularly discloses a gelling agent for efficient acidification and a preparation method of the gelling agent. According to the preparation method of the gelling agent for efficient acidification, the prepared gelling agent is high in dissolution speed in an acid solution, and the acidification construction efficiency can be improved; meanwhile, the tackifying and temperature-resistant effects are good, the tackifying agent is suitable for high-temperature deep well acidification construction, the flow conductivity of acid-etched cracks and the penetration distance of acid liquor can be effectively improved when the tackifying agent is applied to the acidification liquor, and the purpose of deep acidification can be achieved.

Description

Technical Field

[0001] The invention relates to the technical field of compositions used for drilling holes or wells, and in particular to a high-efficiency acidification gelling agent and a preparation method thereof. Background Art

[0002] Conventional acid fluid cannot reach the far well area due to the fast acid-rock reaction speed, short effective action distance and limited penetration depth in acidizing construction, so the production increase measures are less effective. In order to improve the acidizing effect, one of the most effective methods is to add gelling agent to the acid fluid to control the diffusion rate of hydrogen ions, gradually dissolve the rock and its clay minerals, enhance the penetration ability of the acid fluid in the formation, and thus achieve deep acidizing of the formation.

[0003] Domestic and foreign acidification gelling agents mainly include polysaccharide polymers (guar gum, cellulose, etc.), high molecular biopolymers (xanthan gum, sesbania gum, etc.), ethylene polymers, etc. Among them, acrylamide polymer products are the most developed and applied, such as copolymers of acrylamide (AM) and acryloyloxyethyl trimethylammonium chloride (DAC), copolymers of AM and 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and copolymers of maleic anhydride (MAH), AMPS, and methacryloyloxyethyl trimethylammonium chloride (DMC). These copolymers have high relative molecular weight, heat resistance, salt resistance, shear resistance, and good retarding performance, and can meet the requirements of acidification construction below 150°C. However, the acrylamide segments in these copolymers are easily hydrolyzed at high temperatures, and the hydrolysis products will react with high-valent ions to form precipitation.

[0004] Chinese patent 202210754686.8 provides a gelling agent for acid fracturing operation and a preparation method thereof, which relates to the field of oilfield chemical additives. The method comprises: esterifying 2-benzyl methyl acrylate and N,N-dimethylethanolamine, and then adding chloroform for quaternization reaction to obtain a functional cationic monomer; mixing the functional cationic monomer, cationic monomer, nonionic monomer, sulfonic acid monomer, ammonium chloride and deionized water to obtain an aqueous phase reaction liquid; mixing the oily solvent and the emulsifier to obtain an oil phase reaction liquid; adding the oil phase reaction liquid to the aqueous phase reaction liquid, and then adding an initiator to initiate a polymerization reaction, and after the reaction is completed, adding a phase transfer agent to obtain a gelling agent for acid fracturing operation. The gelling agent for acid fracturing operation prepared by the invention has strong stability, fast dispersion speed, good high temperature resistance, high viscosity, no residue, easy use and other advantages, and can improve the efficiency of acid fracturing operation.

[0005] Chinese patent 202310738283.9 discloses a gelling agent for high temperature resistant acid fracturing and its preparation method, which belongs to the technical field of chemical additives for oil fields. It is prepared from the following components by mass percentage: 10% to 25% monomer A, 2.9% to 15% monomer B, 0.1% to 2% cationic hydrophobic functional monomer, 0.01% to 0.1% initiator, and 60% to 85% water; monomer A is a water-soluble polymerizable monomer with double bonds, monomer B is a sulfonic acid monomer with double bonds, and cationic hydrophobic functional monomer is a monomer with hydrophobic chains and rigid groups. The relative molecular weight of the high temperature resistant acid fracturing gelling agent of the invention is 6 million to 8 million, with good water solubility, acid solubility, viscosity enhancement, temperature resistance, and shear resistance. It can be used in acid fracturing construction and enhanced oil recovery operations in oil production above 160°C.

[0006] The depth of deep oil and gas reservoirs in Tarim, Sichuan, Bohai Bay and other regions in China generally exceeds 6000m, and the bottom hole temperature is higher than 180℃, which puts higher requirements on the temperature resistance and retarding performance of the acid system. The high temperature viscosity increasing effect of the gelling agent in the existing technology is insufficient; and the amount of gelling agent product required is large, and the residual acid is not easy to handle, so it is imperative to improve the high temperature resistance of the gelling agent. Summary of the invention

[0007] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is to provide a high-efficiency acidification gelling agent and a preparation method thereof.

[0008] The polymer-based gelling agent used in the prior art has a large molecular weight, which causes the molecular chain to form irregular clusters in the solution, which will increase the viscosity of the fracturing fluid and degrade at high temperatures, thereby causing structural failure and an increase in viscosity, affecting the final mining process. In the present invention, a relatively small molecular weight acidizing gelling agent is synthesized. Due to the small molecular weight, the molecular chain is arranged more regularly in the solution, and it is not easy to move and degrade the molecular chain under heat, thereby improving the stability at high temperature and reducing the sensitivity to heat. In addition, the rigid groups on the smaller molecular structure increase the resistance to molecular thermal motion, hinder the movement of the molecular chain, and also increase the temperature resistance of the gelling agent. The prepared gelling agent has both hydrophobic long chains and hydrophilic polar groups, so it can be adsorbed between the oil-water interface, thereby promoting the adjustment between the interface and the emulsion, and enhancing the ability of the gelling agent to adjust the rheological properties of the acid solution. Applying it to the acidizing fluid can effectively improve the conductivity of the acid-etched fracture and the penetration distance of the acid solution, and can achieve the purpose of deep acidification.

[0009] To achieve the above object, the present invention provides a method for preparing a high-efficiency acidification gelling agent, comprising the following steps:

[0010] S1: 10-phenylundecanoic acid and N,N,N',N'-tetrakis(2-aminoethyl)hexane-1,6-diamine were mixed, and heated and stirred under an inert atmosphere to obtain a gel product;

[0011] S2: The product of the previous step is washed with ethanol and methanol to adjust the pH, and then dried, crushed and sieved to obtain a high-efficiency acidification gelling agent.

[0012] Furthermore, the molar ratio of the 10-phenylundecanoic acid to N,N,N',N'-tetrakis(2-aminoethyl)hexane-1,6-diamine is 1:2-5.

[0013] Furthermore, the inert atmosphere is a nitrogen atmosphere.

[0014] Furthermore, the heating temperature ranges from 150 to 180°C.

[0015] Furthermore, the stirring speed is 200-400 rpm.

[0016] Furthermore, the stirring time is 4 to 6 hours.

[0017] Furthermore, the cleaning and pH adjustment is to adjust the pH to neutral.

[0018] Furthermore, the drying temperature is 100-150° C. and the drying time is 4-6 hours.

[0019] Furthermore, the mesh size of the crushed and sieved product is 100 to 200 meshes.

[0020] Preferably, the method for preparing the highly efficient acidifying gelling agent comprises the following steps:

[0021] S1: 10-phenylundecanoic acid and N,N,N',N'-tetrakis(2-aminoethyl)hexane-1,6-diamine are mixed in a molar ratio of 10-phenylundecanoic acid to N,N,N',N'-tetrakis(2-aminoethyl)hexane-1,6-diamine of 1:2-5, heated to 150-180° C. under a nitrogen atmosphere, and stirred at 200-400 rpm for 4-6 hours to obtain a gel product;

[0022] S2: The product of the previous step is washed with ethanol and methanol until the pH is neutral, dried at 100-150° C. for 4-6 hours, and crushed through a 100-200 mesh sieve to obtain a high-efficiency acidification gelling agent.

[0023] The invention also provides a high-efficiency acidification gelling agent, which is prepared by the above method.

[0024] Beneficial effects of the present invention:

[0025] 1. The present invention synthesizes an acidification gelling agent with a relatively small molecular weight. Due to the small molecular weight, the molecular chains are arranged more regularly in the solution, and are not prone to molecular chain movement and degradation under heat, thereby improving the stability under high temperature and reducing the sensitivity to heat. In addition, the rigid groups on the smaller molecular structure increase the resistance to molecular thermal movement, hinder the movement of the molecular chain, and also increase the temperature resistance of the gelling agent.

[0026] 2. Compared with the prior art, the gelling agent prepared by the present invention has both hydrophobic long chains and hydrophilic polar groups, so it can be adsorbed between the oil-water interface, thereby promoting the adjustment between the interface and the emulsion, and enhancing the ability of the gelling agent to adjust the rheological properties of the acid solution. Applying it to the acidizing solution can effectively improve the conductivity of the acid-etched cracks and the acid penetration distance, and can achieve the purpose of deep acidification. DETAILED DESCRIPTION

[0027] 10-phenylundecanoic acid, CAS No.: 6268-52-6.

[0028] N,N,N',N'-Tetrakis(2-aminoethyl)hexane-1,6-diamine, CAS No.: 84168-09-2.

[0029] N,N'-bis(2-aminoethyl)hexane-1,6-diamine, CAS No.: 52469-92-8.

[0030] N'-heptylethane-1,2-diamine, CAS No.: 65639-09-0.

[0031] Example 1

[0032] A method for preparing a high-efficiency acidification gelling agent comprises the following steps:

[0033] S1: 10-phenylundecanoic acid and N,N,N',N'-tetrakis(2-aminoethyl)hexane-1,6-diamine were mixed in a molar ratio of 10-phenylundecanoic acid to N,N,N',N'-tetrakis(2-aminoethyl)hexane-1,6-diamine of 1:4.5, and the mixture was heated to 160° C. under a nitrogen atmosphere and stirred at 300 rpm for 5 h to obtain a gel product;

[0034] S2: The product of the previous step is washed with ethanol and methanol until the pH is neutral, dried at 130°C for 4 hours, and crushed through a 100-mesh sieve to obtain a high-efficiency acidification gelling agent.

[0035] Example 2

[0036] The same as Example 1, the only difference is that the molar ratio of 10-phenylundecanoic acid to N,N,N',N'-tetrakis(2-aminoethyl)hexane-1,6-diamine is 1:2.

[0037] Example 3

[0038] The same as Example 1, the only difference is that the molar ratio of 10-phenylundecanoic acid to N,N,N',N'-tetrakis(2-aminoethyl)hexane-1,6-diamine is 1:3.

[0039] Example 4

[0040] The same as Example 1, the only difference is that the molar ratio of 10-phenylundecanoic acid to N,N,N',N'-tetrakis(2-aminoethyl)hexane-1,6-diamine is 1:4.

[0041] Comparative Example 1

[0042] A method for preparing a high-efficiency acidification gelling agent comprises the following steps:

[0043] S1: 10-phenylundecanoic acid and N,N'-bis(2-aminoethyl)-1,6-hexanediamine were mixed in a molar ratio of 10-phenylundecanoic acid to N,N'-bis(2-aminoethyl)-1,6-hexanediamine of 1:4.5, heated to 160° C. under a nitrogen atmosphere, and stirred at 300 rpm for 5 h to obtain a gel product;

[0044] S2: The product of the previous step is washed with ethanol and methanol until the pH is neutral, dried at 130°C for 4 hours, and crushed through a 100-mesh sieve to obtain a high-efficiency acidification gelling agent.

[0045] Comparative Example 2

[0046] A method for preparing a high-efficiency acidification gelling agent comprises the following steps:

[0047] S1: 10-phenylundecanoic acid and N'-heptylethane-1,2-diamine were mixed in a molar ratio of 10-phenylundecanoic acid to N'-heptylethane-1,2-diamine of 1:4.5, heated to 160° C. under a nitrogen atmosphere, and stirred at 300 rpm for 5 h to obtain a gel product;

[0048] S2: The product of the previous step is washed with ethanol and methanol until the pH is neutral, dried at 130°C for 4 hours, and crushed through a 100-mesh sieve to obtain a high-efficiency acidification gelling agent.

[0049] Comparative Example 3

[0050] A method for preparing a high-efficiency acidification gelling agent comprises the following steps:

[0051] S1: Undecanoic acid and N,N,N',N'-tetrakis(2-aminoethyl)hexane-1,6-diamine were mixed in a molar ratio of 1:4.5, and the mixture was heated to 160° C. under a nitrogen atmosphere and stirred at 300 rpm for 5 h to obtain a gel product;

[0052] S2: The product of the previous step is washed with ethanol and methanol until the pH is neutral, dried at 130°C for 4 hours, and crushed through a 100-mesh sieve to obtain a high-efficiency acidification gelling agent.

[0053] Comparative Example 4

[0054] Commercially available guar gum powder was used as a high-efficiency acidification gelling agent, model 564-561, which was sourced from Jinan Zhiheng Zhiyuan.

[0055] Test Example 1

[0056] The performance of the synthesized gelling agent was evaluated with reference to the petroleum and natural gas industry standard SY / T 6214-2016 "Thickening Agent for Thickened Acid". 0.5% corrosion inhibitor (potassium iodide and copper iodide), 4.0% Mannich base corrosion inhibitor, 1.0% citric acid and 1.0% Tween-80 were added to a 20% hydrochloric acid solution. 0.8% gelling agent was added to the base liquid to prepare gelled acid, which was stirred and dissolved at room temperature. -1 When the viscosity of the acid solution is the same at two consecutive time points, stop recording and take the first time point of the viscosity stabilization as the acid dissolution time.

[0057] Table 1 Acid dissolution time of gelling agent

[0058] Experimental protocol Acid dissolution time / min Example 1 55 Comparative Example 1 60 Comparative Example 2 75 Comparative Example 3 68 Comparative Example 4 69

[0059] The dissolution rate of the gelling agent in the acid solution is an important parameter for evaluating the performance of the gelling agent, and the gelling agent is generally required to have a faster dissolution rate. When the change in the apparent viscosity of the acid solution tends to be flat, it indicates that the gelling agent has been completely dissolved. When the molecular weight is smaller, the viscosity-enhancing property of the solution is relatively weak, so the acid dissolution time of the control examples 1 to 2 is longer than that of Example 1. Guar gum is a non-ionic polysaccharide branched polymer, and its main chemical component is galactomannan. It is a very effective thickener for water-based fluids and has a low residue content, so its acid dissolution time is relatively short. The molecular weight of the gelling agent in Example 1 is moderate, so the acid dissolution time performance is better. In the on-site construction of the oil field, the acid dissolution time of the gelling agent is required to be less than 120 minutes, so the synthesized gelling agents can meet the on-site construction requirements.

[0060] Test Example 2

[0061] 0.8% gelling agent was added to the base liquid to prepare gelled acid. -1 Then, at 180℃, 170s -1 The stability of the acid solution at high temperature was investigated using a rheometer. The acid solution was sheared at high temperature for 2 hours, and the viscosity before and after high temperature shearing was measured.

[0062] Table 2 Heat and shear resistance of gelling agent

[0063] Experimental protocol 0h viscosity mPa·s Viscosity after 2h mPa·s Example 1 55.1 18.3 Comparative Example 1 48.6 15.2 Comparative Example 2 45.1 14.0 Comparative Example 3 49.7 13.1 Comparative Example 4 50.2 5.6

[0064] The viscosity of the acid solution is the most important indicator of the gelling acid system. As the temperature rises, the viscosity of the gelling acid will gradually decrease. In general, the viscosity of the solution is positively correlated with the relative molecular mass of the polymer and is also affected by the polymer conformation. Under high temperature, the free volume between the segments increases, and the interaction between the segments decreases; acidic conditions promote the hydrolysis of the polymer, intensify the curling between the molecular segments, and reduce the viscosity of the solution. From the test results, it can be seen that the viscosity of Example 1 is the largest before heating, and it can still maintain a good viscosity after 2 hours of high temperature shearing. According to the industry standard SY / T 6214-2016, at a shear rate of 170s -1Under the condition of , the temperature when the apparent viscosity of the acid solution drops to 15mPa·s is the temperature resistance value of the sample. In Example 1, after high-temperature shearing at 180°C, the apparent viscosity of the gelled acid solution is 18.3mPa·s, which is still greater than 15mPa·s, indicating that the gelling agent can resist temperatures above 180°C. This is because the gelling agent polymer contains long-chain hydrophobic groups, which can enhance the hydrophobic association within and between molecules, and the hydrophobic association is an endothermic effect driven by entropy, which has temperature-resistant viscosity-increasing properties, and is beneficial to improving the temperature and salt resistance of the polymer. At the same time, the molecular weight is small, so the molecular chains are arranged more regularly in the solution, and it is not easy for the molecular chains to move and degrade under heat, thereby improving the stability at high temperatures and reducing the sensitivity to heat. In addition, the rigid groups on the smaller molecular structure increase the resistance to molecular thermal motion, hinder the movement of the molecular chains, and also increase the temperature resistance of the gelling agent. Compared with Example 1, the molecular weight of Control Examples 1 to 2 is smaller, so the apparent viscosity is also smaller. However, the rigid groups are lacking in Control Example 3, and the guar gum powder in Control Example 4 has poor high temperature stability and is unstable in a strong acid system. The unmodified natural guar gum that is easily biodegraded forms a viscous solution after hydration, and will quickly undergo thermal degradation when heated, so the viscosity drops sharply.

[0065] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for preparing a highly efficient acidifying gelling agent, characterized in that: The steps include: S1: 10-phenylundecanoic acid and N,N,N',N'-tetrakis(2-aminoethyl)hexane-1,6-diamine were mixed, and heated and stirred under an inert atmosphere to obtain a gel product; S2: The product of the previous step is washed with ethanol and methanol to adjust the pH, and then dried, crushed and sieved to obtain a high-efficiency acidification gelling agent.

2. The method for preparing a highly efficient acidifying gelling agent according to claim 1, characterized in that: The molar ratio of the 10-phenylundecanoic acid to N,N,N',N'-tetrakis(2-aminoethyl)hexane-1,6-diamine is 1:2-5.

3. The method for preparing a highly efficient acidifying gelling agent according to claim 1, characterized in that: The inert atmosphere is a nitrogen atmosphere.

4. The method for preparing a highly efficient acidifying gelling agent according to claim 1, characterized in that: The heating temperature ranges from 150 to 180°C.

5. The method for preparing a highly efficient acidifying gelling agent according to claim 1, characterized in that: The stirring speed is 200-400 rpm.

6. The method for preparing a highly efficient acidifying gelling agent according to claim 1, characterized in that: The stirring time is 4 to 6 hours.

7. The method for preparing a highly efficient acidifying gelling agent according to claim 1, characterized in that: The cleaning and pH adjustment is to adjust the pH to neutral.

8. The method for preparing a highly efficient acidifying gelling agent according to claim 1, characterized in that: The drying temperature is 100-150° C. and the drying time is 4-6 hours.

9. The method for preparing a highly efficient acidifying gelling agent according to claim 1, characterized in that: The mesh number of the crushing and screening is 100 to 200 meshes.

10. A highly efficient acidifying gelling agent, characterized in that: Prepared by the method according to any one of claims 1 to 9.