Waterproof locking agent as well as preparation method and application thereof

Abstract

The invention relates to a waterproof locking agent as well as a preparation method and application thereof. The preparation method of the waterproof locking agent comprises the following steps: (1) reacting alginic acid with amino alcohol to obtain an intermediate product; and (2) reacting the intermediate product obtained in the step (1) with organic ammonium chloride to obtain the waterproof locking agent. The preparation method of the waterproof locking agent provided by the invention is simple in preparation process, economical and efficient, and the prepared waterproof locking agent not only has good waterproof locking performance, but also is low in biotoxicity and good in biodegradability, so that the waterproof locking agent has green and environment-friendly performance; meanwhile, the surfactant has good foam inhibition performance, and the technical defect that in the prior art, due to the fact that strong and lasting foam is generated in the using process of the surfactant, the density of the drilling fluid fluctuates greatly, and the fluidity of the drilling fluid is reduced is well overcome.

Description

Technical Field

[0001] The invention relates to the field of exploration technology, and in particular to a waterproof locking agent and a preparation method and application thereof. Background Art

[0002] As the difficulty of later development of conventional oil and gas resources increases, more research is needed on unconventional oil and gas resources such as low permeability reservoirs to meet the growing energy demand. In China, the oil and gas reserves of low permeability reservoirs are large, accounting for nearly 24% of the total oil and gas resources. This type of reservoir has the characteristics of dense rock, poor physical properties, and small pore throats. During the development of low permeability oil and gas reservoirs, due to the capillary imbibition, the drilling fluid that invades the reservoir is difficult to return to the wellbore, causing water lock damage, which seriously affects the subsequent production capacity of oil and gas wells. Water lock damage is the most common and most serious type of damage in low-porosity and low-permeability oil and gas reservoirs, and the damage rate to low permeability reservoirs can reach 70-90%. Adding water-proof lock agents to drilling fluids can effectively reduce the surface tension and capillary force of the liquid phase and alleviate water lock damage.

[0003] At present, surfactants are used as waterproofing agents in water-based drilling fluids. They can effectively reduce the surface tension of the liquid phase, change the wettability of the reservoir core pore throats, and reduce the water lock damage of the drilling fluid filtrate to the low-permeability reservoir. Common waterproofing agents are fluorocarbon surfactants and hydrocarbon surfactants. Fluorocarbon surfactants are easily soluble in water, have stable chemical properties, and are resistant to acid, alkali, and high temperature. However, fluorocarbon surfactants have disadvantages such as difficult synthesis, many side reactions, and environmental pollution during degradation. Obviously, these disadvantages limit the research and application of fluorocarbon surfactants. Conventional hydrocarbon surfactants have low biological toxicity, but are difficult to biodegrade, have obvious foaming effects, and easily lead to large fluctuations in drilling fluid density and poor rheology. It is well known that surfactants always produce strong and persistent foams due to the nature of surface activity. In order to improve the anti-foaming performance, hydrocarbon surfactants and defoamers are usually compounded, but their compatibility needs to be considered.

[0004] Alginate has good water solubility and environmental protection, is inexpensive, and contains many hydrogen bond adsorption groups, such as hydroxyl groups and ether bonds, and has been widely used in mineral flotation and water treatment industries. Existing modified alginate waterproof lock agents use hydroxyethylethylenediamine, epichlorohydrin and pentaerythritol as raw materials to modify alginate molecules, and their preparation process is complex and the production efficiency is low.

[0005] In view of the poor environmental performance and severe foaming defects of the waterproof lock agent in the prior art, how to prepare a simple, easily degradable, and low-toxic foaming waterproof lock agent has become a problem that needs to be solved urgently. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a waterproof lock agent and a preparation method and application thereof. The preparation method of the waterproof lock agent of the present invention is simple, economical and efficient. The waterproof lock agent prepared by the present invention has a foam-free characteristic and good waterproof lock performance, is green and economical, can meet emission standards, and is easily biodegradable. The technical difficulties of the existing waterproof lock agent, such as high biological toxicity, difficulty in degradation, and severe foaming, are well overcome.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a method for preparing a waterproof lock agent, the preparation method comprising the following steps:

[0009] (1) reacting alginic acid with amino alcohol to obtain an intermediate product;

[0010] (2) reacting the intermediate product of step (1) with organic ammonium chloride to obtain the waterproof lock agent.

[0011] The present invention obtains an environmentally friendly, non-foaming, waterproof locking agent by modifying alginic acid in two steps, and the preparation process is simple, economical and efficient. In step (1) of the present invention, alginic acid and amino alcohol are subjected to an amidation reaction, which not only increases the hydrogen bond adsorption performance with rocks, but also has a chain extension effect, so that one end of the obtained intermediate product contains a hydroxyl group. In step (2), organic ammonium chloride is added to react, so that the obtained waterproof locking agent has a quaternary ammonium group, which promotes electrostatic adsorption of the molecular chain and the negatively charged core, further improving its adsorption performance; and in step (2), organic ammonium chloride and the hydroxyl group at one end of the intermediate product of step (1) are substituted to form an ether, thereby further extending the carbon chain. Through a two-step reaction, the obtained waterproofing agent has a lower surface tension and a higher contact angle, which can change the surface wettability of the reservoir core pore throats, reduce the capillary force of the liquid phase in the core pores, and thus reduce the water lock damage of the drilling fluid to the low-permeability reservoir; at the same time, the obtained waterproofing agent has an isomerized branched structure, which increases the drainage speed of the liquid film and reduces the stability of the foam, thereby making the waterproofing agent molecules have the characteristics of inhibiting foam formation.

[0012] Preferably, the number average molecular weight of the alginate in step (1) is 120,000-260,000 g / mol, for example, 120,000 g / mol, 140,000 g / mol, 160,000 g / mol, 180,000 g / mol, 200,000 g / mol, 220,000 g / mol, 240,000 g / mol or 260,000 g / mol, etc., but is not limited to the above-listed values, and other unlisted data within the numerical range are equally applicable.

[0013] In the present invention, alginic acid with a specific number average molecular weight is selected as the starting material. It is a natural biopolysaccharide with good water solubility and environmental protection. By chemically modifying it, the obtained waterproof lock agent can have good environmental protection performance. At the same time, the structure of alginic acid contains many adsorption groups such as hydroxyl groups, ether bonds, etc., which are adsorbed on the surface of the core pore throat through hydrogen bonds and have good adsorption stability.

[0014] Preferably, the amino alcohol in step (1) comprises any one of 4-amino-1-butanol, 3-amino-1-propanol or 5-amino-1-pentanol, or a combination of at least two thereof.

[0015] In the present invention, the amine group at one end of the amino alcohol can undergo an amidation reaction with the carboxyl group of alginic acid, and the hydroxyl group at the other end can undergo an etherification reaction with organic ammonium chloride, which can effectively extend the chain and is beneficial to improving the surface activity of the obtained waterproof lock agent.

[0016] Preferably, the mass ratio of alginate to amino alcohol in step (1) is (2-4):1, for example, 2:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1, 3:1, 3.2:1, 3.4:1, 3.6:1, 3.8:1 or 4:1, etc., and is not limited to the above-listed values. Other unlisted data within the numerical range are also applicable.

[0017] Preferably, the reaction in step (1) is carried out in a solvent.

[0018] Preferably, the solvent comprises dimethyl sulfoxide.

[0019] Preferably, the mass ratio of the solvent to alginic acid is (2.5-5):1, wherein, for example, it can be 2.5:1, 2.7:1, 3:1, 3.5:1, 3.5:1, 3.8:1, 4:1, 4.5:1 or 5:1, etc., and is not limited to the above-listed values. Other unlisted data within the numerical range are also applicable.

[0020] Preferably, the reaction in step (1) further comprises catalyst A.

[0021] Preferably, the catalyst A comprises boric acid.

[0022] Preferably, the content of the catalyst A is 0.5-1.4% of the mass of the alginate, for example, it can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3% or 1.4%, etc., and is not limited to the above-listed values. Other unlisted data within the numerical range are also applicable.

[0023] Preferably, the reaction in step (1) is carried out under reflux.

[0024] Preferably, the reaction temperature in step (1) is 140-160°C, for example, 142°C, 144°C, 146°C, 148°C, 150°C, 152°C, 154°C, 156°C or 158°C, etc., and is not limited to the above-listed values. Other unlisted data within the numerical range are also applicable.

[0025] Preferably, the reaction time of step (1) is 5-7 h, for example, it can be 5.2 h, 5.4 h, 5.6 h, 5.8 h, 6 h, 6.2 h, 6.4 h, 6.6 h or 6.8 h, etc., and is not limited to the above-listed values. Other unlisted data within the numerical range are also applicable.

[0026] Preferably, the reaction in step (1) is carried out under a protective gas atmosphere.

[0027] Preferably, the protective gas includes any one of nitrogen, argon or helium, or a combination of at least two of them, more preferably nitrogen.

[0028] Preferably, the purity of the nitrogen is ≥99.9% and the flow rate is 3.5-4.5m 3 / h, for example, 3.6m 3 / h、3.7m 3 / h、3.8m 3 / h、3.9m 3 / h、4.0m 3 / h、4.1m 3 / h、4.2m 3 / h、4.3m 3 / h、4.4m 3 / h or 4.5m 3 / h, etc., are not limited to the values ​​listed above, and other data not listed within the numerical range are also applicable.

[0029] Preferably, after the reaction in step (1) is completed, a post-treatment step is also included.

[0030] Preferably, the post-treatment step comprises distillation under reduced pressure, washing and drying.

[0031] Preferably, the washing comprises rinsing with a detergent for more than 3 times, more preferably 3-5 times, for example 3 times, 4 times or 5 times, to remove unreacted raw materials.

[0032] Preferably, the detergent comprises acetone.

[0033] Preferably, the drying comprises any one of reduced pressure rotary evaporation, vacuum drying or freeze drying, or a combination of at least two thereof.

[0034] Preferably, the vacuum drying temperature is 60-70°C, for example, it can be 61°C, 62°C, 63, 64°C, 65°C, 66°C, 67°C, 68°C or 69°C, etc., not limited to the above-listed values, and other unlisted data within the numerical range are also applicable.

[0035] Preferably, the organic ammonium chloride in step (2) includes any one of 3-chloro-2-hydroxypropyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltriethylammonium chloride or 3-chloro-2-hydroxypropyldimethylbenzylammonium chloride, or a combination of at least two thereof.

[0036] In the present invention, the organic ammonium chloride undergoes an etherification reaction with the hydroxyl group at one end of the amino alcohol. On the one hand, it can play a chain extension role, which is beneficial to improving the surface activity of the waterproof lock agent; on the other hand, the organic ammonium chloride can introduce a quaternary ammonium group into the molecular chain of the waterproof lock agent, which promotes the electrostatic adsorption of the molecular chain and the negatively charged core, so that the molecular chain of the waterproof lock agent forms a stable adsorption on the surface of the core pore throat, which is further beneficial to improving its waterproof lock property; at the same time, it can also make the obtained waterproof lock agent have an isomerized branched structure, thereby improving the anti-foaming performance of the obtained waterproof lock agent.

[0037] Preferably, the mass ratio of the intermediate product in step (2) to the organic ammonium chloride is (1.5-4):1, for example, it can be 1.5:1, 1.8:1, 2:1, 2.2:1, 2.5:1, 2.8:1, 3:1, 3.5:1 or 4:1, etc., and is not limited to the above-mentioned values. Other unlisted data within the numerical range are also applicable.

[0038] Preferably, the reaction in step (2) is carried out in a solvent.

[0039] Preferably, the solvent comprises isopropanol.

[0040] Preferably, the mass ratio of the solvent to the intermediate product is (6-10):1, for example, it can be 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1 or 10:1, etc., and is not limited to the above-listed values. Other unlisted data within the numerical range are also applicable.

[0041] Preferably, the reaction in step (2) further comprises catalyst B.

[0042] Preferably, the catalyst B comprises NaOH and / or KOH.

[0043] Preferably, the content of catalyst B is 0.5-1.4% of the mass of the intermediate product, for example, it can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3% or 1.4%, etc., and is not limited to the above-mentioned values. Other unlisted data within the numerical range are also applicable.

[0044] Preferably, the reaction in step (2) is carried out under reflux.

[0045] Preferably, the reaction temperature of the reaction in step (2) is 70-90°C, for example, it can be 72°C, 74°C, 76°C, 78°C, 80°C, 82°C, 84°C, 86°C or 88°C, etc., but is not limited to the listed values. Other unlisted data within the numerical range are also applicable.

[0046] Preferably, the reaction time of the reaction in step (2) is 6-8 h, for example, it can be 6.2 h, 6.4 h, 6.6 h, 6.8 h, 7 h, 7.2 h, 7.4 h, 7.6 h or 7.8 h, etc., and is not limited to the listed values. Other unlisted data within the numerical range are also applicable.

[0047] Preferably, after the reaction in step (2) is completed, a post-treatment step is also included.

[0048] Preferably, the post-treatment step comprises distillation under reduced pressure, washing and drying.

[0049] Preferably, the washing comprises rinsing with a detergent for 3-5 times, for example 3 times, 4 times or 5 times, to remove unreacted raw materials.

[0050] Preferably, the detergent comprises acetone.

[0051] Preferably, the drying comprises any one of reduced pressure rotary evaporation, vacuum drying or freeze drying, or a combination of at least two thereof.

[0052] Preferably, the vacuum drying temperature is 60-70°C, for example, it can be 61°C, 62°C, 63, 64°C, 65°C, 66°C, 67°C, 68°C or 69°C, etc., not limited to the above-listed values, and other unlisted data within the numerical range are also applicable.

[0053] Preferably, the preparation method of the waterproof lock agent specifically comprises the following steps:

[0054] (1) 30-40 parts by weight of alginic acid, 10-15 parts by weight of amino alcohol and 100-150 parts by weight of solvent are mixed, a protective gas is introduced, 0.2-0.4 parts by weight of catalyst A is added, and reflux reaction is carried out at 140-160° C. for 5-7 hours; after the reaction is completed, vacuum distillation, washing and drying are performed to obtain an intermediate product;

[0055] (2) 15-20 parts by weight of the intermediate product of step (1), 5-10 parts by weight of ammonium chloride, 0.1-0.2 parts by weight of catalyst B and 120-150 parts by weight of solvent are mixed, and refluxed at 70-90° C. for 6-8 hours; after the reaction is completed, the mixture is distilled under reduced pressure, washed and dried to obtain the waterproof lock agent.

[0056] In a second aspect, the present invention provides a waterproof locking agent, which is prepared by the preparation method of the waterproof locking agent described in the first aspect.

[0057] Exemplarily, the waterproof lock agent has a structure shown in Formula I:

[0058]

[0059] Wherein, R1 is selected from -(CH2)3-, -(CH2)4- or -(CH2)5-; R2 and R3 are each independently selected from -CH3 or -CH2-CH3; R4 is selected from -CH3, -CH2-CH3 or

[0060] m and n are each independently selected from integers greater than 1, for example, 2, 5, 10, 20, 50, 100, 200, 300, 400 or 500, etc., and are not limited to the listed values. Other unlisted data within the numerical range are also applicable.

[0061] Preferably, the EC of the waterproof lock agent 50 (Biological toxicity by luminescent bacteria method)>60000mg / L, for example, it can be 62000mg / L, 65000mg / L, 66000mg / L, 67000mg / L, 68000mg / L, 69000mg / L or 70000mg / L, etc., not limited to the listed values, other data not listed within the numerical range are also applicable.

[0062] In the present invention, the EC of the waterproof lock agent 50 It is far greater than 32000mg / L, which means it has lower biological toxicity and less harm to the environment. It is a green and environmentally friendly product that meets the emission standards and overcomes the technical difficulties of the existing waterproof lock agents with high biological toxicity.

[0063] Preferably, the BOD5 / CODcr (ratio of five-day biochemical oxygen demand to chemical oxygen demand) of the waterproof lock agent is greater than 29%, for example, it can be 29.1%, 29.2%, 29.3%, 29.4%, 29.5%, 29.6%, 29.7%, 29.8%, 29.9%, 30% or 31%, etc., not limited to the listed values, and other unlisted data within the numerical range are also applicable.

[0064] In the present invention, the BOD5 / CODcr of the waterproof lock agent is much greater than 13.5%, and it is a biodegradable product. After degradation, it will not cause harm to the environment, thus overcoming the technical difficulty of the existing waterproof lock agent that is not easy to degrade.

[0065] Preferably, at 120°C and in a 5wt% NaCl aqueous solution, the surface tension of the waterproof lock agent is less than 21mN / m, for example, it may be 20.5mN / m, 20.2mN / m, 20mN / m, 19.8mN / m, 19.5mN / m, 19.3mN / m or 19mN / m, etc., not limited to the listed values, and other unlisted data within the numerical range are equally applicable.

[0066] The water-proof locking agent in the present invention has a small surface tension and a large water tentacles, thereby being able to change the surface wettability of the reservoir core pore throats, reduce the capillary force of the liquid phase in the core pores, and further reduce the water lock damage of the drilling fluid to the low-permeability reservoir.

[0067] In a third aspect, the present invention provides a use of the waterproof lock agent as described in the second aspect in drilling.

[0068] Compared with the prior art, the present invention has at least the following beneficial effects:

[0069] (1) The preparation method of the waterproof lock agent provided by the present invention is to prepare an environmentally friendly foam-free waterproof lock agent through a two-step synthesis method. The preparation process is simple, economical and efficient, and has good practicality.

[0070] (2) The water-locking agent prepared by the preparation method of the present invention not only has a lower surface tension and a higher contact angle, thereby effectively improving the performance of filtrates such as drilling fluids and completion fluids, but also can prevent filtrates such as drilling fluids and completion fluids from invading the formation to cause water lock, thereby having good water-locking performance, and its biological toxicity is low and its biodegradability is good, thereby having green and environmentally friendly performance; at the same time, it also has good foaming inhibition performance, which well solves the technical defect in the prior art that the density of the drilling fluid fluctuates greatly due to the strong and persistent foam generated by the surfactant during use, thereby reducing its fluidity. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 : is the infrared spectrum of the waterproof lock agent obtained in Example 1, wherein T represents the transmittance and ν represents the wave number. DETAILED DESCRIPTION

[0072] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0073] The number average molecular weight Mn of the alginic acid used in the following examples is 240,000 g / mol and was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0074] Example 1

[0075] This embodiment provides a waterproof lock agent, and the preparation method thereof comprises the following steps:

[0076] (1) 30 parts by weight of alginic acid, 10 parts by weight of 4-amino-1-butanol and 100 parts by weight of dimethyl sulfoxide were added to a three-necked flask equipped with a stirrer, a reflux condenser and a thermometer, and stirred at 25°C for 15 minutes to completely dissolve the alginic acid and 4-amino-1-butanol in dimethyl sulfoxide. 3 / h flow of nitrogen with a purity of ≥99.9% for 30 minutes, add 0.2 parts by weight of boric acid into the flask, keep the reaction temperature at 140°C, and reflux for 5 hours under stirring. After the reaction is completed, remove the solvent by distillation under reduced pressure, rinse with acetone 3 times, and dry at 60°C to obtain an intermediate product.

[0077] (2) 15 parts by weight of the intermediate product of step (1), 5 parts by weight of 3-chloro-2-hydroxypropyltrimethylammonium chloride, 0.1 parts by weight of NaOH and 120 parts by weight of isopropanol were added to a three-necked flask equipped with a stirrer, a reflux condenser and a thermometer, and stirred at 25°C for 15 minutes to completely dissolve the intermediate product, 3-chloro-2-hydroxypropyltrimethylammonium chloride and NaOH in isopropanol. The reaction temperature was maintained at 70°C and refluxed for 6 hours under stirring. After the reaction was completed, the solvent was removed by distillation under reduced pressure, rinsed with acetone 3 times, and dried at 60°C to obtain the waterproof lock agent.

[0078] The characterization spectrum of the waterproof lock agent is as follows Figure 1 As shown. Figure 1 It can be seen that: 1610.4cm -1 The characteristic peak corresponding to carboxylate; 3305.3cm -1 The absorption peak at 1463.5 cm is attributed to the stretching vibration of hydroxyl groups; -1 The characteristic peak at 2941.2cm is attributed to the bending vibration of the methylene CH bond; -1 and 2842.9cm -1 The absorption peaks at 1710.1cm are related to the asymmetric and symmetric stretching vibrations of methylene respectively; -1 The absorption peak at 1122.6 cm -1 The peak at 720.4cm belongs to the stretching vibration of the ether bond, indicating the occurrence of substitution reaction; -1 (-CH2) nThis indicates that the designed target product has been synthesized.

[0079] Example 2

[0080] This embodiment provides a waterproof lock agent, and the preparation method thereof comprises the following steps:

[0081] (1) 40 parts by weight of alginic acid, 15 parts by weight of 3-amino-1-propanol and 120 parts by weight of dimethyl sulfoxide were added to a three-necked flask equipped with a stirrer, a reflux condenser and a thermometer, and stirred at 25°C for 30 minutes to dissolve the alginic acid and 3-amino-1-propanol in dimethyl sulfoxide. 3 / h flow of nitrogen with a purity of ≥99.9% for 30 minutes, add 0.3 parts by weight of boric acid into the flask, keep the reaction temperature at 150°C, and reflux for 6 hours under stirring. After the reaction is completed, remove the solvent by distillation under reduced pressure, rinse with acetone 3 times, and dry at 60°C to obtain an intermediate product.

[0082] (2) 20 parts by weight of the intermediate product of step (1), 10 parts by weight of 3-chloro-2-hydroxypropyl triethylammonium chloride, 0.2 parts by weight of NaOH and 140 parts by weight of isopropanol were added to a three-necked flask equipped with a stirrer, a reflux condenser and a thermometer, and stirred at 25°C for 30 minutes to completely dissolve the intermediate product, 3-chloro-2-hydroxypropyl triethylammonium chloride and NaOH in isopropanol. The reaction temperature was maintained at 80°C, and the reaction was refluxed for 8 hours under stirring. After the reaction was completed, the solvent was removed by distillation under reduced pressure, rinsed with acetone 3 times, and dried at 60°C to obtain the waterproof lock agent.

[0083] Example 3

[0084] This embodiment provides a waterproof lock agent, and the preparation method thereof comprises the following steps:

[0085] (1) 35 parts by weight of alginic acid, 15 parts by weight of 5-amino-1-pentanol and 150 parts by weight of dimethyl sulfoxide were added to a three-necked flask equipped with a stirrer, a reflux condenser and a thermometer, and stirred at 25° C. for 20 min to completely dissolve the alginic acid and 5-amino-1-pentanol in dimethyl sulfoxide. 3 / h flow of nitrogen with a purity of ≥99.9% for 30 minutes, add 0.4 parts by weight of boric acid into the flask, keep the reaction temperature at 160°C, and reflux for 7 hours under stirring. After the reaction is completed, remove the solvent by distillation under reduced pressure, rinse with acetone 3 times, and dry at 60°C to obtain an intermediate product.

[0086] (2) 15 parts by weight of the intermediate product of step (1), 8 parts by weight of 3-chloro-2-hydroxypropyl dimethyl benzyl ammonium chloride, 0.1 parts by weight of NaOH and 150 parts by weight of isopropanol were added to a three-necked flask equipped with a stirrer, a reflux condenser and a thermometer, and stirred at 25°C for 30 minutes to completely dissolve the intermediate product, 3-chloro-2-hydroxypropyl dimethyl benzyl ammonium chloride and NaOH in isopropanol, the reaction temperature was maintained at 90°C, and the reaction was refluxed for 7 hours under stirring. After the reaction was completed, the solvent was removed by distillation under reduced pressure, rinsed with acetone 3 times, and dried at 60°C to obtain the waterproof lock agent.

[0087] Example 4

[0088] This embodiment provides a waterproof lock agent, and the preparation method thereof comprises the following steps:

[0089] (1) 35 parts by weight of alginic acid, 12 parts by weight of 5-amino-1-pentanol and 120 parts by weight of dimethyl sulfoxide were added to a three-necked flask equipped with a stirrer, a reflux condenser and a thermometer, and stirred at 25° C. for 30 min to completely dissolve the alginic acid and 5-amino-1-pentanol in dimethyl sulfoxide. 3 / h flow of nitrogen with a purity of ≥99.9% for 30 minutes, add 0.3 parts by weight of boric acid into the flask, keep the reaction temperature at 140°C, and reflux for 6 hours under stirring. After the reaction is completed, remove the solvent by distillation under reduced pressure, rinse with acetone 3 times, and dry at 60°C to obtain an intermediate product.

[0090] (2) 20 parts by weight of the intermediate product of step (1), 5 parts by weight of 3-chloro-2-hydroxypropyltrimethylammonium chloride, 0.2 parts by weight of NaOH and 120 parts by weight of isopropanol were added to a three-necked flask equipped with a stirrer, a reflux condenser and a thermometer, and stirred at 25°C for 20 minutes to completely dissolve the intermediate product, 3-chloro-2-hydroxypropyltrimethylammonium chloride and NaOH in isopropanol. The reaction temperature was maintained at 70°C and refluxed for 6 hours under stirring. After the reaction was completed, the solvent was removed by distillation under reduced pressure, rinsed with acetone 3 times, and dried at 60°C to obtain the waterproof lock agent.

[0091] Comparative Example 1

[0092] This comparative example provides a waterproof lock agent, which is commercially available sodium perfluorooctane sulfonate.

[0093] Comparative Example 2

[0094] This comparative example provides a waterproof lock agent, which is commercially available octylphenol polyoxyethylene ether (OP-10).

[0095] The waterproof lock agent obtained in Examples 1-4 and Comparative Examples 1-2 was subjected to performance testing, and the testing method was as follows:

[0096] (1) Surface tension and contact angle test

[0097] A. The waterproof lock agents obtained in Examples 1-4 and Comparative Examples 1-2 were respectively added to 5 wt% NaCl aqueous solution, placed in an aging tank, and subjected to hot rolling aging at 120° C. for 16 h. The surface tension of the solution was tested at 25° C. using a surface tension meter.

[0098] B. The low permeability core (gas permeability of 1.0 mD) was fully polished with sandpaper and immersed in a 5wt% NaCl brine solution containing no waterproofing agent and containing the waterproofing agent obtained in Example 1-4 or Comparative Example 1-2 for 2 hours. After the core was dried at 25°C, the contact angle of distilled water on the core surface was measured.

[0099] The test results are shown in Table 1.

[0100] Table 1

[0101] 5wt% NaCl saline solution Surface tension (mN / m) Contact angle (°) Blank (no waterproofing agent) 59.5 23.2 Example 1 20.2 84.2 Example 2 19.5 85,6 Example 3 19.4 83.9 Example 4 19.8 84.0 Comparative Example 1 25.3 72.5 Comparative Example 2 24.9 69.7

[0102] It can be seen from Table 1 that the waterproofing agent provided by the present invention makes the surface tension of the 5wt% NaCl aqueous solution 19.4-20.2mN / m, and the contact angle of distilled water on the core surface is 83.9-85.6°. Obviously, compared with the 5 blank groups without adding the waterproofing agent, the addition of the waterproofing agent of the present invention can significantly reduce the surface tension of the 5wt% NaCl salt solution by 66-67.4%, and can also significantly increase the contact angle of distilled water on the core surface by 3.6-3.7 times.

[0103] By comparing Examples 1-4 with Comparative Examples 1-2, it can be seen that the waterproof locking agent provided in Comparative Example 1 reduces the surface tension of the 5wt% NaCl brine solution by 57.5%, and increases the contact angle of distilled water on the core surface to 3.1 times, while Comparative Example 2 reduces the surface tension of the 5wt% NaCl brine solution by 60%, and increases the contact angle of distilled water on the core surface to 3 times. Obviously, Examples 1-4 have lower surface tension and higher contact angle, that is, the waterproof locking performance of the waterproof locking agent of Examples 1-4 is better than that of the waterproof locking agent of Comparative Examples 1-2.

[0104] Therefore, the waterproof lock agent provided by the present invention can significantly reduce the surface tension of 5wt% NaCl aqueous solution, and at the same time can significantly increase the contact angle of distilled water on the core surface, thereby changing the wettability of the rock surface, reducing the capillary force of the brine solution in the core pores, and further reducing the water lock damage of the brine solution to the core.

[0105] (2) Environmental performance test

[0106] According to SY / T6788 2020 "Technical Evaluation Requirements for Environmental Protection of Water-soluble Oilfield Chemicals", the biological toxicity and degradation performance of the waterproof lock agents obtained in Examples 1-4 and Comparative Examples 1-2 were evaluated, among which EC 50 Biotoxicity test by luminescent bacteria; BOD5 / COD cr It is the ratio of five-day biochemical oxygen demand to chemical oxygen demand.

[0107] The test results are shown in Table 2.

[0108] Table 2

[0109] <![CDATA[EC 50 (mg / L)]]> <![CDATA[BOD5 / COD cr (%)]]> Example 1 67900 30.1 Example 2 65600 29.8 Example 3 68500 30.5 Example 4 66700 29.5 Comparative Example 1 23600 12.7 Comparative Example 2 31200 13.3

[0110] It can be seen from Table 2 that the EC of the waterproof lock agent provided by the present invention is 50 >60000mg / L, and BOD5 / COD cr >29%, that is, it has low biological toxicity and good biodegradability, and is a good green environmentally friendly product. Through Examples 1-4 and Comparative Examples 1-2, it can be found that the EC 50 Both are lower than 32000mg / L, and BOD5 / COD cr All of them are no higher than 13.5%. Obviously, the environmental protection performance of the waterproof lock agent provided by the present invention is better than the commercially available products commonly used in the field.

[0111] (3) Foaming performance test

[0112] 0.5 wt % of the waterproof lock agent obtained in Example 1-4 or Comparative Example 1-2 was added to 200 mL of 5 wt % NaCl aqueous solution, and the mixture was stirred at 8000 r / min for 30 s using a Waring Blender, and then poured into a 2000 mL measuring cylinder. The volume values ​​of V0, V2.5 and V5.0 were recorded, wherein V0 represents the original volume of the foam, V2.5 represents the volume of the foam after standing for 2.5 min, and V5.0 represents the volume of the foam after standing for 5.0 min.

[0113] The test results are shown in Table 3.

[0114] Table 3

[0115] V0(mL) V2.5(mL) V5.0(mL) Example 1 3.2 0 0 Example 2 4.3 0.2 0 Example 3 3.8 0 0 Example 4 4.5 0.3 0 Comparative Example 1 17 8 3 Comparative Example 2 37 19 11

[0116] It can be seen from Table 3 that the waterproofing locking agent obtained in Examples 1-4 only produces small impact bubbles at the beginning, which then disappears quickly, and will not foam after standing for 5 minutes, that is, the waterproofing locking agent provided by the present invention has a good foam suppression effect, while Comparative Examples 1-2 have very high foam at the beginning, and will still foam after standing for 5 minutes. Obviously, the waterproofing locking agent provided by the present invention has better foam suppression performance and can be better used in drilling fluid as a foam-free waterproofing locking agent.

[0117] In summary, the waterproof lock agent prepared by the specific preparation process of the present invention has a non-foaming characteristic and good waterproof lock performance, and at the same time, it can meet the emission standards and is easily biodegradable. That is, the present invention provides an environmentally friendly non-foaming waterproof lock agent with a simple preparation process, economical and efficient, which overcomes the technical difficulties of the existing waterproof lock agents, such as high biological toxicity, difficulty in degradation and severe foaming.

[0118] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a waterproof lock agent, characterized in that: The preparation method comprises the following steps: (1) reacting alginic acid with amino alcohol to obtain an intermediate product; (2) reacting the intermediate product of step (1) with organic ammonium chloride to obtain the waterproof lock agent.

2. The method for preparing the waterproof lock agent according to claim 1, characterized in that: The number average molecular weight of the alginic acid in step (1) is 120000-260000 g / mol; Preferably, the amino alcohol in step (1) comprises any one of 4-amino-1-butanol, 3-amino-1-propanol or 5-amino-1-pentanol, or a combination of at least two thereof; Preferably, the mass ratio of alginic acid to amino alcohol in step (1) is (2-4):1; Preferably, the reaction in step (1) is carried out in a solvent; Preferably, the solvent comprises dimethyl sulfoxide; Preferably, the mass ratio of the solvent to alginic acid is (2.5-5):1; Preferably, the reaction in step (1) further comprises catalyst A; Preferably, the catalyst A comprises boric acid; Preferably, the content of the catalyst A is 0.5-1.4% of the mass of the alginate; Preferably, the reaction in step (1) is carried out under reflux; Preferably, the reaction temperature in step (1) is 140-160°C; Preferably, the reaction time in step (1) is 5-7 hours.

3. The method for preparing the waterproof lock agent according to claim 1 or 2, characterized in that: The reaction in step (1) is carried out under a protective gas atmosphere; Preferably, the protective gas includes any one of nitrogen, argon or helium or a combination of at least two thereof, more preferably nitrogen; Preferably, the purity of the nitrogen is ≥99.9% and the flow rate is 3.5-4.5m 3 / h.

4. The method for preparing the waterproof lock agent according to any one of claims 1 to 3, characterized in that: After the reaction in step (1) is completed, a post-treatment step is also included; Preferably, the post-treatment step comprises distillation under reduced pressure, washing and drying; Preferably, the washing comprises rinsing with a detergent 3-5 times; Preferably, the detergent comprises acetone; Preferably, the drying comprises any one or a combination of at least two of reduced pressure rotary evaporation, vacuum drying or freeze drying; Preferably, the vacuum drying temperature is 60-70°C.

5. The method for preparing the waterproof lock agent according to any one of claims 1 to 4, characterized in that: The organic ammonium chloride in step (2) includes any one of 3-chloro-2-hydroxypropyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltriethylammonium chloride or 3-chloro-2-hydroxypropyldimethylbenzylammonium chloride or a combination of at least two thereof; Preferably, the mass ratio of the intermediate product to the organic ammonium chloride in step (2) is (1.5-4):1; Preferably, the reaction in step (2) is carried out in a solvent; Preferably, the solvent comprises isopropanol; Preferably, the mass ratio of the solvent to the intermediate product is (6-10):1; Preferably, the reaction in step (2) further comprises a catalyst B; Preferably, the catalyst B comprises NaOH and / or KOH; Preferably, the content of the catalyst B is 0.5-1.4% of the mass of the intermediate product; Preferably, the reaction in step (2) is carried out under reflux; Preferably, the reaction temperature in step (2) is 70-90°C; Preferably, the reaction time in step (2) is 6-8 hours.

6. The method for preparing the waterproof lock agent according to any one of claims 1 to 5, characterized in that: After the reaction in step (2) is completed, a post-treatment step is also included; Preferably, the post-treatment step comprises distillation under reduced pressure, washing and drying.

7. The method for preparing the waterproof lock agent according to any one of claims 1 to 6, characterized in that: The preparation method specifically comprises the following steps: (1) 30-40 parts by weight of alginic acid, 10-15 parts by weight of amino alcohol and 100-150 parts by weight of solvent are mixed, a protective gas is introduced, 0.2-0.4 parts by weight of catalyst A is added, and reflux reaction is carried out at 140-160° C. for 5-7 hours; after the reaction is completed, vacuum distillation, washing and drying are performed to obtain an intermediate product; (2) 15-20 parts by weight of the intermediate product of step (1), 5-10 parts by weight of ammonium chloride, 0.1-0.2 parts by weight of catalyst B and 120-150 parts by weight of solvent are mixed, and refluxed at 70-90° C. for 6-8 hours; after the reaction is completed, the mixture is distilled under reduced pressure, washed and dried to obtain the waterproof lock agent.

8. A waterproof lock agent, characterized in that: The waterproof locking agent is prepared by the preparation method of the waterproof locking agent according to any one of claims 1 to 7.

9. The waterproof lock agent according to claim 8, characterized in that: The EC of the waterproof lock agent 50 >60000mg / L; Preferably, the BOD5 / CODcr of the waterproof lock agent is greater than 29%; Preferably, in a 5 wt % NaCl aqueous solution at 120° C., the surface tension of the waterproof lock agent is less than 21 mN / m.

10. Use of the waterproof lock agent as claimed in claim 8 or 9 in drilling.

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