A high-temperature-resistant environment-friendly drilling fluid filtrate reducer based on humic acid and sodium alginate and a preparation method thereof

Abstract

The application discloses a high-temperature-resistant environment-friendly drilling fluid filtrate reducer based on humic acid and sodium alginate and a preparation method thereof, and belongs to the technical field of oil drilling engineering oilfields.Under the premise of not introducing sulfonic acid groups, humic acid and sodium alginate are selected as main raw materials of the filtrate reducer, a stable polymer structure is constructed through grafting acrylamide, N-vinylpyrrolidone and 4-acryloyl morpholine, the filtrate control ability under high temperature is effectively improved, no sulfonic acid groups are contained, and excellent environmental friendliness and degradability are achieved.Compared with existing filtrate reducers, the application has obvious advantages in aspects of raw material sources, synthesis cost, thermal stability and environmental protection performance, and is particularly suitable for high-temperature high-salt complex working conditions of a green drilling fluid system, and has a good popularization and application prospect.

Description

Technical Field

[0001] This invention relates to the field of oilfield technology in petroleum drilling engineering, and in particular to a high-temperature resistant and environmentally friendly drilling fluid filtration reducer based on humic acid and sodium alginate, and its preparation method. Background Technology

[0002] Currently, global oil and gas resources are facing increasingly severe challenges. Global oil and gas resources are gradually shifting towards deeper, ultra-deepering, and unconventional resources (such as shale oil and gas, and tight oil and gas). However, the exploitation of these unconventional resources typically requires higher temperatures, higher pressures, and more complex environmental conditions, placing higher demands on the various chemical additives used in the extraction process. In the drilling, fracturing, and oil production processes of oil and gas fields, filtration control agents, as a key chemical additive, are widely used to control the filtration properties of drilling mud to prevent water or other fluids from seeping into the surrounding rock formations, leading to the waste or pollution of oil and gas resources. Under high temperature and high pressure environments, traditional filtration control agents are prone to failure, leading to a decline in drilling fluid performance, which in turn can cause wellbore instability, reduced drilling efficiency, and even safety accidents. Furthermore, the chemical components used in traditional filtration control agents, especially certain polymers or additives, can pollute the environment, particularly during extraction in deep water or complex geological environments. This not only increases the environmental risks of oil and gas extraction but also leads to safety issues during the production process. While traditional filtration loss control agents can function effectively in conventional oil and gas extraction, they have significant limitations in terms of high temperature and pressure, environmental pollution, and the need for high efficiency. Currently, many high-temperature resistant filtration loss control agents rely on sulfonic acid groups, especially polymer-based agents. However, these agents degrade slowly in the environment, posing a significant environmental risk. Therefore, developing new filtration loss control agents with stronger temperature resistance, environmental friendliness, and better rheological control has become an urgent need for the oil and gas extraction industry. Summary of the Invention

[0003] The purpose of this invention is to provide a high-temperature resistant and environmentally friendly drilling fluid filtration reducer based on humic acid and sodium alginate, and its preparation method, in order to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides a high-temperature resistant and environmentally friendly drilling fluid filtration reducer based on humic acid and sodium alginate, comprising humic acid, sodium alginate, acrylamide, N-vinylpyrrolidone, 4-acryloylmorpholine, micro-crosslinking agent N,N′-methylenebisacrylamide, ammonium persulfate, and sodium bisulfite.

[0005] Preferably, by weight, it includes 1-5 parts humic acid, 1-4 parts sodium alginate, 3-10 parts acrylamide, 1-5 parts N-vinylpyrrolidone, 1-5 parts 4-acryloylmorpholine, 0.1-0.5 parts micro-crosslinking agent N,N′-methylenebisacrylamide, 0.08-0.16 parts ammonium persulfate, and 0.08-0.16 parts sodium bisulfite.

[0006] Preferably, the humic acid has an ash content of 10%, a moisture content of 8%, and an iron content of 0.3%.

[0007] Preferably, the sodium alginate contains 0.0002% arsenic, 0.001% lead, 0.04% iron, has a loss on drying of 22.0%, and a residue on ignition of 30.0-35.0%.

[0008] Preferably, the viscosity of a 10 g / L sodium alginate solution at 20°C is 0.02 Pa·s.

[0009] Preferably, the number-average molecular weight (Mn) of acrylamide is 71.08 g / mol; the number-average molecular weight (Mn) of 4-acryloylmorpholine is 141.17 g / mol; and the number-average molecular weight (Mn) of the micro-crosslinking agent N,N'-methylenebisacrylamide is 154.17 g / mol.

[0010] Preferably, the N-vinylpyrrolidone has a number-average molecular weight Mn of 111.14 g / mol and contains 100 ppm NaOH as a stabilizer.

[0011] Preferably, the purity of ammonium persulfate is ≥99%; the purity of sodium bisulfite is ≥99%; and the sodium hydroxide is analytical grade with a purity of ≥99%.

[0012] This invention also provides a method for preparing the above-mentioned high-temperature resistant and environmentally friendly drilling fluid filtration reducer based on humic acid and sodium alginate, specifically including the following steps:

[0013] S1. Weigh deionized water into a beaker and heat it to 60°C. Add humic acid and sodium alginate in sequence, stir to dissolve, and then adjust the pH to 7-8 with 5% NaOH solution.

[0014] S2. Take another deionized water in a beaker, add acrylamide, N-vinylpyrrolidone and 4-acryloylmorpholine in sequence, mix well and slowly pour into the solution obtained in step S1, stir well.

[0015] S3. Transfer the solution after stirring in step S2 to a three-necked flask, purge with nitrogen to remove oxygen, add ammonium persulfate and sodium bisulfite at a reaction temperature of 60-65℃, stir the reaction, add N,N′-methylenebisacrylamide after 30 min of reaction, and continue the polymerization reaction for 2-4 h. After the reaction is completed, the target product is obtained.

[0016] This invention selects humic acid and sodium alginate, natural organic polymers, as the main raw materials for the filtration loss reducing agent without introducing sulfonic acid groups. Humic acid is a complex organic compound formed from the long-term decomposition of plant and animal remains under natural conditions. It contains abundant functional groups, such as carboxyl, phenolic hydroxyl, and alcohol groups, which endow humic acid with good hydrophilicity and chemical reactivity. Sodium alginate, derived from brown algae, is an anionic polysaccharide with strong film-forming, gelling, and water-soluble properties, as well as excellent biocompatibility and biodegradability. Both are natural polymer materials that are not only abundant and widely available but also environmentally friendly. Based on this, the present invention synthesizes a novel high-temperature filtration loss reducer by using humic acid and sodium alginate as natural matrices, grafting functional monomers such as acrylamide (AM), N-vinylpyrrolidone (NVP), and 4-acryloylmorpholine (ACMO) via free radical polymerization, and simultaneously introducing a trace amount of crosslinking agent N,N'-methylenebisacrylamide (MBA) to construct a three-dimensional structural network through graft copolymerization. This results in a novel high-temperature filtration loss reducer that combines the reactivity of humic acid and the colloidal film-forming properties of sodium alginate with the thermal stability and structural strength of polymer segments, thereby achieving stable performance of the filtration loss reducer under high-temperature conditions.

[0017] Therefore, the high-temperature resistant and environmentally friendly drilling fluid filtration reducer based on humic acid and sodium alginate, and its preparation method, provided by the present invention, have the following beneficial effects:

[0018] (1) Humic acid and sodium alginate are materials of natural origin, with a wide range of raw material sources and low cost;

[0019] (2) Using humic acid and sodium alginate as the main components, the polymer structure does not contain sulfonic acid groups, which avoids the environmental pollution problem of sulfate ions generated after the traditional filtration loss reducer decomposes at high temperature, reduces the impact on the environment, and humic acid and sodium alginate also have good environmental protection performance and biodegradability, making them more in line with the requirements of green and environmentally friendly drilling.

[0020] (3) The multifunctional structure of humic acid can react effectively with polymer monomers, while sodium alginate enhances the blocking performance through its three-dimensional network colloidal properties. The two work together to form a high molecular polymer structure with good water solubility, high temperature resistance and low filtration loss. This filtration loss reducer has excellent filtration loss control ability in a high temperature environment of 180℃, and the API filtration loss can be controlled within 10mL. It also shows good salt and calcium stability.

[0021] (4) The synthesis cost of this filtration loss reduction agent system is low and the process is simple. It can not only play a stable role in the high temperature drilling environment for a long time, but also has good environmental adaptability and sustainable development advantages, and has strong economic feasibility and promotion potential.

[0022] The technical solution of the present invention will be further described in detail below through embodiments. Detailed Implementation

[0023] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the invention should be considered equivalent substitutions and are included within the scope of protection of the invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims and are all within the scope of protection of the invention.

[0024] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0025] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.

[0026] Unless otherwise specified, all reagents, instruments, and equipment used in this invention are those commonly used by those skilled in the art. Deionized water is distilled water prepared in-house.

[0027] Example 1

[0028] This embodiment provides a method for preparing a high-temperature resistant and environmentally friendly drilling fluid filtration reducer based on humic acid and sodium alginate, specifically including the following steps:

[0029] First, weigh 60g of deionized water into a beaker, heat the deionized water to 60℃, add 5 parts of humic acid and 2 parts of sodium alginate in sequence, place the beaker on a magnetic stirrer and stir to dissolve, then adjust the pH to 7-8 with 5% NaOH solution.

[0030] The second step involves weighing out 20g of deionized water, adding 6 parts of acrylamide, 3 parts of N-vinylpyrrolidone, and 3 parts of 4-acryloylmorpholine to the water in sequence, mixing well, and then slowly pouring the mixture into the solution obtained in the previous step, stirring until homogeneous.

[0031] Third, the solution, after being stirred evenly in the above steps, is transferred to a three-necked flask, and nitrogen gas is purged for 30 minutes to remove oxygen, while maintaining the reaction temperature at 60°C. 0.08 parts of ammonium persulfate and 0.08 parts of sodium bisulfite are added as initiators, and the reaction is stirred. After 30 minutes of reaction, 0.1 parts of N,N'-methylenebisacrylamide are added, and the polymerization reaction is continued for 3 hours to obtain the target product.

[0032] Example 2

[0033] This embodiment provides a method for preparing a high-temperature resistant and environmentally friendly drilling fluid filtration reducer based on humic acid and sodium alginate, specifically including the following steps:

[0034] First, weigh 60g of deionized water into a beaker, heat the deionized water to 60℃, add 5 parts of humic acid and 3 parts of sodium alginate in sequence, place the beaker on a magnetic stirrer and stir to dissolve, then adjust the pH to 7-8 with 5% NaOH solution.

[0035] The second step involves weighing out 20g of deionized water, adding 6 parts of acrylamide, 3 parts of N-vinylpyrrolidone, and 3 parts of 4-acryloylmorpholine to the water in sequence, mixing well, and then slowly pouring the mixture into the solution obtained in the previous step, stirring until homogeneous.

[0036] Third, the solution, after being stirred evenly in the above steps, is transferred to a three-necked flask, and nitrogen gas is purged for 30 minutes to remove oxygen, while maintaining the reaction temperature at 60°C. 0.1 parts of ammonium persulfate and 0.1 parts of sodium bisulfite are added as initiators, and the reaction is stirred. After 30 minutes of reaction, 0.2 parts of N,N'-methylenebisacrylamide are added, and the polymerization reaction is continued for 3 hours to obtain the target product.

[0037] Example 3

[0038] First, weigh 60g of deionized water into a beaker, heat the deionized water to 60℃, add 4 parts of humic acid and 1 part of sodium alginate in sequence, place the beaker on a magnetic stirrer and stir to dissolve, then adjust the pH to 7-8 with 5% NaOH solution.

[0039] In the second step, weigh out another 20g of deionized water, add 7 parts of acrylamide, 5 parts of N-vinylpyrrolidone, and 5 parts of 4-acryloylmorpholine to it in sequence, mix well, and then slowly pour it into the solution obtained in the above step, stirring until evenly mixed.

[0040] Third, the solution, after being stirred evenly in the above steps, is transferred to a three-necked flask, and nitrogen is purged for 30 minutes to remove oxygen, while maintaining the reaction temperature at 65°C. 0.08 parts of ammonium persulfate and 0.08 parts of sodium bisulfite are added as initiators, and the reaction is stirred. After 30 minutes of reaction, 0.3 parts of N,N'-methylenebisacrylamide are added, and the polymerization reaction is continued for 4 hours to obtain the target product.

[0041] Example 4

[0042] First, weigh 60g of deionized water into a beaker, heat the deionized water to 60℃, add 3 parts of humic acid and 1 part of sodium alginate in sequence, place the beaker on a magnetic stirrer and stir to dissolve, then adjust the pH to 7-8 with 5% NaOH solution.

[0043] The second step involves weighing out 20g of deionized water, adding 5 parts of acrylamide, 2 parts of N-vinylpyrrolidone, and 2 parts of 4-acryloylmorpholine to the water in sequence, mixing well, and then slowly pouring the mixture into the solution obtained in the previous step, stirring until homogeneous.

[0044] The third step involves transferring the thoroughly stirred solution from the previous step into a three-necked flask, purging with nitrogen for 30 minutes to remove oxygen, and maintaining the reaction temperature at 65°C. 0.08 parts of ammonium persulfate and 0.08 parts of sodium bisulfite are added as initiators, and the mixture is stirred. After 30 minutes of reaction, 0.1 parts of N,N'-methylenebisacrylamide are added, and the polymerization reaction continues for 3 hours to obtain the target product.

[0045] Existing sulfonated phenolic resin SMP-II was selected as Comparative Example 1.

[0046] Preparation of the freshwater-based slurry: Add 400ml of hot water to a high-speed stirring cup, set the stirring speed to 6000 rpm, and while stirring, add 12g of bentonite, 0.8g of sodium hydroxide, and 0.8g of anhydrous sodium carbonate in sequence. During stirring, use a glass rod to push the powder adhering to the cup wall into the cup and continue stirring for 2 hours. Then cover with plastic wrap and let it cure at room temperature for 24 hours. This is the pre-hydrated freshwater-based slurry.

[0047] Examples 1-4 and Comparative Example 1 were added to pre-hydrated freshwater-based slurry and stirred for 30 minutes at 8000 rpm using a variable frequency high-speed mixer. The stirred liquid was then poured into an aging tank and heated at 180°C for 16 hours. Subsequently, the liquid was transferred from the aging tank to a high-speed stirring cup and stirred for 5 minutes at 8000 rpm using a variable frequency high-speed mixer. The filtration loss of the liquid was measured using an API filtration loss meter, and the results are shown in Table 1 below.

[0048] Table 1. Filtration performance of the filtration reducer

[0049] Prehydrated base slurry Filtration loss (mL) blank 71 1.0wt% Example 1 8.6 1.0wt% Example 2 9.2 1.0wt% Example 3 9.0 1.0wt% Example 4 8.4 1.0wt% Comparative Example 1 15.8

[0050] As shown in Table 1, the filtration loss of Examples 1-4 was reduced by 80%-85% compared to the blank example, demonstrating superior filtration loss reduction performance compared to traditional sulfonated phenolic resin.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A high-temperature resistant and environmentally friendly drilling fluid filtration reducer based on humic acid and sodium alginate, characterized in that, Including humic acid, sodium alginate, acrylamide, N-vinylpyrrolidone, 4-acryloylmorpholine, micro-crosslinking agent N,N′-methylenebisacrylamide, ammonium persulfate, and sodium bisulfite; The humic acid contains 10% ash, 8% moisture, and 0.3% iron. Sodium alginate contains 0.0002% arsenic, 0.001% lead, 0.04% iron, has a drying loss of 22.0%, and a residue on ignition of 30.0-35.0%. The number-average molecular weight (Mn) of the microcrosslinking agent N,N'-methylenebisacrylamide is 154.17 g / mol; The preparation method of the above-mentioned filtration loss reducing agent includes the following steps: S1. Weigh deionized water into a beaker and heat it to 60°C. Add humic acid and sodium alginate in sequence, stir to dissolve, and then adjust the pH to 7-8 with 5% NaOH solution. S2. Take another deionized water in a beaker, add acrylamide, N-vinylpyrrolidone and 4-acryloylmorpholine in sequence, mix well and slowly pour into the solution obtained in step S1, stir well. S3. Transfer the solution after stirring in step S2 to a three-necked flask, purge with nitrogen to remove oxygen, add ammonium persulfate and sodium bisulfite at a reaction temperature of 60-65℃, stir the reaction, add N,N′-methylenebisacrylamide after 30 min of reaction, and continue the polymerization reaction for 2-4 h. After the reaction is completed, the target product is obtained.

2. The high-temperature resistant and environmentally friendly drilling fluid filtration reducer based on humic acid and sodium alginate according to claim 1, characterized in that: By weight, it includes 1-5 parts humic acid, 1-4 parts sodium alginate, 3-10 parts acrylamide, 1-5 parts N-vinylpyrrolidone, 1-5 parts 4-acryloylmorpholine, 0.1-0.5 parts micro-crosslinking agent N,N′-methylenebisacrylamide, 0.08-0.16 parts ammonium persulfate, and 0.08-0.16 parts sodium bisulfite.

3. The high-temperature resistant and environmentally friendly drilling fluid filtration reducer based on humic acid and sodium alginate according to claim 1, characterized in that: The viscosity of a 10 g / L sodium alginate solution at 20 °C is 0.02 Pa·s.

4. The high-temperature resistant and environmentally friendly drilling fluid filtration reducer based on humic acid and sodium alginate according to claim 1, characterized in that: The number-average molecular weight (Mn) of acrylamide is 71.08 g / mol; the number-average molecular weight (Mn) of 4-acryloylmorpholine is 141.17 g / mol.

5. The high-temperature resistant and environmentally friendly drilling fluid filtration reducer based on humic acid and sodium alginate according to claim 1, characterized in that: The number-average molecular weight (Mn) of N-vinylpyrrolidone is 111.14 g / mol, and it contains 100 ppm of NaOH as a stabilizer.

6. The high-temperature resistant and environmentally friendly drilling fluid filtration reducer based on humic acid and sodium alginate according to claim 1, characterized in that: The purity of ammonium persulfate is ≥99%; the purity of sodium bisulfite is ≥99%; and the purity of sodium hydroxide is analytical grade, ≥99%.