A solid-free drilling fluid containing polysaccharide and its preparation method and application

Abstract

The application relates to the technical field of oilfield exploitation, and discloses a solid-phase-free drilling fluid containing polysaccharide as well as a preparation method and application of the drilling fluid. The drilling fluid is prepared by mixing plugging anti-sloughing agents, polysaccharide filtrate reducers and viscosity increasing agents, wherein the plugging anti-sloughing agent is prepared by taking acrylamide, N-vinyl pyrrolidone and a functional monomer as raw materials, and performing emulsion cross-linking polymerization under the action of an initiator; the functional monomer structure contains a large number of quaternary ammonium cations and sulfonic acid groups, and simultaneously contains a biphenyl structure; the quaternary ammonium cations can produce strong adsorption with shale and silt, thereby improving the plugging effect and temperature resistance of the drilling fluid; in addition, the polysaccharide is used as the filtrate reducer of the drilling fluid, and after the polysaccharide is dissolved in water, a high-viscosity colloid can be formed to effectively plug formation pores, reduce filtrate invasion and reduce the filtration loss; in addition, the polysaccharide filtrate reducer can improve the viscosity of the drilling fluid, enhance the rock-carrying capacity of the drilling fluid and improve the cleaning effect of a wellbore.

Description

Technical Field

[0001] This invention relates to the field of oilfield development technology, specifically to a polysaccharide-containing solids-free drilling fluid, its preparation method, and its application. Background Technology

[0002] Solid-free drilling fluids are composed of organic polymers and salts. Compared with traditional solid-phase drilling fluids containing bentonite, they have poorer plugging effect, are prone to leakage, and have weaker temperature resistance, which poses significant problems in practical applications. Therefore, it is of great significance to prepare a solid-free drilling fluid with excellent comprehensive performance.

[0003] The invention patent with application number CN202010753618.0 discloses a solid-free anti-pollution drilling fluid. By constructing a temperature and salt resistance flow modifier with an "associative micro-crosslinked structure", the comprehensive performance of the drilling fluid, such as temperature and salt resistance, is improved. Therefore, by adjusting the composition of the drilling fluid, a solid-free drilling fluid with excellent comprehensive performance can be developed. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] To address the shortcomings of existing technologies, this invention provides a polysaccharide-containing solids-free drilling fluid, its preparation method, and its application.

[0006] (II) Technical Solution

[0007] A polysaccharide-containing solids-free drilling fluid, comprising the following raw materials measured in parts by weight:

[0008] 4-5 parts of sealing and anti-collapse agent, 4.5-6.5 parts of polysaccharide filtration loss reducer, 1.5-2.5 parts of thickener, 0.5-1 part of stabilizer, and 80-100 parts of water;

[0009] The preparation method of the sealing and anti-collapse agent includes the following steps:

[0010] Step A: Add emulsifier Span 80 to white oil and mechanically stir until a homogeneous solution is formed, thus forming the oil phase;

[0011] Step B: Add acrylamide, N-vinylpyrrolidone, functional monomer and sodium bisulfite to purified water, stir and mix evenly to form an aqueous phase;

[0012] Step C: Add the oil phase dropwise to the aqueous phase. After the addition is complete, stir and emulsify for 20-40 minutes. Then raise the temperature to 70-80℃ and add potassium persulfate at the same time. After the addition is complete, continue stirring and polymerizing for 4-8 hours. Stop heating, cool down and discharge the material to obtain the sealing and anti-collapse agent.

[0013] As a further aspect of the present invention, the method for preparing the functional monomer includes the following steps:

[0014] Step 1: Purge nitrogen into the polymerization reactor to purge air. Then, add oxamanic anhydride and N,N-dimethylformamide into the polymerization reactor. After the addition is complete, start stirring. Under stirring conditions, add 2,3-dihydroxypropyl-trimethylammonium chloride and accelerator into the polymerization reactor. After the addition is complete, raise the temperature to 60-70℃ and maintain the temperature for 12-18 hours. Then, cool down and discharge the material, collect the product, and obtain the intermediate material.

[0015] Step 2: Add the intermediate material and dimethyl sulfoxide to the reactor, stir and mix well, and purge with nitrogen for protection. Then, under stirring conditions, add 2-amino-5,7-naphthalenedisulfonic acid and catalyst to the reactor, stir well, raise the temperature to 90-100℃, keep it at that temperature for 4-8 hours, stop heating, and separate the product to obtain the functional monomer.

[0016] As a further aspect of the present invention, in step one, the molar ratio of the oxanoic anhydride and 2,3-dihydroxypropyl-trimethylammonium chloride is 1:1.1-1.2.

[0017] As a further aspect of the present invention, in step one, the accelerator is p-toluenesulfonic acid.

[0018] As a further aspect of the present invention, in step two, the catalyst is a boron trifluoride diethyl ether complex.

[0019] In the above technical solution, oxaic anhydride and 2,3-dihydroxypropyl-trimethylammonium chloride are first used as reactants. The anhydride groups in their structures first undergo ring-opening esterification with the hydroxyl groups to obtain an intermediate containing both carboxyl and hydroxyl groups in its structure. Then, under the action of a promoter, the intermediate undergoes polycondensation to obtain an intermediate material with ester bonds and an alternating block structure. Next, under the action of a catalyst, the epoxy groups in the intermediate material structure can undergo a ring-opening addition reaction with the amino groups in the 2-amino-5,7-naphthalenedisulfonic acid structure, thereby introducing sulfonic acid groups into the intermediate material molecular chain to obtain a functional monomer.

[0020] Because the functional monomer contains unsaturated alkenyl functional groups, a sealing and anti-collapse agent with a three-dimensional cross-linked network structure can be prepared by cross-linking polymerization with monomers acrylamide and N-vinylpyrrolidone via emulsion polymerization.

[0021] As a further aspect of the present invention, the polysaccharide filtration reducer is carboxymethyl starch or carboxymethyl cellulose.

[0022] As a further aspect of the present invention, the thickener is sodium alginate.

[0023] As a further aspect of the present invention, the stabilizer is potassium polyacrylate.

[0024] A method for preparing a polysaccharide-containing solids-free drilling fluid includes the following steps:

[0025] Step 1: Weigh and prepare all the raw materials according to their respective weight proportions;

[0026] The second step is to add all the raw materials into the mixer, control the stirring speed to 3000-5000 r / min, and mechanically stir for 20-40 minutes to obtain solids-free drilling fluid.

[0027] Application of a polysaccharide-containing solids-free drilling fluid, which is used in the field of oilfield development.

[0028] (iii) Beneficial technical effects

[0029] The functional monomer structure prepared in this invention contains a large number of quaternary ammonium cations and sulfonic acid groups, as well as a biphenyl structure. Using this as a polymerizing monomer, it undergoes free radical polymerization with other monomers to obtain a sealing and anti-collapse agent with a cross-linked structure. The quaternary ammonium cations exhibit strong adsorption with shale and silt, and can also intercalate into the soil, resulting in a strong adsorption effect between the sealing and anti-collapse agent and the shale and soil, thus forming a dense sealing layer. Furthermore, the cross-linked network structure can extend into fractures through capillary action and efficiently encapsulate clay, forming a dense mud cake, thereby effectively sealing micro-fractures and pores. In addition, the presence of sulfonic acid groups increases the sealing and anti-collapse agent's sensitivity to salt, while the presence of rigid ring structures improves the stability of the anti-collapse agent's molecular chain and enhances the drilling fluid's temperature resistance.

[0030] This invention uses polysaccharides as a filtration reducer for drilling fluid. When polysaccharides dissolve in water, they can form a high-viscosity colloid that effectively seals formation pores, reduces filtrate intrusion, and lowers filtration loss. Furthermore, polysaccharide filtration reducers can increase the viscosity of drilling fluid, enhance its rock-carrying capacity, and improve wellbore cleaning. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 Infrared analysis test results for functional units. Detailed Implementation

[0033] To facilitate understanding of the present invention, a more complete description will be provided below. Preferred embodiments of the invention are given below. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0034] Preparation Example 1

[0035] Preparation of sealing and anti-collapse agent:

[0036] Step A: Add 0.2g of emulsifier Span 80 to 1mL of white oil and mechanically stir until a homogeneous solution is formed, thus forming the oil phase;

[0037] Step B: Add 20g acrylamide, 8g N-vinylpyrrolidone, 1g functional monomer and 0.2g sodium bisulfite to 50mL purified water, stir and mix well to form an aqueous phase;

[0038] Step C: Add the oil phase dropwise to the aqueous phase. After the addition is complete, stir and emulsify for 30 minutes. Then raise the temperature to 75°C and add 0.1g of potassium persulfate. After the addition is complete, continue stirring and polymerization for 6 hours. Stop heating, cool down and discharge the material to obtain the sealing and anti-collapse agent.

[0039] The preparation method of the functional monomer includes the following steps:

[0040] Step 1: Purge nitrogen gas into the polymerization reactor to purge air. Then, add 0.1g of oxamanic anhydride and N,N-dimethylformamide to the polymerization reactor. After the addition is complete, start stirring. Under stirring conditions, add 0.12g of 2,3-dihydroxypropyl-trimethylammonium chloride and 0.01g of p-toluenesulfonic acid to the polymerization reactor. After the addition is complete, raise the temperature to 65℃ and maintain the temperature for 16 hours. Then, cool down and discharge the material, collect the product, and obtain the intermediate material.

[0041] Step 2: Add 0.5g of intermediate material and dimethyl sulfoxide to the reaction vessel, stir and mix well, and purge with nitrogen for protection. Then, under stirring conditions, add 0.1g of 2-amino-5,7-naphthalenedisulfonic acid and 0.02g of boron trifluoride diethyl ether complex to the reaction vessel, stir well, raise the temperature to 95℃, keep it at that temperature for 6 hours, stop heating, and separate the product to obtain the functional monomer.

[0042] Figure 1 Infrared analysis test pattern of functional unit, where 3419 cm -1 The characteristic absorption peak appearing at 3308 cm⁻¹ is the characteristic absorption peak of NH. -1 The characteristic absorption peak appearing at 3073 cm⁻¹ is the characteristic absorption peak of hydroxyl groups. -1 The characteristic absorption peak appearing at 3002 cm⁻¹ is a characteristic absorption peak of the benzene ring skeleton.-1 The characteristic absorption peak appearing at 1742 cm⁻¹ is the hydrocarbon absorption peak of an unsaturated carbon-carbon double bond. -1 The characteristic absorption peak appearing at this point is the C=O characteristic absorption peak of the ester bond.

[0043] Preparation Example 2

[0044] Preparation of sealing and anti-collapse agent:

[0045] Step A: Add 0.3g of emulsifier Span 80 to 1.5mL of white oil and stir mechanically until a homogeneous solution is formed, thus forming the oil phase;

[0046] Step B: Add 24g acrylamide, 10g N-vinylpyrrolidone, 1.2g functional monomer and 0.3g sodium bisulfite to 60mL purified water, stir and mix evenly to form an aqueous phase;

[0047] Step C: Add the oil phase dropwise to the aqueous phase. After the addition is complete, stir and emulsify for 30 minutes. Then raise the temperature to 75°C and add 0.2g of potassium persulfate. After the addition is complete, continue stirring and polymerization for 6 hours. Stop heating, cool down and discharge the material to obtain the sealing and anti-collapse agent.

[0048] The preparation method of the functional monomer is the same as that in Preparation Example 1.

[0049] Example 1, a polysaccharide-containing solids-free drilling fluid, comprising the following raw materials measured in parts by weight:

[0050] 4 parts sealing and anti-collapse agent, 4.5 parts carboxymethyl starch, 1.5 parts sodium alginate, 0.5 parts potassium polyacrylate, and 80 parts water;

[0051] The method for preparing the solids-free drilling fluid includes the following steps:

[0052] Step 1: Weigh and prepare all the raw materials according to their respective weight proportions;

[0053] The second step is to add all the raw materials into the mixer, control the stirring speed to 3000 r / min, and mechanically stir for 40 minutes to obtain solids-free drilling fluid.

[0054] The preparation method of the sealing and anti-collapse agent is shown in the preparation example, and the same applies to the following.

[0055] Example 2, a polysaccharide-containing solids-free drilling fluid, comprising the following raw materials measured in parts by weight:

[0056] 4.8 parts sealing and anti-collapse agent, 5 parts carboxymethyl cellulose, 2 parts sodium alginate, 0.6 parts potassium polyacrylate, and 90 parts water;

[0057] The method for preparing the solids-free drilling fluid includes the following steps:

[0058] Step 1: Weigh and prepare all the raw materials according to their respective weight proportions;

[0059] The second step is to add all the raw materials into the mixer, control the stirring speed to 4000 r / min, and mechanically stir for 30 minutes to obtain solids-free drilling fluid.

[0060] Example 3, a polysaccharide-containing solids-free drilling fluid, comprising the following raw materials measured in parts by weight:

[0061] 5 parts sealing and anti-collapse agent, 6.5 parts carboxymethyl cellulose, 2.5 parts sodium alginate, 1 part potassium polyacrylate, and 100 parts water;

[0062] The method for preparing the solids-free drilling fluid includes the following steps:

[0063] Step 1: Weigh and prepare all the raw materials according to their respective weight proportions;

[0064] The second step is to add all the raw materials into the mixer, control the stirring speed to 5000 r / min, and mechanically stir for 20 minutes to obtain solids-free drilling fluid.

[0065] Comparative Example 1, a polysaccharide-containing solids-free drilling fluid, comprising the following raw materials measured in parts by weight:

[0066] 4.8 parts sealing and anti-collapse agent, 5 parts carboxymethyl cellulose, 2 parts sodium alginate, 0.6 parts potassium polyacrylate, and 90 parts water;

[0067] The method for preparing the solids-free drilling fluid includes the following steps:

[0068] Step 1: Weigh and prepare all the raw materials according to their respective weight proportions;

[0069] The second step is to add all the raw materials into the mixer, control the stirring speed to 4000 r / min, and mechanically stir for 30 minutes to obtain solids-free drilling fluid.

[0070] The difference between the sealing and anti-collapse agent and the preparation example 1 is that no functional monomer is added, but all other aspects are the same.

[0071] Performance testing

[0072] The drilling fluids in the examples and comparative examples were heat-aged at 180°C for 16 hours. According to standard GB / T16783.1-2014, filtration loss was tested. Generally, lower filtration loss indicates better sealing and anti-collapse effects of the drilling fluid, and vice versa. The test results are recorded in the table below:

[0073] Table 1

[0074]

[0075] Analysis of the test results shows that the plugging and anti-collapse agent prepared in the embodiments of the present invention has good high temperature resistance and plugging and anti-collapse performance. After removing the functional monomers in the plugging and anti-collapse agent, the modification effect brought by each functional group in the functional monomer structure cannot be utilized, resulting in a significant reduction in various properties of the drilling fluid.

[0076] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

Claims

1. A polysaccharide-containing solids-free drilling fluid, characterized in that, Including the following raw materials measured in parts by weight: 4-5 parts of sealing and anti-collapse agent, 4.5-6.5 parts of polysaccharide filtration loss reducer, 1.5-2.5 parts of thickener, 0.5-1 part of stabilizer, and 80-100 parts of water; The preparation method of the sealing and anti-collapse agent includes the following steps: Step A: Add emulsifier Span 80 to white oil and mechanically stir until a homogeneous solution is formed, thus forming the oil phase; Step B: Add acrylamide, N-vinylpyrrolidone, functional monomer and sodium bisulfite to purified water, stir and mix evenly to form an aqueous phase; Step C: Add the oil phase to the aqueous phase, stir and emulsify for 20-40 minutes, raise the temperature to 70-80℃, add potassium persulfate at the same time, continue stirring and polymerize for 4-8 hours, stop heating, cool down and discharge the material to obtain the sealing and anti-collapse agent. The solid-liquid ratio of Span 80, white oil, acrylamide, N-vinylpyrrolidone, functional monomer, sodium bisulfite, purified water, and potassium persulfate is: 0.1-0.3g:0.5-1.5mL:15-25g:6-10g:0.5-1.5g:0.1-0.3g:40-60mL:0.1-0.2g; The preparation method of the functional monomer includes the following steps: Step 1: Introduce nitrogen into the polymerization reactor to purge air. Add oxamanic anhydride and N,N-dimethylformamide into the polymerization reactor and start stirring. Under stirring conditions, add 2,3-dihydroxypropyl-trimethylammonium chloride and accelerator into the polymerization reactor. Raise the temperature to 60-70℃ and maintain the temperature for 12-18 hours. Then, cool down and discharge the material, collect the product, and obtain the intermediate material. Step 2: Add the intermediate material and dimethyl sulfoxide to the reactor, stir and mix well, and purge with nitrogen for protection. Under stirring conditions, add 2-amino-5,7-naphthalenedisulfonic acid and catalyst to the reactor, stir well, raise the temperature to 90-100℃, keep it at that temperature for 4-8 hours, stop heating, and separate the product to obtain the functional monomer. The polysaccharide filtration reducer is carboxymethyl starch or carboxymethyl cellulose; The thickener is sodium alginate; The stabilizer is potassium polyacrylate.

2. The polysaccharide-containing solids-free drilling fluid according to claim 1, characterized in that, In step one, the molar ratio of the oxanoic anhydride and 2,3-dihydroxypropyl-trimethylammonium chloride is 1:1.1-1.

2.

3. The polysaccharide-containing solids-free drilling fluid according to claim 1, characterized in that, In step one, the accelerator is p-toluenesulfonic acid.

4. The polysaccharide-containing solids-free drilling fluid according to claim 1, characterized in that, In step two, the catalyst is a boron trifluoride diethyl ether complex.

5. A method for preparing a polysaccharide-containing solids-free drilling fluid as described in any one of claims 1-4, characterized in that, Includes the following steps: Step 1: Weigh and prepare all the raw materials according to their respective weight proportions; The second step is to add all the raw materials into the mixer, control the stirring speed to 3000-5000 r / min, and mechanically stir for 20-40 minutes to obtain solids-free drilling fluid.

6. An application of the polysaccharide-containing solids-free drilling fluid as described in any one of claims 1-4, characterized in that, The solids-free drilling fluid is applied to the field of oilfield development.

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