A kind of brine-based reservoir drilling fluid and its preparation method

Abstract

The present invention belongs to the technical field of drilling fluids, and discloses a brine-based reservoir-specific drilling fluid and a preparation method thereof, wherein the brine-based reservoir-specific drilling fluid comprises 100 parts by weight of oilfield brine, 1-3 parts by weight of polyethyleneimine-modified cellulose, 1.5-2.8 parts by weight of lignin, and 1.4-2.2 parts by weight of anhydrous polyol; the modified cellulose of the present invention contains a long alkyl chain, which can form a unique hydrophobic association, and is conducive to improving the viscosity and shear resistance of the cellulose-based drilling fluid. The modified cellulose contains a large number of groups such as carboxyl and amino groups, which can be well adsorbed on the surface of bentonite silicate, inhibit the hydration of its grain surface, reduce the expansion of the crystal layer, and have better anti-swelling inhibition performance. The drilling fluid of the present invention has the advantages of small filtration loss and high heat rolling recovery rate, and shows good filtration loss reduction and high temperature resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of drilling fluid, in particular to a brine-based reservoir drilling fluid and a preparation method thereof. Background Art

[0002] Drilling fluid is widely used in drilling engineering and oil and gas production. Drilling fluid can be divided into water-based, mud-based, emulsion-based, foam-based, etc. Brine as the base fluid of drilling fluid has the advantages of low cost, simple preparation, convenient construction, and simple maintenance and management. Drilling fluid mainly consists of base slurry, viscosity enhancer, lubricating additive, filtration reducer, etc. Polymers such as polyethyleneimine and cellulose have the advantages of being green, environmentally friendly, cheap and easy to obtain, and have excellent viscosity-enhancing effects. They are widely used in drilling fluids, oil and gas production, etc. Improving the anti-swelling inhibition, anti-shear, and filtration loss reduction properties of cellulose-based drilling fluids has important applications.

[0003] The invention patent with the announcement number CN110591670B discloses that low-viscosity carboxymethyl cellulose is grafted and modified with monomers such as acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and dimethyldiallylammonium chloride, and the obtained fluid loss reducer and drilling fluid have good fluid loss reduction performance, and are environmentally friendly and have excellent temperature resistance. However, the patent does not improve the anti-swelling inhibition and shear resistance of the drilling fluid.

[0004] The invention patent with announcement number CN109652031B discloses that branched polyethyleneimine with catechol groups grafted on the main chain is used as a strong inhibition and strong cementation well wall stabilizer, and the drilling fluid obtained by compounding with nano plugging agents, aluminum-based polymers, etc. can effectively inhibit the hydration and expansion of shale and solve the problem of well wall instability. However, the patent does not improve the performance of drilling fluid in reducing filtration and anti-shearing. Summary of the invention

[0005] The invention solves the problem that the cellulose-based drilling fluid has poor anti-swelling inhibition, anti-shearing and other properties.

[0006] The technical scheme of the present invention is: a brine-based reservoir drilling fluid, comprising 100 parts by weight of oilfield brine, 1-3 parts by weight of polyethyleneimine modified cellulose, 1.5-2.8 parts by weight of lignin, and 1.4-2.2 parts by weight of anhydrous polymer alcohol.

[0007] The preparation method of polyethyleneimine modified cellulose is as follows: add cellulose and polyethyleneimine to N,N-dimethylformamide, add a modifier and 4-dimethylaminopyridine after stirring, heat to 50-70°C and stir to react for 12-18h, add ethanol to dilute the solution, filter, wash with ethanol, and dry to obtain polyethyleneimine modified cellulose.

[0008] The structural formula of the modifier is , in the structural formula, n is 14-18.

[0009] Preferably, the amount of cellulose is 100 parts by weight, the amount of polyethyleneimine is 15-50 parts by weight, the amount of the modifier is 6-25 parts by weight, and the amount of 4-dimethylaminopyridine is 1.2-5 parts by weight.

[0010] Preferably, the preparation method of the modifier is:

[0011] Step (1), add 100 parts by weight of diethanolamine, 284-340 parts by weight of bromoalkane, and 136-144 parts by weight of potassium carbonate to acetonitrile, stir and react at room temperature for 24-36 hours, concentrate under reduced pressure, separate the product by silica gel column chromatography, and use dichloromethane and methanol solution as eluent to obtain a precursor.

[0012] Step (2), in an ice water bath, add 100 parts by weight of the precursor, 110-140 parts by weight of trimellitic anhydride chloride, and 52-60 parts by weight of pyridine to dichloromethane, then stir the reaction at room temperature for 12-18 hours, concentrate under reduced pressure, and separate the product by silica gel column chromatography, using dichloromethane and methanol solution as eluents to obtain a modifier.

[0013] Preferably, the bromoalkane is any one of 1-bromotetradecane, 1-bromopentadecane, 1-bromohexadecane, 1-bromoheptadecane and 1-bromooctadecane.

[0014] Preferably, the method for preparing the brine-based reservoir drilling fluid is as follows: polyethyleneimine-modified cellulose, lignin, and anhydrous polyol are added to oilfield brine, and stirred to obtain the brine-based reservoir drilling fluid.

[0015] The present invention has the following technical effects: using diethanolamine, bromoalkane, trimellitic anhydride chloride and the like as reactants, a modifier containing anhydride groups and alkyl long chains is prepared. Using the modifier as a crosslinking agent, the anhydride groups thereof react with the hydroxyl groups of cellulose and the amino groups of polyethyleneimine to crosslink, thereby realizing a grafting reaction between cellulose and polyethyleneimine to obtain polyethyleneimine-modified cellulose.

[0016] The present invention uses oilfield brine as the base fluid of the drilling fluid, polyethyleneimine-modified cellulose, lignin, and anhydrous polyol as auxiliary agents, and compounding to obtain a brine-based reservoir drilling fluid. Polyethyleneimine-modified cellulose contains long alkyl chains, which can form a unique hydrophobic association between the molecular chains of the modified cellulose, which is beneficial to improving the viscosity and shear resistance of the cellulose-based drilling fluid. At the same time, after the cellulose is grafted with the polyethyleneimine molecular chain, a large number of groups such as carboxyl and amino groups are introduced, which improves the water solubility of the modified cellulose, and there is a good interaction between the amino groups and bentonite silicate, which can make the modified cellulose adsorbed on the surface of the bentonite silicate, inhibit the hydration of its grain surface, reduce the expansion of the crystal layer, thereby reducing the expansion height, having better anti-swelling inhibition performance, and being beneficial to solving the problem of well wall instability. In addition, the drilling fluid of the present invention has the advantages of small filtration loss, high hot rolling recovery rate, etc., and shows good filtration loss reduction and high temperature resistance. At the same time, the drilling fluid of the present invention has the advantages of good lubrication performance, natural degradation of cellulose, and is helpful to protect the reservoir. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is the reaction formula for preparing the modifier.

[0018] Figure 2 This is the reaction formula for preparing polyethyleneimine-modified cellulose. DETAILED DESCRIPTION

[0019] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0020] The anhydrous polyol in the present invention is of model JMZ-1, Jinan Lanjue Trading Co., Ltd. Cellulose, Shandong Xinxiong Biotechnology Co., Ltd. Oilfield brine was obtained from Well 7-27-Slant 16 of Gudong Oilfield.

[0021] Example 1

[0022] (1) Add 0.5 g of diethanolamine, 1.57 g of 1-bromohexadecane, and 0.72 g of potassium carbonate to acetonitrile, stir and react at room temperature for 24 h, and concentrate under reduced pressure. The product is separated by silica gel column chromatography using dichloromethane and methanol solution as eluents to obtain a precursor.

[0023] (2) In an ice-water bath, add 1 g of the precursor, 1.26 g of trimellitic anhydride chloride, and 0.58 g of pyridine to 15 mL of dichloromethane, and then stir the reaction at room temperature for 18 h. Concentrate under reduced pressure, and separate the product by silica gel column chromatography using dichloromethane and methanol solution as eluents to obtain a modifier.

[0024] (3) Add 2 g of cellulose and 0.3 g of polyethyleneimine to 40 mL of N,N-dimethylformamide, stir, then add 0.12 g of a modifier and 24 mg of 4-dimethylaminopyridine. Heat to 60 °C and stir for 12 h. Add ethanol to dilute the solution. Filter, wash with ethanol, and dry to obtain polyethyleneimine-modified cellulose.

[0025] (4) Add 10 g of polyethyleneimine-modified cellulose, 22 g of lignin, and 18 g of anhydrous polyol to 1000 g of oilfield brine, and stir to obtain a brine-based reservoir drilling fluid.

[0026] Example 2

[0027] (1) Add 0.5 g of diethanolamine, 1.7 g of 1-bromooctadecane, and 0.68 g of potassium carbonate to acetonitrile, stir the reaction at room temperature for 36 h, and concentrate under reduced pressure. The product is separated by silica gel column chromatography using dichloromethane and methanol solution as eluents to obtain a precursor.

[0028] (2) In an ice-water bath, add 1 g of the precursor, 1.4 g of trimellitic anhydride chloride, and 0.52 g of pyridine to 15 mL of dichloromethane, and then stir the reaction at room temperature for 18 h. Concentrate under reduced pressure, and separate the product by silica gel column chromatography using dichloromethane and methanol solution as eluents to obtain a modifier.

[0029] (3) Add 2 g of cellulose and 1 g of polyethyleneimine to 60 mL of N,N-dimethylformamide, stir, then add 0.5 g of a modifier and 100 mg of 4-dimethylaminopyridine. Heat to 50 °C and stir for 18 h. Add ethanol to dilute the solution. Filter, wash with ethanol, and dry to obtain polyethyleneimine-modified cellulose.

[0030] (4) Add 15 g of polyethyleneimine-modified cellulose, 28 g of lignin, and 15 g of anhydrous polyol to 1000 g of oilfield brine, and stir to obtain a brine-based reservoir drilling fluid.

[0031] Example 3

[0032] (1) Add 0.5 g of diethanolamine, 1.42 g of 1-bromotetradecane, and 0.68 g of potassium carbonate to acetonitrile, stir and react at room temperature for 36 h, and concentrate under reduced pressure. The product is separated by silica gel column chromatography using dichloromethane and methanol solution as eluents to obtain a precursor.

[0033] (2) In an ice-water bath, add 1 g of the precursor, 1.1 g of trimellitic anhydride chloride, and 0.6 g of pyridine to 15 mL of dichloromethane, and then stir the reaction at room temperature for 12 h. Concentrate under reduced pressure and separate the product by silica gel column chromatography using dichloromethane and methanol solution as eluents to obtain a modifier.

[0034] (3) Add 2 g of cellulose and 0.5 g of polyethyleneimine to 50 mL of N,N-dimethylformamide, stir, then add 0.26 g of a modifier and 52 mg of 4-dimethylaminopyridine. Heat to 70 °C and stir for 12 h. Add ethanol to dilute the solution. Filter, wash with ethanol, and dry to obtain polyethyleneimine-modified cellulose.

[0035] (4) Add 22 g of polyethyleneimine-modified cellulose, 28 g of lignin, and 14 g of anhydrous polyol to 1000 g of oilfield brine, and stir to obtain a brine-based reservoir drilling fluid.

[0036] Example 4

[0037] (1) Add 2 g of cellulose and 0.72 g of polyethyleneimine to 50 mL of N,N-dimethylformamide, stir, add 0.37 g of a modifier (prepared according to the method of Example 1) and 74 mg of 4-dimethylaminopyridine, heat to 60°C and stir for 18 h, add ethanol to dilute the solution, filter, wash with ethanol, and dry to obtain polyethyleneimine-modified cellulose.

[0038] (2) Add 30 g of polyethyleneimine-modified cellulose, 15 g of lignin, and 22 g of anhydrous polyol to 1000 g of oilfield brine, and stir to obtain a brine-based reservoir drilling fluid.

[0039] Comparative Example 1

[0040] (1) Add 22 g of lignin and 18 g of anhydrous polyol to 1000 g of oilfield brine and stir to obtain a brine-based reservoir drilling fluid.

[0041] Comparative Example 2

[0042] (1) Add 10 g of cellulose, 22 g of lignin, and 18 g of anhydrous polyol to 1000 g of oilfield brine, and stir to obtain a brine-based reservoir drilling fluid.

[0043] Comparative Example 3

[0044] (1) Add 2 g of cellulose and 0.3 g of polyethyleneimine to 40 mL of N,N-dimethylformamide, stir, then add 0.12 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride and 24 mg of 4-dimethylaminopyridine, heat to 60 °C and stir for 12 h, add ethanol to dilute the solution, filter, wash with ethanol, and dry to obtain polyethyleneimine-modified cellulose.

[0045] (2) Add 10 g of polyethyleneimine-modified cellulose, 22 g of lignin, and 18 g of anhydrous polyol to 1000 g of oilfield brine, and stir to obtain a brine-based reservoir drilling fluid.

[0046] Linear expansion test: The bentonite is compacted by a molding machine for 4 minutes at a pressure of 15 MPa to make a sample, which is then loaded into a dilatometer, and drilling fluid is added to record the expansion height at different times. The smaller the expansion height, the better the anti-swelling inhibition performance.

[0047] The polyethyleneimine-modified cellulose prepared in each example, the cellulose in comparative example 2, and the polyethyleneimine-modified cellulose in comparative example 3 were added to 1 L of distilled water, and after stirring, the initial viscosity and the viscosity after shearing for 1 h were tested using a rheometer at a shear rate of 170 s -1 The test results are shown in Table 1-2.

[0048] Table 1 Viscosity test of polyethyleneimine modified cellulose

[0049]

[0050] Table 2 Anti-swelling inhibition performance test

[0051]

[0052] According to GB / T 16783.1-2014 standard, the room temperature filter loss and hot rolling recovery rate of the drilling fluid were tested. The hot rolling conditions were 150℃ and the time was 16h. The test results are shown in Table 3.

[0053] Table 3 Filtration and hot rolling recovery test

[0054]

[0055] As shown in Tables 1-3, compared with Comparative Example 1, polyethyleneimine-modified cellulose is added to the drilling fluid of each embodiment, which contains a long alkyl chain, and can form a unique hydrophobic association between the molecular chains of the modified cellulose, which is beneficial to improve the viscosity and shear resistance of the cellulose-based drilling fluid. At the same time, after the cellulose is grafted with the polyethyleneimine molecular chain, a large number of carboxyl and amino groups are introduced, which improves the water solubility of the modified cellulose, and there is a good interaction between the amino groups and bentonite silicate, which can make the modified cellulose adsorbed on the surface of bentonite silicate, inhibit the hydration of its grain surface, reduce the expansion of the crystal layer, thereby reducing the expansion height, and having better anti-swelling inhibition performance. It also has the advantages of small filtration loss and high hot rolling recovery rate, showing good filtration loss reduction and high temperature resistance.

[0056] In comparative example 2, only cellulose was added, and the viscosity was low, and the hydrophilicity and water solubility were poor. After shearing, the viscosity dropped greatly, and the shear resistance was poor. In addition, the swelling height was large, the filtration loss was high, the hot rolling recovery rate was low, and the anti-swelling inhibition, filtration loss reduction, and high temperature resistance were poor.

[0057] In Comparative Example 3, 3,3',4,4'-biphenyltetracarboxylic dianhydride is used as a crosslinking agent to crosslink cellulose with polyethyleneimine. The obtained polyethyleneimine-modified cellulose does not contain long alkyl chains and cannot form hydrophobic associations, resulting in poor viscosity and shear resistance of the modified cellulose, poor filtration loss reduction, and poor high temperature resistance.

[0058] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A drilling fluid for brine-based reservoirs, characterized in that: The brine-based reservoir drilling fluid comprises 100 parts by weight of oilfield brine, 1-3 parts by weight of polyethyleneimine-modified cellulose, 1.5-2.8 parts by weight of lignin, and 1.4-2.2 parts by weight of anhydrous polymer alcohol; The preparation method of polyethyleneimine modified cellulose is as follows: cellulose and polyethyleneimine are added to N,N-dimethylformamide, a modifier and 4-dimethylaminopyridine are added after stirring, the mixture is heated to 50-70° C. and stirred for reaction for 12-18 hours, ethanol is added to the solution for dilution, the mixture is filtered, washed with ethanol, and dried to obtain polyethyleneimine modified cellulose; The structural formula of the modifier is , in the structural formula, n is 14-18.

2. The brine-based reservoir drilling fluid according to claim 1, characterized in that: The dosage of the cellulose is 100 parts by weight, the dosage of the polyethyleneimine is 15-50 parts by weight, the dosage of the modifier is 6-25 parts by weight, and the dosage of the 4-dimethylaminopyridine is 1.2-5 parts by weight.

3. The brine-based reservoir drilling fluid according to claim 1, characterized in that: The preparation method of the modifier is: Step (1), adding diethanolamine, bromoalkane and potassium carbonate to acetonitrile, concentrating under reduced pressure after the reaction, and separating the product by silica gel column chromatography, using dichloromethane and methanol solution as eluents to obtain a precursor; Step (2), in an ice-water bath, add the precursor, trimellitic anhydride chloride, and pyridine to dichloromethane, concentrate under reduced pressure after the reaction, separate the product by silica gel column chromatography, and use dichloromethane and methanol solution as eluent to obtain a modifier.

4. The brine-based reservoir drilling fluid according to claim 3, characterized in that: In the above (1), the amount of diethanolamine used is 100 parts by weight, the amount of bromoalkane used is 284-340 parts by weight, and the amount of potassium carbonate used is 136-144 parts by weight.

5. The brine-based reservoir drilling fluid according to claim 3, characterized in that: In the above (1), the bromoalkane is any one of 1-bromotetradecane, 1-bromopentadecane, 1-bromohexadecane, 1-bromoheptadecane and 1-bromooctadecane.

6. The brine-based reservoir drilling fluid according to claim 3, characterized in that: In the step (1), the reaction is stirred at room temperature for 24-36 hours.

7. The brine-based reservoir drilling fluid according to claim 3, characterized in that: In the above (2), the amount of the precursor is 100 parts by weight, the amount of trimellitic anhydride chloride is 110-140 parts by weight, and the amount of pyridine is 52-60 parts by weight.

8. The brine-based reservoir drilling fluid according to claim 3, characterized in that: In the step (2), the reaction is stirred at room temperature for 12-18 hours.

9. A method for preparing a brine-based reservoir drilling fluid as claimed in any one of claims 1 to 8, characterized in that: The preparation method comprises the following steps: adding polyethyleneimine-modified cellulose, lignin and anhydrous polyol into oilfield brine, stirring the mixture and obtaining brine-based reservoir-specific drilling fluid.

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