High-temperature-resistant xanthan gum for drilling fluid and preparation method thereof

Abstract

The invention relates to high-temperature-resistant xanthan gum for drilling fluid and a preparation method of the high-temperature-resistant xanthan gum. The method comprises the following steps: adding a transition metal salt aqueous solution into fermentation liquor for producing xanthan gum powder, uniformly stirring, heating to 60 DEG C or above, and keeping for 3 hours or above; cooling the reactant to room temperature, and adding urea and long-chain quaternary ammonium salt into the reactant; and cooling the reactant to room temperature, and processing the reactant into xanthan gum powder according to the technical specifications for xanthan gum fermentation production according to T / SDAS 54-2019, so as to obtain the high-temperature-resistant xanthan gum for the drilling fluid. After the high-temperature-resistant xanthan gum is aged, the apparent viscosity retention rate is 95% or above, and the dynamic shearing force retention rate is 98% or above.

Description

Technical Field

[0001] This invention relates to the field of modification and application technology of xanthan gum, a cutting agent for drilling fluids, and specifically to a high-temperature resistant xanthan gum for drilling fluids and its preparation method. Background Technology

[0002] Xanthan gum (XG) is a high-molecular-weight extracellular polysaccharide obtained through fermentation with Xanthomonas campestris. Due to its ability to establish high yield strength, strong shear dilution, and good sand-suspending capacity even at low concentrations, it is widely recognized as the most cost-effective natural shear lifter in water-based drilling fluids. Globally, over 80,000 tons of xanthan gum are used in drilling fluids annually, accounting for more than 65% of the total consumption of polymeric shear lifters in drilling fluids. At a conventional field addition of 0.2%–0.4%, the apparent viscosity at room temperature can reach 40–60 mPa·s, and the dynamic shear force 10–20 Pa, sufficient to meet the cutter-carrying requirements of shallow and medium-deep wells. However, as domestic oil and gas exploration shifts towards deeper, unconventional, and deep-water formations, downhole temperatures have generally risen above 120°C, and even reached 150–180°C in shale gas horizontal sections. In this high-temperature environment, the molecular structure of xanthan gum undergoes multiple deteriorations: ① thermal cracking of the β-1,4-glycosidic bonds in the main chain, resulting in a sharp drop in molecular weight; ② reversible cross-linking and dissociation of the carboxyl groups in the side chains with Ca²⁺ and Mg²⁺ in the drilling fluid, causing intermittent network nodes; ③ transformation of the double helix conformation into random coils, leading to the disintegration of the weak gel network. Experiments show that the apparent viscosity retention of 0.3% xanthan gum-based slurry after hot rolling at 100℃ for 16 h is <50%, and <30% at 120℃; the dynamic shear force drops from 20 Pa to below 5 Pa, the API filtration loss increases from 4 mL to over 10 mL, the mud cake becomes loose, and the difficulty of wellbore stability increases dramatically. Currently, methods to improve the temperature resistance limit of xanthan gum include chemical cross-linking, compounding with temperature-resistant synthetic polymers, nano-hybridization, and antioxidant additives. Chemical crosslinking can increase viscosity in the short term, but the crosslinking bonds are easily broken under high temperature and high shear, and excessive crosslinking causes a sharp increase in pump pressure. Although compounding with AMPS copolymers or hydrophobically associating polyacrylamide can push the upper limit of temperature resistance to 110-120℃, it brings high cost, large residue, and synergistic effects with xanthan gum.

[0003] Similar problems include difficulty in breaking down the gel; although the "reinforced network" such as nano-SiO2 and graphene oxide has good laboratory effects, it is difficult to disperse in the field and has poor storage stability; antioxidant additives (thiourea, sulfite) decompose themselves at high temperatures and release H2S, which negatively interferes with the corrosion inhibition and sterilization system of drilling fluid.

[0004] Therefore, a modification method is needed to improve the temperature resistance limit of xanthan gum while retaining its excellent shear dilution and environmentally friendly properties. Developing economical, efficient, and easily implementable temperature-resistant modification technologies is of significant engineering value and strategic importance for expanding the applicability of xanthan gum in deep well drilling fluids, ensuring the safe and efficient development of deep oil and gas, and reducing overall drilling costs. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, this invention modifies the fermentation broth before the production of xanthan gum powder by adding calcium and magnesium ions in the drilling fluid that can have a stronger complexing ability with the carboxyl groups of the side chains. In addition, thermally stable groups are introduced at the molecular level to construct a rigid "nano-shell" structure, which blocks the main chain breakage and conformational collapse at high temperatures, thereby improving the temperature resistance of xanthan gum in drilling fluid.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A high-temperature resistant xanthan gum for drilling fluids and its preparation method thereof, comprising the following steps:

[0008] The first step involves adding a transition metal salt aqueous solution with a mass concentration of 2-10% (1-3% of the xanthan gum powder) to the fermentation broth for producing xanthan gum powder in a reaction vessel at room temperature. The mixture is stirred until homogeneous, heated to above 60°C, and maintained for at least 3 hours. The fermentation broth for producing xanthan gum powder is the gum solution produced by fermentation according to T / SDAS 54-2019 "Technical Specification for Xanthan Gum Fermentation Production". The transition metal salt is ferric sulfate, cobalt sulfate, nickel sulfate, copper sulfate, zinc sulfate, ferric nitrate, cobalt nitrate, nickel nitrate, copper nitrate, zinc nitrate, ferric chloride, cobalt chloride, nickel chloride, copper chloride, and zinc chloride with industrial grade or higher purity.

[0009] The second step involves cooling the above reactants to room temperature, adding 0.1-0.3% of a long-chain quaternary ammonium salt and 0.05-0.1% of urea (by mass of the fermentation broth), stirring until homogeneous, and heating to above 60°C for at least 3 hours. The long-chain quaternary ammonium salt is industrial grade or higher purity, comprising: dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, octadecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium bromide, dodecyl dimethylbenzylammonium chloride, hexadecyl dimethylbenzylammonium chloride, octadecyl dimethylbenzylammonium chloride, dodecyl dimethylbenzylammonium bromide, hexadecyl dimethylbenzylammonium bromide, and octadecyl dimethylbenzylammonium bromide. The urea is industrial grade or higher purity.

[0010] The third step is to cool the above reactants to room temperature and process them into xanthan gum powder in accordance with T / SDAS 54-2019 "Technical Specification for Fermentation Production of Xanthan Gum", thus obtaining high-temperature resistant xanthan gum for drilling fluid.

[0011] This invention introduces transition metal ions that can strongly complex with carboxyl groups, maintaining their water solubility while inhibiting complexation with calcium and magnesium ions in drilling fluid. The introduced long-chain quaternary ammonium salt can enter the inner cavity of the less polar xanthan gum double helix structure, improving its double helix structure stability. Urea can react with highly reactive amine groups to convert into formamide, thereby inhibiting the reaction of amine groups with other active compounds during high-temperature aging in drilling fluid. The synergistic effect of these three methods enhances the temperature resistance in drilling fluid.

[0012] The beneficial effects of this invention are as follows:

[0013] Unmodified xanthan gum retains less than 50% of its apparent viscosity and less than 60% of its dynamic shear force after aging in drilling fluid at 90℃-110℃ for more than 8 hours. In contrast, high-temperature resistant xanthan gum retains more than 80% of its apparent viscosity and more than 75% of its dynamic shear force after aging for more than 80% of its apparent viscosity. Example

[0014] The present invention will be further illustrated below through examples. It should be understood that the methods described in the examples are merely illustrative and not intended to limit the invention. Simple modifications to the preparation methods of the present invention within the framework of the present invention's concept are all within the scope of protection claimed by the present invention. All raw materials and solvents used in the examples are commercially available products of the corresponding purity.

[0015] The present invention will be further described below with reference to embodiments.

[0016] Example 1

[0017] A high-temperature resistant xanthan gum for drilling fluids and its preparation method thereof, comprising the following steps:

[0018] The first step involves adding a 2% (3% by weight) aqueous solution of a transition metal salt to the fermentation broth for producing xanthan gum powder in a reactor at room temperature. The mixture is stirred until homogeneous, heated to 70°C, and maintained for 4 hours. The fermentation broth for producing xanthan gum powder is the gum solution produced by fermentation according to T / SDAS 54-2019 "Technical Specification for Fermentation Production of Xanthan Gum". The transition metal salt is industrial-grade ferric sulfate.

[0019] The second step involves cooling the above reactants to room temperature, adding 0.3% of a long-chain quaternary ammonium salt and 0.05% of urea (by mass of the fermentation broth), stirring until homogeneous, heating to 70°C, and maintaining the temperature for 6 hours. The long-chain quaternary ammonium salt is industrial-grade octadecyltrimethylammonium bromide, and the urea is an industrial-grade product.

[0020] The third step is to cool the above reactants to room temperature and process them into xanthan gum powder in accordance with T / SDAS 54-2019 "Technical Specification for Fermentation Production of Xanthan Gum", thus obtaining high-temperature resistant xanthan gum for drilling fluid.

[0021] The beneficial effects of this invention are as follows:

[0022] After aging in drilling fluid at 95°C for 10 hours, 0.5% unmodified xanthan gum retained 45% of its apparent viscosity and 55% of its dynamic shear strength; in contrast, high-temperature resistant xanthan gum retained 95% of its apparent viscosity and 98% of its dynamic shear strength after aging.

[0023] Example 2

[0024] A high-temperature resistant xanthan gum for drilling fluids and its preparation method thereof, comprising the following steps:

[0025] The first step involves adding a 2% (3% by weight) aqueous solution of a transition metal salt to the fermentation broth for producing xanthan gum powder in a reactor at room temperature. The mixture is stirred until homogeneous, heated to 70°C, and maintained for 4 hours. The fermentation broth for producing xanthan gum powder is the gum solution produced by fermentation according to T / SDAS 54-2019 "Technical Specification for Fermentation Production of Xanthan Gum". The transition metal salt is industrial-grade ferric sulfate.

[0026] The second step involves cooling the above reactants to room temperature, adding 0.3% of a long-chain quaternary ammonium salt and 0.05% of urea (by mass of the fermentation broth), stirring until homogeneous, heating to 70°C, and maintaining the temperature for 6 hours. The long-chain quaternary ammonium salt is industrial-grade octadecyltrimethylammonium bromide, and the urea is an industrial-grade product.

[0027] The third step is to cool the above reactants to room temperature and process them into xanthan gum powder in accordance with T / SDAS 54-2019 "Technical Specification for Fermentation Production of Xanthan Gum", thus obtaining high-temperature resistant xanthan gum for drilling fluid.

[0028] The beneficial effects of this invention are as follows:

[0029] After aging in drilling fluid at 100°C for 16 hours, 0.4% unmodified xanthan gum retained 40% of its apparent viscosity and 50% of its dynamic shear strength; in contrast, 0.4% high-temperature resistant xanthan gum retained 90% of its apparent viscosity and 85% of its dynamic shear strength after aging.

[0030] Example 3

[0031] A high-temperature resistant xanthan gum for drilling fluids and its preparation method thereof, comprising the following steps:

[0032] The first step involves adding a 2% (3% by weight) aqueous solution of a transition metal salt to the fermentation broth for producing xanthan gum powder in a reactor at room temperature. The mixture is stirred until homogeneous, heated to 70°C, and maintained for 4 hours. The fermentation broth for producing xanthan gum powder is the gum solution produced by fermentation according to T / SDAS 54-2019 "Technical Specification for Fermentation Production of Xanthan Gum". The transition metal salt is industrial-grade ferric sulfate.

[0033] The second step involves cooling the above reactants to room temperature, adding 0.3% of a long-chain quaternary ammonium salt and 0.05% of urea (by mass of the fermentation broth), stirring until homogeneous, heating to 70°C, and maintaining the temperature for 6 hours. The long-chain quaternary ammonium salt is industrial-grade octadecyltrimethylammonium bromide, and the urea is an industrial-grade product.

[0034] The third step is to cool the above reactants to room temperature and process them into xanthan gum powder in accordance with T / SDAS 54-2019 "Technical Specification for Fermentation Production of Xanthan Gum", thus obtaining high-temperature resistant xanthan gum for drilling fluid.

[0035] The beneficial effects of this invention are as follows:

[0036] The apparent viscosity retention rate of 1% unmodified xanthan gum after aging at 105°C for 16 hours in drilling fluid was 42%, and the dynamic shear force retention rate was 33%. In contrast, the apparent viscosity retention rate of high-temperature resistant xanthan gum after aging was 81%, and the dynamic shear force retention rate was 83%.

[0037] Example 4

[0038] A high-temperature resistant xanthan gum for drilling fluids and its preparation method thereof, comprising the following steps:

[0039] The first step involves adding a 2% (3% by weight) aqueous solution of a transition metal salt to the fermentation broth for producing xanthan gum powder in a reactor at room temperature. The mixture is stirred until homogeneous, heated to 70°C, and maintained for 4 hours. The fermentation broth for producing xanthan gum powder is the gum solution produced by fermentation according to T / SDAS 54-2019 "Technical Specification for Fermentation Production of Xanthan Gum". The transition metal salt is industrial-grade ferric sulfate.

[0040] The second step involves cooling the above reactants to room temperature, adding 0.3% of a long-chain quaternary ammonium salt and 0.05% of urea (by mass of the fermentation broth), stirring until homogeneous, heating to 70°C, and maintaining the temperature for 6 hours. The long-chain quaternary ammonium salt is industrial-grade octadecyltrimethylammonium bromide, and the urea is an industrial-grade product.

[0041] The third step is to cool the above reactants to room temperature and process them into xanthan gum powder in accordance with T / SDAS 54-2019 "Technical Specification for Fermentation Production of Xanthan Gum", thus obtaining high-temperature resistant xanthan gum for drilling fluid.

[0042] The beneficial effects of this invention are as follows:

[0043] After aging in drilling fluid at 110°C for 12 hours, 0.6% unmodified xanthan gum retained 33% of its apparent viscosity and 40% of its dynamic shear strength; in contrast, high-temperature resistant xanthan gum retained 81% of its apparent viscosity and 76% of its dynamic shear strength after aging.

[0044] Example 5

[0045] A high-temperature resistant xanthan gum for drilling fluids and its preparation method thereof, comprising the following steps:

[0046] The first step involves adding a 2% (3% by weight) aqueous solution of a transition metal salt to the fermentation broth for producing xanthan gum powder in a reactor at room temperature. The mixture is stirred until homogeneous, heated to 70°C, and maintained for 4 hours. The fermentation broth for producing xanthan gum powder is the gum solution produced by fermentation according to T / SDAS 54-2019 "Technical Specification for Fermentation Production of Xanthan Gum". The transition metal salt is industrial-grade ferric sulfate.

[0047] The second step involves cooling the above reactants to room temperature, adding 0.3% of a long-chain quaternary ammonium salt and 0.05% of urea (by mass of the fermentation broth), stirring until homogeneous, heating to 70°C, and maintaining the temperature for 6 hours. The long-chain quaternary ammonium salt is industrial-grade octadecyltrimethylammonium bromide, and the urea is an industrial-grade product.

[0048] The third step is to cool the above reactants to room temperature and process them into xanthan gum powder in accordance with T / SDAS 54-2019 "Technical Specification for Fermentation Production of Xanthan Gum", thus obtaining high-temperature resistant xanthan gum for drilling fluid.

[0049] The beneficial effects of this invention are as follows:

[0050] After aging in drilling fluid at 105°C for 24 hours, 0.5% unmodified xanthan gum retained 40% of its apparent viscosity and 30% of its dynamic shear strength; in contrast, high-temperature resistant xanthan gum retained 82% of its apparent viscosity and 80% of its dynamic shear strength after aging.

[0051] Example 6

[0052] A high-temperature resistant xanthan gum for drilling fluids and its preparation method thereof, comprising the following steps:

[0053] The first step involves adding a 2% (3% by weight) aqueous solution of a transition metal salt to the fermentation broth for producing xanthan gum powder in a reactor at room temperature. The mixture is stirred until homogeneous, heated to 70°C, and maintained for 4 hours. The fermentation broth for producing xanthan gum powder is the gum solution produced by fermentation according to T / SDAS 54-2019 "Technical Specification for Fermentation Production of Xanthan Gum". The transition metal salt is industrial-grade ferric sulfate.

[0054] The second step involves cooling the above reactants to room temperature, adding 0.3% of a long-chain quaternary ammonium salt and 0.05% of urea (by mass of the fermentation broth), stirring until homogeneous, heating to 70°C, and maintaining the temperature for 6 hours. The long-chain quaternary ammonium salt is industrial-grade octadecyltrimethylammonium bromide, and the urea is an industrial-grade product.

[0055] The third step is to cool the above reactants to room temperature and process them into xanthan gum powder in accordance with T / SDAS 54-2019 "Technical Specification for Fermentation Production of Xanthan Gum", thus obtaining high-temperature resistant xanthan gum for drilling fluid.

[0056] The beneficial effects of this invention are as follows:

[0057] After aging in drilling fluid at 100°C for 18 hours, 0.4% unmodified xanthan gum retained 45% of its apparent viscosity and 48% of its dynamic shear strength; in contrast, high-temperature resistant xanthan gum retained 87% of its apparent viscosity and 85% of its dynamic shear strength after aging.

Claims

1. A high-temperature resistant xanthan gum for drilling fluid, characterized in that... include: Fermentation broth of xanthan gum powder, transition metal salts, long-chain quaternary ammonium salts, and urea.

2. The high-temperature resistant xanthan gum for drilling fluid according to claim 1, characterized in that: The fermentation broth used to produce xanthan gum powder is a gum solution produced by fermentation according to T / SDAS 54-2019 "Technical Specification for Fermentation Production of Xanthan Gum". The transition metal salts are ferric sulfate, cobalt sulfate, nickel sulfate, copper sulfate, zinc sulfate, ferric nitrate, cobalt nitrate, nickel nitrate, copper nitrate, zinc nitrate, ferric chloride, cobalt chloride, nickel chloride, copper chloride, and zinc chloride. The long-chain quaternary ammonium salts are dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, octadecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium bromide, dodecyl dimethylbenzylammonium chloride, hexadecyl dimethylbenzylammonium chloride, octadecyl dimethylbenzylammonium chloride, dodecyl dimethylbenzylammonium bromide, hexadecyl dimethylbenzylammonium bromide, and octadecyl dimethylbenzylammonium bromide. The urea is a product of industrial grade or higher purity.

3. The method for preparing high-temperature resistant xanthan gum for drilling fluid according to claim 1 or 2, characterized in that... Includes the following steps: The first step involves adding a transition metal salt aqueous solution with a mass concentration of 2-10% (1-3% of the xanthan gum powder) to the fermentation broth for producing xanthan gum powder in a reaction vessel at room temperature. The mixture is stirred until homogeneous, heated to above 60°C, and maintained for at least 3 hours. The fermentation broth for producing xanthan gum powder is the gum solution produced by fermentation according to T / SDAS 54-2019 "Technical Specification for Xanthan Gum Fermentation Production". The transition metal salt is ferric sulfate, cobalt sulfate, nickel sulfate, copper sulfate, zinc sulfate, ferric nitrate, cobalt nitrate, nickel nitrate, copper nitrate, zinc nitrate, ferric chloride, cobalt chloride, nickel chloride, copper chloride, and zinc chloride with industrial grade or higher purity.

4. The method for preparing high-temperature resistant xanthan gum for drilling fluid according to claim 3, characterized in that... Includes the following steps: The second step involves cooling the above reactants to room temperature, adding 0.1-0.3% of a long-chain quaternary ammonium salt and 0.05-0.1% of urea (by mass of the fermentation broth), stirring until homogeneous, and heating to above 60°C for at least 3 hours. The long-chain quaternary ammonium salt is industrial grade or higher purity, comprising: dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, octadecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium bromide, dodecyl dimethylbenzylammonium chloride, hexadecyl dimethylbenzylammonium chloride, octadecyl dimethylbenzylammonium chloride, dodecyl dimethylbenzylammonium bromide, hexadecyl dimethylbenzylammonium bromide, and octadecyl dimethylbenzylammonium bromide. The urea is industrial grade or higher purity.

5. The method for preparing high-temperature resistant xanthan gum for drilling fluid according to claim 3, characterized in that... Includes the following steps: The third step is to cool the above reactants to room temperature and process them into xanthan gum powder in accordance with T / SDAS 54-2019 "Technical Specification for Fermentation Production of Xanthan Gum", thus obtaining high-temperature resistant xanthan gum for drilling fluid.

6. The method for preparing high-temperature resistant xanthan gum for drilling fluid according to claim 3, characterized in that... Includes the following steps: The first step involves adding a transition metal salt aqueous solution with a mass concentration of 2-10% (1-3% of the xanthan gum powder) to the fermentation broth for producing xanthan gum powder in a reaction vessel at room temperature. The mixture is stirred until homogeneous, heated to above 60°C, and maintained for at least 3 hours. The fermentation broth for producing xanthan gum powder is the gum solution produced by fermentation according to T / SDAS 54-2019 "Technical Specification for Xanthan Gum Fermentation Production". The transition metal salt is ferric sulfate, cobalt sulfate, nickel sulfate, copper sulfate, zinc sulfate, ferric nitrate, cobalt nitrate, nickel nitrate, copper nitrate, zinc nitrate, ferric chloride, cobalt chloride, nickel chloride, copper chloride, and zinc chloride with industrial grade or higher purity. The second step involves cooling the above reactants to room temperature, adding 0.1-0.3% of a long-chain quaternary ammonium salt and 0.05-0.1% of urea (by mass of the fermentation broth), stirring until homogeneous, and heating to above 60°C for at least 3 hours. The long-chain quaternary ammonium salt is industrial grade or higher purity, comprising: dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, octadecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium bromide, dodecyl dimethylbenzylammonium chloride, hexadecyl dimethylbenzylammonium chloride, octadecyl dimethylbenzylammonium chloride, dodecyl dimethylbenzylammonium bromide, hexadecyl dimethylbenzylammonium bromide, and octadecyl dimethylbenzylammonium bromide. The urea is industrial grade or higher purity. The third step is to cool the above reactants to room temperature and process them into xanthan gum powder in accordance with T / SDAS 54-2019 "Technical Specification for Fermentation Production of Xanthan Gum", thus obtaining high-temperature resistant xanthan gum for drilling fluid.

7. Use of the high-temperature resistant xanthan gum for drilling fluids according to claim 1 or 2 in the petroleum industry.