High paraffin oil-based drilling fluid base oil and method of making

Abstract

The application discloses a high-paraffin oil-based drilling fluid base oil and a preparation method thereof. The preparation method comprises the following steps: after mineral base distillate oil and hydrogen are mixed, the mixture is introduced into a first reaction zone and a second reaction zone provided with catalysts to perform reaction, and the reaction product flowing out of the second reaction zone is subjected to high-pressure separation, stripping and fractionation to obtain the high-paraffin oil-based drilling fluid base oil. The high-paraffin oil-based drilling fluid base oil developed by the application has ultra-low aromatic hydrocarbon content, ultra-high paraffin content, and lower biological toxicity and higher degradability.

Description

Technical Field

[0001] This invention belongs to the field of petroleum refining and relates to a base oil product for high-chain alkane oil-based drilling fluid and its preparation method. Background Technology

[0002] With the increasing number of unconventional oil and gas wells and the growing complexity of geological conditions, the application range of oil-based drilling fluids is expanding. Oil-based drilling fluids mainly consist of base fluid, emulsifiers, filtration reducers, and organic clay, with base fluid accounting for approximately 70% of the cost. The average consumption of base fluid per well in shale gas horizontal wells is nearly 300 cubic meters; in deep wells in the Kuqa foreland / Junggar Basin of the Tarim Basin, the average consumption is 880 cubic meters; and the group company's annual consumption of base fluid is 200,000 cubic meters, with costs exceeding 1.6 billion yuan.

[0003] Currently, the main base fluids for oil-based drilling fluids in China are diesel-based, white oil-based, and a small amount of synthetic-based base fluids. Internationally, the mainstream approach uses low-toxicity or non-toxic, biodegradable oil-based or synthetic-based base fluids, such as Total's EDC95-11 base oil, which has an aromatic hydrocarbon content of less than 0.03%, a sulfur content of less than 1 mg / kg, a nitrogen content of less than 2 mg / kg, a flash point of 115℃, and a kinematic viscosity of 3.5 mm. 2 / s, with a 74% biodegradability rate in seawater within 28 days. Shell's Saraline 185V has an aromatic hydrocarbon content of less than 0.05%, a sulfur content of less than 3 mg / kg, a flash point of 85℃, and a kinematic viscosity of 2.6 mm. 2 / s, the biodegradation rate in seawater within 28 days is 60%.

[0004] Synthetic-based drilling fluid systems are a new type of environmentally friendly drilling fluid system. They possess the characteristics of oil-based drilling fluids, such as high-temperature resistance, resistance to salt and calcium intrusion, improved wellbore stability, good lubrication, and minimal damage to oil and gas reservoirs. Furthermore, they offer at least the following advantages: 1) Enhancing the technological level of oil and gas resource exploration and development in ecologically sensitive or environmentally fragile areas, thereby improving global competitiveness; 2) Increasing mechanical drilling speed and reducing drilling cycle time; 3) Reducing annular pressure loss, improving ECD control levels, and mitigating downhole complexity and induced leakage risks; 4) Increasing drilling fluid reuse rate and reducing overall costs. Based on these reasons and advantages, developing drilling fluid base oils with similar properties to synthetic-based systems is the development trend of oil-based drilling fluid base oils.

[0005] CN105713661B discloses a method for preparing synthetic-based drilling fluid base oil, comprising the following steps: 1) distilling a specific fraction of Fischer-Tropsch synthesis into several fractions; 2) isomerizing one or more of the obtained fractions, controlling the isomerization degree between 50% and 100% by changing the reaction conditions; 3) blending the isomerized and un-isomerized fractions in a certain proportion according to the application requirements of the drilling fluid; 4) distilling the blended product to remove the low-carbon hydrocarbons, a byproduct of hydroisomerization, to obtain a base oil sample for performance testing and commercial application. This method mainly uses Fischer-Tropsch synthesis fractions as raw materials to achieve the production of synthetic-based base oil for drilling fluids through hydroisomerization, blending, and other processes.

[0006] CN110964564A discloses a Fischer-Tropsch synthetic-based drilling fluid base oil and its preparation method. The preparation method includes: cracking and isomerizing the Fischer-Tropsch synthetic product; directly fractionating the cracked and isomerized Fischer-Tropsch synthetic product to obtain the base oil product, or hydrorefining the product followed by fractionation to obtain the base oil product; wherein the fractionation includes atmospheric fractionation, and the process conditions for atmospheric fractionation are: top temperature 100-120℃, top pressure 0.01-0.2MPa, and side stream extraction temperature 170-190℃. This method requires Fischer-Tropsch products as raw materials, and requires cracking, isomerization, and subsequent supplementary refining to produce suitable drilling fluid base oil.

[0007] CN113136181B discloses a biosynthetic-based drilling fluid and its preparation method. The raw materials for the biosynthetic-based drilling fluid include: biodiesel, calcium chloride solution, organic clay, a primary emulsifier, a secondary emulsifier, a filtration reducer, a wetting agent, lime, a flow pattern regulator, and barite powder. By weight, the biodiesel comprises 80-90 parts, and the calcium chloride solution comprises 20-10 parts. The primary emulsifier is polyamide HYOZ, the secondary emulsifier is amide-based amine HYOF, and the flow pattern regulator is polyamide HYON. This biosynthetic-based drilling fluid overcomes the serious environmental pollution problems caused by conventional oil-based drilling fluids, such as the difficulty in degrading oil-based cuttings and waste oil-based drilling fluids, their high biotoxicity, and the presence of aromatic hydrocarbons. It relies on biodiesel as a raw material, ensuring that the raw material contains a large amount of isoparaffins. Meanwhile, Jie Yuning et al. (Petroleum Drilling Technology, 2019, 47, 34-39) also revealed that waste cooking oils such as animal and vegetable oils and microbial oils can be used as raw materials for biosynthetic base oils, and the 96-hour half-lethal concentration (LC50) of the synthetic base oil for drilling fluids is >1,000,000 mg / L.

[0008] CN110698329A discloses a method for preparing biomass synthetic oil for drilling fluids, comprising: reacting halododecane, an acid-binding agent, and an alkyl alcohol under the action of a catalyst to obtain biomass synthetic oil for drilling fluids. This technology provides a method for preparing biomass synthetic oil for drilling fluids at a low synthesis temperature. This biomass synthetic oil dodecyl ether exhibits good inhibition properties, low viscosity, strong temperature resistance, hydrolytic stability, and biodegradability, making it suitable as a base oil for synthetic drilling fluids. However, in acidic or alkaline formation environments, although the biomass synthetic oil can degrade, it cannot maintain its stability, affecting the safety performance during drilling operations.

[0009] In summary, to obtain low-toxicity oil-based drilling fluid base oils, the main characteristics are high alkane content and low aromatic content. In the product field, the main products are Fischer-Tropsch-oriented synthetic-based drilling fluid base oils, polyalphaolefins (LAO), linear paraffins, internal olefins, biomass-synthesized drilling fluid base oils, and ether- or bio-ester-based synthetic-based drilling fluid base oils. However, the above-mentioned unit processes or products are relatively difficult to synthesize or have high synthesis costs in the industry, which greatly limits the promotion of low-toxicity, high-alkane drilling fluid base oils. Traditional mineral-based drilling fluid base oils generally have an alkane content of 20-60 wt%, which cannot meet the demand for high alkane content. Furthermore, even with molecular sieve dewaxing and solvent dewaxing processes, it is still necessary to combine them with unit processes such as hydroisomerization to achieve the conversion of wax to oil, making the process route relatively complex. Summary of the Invention

[0010] The technical problem to be solved by this invention is to increase the alkane content of traditional white oil-based or diesel-based mineral-based drilling fluid base oils, reduce their biotoxicity during use, and improve their degradation efficiency.

[0011] To address the limitations of raw materials and processes in the traditional production of synthetic-based drilling fluid base oils, and to improve the application and promotion of drilling fluid base oils with high alkane content, enhance their biodegradability, and reduce their biotoxicity, this invention, combining the reaction characteristics of hydrocarbon conversion with the compositional requirements of hydrocarbon molecules for biotoxicity and biodegradability, provides a process for producing high-alkane, low-aromatic drilling fluid base oils from mineral oil. This effectively broadens the product sources of synthetic-based drilling fluid base oils and significantly reduces their production costs.

[0012] To achieve the above objectives, a method for preparing a base oil for high-alkane oil-based drilling fluid is provided, wherein the base oil has an alkane content of ≥90 wt% and an aromatic content of ≤0.2 wt%. The preparation method includes the following steps:

[0013] a) After mixing mineral-based distillate oil and hydrogen, the mixture enters the first reaction zone containing a catalyst for reaction;

[0014] b) The reaction products flowing out of the first reaction zone continue to enter the second reaction zone containing the catalyst for further reaction;

[0015] c) The reaction products flowing out of the second reaction zone are subjected to high-pressure separation, stripping, and fractionation to obtain unconverted bottom oil, which is the base oil for high-chain alkane oil-based drilling fluid.

[0016] The present invention relates to a method for preparing base oil for high-chain alkane oil-based drilling fluids, wherein the mineral-based distillate oil is mainly straight-run diesel oil with a distillation range of 180-370℃, preferably 180-330℃.

[0017] In the method for preparing base oil for high-chain alkane oil-based drilling fluid of the present invention, when the catalyst in the first reaction zone is a hydrorefining catalyst, the catalyst in the second reaction zone is a hydrocracking catalyst.

[0018] In the method for preparing base oil for high-chain alkane oil-based drilling fluid of the present invention, when the catalyst in the first reaction zone is a hydrocracking catalyst, the catalyst in the second reaction zone is a hydrorefining catalyst.

[0019] Based on the selected mineral oil distillation range of 180-330℃, the reactor gradation can be optimized according to the flow direction of the reactants. The reaction direction can be hydrorefining and hydrocracking, or the reaction direction can be to first contact the hydrocracking catalyst and then contact the hydrorefining catalyst. Both methods can achieve the production of drilling fluid base oil with high alkane content from conventional mineral oil.

[0020] This invention does not particularly limit the hydrorefining catalyst. The hydrorefining catalyst includes, but is not limited to, a hydrorefining catalyst containing at least one of Ni, W, Co, and Mo as a transition metal active phase, and simultaneously containing one or two non-metallic dopants of Si, P, B, and F. Its support can be at least one of γ-Al2O3 and amorphous silicon-aluminum, or a complexing agent, wherein the complexing agent is at least one of citric acid, oxalic acid, and ethylenediamine. Commercially available or commercially available hydrorefining catalysts, such as PHD, PHF, FHUDS, RS, and HYT, can also be used to meet the requirements of desulfurization and denitrification or aromatic saturation.

[0021] This invention does not particularly limit the hydrocracking catalyst, which includes, but is not limited to, a bifunctional catalyst with cracking function, wherein the active hydrogenation component is an oxide of one, two or three of the metals Ni, W, Co and Mo, and the acid support contains at least one of zeolite, amorphous silica-alumina and alumina. Commercially available or commercially available medium-oil type or flexible hydrocracking catalysts are also used to meet the performance requirements of low naphtha yield under high temperature conditions, and at the same time, the hydrocracking catalyst is required to preferentially convert aromatics or cycloalkanes.

[0022] The method for preparing base oil for high-chain alkane oil-based drilling fluid of the present invention includes a pressure of 6-20 MPa, preferably 6-12 MPa, a reaction temperature of 330-370°C, and a space velocity of 0.5-3.0 h⁻¹. -1 The hydrogen-to-oil ratio is 600-1500 v / v.

[0023] The method for preparing base oil for high-chain alkane oil-based drilling fluid of the present invention includes a second reaction zone with pressure consistent with the first reaction zone, a reaction temperature of 340-380℃, and a space velocity of 0.5-3.0 h⁻¹. -1 The hydrogen-to-oil ratio is 600-1500 v / v.

[0024] The method for preparing base oil for high-chain alkane oil-based drilling fluid of the present invention specifies that the initial boiling point of the unconverted bottom oil is not lower than 200°C, and the viscosity of the unconverted bottom oil at 40°C is in the range of 2.2-3.0 mm. 2 / s.

[0025] The present invention also provides a base oil for drilling fluid with high alkane content ≥90wt%, aromatic content ≤0.2wt%, and flash point ≥80℃.

[0026] The high-chain alkane oil-based drilling fluid base oil of the present invention, wherein the EC of the high-chain alkane oil-based drilling fluid base oil is... 50 ≥40000mg / L.

[0027] The yield of unconverted oil at the bottom of the distillation column is closely related to the reaction depth and the alkanes content of the feedstock. Generally, the product of the yield of unconverted oil at the bottom of the column and the alkanes content at the bottom is lower than the alkanes content of the feedstock. Based on this relationship, by controlling an appropriate conversion depth, the enrichment of high alkanes content at the bottom of the column can be achieved. The preparation of drilling fluid base oil with high alkanes content in this invention is closely related to the conversion efficiency of mineral oil. Considering product distribution and economics, a single-pass or partial tail oil recycling mode can be used to achieve the enrichment of high alkanes content in the unconverted oil. The single-pass mode may generate more light components or gases; therefore, a partial recycling mode can be used to achieve the enrichment of alkanes in the unconverted oil.

[0028] Compared to synthetic-based, bio-based, and ether / ester-based drilling fluid base oils, the high-alkane oil-based drilling fluid base oil developed in this invention exhibits ultra-low aromatics and ultra-high alkane content, along with lower biotoxicity, higher biodegradability, and excellent drilling fluid compatibility. Based on the understanding of hydrocarbon molecule transformation, this invention utilizes a dual-reaction functional zone catalysis approach, employing a graded approach of hydrorefining and hydrocracking catalysts to preferentially convert cycloalkanes and aromatics, maximizing the retention of alkane content. Simultaneously, based on conversion efficiency and product carbon number characterization, combined with distillation and reaction cycle modes, it achieves alkane enrichment, cycloalkane conversion, and aromatics hydrogenation saturation and secondary conversion, resulting in alkane enrichment in the unconverted bottom oil. The total alkane content is >90 wt%, and the aromatic content is <0.2 wt%. This effectively expands the sources of high-alkane drilling fluid base oils and reduces dependence on synthetic-based, bio-based, and ether / ester-based base oils. This invention can also avoid secondary processing and reduce costs. Attached Figure Description

[0029] Figure 1 This is a carbon number distribution diagram of the base oil for high-chain alkane content mineral-based drilling fluid in Example 1. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to specific embodiments, but the present invention is not limited to the following embodiments. Any modifications that do not depart from the concept and scope of the present invention are within the scope of the present invention.

[0031] The properties of the straight-run diesel used in the examples and comparative examples are shown in Table 1.

[0032] Table 1 Basic Information on Straight-Run Diesel Feedstock

[0033]

[0034]

[0035] Example 1:

[0036] Preparation of base oil for high-chain alkane oil-based drilling fluid: Straight-run diesel I is mixed with hydrogen and then contacted with catalysts in the first and second reaction zones. The system reaction pressure is 6 MPa, the hydrogen-to-oil ratio (v / v) is 1000, and the mass hourly space velocity (HHSV) in the first reaction zone is 1.5 h⁻¹. -1 The mass hourly space velocity (HHSV) in the second reaction zone is 1.5 h⁻¹. -1The catalyst in the first reaction zone is hydrorefined Ni-Mo-P / Al2O3, and the catalyst in the second reaction zone is hydrocracking Ni-W / USY-SiO2-Al2O3-Al2O3 catalyst. The reaction temperature in the first reaction zone is 350℃, and the reaction temperature in the second reaction zone is 365℃. The product from the second reaction zone is subjected to high-pressure separation, a stripping tower, and a fractionation tower. The bottom cutting temperature of the fractionation tower is controlled at 235℃. The product obtained from the bottom of the fractionation tower is a high-chain alkane oil-based drilling fluid base oil. Analysis using ASTM D86 standard shows that the fraction's temperature range is 235–285℃. Analysis using ASTM D 445 method shows a kinematic viscosity of 2.7 mmHg at 40℃. 2 / s. Analysis using SH / T0606 yielded an alkane content of 92 wt%, an aromatic content of <0.1 wt%, and a flash point of 90℃. The relative alkane content distribution is as follows: Figure 1 As shown.

[0037] The test was conducted according to the methods specified in Q / SY 111-2007 "Classification and Detection Methods for Biotoxicity of Oilfield Chemicals and Drilling Fluids", EC 50 =40000mg / L.

[0038] Comparative Example 1:

[0039] Preparation of base oil for conventional mineral-based oil-based drilling fluids: The difference from Example 1 is that only the first reaction zone is used, and the second reaction zone is not used.

[0040] Straight-run diesel I is mixed with hydrogen and then contacted with the catalyst in the first reaction zone. The system reaction pressure is 6 MPa, the hydrogen-to-oil ratio (v / v) is 1000, and the mass hourly space velocity (HHSV) in the first reaction zone is 1.5 h⁻¹. -1 The catalyst in the first reaction zone is hydrorefined Ni-Mo-P / Al2O3, and the reaction temperature in the first reaction zone is 350℃. The product from the first reaction zone is subjected to high-pressure separation, a stripping tower, and a fractionation tower. The product obtained from the bottom of the fractionation tower is a conventional mineral-based drilling fluid base oil. Analysis using ASTM D86 standard shows that the fraction's temperature range is 200-310℃, and the kinematic viscosity at 40℃ is 2.85 mmHg, analyzed using ASTM D445 method. 2 The content of alkane was 48 wt%, the total amount of aromatics was 8.1 wt%, and the flash point was 75℃, obtained by SH / T0606 analysis method.

[0041] The test was conducted according to the methods specified in Q / SY 111-2007 "Classification and Detection Methods for Biotoxicity of Oilfield Chemicals and Drilling Fluids", EC 50 =8000mg / L.

[0042] Example 2:

[0043] Preparation of base oil for high-chain alkane oil-based drilling fluid: Straight-run diesel II is mixed with hydrogen and then contacted with catalysts in the first and second reaction zones. The system reaction pressure is 6 MPa, the hydrogen-to-oil ratio (v / v) is 1200, and the mass hourly space velocity (HHSV) in the first reaction zone is 1.5 h⁻¹. -1 The mass hourly space velocity (HHSV) in the second reaction zone is 1.3 h⁻¹. -1 The catalyst in the first reaction zone is hydrorefined Ni-Mo-P / Al2O3, and the catalyst in the second reaction zone is hydrocracking Ni-W / USY-SiO2-Al2O3-Al2O3 catalyst. The reaction temperature in the first reaction zone is 360℃, and the reaction temperature in the second reaction zone is 375℃. The product from the second reaction zone is subjected to high-pressure separation, stripping, and fractionation. The product obtained from the bottom of the fractionation tower is a high-chain alkane oil-based drilling fluid base oil. Analysis using ASTM D86 standard shows that the fraction's temperature range is 235–330℃. Analysis using ASTM D445 method shows a kinematic viscosity of 2.95 mmHg at 40℃. 2 / s. Analysis using SH / T0606 showed that the alkane content was 94wt%, the aromatic content was <0.2wt%, and the flash point was 95℃.

[0044] The test was conducted according to the methods specified in Q / SY 111-2007 "Classification and Detection Methods for Biotoxicity of Oilfield Chemicals and Drilling Fluids", EC 50 =42000mg / L.

[0045] Example 3:

[0046] Preparation of base oil for high-chain alkane oil-based drilling fluid: Straight-run diesel I is mixed with hydrogen and then contacted with catalysts in the first and second reaction zones. The system reaction pressure is 12 MPa, the hydrogen-to-oil ratio (v / v) is 1000, and the mass hourly space velocity (HHSV) in the first reaction zone is 1.5 h⁻¹. -1 The mass hourly space velocity (HHSV) in the second reaction zone is 1.5 h⁻¹. -1 The catalyst in the first reaction zone is a hydrocracking Ni-W / USY-SiO2-Al2O3-Al2O3 catalyst, and the catalyst in the second reaction zone is a hydrorefining Ni-Mo-P / Al2O3 catalyst. The reaction temperature in both zones is 370℃. The product from the second reaction zone is then subjected to high-pressure separation, a stripping tower, and a fractionation tower. The product obtained from the bottom of the fractionation tower is a high-chain alkane oil-based drilling fluid base oil. Analysis using ASTM D86 standard shows that the fraction's temperature range is 235–285℃. Analysis using ASTM D445 method shows a kinematic viscosity of 2.68 mmHg at 40℃. 2 / s. SH / T0606 analysis revealed an alkane content of 95 wt%, an aromatic content of <0.05 wt%, and a flash point of 100℃.

[0047] The test was conducted according to the methods specified in Q / SY 111-2007 "Classification and Detection Methods for Biotoxicity of Oilfield Chemicals and Drilling Fluids", EC 50 =43500mg / L.

[0048] Comparative Example 2:

[0049] Preparation of base oil for low-chain alkane oil-based drilling fluid: Straight-run diesel I is mixed with hydrogen and then contacted with catalysts in the first and second reaction zones. The system reaction pressure is 6 MPa, the hydrogen-to-oil ratio (v / v) is 1000, and the mass hourly space velocity (HHSV) in the first reaction zone is 1.5 h⁻¹. -1 The mass hourly space velocity (HHSV) in the second reaction zone is 1.5 h⁻¹. -1 The catalyst in the first reaction zone is hydrorefined Ni-Mo-P / Al2O3, and the catalyst in the second reaction zone is hydrocracking Ni-W / USY-SiO2-Al2O3-Al2O3 catalyst. The reaction temperature in the first reaction zone is 350℃, and the reaction temperature in the second reaction zone is 365℃. The product from the second reaction zone is subjected to high-pressure separation, a stripping tower, and a fractionation tower. The bottom oil cut temperature of the fractionation tower is controlled at 180℃. The product obtained from the bottom of the fractionation tower is a low-chain alkane oil-based drilling fluid base oil. Analysis using ASTM D86 standard shows that the fraction's temperature range is 180–285℃. Analysis using ASTM D 445 method shows a kinematic viscosity of 2.46 mmHg at 40℃. 2 / s. Analysis using SH / T0606 showed that the alkane content was 72wt%, the aromatic content was <0.4wt%, and the flash point was 65℃.

[0050] The test was conducted according to the methods specified in Q / SY 111-2007 "Classification and Detection Methods for Biotoxicity of Oilfield Chemicals and Drilling Fluids", EC 50 =30000mg / L.

[0051] Example 4:

[0052] Preparation of base oil for high-chain alkane oil-based drilling fluid: Straight-run diesel II is mixed with hydrogen and then contacted with catalysts in the first and second reaction zones. The system reaction pressure is 6 MPa, the hydrogen-to-oil ratio (v / v) is 1500, and the mass hourly space velocity (HHSV) in the first reaction zone is 0.5 h⁻¹. -1 The mass hourly space velocity (HHSV) in the second reaction zone is 3.0 h⁻¹. -1The catalyst in the first reaction zone is hydrorefined Ni-Mo-P / Al2O3, and the catalyst in the second reaction zone is hydrocracking Ni-W / USY-SiO2-Al2O3-Al2O3 catalyst. The reaction temperature in the first reaction zone is 350℃, and the reaction temperature in the second reaction zone is 380℃. The product from the second reaction zone is subjected to high-pressure separation, a stripping tower, and a fractionation tower. The bottom cut temperature of the fractionation tower is controlled at 235℃. The product obtained from the bottom of the fractionation tower is a high-chain alkane oil-based drilling fluid base oil. Analysis using ASTM D86 standard shows that the fraction's temperature range is 235–330℃. Analysis using ASTM D 445 method shows a kinematic viscosity of 2.65 mmHg at 40℃. 2 / s. Analysis using SH / T0606 showed that the alkane content was 96wt%, the aromatic content was <0.1wt%, and the flash point was 90℃.

[0053] The test was conducted according to the methods specified in Q / SY 111-2007 "Classification and Detection Methods for Biotoxicity of Oilfield Chemicals and Drilling Fluids", EC 50 =45100mg / L.

[0054] Example 5:

[0055] Preparation of base oil for high-chain alkane-based drilling fluid: Straight-run diesel II is mixed with hydrogen and then contacted with catalysts in the first and second reaction zones. The system reaction pressure is 12 MPa, the hydrogen-to-oil ratio (v / v) is 600, and the mass hourly space velocity (HHSV) in the first reaction zone is 3.0 h⁻¹. -1 The mass space velocity in the second reaction zone is 0.5 h⁻¹. -1 The catalyst in the first reaction zone is a hydrocracking Ni-W / USY-SiO2-Al2O3-Al2O3 catalyst, and the catalyst in the second reaction zone is a hydrorefining Ni-Mo-P / Al2O3 catalyst. 3。 The reaction temperature in the first reaction zone is 370℃, and the reaction temperature in the second reaction zone is 330℃. The product from the second reaction zone undergoes high-pressure separation, a stripping tower, and a fractionation tower. The bottom cutting temperature of the fractionation tower is controlled at 235℃. The product obtained from the bottom of the fractionation tower is a high-chain alkane oil-based drilling fluid base oil. Analysis using ASTM D86 standard shows that the fraction's temperature range is 235–330℃. Analysis using ASTM D 445 method shows a kinematic viscosity of 2.61 mmHg at 40℃. 2 / s. SH / T0606 analysis revealed an alkane content of 96.5 wt%, an aromatic content of <0.05 wt%, and a flash point of 92℃.

[0056] The test was conducted according to the methods specified in Q / SY 111-2007 "Classification and Detection Methods for Biotoxicity of Oilfield Chemicals and Drilling Fluids", EC 50 =46000mg / L.

[0057] Example 6:

[0058] Preparation of base oil for high-chain alkane-based drilling fluid: Straight-run diesel II is mixed with hydrogen and then contacted with catalysts in the first and second reaction zones. The system reaction pressure is 12 MPa, the hydrogen-to-oil ratio (v / v) is 600, and the mass hourly space velocity (HHSV) in the first reaction zone is 3.0 h⁻¹. -1 The mass space velocity in the second reaction zone is 0.5 h⁻¹. -1 The catalyst in the first reaction zone is a hydrocracking Ni-W / USY-SiO2-Al2O3-Al2O3 catalyst, and the catalyst in the second reaction zone is a hydrorefining Ni-Mo-P / Al2O3 catalyst. 3。 The reaction temperature in the first reaction zone is 360℃, and the reaction temperature in the second reaction zone is 330℃. The product from the second reaction zone undergoes high-pressure separation, a stripping tower, and a fractionation tower. The bottom cutting temperature of the fractionation tower is controlled at 235℃. 20% of the distillate obtained from the bottom of the fractionation tower is recycled back to the first reaction zone. The final fraction drawn from the bottom of the fractionation tower is a high-alkane oil-based drilling fluid base oil. Analysis using ASTM D86 standard shows that this fraction's temperature range is 235–330℃. Analysis using ASTM D445 method shows a kinematic viscosity of 2.58 mmHg at 40℃. 2 / s. Analysis using SH / T0606 showed that the alkane content was 97wt%, the aromatic content was <0.05wt%, and the flash point was 93℃.

[0059] The test was conducted according to the methods specified in Q / SY 111-2007 "Classification and Detection Methods for Biotoxicity of Oilfield Chemicals and Drilling Fluids", EC 50 =46200mg / L.

[0060] Example 7:

[0061] Using the high-chain alkane oil-based drilling fluid base oil obtained in Example 1 as the base fluid, a drilling fluid compatibility study was conducted. The drilling fluid formulation was: 240 mL base oil + 8% shear-lifting emulsifier + 2.5% organic clay + 60 mL 20% CaCl2 aqueous solution + 2% CaO + 4% filtration loss reducer (12 g) + 650 g barite. The apparent viscosity measured at 65°C was 52 mPa·s, the plastic viscosity was 41 mPa·s, and the dynamic shear force was 11 Pa. After hot rolling at 180°C, the apparent viscosity was 52 mPa·s, the plastic viscosity was 41 mPa·s, and the dynamic shear force was 12 Pa.

[0062] Comparative Example 3:

[0063] Using the base oil of the traditional mineral-based drilling fluid obtained in Comparative Example 1 as the base fluid, a drilling fluid compatibility study was conducted. The drilling fluid formula was: 240 mL base oil + 8 wt% shear-reducing emulsifier + 2.5 wt% organic clay + 60 mL 20 wt% CaCl2 aqueous solution + 2 wt% CaO + 4 wt% filtration loss reducer (12 g) + 650 g barite. The apparent viscosity measured at 65℃ was 66 mPa·s, the plastic viscosity was 47 mPa·s, and the dynamic shear force was 14 Pa. After hot rolling at 180℃, the apparent viscosity was 50 mPa·s, the plastic viscosity was 40 mPa·s, and the dynamic shear force was 10 Pa.

[0064] Through examples and comparative analyses, compared with traditional mineral-based oil-based drilling fluid base oils, the high-alkane oil-based drilling fluid base oil developed in this invention has lower aromatic content and higher alkane content, lower biotoxicity, and good drilling fluid compatibility.

[0065] Of course, the present invention may have other embodiments and variations. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and variations according to the present invention, but these corresponding changes and variations should all fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a base oil for high-chain alkane-based drilling fluid, characterized in that, Includes the following steps: a) After mixing mineral-based distillate oil and hydrogen, the mixture enters the first reaction zone containing a catalyst for reaction; b) The reaction products flowing out of the first reaction zone continue to enter the second reaction zone containing the catalyst for further reaction; c) The reaction products flowing out of the second reaction zone are subjected to high-pressure separation, stripping and fractionation. The fractionation is carried out in a fractionation tower with a bottom cutting temperature of 235°C. The unconverted bottom oil is the high-alkane oil-based drilling fluid base oil with an alkane content of ≥90wt% and a total aromatic content of <0.2wt%. The mineral-based distillate oil is mainly straight-run diesel oil; The pressure in the first reaction zone is 6-20 MPa, the reaction temperature is 330-370℃, and the space velocity is 0.5-3.0 h⁻¹. -1 The hydrogen-to-oil ratio is 600-1500 v / v; The pressure in the second reaction zone is the same as that in the first reaction zone, the reaction temperature is 340-380℃, and the space velocity is 0.5-3.0 h⁻¹. -1 The hydrogen-to-oil ratio is 600-1500 v / v; When the catalyst in the first reaction zone is a hydrorefining catalyst, the catalyst in the second reaction zone is a hydrocracking catalyst; When the catalyst in the first reaction zone is a hydrocracking catalyst, the catalyst in the second reaction zone is a hydrorefining catalyst; The hydrogenation refining catalyst is a hydrogenation catalyst containing at least one of Ni, W, Co, and Mo as a transition metal active phase, and simultaneously containing one or two non-metallic dopants of Si, P, B, and F. The support for the hydrogenation refining catalyst is at least one of γ-Al2O3 and amorphous silicon-aluminum. The hydrocracking catalyst is a bifunctional catalyst with cracking function. The active hydrogenation component of the hydrocracking catalyst is an oxide of one, two, or three of the metals selected from Ni, W, Co, and Mo. The acidic support of the hydrocracking catalyst contains at least one of zeolite, amorphous silica-alumina, and alumina.

2. The preparation method according to claim 1, characterized in that, The distillation range of the mineral-based distillate oil is 180-370℃.

3. The preparation method according to claim 2, characterized in that, The distillation range of the mineral-based distillate oil is 180-330℃.

4. The preparation method according to claim 1, characterized in that, The unconverted bottom oil portion is recycled to the first or second reaction zone.

5. The preparation method according to claim 1, characterized in that, The flash point of the base oil for the high-chain alkane oil-based drilling fluid is ≥80℃.

6. The preparation method according to claim 1, characterized in that, EC of the base oil for the high-alkane oil-based drilling fluid 50 ≥40000mg / L.

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