Base oil for high-paraffin oil-based drilling fluid and preparation method thereof

Abstract

The invention discloses base oil for high-paraffin oil-based drilling fluid and a preparation method of the base oil, the preparation method comprises the following steps: mixing mineral-based distillate oil and hydrogen, feeding the mixture into a first reaction zone and a second reaction zone which are filled with catalysts for reaction, and performing high-pressure separation, steam stripping and fractionation on a reaction product flowing out of the second reaction zone to obtain the high-paraffin oil-based drilling fluid. The base oil for the high-paraffin oil-based drilling fluid is obtained. The base oil for the high-paraffin oil-based drilling fluid developed by the invention has ultralow aromatic hydrocarbon content, ultrahigh paraffin content, lower biotoxicity and higher degradability.

Description

Technical Field

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

[0002] With the increasing number of unconventional oil and gas wells and increasingly complex geological conditions, the application scope of oil-based drilling fluids is becoming wider and wider. Oil-based drilling fluids are mainly composed of base fluids, emulsifiers, fluid loss reducers, organic soils, etc., and base fluids account for about 70% of the cost of oil-based drilling fluids. The average single-well consumption of base fluids in shale gas horizontal wells is nearly 300 cubic meters; the average single-well consumption of deep wells in the Tarim Kuche piedmont / Junggar Basin is 880 cubic meters; the annual consumption of base fluids by the group company is 200,000 cubic meters, with a cost of more than 1.6 billion yuan.

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

[0004] The synthetic-based drilling fluid system is a new type of drilling fluid system with environmentally friendly characteristics. It has the characteristics of oil-based drilling fluids such as resistance to high temperature, resistance to salt and calcium invasion, good wellbore stability, good lubricity and little damage to oil and gas layers. It also has at least the following characteristics: 1) Improve the technical level of oil and gas resource exploration and development in ecologically sensitive or environmentally fragile areas, and enhance global competitiveness; 2) Increase mechanical drilling speed and reduce drilling cycles; 3) Reduce annular pressure loss, improve ECD control level, and reduce the risk of downhole complexity and induced leakage; 4) Increase the reuse rate of drilling fluids and reduce comprehensive costs. Based on the above reasons and advantages, the development of drilling fluid base oils with similar synthetic-based performance is the development trend of oil-based drilling fluid base oils.

[0005] CN105713661B discloses a method for preparing a synthetic base oil for drilling fluid, comprising the following steps: 1) cutting a specific fraction product of Fischer-Tropsch synthesis into several fractions by distillation; 2) isomerizing one or several fractions of the obtained fractions, and controlling the degree of isomerization between 50% and 100% by changing the reaction conditions; 3) blending the obtained fractions that have been isomerized and those that have not been isomerized in proportion according to the application requirements of the drilling fluid; 4) distilling the blended product, removing the low-carbon hydrocarbons of the hydrogenation isomerization byproduct, and obtaining a base oil sample for performance testing and commercial application. The method mainly uses the fraction of Fischer-Tropsch synthesis as a raw material, and realizes the production of synthetic base oil for drilling fluid through processes such as hydrogenation isomerization and blending.

[0006] CN110964564A discloses a Fischer-Tropsch synthesis-based drilling fluid base oil and a preparation method thereof, the preparation method comprising: cracking and isomerizing the Fischer-Tropsch synthesis product; directly fractionating the Fischer-Tropsch synthesis product after the cracking and isomerization treatment to obtain a base oil product or fractionating the Fischer-Tropsch synthesis product after the hydrofining treatment to obtain a base oil product; wherein the fractionation comprises atmospheric pressure fractionation, and the process conditions of atmospheric pressure fractionation are: tower top temperature 100-120°C, tower top pressure 0.01-0.2MPa, and side line extraction temperature 170-190°C. The method requires the Fischer-Tropsch product as a raw material, and only through cracking and isomerization-post-refining can a suitable drilling fluid base oil be produced.

[0007] CN113136181B discloses a biosynthetic drilling fluid and a preparation method thereof. The raw materials of the biosynthetic drilling fluid include: biodiesel, calcium chloride solution, organic soil, primary emulsifier, secondary emulsifier, fluid loss reducer, wetting agent, lime, flow pattern regulator, barite powder; calculated by weight, the biodiesel is 80 to 90 parts, the calcium chloride solution is 20 to 10 parts; the primary emulsifier is polyamide fat HYOZ, the secondary emulsifier is amidoamine HYOF, and the flow pattern regulator is polyamide HYON. The biosynthetic drilling fluid provided by this technology can overcome the serious environmental pollution problems of oil-based rock cuttings and waste oil-based drilling fluids produced by conventional oil-based drilling fluids, such as difficulty in degradation, strong biological toxicity, and containing aromatic substances. It needs to rely on biodiesel as a raw material to ensure that the raw material contains a large amount of isomeric paraffins. At the same time, Xie Yuning et al. (Petroleum Drilling Technology, 2019, 47, 34-39) also revealed that animal and plant oils, microbial oils and other catering waste oils can be used as raw materials for biosynthetic base oils, and the 96h half-lethal concentration LC50 of its synthetic drilling fluid base oil is greater than 1000000 mg / L.

[0008] CN110698329A discloses a method for preparing biomass synthetic oil for drilling fluid, comprising: reacting halogenated dodecane, an acid-binding agent and an alkyl alcohol under the action of a catalyst to obtain biomass synthetic oil for drilling fluid. The method provided by the technology prepares biomass synthetic oil for drilling fluid, and the synthesis temperature is low. The biomass synthetic oil dodecyl ether has good inhibition, low viscosity, strong temperature resistance, hydrolysis stability and biodegradability, and can be used as a base oil for synthetic drilling fluid. However, in the acid-base environment of the formation, although the biomass synthetic oil can be degraded, it cannot maintain the stability of the synthetic oil, which affects the safety performance of drilling use.

[0009] In summary, in order to obtain low-toxic oil-based drilling fluid base oil, the main characteristics are high paraffin content and low aromatic content. In the product field, the main products are synthetic drilling fluid base oils oriented by Fischer-Tropsch, poly-α-olefins (LAO), linear paraffins, internal olefins, biomass-synthesized drilling fluid base oils, and synthetic drilling fluid base oils of ethers or bio-esters. However, the above-mentioned unit processes or products are relatively difficult to synthesize or the synthesis cost is high in the industry, which greatly limits the promotion of low-toxicity, high-paraffin drilling fluid base oils. The paraffin content of traditional mineral-based drilling fluid base oils is generally 20-60wt%, which cannot meet the demand for high paraffin content. At the same time, if supporting processes such as molecular sieve dewaxing and solvent dewaxing are used, it is still necessary to combine unit processes such as hydrogenation isomerization to realize the conversion of wax to oil, and the process route is also relatively complicated. Summary of the invention

[0010] The technical problem to be solved by the present invention is to increase the paraffin content of the base oil of the traditional white oil-based or diesel-based mineral-based drilling fluid, reduce its biological toxicity during use, and improve its degradability efficiency.

[0011] In order to solve the problems of limited raw materials and processes in the traditional production of synthetic base drilling fluid base oils, improve the application and promotion of drilling fluid base oils with high chain alkane content, improve their biodegradability and reduce their biotoxicity, the present invention combines the reaction characteristics of hydrocarbon conversion and the composition requirements of hydrocarbon molecules in terms of biotoxicity and biodegradability. The present invention provides a drilling fluid base oil with high chain alkane and low aromatic content produced by using mineral oil as a raw material and a process thereof, which can effectively broaden the product source of synthetic base drilling fluid base oils and effectively reduce their production costs.

[0012] To achieve the above purpose, a method for preparing a base oil for high paraffin oil-based drilling fluid, wherein the base oil has a paraffin content of ≮90wt% and an aromatic content of ≯0.2wt%. The preparation method comprises the following steps:

[0013] a) mixing the mineral-based distillate oil and hydrogen and then entering a first reaction zone equipped with a catalyst for reaction;

[0014] b) the reaction product flowing out of the first reaction zone continues to enter the second reaction zone equipped with a catalyst for reaction;

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

[0016] The method for preparing the base oil for high-chain alkane oil-based drilling fluid of the present invention, the mineral-based distillate oil is mainly straight-run diesel oil, and the distillation range is 180-370°C, preferably 180-330°C.

[0017] In the method for preparing base oil for high-chain paraffin 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 paraffin 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] According to the selected mineral oil distillation range of 180-330°C, the grading of the reactor can be optimized according to the flow direction of the reaction materials, the reaction directions of hydrorefining and hydrocracking can be adopted, and the method of first contacting the hydrocracking catalyst and then contacting the hydrorefining catalyst can be adopted. Both of these can achieve the production of drilling fluid base oil with a high paraffin content from traditional mineral oil.

[0020] The present invention does not particularly limit the hydrorefining catalyst. The hydrorefining catalyst includes but is not limited to a hydrogenation catalyst containing at least one of Ni, W, Co, and Mo as a transition metal active phase, and containing one or two non-metallic doped hydrogenation catalysts of Si, P, B, and F. The carrier thereof may 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 commercial hydrorefining catalysts may also be used, such as PHD, PHF, FHUDS, RS, HYT and other hydrorefining catalysts to meet the requirements of desulfurization and denitrogenation or aromatic saturation.

[0021] The present invention does not particularly limit the hydrocracking catalyst, and the hydrocracking catalyst includes but is not limited to a bifunctional catalyst containing a cracking function, wherein the active hydrogenation component is an oxide of one, two or three metals selected from Ni, W, Co and Mo, and the acidic carrier contains at least one of faujasite, amorphous silica-alumina and alumina. A commercially available or commercial medium-oil type or flexible hydrocracking catalyst is also used to meet the performance requirements of low naphtha yield under high temperature conditions, and the hydrocracking catalyst is required to preferentially convert aromatics or cycloalkanes.

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

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

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

[0025] The present invention also provides a base oil for high-chain alkane oil-based drilling fluid, wherein the chain alkane content is ≮90wt%, the aromatic content is ≯0.2wt%, and the flash point is ≮80°C.

[0026] The high-chain paraffin oil-based drilling fluid base oil of the present invention has an EC 50 ≮40000mg / L.

[0027] The yield of the unconverted oil at the bottom of the tower is closely related to the reaction depth, and is also closely related to the paraffin content of the raw material. Generally speaking, the product of the yield of the unconverted oil at the bottom of the tower and the paraffin content at the bottom of the tower is lower than the paraffin content of the raw material. Based on this relationship, by controlling the appropriate conversion depth, the enrichment of the high paraffin content at the bottom of the tower is achieved. The preparation of the drilling fluid base oil with a high paraffin content of the present invention is closely related to the conversion efficiency of the mineral oil. Under the premise of considering the product distribution and economy, the high paraffin content enrichment of the unconverted oil can be achieved by a one-time pass or a partial tail oil circulation mode. More light components or gases may be produced in the one-time pass mode, and the enrichment of the unconverted oil paraffin can be achieved by a partial circulation mode.

[0028] Compared with synthetic drilling fluid base oil, bio-based drilling fluid base oil, and ether / ester drilling fluid base oil, the high-chain alkane oil-based drilling fluid base oil developed by the present invention has ultra-low aromatics, ultra-high chain alkane content, lower biological toxicity, higher degradability, and good drilling fluid compatibility. Based on the understanding of hydrocarbon molecular transformation, the present invention preferentially realizes the transformation of cycloalkanes and aromatics through the grading mode of hydrorefining catalyst and hydrocracking catalyst under the catalytic action of double reaction functional zones, and retains chain alkanes to the maximum extent. At the same time, according to the efficiency of transformation and the molecular characterization of the carbon number of the product, combined with the distillation and reaction cycle mode, the enrichment of chain alkanes, the transformation of cycloalkanes, and the hydrogenation saturation and secondary transformation of aromatics are realized, and the chain alkanes of the unconverted bottom oil are enriched, and the total chain alkanes content is greater than 90wt%, and the aromatics content is less than 0.2wt%. In this way, the source of high-chain alkane content drilling fluid base oil can be effectively expanded, and the dependence on synthetic base, bio-based and ether / ester can be reduced. The present invention can also avoid secondary processing and reduce costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the carbon number distribution diagram of the base oil for the high paraffin content mineral-based drilling fluid of Example 1. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below in conjunction with specific embodiments, but the present invention is not limited by the following embodiments. Any modification that does not exceed the concept and scope of the present invention is 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 of straight-run diesel raw materials

[0033]

[0034]

[0035] Embodiment 1:

[0036] Preparation of base oil for high-chain alkane oil-based drilling fluid: After the straight-run diesel I is mixed with hydrogen, it is contacted with the catalysts in the first reaction zone and the second reaction zone. The system reaction pressure is 6 MPa, the hydrogen-to-oil ratio (v / v) is 1000, and the mass space velocity in the first reaction zone is 1.5 h -1 , the mass space velocity in the second reaction zone is 1.5h -1The catalyst in the first reaction zone is hydrorefined Ni-Mo-P / Al2O3, and the catalyst in the second reaction zone is hydrocracked Ni-W / USY-SiO2-Al2O3-Al2O3 catalyst. The reaction temperature in the first reaction zone is 350°C, and the reaction temperature in the second reaction zone is 365°C. The products passing through the second reaction zone are passed through high-pressure separation, stripping tower and fractionation tower. The cutting temperature at the bottom of the controlled fractionation tower is 235°C. The product obtained from the bottom of the fractionation tower is the base oil for high-chain alkane oil-based drilling fluid. ASTM D86 standard analysis was used. The fraction of the fraction was 235-285℃, and the kinematic viscosity of 40℃ was analyzed by ASTM D 445 method. 2 / s. The paraffin content was 92wt% and the aromatic content was <0.1wt% by SH / T0606 analysis. The flash point was 90℃. The relative content distribution of paraffin is shown in Figure 1 shown.

[0037] The test was conducted according to Q / SY 111-2007 "Classification and Detection Methods of Biological Toxicity 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 fluid: The difference from Example 1 is that only the first reaction zone is used, and the second reaction zone is not used.

[0040] After the straight-run diesel I is mixed with hydrogen, it contacts 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 space velocity in the first reaction zone is 1.5 h -1 The catalyst in the first reaction zone is hydrofined Ni-Mo-P / Al2O3, the reaction temperature in the first reaction zone is 350℃, the product in the first reaction zone is separated by high pressure, stripped and fractionated, and the product obtained from the bottom of the fractionation tower is a base oil for traditional mineral-based drilling fluid. The fraction is analyzed by ASTM D86 standard, the fraction is 200-310℃, and the kinematic viscosity at 40℃ is 2.85mm by ASTM D445 method. 2 / s, the paraffin content obtained by SH / T0606 analysis method is 48wt%, the total amount of aromatics is 8.1wt%, and the flash point is 75℃.

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

[0042] Embodiment 2:

[0043] Preparation of base oil for high-chain alkane oil-based drilling fluid: After the straight-run diesel II is mixed with hydrogen, it is contacted with the catalysts in the first reaction zone and the second reaction zone. The system reaction pressure is 6 MPa, the hydrogen-to-oil ratio (v / v) is 1200, and the mass space velocity in the first reaction zone is 1.5 h -1 , the mass space velocity in the second reaction zone is 1.3h -1 The catalyst in the first reaction zone is Ni-Mo-P / Al2O3 for hydrofining, and the catalyst in the second reaction zone is Ni-W / USY-SiO2-Al2O3-Al2O3 for hydrocracking. The reaction temperature in the first reaction zone is 360°C, and the reaction temperature in the second reaction zone is 375°C. The product in the second reaction zone is separated by high pressure, and then separated by a stripping tower and a fractionating tower. The product obtained from the bottom of the fractionating tower is a base oil for high-chain alkane oil-based drilling fluid. The fraction is analyzed by ASTM D86 standard, and the fraction has a fraction range of 235-330°C. The kinematic viscosity at 40°C is 2.95mm by ASTM D 445 method. 2 / s. The paraffin content was 94wt% and the aromatic content was <0.2wt% according to SH / T0606 analysis. The flash point was 95°C.

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

[0045] Embodiment 3:

[0046] Preparation of base oil for high-chain paraffin oil-based drilling fluid: After the straight-run diesel I is mixed with hydrogen, it is contacted with the catalysts in the first reaction zone and the second reaction zone. The system reaction pressure is 12 MPa, the hydrogen-to-oil ratio (v / v) is 1000, and the mass space velocity in the first reaction zone is 1.5 h -1 , the mass space velocity in the second reaction zone is 1.5h -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 hydrofining Ni-Mo-P / Al2O3 catalyst. The reaction temperature in the first reaction zone is 370°C, and the reaction temperature in the second reaction zone is 370°C. The product in the second reaction zone is separated by high pressure, and then separated by a stripping tower and a fractionating tower. The product obtained from the bottom of the fractionating tower is a base oil for high-chain alkane oil-based drilling fluid. The fraction is analyzed by ASTM D86 standard, and the distillation section of the fraction is 235-285°C. The kinematic viscosity at 40°C is 2.68mm by ASTM D 445 method. 2 / s. The paraffin content was 95wt% and the aromatic content was <0.05wt% according to SH / T0606 analysis. The flash point was 100°C.

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

[0048] Comparative Example 2:

[0049] Preparation of base oil for low paraffin oil-based drilling fluid: After the straight-run diesel I is mixed with hydrogen, it is contacted with the catalysts in the first reaction zone and the second reaction zone. The system reaction pressure is 6 MPa, the hydrogen-to-oil ratio (v / v) is 1000, and the mass space velocity in the first reaction zone is 1.5 h -1 , the mass space velocity in the second reaction zone is 1.5h -1 The catalyst in the first reaction zone is Ni-Mo-P / Al2O3 for hydrofining, and the catalyst in the second reaction zone is Ni-W / USY-SiO2-Al2O3-Al2O3 for hydrocracking. The reaction temperature in the first reaction zone is 350°C, and the reaction temperature in the second reaction zone is 365°C. The product in the second reaction zone is separated by high pressure, stripped and fractionated. The fractionation tower bottom oil cutting temperature is controlled to be 180°C. The product obtained from the bottom of the fractionation tower is a base oil for low-chain paraffin oil-based drilling fluid. The fraction is analyzed by ASTM D86 standard, and the fraction has a fraction range of 180-285°C. The kinematic viscosity at 40°C is 2.46mm by ASTM D 445 method. 2 / s. The paraffin content was 72wt% and the aromatic content was <0.4wt% by SH / T0606 analysis, and the flash point was 65°C.

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

[0051] Embodiment 4:

[0052] Preparation of base oil for high-chain alkane oil-based drilling fluid: After the straight-run diesel II is mixed with hydrogen, it is contacted with the catalysts in the first reaction zone and the second reaction zone. The system reaction pressure is 6 MPa, the hydrogen-to-oil ratio (v / v) is 1500, and the mass space velocity in the first reaction zone is 0.5 h -1 , the mass space velocity in the second reaction zone is 3.0h -1The catalyst in the first reaction zone is Ni-Mo-P / Al2O3 for hydrofining, and the catalyst in the second reaction zone is Ni-W / USY-SiO2-Al2O3-Al2O3 for hydrocracking. The reaction temperature in the first reaction zone is 350°C, and the reaction temperature in the second reaction zone is 380°C. The product in the second reaction zone is separated by high pressure, and the stripping tower and fractionation tower are used. The cutting temperature at the bottom of the fractionation tower is controlled to be 235°C. The product obtained from the bottom of the fractionation tower is a base oil for high-chain alkane oil-based drilling fluid. The fraction is analyzed by ASTM D86 standard, and the fraction has a fraction range of 235-330°C. The kinematic viscosity at 40°C is 2.65mm by ASTM D 445 method. 2 / s. The paraffin content was 96wt% and the aromatic content was <0.1wt% by SH / T0606 analysis, and the flash point was 90°C.

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

[0054] Embodiment 5:

[0055] Preparation of base oil for high-chain paraffin oil-based drilling fluid: After the straight-run diesel II is mixed with hydrogen, it is contacted with the catalysts in the first reaction zone and the second reaction zone. The system reaction pressure is 12 MPa, the hydrogen-to-oil ratio (v / v) is 600, and the mass space velocity in the first reaction zone is 3.0 h -1 , the mass space velocity in the second reaction zone is 0.5h -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 / Al2O 3。 The reaction temperature of the first reaction zone is 370℃, and the reaction temperature of the second reaction zone is 330℃. The product of the second reaction zone is separated by high pressure, stripped and fractionated. The cutting temperature of the bottom of the fractionated tower is controlled to be 235℃. The product obtained from the bottom of the fractionated tower is a base oil for high-chain alkane oil-based drilling fluid. The fraction is analyzed by ASTM D86 standard, and the distillation section of the fraction is 235~330℃. The kinematic viscosity at 40℃ is 2.61mm by ASTM D 445 method. 2 / s. The paraffin content was 96.5wt% and the aromatic content was <0.05wt% according to SH / T0606 analysis. The flash point was 92°C.

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

[0057] Embodiment 6:

[0058] Preparation of base oil for high-chain paraffin oil-based drilling fluid: After the straight-run diesel II is mixed with hydrogen, it is contacted with the catalysts in the first reaction zone and the second reaction zone. The system reaction pressure is 12 MPa, the hydrogen-to-oil ratio (v / v) is 600, and the mass space velocity in the first reaction zone is 3.0 h -1 , the mass space velocity in the second reaction zone is 0.5h -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 / Al2O 3。 The reaction temperature of the first reaction zone is 360℃, and the reaction temperature of the second reaction zone is 330℃. The product of the second reaction zone is separated by high pressure, stripped and fractionated. The cutting temperature of the bottom of the fractionated tower is controlled to be 235℃. 20% of the distillate oil obtained from the bottom of the fractionated tower is recycled to the first reaction zone. Finally, the distillate extracted from the bottom of the fractionated tower is used as the base oil for drilling fluid. The distillate is analyzed by ASTMD86 standard. The distillate section is 235~330℃. The kinematic viscosity at 40℃ is 2.58mm by ASTM D 445 method. 2 / s. The paraffin content was 97wt%, the aromatic content was <0.05wt%, and the flash point was 93°C according to SH / T0606 analysis.

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

[0060] Embodiment 7:

[0061] The high-chain alkane oil-based drilling fluid base oil obtained in Example 1 was used as the base fluid for drilling fluid compatibility research. The drilling fluid formula was: 240mL base oil + 8% shear-enhancing emulsifier + 2.5% organic soil + 60mL 20% CaCl2 aqueous solution + 2% CaO + 4% filtrate reducer (12g) + 650g barite. The apparent viscosity measured at 65°C was 52mPa·s, the plastic viscosity was 41mPa·s, and the dynamic shear force was 11Pa. The apparent viscosity after hot rolling at 180°C was 52mPa·s, the plastic viscosity was 41mPa·s, and the dynamic shear force was 12Pa.

[0062] Comparative Example 3:

[0063] The conventional mineral-based oil-based drilling fluid base oil obtained in Comparative Example 1 was used as the base oil for drilling fluid compatibility research. The drilling fluid formula was: 240 mL base oil + 8 wt % shear-enhancing emulsifier + 2.5 wt % organic soil + 60 mL 20 wt % CaCl2 aqueous solution + 2 wt % CaO + 4 wt % filtration reducer (12 g) + 650 g barite. The apparent viscosity measured at 65 ° C was 66 mPa·s, the plastic viscosity was 47 mPa·s, and the dynamic shear force was 14 Pa. The apparent viscosity after hot rolling at 180 ° C was 50 mPa·s, the plastic viscosity was 40 mPa·s, and the dynamic shear force was 10 Pa.

[0064] Through examples and comparative analysis, compared with traditional mineral-based oil-based drilling fluid base oil, the high-paraffin oil-based drilling fluid base oil developed by the present invention has lower aromatic content and higher paraffin content, lower biological toxicity and good drilling fluid compatibility.

[0065] Of course, the present invention may have many other embodiments and variations thereof. Without departing from the spirit and essence of the present invention, technicians familiar with the field may make various corresponding changes and variations based on the present invention, but these corresponding changes and variations should all fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a base oil for high paraffin oil-based drilling fluid, wherein the paraffin content of the base oil is ≮90wt%, and the total aromatic content is <0.2wt%, characterized in that: The steps include: a) mixing the mineral-based distillate oil and hydrogen and then entering a first reaction zone equipped with a catalyst for reaction; b) the reaction product flowing out of the first reaction zone continues to enter the second reaction zone equipped with a catalyst for reaction; c) The reaction product flowing out from the second reaction zone is subjected to high pressure separation, steam stripping and fractionation to obtain unconverted bottom oil, which is the base oil for high-chain paraffin oil-based drilling fluid.

2. The preparation method according to claim 1, characterized in that: The mineral-based distillate oil is mainly straight-run diesel with a distillation range of 180-370°C.

3. The preparation method according to claim 2, characterized in that: The mineral-based distillate oil has a distillation range of 180-330°C.

4. The preparation method according to claim 1, characterized in that: When the catalyst in the first reaction zone is a hydrotreating catalyst, the catalyst in the second reaction zone is a hydrocracking catalyst.

5. The preparation method according to claim 1, characterized in that: When the catalyst in the first reaction zone is a hydrocracking catalyst, the catalyst in the second reaction zone is a hydrotreating catalyst.

6. The preparation method according to claim 1, characterized in that: The pressure of the first reaction zone is 6-20 MPa, the reaction temperature is 330-370°C, and the space velocity is 0.5-3.0 h -1 , the hydrogen-to-oil ratio is 600-1500v / v.

7. The preparation method according to claim 1, characterized in that: The pressure of the second reaction zone is consistent with that of the first reaction zone, the reaction temperature is 340-380°C, and the space velocity is 0.5-3.0h -1 , the hydrogen-to-oil ratio is 600-1500v / v.

8. The preparation method according to claim 1, characterized in that: The initial boiling point of the unconverted tower bottom oil is not less than 200°C, and the viscosity of the unconverted tower bottom oil at 40°C is in the range of 2.2-3.0 mm 2 / s.

9. A base oil for high-chain paraffin oil-based drilling fluid, characterized in that: Paraffin content ≮90wt%, aromatic content ≯0.2wt%, flash point ≮80℃.

10. The base oil for high-chain paraffin oil-based drilling fluid according to claim 1, characterized in that: The unconverted oil at the bottom of the fractionation tower can be partially recycled to the first reactor or the second reactor; EC of the base oil for the high paraffin oil-based drilling fluid 50 ≮40000mg / L.

Images