Preparation method of olefin-rich mixed drilling fluid base oil

Abstract

The application relates to a preparation method of a rich olefin mixed type drilling fluid base oil, comprising the following steps: carrying out non-hydrogen treatment on high-temperature Fischer-Tropsch synthesis oil to obtain the drilling fluid base oil, wherein the high-temperature Fischer-Tropsch synthesis oil is a product obtained by synthesizing low-carbon alkanes and olefins at 280-420 DEG C through Fischer-Tropsch synthesis, and the non-hydrogen treatment comprises at least one time of fraction cutting and at least one time of deoxygenation treatment. The prepared drilling fluid base oil has the advantages of a wide adjustable range, high safety, low viscosity, good low-temperature fluidity, non-toxicity, easy biodegradation and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of synthetic base drilling fluid base oil, and particularly relates to a preparation method of an olefin-rich mixed drilling fluid base oil. BACKGROUND

[0002] Drilling fluid is the blood of drilling engineering. In modern drilling technology, the application of advanced drilling fluid technology and high-quality drilling fluid can ensure safe, high-quality and rapid drilling, and can quickly achieve good oil and gas exploration results, and effectively develop and exploit oil and gas fields. It plays a very important role in drilling complex formations, ensuring safety underground, preventing chemical pollution, overcoming bottom hole temperature and the like.

[0003] The drilling fluid composition usually includes base fluid, filtrate reducer, viscosity enhancer, emulsifier, shale inhibitor, plugging agent, viscosity reducer, corrosion inhibitor, clay, lubricant, weighting agent, bactericide, defoamer, foaming agent, flocculant, lubricant and the like ten components, wherein the base fluid occupies the largest volume. According to the type of base fluid, it can be divided into two categories of water-based drilling fluid and oil-based drilling fluid. Compared with water-based drilling fluid, oil-based drilling fluid has many advantages such as high temperature resistance, salt and calcium invasion resistance, good lubricity, low damage to oil and gas layers and the like, and has become an important means for drilling high-difficulty high-temperature deep wells, offshore drilling, large-inclination directional wells, horizontal wells, complex process wells and reservoir protection. However, the traditional white oil and mineral oil have poor biodegradability and can easily affect the environment. In addition, the drilling fluid system prepared by taking diesel oil and white oil as the base has unstable rheological properties, and sometimes the apparent viscosity increases sharply under low temperature, which leads to excessive circulating pump pressure and seriously affects the normal operation of drilling operation. Therefore, synthetic base drilling fluid with biodegradability and good rheological property has gradually attracted attention.

[0004] Synthetic base drilling fluid, also called imitation oil-based drilling fluid, is a non-water-soluble synthetic oil-based drilling fluid, which has the operation performance of oil-based drilling fluid and has basically the same composition as oil-based drilling fluid. The fraction contained in the synthetic base drilling fluid basically does not contain aromatic compounds and is basically non-toxic to mammals, and can meet the discharge requirements after field use. At present, it has been applied in more than 800 wells in the world, which are located in the Gulf of Mexico, the North Sea, the Far East, the European continent, South America and other regions, and Australia, Mexico and Russia, among which the Gulf of Mexico and the North Sea account for 90%.

[0005] Different products have been applied internationally in the 1990s, and under the promotion of major oil service companies, synthetic base drilling fluid has developed rapidly. For example, Petrofree system of Baroid Company, Quad Drill system of Dowell Company, Bio-drill system of Mipark Company and Novadrill system of M-I Company.

[0006] The first generation of synthetic base drilling fluid is represented by ester group, ether group, poly-alpha-olefin, acetal group, etc. The second generation of synthetic base drilling fluid is represented by linear alpha-olefin, internal olefin, linear alkyl benzene, linear paraffin group. Ester is the first generation of synthetic material used for preparing drilling fluid, and the drilling with ester base drilling fluid was successful in Norway in March 1990. Inspired by the ester base drilling fluid, ether base drilling fluid was developed in 1991. Ether base drilling fluid was used in offshore oil fields in Norway and Mexico Gulf in May and June 1992 respectively, and then was widely used. At the end of 1992, acetal base drilling fluid was used, but due to its high cost, it was less used. In the following three years (1993-1995), the second generation of synthetic material represented by linear alkyl benzene (LAB), linear paraffin (LP), linear olefin, etc. was developed by drilling fluid researchers, and its drilling fluid system was rapidly and widely used in the North Sea of Britain and the Gulf of Mexico. With the development of coal-to-oil industry, Fischer-Tropsch synthetic oil has certain environmental advantages due to no sulfur and nitrogen impurities, and is widely concerned. Energy companies represented by Shell Company developed synthetic base alkane type drilling fluid base oil, and it was widely used.

[0007] Fischer-Tropsch synthesis is a process of synthesizing hydrocarbons, oxygen-containing compounds and water from synthesis gas containing hydrogen and carbon monoxide under the reaction conditions of catalyst and certain temperature and pressure, and is widely used in coal indirect liquefaction, natural gas to oil and biomass to oil and other oil replacement technologies, and has important significance for relieving the dependence of domestic energy on oil resources. Fischer-Tropsch synthesis can be divided into two types according to the reaction temperature and product composition. One is low-temperature Fischer-Tropsch which generates long-chain heavy oil or Fischer-Tropsch wax at low temperature (220-250℃), and the carbon number distribution range is wide, and from C4 to C60 or even C100 is distributed in the liquid product, of which 80-90% are normal alkanes, and a small amount of isomeric hydrocarbons, olefins, oxygen-containing compounds and other components. The other is high-temperature Fischer-Tropsch which synthesizes low-carbon alkanes and olefins at high temperature (300-350℃), and the carbon number distribution of the synthesis product is relatively narrow, mainly concentrated below C20, and the content of olefin component accounts for more than half, which is called high-temperature Fischer-Tropsch, and the obtained product is high-temperature Fischer-Tropsch oil.

[0008] Low-temperature Fischer-Tropsch oil is mainly linear alkanes, which is a good processing raw material for alkane base drilling fluid base oil. By controlling the appropriate distillation distribution, the flash point range of the product can be adjusted, and the higher the boiling point, the higher the corresponding flash point. Compared with isomeric alkanes, the pour point of linear alkanes is low, and for some low-temperature areas, linear alkane base oil cannot be directly used, and must be subjected to hydrogenation isomerization treatment to change linear alkanes into branched isomeric alkanes by isomerization, so as to reduce the pour point of the oil product and broaden the application range of the base oil.

[0009] CN110964564A discloses a Fischer-Tropsch synthesis-based drilling fluid base oil and a preparation method thereof, comprising the following steps: directly performing cracking isomerization treatment on Fischer-Tropsch synthesis products; directly performing fractionation on the Fischer-Tropsch synthesis products after cracking isomerization treatment to obtain a base oil product or performing fractionation after hydrofining treatment to obtain a base oil product, the proportion of isomeric alkanes in the obtained base oil product is 60 wt% or more; wherein the fractionation comprises atmospheric fractionation, and the process conditions of the atmospheric fractionation are as follows: a tower top temperature of 100-120 ℃, a tower top pressure of 0.01-0.2 MPa, and a side line extraction temperature of 170-190 ℃. The invention also describes a processing flow for producing an alkane-based drilling fluid base oil from Fischer-Tropsch synthesis products after hydrocracking isomerization treatment.

[0010] CN105713661A discloses a method for preparing base oil from Fischer-Tropsch synthesis products, comprising: a, cutting Fischer-Tropsch synthesis specific fraction products into several fractions by distillation; b, performing isomerization treatment on one or more of the obtained several fractions, and controlling the isomerization degree to be between 50-100% by changing the reaction conditions; c, blending the isomerization-treated and non-isomerization-treated several fraction oils according to the application requirements of drilling fluids; d, performing distillation on the blended product to remove the hydrogenation isomerization by-products low-carbon hydrocarbons, and obtaining base oil samples for performance testing and commercial application.

[0011] CN1761734A discloses a method for preparing base oil from Fischer-Tropsch synthesis products, comprising: (a) separating the Fischer-Tropsch synthesis products into a fraction (i) having a boiling point in the range of middle distillate oil and lower, a heavy tail fraction (iii), and a middle base oil precursor fraction (ii) having a boiling point between the fraction (i) and the fraction (iii); (b) subjecting the base oil precursor fraction (ii) to a catalytic hydroisomerization and catalytic dewaxing process to produce one or more base oil grades; (c) subjecting the heavy tail fraction (iii) to a conversion step to produce a fraction (iv) having a boiling point lower than the heavy tail fraction (iii); and (d) subjecting a high-boiling fraction (v) of the fraction (iv) to a catalytic hydroisomerization and catalytic dewaxing process to produce one or more base oil grades.

[0012] The above patents all use low-temperature Fischer-Tropsch synthesis oil to produce alkane-based drilling fluid base oil, most of which need to undergo isomerization process, and the obtained base oil is usually mainly isomeric alkanes with a small amount of n-alkanes. The hydrocracking or hydroisomerization process is usually a high-pressure reaction process with a pressure of 10 MPa or more, the reaction conditions are harsh, the device energy consumption is high, and in addition, the catalyst used in the isomerization reaction is usually a noble metal catalyst, the production cost is high.

[0013] The existing drilling fluid base oil with olefin components, mainly poly-α-olefin base drilling fluid, is derived from linear α-olefins and isomers of the mixture or internal olefins and internal olefin isomers. The α-olefin product is derived from the Ziegler chain growth process, and the product is mainly linear α-olefins. The mixture of such oil products generally has a high pour point, and most of them need to be treated by isomerization process to achieve the purpose of pour point reduction and pour point reduction.

[0014] WO9521226(A1) discloses a drilling fluid for use in subterranean oil and gas wells, the base oil of which is a mixture of straight and branched chain olefins, the majority of which are straight chain olefins, said olefins having at least 12 carbon atoms, preferably C14 to C18 olefins. In the mixture of the present invention, the majority of the olefins are linear, meaning that 50-100%, preferably 60-100%, more preferably 70-80% of the olefins in the mixture do not have branching points along the hydrocarbon chain. On the other hand, it is further preferred that such a mixture also contains olefins with some side chain branching, preferably branched olefins account for at least 5%, preferably at least 10% of the mixture.

[0015] WO9907805(A1) discloses a base oil mixture for preparing a low pour point drilling fluid, the base oil is composed of isomers of linear internal tetradecene and isomers of linear internal hexadecene, the base oil has a pour point lower than -25°C, and is suitable for drilling in cold and offshore areas.

[0016] Generally, the drilling fluid base oil with linear α-olefins, internal olefins and the like as the main component, although it has excellent viscosity performance and high flash point, has a high pour point, and generally needs to be isomerized to reduce the pour point of the oil product. WO0132590(A3) discloses an isomerization method for a mixture of linear α-olefins with 10-35 carbon atoms of ethylene and vinylidene, after isomerization, at least 70% by weight of the mixture is di- or tri-substituted internal olefin; at least 20% by weight is tri-substituted internal olefin; at least 20% by weight of the product mixture is di-substituted internal olefin with double bonds at the fourth or higher numbered carbon atom position, and less than 50% by weight is di-substituted internal olefin with double bonds at the second or third numbered carbon atom position. The invention also discloses a reverse phase drilling fluid comprising at least about 50% by volume of base oil, wherein at least about 25% by volume, more preferably 75% by volume of the base oil content of the drilling fluid is the above-mentioned mixture after isomerization.

[0017] In the above patents, the base oil with saturated alkane components or the base oil with α-olefin, internal olefin and the like olefin components as the main component, most of which need to be treated by hydrogenation isomerization process to achieve the purpose of pour point reduction and pour point reduction. SUMMARY

[0018] Based on the above, the purpose of the present application is to provide an olefin-rich mixed drilling fluid base oil and a preparation method thereof. The preparation method of the present application uses high-temperature Fischer-Tropsch oil as a raw material to prepare a drilling fluid base oil. The composition characteristics of the high-temperature Fischer-Tropsch oil (narrow carbon number distribution, mainly below C20, with an olefin component content of more than 50% of the total amount of hydrocarbons, and mainly α-olefins, in addition to some internal olefins and alkanes) are processed by separation. No hydrogenation isomerization treatment is required, which greatly reduces the production cost.

[0019] To this end, the present application provides a preparation method of an olefin-rich mixed drilling fluid base oil, comprising the following steps: subjecting high-temperature Fischer-Tropsch synthetic oil to non-hydrogen treatment to obtain a drilling fluid base oil, the high-temperature Fischer-Tropsch synthetic oil being a product obtained by synthesizing low-carbon alkanes and olefins at 280-420°C, preferably 300-350°C, by Fischer-Tropsch synthesis, and the non-hydrogen treatment comprising at least one fraction cutting and at least one deoxygenation treatment.

[0020] Specifically, the order of fraction cutting and deoxygenation treatment in the preparation method of the present application is not limited. Fraction cutting can be performed first, or deoxygenation treatment can be performed first.

[0021] The preparation method of the olefin-rich mixed drilling fluid base oil according to the present application, wherein preferably, the drilling fluid base oil has linear terminal olefins and internal olefins with 10-28 carbons, and linear alkanes and isomeric alkanes with 10-28 carbons, and the total mass content of the linear terminal olefins and internal olefins in the drilling fluid base oil is greater than or equal to 60%.

[0022] The preparation method of the olefin-rich mixed drilling fluid base oil according to the present application, wherein preferably, the drilling fluid base oil has linear terminal olefins and internal olefins with 12-24 carbons, and linear alkanes and isomeric alkanes with 12-24 carbons, and the total mass content of the linear terminal olefins and internal olefins in the drilling fluid base oil is greater than or equal to 60%, the mass content of linear alkanes is not less than 10%, and the mass content of isomeric alkanes is not less than 10%.

[0023] The preparation method of the olefin-rich mixed drilling fluid base oil according to the present application, wherein preferably, the drilling fluid base oil has an oxygen mass content of not more than 1%, an initial boiling point of 150-250°C, and a final boiling point of 300-400°C.

[0024] Specifically, since it is difficult to avoid the generation of alcohol, ether, ketone, acid, ester and other oxygen-containing compounds in the Fischer-Tropsch synthesis reaction of CO and H2, the content of oxygen-containing compounds in high-temperature Fischer-Tropsch oil accounts for more than 10%. The presence of oxygen-containing compounds can aggravate the taste of oil products, and can easily have a stimulating odor during use, and can also affect the light and heat stability of the product. In addition, especially the acidic oxygen-containing compounds seriously corrode the processing equipment and affect the safety during use. Therefore, the oxygen-containing compounds need to be removed before the next processing process. However, the high-temperature Fischer-Tropsch synthesis oil contains a large amount of olefins, and the conventional hydrofining method will inevitably saturate the olefins while removing the oxygen-containing compounds, so it is not suitable. The present application recommends a method for removing oxygen-containing compounds by non-hydrogenation means. The relatively effective treatment measures include solvent extraction method, physical adsorption method and chemical removal method. The present application does not limit the method for removing oxygen-containing compounds, as long as the mass percentage of oxygen in the oil product after deoxidation treatment is not more than 1.0%, and the olefins are not saturated.

[0025] Specifically, the distillation distribution of the drilling fluid base oil determines the level of physical property parameters. Generally, the larger the molecular weight of the oil product, the higher the carbon number, the flash point, the pour point, the density and the viscosity all show an increasing trend. The flash point is mainly related to the initial boiling point, and the higher the initial boiling point, the larger the flash point. The pour point is mainly related to the final boiling point, and the higher the final boiling point, the higher the pour point. Since the carbon number distribution of the Fischer-Tropsch synthesis oil is in a normal distribution shape and the distribution range is wide, it is necessary to remove the light and heavy components to obtain a relatively concentrated carbon number distribution, so that the product index can be controlled. The carbon number concentration in the present application is mainly solved by distillation cutting. The light and heavy components are separated by using the boiling point difference between different fractions. The separation process mainly controls the initial boiling point and the final boiling point of the oil product. After separation, the initial boiling point range of the obtained oil product is controlled to be 150-250℃, and the final boiling point range is controlled to be 300-400℃.

[0026] The preparation method of the olefin-rich mixed drilling fluid base oil provided by the present application, wherein preferably, the non-hydrogenation treatment step is: subjecting the high-temperature Fischer-Tropsch synthesis oil to primary fraction cutting to obtain primary fraction cutting oil, then performing deoxidation treatment, the mass content of oxygen in the primary fraction cutting oil after deoxidation is not higher than 1.5%, then performing secondary fraction cutting to obtain secondary fraction cutting oil, i.e. the base oil; the initial boiling points of the primary fraction cutting oil and the secondary fraction cutting oil are independently 150-250℃, and the final boiling points are independently 300-400℃.

[0027] The preparation method of the olefin-rich mixed drilling fluid base oil provided by the present application, wherein preferably, the initial boiling point cutting in the primary fraction cutting and the secondary fraction cutting is independently normal pressure distillation, and the final boiling point cutting is independently vacuum distillation. The vacuum distillation adopts a distillation column with a column top pressure of 10-50mmHg and a theoretical tray number of not less than 15.

[0028] The preparation method of the olefin-rich mixed drilling fluid base oil, wherein preferably, a cutting temperature is increased when the secondary fraction is cut, the obtained secondary fraction cutting oil is divided into a light fraction and a heavy fraction, and the light fraction and the heavy fraction are compounded to adjust the carbon number distribution.

[0029] The preparation method of the olefin-rich mixed drilling fluid base oil, wherein preferably, the cutting temperature is 240-280℃, and the compounding ratio of the light fraction and the heavy fraction is 1:1-3.

[0030] The preparation method of the olefin-rich mixed drilling fluid base oil, wherein preferably, the initial boiling point of the primary fraction cutting oil is 170-200℃, and the final boiling point is 350-400℃.

[0031] The preparation method of the olefin-rich mixed drilling fluid base oil, wherein preferably, the initial boiling point of the secondary fraction cutting oil is 170-200℃, and the final boiling point is 350-400℃.

[0032] The preparation method of the olefin-rich mixed drilling fluid base oil, wherein preferably, the deoxygenation treatment comprises at least one of a solvent extraction method, a physical adsorption method and a chemical removal method.

[0033] Specifically, the solvent extraction is also called liquid-liquid extraction, which is used to separate a mixture by using the different solubilities of components in solvents. The oxygen-containing compound is a polar compound, the extractant is a strong polar solvent, and the oxygen-containing compound can be separated and removed from the hydrocarbon with smaller polarity, so as to achieve the purpose of separation and purification. The physical adsorption method mainly removes the oxygen-containing compound in the olefin by using the polarity difference between the hydrocarbon and the oxygen-containing compound. The oxygen-containing compound is a polar compound, while the hydrocarbon molecule is a non-polar or weakly polar compound, and the adsorbent is used to selectively adsorb and remove the oxygen-containing compound due to the different polarity of the oxygen-containing compound. Common solid adsorbents mainly include silica gel, alumina, activated carbon, aluminum silicate, cation exchange resin, molecular sieve, zeolite, natural or modified clay and the like. The chemical removal method mainly forms a complex by using a removing agent (sodium hydroxide, potassium hydroxide and potassium carbonate solution) and an organic acid, and then removes the oxygen-containing compound in the olefin by water washing. The organic acid (naphthenic acid) can be removed by alkali washing through acid-base neutralization.

[0034] The preparation method of the olefin-rich mixed drilling fluid base oil, wherein preferably, the sulfur content of the drilling fluid base oil is less than 1 ppm, the nitrogen content is less than 1 ppm, the flash point is higher than 80℃, the pour point is lower than -30℃, the kinematic viscosity at 40℃ is less than 2 mm 2 / s.

[0035] Specifically, the key property parameters of the drilling fluid base oil include flash point, pour point, density, kinematic viscosity, etc., and the high or low property parameter index has an important influence on the performance and safety of the base oil. In the drilling process, the drilling fluid needs to maintain good rheological property, and the viscosity needs to be maintained in a moderate range. The higher the viscosity, the worse the rheological property, and pressure fluctuation is prone to occur, circulation pressure consumption is large, drilling speed is reduced, and sticking is prone to occur. The drilling fluid is also not easy to maintain. If the viscosity is too low, the carrying and suspending capacity is poor, the well flushing effect is poor, and sticking is prone to occur due to the settlement of barite and drill cuttings. The pour point mainly affects the use of the drilling fluid in a low-temperature environment, and the lower the pour point, the wider the applicable range. The flash point mainly affects the safety during use. In the drilling process, the temperature is increased by about 4℃ when going down 100m. For some ultra-deep wells, the temperature is even above 200℃. If the flash point is too low, oil burning and explosion are prone to occur in the construction project, and safety accidents occur. Therefore, the flash point should be as high as possible. The drilling fluid needs to have a certain density in the drilling process, the hydrostatic pressure of the drilling fluid in the well is adjusted, the well wall is maintained stable, and usually barite is added for adjustment. However, increasing the density of the base oil can reduce the amount of barite, and avoid the precipitation caused by too much barite. The drilling fluid base oil obtained by the method has no sulfur and nitrogen impurities, high flash point, low pour point, and small viscosity, and has the advantages of high safety and good low-temperature rheological property.

[0036] The preparation method of the olefin-rich mixed drilling fluid base oil provided by the application specifically comprises the following steps: subjecting raw high-temperature Fischer-Tropsch synthetic oil to primary distillation cutting through a distillation column to obtain oil products with an initial boiling point of 150-250℃ and a final boiling point of 300-400℃, subjecting the obtained distillate oil to deoxygenation treatment with an oxygen mass content of not higher than 1.5%, and subjecting the deoxygenated distillate oil to secondary distillation cutting through a distillation column to obtain oil products with an oxygen mass content of not higher than 1%, an initial boiling point of 150-250℃, and a final boiling point of 300-400℃.

[0037] The drilling fluid base oil obtained by the method has no sulfur and nitrogen impurities, high flash point, low pour point, and small viscosity, and has the advantages of high safety and good low-temperature rheological property.

[0038] (1) The preparation method of the olefin-rich mixed drilling fluid base oil provided by the application fully utilizes the composition characteristics of high-temperature Fischer-Tropsch synthetic oil, takes into account the performance advantages of olefin and alkane base drilling fluid base oil, avoids the high-energy-consumption and high-cost processing and treatment process such as hydrogenation isomerization in the process of producing alkane base drilling fluid from low-temperature Fischer-Tropsch synthetic oil, the processing process is mild and controllable, and the processing and preparation process is simple; the obtained base oil has low viscosity, which is conducive to improving the actual drilling speed, the performance index can be flexibly adjusted, and the product has a wide range of applications.

[0039] (2) The drilling fluid base oil provided by the application has no sulfur and nitrogen impurities, high flash point, low pour point, and small viscosity, and has the advantages of high safety and good low-temperature rheological property. DETAILED DESCRIPTION

[0040] The following detailed description of the embodiments of the present application is given on the premise of the technical solutions of the present application, and detailed implementation manners and processes are given, but the protection scope of the present application is not limited to the following embodiments. The experimental methods not specified in the following embodiments are usually performed according to the conventional conditions, and the % not specified is the mass %.

[0041] The present application provides a preparation method of an olefin-rich mixed drilling fluid base oil, comprising the following steps: subjecting a high-temperature Fischer-Tropsch synthesis oil to non-hydrogen treatment to obtain a drilling fluid base oil, wherein the high-temperature Fischer-Tropsch synthesis oil is a product obtained by synthesizing low-carbon alkanes and olefins at 280-420 ℃, preferably 300-350 ℃, by Fischer-Tropsch synthesis, and the non-hydrogen treatment comprises at least one fraction cutting and at least one deoxygenation treatment.

[0042] Specifically, the order of fraction cutting and deoxygenation treatment in the preparation method of the present application is not limited, and fraction cutting can be performed first, or deoxygenation treatment can be performed first.

[0043] In some embodiments, preferably, the drilling fluid base oil has linear terminal olefins and internal olefins with 10-28 carbons and linear alkanes and isomeric alkanes with 10-28 carbons, and the total mass content of the linear terminal olefins and internal olefins in the drilling fluid base oil is greater than or equal to 60%.

[0044] In some embodiments, preferably, the drilling fluid base oil has linear terminal olefins and internal olefins with 12-24 carbons and linear alkanes and isomeric alkanes with 12-24 carbons, and the total mass content of the linear terminal olefins and internal olefins in the drilling fluid base oil is greater than or equal to 60%, the mass content of linear alkanes is not less than 10%, and the mass content of isomeric alkanes is not less than 10%.

[0045] In some embodiments, preferably, the drilling fluid base oil has an oxygen mass content of not more than 1%, an initial boiling point of 150-250 ℃, and a final boiling point of 300-400 ℃.

[0046] Specifically, since it is difficult to avoid the generation of alcohol, ether, ketone, acid, ester and other oxygen-containing compounds in the Fischer-Tropsch synthesis reaction of CO and H2, the content of oxygen-containing compounds in high-temperature Fischer-Tropsch oil accounts for more than 10%. The presence of oxygen-containing compounds can aggravate the taste of oil products, and can easily have a stimulating odor during use, and can also affect the light and heat stability of the product. In addition, especially the acidic oxygen-containing compounds seriously corrode the processing equipment and affect the safety during use. Therefore, the oxygen-containing compounds need to be removed before the next processing process. However, the high-temperature Fischer-Tropsch synthesis oil contains a large amount of olefins, and the conventional hydrofining method will inevitably saturate the olefins while removing the oxygen-containing compounds, so it is not very suitable. The present application recommends a method for removing oxygen-containing compounds by non-hydrogen method. The relatively effective treatment measures include solvent extraction method, physical adsorption method and chemical removal method. The present application does not limit the method for removing oxygen-containing compounds, as long as the mass percentage of oxygen in the oil product after deoxidation treatment is not more than 1.0%, and the olefins are not saturated.

[0047] Specifically, the distillation distribution of the drilling fluid base oil has a decisive effect on the level of physical property parameters. Generally speaking, the larger the molecular weight of the oil product and the higher the carbon number, the greater the flash point, pour point, density and viscosity. In addition, the flash point is mainly related to the initial boiling point, and the higher the initial boiling point, the greater the flash point. The pour point is mainly related to the final boiling point, and the higher the final boiling point, the higher the pour point. Since the carbon number distribution of the Fischer-Tropsch synthesis oil is in a normal distribution shape and the distribution range is wide, it is necessary to remove the too light components and the too heavy components to obtain a relatively concentrated carbon number distribution so that the product index can be controlled. The carbon number concentration of the present application is mainly solved by distillation cutting. The light and heavy components are separated by using the boiling point difference between different fractions. The separation process mainly controls the initial boiling point and the final boiling point of the oil product. After separation, the initial boiling point range of the obtained oil product is controlled to be 150-250℃, and the final boiling point range is controlled to be 300-400℃.

[0048] In some embodiments, preferably, the non-hydrogen treatment step is: subjecting the high-temperature Fischer-Tropsch synthesis oil to primary fraction cutting to obtain a primary fraction cut oil, then performing deoxidation treatment, the mass content of oxygen in the primary fraction cut oil after deoxidation is not higher than 1.5%, and then performing secondary fraction cutting to obtain a secondary fraction cut oil, i.e. a base oil; the initial boiling points of the primary fraction cut oil and the secondary fraction cut oil are independently 150-250℃, and the final boiling points are independently 300-400℃.

[0049] In some embodiments, preferably, the initial boiling point cutting in the primary fraction cutting and the secondary fraction cutting is independently atmospheric distillation, and the final boiling point cutting is independently vacuum distillation. The overhead pressure of the distillation column used in the vacuum distillation is 10-50mmHg, and the theoretical plate number of the distillation column is not less than 15.

[0050] In some embodiments, it is preferred that the secondary fraction cutting is increased by one cutting temperature, and the obtained secondary fraction cutting oil is divided into a light fraction and a heavy fraction, and the light fraction and the heavy fraction are recombined to adjust the carbon number distribution.

[0051] In some embodiments, it is preferred that the cutting temperature is 240-280°C, and the recombination ratio of the light fraction and the heavy fraction is 1:1-3.

[0052] In some embodiments, it is preferred that the initial boiling point of the primary fraction cutting oil is 170-200°C, and the final boiling point is 350-400°C.

[0053] In some embodiments, it is preferred that the initial boiling point of the secondary fraction cutting oil is 170-200°C, and the final boiling point is 350-400°C.

[0054] In some embodiments, it is preferred that the deoxygenation treatment includes at least one of a solvent extraction method, a physical adsorption method, and a chemical removal method.

[0055] Specifically, solvent extraction, also known as liquid-liquid extraction, is a method for separating mixtures by taking advantage of the different solubilities of components in solvents. Oxygen-containing compounds are polar compounds, and the extractant is a strong polar solvent, which can separate and remove oxygen-containing compounds from hydrocarbons with smaller polarity, thereby achieving the purpose of separation and purification. The physical adsorption method mainly uses the difference in polarity between hydrocarbons and oxygen-containing compounds to remove oxygen-containing compounds in olefins. Oxygen-containing compounds are polar compounds, while hydrocarbon molecules are non-polar or weakly polar compounds. By using adsorbents with different selectivity for the polarity of oxygen-containing compounds, the oxygen-containing compounds can be adsorbed and removed. Common solid adsorbents include silica gel, alumina, activated carbon, aluminum silicate, cation exchange resin, molecular sieve, zeolite, natural or modified clay, etc. The chemical removal method mainly forms a complex of a removing agent (sodium hydroxide, potassium hydroxide, and potassium carbonate solution) and an organic acid, and then removes the oxygen-containing compounds in the olefins by water washing. The organic acid (naphthenic acid) can be removed by alkali washing through acid-base neutralization.

[0056] In some embodiments, it is preferred that the sulfur content of the drilling fluid base oil is less than 1 ppm, the nitrogen content is less than 1 ppm, the flash point is higher than 80°C, the pour point is lower than -30°C, the kinematic viscosity at 40°C is less than 2 mm 2 / s.

[0057] Specifically, the key property parameters of the drilling fluid base oil include flash point, pour point, density, kinematic viscosity, etc., and the high or low property parameter index has an important influence on the performance and safety of the base oil. In the drilling process, the drilling fluid needs to maintain good rheological property, and the viscosity needs to be maintained in a moderate range. The higher the viscosity, the worse the rheological property, and pressure fluctuation is easy to occur, circulation pressure consumption is large, drilling speed is reduced, and sticking is easy to occur, and the drilling fluid is not easy to maintain; the viscosity is too low, the carrying and suspending capacity is poor, the well flushing effect is poor, and sticking is easy to occur due to barite and drill cuttings settlement. The pour point mainly affects the use of the drilling fluid in a low-temperature environment, and the lower the pour point, the wider the applicable range. The flash point mainly affects the safety during use. In the drilling process, the temperature is increased by about 4℃ when diving 100m, and for some ultra-deep wells, the temperature is even above 200℃. The flash point is too low to cause oil combustion, explosion and other accidents in the construction project, and safety accidents occur, so the flash point should be as high as possible. The drilling fluid needs to have a certain density in the drilling process, the hydrostatic pressure of the drilling fluid in the well is adjusted, the well wall is maintained stable, and usually the barite is added for adjustment, and the increase of the density of the base oil can reduce the amount of barite, and avoid the precipitation caused by too much barite. The drilling fluid base oil obtained by the method has the advantages of high safety, good low-temperature rheological property, no sulfur and nitrogen impurities, high flash point, low pour point and small viscosity.

[0058] Test method

[0059] In the present application, the base oil composition is determined by a gas chromatograph-time of flight mass spectrometer of Japan Electronic, the oxygen element mass content is determined by an EA 2400 instrument of PerkinElmer Company, the closed flash point is determined by GB / T 261-2008, the pour point is determined by GB / T 3535-2006, and the kinematic viscosity is determined by GB / 30515-2014.

[0060] Source of raw materials and reagents

[0061] Silica-magnesia type adsorbent, Shanghai Chemical Reagent Co., Ltd., FCP 60-100 mesh.

[0062] Example 1:

[0063] A high-temperature Fischer-Tropsch slurry reactor was operated at a temperature of 320°C and a pressure of 3 MPa using a synthesis gas with a H2 / CO ratio of 2:1 as the raw material. The product from the reactor outlet, i.e., high-temperature Fischer-Tropsch oil, was collected and added to a 5L rectifying column for a first fraction cut. The rectifying column had 25 theoretical plates, and atmospheric distillation was used to remove the fraction with a boiling point less than 170°C. Then, the vacuum degree was controlled at 50 mmHg to remove the fraction with a boiling point greater than 320°C, and a first cut fraction oil with an initial boiling point of 170°C and a final boiling point of 320°C was obtained. The first cut fraction oil was subjected to deoxygenation treatment using a silicon-magnesium adsorbent under the following conditions: a temperature of 25°C, a pressure of 0.1 MPa, and a volume ratio of the fraction oil to the silicon-magnesium adsorbent of 400:1. The oxygen content of the deoxygenated fraction oil was 0.42 wt%. The deoxygenated first cut fraction oil was again subjected to a second fraction cut in the rectifying column under the same conditions as the first fraction cut, and the fraction cut temperature was controlled to obtain a second cut fraction oil with an initial boiling point of 170°C and a final boiling point of 320°C, i.e., a rich-olefin-mixture drilling fluid base oil. The total mass content of linear terminal olefins and internal olefins with 12-24 carbons in the obtained base oil was 64.3%, the mass content of linear alkanes was 14.2%, and the mass content of isomeric alkanes was 16.4%. The physical property indexes of the drilling fluid base oil are shown in Table 1.

[0064] Example 2:

[0065] A high-temperature Fischer-Tropsch synthesis slurry reactor was operated at a temperature of 320°C and a pressure of 3 MPa using a synthesis gas with a H2 / CO ratio of 2:1 as the raw material. The product at the outlet of the reactor was collected and fed into a 5 L rectifying column for primary fraction cutting. The rectifying column had 25 theoretical plates. The fraction with a boiling point less than 200°C was removed by atmospheric distillation, and then the vacuum degree was controlled at 50 mmHg to remove the fraction with a boiling point higher than 310°C, thus obtaining an oil product with an initial boiling point of 200°C and a final boiling point of 310°C. The obtained fraction oil was subjected to deoxygenation treatment by a chemical method. The treatment conditions were as follows: the fraction oil was fed into a three-neck flask with a mechanical stirring device, and an aqueous solution of methanol and sodium hydroxide was prepared (preparation method: 10% methanol aqueous solution and 25% sodium hydroxide aqueous solution were prepared according to a volume ratio of 1:3), and the mass of the aqueous solution of methanol and sodium hydroxide was the same as that of the fraction oil. The solution was stirred at a speed of 800 r / min for 4 h, and then the upper oil phase was taken out and fed into a new three-neck flask. An equal mass of desalted water was added, and the solution was stirred for a certain period of time, and then the solution was allowed to separate into two layers. The upper layer was the fraction oil after deoxygenation and purification. The oxygen content of the fraction oil after deoxygenation was 0.32 wt%. The fraction oil after deoxygenation was subjected to secondary fraction cutting by a rectifying column under the same conditions as those of the primary fraction cutting. The fraction cutting temperature was controlled, thus obtaining an oil product with an initial boiling point of 200°C and a final boiling point of 310°C, which was a rich-olefin-mixed drilling fluid base oil. The total mass content of linear terminal olefins and internal olefins with carbon numbers of 12-24 in the obtained base oil was 66.2%, the mass content of linear alkanes was 13.6%, and the mass content of isomeric alkanes was 15.3%. The physical property indexes of the drilling fluid base oil are shown in Table 1.

[0066] Example 3:

[0067] A high temperature Fischer-Tropsch synthesis slurry bed reactor was used, with a synthesis gas having a H2 / CO ratio of 2:1 as the raw material, the reactor operating temperature was 320°C, the reaction pressure was 3 MPa, the product at the reactor outlet was collected, the oil was added to the 5L distillation column to cut the first fraction, the distillation column had 25 theoretical plates, atmospheric distillation was used to remove the fraction less than 190°C, then the vacuum was controlled at 20 mmHg to remove the fraction greater than 350°C, an oil having an initial boiling point of 190°C and a final boiling point of 350°C was obtained. The fraction oil was treated by solvent extraction distillation to remove the oxygen-containing compounds, a 95% methanol aqueous solution was used as the extractant, the fraction oil was repeatedly extracted to remove the oxygen-containing compounds, the oxygen content of the fraction oil after the deoxygenation was 0.46 wt%. The fraction oil after the deoxygenation was again cut by the distillation column to cut the second fraction, the cutting conditions were the same as the first cutting, the fraction cutting temperature was controlled, an oil having an initial boiling point of 190°C and a final boiling point of 350°C was obtained, which was the rich olefin mixed drilling fluid base oil. The total mass content of the linear terminal olefins and internal olefins having 12-24 carbons in the obtained base oil was 73.6%, the mass content of the linear alkanes was 10.1%, and the mass content of the isomeric alkanes was 12.2%. The drilling fluid base oil physical property indexes are shown in Table 1.

[0068] Example 4

[0069] A high temperature Fischer-Tropsch synthesis slurry bed reactor was used, with a synthesis gas having a H2 / CO ratio of 2:1 as the raw material, the reactor operating temperature was 320°C, the reaction pressure was 3 MPa, the product at the reactor outlet was collected, the oil was added to the 5L distillation column to cut the first fraction, the distillation column had 25 theoretical plates, atmospheric distillation was used to remove the fraction less than 170°C, then the vacuum was controlled at 20 mmHg to remove the fraction greater than 350°C, an oil having an initial boiling point of 170°C and a final boiling point of 350°C was obtained. The fraction oil was treated by a silicon-magnesium type adsorbent to remove the oxygen-containing compounds, the treatment conditions were: a temperature of 25°C, a pressure of 0.1 MPa, and a volume ratio of the fraction oil to the silicon-magnesium type adsorbent of 400:1, the oxygen content of the fraction oil after the deoxygenation was 0.47 wt%. The fraction oil after the deoxygenation was again cut by the distillation column to cut the second fraction, the cutting conditions were the same as the first cutting, the fraction cutting temperature was controlled, an oil having an initial boiling point of 170°C and a final boiling point of 330°C was obtained. During the second fraction cutting, a fraction cutting point of 260°C was added, an oil having a boiling range of 170-260°C and an oil having a boiling range of 260-330°C were obtained, the two oils were mixed in a ratio of 1:1, which was the rich olefin mixed drilling fluid base oil. The mass content of the linear terminal olefins and internal olefins having 12-24 carbons in the obtained base oil was 68.3%, the mass content of the linear alkanes was 13.2%, and the mass content of the isomeric alkanes was 14.4%. The drilling fluid base oil physical property indexes are shown in Table 1.

[0070] Example 5

[0071] A high temperature Fischer-Tropsch synthesis slurry reactor, with a synthesis gas of H2 / CO ratio of 2:1 as raw material, the device operating temperature of 320℃, the reaction pressure of 3MPa, the reactor outlet product was collected, the oil was added to the 5L rectifying column for the first cut, the rectifying column theoretical plate number was 25, the less than 170℃ fraction was removed by atmospheric distillation, then the vacuum degree was controlled at 20mmHg, the fraction greater than 350℃ was removed, the first cut oil with the initial boiling point of 170℃ and the final boiling point of 350℃ was obtained. The obtained first cut oil was treated by chemical removal method, the treatment conditions were as follows: the fraction oil was added to a three-necked flask with mechanical stirring device, the aqueous solution prepared by adding methanol and sodium hydroxide (preparation method: 10% methanol aqueous solution and 25% sodium hydroxide aqueous solution were prepared according to the volume ratio of 1:3) was added, the mass of the aqueous solution prepared by adding methanol and sodium hydroxide was the same as that of the fraction oil, the stirring was carried out at the speed of 800r / min for 4h, after the solution was stratified, the upper oil phase was taken to a new three-necked flask, the same mass of desalted water was added, after a certain time of stirring, the solution was stratified, the upper layer was the fraction oil after deoxygenation and refining, the oxygen content of the fraction oil after deoxygenation was 0.5wt%. The fraction oil after deoxygenation was subjected to secondary cut by the rectifying column, the cut conditions were the same as those of the first cut, the cut temperature was controlled, the oil with the initial boiling point of 180℃ and the final boiling point of 340℃ was obtained. In the secondary cut, a cut point of 250℃ was added, the oil with the boiling range of 180-250℃ and the oil with the boiling range of 250-340℃ were obtained, the two kinds of oil were mixed according to the ratio of 1:2, which was the rich olefin mixed drilling fluid base oil. The total mass content of 12-24 carbon straight chain terminal olefins and internal olefins in the obtained base oil was 67.2%, the mass content of straight chain alkanes was 13.8%, and the mass content of isomeric alkanes was 15.9%. The drilling fluid base oil physical property indexes were shown in Table 1.

[0072] Comparative Example 1

[0073] A low temperature Fischer-Tropsch synthesis fixed bed reactor, with a synthesis gas of H2 / CO ratio of 2:1 as raw material, the device operating temperature of 220℃, the reaction pressure of 2.5MPa, the reactor outlet product was collected, the product was first subjected to hydroisomerization treatment under the process conditions of reaction temperature of 320℃, pressure of 7MPa, space velocity of 2h -1 -1, hydrogen to oil ratio of 500:1, the catalyst used was PIC-812 hydroisomerization catalyst of PetroChina. Then the product was subjected to cut by a rectifying column, the rectifying column theoretical plate number was 25, the less than 200℃ fraction was removed by atmospheric distillation, then the vacuum degree was controlled at 20mmHg, the fraction greater than 330℃ was removed, the initial boiling point was controlled at 200℃, the final boiling point was controlled at 330℃, finally the alkanes type drilling fluid base oil with the isomeric alkanes content of 80wt% was obtained.

[0074] Table 1 Drilling fluid base oil physical property indexes

[0075]

[0076]

[0077] As shown in Table 1, the preparation method of the olefin-rich mixed drilling fluid base oil provided by each embodiment of the present application fully utilizes the composition characteristics of high-temperature Fischer-Tropsch synthetic oil, takes into account the performance advantages of olefin and alkane-based drilling fluid base oil, avoids the high-energy and high-cost processing and treatment process such as hydrogenation isomerization in the process of producing alkane-based drilling fluid from low-temperature Fischer-Tropsch synthetic oil, and has a mild and controllable processing process and a simple preparation process. The obtained base oil has low viscosity, is conducive to improving the actual drilling speed, has flexible performance indicators, and has a wide application range.

[0078] As shown in Table 1, the olefin-rich mixed drilling fluid base oil provided by each embodiment of the present application has no sulfur and nitrogen impurities, has high flash point, low pour point and low viscosity, and has the advantages of high safety and good low-temperature rheological property.

[0079] Of course, the present application can have other various embodiments, and those skilled in the art can make various corresponding changes and modifications according to the present application without departing from the spirit and essence of the present application. However, these corresponding changes and modifications should all belong to the protection scope of the present application.

Claims

1. A method for preparing an olefin-rich mixed drilling fluid base oil, characterized in that, Includes the following steps: Drilling fluid base oil is obtained by non-hydrogenation treatment of high-temperature Fischer-Tropsch synthetic oil. The high-temperature Fischer-Tropsch synthetic oil is a product obtained by Fischer-Tropsch synthesis of low-carbon alkanes and olefins at 280-420℃. The non-hydrogenation treatment steps are as follows: the high-temperature Fischer-Tropsch synthetic oil is subjected to primary fractionation to obtain primary fractionated oil, and then subjected to deoxygenation treatment. The oxygen content of the deoxygenated primary fractionated oil is not higher than 1.5% by mass. Then, it is subjected to secondary fractionation to obtain secondary fractionated oil, i.e., base oil, and the oxygen content of the base oil is not higher than 1% by mass. The drilling fluid base oil has 10-28 carbon straight-chain terminal olefins and internal olefins, as well as 10-28 carbon straight-chain alkanes and isoalkanes, and the total mass content of the straight-chain terminal olefins and internal olefins in the drilling fluid base oil is greater than or equal to 60%, the mass content of straight-chain alkanes is not less than 10%, and the mass content of isoalkanes is not less than 10%.

2. The preparation method according to claim 1, characterized in that, The drilling fluid base oil has 12-24 carbon straight-chain terminal olefins and internal olefins, as well as 12-24 carbon straight-chain alkanes and isoalkanes, and the total mass content of the straight-chain terminal olefins and internal olefins in the drilling fluid base oil is greater than or equal to 60%.

3. The preparation method according to claim 1, characterized in that, The initial boiling point of the primary distillate cut oil and the secondary distillate cut oil are independently 150~250℃, and the final boiling point is independently 300~400℃.

4. The preparation method according to claim 3, characterized in that, The initial distillation point cut in the primary fraction cut and the secondary distillation point cut are each independently atmospheric distillation, and the final distillation point cut are each independently vacuum distillation. The top pressure of the distillation column used for vacuum distillation is 10~50 mmHg, and the theoretical number of the distillation column is not less than 15.

5. The preparation method according to claim 3 or 4, characterized in that, The secondary fraction cutting process involves adding a cutting temperature to separate the resulting secondary fraction oil into light and heavy fractions. The light and heavy fractions are then blended to adjust the carbon number distribution.

6. The preparation method according to claim 5, characterized in that, The cutting temperature is 240~280℃, and the blending ratio of light fraction to heavy fraction is 1:1~3.

7. The preparation method according to claim 3, characterized in that, The initial boiling point of the primary distillate cut oil is 170~200℃, and the final boiling point is 350~400℃; the initial boiling point of the secondary distillate cut oil is 170~200℃, and the final boiling point is 350~400℃.

8. The preparation method according to claim 1, characterized in that, The deoxygenation treatment includes at least one of solvent extraction, physical adsorption, and chemical removal.

9. The preparation method according to claim 1, characterized in that, The drilling fluid base oil has an initial boiling point of 150-250℃ and a final boiling point of 300-400℃.

10. The preparation method according to claim 1, characterized in that, The drilling fluid base oil has a sulfur content of less than 1 ppm, a nitrogen content of less than 1 ppm, a flash point of higher than 80°C, a pour point of lower than -30°C, and a kinematic viscosity of less than 2 mm at 40°C. 2 / s.

11. The preparation method according to claim 1, characterized in that, The high-temperature Fischer-Tropsch synthetic oil is a product obtained by synthesizing low-carbon alkanes and olefins through Fischer-Tropsch synthesis at 300~350℃.

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