Olefins-rich mixed drilling fluid base oil and its preparation method

Abstract

The present application relates to a kind of drilling fluid base oil of olefin-rich mixed type, which is obtained by distillation treatment and deoxygenation treatment from raw material high-temperature Fischer-Tropsch synthetic oil.The initial boiling point of the drilling fluid base oil is 150-250℃, the final boiling point is 300-400℃, it has 10-28 carbon straight-chain terminal olefins and internal olefins, and 10-28 carbon straight-chain alkanes and isomeric alkanes, and the total mass content of the straight-chain terminal olefins and internal olefins in the drilling fluid base oil is not less than 60%;The sulfur and nitrogen content of the drilling fluid base oil is less than 1 ppm, the flash point is not less than 80℃, the pour point is not higher than-30℃, the kinematic viscosity at 40℃ is not more than 2mm 2 / s.The drilling fluid prepared using the drilling fluid base oil provided by the present application has the advantages of low viscosity, high demulsification voltage, low high-temperature high-pressure filtration loss, etc.The present application also relates to a preparation method of the drilling fluid base oil of olefin-rich mixed type.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of synthetic base drilling fluid base oil, and particularly relates to a rich olefin mixed drilling fluid base oil derived from high-temperature Fischer-Tropsch synthetic oil and a preparation method thereof. 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, etc.

[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, etc. Among them, the base fluid occupies the largest volume. According to the type of base fluid, it can be divided into two categories: 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, etc. It has become an important means for drilling high-difficulty high-temperature deep wells, offshore drilling, high-inclination directional wells, horizontal wells, complex process wells and reservoir protection. However, traditional white oil and mineral oil have poor biodegradability and can easily affect the environment. In addition, the rheological properties of drilling fluid systems prepared with diesel oil and white oil as the base are still unstable, and sometimes the apparent viscosity increases sharply under low temperature conditions, which leads to excessive circulating pump pressure and seriously affects the normal operation of drilling operations. Therefore, biodegradable and rheologically good synthetic base drilling fluid has gradually attracted attention.

[0004] Synthetic base drilling fluid, also known as imitation oil-based drilling fluid, is a non-water-soluble synthetic oil-based drilling fluid with the operating performance of oil-based drilling fluid. Its composition is basically the same as that of oil-based drilling fluid. The fractions contained in synthetic base drilling fluid are basically free of aromatic compounds and are basically non-toxic to mammals. After field use, it can meet the discharge requirements. At present, it has been applied in more than 800 wells around the world, which are located in the Gulf of Mexico, the North Sea, the Far East, the European continent, South America, Australia, Mexico and Russia, etc. Among them, the Gulf of Mexico and the North Sea account for 90%.

[0005] Different products have been applied internationally since the 1990s. 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, Novadrill system of M-I Company, etc.

[0006] The first generation of synthetic base drilling fluids are represented by ester, ether, poly-α-olefin, acetal, etc. The second generation of synthetic base drilling fluids are represented by linear α-olefin, internal olefin, linear alkyl benzene, linear paraffin.

[0007] Ester is the first generation of synthetic material used for preparing drilling fluids. In March 1990, drilling with ester base drilling fluid was successful in Norway. Inspired by the ester base drilling fluid, ether base drilling fluid was developed in 1991. In May and June 1992, ether base drilling fluid was used in offshore oil fields in Norway and the Gulf of Mexico, 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 rarely used. In the following three years (1993-1995), researchers of foreign drilling fluids developed the second generation of synthetic materials represented by linear alkyl benzene (LAB), linear paraffin (LP), linear olefin, etc. Their drilling fluid systems were rapidly and widely used in the North Sea of the United Kingdom and the Gulf of Mexico. With the development of coal-to-oil industry, Fischer-Tropsch synthetic oil has certain environmental advantages due to its lack of sulfur and nitrogen impurities, and has attracted widespread attention. Energy companies represented by Shell Company have developed synthetic base alkane drilling fluid base oil, which has been widely used.

[0008] Fischer-Tropsch synthesis is a process of synthesizing hydrocarbons, oxygen-containing compounds and water from synthesis gas containing hydrogen and carbon monoxide under certain reaction conditions of catalyst, temperature and pressure. It is widely used in coal indirect liquefaction, natural gas-to-liquid and biomass-to-liquid oil and other oil replacement technologies, which is of great significance to alleviate the dependence on oil resources for domestic energy. Fischer-Tropsch synthesis can be divided into two types according to reaction temperature and product composition. One is low-temperature Fischer-Tropsch synthesis, which generates long-chain heavy oil or Fischer-Tropsch wax at low temperature (220-250℃), and the carbon number distribution range is wide, from C4 to C60 or even C100, of which 80-90wt% are normal alkanes, and a small amount of isomeric hydrocarbons, olefins, oxygen-containing compounds and other components. The other is high-temperature Fischer-Tropsch synthesis, 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 below C20, of which the content of olefin component is more than 50wt%. The product is high-temperature Fischer-Tropsch oil.

[0009] Low-temperature Fischer-Tropsch oil is mainly composed of straight-chain alkanes, which is a good raw material for processing alkane base drilling fluid base oil. By controlling the appropriate distillation distribution, the flash point range of the product can be adjusted. The higher the boiling point, the higher the corresponding flash point. However, compared with isomeric alkanes, the pour point of straight-chain alkanes is low, so straight-chain alkane base oil cannot be directly used in some low-temperature areas and must be subjected to hydrogenation isomerization treatment. The straight-chain alkanes are converted into branched isomeric alkanes through isomerization to reduce the pour point of the oil and broaden the application range of the base oil.

[0010] CN105505347A discloses a synthetic base drilling fluid base oil, which is mixed from Fischer-Tropsch synthetic oil and non-traditional petroleum-derived fine chemical base oil, contains at least 35% by mass of a plurality of normal alkanes of 9-20 carbon atoms, contains at least 60% by mass of a plurality of branched or cyclic alkanes of 9-20 carbon atoms, and contains less than 0.5% by mass of aromatic hydrocarbons. The synthetic base drilling fluid base oil has a kinematic viscosity of 2-3 mm 2 / s at 40°C, a pour point of -10 to -30°C, and a closed-cup flash point of 50-80°C.

[0011] CN110964564A discloses a Fischer-Tropsch synthesis base drilling fluid base oil and a preparation method thereof, which comprises: 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; and the proportion of isomeric alkanes in the obtained base oil product is 60 wt%. The fractionation comprises atmospheric fractionation, and the process conditions of the atmospheric fractionation are as follows: a column top temperature of 100-120°C, a column top pressure of 0.01-0.2 MPa, and a side line extraction temperature of 170-190°C. The invention describes a processing flow for producing an alkane base drilling fluid base oil from Fischer-Tropsch synthesis products after hydrocracking isomerization treatment.

[0012] CN105713661A discloses a method for preparing a base oil from Fischer-Tropsch synthesis products, which comprises: 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% and 100% by changing the reaction conditions; c. blending the isomerization-treated and non-isomerization-treated fraction oils according to the application requirements of drilling fluids; and d. performing distillation on the blended product to remove hydrogenation isomerization by-products low-carbon hydrocarbons, and obtaining a base oil sample for performance testing and commercial application.

[0013] The above patents all use low-temperature Fischer-Tropsch synthetic oil to process and produce an alkane base drilling fluid base oil, and most of them need to go through an isomerization process. The obtained base oil is usually mainly isomeric alkanes and contains a small amount of normal alkanes. The hydrocracking or hydroisomerization process is usually a high-pressure reaction process of more than 10 MPa, 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, and the production cost is high.

[0014] 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.

[0015] 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 to 100%, preferably 60 to 100%, more preferably 70 to 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.

[0016] 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.

[0017] 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 to 35 carbon atoms of ethylene and vinylidene group, 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 bond at the fourth or higher numbered carbon atom position, and less than 50% by weight is di-substituted internal olefin with double bond at the second or third numbered carbon atom position. The present 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.

[0018] 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

[0019] Based on the above, the purpose of the present application is to provide a kind of olefin-rich mixed drilling fluid base oil derived from Fischer-Tropsch synthesis oil and its preparation method.The olefin-rich mixed drilling fluid base oil provided by the present application contains olefin and alkane components at the same time, and has the performance characteristics of both olefin-based and alkane-based drilling fluid base oils, without the need for isomerization or hydrogenation process treatment, with high olefin content, and the base oil has low viscosity, which is beneficial to improve the actual drilling rate, the performance index can be flexibly controlled, and the product has wide application range.

[0020] Therefore, the present application provides an olefin-rich mixed drilling fluid base oil, which is obtained by distillation treatment and deoxygenation treatment of raw material high-temperature Fischer-Tropsch synthesis oil, the initial boiling point of the drilling fluid base oil is 150-250 DEG C, the final boiling point is 300-400 DEG C, it has 10-28 carbon straight-chain terminal olefins and internal olefins, and 10-28 carbon straight-chain alkanes and isomeric alkanes, 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 sulfur and nitrogen content of the drilling fluid base oil is less than 1 ppm, the flash point is not less than 80 DEG C, the pour point is not higher than -30 DEG C, the kinematic viscosity at 40 DEG C is not more than 2 mm 2 / s.

[0021] Specifically, the high-temperature Fischer-Tropsch oil contains a large amount of olefins, which accounts for more than 50% of the total amount of hydrocarbons, among which α-olefins are dominant, and part of internal olefins and alkanes are also present. High-temperature Fischer-Tropsch oil is synthesized at high temperature (300-350 DEG C) from low-carbon alkanes and olefins, and the carbon number distribution of the synthesis product is relatively narrow, mainly concentrated below C20, and the content of olefin component is more than 50 wt%.

[0022] In addition, during the Fischer-Tropsch synthesis reaction of CO and H2, it is difficult to avoid the generation of oxygen-containing compounds, especially the content of oxygen-containing compounds in high-temperature Fischer-Tropsch oil can be as high as 10 wt% or more, including different types of alcohols, ethers, acids, ketones, esters, etc. The presence of oxygen-containing compounds will aggravate the taste of the oil product, and during use, it is easy to have a pungent odor, and it will also affect the light and thermal stability of the product, in addition, the presence of acidic substances will easily cause corrosion of metal such as drill pipe and equipment, affecting the safety during use, and before the next processing process, the removal of oxygen-containing compounds must be carried out. Moreover, the high-temperature Fischer-Tropsch synthesis oil contains a large amount of olefins, and the conventional hydrogenation refining means will inevitably saturate the olefins while removing the oxygen-containing compounds, so it is not very suitable. Usually, non-hydrogenation means is adopted, and relatively effective treatment measures include solvent extraction method, physical adsorption method and chemical removal method.

[0023] The olefin-rich mixed drilling fluid base oil provided by the present application, wherein preferably, the initial boiling point of the drilling fluid base oil is 170-200 DEG C, and the final boiling point is 300-350 DEG C.

[0024] The olefin-rich mixed drilling fluid base oil, 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.

[0025] The olefin-rich mixed drilling fluid base oil, wherein preferably, the mass content of the linear terminal olefins and internal olefins with 12-24 carbons in the drilling fluid base oil is greater than or equal to 60%.

[0026] The olefin-rich mixed drilling fluid base oil, wherein preferably, the mass content of the linear alkanes with 12-24 carbons in the drilling fluid base oil is not less than 10%.

[0027] The olefin-rich mixed drilling fluid base oil, wherein preferably, the mass content of the isomeric alkanes with 12-24 carbons in the drilling fluid base oil is not less than 10%.

[0028] The olefin-rich mixed drilling fluid base oil, wherein preferably, the mass content of oxygen in the drilling fluid base oil is not higher than 1.5%, preferably not higher than 1%.

[0029] 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.

[0030] The preparation method of the olefin-rich mixed drilling fluid base oil, wherein preferably, the method comprises the following steps: subjecting high-temperature Fischer-Tropsch synthesis oil to primary fraction cutting, subjecting the obtained primary cutting fraction oil to deoxygenation treatment, the mass content of oxygen being not higher than 1%, and subjecting the primary cutting fraction oil after deoxygenation to secondary fraction cutting, thereby obtaining the olefin-rich mixed drilling fluid base oil with an initial boiling point of 150-250°C, preferably 170-200°C, and a final boiling point of 300-400°C, preferably 300-350°C.

[0031] The preparation method, wherein preferably, the initial boiling point of the primary cutting fraction oil is 150-250°C, preferably 170-200°C, and the final boiling point is 300-400°C, preferably 300-350°C.

[0032] Specifically, key physical properties of drilling fluid base oils include flash point, pour point, density, and kinematic viscosity. These properties significantly impact the performance and safety of the base oil. During drilling, the drilling fluid needs to maintain good rheological properties, and its viscosity must be kept within a suitable range. Higher viscosity results in poorer rheology, leading to pressure fluctuations, high circulating pressure loss, decreased drilling speed, and a higher risk of stuck pipe. It also makes the drilling fluid difficult to maintain. Conversely, excessively low viscosity results in poor carrying and suspension capabilities, ineffective well washing, and a higher risk of barite and drill cuttings settling, causing stuck pipe. Pour point primarily affects the use of drilling fluids in low-temperature environments; a lower pour point allows for a wider range of applications. Flash point mainly affects the safety of the drilling process. During drilling, the temperature rises by about 4°C for every 100 meters of depth. For some ultra-deep wells, the temperature can even reach over 200°C. A flash point that is too low can easily cause oil combustion, explosion, or other safety accidents during drilling. Therefore, the flash point should be as high as possible. During drilling, the drilling fluid needs to have a certain density to regulate the hydrostatic pressure of the drilling fluid in the well and maintain wellbore stability. This usually requires the addition of barite for regulation. Increasing the density of the base oil can reduce the amount of barite used, avoiding excessive barite addition that could cause precipitation.

[0033] The fractional distribution of drilling fluid base oil plays a decisive role in determining its physical properties. Generally, the larger the molecular weight and the higher the carbon number of the oil, the higher the flash point, pour point, density, and viscosity tend to be. Furthermore, the flash point is mainly related to the initial boiling point; the higher the initial boiling point, the higher the flash point. The pour point is mainly related to the final boiling point; the higher the final boiling point, the higher the pour point. Since the carbon number distribution of Fischer-Tropsch synthetic oil follows a normal distribution with a wide range, it is necessary to remove excessively light and heavy components to obtain a relatively concentrated carbon number distribution, making product indicators controllable. This invention primarily addresses carbon number concentration through distillation separation, utilizing the boiling point difference between different fractions to separate light and heavy components. The separation process mainly controls the initial and final boiling points of the oil. After separation, the initial boiling point range of the oil is controlled to be 150–250℃, and the final boiling point range is controlled to be 300–400℃. Further optimize the initial distillate temperature range of the oil obtained from the cutting and separation process to 170–200℃, and the final boiling point range to 300–350℃.

[0034] The beneficial effects of this invention are as follows:

[0035] (1) The drilling fluid base oil provided by the present invention contains both olefin and alkane components, taking into account the performance characteristics of olefin-based and alkane-based drilling fluid base oils. It does not require isomerization process, and the base oil has low viscosity, which is conducive to improving the actual drilling speed. The performance indicators can be flexibly adjusted, and the product has a wide range of applications.

[0036] (2) Drilling fluids prepared using the drilling fluid base oil provided by the present invention have advantages such as low viscosity, high demulsification voltage, and low filtration loss at high temperature and high pressure. Detailed Implementation

[0037] The following detailed description of the embodiments of the present application is made 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 percentages not specified are weight percentages.

[0038] The olefin-rich mixed drilling fluid base oil provided by the present application is obtained by distillation treatment and deoxygenation treatment of raw material high-temperature Fischer-Tropsch synthetic oil. The initial boiling point of the drilling fluid base oil is 150-250°C, the final boiling point is 300-400°C, and the drilling fluid base oil has 10-28 carbon straight-chain terminal olefins and internal olefins, and 10-28 carbon straight-chain alkanes and isomeric alkanes. 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 sulfur and nitrogen content of the drilling fluid base oil is less than 1 ppm, the flash point is not less than 80°C, the pour point is not higher than -30°C, the kinematic viscosity at 40°C is not greater than 2 mm 2 / s.

[0039] Specifically, the high-temperature Fischer-Tropsch oil contains a large amount of olefins, accounting for more than 50% of the total amount of hydrocarbons, of which α-olefins are the main component, and part of internal olefins and alkanes. High-temperature Fischer-Tropsch oil is synthesized at high temperature (300-350°C) to obtain low-carbon alkanes and olefins. The carbon number distribution of the synthesis product is relatively narrow, mainly concentrated below C20, and the content of olefin component is more than 50wt%.

[0040] In addition, during the Fischer-Tropsch synthesis reaction of CO and H2, it is difficult to avoid the generation of oxygen-containing compounds, especially the content of oxygen-containing compounds in high-temperature Fischer-Tropsch oil can be as high as 10wt% or more, including different types of alcohols, ethers, acids, ketones, esters, etc. The presence of oxygen-containing compounds will aggravate the taste of the oil product, and during use, it is easy to have a pungent odor, and it will also affect the light and thermal stability of the product. In addition, the presence of acidic substances can easily cause corrosion of metal such as drill pipe and equipment, affecting the safety during use. Therefore, before the next processing process, the removal of oxygen-containing compounds must be carried out. Moreover, the high-temperature Fischer-Tropsch synthetic oil contains a large amount of olefins, and the conventional hydrogenation refining means will inevitably saturate the olefins while removing the oxygen-containing compounds, so it is not very suitable. Usually, non-hydrogenation means is adopted, and relatively effective treatment measures include solvent extraction method, physical adsorption method and chemical removal method.

[0041] In some embodiments, it is preferred that the initial boiling point of the drilling fluid base oil is 170-200°C, and the final boiling point is 300-350°C.

[0042] In some embodiments, it is preferred that the drilling fluid base oil has 12-24 carbon straight-chain terminal olefins and internal olefins, and 12-24 carbon straight-chain alkanes and isomeric alkanes.

[0043] In some embodiments, it is preferred that the mass content of linear terminal olefins and internal olefins with 12-24 carbons in the drilling fluid base oil is greater than or equal to 60%.

[0044] In some embodiments, it is preferred that the mass content of linear alkanes with 12-24 carbons in the drilling fluid base oil is not less than 10%.

[0045] In some embodiments, it is preferred that the mass content of isomeric alkanes with 12-24 carbons in the drilling fluid base oil is not less than 10%.

[0046] In some embodiments, it is preferred that the mass content of oxygen in the drilling fluid base oil is not higher than 1.5%, preferably not higher than 1%.

[0047] In some embodiments, it is preferred that the deoxygenation treatment comprises at least one of solvent extraction, physical adsorption, and chemical removal.

[0048] The present application provides a preparation method of the olefin-rich mixed drilling fluid base oil, which comprises the following steps: subjecting high-temperature Fischer-Tropsch synthesis oil to primary fraction cutting, subjecting the obtained primary cutting fraction oil to deoxygenation treatment, so that the mass content of oxygen is not higher than 1%, and subjecting the deoxygenated primary cutting fraction oil to secondary fraction cutting, thereby obtaining the olefin-rich mixed drilling fluid base oil with an initial boiling point of 150-250°C, preferably 170-200°C, and a final boiling point of 300-400°C, preferably 300-350°C.

[0049] In some embodiments, it is preferred that the initial boiling point of the primary cutting fraction oil is 150-250°C, preferably 170-200°C, and the final boiling point is 300-400°C, preferably 300-350°C.

[0050] 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 of the property parameter index has 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. If the viscosity is too low, the carrying and suspending capacity is poor, and the well flushing effect is poor, and sticking is easy 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 in the use process. In the drilling process, the temperature is increased by about 4℃ when the drilling depth is 100m. For some ultra-deep wells, the temperature is even above 200℃. If the flash point is too low, oil burning and explosion are easy to occur in the construction project, and safety accidents are easy to 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.

[0051] The distillation distribution of the drilling fluid base oil has a decisive influence on the high or low of the property parameter. Generally, the larger the molecular weight of the oil product, the higher the carbon number, and the flash point, pour point, density and 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 synthetic oil is in a normal distribution shape, the distribution range is wide, and therefore, the too light component and the too heavy component need to be removed, and a relatively concentrated carbon number distribution is obtained, so that the product index is controllable. The carbon number concentration in the application is mainly solved by the rectification cutting mode, the light and heavy components are separated by using the boiling point difference between different fractions, and the initial boiling point and the final boiling point of the oil product are mainly controlled in the separation process. 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℃. The initial fraction range of the oil product obtained by further optimizing the cutting separation is controlled to be 170-200℃, and the final boiling point range is controlled to be 300-350℃.

[0052] Test method

[0053] In the 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.

[0054] Source of raw materials and reagents

[0055] Silica-magnesium type adsorbent, China Pharmaceutical Shanghai Test, FCP 60-100 mesh.

[0056] Example 1:

[0057] 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, i.e., high-temperature Fischer-Tropsch oil, was collected, the oil was added to a 5L rectifying column for primary fraction cutting, the rectifying column had 25 theoretical plates, atmospheric distillation was used to remove the fraction less than 170°C, then the vacuum degree was controlled at 50 mmHg to remove the fraction greater than 320°C, and an oil having an initial boiling point of 170°C and a final boiling point of 320°C was obtained. The obtained fraction oil was subjected to deoxygenation treatment using a silica-magnesium type adsorbent, the treatment conditions were: temperature 25°C, pressure 0.1 MPa, the volume ratio of the fraction oil to the silica-magnesium type adsorbent was 400:1, and the oxygen content of the fraction oil after deoxygenation was 0.42wt%. The fraction oil after deoxygenation was again subjected to secondary fraction cutting by a rectifying column, the cutting conditions were the same as those of the primary fraction cutting, the fraction cutting temperature was controlled, and an oil having an initial boiling point of 170°C and a final boiling point of 320°C was obtained, i.e., a rich olefin mixture type drilling fluid base oil. The total mass content of linear terminal olefins and internal olefins having 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 drilling fluid base oil physical property indexes are shown in Table 1.

[0058] Example 2:

[0059] 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 having a H2 / CO ratio of 2:1 as the feedstock. The product from the reactor, i.e., high temperature Fischer-Tropsch oil, was collected and fed to a 5 L rectifying column for a first distillation cut. The rectifying column had 25 theoretical plates and was operated at atmospheric pressure to remove a fraction having a boiling point of less than 170°C. The column was then operated at a vacuum of 20 mm Hg to remove a fraction having a boiling point of greater than 330°C. The resulting oil had an initial boiling point of 170°C and a final boiling point of 330°C. The distillate was treated by a chemical deoxygenation process. The distillate was placed in a three-neck flask with a mechanical stirrer. An aqueous solution of methanol and sodium hydroxide was prepared by mixing 10% methanol and 25% sodium hydroxide in a volume ratio of 1:3. The amount of the aqueous solution was equal to the amount of the distillate. The solution was stirred at a speed of 800 rpm for 4 hours. The upper layer was removed and placed in a new three-neck flask. An equal amount of distilled water was added and the solution was stirred for a certain period of time. The upper layer was removed and was the deoxygenated distillate. The oxygen content of the deoxygenated distillate was 0.38 wt%. The deoxygenated distillate was again fed to a rectifying column for a second distillation cut. The distillation cut was controlled to obtain an oil having an initial boiling point of 170°C and a final boiling point of 330°C. The resulting oil was a rich olefin mixture drilling fluid base oil. The mass content of straight chain terminal olefins and internal olefins having 12-24 carbons in the base oil was 70.0%, the mass content of straight chain alkanes was 12.9%, and the mass content of isomeric alkanes was 13.1%. The physical properties of the drilling fluid base oil are shown in Table 1.

[0060] Example 3:

[0061] 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 perform a first distillation cut, the distillation column had 25 theoretical plates, atmospheric distillation was used to remove the fraction less than 200°C, then the vacuum was controlled at 20 mmHg to remove the fraction greater than 310°C, and an oil having an initial boiling point of 200°C and a final boiling point of 310°C was obtained. The obtained distillate oil was treated by a chemical deoxygenation method, the treatment conditions were the same as in Example 2, stirring was performed at a speed of 800 r / min for 4 h, after the solution was stratified, the upper oil phase was taken to a new three-necked flask, an equal amount of desalted water was added, after a certain period of stirring, the solution was stratified, and the upper layer was the deoxygenated and refined distillate oil, the oxygen content of the deoxygenated distillate oil was 0.32 wt%. The deoxygenated distillate oil was again subjected to a second distillation cut in the distillation column, the cut conditions were the same as the first cut, the distillation cut temperature was controlled, and an oil having an initial boiling point of 200°C and a final boiling point of 310°C was obtained, which was a rich olefin mixed 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 66.2%, the mass content of linear alkanes was 13.6%, and the mass content of isomeric alkanes was 15.3%. The drilling fluid base oil physical property indexes are shown in Table 1.

[0062] Example 4:

[0063] 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 perform a first distillation cut, the distillation column had 25 theoretical plates, atmospheric distillation was used to remove the fraction less than 200°C, then the vacuum was controlled at 20 mmHg to remove the fraction greater than 310°C, and an oil having an initial boiling point of 200°C and a final boiling point of 310°C was obtained. The obtained distillate oil was treated by a chemical deoxygenation method, the treatment conditions were the same as in Example 2, stirring was performed at a speed of 800 r / min for 4 h, after the solution was stratified, the upper oil phase was taken to a new three-necked flask, an equal amount of desalted water was added, after a certain period of stirring, the solution was stratified, and the upper layer was the deoxygenated and refined distillate oil, the oxygen content of the deoxygenated distillate oil was 0.32 wt%. The deoxygenated distillate oil was again subjected to a second distillation cut in the distillation column, the cut conditions were the same as the first cut, the distillation cut temperature was controlled, and an oil having an initial boiling point of 200°C and a final boiling point of 310°C was obtained, which was a rich olefin mixed 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 66.2%, the mass content of linear alkanes was 13.6%, and the mass content of isomeric alkanes was 15.3%. The drilling fluid base oil physical property indexes are shown in Table 1.

[0064] Example 5:

[0065] A high-temperature Fischer-Tropsch synthesis slurry bed reaction device was used, with a synthesis gas with a H2 / CO ratio of 2:1 as a raw material, the device was operated at a temperature of 320 DEG C and a reaction pressure of 3 MPa, the reactor outlet product was collected, the oil product was added to the 5L rectifying column to perform a first distillation cut, the rectifying column had 25 theoretical plates, atmospheric distillation was used to remove the fraction less than 190 DEG C, then the vacuum degree was controlled to be 10 mmHg, and the fraction greater than 350 DEG C was removed, to obtain an oil product with an initial boiling point of 190 DEG C and a final boiling point of 350 DEG C. The obtained distillate oil was subjected to deoxygenation treatment by using a solvent extraction distillation method, a 95wt% methanol aqueous solution was used as an extractant, and repeated extraction was performed to remove oxygen-containing compounds in the distillate oil, and the oxygen content of the deoxygenated distillate oil was 0.46wt%. The deoxygenated distillate oil was subjected to a second distillation cut by using a rectifying column, and the cutting conditions were the same as those of the first cut, the distillation cut temperature was controlled, to obtain an oil product with an initial boiling point of 190 DEG C and a final boiling point of 350 DEG C, which was a rich olefin mixed type 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 73.6%, the mass content of linear alkanes was 10.1%, and the mass content of isomeric alkanes was 12.2%. The drilling fluid base oil physical property indexes are shown in Table 1.

[0066] Comparative Example 1

[0067] A low-temperature Fischer-Tropsch synthesis fixed bed reaction device was used, with a synthesis gas with a H2 / CO ratio of 2:1 as a raw material, the device was operated at a temperature of 220 DEG C and a reaction pressure of 2.5 MPa, the reactor outlet product was collected, and then hydrogenation isomerization treatment was performed under the process conditions of a reaction temperature of 320 DEG C, a pressure of 7 MPa, a space velocity of 2h -1 -1, and a hydrogen / oil ratio of 500, a PIC-812 hydrogenation isomerization catalyst of China Petroleum was used as a catalyst. Then, distillation cut was performed by using a rectifying column, the rectifying column had 25 theoretical plates, atmospheric distillation was used to remove the fraction less than 200 DEG C, then the vacuum degree was controlled to be 20 mmHg, and the fraction greater than 330 DEG C was removed, the initial boiling point was controlled to be 200 DEG C, the final boiling point was controlled to be 330 DEG C, and finally an alkanes type drilling fluid base oil with an isomeric alkane content of 80wt% was obtained.

[0068] Test Example 1

[0069] The rich olefin mixed type drilling fluid base oil derived from the Fischer-Tropsch synthesis oil in the application was used to prepare an oil-based drilling fluid according to the following formula to perform drilling fluid performance testing, and the formula was as follows: 240ml of the rich olefin mixed type base oil obtained in each example or the alkanes type drilling fluid base oil obtained in the comparative example, 8% emulsifier, 2.5% organic clay, 60ml of a 20% CaCl2 aqueous solution, 2% CaO, 4% filtration loss reducer, 666g of barite (Tabei barite), and an oil / water ratio of 4:1. The drilling fluid performance indexes are shown in Table 2.

[0070] Table 1 Drilling fluid base oil physical property indexes

[0071]

[0072] Table 2 drilling fluid performance index

[0073]

[0074] As shown in Table 1, the drilling fluid base oil provided by each embodiment of the present application contains both olefin and alkane components, and the performance characteristics of the olefin-based and alkane-based drilling fluid base oil are taken into account, the base oil does not need to be treated by isomerization process, and the base oil has low viscosity, which is conducive to improving the actual drilling rate, the performance index can be flexibly regulated, and the product has wide application range.

[0075] In Table 2, the rheological property and demulsification voltage are measured at 65℃, and the high temperature and high pressure filtration loss is measured after 16h of hot rolling at 150℃. As shown in Table 2, the drilling fluid prepared by using the drilling fluid base oil provided by the present application has the advantages of low viscosity, high demulsification voltage, and low high temperature and high pressure filtration loss.

[0076] 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, but these corresponding changes and modifications should all belong to the protection scope of the present application.

Claims

1. An olefin-rich hybrid drilling fluid base oil, characterized by, The drilling fluid base oil is obtained by distillation treatment and deoxygenation treatment of raw material high-temperature Fischer-Tropsch synthetic oil, the initial boiling point of the drilling fluid base oil is 150-250 DEG C, the final boiling point is 300-400 DEG C, it has 10-28 carbon straight chain terminal olefins and internal olefins and 10-28 carbon straight chain alkanes and isomeric alkanes, 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 12-24 carbon straight chain alkanes in the drilling fluid base oil is not less than 10%, the mass content of 12-24 carbon isomeric alkanes in the drilling fluid base oil is not less than 10%; the sulfur and nitrogen content of the drilling fluid base oil is less than 1 ppm, the flash point is not less than 80 DEG C, the pour point is not higher than -30 DEG C, the kinematic viscosity at 40 DEG C is not greater than 2 mm 2 / s.

2. The olefin-rich hybrid drilling fluid base oil of claim 1, wherein, The initial boiling point of the drilling fluid base oil is 170-200 DEG C, and the final boiling point is 300-350 DEG C.

3. The olefin-rich hybrid drilling fluid base oil of claim 1, wherein, 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.

4. The olefin-rich hybrid drilling fluid base oil of claim 1, wherein, The total mass content of linear terminal olefins and internal olefins with 12-24 carbons in the drilling fluid base oil is greater than or equal to 60%.

5. The olefin-rich hybrid drilling fluid base oil of claim 1, wherein, The mass content of oxygen in the drilling fluid base oil is not higher than 1.5%.

6. The olefin-rich hybrid drilling fluid base oil of claim 5, wherein, The mass content of oxygen in the drilling fluid base oil is not higher than 1%.

7. The olefin-rich hybrid drilling fluid base oil of claim 1, wherein, The deoxygenation treatment includes at least one of solvent extraction, physical adsorption and chemical removal.

8. A method of preparing the olefin-rich hybrid drilling fluid base oil according to any one of claims 1 to 7, characterized by, The method comprises the following steps: subjecting high-temperature Fischer-Tropsch synthesis oil to primary fraction cutting, subjecting the obtained primary cutting fraction oil to deoxygenation treatment, the mass content of oxygen being not higher than 1.5%, and subjecting the primary cutting fraction oil after deoxygenation to secondary fraction cutting again to obtain an olefin-rich mixed drilling fluid base oil with an initial boiling point of 150-250 DEG C and a final boiling point of 300-400 DEG C.

9. The production method according to claim 8, characterized by, The mass content of oxygen is not higher than 1.0%.

10. The preparation method according to claim 8, characterized in that, The initial boiling point of the olefin-rich mixed drilling fluid base oil is 170-200 DEG C.

11. The preparation method according to claim 8, characterized in that, The final boiling point of the olefin-rich mixed drilling fluid base oil is 300-350 DEG C.

12. The method of claim 8, wherein, The initial boiling point of the primary cutting fraction oil is 150-250 DEG C, and the final boiling point is 300-400 DEG C.

13. The method of claim 12, wherein, The initial boiling point of the primary cutting fraction oil is 170-200 DEG C.

14. The method of claim 12, wherein, The final boiling point of the primary cutting fraction oil is 300-350 DEG C.

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