A modified barite, its preparation method and application, and a synthetic-based drilling fluid

Abstract

The present invention provides a modified barite, a preparation method and application thereof, and a synthetic-based drilling fluid. The modified barite is prepared by subjecting barite to surface hydrophobic modification using plant polyphenols and a surfactant having a long-chain alkyl group. The surface of the modified barite is connected with a polyhydroxy polybenzene ring structure and a long-chain alkyl group through coordination complexation and / or electrostatic attraction. The present invention uses plant polyphenols and a surfactant having a long-chain alkyl group to perform surface hydrophobic modification on barite, improving the hydrophobicity of the barite surface, increasing the compatibility between the barite and the organic compounds in the synthetic-based drilling fluid, enabling it to better suspend in the synthetic-based drilling fluid, having excellent dispersion ability and anti-settling ability. At the same time, the synthetic-based drilling fluid system containing the modified barite also has excellent high-temperature resistance performance.

Description

Technical Field

[0001] The present invention relates to a modified barite, a preparation method and application thereof, and a synthetic-based drilling fluid, belonging to the technical field of oilfield exploitation. Background Art

[0002] With the increasing drilling and production intensity of oil and gas resources, the oil and gas are buried deeply, the reservoir temperature is high, and the drilling and production difficulty increases, posing a series of challenges to drilling fluid technology. Drilling fluid is the medium for circulating and flushing in the hole during drilling and punching, playing a key role in the drilling process of oil and gas wells, and at the same time being the fundamental factor causing pollution. Many of the components in drilling fluid contain chemical treatment agents with certain toxicity, and the impact of cuttings generated from the formation on the ecological environment is also difficult to recover. The weighting material is the main component of the dispersed phase in the drilling fluid system. Under high temperature and high pressure conditions, it is difficult to disperse and easy to settle, resulting in the drilling fluid being difficult to control the formation pressure due to insufficient density, causing difficulties in well control. Barite is widely sourced and has low production costs. It is the most common weighting material in high-density drilling fluids, with characteristics such as high density and stable chemical properties. As an inorganic material, due to large differences in chemical structure and physical form between barite and organic treatment agents, it is difficult to disperse evenly and is easy to settle from the suspension, resulting in a decrease in the rheology and sedimentation stability of the drilling fluid system, which may cause various drilling problems.

[0003] To improve the suspension ability of barite in synthetic-based drilling fluids, hydrophilic barite can be hydrophobically modified. The common chemical method is to form an adsorption layer of surfactant on the surface of barite to reduce the surface energy and surface polarity, thereby improving its dispersibility and compatibility with organic substances. However, this method has a complex process, the reaction process is not easy to control, and most surfactants have high costs, certain toxicity and pollution. Therefore, it is of great significance to find a safe and biodegradable natural plant modifier.

[0004] Therefore, providing a new type of modified barite, a preparation method and application thereof, and a synthetic-based drilling fluid to solve the problem of difficult dispersion and easy settlement of the inorganic material barite weighting agent, and constructing the molecular interaction force among the synthetic-based drilling fluid base fluid, organic treatment agent, and barite has become an urgent technical problem in this field. Summary of the Invention

[0005] To solve the above-mentioned drawbacks and deficiencies, one object of the present invention is to provide a modified barite.

[0006] Another object of the present invention is also to provide a preparation method for the above-mentioned modified barite.

[0007] Another object of the present invention is also to provide the application of the above-mentioned modified barite in oil and gas exploitation drilling operations.

[0008] Another object of the present invention is also to provide a synthetic-based drilling fluid, which contains the modified barite described above.

[0009] To achieve the above object, on the one hand, the present invention provides a modified barite, wherein the modified barite is obtained by surface hydrophobic modification of barite using plant polyphenols and a surfactant having a long-chain alkyl group, and a polyhydroxy polybenzene ring structure and a long-chain alkyl group are connected to the surface of the modified barite through coordination complexation and / or electrostatic attraction.

[0010] As a specific embodiment of the modified barite described above in the present invention, the plant polyphenols include one or a combination of several of tannic acid, gallic acid, sodium humate, phytic acid, etc. In some embodiments of the present invention, the tannic acid can be, for example, larch tannin or mimosa tannin, etc.

[0011] Plant polyphenol resources are important forestry characteristic biomass resources, which are rich in sources, low in price, good in biocompatibility, easy to degrade, mostly contain cyclic skeletons, are carbon-containing organic substances with stable structures, and usually contain structural advantages such as double bonds, hydroxyl groups and carboxylic acid groups. The present invention performs surface hydrophobic modification of barite using plant polyphenols and a surfactant having a long-chain alkyl group, which can improve the dispersibility and anti-settling performance of barite in the synthetic-based drilling fluid system, so that it can be better applied to deep oil and gas exploitation.

[0012] As a specific embodiment of the modified barite described above in the present invention, the carbon number of the long-chain alkyl group in the surfactant having a long-chain alkyl group is 6-18.

[0013] As a specific embodiment of the modified barite described above in the present invention, the surfactant having a long-chain alkyl group includes quaternary ammonium salt surfactants and / or organic amine surfactants, etc.

[0014] As a specific embodiment of the modified barite described above in the present invention, the quaternary ammonium salt surfactants include one or a combination of several of dodecyl trimethyl ammonium bromide, tetradecyl trimethyl ammonium bromide, hexadecyl trimethyl ammonium bromide, octadecyl trimethyl ammonium bromide, etc.

[0015] As a specific embodiment of the modified barite described above in the present invention, the organic amine surfactants include hexamethylenediamine and / or octamethylenediamine, etc.

[0016] As a specific embodiment of the modified barite described above in the present invention, the conditions for the surface hydrophobic modification include: the temperature is 40-80°C, the pH value is 8-10, preferably, the temperature is 50°C and the pH value is 8.5.

[0017] On the other hand, the present invention also provides a method for preparing the modified barite described above, wherein the preparation method includes:

[0018] Step 1: Disperse barite and plant polyphenols evenly in deionized water to obtain a mixed solution of barite and plant polyphenols;

[0019] Step 2: Under heating conditions, add a surfactant with a long-chain alkyl group to the mixed solution of barite and plant polyphenols and then adjust the system to be alkaline to perform surface hydrophobic modification on barite;

[0020] Step 3: Centrifuge and wash the solution obtained in Step 2, and then dry and grind the obtained precipitate to obtain the modified barite.

[0021] As a specific embodiment of the preparation method described above in the present invention, the mass ratio of the barite, the plant polyphenols, and the surfactant with a long-chain alkyl group is 20-30:1-3:1-2.

[0022] As a specific embodiment of the preparation method described above in the present invention, in Step 2, the heating temperature is 40-80°C, a pH regulator is added to adjust the pH value of the system to 8-10, and the time for surface hydrophobic modification is 2-5 h; preferably, the heating temperature is 50°C, a pH regulator is added to adjust the pH value of the system to 8.5, and the time for surface hydrophobic modification is 4 h.

[0023] As a specific embodiment of the preparation method described above in the present invention, the pH regulator includes sodium hydroxide solution, etc.

[0024] As a specific embodiment of the preparation method described above in the present invention, the washing is performed by alternately washing with deionized water and absolute ethanol. The present invention does not make specific requirements on the number of times of alternately washing with deionized water and absolute ethanol, and can be reasonably adjusted according to the actual on-site operation needs. For example, in some embodiments of the present invention, the deionized water and absolute ethanol can be used for three alternate washings.

[0025] As a specific embodiment of the preparation method described above in the present invention, the drying is carried out at 60-80°C for 12-24 h, preferably, the drying is carried out at 70°C for 24 h.

[0026] On the other hand, the present invention also provides the application of the modified barite described above in oil and gas exploration drilling operations.

[0027] As a specific embodiment of the application described above in the present invention, the oil and gas exploration drilling operation is a deep oil and gas exploration drilling operation.

[0028] On the other hand, the present invention also provides a synthetic-based drilling fluid, wherein the synthetic-based drilling fluid contains the modified barite described above. The synthetic-based drilling fluid system provided by the present invention has excellent rheological properties, sedimentation stability and temperature resistance. In addition, the present invention does not make specific requirements on the base fluid, organic treatment agent, etc. used in the synthetic-based drilling fluid, and can be reasonably selected / adjusted according to the actual on-site operation needs.

[0029] Compared with the prior art, the beneficial technical effects that the present invention can achieve include:

[0030] 1) The present invention uses plant polyphenols and a surfactant with a long-chain alkyl group as modifiers to perform surface hydrophobic modification on barite. A large number of phenolic hydroxyl groups in the plant polyphenols can form a stable coordination complex with free cations (such as metal ions) on the surface of barite, thereby introducing a polyhydroxy polybenzene ring structure on the surface of barite, which is equivalent to forming a coating layer on the surface of barite, improving its temperature resistance and environmental friendliness; under alkaline conditions, functional groups such as carboxyl groups and phenolic hydroxyl groups in the plant polyphenols are easily deprotonated and negatively charged, and this negative charge undergoes electrostatic attraction with positively charged surfactant ions, such as quaternary ammonium salt ions, etc., thereby introducing a long-chain alkyl group with a stable structure on the surface of barite, which is equivalent to forming a stable hydrophobic adsorption layer on the surface of barite, thereby improving the surface hydrophobicity of barite, as well as its dispersibility and sedimentation stability in the synthetic-based drilling fluid system.

[0031] Therefore, the present invention uses plant polyphenols and a surfactant with a long-chain alkyl group to perform surface hydrophobic modification on barite, improving the hydrophobicity of the barite surface, increasing the compatibility between barite and organic compounds in the synthetic-based drilling fluid, enabling it to better suspend in the synthetic-based drilling fluid, and having excellent dispersion ability and anti-sedimentation ability.

[0032] 2) The plant polyphenols used in the present invention are natural materials, having good biocompatibility, rich sources and low production costs. The preparation method of the modified barite provided by the present invention has the advantages of simple operation, low production cost and environmental friendliness.

[0033] 3) Using the modified barite with excellent hydrophobic properties provided by the present invention in oil and gas exploration drilling operations, it has good compatibility with high-density synthetic-based drilling fluids. Treatment agents such as emulsifiers, organic clays, and filtration loss reducers in the synthetic-based drilling fluid system can form a stable spatial network structure with the modified barite, enhancing the loading capacity for the modified barite. At the same time, the hydrophobic surface also helps to prevent the aggregation and sedimentation of the modified barite, improving the rheological properties and sedimentation stability of the synthetic-based drilling fluid system, and introducing a polyhydroxy polybenzene ring structure on the surface of barite can also improve the temperature resistance of the synthetic-based drilling fluid system. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0035] Figure 1 It is the infrared spectrogram obtained in Characterization Test Example 1 of the present invention. Among them, a, b, and c are the modified barites provided in Embodiments 1-3 of the present invention respectively.

[0036] Figure 2 It is the infrared spectrogram obtained in Characterization Test Example 2 of the present invention. Among them, a is tannic acid, and b is the modified barite provided in Embodiment 4 of the present invention.

[0037] Figure 3a It is the scanning electron micrograph of the modified barite provided in Embodiment 1 of the present invention.

[0038] Figure 3b It is the scanning electron micrograph of the modified barite provided in Embodiment 2 of the present invention.

[0039] Figure 3c It is the scanning electron micrograph of the modified barite provided in Embodiment 3 of the present invention.

[0040] Figure 3d It is the scanning electron micrograph of the modified barite provided in Comparative Example 1.

[0041] Figure 4a It is the scanning electron micrograph (30.0μm) of the modified barite provided in Embodiment 4 of the present invention.

[0042] Figure 4b It is the scanning electron micrograph (5.00μm) of the modified barite provided in Embodiment 4 of the present invention.

[0043] Figure 4c It is the scanning electron micrograph (3.00μm) of the modified barite provided in Embodiment 4 of the present invention.

[0044] Figure 4d It is the scanning electron micrograph (1.00μm) of the modified barite provided in Embodiment 4 of the present invention.

[0045] Figure 5a It is the contact angle schematic diagram of the barite raw material used in Embodiment 4 of the present invention, that is, unmodified barite.

[0046] Figure 5b It is the contact angle schematic diagram of the modified barite prepared in Embodiment 4 of the present invention. Detailed implementation manners

[0047] It should be noted that the term "comprising" and any variations thereof in the description, claims, and above-mentioned drawings of the present invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that comprises a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0048] The "range" disclosed in the present invention is given in the form of a lower limit and an upper limit. There may be one or more lower limits, and one or more upper limits. A given range is defined by selecting a lower limit and an upper limit. The selected lower limit and upper limit define the boundary of a particular range. All ranges defined in this way are combinable, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. Additionally, if the minimum range values listed are 1 and 2, and the maximum range values listed are 3, 4, and 5, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5.

[0049] In the present invention, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where both a and b are real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are fully listed in the present invention, and "0 - 5" is only an abbreviated representation of these numerical combinations.

[0050] In the present invention, if there is no special indication, all the embodiments and preferred embodiments mentioned in the present invention can be combined with each other to form a new technical solution.

[0051] In the present invention, if there is no special indication, all the technical features and preferred features mentioned in the present invention can be combined with each other to form a new technical solution.

[0052] In the present invention, unless otherwise specified, the term "two" used in this specification means "at least two".

[0053] In the present invention, unless otherwise specified, all steps mentioned herein can be carried out sequentially or randomly, but preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) carried out sequentially, or may also include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), indicating that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or may also include steps (a), (c), and (b), or may also include steps (c), (a), and (b), etc.

[0054] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with the attached tables, drawings and embodiments. The following described embodiments are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts fall within the scope of protection of the present invention. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained through commercial purchase.

[0055] Example 1

[0056] This example provides a modified barite, which is prepared by a preparation method including the following specific steps:

[0057] Step 1: Add 30 g of barite (with a density of 4.3 g / cm 3 , a particle size of 20 - 40 μm) and 1 g of tannic acid to 100 mL of deionized water, stir to disperse them evenly, and then ultrasonicate for 30 min to obtain a mixed solution of barite and tannic acid;

[0058] Step 2: Under the heating condition of 50 °C, add 1 g of cetyltrimethylammonium bromide to the mixed solution of barite and tannic acid, and then use sodium hydroxide solution to adjust the pH value of the system to 8.5, and stir at a constant temperature for 4 h to perform surface modification on the barite;

[0059] Step 3: Centrifuge the solution obtained after the reaction in Step 2, and wash it three times alternately with deionized water and absolute ethanol to obtain a modified barite precipitate; then dry the precipitate at 70 °C for 18 h and grind it into powder to obtain the finished product of modified barite.

[0060] Example 2

[0061] This embodiment provides a modified barite, which is prepared by a preparation method including the following specific steps:

[0062] Step 1: Add 20 g of barite (density: 4.3 g / cm 3 , particle size: 20 - 40 μm) and 1 g of sodium humate to 100 mL of deionized water. Stir to disperse evenly and then ultrasonicate for 30 min to obtain a mixed solution of barite and sodium humate;

[0063] Step 2: Under the heating condition of 60 °C, add 1 g of cetyltrimethylammonium bromide to the mixed solution of barite and sodium humate, and then adjust the pH value of the system to 10 with sodium hydroxide solution. Stir at a constant temperature for 4 h to perform surface modification on the barite;

[0064] Step 3: Centrifuge the solution obtained after the reaction in Step 2, and wash it three times alternately with deionized water and absolute ethanol to obtain a modified barite precipitate; then dry the precipitate at 80 °C for 12 h and grind it into powder to obtain the finished product of modified barite.

[0065] Example 3

[0066] This embodiment provides a modified barite, which is prepared by a preparation method including the following specific steps:

[0067] Step 1: Add 25 g of barite (density: 4.3 g / cm 3 , particle size: 20 - 40 μm) and 1.5 g of phytic acid to 100 mL of deionized water. Stir to disperse evenly and then ultrasonicate for 30 min to obtain a mixed solution of barite and phytic acid;

[0068] Step 2: Under the heating condition of 40 °C, add 1.5 g of cetyltrimethylammonium bromide to the mixed solution of barite and phytic acid, and then adjust the pH value of the system to 8 with sodium hydroxide solution. Stir at a constant temperature for 3 h to perform surface modification on the barite;

[0069] Step 3: Centrifuge the solution obtained after the reaction in Step 2, and wash it three times alternately with deionized water and absolute ethanol to obtain a modified barite precipitate; then dry the precipitate at 60 °C for 24 h and grind it into powder to obtain the finished product of modified barite.

[0070] Example 4

[0071] This embodiment provides a modified barite, which is prepared by a preparation method including the following specific steps:

[0072] Step 1: Add 30 g of barite (density: 4.3 g / cm 3, barite with a particle size of 20 - 40 μm) and 1 g of tannic acid were added to 100 mL of deionized water. After stirring to disperse evenly, it was ultrasonicated for 30 min to obtain a mixed solution of barite and tannic acid;

[0073] Step 2: Under the heating condition of 50 °C, 1 g of hexamethylenediamine was added to the mixed solution of barite and tannic acid, and then the pH value of the system was adjusted to 8.5 using sodium hydroxide solution, and stirred at a constant temperature for 4 h to modify the surface of barite;

[0074] Step 3: The solution obtained after the reaction in Step 2 was centrifuged, and alternately washed three times with deionized water and absolute ethanol to obtain modified barite precipitate; then the precipitate was dried at 70 °C for 18 h and ground into powder to obtain the modified barite product.

[0075] Comparative Example 1

[0076] This comparative example provides a modified barite, which is prepared by a preparation method including the following specific steps:

[0077] Step 1: 30 g of barite (density 4.3 g / cm 3 , particle size 20 - 40 μm) and 1 g of gallic acid were added to 100 mL of deionized water. After stirring to disperse evenly, it was ultrasonicated for 30 min to obtain a mixed solution of barite and gallic acid;

[0078] Step 2: Under the heating condition of 50 °C, sodium hydroxide solution was added to the mixed solution of barite and gallic acid to adjust the pH value of the system to 8.5, and stirred at a constant temperature for 4 h to modify the surface of barite;

[0079] Step 3: The solution obtained after the reaction in Step 2 was centrifuged, and alternately washed three times with deionized water and absolute ethanol to obtain modified barite precipitate; then the precipitate was dried at 70 °C for 24 h and ground into powder to obtain the modified barite product.

[0080] Comparative Example 2

[0081] This comparative example provides a conventional unmodified barite (density 4.3 g / cm 3 , particle size 20 - 40 μm).

[0082] Example 5

[0083] This example provides a high - density synthetic - based drilling fluid, which is prepared by a preparation method including the following specific steps:

[0084] Add 240 mL of No. 3 white oil, 24 g of primary emulsifier and secondary emulsifier (Wang Maogong, et al. Development and performance evaluation of emulsifiers for high-temperature gas-based oil-based drilling fluids [J]. Drilling Fluid & Completion Fluid, 2012, 29(6), and the mass ratio of the primary emulsifier to the secondary emulsifier is 1:1) into a 300 mL high-speed stirring cup, and stir at a speed of 11000 r / min for 20 min; then add 60 mL of 20 wt% CaCl 2 brine, and stir at a speed of 11000 r / min for 10 min; then add 7.5 g of organophilic clay, and stir at a speed of 11000 r / min for 10 min; continue to add 12 g of filtrate reducer (oxidized asphalt), and stir at a speed of 11000 r / min for 10 min; add 6 g of alkalinity regulator CaO, and stir at a speed of 11000 r / min for 10 min; finally add 480 g of the modified barite provided in Example 1, and stir at a speed of 11000 r / min for 40 min to finally obtain a high-density synthetic-based drilling fluid.

[0085] Example 6

[0086] This example provides a high-density synthetic-based drilling fluid, which is prepared by a preparation method including the following specific steps:

[0087] Add 240 mL of No. 3 white oil, 24 g of primary emulsifier and secondary emulsifier (Wang Maogong, et al. Development and performance evaluation of emulsifiers for high-temperature gas-based oil-based drilling fluids [J]. Drilling Fluid & Completion Fluid, 2012, 29(6), and the mass ratio of the primary emulsifier to the secondary emulsifier is 1:1) into a 300 mL high-speed stirring cup, and stir at a speed of 11000 r / min for 20 min; then add 60 mL of 20 wt% CaCl 2 brine, and stir at a speed of 11000 r / min for 10 min; then add 7.5 g of organophilic clay, and stir at a speed of 11000 r / min for 10 min; continue to add 12 g of filtrate reducer (oxidized asphalt), and stir at a speed of 11000 r / min for 10 min; add 6 g of alkalinity regulator CaO, and stir at a speed of 11000 r / min for 10 min; finally add 480 g of the modified barite provided in Example 2, and stir at a speed of 11000 r / min for 40 min to finally obtain a high-density synthetic-based drilling fluid.

[0088] Example 7

[0089] This example provides a high-density synthetic-based drilling fluid, which is prepared by a preparation method including the following specific steps:

[0090] Add 240 mL of No. 3 white oil, 24 g of primary emulsifier and secondary emulsifier (Wang Maogong, etc. Research and performance evaluation of emulsifiers for high-temperature gas-based oil-based drilling fluids [J]. Drilling Fluid & Completion Fluid, 2012, 29(6), and the mass ratio of the primary emulsifier to the secondary emulsifier is 1:1) into a 300 mL high-speed stirring cup, and stir at a speed of 11000 r / min for 20 min; then add 60 mL of 20 wt% CaCl 2 brine, and stir at a speed of 11000 r / min for 10 min; then add 7.5 g of organoclay, and stir at a speed of 11000 r / min for 10 min; continue to add 12 g of filtrate reducer (oxidized asphalt), and stir at a speed of 11000 r / min for 10 min; add 6 g of alkalinity regulator CaO, and stir at a speed of 11000 r / min for 10 min; finally add 480 g of the modified barite provided in Example 3, and stir at a speed of 11000 r / min for 40 min to finally obtain a high-density synthetic-based drilling fluid.

[0091] Example 8

[0092] This example provides a high-density synthetic-based drilling fluid, which is prepared by a preparation method including the following specific steps:

[0093] Add 240 mL of No. 3 white oil, 24 g of primary emulsifier and secondary emulsifier (Wang Maogong, etc. Research and performance evaluation of emulsifiers for high-temperature gas-based oil-based drilling fluids [J]. Drilling Fluid & Completion Fluid, 2012, 29(6), and the mass ratio of the primary emulsifier to the secondary emulsifier is 1:1) into a 300 mL high-speed stirring cup, and stir at a speed of 11000 r / min for 20 min; then add 60 mL of 20 wt% CaCl 2 brine, and stir at a speed of 11000 r / min for 10 min; then add 7.5 g of organoclay, and stir at a speed of 11000 r / min for 10 min; continue to add 12 g of filtrate reducer (oxidized asphalt), and stir at a speed of 11000 r / min for 10 min; add 6 g of alkalinity regulator CaO, and stir at a speed of 11000 r / min for 10 min; finally add 480 g of the modified barite provided in Example 4, and stir at a speed of 11000 r / min for 40 min to finally obtain a high-density synthetic-based drilling fluid.

[0094] Comparative Example 3

[0095] This comparative example provides a high-density synthetic-based drilling fluid, which is prepared by a preparation method including the following specific steps:

[0096] Add 240 mL of No. 3 white oil, 24 g of the main emulsifier and auxiliary emulsifier (Wang Maogong, etc. Research and performance evaluation of emulsifiers for high-temperature gas-based oil-based drilling fluids [J]. Drilling Fluid & Completion Fluid, 2012, 29(6), and the mass ratio of the main emulsifier to the auxiliary emulsifier is 1:1) into a 300 mL high-speed stirring cup, and stir at a speed of 11000 r / min for 20 min; then add 60 mL of 20 wt% CaCl 2 brine, and stir at a speed of 11000 r / min for 10 min; then add 7.5 g of organophilic clay, and stir at a speed of 11000 r / min for 10 min; continue to add 12 g of filtrate reducer (oxidized asphalt), and stir at a speed of 11000 r / min for 10 min; then add 6 g of alkalinity regulator CaO, and stir at a speed of 11000 r / min for 10 min; finally add 480 g of the modified barite provided in Comparative Example 1, and stir at a speed of 11000 r / min for 40 min to finally obtain a high-density synthetic-based drilling fluid.

[0097] Comparative Example 4

[0098] This comparative example provides a high-density synthetic-based drilling fluid, which is prepared by a preparation method including the following specific steps:

[0099] Add 240 mL of No. 3 white oil, 24 g of the main emulsifier and auxiliary emulsifier (Wang Maogong, etc. Research and performance evaluation of emulsifiers for high-temperature gas-based oil-based drilling fluids [J]. Drilling Fluid & Completion Fluid, 2012, 29(6), and the mass ratio of the main emulsifier to the auxiliary emulsifier is 1:1) into a 300 mL high-speed stirring cup, and stir at a speed of 11000 r / min for 20 min; then add 60 mL of 20 wt% CaCl 2 brine, and stir at a speed of 11000 r / min for 10 min; then add 7.5 g of organophilic clay, and stir at a speed of 11000 r / min for 10 min; continue to add 12 g of filtrate reducer (oxidized asphalt), and stir at a speed of 11000 r / min for 10 min; then add 6 g of alkalinity regulator CaO, and stir at a speed of 11000 r / min for 10 min; finally add 480 g of the barite provided in Comparative Example 2, and stir at a speed of 11000 r / min for 40 min to finally obtain a high-density synthetic-based drilling fluid.

[0100] Characterization Test Example 1

[0101] This characterization test example respectively conducts infrared spectroscopy analysis on the modified barite products provided in Examples 1 - 3, and the obtained infrared spectra are as Figure 1 shown.

[0102] From Figure 1It can be seen that the peak at 3260 cm -1 -3530 cm -1 is a broad peak generated by the stretching vibrations of O-H and N-H on plant polyphenols and cetyltrimethylammonium bromide; the peaks at 2820 cm -1 and 2930 cm -1 are the two vibration peaks of C-H on cetyltrimethylammonium bromide; the peak at 1615 cm -1 is the absorption peak formed by the C=O bond of plant polyphenols; the peak at 1470 cm -1 is generated by C-N stretching vibration. The above infrared results show that: the polyhydroxy polybenzene ring structure in plant polyphenols can be adsorbed on the surface of barite through metal chelation to form a coating layer. At the same time, functional groups such as carboxyl groups and phenolic hydroxyl groups on plant polyphenols carry negative charges under alkaline conditions and can undergo electrostatic adsorption with the quaternary ammonium positive ions of cetyltrimethylammonium bromide, further ensuring the successful modification of barite.

[0103] Characterization Test Example 2

[0104] In this characterization test example, infrared spectroscopy analysis was performed on tannic acid and the modified barite prepared in Example 4 respectively, and the obtained infrared spectra are as shown in Figure 2 as follows.

[0105] As shown in Figure 2 a broad peak appears at 3280 cm -1 -3500 cm -1 which is mainly generated by the stretching vibrations of O-H and N-H provided by tannic acid and hexamethylenediamine respectively; the peaks at 2820 cm -1 and 2930 cm -1 are the two stretching vibration peaks of C-H on the alkyl chain of hexamethylenediamine; the peak at 1615 cm -1 is the absorption peak formed by the C=O bond in tannic acid; the peak at 900 cm -1 is the peak generated by the C=C stretching vibration on the benzene ring of tannic acid. From the changes in the stretching peaks and the increase in the content of C-H and N-H in the product, it can be seen that tannic acid and hexamethylenediamine have successfully modified barite.

[0106] Characterization Test Example 3

[0107] In this characterization test example, scanning electron microscopy analysis was performed on the modified barite provided in Examples 1-4 and Comparative Example 1 respectively, and the obtained scanning electron micrographs are as shown in Figures 3a - 3d and Figures 4a - 4d as follows. It can be seen from Figures 3a - 3d that for the modified barite provided in Examples 1-4 and Comparative Example 1, the modifier adheres to the barite relatively uniformly, and there are differences in the coating degree. Some of the adherents are easily peeled off from the surface of barite, resulting in a decline in its performance, while fromFigures 4a - 4d It can be seen that the modifier is completely coated on the modified barite prepared in Example 4, and is evenly and densely distributed. This is because the amino groups at both ends of hexamethylenediamine form chemical bonds with multiple phenolic hydroxyl groups and ortho-para positions of the tannic acid molecules, so that the tannic acid molecules are tightly connected to completely coat the barite and are not easy to fall off; in contrast, the interaction force between the barite, plant polyphenols, and hexadecyltrimethylammonium bromide molecules is electrostatic attraction, and there is no chemical bond, which makes the attachment easy to peel off.

[0108] Characterization Test Example 4

[0109] This characterization test example measures the contact angles of the barite raw materials used in Example 4, i.e., the unmodified barite and the modified barite obtained in Example 4, respectively. The test process includes: first, using a tablet press to press the unmodified barite and the modified barite obtained in Example 4, respectively, with a pressure of 15-20Pa and a pressing time of 90-105s; then, 5 μL of water is dropped onto the surface of the object to be tested through a contact angle meter, and the static contact angle at 5s is recorded, and the average value is taken after three measurements.

[0110] The contact angle diagram of the barite raw material used in Example 4, i.e., the unmodified barite, is as follows: Figure 5a As shown, the contact angle diagram of the modified barite obtained in Example 4 is as follows Figure 5b As shown. Figure 5a and Figure 5b It can be seen that the contact angle of unmodified barite is 20.2°, and the contact angle of modified barite is 89.0°. By comparison, it can be seen that the hydrophobicity of modified barite is significantly improved.

[0111] Test Example 1

[0112] This test example evaluates the rheological properties of the high-density synthetic-based drilling fluids provided in Examples 5 to 8 and Comparative Examples 3 to 4, respectively. The evaluation process includes:

[0113] (1) After the high-density synthetic drilling fluid was stirred at a speed of 11000 r / min for 20 min, the stable readings of Φ600, Φ300, Φ200, Φ100, Φ6, and Φ3 were measured using a six-speed rotational viscometer according to the standard GB / T16783-1997. The speed was then adjusted to Φ600 and rotated for 10 s. After standing for 10 s, the maximum value of Φ3 was recorded as the initial cutting value τ of the drilling fluid. 10s Adjust the speed to Φ600 and rotate for 10 seconds. Let it stand for 10 minutes and record the maximum value of Φ3 as the final cutting value τ of the drilling fluid. 10min .

[0114] (2) Put the high-density synthetic-based drilling fluid into a 300 mL reactor, tighten the screws and the air vent valve, and place it in a high-temperature heating roller furnace after safety inspection. Age it at 180 °C for 16 h.

[0115] (3) After stirring the aged high-density synthetic-based drilling fluid at a speed of 11,000 r / min for 20 min, refer to the standard GB / T 16783-1997, and use a six-speed rotational viscometer to measure the stable readings of Φ600, Φ300, Φ200, Φ100, Φ6, and Φ3 respectively. Then adjust the speed to Φ600 and rotate for 10 s, let it stand for 10 s and record the maximum value of Φ3 as the initial shear value τ of the drilling fluid. 10s Adjust the speed to Φ600 and rotate for 10 s, let it stand for 10 min and record the maximum value of Φ3 as the final shear value τ of the drilling fluid. 10min 。

[0116] (4) Calculate the apparent viscosity AV, plastic viscosity PV, yield point YP, yield point / plastic viscosity ratio YP / PV, and gel strength Gel of the high-density synthetic-based drilling fluid according to the parameters obtained above using the following formulas.

[0117] Apparent viscosity: AV = η 表 = Φ600 / 2, with the unit of mPa·s;

[0118] Plastic viscosity: PV = η 塑 = Φ600 - Φ300, with the unit of mPa·s;

[0119] Yield point: YP = τ0 = (Φ300 - PV) / 2 = Φ300 - Φ600 / 2, with the unit of Pa;

[0120] Yield point / plastic viscosity ratio: YP / PV = (Φ300 - Φ600 / 2) / (Φ600 - Φ300), with the unit of Pa / (mPa·s);

[0121] Static shear force: Gel 10s = τ 10s / 2, with the unit of Pa, Gel 10min = τ 10min / 2, with the unit of Pa.

[0122] The influence results of the modified barite provided in Examples 1-4 and Comparative Example 1 and the barite provided in Comparative Example 2 on the rheological properties of the high-density synthetic-based drilling fluid system are shown in Table 1.

[0123] Table 1

[0124]

[0125]

[0126] As can be seen from the experimental data in Table 1, after adding the modified barite provided in Examples 1 - 4 to the high-density synthetic-based drilling fluid, the change in its rheological parameters before and after aging is small, indicating that the modified barite product provided in the embodiments of the present invention has excellent temperature resistance and has little impact on the rheology of the drilling fluid. From the experimental data in the comparative examples, it can be seen that the modified barite provided in Examples 1, 3, and 4 of the present invention has the most obvious improvement in the stability of the drilling fluid. After aging at 180°C for 16 h, the rheological properties still remain stable, which greatly improves the actual drilling operation efficiency. The modified barite provided in Example 2 has a greater impact on the rheology of the drilling fluid and weaker high-temperature resistance, but the change in the dynamic-plastic ratio and contact angle before and after aging (the contact angle change data is shown in Table 2 below) is very small, and it can be used in combination with other modified barites. In addition, sodium humate itself has the functions of reducing filtration loss and viscosity, and will improve the filtration loss performance of the wellbore wall. Compared with the examples, the change in rheology before and after aging of the drilling fluid prepared by adding the modified barite and barite provided in Comparative Examples 1 - 2 is relatively large, which shows that the properties of the modified barite prepared by only surface hydrophobic modification of barite with plant polyphenols and the unmodified barite are both inferior to the modified barite prepared by surface hydrophobic modification of barite with plant polyphenols and a surfactant with a long-chain alkyl group in the embodiments of the present invention.

[0127] Test Example 2

[0128] In this test example, the contact angles of the high-density synthetic-based drilling fluids provided in Examples 5 - 8 and Comparative Examples 3 - 4 before and after aging were tested respectively. Among them, the aging process includes:

[0129] Put the high-density synthetic-based drilling fluid into a 300 mL reactor, tighten the screws and the air valve, and place it in a high-temperature heating roller furnace after safety inspection. Age at 180°C for 16 h;

[0130] The contact angle test includes:

[0131] The influence results of the modified barite provided in Examples 1 - 4 and Comparative Example 1 and the barite provided in Comparative Example 2 on the contact angle performance of the high-density synthetic-based drilling fluid system are shown in Table 2.

[0132] Table 2

[0133]

[0134] Table 2 shows the influence of the modified barite or barite prepared in Examples 1 - 4 and Comparative Examples 1 - 2 on the contact angle performance of the high - density synthetic - based drilling fluid system. It can be seen from Table 2 that the contact angles of the drilling fluids prepared by adding the modified barite provided in Examples 1 - 4 are all above 80°, indicating that the modified barite provided by the present invention can improve the contact angle performance of the drilling fluid. And the contact angle of the drilling fluid prepared by adding the modified barite provided in Example 4 can reach as high as 105.2°, indicating that the modified barite provided in Example 4 has the greatest improvement on the contact angle performance of the drilling fluid. It can also be seen from Table 2 that before and after aging, the contact angles of the drilling fluids prepared by adding the modified barite provided in Examples 2 - 4 decrease less, indicating that the change in the composition of the drilling fluid under high - temperature and high - pressure conditions is relatively small, and its temperature - resistance performance and stability are excellent. While the contact angle of the drilling fluid prepared by adding the modified barite provided in Example 1 decreases more, probably because during the high - temperature aging process, the electrostatic adsorption between barite, tannic acid, and cetyltrimethylammonium bromide is weakened by high temperature, but it is still improved compared with unmodified barite. Although the contact angle of the drilling fluid prepared by adding unmodified barite can reach 93.1°, before and after aging, the contact angle of the drilling fluid decreases by nearly 50°. For the drilling fluid prepared by adding the modified barite provided in Comparative Example 1, although the contact angle of the drilling fluid decreases less before and after aging, the contact angles of the drilling fluid before and after aging are only 42.7° and 29.9° respectively, probably because the interaction between this modified barite and other organic treating agents in the drilling fluid is relatively large, reducing the contact angle of the whole system and affecting the overall performance of the drilling fluid. This also shows that the performance of the modified barite prepared by only surface - hydrophobic modification of barite with plant polyphenols and unmodified barite is inferior to that of the modified barite prepared by surface - hydrophobic modification of barite with plant polyphenols and a surfactant with a long - chain alkyl group in the examples of the present invention.

[0135] As mentioned above, the above are only specific embodiments of the present invention and cannot limit the scope of the invention implementation. Therefore, the replacement of equivalent components or the equivalent changes and modifications made according to the scope of the present invention patent protection should still fall within the scope covered by this patent. In addition, the technical features in the present invention can be freely combined with each other between technical features, between technical features and technical inventions, and between technical inventions.

Claims

1. A modified barite, characterized in that, the modified barite is prepared by surface hydrophobic modification of barite with plant polyphenols and a surfactant having a long-chain alkyl group under alkaline conditions, wherein the pH value of the alkaline conditions is 8-10 and the mass ratio of the barite, the plant polyphenols and the surfactant having a long-chain alkyl group is 20-30:1-3:1-2, and the plant polyphenols include one or a combination of several of gallic acid, sodium humate and phytic acid; the surface of the modified barite is connected with a polyhydroxy polybenzene ring structure and a long-chain alkyl group through coordination complexation and / or electrostatic attraction, and the surface of the modified barite is hydrophobic.

2. The modified barite according to claim 1, characterized in that, the carbon number of the long-chain alkyl in the surfactant having a long-chain alkyl group is 6-18.

3. The modified barite according to claim 2, characterized in that, the surfactant having a long-chain alkyl group includes a quaternary ammonium salt surfactant and / or an organic amine surfactant.

4. The modified barite according to claim 3, characterized in that, the quaternary ammonium salt surfactant includes one or a combination of several of dodecyl trimethyl ammonium bromide, tetradecyl trimethyl ammonium bromide, hexadecyl trimethyl ammonium bromide and octadecyl trimethyl ammonium bromide.

5. The modified barite according to claim 3, characterized in that, the organic amine surfactant includes hexamethylenediamine and / or octamethylenediamine.

6. The modified barite according to any one of claims 1-5, characterized in that, the conditions for the surface hydrophobic modification include: the temperature is 40-80 °C.

7. A method for preparing the modified barite according to any one of claims 1-6, characterized in that, the preparation method includes: Step 1: Disperse barite and plant polyphenols evenly in deionized water to obtain a mixed solution of barite and plant polyphenols; Step 2: Under heating conditions, add a surfactant having a long-chain alkyl group to the mixed solution of barite and plant polyphenols and then adjust the pH value of the system to 8-10 to perform surface hydrophobic modification on barite; wherein, the mass ratio of the barite, the plant polyphenols and the surfactant having a long-chain alkyl group is 20-30:1-3:1-2, and the plant polyphenols include one or a combination of several of gallic acid, sodium humate and phytic acid; Step 3: Centrifuge and wash the solution obtained in Step 2, and then dry and grind the obtained precipitate to obtain the modified barite.

8. The preparation method according to claim 7, characterized in that, in Step 2, the heating temperature is 40-80 °C and the time for surface hydrophobic modification is 2-5 h.

9. The preparation method according to claim 7, characterized in that, the pH regulator includes a sodium hydroxide solution.

10. The preparation method according to claim 7, characterized in that, the washing is alternately washing with deionized water and absolute ethanol.

11. The preparation method according to claim 7, characterized in that, The drying is carried out at 60-80 °C for 12-24 h.

12. Use of the modified barite according to any one of claims 1-6 in oil and gas exploration drilling operations.

13. A synthetic-based drilling fluid, characterized in that the synthetic-based drilling fluid contains the modified barite according to any one of claims 1-6.

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