CN109824839B - Nano-silica graft copolymer, preparation method and application thereof, and drilling fluid and application thereof - Google Patents
Nano-silica graft copolymer, preparation method and application thereof, and drilling fluid and application thereof Download PDFInfo
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Abstract
The invention relates to the field of drilling in the petroleum industry, in particular to a nano silicon dioxide graft copolymer with temperature resistance and calcium resistance and suitable for fluid loss reduction, a preparation method and application thereof, and a drilling fluid and application thereof. The nano silica graft copolymer of the present invention contains one or more of the structural units represented by the following formula (1), one or more of the structural units represented by the formula (2), one or more of the structural units represented by the formula (3), and one or more of the structural units represented by the formula (4). The copolymer provided by the invention can successfully obtain good high-temperature and high-calcium resistant effects when the copolymer is used in a drilling fluid as a fluid loss additive through the coordination effect among the structural unit shown in the formula (1), the structural unit shown in the formula (2), the structural unit shown in the formula (3) and the structural unit shown in the formula (4).
Description
Technical Field
The invention relates to the field of drilling in the petroleum industry, in particular to a nano silicon dioxide graft copolymer with temperature resistance and calcium resistance and suitable for fluid loss reduction, a preparation method and application thereof, and a drilling fluid and application thereof.
Background
With the development of oil drilling technology and the reduction of conventional oil and gas reserves, the exploration and development of oil and gas resources gradually shift to deep unconventional oil reservoirs. The drilling fluid is used as a circulating fluid which can meet multiple functions of drilling work, and plays an important role in the aspects of cleaning a well bottom, carrying rock debris, cooling, lubricating a drill bit and the like. However, as the depth of the formation increases, the drilling fluid must experience prolonged high temperatures and various cationic contaminations. Although the performance of the oil-based drilling fluid is superior to that of the water-based drilling fluid, the oil-based drilling fluid has the defects of high cost, difficult waste liquid treatment and the like. Drilling fluid loss additives are treatments used to reduce the amount of fluid loss from the fluid phase of the drilling fluid leaking into the formation. The excessive filtration loss in the drilling fluid can cause the filter cake of the well wall to be too thick, and fine clay particles can enter the stratum along with the filtrate, so that the stratum is damaged, and the normal drilling is influenced. The common filtrate reducer for drilling fluid comprises cellulose, humic acid, modified starch, synthetic polymer and the like. Wherein, the good combination of the polymer fluid loss agent and the clay enhances the structural stability of the bentonite. Meanwhile, the addition of some rigid groups increases the temperature resistance of the polymer. The synthesis process is simple, low in cost and widely applicable. The gypsum layer is a good oil-gas covering layer, and nearly 30% of oil-gas covering layers of large oil fields in the world consist of the gypsum layer and salt rocks. The gypsum layer contains a large amount of calcium and sodium ions, which can seriously affect the hydration and the dispersibility of the bentonite and greatly increase the filtration loss of the drilling fluid. Therefore, in the current drilling process of deep wells and ultra-deep wells, the polymer-based water-based drilling fluid treating agent not only needs to overcome the problem of easy degradation at high temperature, but also needs to have good salt resistance and calcium pollution resistance, so that the good performance of the treating agent is maintained. However, much research is currently focused on resistance to sodium ion contamination, and relatively little research has been conducted on fluid loss control under high temperature, high calcium conditions.
The common filtrate reducer for the drilling fluid at present comprises: (1) carboxymethyl cellulose (CMC), a cellulose product represented by CMC, is one of the most widely used fluid loss additives for drilling fluids, which has been used most recently. CMC can be used as an important drilling fluid treating agent because of rich raw material sources, relatively low price and simple and convenient production process. (2) The sulfonated lignite is sulfonated lignite (SMC), the sulfonated lignite has the functions of filtration reduction and dilution, and the sulfonated lignite is mainly characterized by high thermal stability and can effectively control the filtration loss and the viscosity of the fresh water drilling fluid at the high temperature of 200-220 ℃. (3) The polymer is one of the most used fluid loss additives at present, and the development speed is higher. The polymer is mainly acrylic acid and acrylamide copolymer.
The main chain of CMC molecules is connected by ether bonds, the temperature resistance of the CMC molecule in drilling fluid can only reach 130-140 ℃, and the high valence ion pollution resistance and salt resistance of the CMC molecule are limited, so the CMC molecule is limited to be applied in a wider range. SMC has the disadvantage of poor salt resistance at high temperatures. The common acrylamide polymer fluid loss agent has weak temperature and salt resistance.
Disclosure of Invention
The invention aims to overcome the defect that the existing fluid loss additive cannot have good temperature resistance and calcium resistance, and provides a nano-silica graft copolymer which has good temperature resistance and calcium resistance and is suitable for fluid loss reduction, a preparation method and application thereof, and drilling fluid and application thereof.
In order to achieve the above object, the present invention provides, in a first aspect, a nanosilica graft copolymer characterized in that the copolymer contains one or more of the structural units represented by the following formula (1), one or more of the structural units represented by the formula (2), one or more of the structural units represented by the formula (3), and one or more of the structural units represented by the formula (4):
wherein R is1Is C0-C6 alkylene; r1'And R1”Each independently H and C1-C6 alkyl; r2、R3And R4Each independently selected from H and C1-C6 alkyl; r2'And R2”Each independently H and C1-C6 alkyl; r3'And R3”Each independently H and C1-C6 alkyl; r4'And R4”Each independently H and C1-C6 alkyl; r5And R6Each independently is a C1-C6 alkylene group; m is H and an alkali metal element; a is silicon dioxide nanoParticles.
In a second aspect, the present invention provides a method for preparing a nanosilicon dioxide graft copolymer, comprising: copolymerizing a compound represented by the formula (1-a), a compound represented by the formula (2-a), a compound represented by the formula (3-a) and a compound represented by the formula (4-a) in a water-containing solvent in the presence of a redox initiator;
wherein R is1Is C0-C6 alkylene; r1'And R1”Each independently H and C1-C6 alkyl; r2、R3And R4Each independently selected from H and C1-C6 alkyl; r2'And R2”Each independently H and C1-C6 alkyl; r3'And R3”Each independently H and C1-C6 alkyl; r4'And R4”Each independently H and C1-C6 alkyl; r5And R6Each independently is a C1-C6 alkylene group; m is H and an alkali metal element; a is silica nano-particles.
In a third aspect, the invention provides a nano-silica graft copolymer prepared by the above preparation method.
In a fourth aspect, the present invention provides the use of the nanosilica graft copolymer of the present invention as a fluid loss additive in a drilling fluid.
In a fifth aspect, the invention provides a drilling fluid containing the nanosilica graft copolymer of the invention as a fluid loss additive.
In a sixth aspect, the present invention provides the use of a drilling fluid in oil and gas drilling.
Through the technical scheme, the invention has the following beneficial effects.
(1) The nano silicon dioxide graft copolymer (M-PAAN) provided by the invention has an excellent fluid loss reducing effect, has an excellent fluid loss reducing effect in fresh water-based drilling fluid within a temperature range of 20-200 ℃, particularly a high-temperature fluid loss reducing effect, and the API (American Petroleum institute) fluid loss of base slurry after aging for 16 hours at 200 ℃ is only 8 ml.
(2) The M-PAAN provided by the invention has obvious calcium ion pollution resistance at the temperature of 170-180 ℃. When 2 weight percent of M-PAAN is added into 2 weight percent of calcium-polluted base slurry, the API fluid loss is reduced from 188ml to 6ml, and the fluid loss reducing effect is obvious.
(3) The M-PAAN provided by the invention performs graft copolymerization on the polymer and the nano material, not only highlights the improvement of the stability of the polymer to the structure of clay particles, but also combines the temperature resistance of the nano material, so that the nano silicon dioxide graft copolymer has excellent fluid loss reduction effect at high temperature and has good calcium pollution resistance.
Drawings
FIG. 1 shows the aging temperatures of 2% by weight of copolymer A1 and 1% by weight of CaCl2The particle size of the base slurry of (1).
Fig. 2 is an XRD pattern of each sample before aging, where a: base slurry, B: base stock + 2% by weight of copolymer a1, C: base slurry + 1% by weight of CaCl2D, D: base syrup + 2% by weight copolymer A1+ 1% by weight CaCl2。
Fig. 3 is an XRD pattern of each sample after aging at 180 ℃, where a: base slurry, B: base stock + 2% by weight of copolymer a1, C: base slurry + 1% by weight of CaCl2D, D: base syrup + 2% by weight copolymer A1+ 1% by weight CaCl2。
A in FIG. 4 is a TEM image of 2% by weight of copolymer A1 in deionized water after aging at 180 ℃ for 16 hours; b in FIG. 4 is a TEM image of the binder after aging at 180 ℃ for 16 hours; c in FIG. 4 is 2% by weight CaCl after aging at 180 ℃ for 16 hours2A TEM image of the base slurry of (a); d in FIG. 4 is 2% by weight CaCl after aging at 180 ℃ for 16 hours2And 2 wt% copolymer a 1; d1 in FIG. 4 is a TEM image of the clear copolymer A1 structure under condition d in FIG. 4; d2 in FIG. 4 is a TEM image of the structure of the enlarged copolymer A1.
In FIG. 5, a is a copolymer A1 containing 2% by weight of copolymer A1 and 2% by weight of CaCl2SEM image (3000 magnification) of the filter cake after aging of the base slurry at 150 ℃; in FIG. 5 b is a copolymer A1 containing 2% by weight of copolymer A1 and 2% by weight of CaCl2SEM image (3000 x magnification) of the filter cake after aging of the base slurry at 180 ℃.
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
One aspect of the present invention provides a nanosilica graft copolymer (hereinafter also simply referred to as a copolymer) containing one or more of the structural units represented by the following formula (1), one or more of the structural units represented by the formula (2), one or more of the structural units represented by the formula (3), and one or more of the structural units represented by the formula (4):
wherein R is1Is C0-C6 alkylene; r1'And R1”Each independently H and C1-C6 alkyl; r2、R3And R4Each independently selected from H and C1-C6 alkyl; r2'And R2”Each independently H and C1-C6 alkyl; r3'And R3”Each independently H and C1-C6 alkyl; r4'And R4”Each independently H and C1-C6 alkyl; r5And R6Each independently is a C1-C6 alkylene group; m is H and an alkali metal element; a is silica nano-particles.
According to the present invention, the alkyl group having 1 to 6 may be, for example, a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a n-pentyl group, an isopentyl group, a n-hexyl group, etc.
The alkylene group having C0 to C6 may be, for example, an alkylene group formed of an alkylene group having C0 and an alkyl group having C1 to C6, wherein the alkylene group having C0 may be considered to be directly connected to each other at both ends of the alkylene group, and the alkylene group having C0 may be considered to be present or absent as a connecting bond.
According to the invention, R is preferably1Is C0-C4 alkylene; r1'And R1”Each independently H and C1-C4 alkyl; r2、R3And R4Each independently selected from alkyl groups of H, C1-C4; r2'And R2”Each independently H and C1-C4 alkyl; r3'And R3”Each independently H and C1-C4 alkyl; r4'And R4”Each independently H and C1-C4 alkyl; r5And R6Is C2-C6 alkylene; m is H, Li, Na and K; a is silica nano-particles.
More preferably, R1Is alkylene of C0, -CH2-、-CH2-CH2-or-CH2-CH2-CH2-；R1'And R1”Each independently is H, methyl, ethyl, and propyl; r2、R3And R4Each independently selected from H, methyl and ethyl; r2'And R2”Each independently is H, methyl, ethyl, and propyl; r3'And R3”Each independently is H, methyl, ethyl, and propyl; r4'And R4”Each independently is H, methyl, ethyl, and propyl; r5And R6is-CH2-CH2-、-CH2-CH2-CH2-、-CHCH3-CH2-、-CH2-CH2-CH2-CH2-、-C(CH3)2-CH2-、-CH2-C(CH3)2-or-CH2-CHCH3-CH2-; m is H and Na; a is silica nano-particles.
In a preferred embodiment of the invention, R2、R3And R4Is H.
According to the present invention, the particle size of the silica nanoparticles may be in the nanometer level, and preferably, the particle size of the silica nanoparticles is 10 to 50nm, preferably 20 to 30 nm.
According to the present invention, it is preferable that the copolymer has a molar ratio of the structural unit represented by formula (1), the structural unit represented by formula (2), the structural unit represented by formula (3), and the structural unit represented by formula (4) of 1: 0.3-0.35: 0.5-0.6: 0.05-0.06. In order to obtain a copolymer having more excellent properties, it is more preferable that the molar ratio of the structural unit represented by formula (1), the structural unit represented by formula (2), the structural unit represented by formula (3), and the structural unit represented by formula (4) is 1: 0.3-0.32: 0.51-0.55: 0.055 to 0.057, particularly preferably 1: 0.3-0.32: 0.51-0.55: 0.055.
according to the invention, the viscosity-average molecular weight of the above-mentioned copolymers is 2.40 × 105～2.75×105The g/mol range is selected from the viewpoint of improving the temperature resistance, salt resistance and fluid loss properties of the resulting copolymer, and preferably the viscosity average molecular weight of the copolymer is 2.42 × 105～2.67×105g/mol, more preferably 2.44 × 105～2.65×105g/mol。
According to the present invention, the silica graft copolymer contains a structural unit represented by formula (1), a structural unit represented by formula (2), a structural unit represented by formula (3), and a structural unit represented by formula (4), and is particularly preferably a linear random copolymer composed of a structural unit represented by formula (1), a structural unit represented by formula (2), a structural unit represented by formula (3), and a structural unit represented by formula (4).
According to another aspect of the present invention, there is provided a method for preparing a nano silica graft copolymer, the method comprising: copolymerizing a compound represented by the formula (1-a), a compound represented by the formula (2-a), a compound represented by the formula (3-a) and a compound represented by the formula (4-a) in a water-containing solvent in the presence of a redox initiator;
wherein R is1Is C0-C6 alkylene; r1'And R1”Each independently H and C1-C6 alkyl; r2、R3And R4Each independently selected from H and C1-C6 alkyl; r2'And R2”Each independently H and C1-C6 alkyl; r3'And R3”Each independently H and C1-C6 alkyl; r4'And R4”Each independently H and C1-C6 alkyl; r5And R6Each independently is a C1-C6 alkylene group; m is H and an alkali metal element; a is silica nano-particles.
According to the present invention, the compound represented by the above formula (1-a), the compound represented by the formula (2-a), the compound represented by the formula (3-a), the compound represented by the formula (4-a), and each group related thereto may be specifically selected according to the structural unit represented by the above formula (1), the structural unit represented by the above formula (2), the structural unit represented by the above formula (3), and the structural unit represented by the above formula (4), respectively.
Specific examples of the compound represented by the above formula (1-a) may include, for example, one or more compounds represented by the following formula:
formula (1-a-1): r1Being alkylene of C0, R1'And R1”Are all H (also known as acrylamide);
formula (1-a-2): r1Being alkylene of C0, R1'Is methyl, R1”Is H (also known as methacrylamide);
formula (1-a-3): r1is-CH2-，R1'And R1”Are all H.
Specific examples of the compound represented by the above formula (2-a) may include, for example, compounds represented by the following formula:
formula (2-a-1): r2、R3And R4Is H, R2'And R2”Are all H (N-vinylpyrrolidone).
Specific examples of the compound represented by the above formula (3-a) may include, for example, one or more compounds represented by the following formula:
formula (3-a-1): r5is-C (CH)3)2-CH2-，R3'And R3”Is H, M is H (2-acrylamido-2-methylpropanesulfonic acid)Acid);
formula (3-a-2): r5is-C (CH)3)2-CH2-，R3'And R3”Is H, M is Na (2-acrylamido-2-methylpropanesulfonic acid);
formula (3-a-3): r5is-C (CH)3)2-CH2-，R3'Is methyl, R3”Is H, M is H (2-methacrylamido-2-methylpropanesulfonic acid);
formula (3-a-4): r5is-C (CH)3)2-CH2-，R3'Is methyl, R3”Is H, and M is Na (sodium 2-methacrylamido-2-methylpropanesulfonate).
Specific examples of the compound represented by the above formula (4-a) may include, for example, compounds represented by the following formula:
formula (3-a-1): r6is-CH2-CH2-CH2-，R4'And R4”Is H.
According to the present invention, the compound represented by the above formula (1-a), the compound represented by the formula (2-a), the compound represented by the formula (3-a) and the compound represented by the formula (4-a) may be used in a molar ratio of 1: 0.3-0.35: 0.5-0.6: 0.05 to 0.06, in order to obtain a copolymer having more excellent properties, it is preferable that the compound represented by the above formula (1-a), the compound represented by the formula (2-a), the compound represented by the formula (3-a) and the compound represented by the formula (4-a) are used in a molar ratio of 1: 0.3-0.32: 0.51-0.55: 0.055 to 0.057, particularly preferably 1: 0.3-0.32: 0.51-0.55: 0.055.
according to the present invention, preferably, the copolymerization is such that the viscosity-average molecular weight of the resulting copolymer is 2.40 × 105～2.75×105g/mol, preferably 2.42 × 105～2.67×105More preferably, g/mol is 2.44 × 105～2.65×105g/mol。
According to the present invention, the aqueous solvent may be water or a mixture of water and other solvents (for example, methanol, ethanol, propanol, etc.) which do not affect the copolymerization reaction of the present invention. The amount of the aqueous solvent to be used may be suitably adjusted depending on the desired molecular weight of the copolymer, and it is preferable that the total content of the compound represented by the formula (1-a), the compound represented by the formula (2-a), the compound represented by the formula (3-a) and the compound represented by the formula (4-a) is 15 to 35% by weight, more preferably 20 to 30% by weight, for example 20 to 25% by weight, based on the total weight of the aqueous solvent, the compound represented by the formula (1-a), the compound represented by the formula (2-a), the compound represented by the formula (3-a) and the compound represented by the formula (4-a).
According to the present invention, the polymerization of the above-mentioned monomer of the present invention is initiated by using a redox initiator system, and the type of the redox initiator system is not particularly limited in the present invention, and various redox initiator systems conventionally used in the art can be used. Preferably, the oxidant in the redox initiator is one or more of ammonium persulfate, potassium persulfate, sodium persulfate, hydrogen peroxide, sodium hypochlorite, potassium permanganate, potassium perborate and sodium perborate, preferably one or more of ammonium persulfate, potassium persulfate and sodium persulfate. Preferably, the reducing agent in the redox initiator is one or more of sodium bisulfite, potassium sulfite, sodium thiosulfate, potassium thiosulfate, sodium sulfide and hydrogen sulfide, preferably sodium bisulfite and/or potassium sulfate. In order to be able to better initiate obtaining the copolymer required by the present invention, it is preferable that the redox initiator has a molar ratio of the oxidizing agent to the reducing agent of 1: 0.5-2, preferably 1: 0.5-1.3, more preferably 1: 0.6-0.8.
According to the present invention, the amount of the redox initiator to be used may be suitably adjusted depending on the desired molecular weight of the copolymer, and is preferably 0.05 to 2% by weight, preferably 0.2 to 1% by weight, more preferably 0.2 to 0.5% by weight, based on the total weight of the compound represented by formula (1-a), the compound represented by formula (2-a), the compound represented by formula (3-a) and the compound represented by formula (4-a).
According to the present invention, it is preferred that the conditions of the copolymerization reaction include: the pH value is 7-8, the temperature is 50-70 deg.C, and the time is 3-8h (preferably 4-7 h). The pH of the reaction system may be adjusted by using an acid and a base which are conventional in the art, and the reaction system provided by the above-mentioned monomers is generally acidic, and for this purpose, an alkali metal hydroxide (e.g., sodium hydroxide, potassium hydroxide, etc.) may be used.
According to the invention, before the copolymerization reaction, the reaction system is further deoxidized, so as to keep the activity of the redox initiator used in the invention, for example, a non-active gas (one or more of nitrogen, helium, neon, argon and the like) is introduced, and the introducing time can be 10-60min, for example.
In a preferred embodiment of the present invention, the method comprises: mixing the compound shown in the formula (1-a), the compound shown in the formula (2-a), the compound shown in the formula (3-a), the compound shown in the formula (4-a) and a water-containing solvent, adjusting the pH value to 8-9, introducing an inactive gas to remove oxygen, and introducing a redox initiator to carry out copolymerization reaction when the temperature reaches the copolymerization reaction temperature.
According to the invention, in order to be able to obtain the copolymer of the invention in solid form, the process further comprises: drying the product of the free radical polymerization reaction. The conditions for this drying may include, for example: the temperature is 50-100 ℃ and the time is 20-60 h. The drying method is not particularly limited, and various drying methods which are conventional in the art, such as an oven drying method, a freeze drying method, and a spray drying method, can be used.
The invention also provides the copolymer prepared by the method. Although the present invention is not particularly limited, the copolymer may be considered as one of the copolymers described above, or a mixture of a plurality of copolymers. It will of course be understood that the copolymer produced by the above process is generally the direct product of the above process without purification (or after drying only as described hereinbefore), and that the present invention includes such cases within the scope of the invention, although such products may be mixtures of polymers.
The invention also provides the application of the copolymer or the copolymer prepared by the method as a fluid loss additive in drilling fluid.
The invention also provides a drilling fluid containing the copolymer as a fluid loss additive.
According to the invention, the copolymer is used as a fluid loss agent applied to drilling fluid, the copolymer is a polymer-coated nano silica microsphere in a water solution, the particle size of the polymer-coated nano silica microsphere is between 200 and 400nm, the copolymer can play an excellent fluid loss reduction effect in water-based drilling fluid, the fluid loss reduction effect is particularly obvious at high temperature, and the temperature resistance can reach 200 ℃. And, the copolymer can be aged at 180 ℃, part of the polymer chains are stretched and form nano SiO2-linear structure of the polymer chain. Exposing a large amount of amide, sulfonic group and cyclic rigid group on the stretched polymer chain, connecting with the clay layer through hydrogen bonds, strengthening the connection between the copolymer and the clay layer, and preventing Ca2+And a large amount of ion exchange with the clay layer. Therefore, it can resist Ca2 +Resulting in weakening of the structural strength of the clay and agglomeration of clay layers. In this case, the particle size distribution of the clay particles is more extensive, some particles with a size of 1-10um are grafted with nano SiO on the polymer chain2Together can block micro-nano holes on the filter cake. At this time, the copolymer can resist 2 weight percent of calcium ion pollution at 180 ℃ of 170 ℃ and the filtration loss is lower than 6ml, so that the copolymer as a fluid loss additive has excellent fluid loss performance and special calcium pollution resistance in water-based drilling fluid at high temperature.
According to the invention, the copolymer is used as a filtrate reducer for drilling fluid, the obtained drilling fluid can still keep lower filtrate loss in a high-temperature and high-calcium environment, can well maintain the stability of a well wall, and is particularly suitable for developing deep and ultra-deep oil gas resources in a high-temperature and high-calcium environment underground. The content of the copolymer is not particularly limited in the present invention, and the amount of the conventional fluid loss additive can be used, and can be adjusted as appropriate according to the conditions of different wells, and the content of the copolymer is preferably 2 to 3 wt% (relative to the total weight of the drilling fluid).
The present invention is not particularly limited to the above-mentioned drilling fluid system according to the present invention, and may be various drilling fluid systems conventional in the art as long as the copolymer of the present invention is added to these conventional drilling fluid systems. As such conventional drilling fluid systems, for example, one or more of potassium chloride-polyalcohol drilling fluids, silicone drilling fluids, and cationic drilling fluids may be mentioned. The potassium chloride-polyalcohol drilling fluid may be various potassium chloride-polyalcohol drilling fluids well known to those skilled in the art, and may be, for example, one or more of a potassium chloride-polyethylene glycol drilling fluid, a potassium chloride-polypropylene glycol drilling fluid, a potassium chloride-ethylene glycol/propylene glycol copolymer drilling fluid, a potassium chloride-polyglycerol drilling fluid, and a potassium chloride-polyethylene glycol drilling fluid; the organosilicon drilling fluid can be various organosilicon drilling fluids well known to those skilled in the art, and the organosilicon in the organosilicon drilling fluid can be one or more selected from sodium methylsiliconate, potassium methylsiliconate and potassium humate. The cationic drilling fluid may be various cationic drilling fluids well known to those skilled in the art, and the cation in the cationic drilling fluid may be one or more selected from the group consisting of 2, 3-epoxypropyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrimethylammonium chloride, and cationic polyacrylamide.
According to the invention, the drilling fluid is preferably a water-based drilling fluid which may contain, in addition to water and the above-mentioned copolymer, other additives as water-based drilling fluids, preferably the drilling fluid of the invention contains one or more of bentonite, viscosifying agents, anti-sloughing agents, lubricants, calcium chloride, sodium carbonate and the like.
The bentonite is a clay mainly composed of montmorillonite, and has the functions of imparting shear strength and fluid loss wall-building property to drilling fluid, and may be, for example, sodium bentonite and/or calcium bentonite, and preferably sodium bentonite. More preferably, the bentonite is present in an amount of 2 to 4 wt%, more preferably 3 to 4 wt%.
The tackifier can improve the viscous shear force of the drilling fluid, and can be one or more of polyacrylamide potassium salt (KPAM), polyanionic cellulose (such as PAC141) and a copolymer of acrylamide and sodium acrylate (such as 80A51), and is preferably polyacrylamide potassium salt. More preferably, the tackifier is present in an amount of 0.2 to 0.5 wt%, more preferably 0.3 to 0.5 wt%.
The anti-collapse agent can assist the bionic shale inhibitor to prevent the well wall from collapsing and improve the stability of the well wall, and can be one or more of potassium humate (KHM), organic silicon (such as with the trademark of GF-1) and sulfonated asphalt (such as with the trademark of FT-1A), and is preferably potassium humate. More preferably, the anti-collapse agent is contained in an amount of 2 to 4 wt%.
The lubricant can improve the lubricating property of the drilling fluid and prevent the drilling of complex conditions in the well, such as drilling sticking, and can be one or more of sulfonated oil foot (such as FK-10), diesel oil and surfactant mixture (such as FRH) and fatty glyceride and surfactant mixture (such as FK-1), and is preferably FK-10. More preferably, the lubricant is present in an amount of 2 to 4 wt.%.
The content of calcium chloride may be, for example, 0.5 to 1% by weight, and the content of sodium carbonate may be, for example, 0.2 to 0.3% by weight.
The above additives may be commercially available or prepared by conventional methods in the art, and are not described herein.
The invention also provides application of the drilling fluid in oil and gas drilling.
The present invention will be described in detail below by way of examples.
In the following examples and comparative examples,
AM: acrylamide, 99% by weight purity, purchased from alatin;
AMPS: 2-acrylamido-2-methyl-1-propanesulfonic acid having a purity of 98% by weight and obtained from alatin;
NVP: n-vinyl pyrrolidone, 99% pure by weight, purchased from alatin;
M-SiO2: methacryloxypropyltrimethoxysilane (KH570) modified nanosilica having a particle size of 20nm and a purity of 99% by weight, available from SAFEN Chemicals, Inc.
The viscosity average molecular weight was measured using an Ubbelohde viscometer.
The X-ray photoelectron spectroscopy was measured by a D8ADVANCE polycrystal X-ray diffractometer in Germany.
Polymer production example 1
10g of AM (0.14mol) and 15g of AMPS (0.07mol) are dissolved thoroughly in 100ml of water, the pH of the solution is adjusted to 8 with sodium hydroxide, and 2g of M-SiO are then added2(0.008mol) was sufficiently stirred to dissolve it. The aqueous solution was transferred to a three-necked reaction flask and 5ml of NVP (0.046mol) was added. And (2) placing the reaction bottle in a constant-temperature water bath kettle at 55 ℃ by adopting a water bath heating mode, stirring at the speed of 300r/min, keeping the temperature for 30 minutes, adding 60mg of ammonium persulfate and 20mg of sodium bisulfite into the solution, carrying out catalytic reaction, and introducing nitrogen gas for protection in the whole reaction process. After 4 hours of reaction, milky viscous liquid is obtained, and the M-PAAN nano silicon dioxide graft copolymer A1 is obtained after drying and crushing in a drying oven at 60 ℃.
Through the analysis and detection of infrared and nuclear magnetic resonance hydrogen spectrum and carbon spectrum, acrylamide, N-vinyl pyrrolidone, 2-acrylamide-2-methyl propanesulfonic acid and M-SiO in the obtained copolymer2The molar ratio of the structural units was 1:0.32:0.51:0.055, and the viscosity-average molecular weight of the copolymer was 2.6 × 105g/mol。
Polymer production example 2
10.5g AM (0.15mol) and 20g AMPS (0.1mol) are dissolved thoroughly in 100ml water, the pH of the solution is adjusted to 8 with sodium hydroxide, and 2g M-SiO are added2(0.008mol) was sufficiently stirred to dissolve it. The aqueous solution was transferred to a three-necked reaction flask and 5ml of NVP (0.046mol) was added. And (2) placing the reaction bottle in a constant-temperature water bath kettle at 55 ℃ by adopting a water bath heating mode, stirring at the speed of 300r/min, keeping the temperature for 30 minutes, adding 60mg of ammonium persulfate and 20mg of sodium bisulfite into the solution, carrying out catalytic reaction, and introducing nitrogen gas for protection in the whole reaction process. After 4 hours of reaction, colorless viscous liquid is obtained, and the M-PAAN nano silicon dioxide graft copolymer A2 is obtained after drying and crushing in a baking oven at 60 ℃.
The obtained copolymer is analyzed and detected by infrared and nuclear magnetic resonance hydrogen spectrum and carbon spectrumAcrylamide, N-vinylpyrrolidone, 2-acrylamido-2-methylpropanesulfonic acid and M-SiO2The molar ratio of the structural units was 1: 0.3: 0.53: 0.055, and the viscosity-average molecular weight of the copolymer was 2.65 × 105g/mol。
Polymer production example 3
10g of AM (0.14mol) and 15g of AMPS (0.07mol) are dissolved thoroughly in 100ml of water, the pH of the solution is adjusted to 8 with sodium hydroxide, and 2g of M-SiO are then added2(0.008mol) was sufficiently stirred to dissolve it. The aqueous solution was transferred to a three-necked reaction flask and 5ml of NVP (0.046mol) was added. And (2) putting the reaction bottle into a constant-temperature water bath kettle at 55 ℃ by adopting a water bath heating mode, stirring at the speed of 300r/min, keeping the temperature for 30 minutes, adding 70mg of ammonium persulfate and 30mg of sodium bisulfite into the solution, carrying out catalytic reaction, and introducing nitrogen gas for protection in the whole reaction process. After 4 hours of reaction, colorless viscous liquid is obtained, and the M-PAAN nano silicon dioxide graft copolymer A3 is obtained after drying and crushing in a baking oven at 60 ℃.
Through the analysis and detection of infrared and nuclear magnetic resonance hydrogen spectrum and carbon spectrum, acrylamide, N-vinyl pyrrolidone, 2-acrylamide-2-methyl propanesulfonic acid and M-SiO in the obtained copolymer2The molar ratio of the structural units was 1:0.32: 0.55: 0.055, and the viscosity-average molecular weight of the copolymer was 2.72 × 105g/mol。
Polymer preparation comparative example 1
The procedure is as in example 3, except that no M-SiO is added2To obtain copolymer D1.
The molar ratio of the structural units provided by acrylamide, N-vinyl pyrrolidone and 2-acrylamido-2-methylpropanesulfonic acid in the obtained copolymer is 1:0.32: 0.55 through the analysis and detection of infrared and nuclear magnetic resonance hydrogen spectrum and carbon spectrum, and the viscosity-average molecular weight of the copolymer is 3.5 × 105g/mol。
Test example 1
The test examples are provided to illustrate the drilling fluids of the present invention and their use.
The basic drilling fluid formula comprises: 1000g of water, 40g of Weichafang Weizhou bentonite (purchased from Shandong Weifang Weizhou bentonite Co., Ltd., the same shall apply hereinafter) and 2.5g of anhydrous sodium carbonate were mixed, stirred at a high speed for 20min, and aged in a closed container at room temperature (about 25 ℃ C.) for 24 hours, to obtain a basic drilling fluid Y.
The apparent viscosity, plastic viscosity, dynamic shear force (YP), medium pressure fluid loss (API) and high temperature high pressure fluid loss (HTHL) of each system were measured before aging, after aging at 140 ℃ for 16 hours and after aging at 200 ℃ for 16 hours, respectively, by adding 2 wt% of the copolymers obtained in the above examples and comparative examples to the base drilling fluid Y, and after cooling to room temperature (about 25 ℃), respectively, and the results are shown in table 1, respectively:
the viscosity is measured by a viscosity measuring instrument-six-speed viscometer, and the calculation method comprises the following steps:
apparent viscosity: mu.sa＝1/2θ600，θ600The number of degrees is 600 revolutions per minute;
plastic viscosity: mu.sp＝θ600-θ300，θ600Is the number of degrees at 600 revolutions/min, theta300At 300 rpm. The plastic viscosity reflects the strength of the internal friction between the suspended solid phase and the liquid phase and inside the continuous liquid phase under the laminar flow condition when the damage and the recovery of the net frame structure in the drilling fluid are in dynamic balance. Higher rock carrying capacity means better rock carrying capacity, but too high increases circulating pressure loss, and causes downhole complex conditions such as pump holding, bit mud pocket and the like.
The dynamic shear force (YP) was measured by a method specified in the national standard GB/T29170-2012 using a van type six-speed viscometer, and YP was 0.5(2 θ)300-θ600) In Pa.
API refers to medium pressure fluid loss, measured in mL using a medium pressure fluid loss gauge according to the method in SY/T5621-93 standard.
TABLE 1
Test example 2
The test examples are provided to illustrate the drilling fluids of the present invention and their use.
The basic drilling fluid formula comprises: water, sodium-based bentonite (purchased from Shandong Fang Weihua bentonite Corp, the same shall apply hereinafter) and sodium carbonate were mixed in accordance with 400: 16: 1, and stirring at a high speed for 20min, and aging in a closed container at room temperature (about 25 ℃) for 24h to obtain the base drilling fluid Y.
The copolymer obtained in the above examples and comparative examples and CaCl were added to the base drilling fluid Y2And the apparent viscosity, plastic viscosity, dynamic shear force (YP) and medium pressure loss (API) of each system were measured before aging, after aging at 80 ℃ for 16 hours and after aging at 180 ℃ for 16 hours, respectively, and after cooling to room temperature (about 25 ℃), and the results are shown in table 2, respectively, wherein:
the viscosity is measured by a viscosity measuring instrument-six-speed viscometer, and the calculation method comprises the following steps:
apparent viscosity: mu.sa＝1/2θ600，θ600The number of degrees is 600 revolutions per minute;
plastic viscosity: mu.sp＝θ600-θ300，θ600Is the number of degrees at 600 revolutions/min, theta300At 300 rpm. The plastic viscosity reflects the strength of the internal friction between the suspended solid phase and the liquid phase and inside the continuous liquid phase under the laminar flow condition when the damage and the recovery of the net frame structure in the drilling fluid are in dynamic balance. Higher rock carrying capacity means better rock carrying capacity, but too high increases circulating pressure loss, and causes downhole complex conditions such as pump holding, bit mud pocket and the like.
The dynamic shear force (YP) was measured by a method specified in the national standard GB/T29170-2012 using a van type six-speed viscometer, and YP was 0.5(2 θ)300-θ600) In Pa.
API refers to medium pressure fluid loss, measured in mL using a medium pressure fluid loss gauge according to the method in SY/T5621-93 standard.
TABLE 2
Note: "/" indicates notTesting; CaCl2In the amount of Ca2+And (6) counting.
Test example 3
The basic drilling fluid formula comprises: water, sodium-based bentonite (purchased from Shandong Fang Weihua bentonite Corp, the same shall apply hereinafter) and sodium carbonate were mixed in accordance with 400: 16: 1, and stirring at a high speed for 20min, and aging in a closed container at room temperature (about 25 ℃) for 24h to obtain the base drilling fluid Y.
Preparation of the aged base slurries at different temperatures, base slurry + 2% by weight of copolymer A1, base slurry + 1% by weight of CaCl2Base stock + 2% by weight of copolymer A1+ 1% by weight of CaCl2Taking a liquid sample for particle size analysis (laser particle sizer, Betterize 2000, Dandong Baite); performing TEM analysis after diluting the liquid by 1000 times; the liquid samples were dried in an oven at 60 ℃ and ground to a powder, and the powder samples were subjected to X-ray diffraction analysis (XRD) (Bruker D8 Advance); the filter cake subjected to the API fluid loss test was analyzed by Scanning Electron Microscopy (SEM) (JSM 7401, japan electronics corporation).
(1) Particle size analysis
FIG. 1 shows a composition comprising 2% by weight of copolymer and 1% by weight of CaCl at different ageing temperatures2The particle size in the drilling fluid. As can be seen from the figure, the particle size was the smallest at 180 ℃ with a median particle size of 54.94 μm, while the particle sizes before and after aging at 150 ℃ and 200 ℃ were 346.1 μm, 303.2 μm and 90.41 μm, respectively. Thus, the particle size of the particles in the calcium-containing drilling fluid after aging at 180 ℃ was the smallest, indicating that the clay particles were the most dispersible at this point, favoring the formation of a dense filter cake.
(2) XRD analysis
X-ray diffraction analysis (XRD) is the most important evidence for analyzing the clay interlayer spacing. The interlamellar spacing of the clay varies with hydration of the clay and intercalation of chemicals. Addition of copolymer A1 and CaCl2The change in the post clay layer spacing is shown in fig. 2 and 3. As can be seen from FIG. 2, the addition of 2% by weight of copolymer A1 at room temperature results in an interlayer spacing d of the bentonite(001)Increased from 1.23nm to 1.26nm, while adding 1 wt.% CaCl2Will d(001)Increasing to 1.48 nm. Calcium ion (Ca)2+) The adsorption on the surface of the clay is obviously increased by d(001). After 2% by weight of copolymer A1 was added to a solution containing 1% by weight of CaCl2In the base slurry of (2), d(001)From 1.48nm to 1.45 nm. As shown in FIG. 3, after aging at 180 ℃ for 16 hours, the base stock containing 2% by weight of copolymer A1, contains 1% by weight of CaCl2And a base stock containing 2% by weight of copolymer A1 and 1% by weight of CaCl2The particle size of the clay in the base slurry is respectively reduced from 1.23, 1.26, 1.48 and 1.45nm to 1.21, 1.39 and 1.29 nm. At high temperatures, the interlayer spacing of the clay decreases due to the disappearance of interlayer water. It can be seen that copolymer A1 contains CaCl2The clay interlayer spacing in the base slurry of (1) was significantly reduced from 1.39nm to 1.29nm, indicating that copolymer A1 blocked Ca2+Adsorption on clay surface reduces Ca2+A phenomenon of agglomeration of clay particles and an enhanced dispersion of clay in an aqueous solution. However, the d of the calcium ion-containing bentonite after addition of copolymer A1 at room temperature(001)There is no significant reduction.
(3) TEM analysis
Results consistent with particle size analysis and XRD analysis were observed by TEM images (fig. 4). From a in FIG. 4, it can be seen that nano SiO is grafted2The stretched polymer chains lead to higher fluid viscosity and lower filtration volume. The transparent clay layers can be seen in b in fig. 4, but after the addition of calcium the clay layers agglomerate (c in fig. 4). When 2% by weight of copolymer A1 was added, the clay layer was in CaCl2Still dispersed well in the presence (d in fig. 4). At this time, more stretched copolymer a1 (d 1 in fig. 4) was observed, and the linear structure was also more pronounced (d 2 in fig. 4). After the structure of copolymer A1 changed from chain entanglement to chain extension, more amide, sulfonic acid and cyclic rigid groups were exposed on the polymer chains. Nano SiO2Good adsorption and hydrogen bonding and other forces between copolymer a1 and clay tightly bond the polymer to the clay, preventing Ca2+And a large amount of ion exchange between clay layers, reducing the agglomeration of clay.
(4) SEM analysis
As shown in a in FIG. 5, it contained 2% by weight of copolymer A1 and 2% by weight of CaCl2After aging the base slurry at 150 ℃ for 16 hours, the filter cake showed "dishing and peaked", indicating that the filter cake was loose. While the filter cake was more dense and smooth after 16 hours of aging at 180 c, as shown in b of fig. 5, indicating that the interaction between copolymer a1 and the clay particles formed a dense film, it is due to the formation of this smooth and dense filter cake that copolymer a1 was effective in reducing fluid loss.
As can be seen from the above analysis, at about 170-2-linear structure of the polymer chain. Exposing a large amount of amide, sulfonic acid group and cyclic rigid group on the stretched polymer chain, connecting with the clay layer through hydrogen bonds, strengthening the connection between the copolymer A1 and the clay layer, and preventing Ca2+And a large amount of ion exchange with the clay layer. Thus, copolymer A1 is effective against Ca2+Resulting in weakening of the structural strength of the clay and agglomeration of clay layers. In this case, the particle size distribution of the clay particles is more extensive, some particles with a size of 1-10um are grafted with nano SiO on the polymer chain2Together can block micro-nano holes on the filter cake.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.
Claims (15)
1. A nano-silica graft copolymer characterized by comprising a structural unit derived from acrylamide, a structural unit derived from N-vinylpyrrolidone, a structural unit derived from 2-acrylamido-2-methyl-1-propanesulfonic acid, and a structural unit derived from methacryloxypropyltrimethoxysilane-modified nano-silica;
wherein the molar ratio of the structural unit from acrylamide, the structural unit from N-vinyl pyrrolidone, the structural unit from 2-acrylamide-2-methyl-1-propane sulfonic acid and the structural unit from methacryloxypropyl trimethoxysilane modified nano-silica is 1:0.32:0.51: 0.055.
2. A method for preparing a nano-silica graft copolymer, the method comprising: in an aqueous solvent, in the presence of a redox initiator, carrying out copolymerization reaction on acrylamide, N-vinyl pyrrolidone, 2-acrylamide-2-methyl-1-propane sulfonic acid and methacryloxypropyl trimethoxy silane modified nano silicon dioxide;
wherein the molar ratio of the usage of the acrylamide, the N-vinyl pyrrolidone, the 2-acrylamide-2-methyl-1-propanesulfonic acid and the methacryloxypropyltrimethoxysilane modified nano-silica is 1:0.32:0.51: 0.055.
3. The method of claim 2, wherein the oxidant in the redox initiator is one or more of ammonium persulfate, potassium persulfate, sodium persulfate, hydrogen peroxide, sodium hypochlorite, potassium permanganate, potassium perborate, and sodium perborate; the reducing agent in the redox initiator is one or more of sodium bisulfite, potassium sulfite, sodium thiosulfate, potassium thiosulfate, sodium sulfide and hydrogen sulfide.
4. The method of claim 3, wherein the redox initiator has a molar ratio of oxidant to reductant of 1: 0.5-2.
5. The method of claim 4, wherein the redox initiator has a molar ratio of oxidant to reductant of 1: 0.5-1.3.
6. The method according to claim 3, wherein the redox initiator is used in an amount of 0.05-2 wt% relative to the total weight of acrylamide, N-vinylpyrrolidone, 2-acrylamido-2-methyl-1-propanesulfonic acid and methacryloxypropyltrimethoxysilane modified nanosilica.
7. The method according to claim 6, wherein the redox initiator is used in an amount of 0.2-1 wt% relative to the total weight of acrylamide, N-vinylpyrrolidone, 2-acrylamido-2-methyl-1-propanesulfonic acid and methacryloxypropyltrimethoxysilane modified nanosilica.
8. The method according to claim 3, wherein the total content of acrylamide, N-vinylpyrrolidone, 2-acrylamido-2-methyl-1-propanesulfonic acid and methacryloxypropyltrimethoxysilane modified nanosilica is from 15 to 35% by weight, based on the total weight of aqueous solvent, acrylamide, N-vinylpyrrolidone, 2-acrylamido-2-methyl-1-propanesulfonic acid and methacryloxypropyltrimethoxysilane modified nanosilica.
9. The method of claim 8, wherein the total amount of acrylamide, N-vinylpyrrolidone, 2-acrylamido-2-methyl-1-propanesulfonic acid, and methacryloxypropyltrimethoxysilane modified nanosilica ranges from 20 to 30 weight percent, based on the total weight of aqueous solvent, acrylamide, N-vinylpyrrolidone, 2-acrylamido-2-methyl-1-propanesulfonic acid, and methacryloxypropyltrimethoxysilane modified nanosilica.
10. The method of claim 3, wherein the conditions of the copolymerization reaction comprise: the pH value is 7-8, the temperature is 50-70 ℃, and the time is 3-8 h.
11. A nanosilica graft copolymer obtainable by the process of any of claims 2 to 10.
12. Use of the nanosilica graft copolymer of claim 1 or 11 as a fluid loss additive in a drilling fluid.
13. A drilling fluid comprising the nanosilica graft copolymer of claim 1 or 11 as a fluid loss additive.
14. The drilling fluid of claim 13, wherein the nanosilica graft copolymer is present in an amount of 0.5-2 wt%.
15. Use of the drilling fluid of claim 13 or 14 in oil and gas drilling.
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