Core-shell structured oil absorbent for cementing under oil-based drilling fluid conditions and its preparation method

Abstract

This invention discloses a core-shell structure oil absorbent for cementing under oil-based drilling fluid conditions and its preparation method. The oil absorbent comprises the following components in parts by weight: 20-25 parts ester monomers, 3-7 parts modified composite materials, 1-5 parts dispersant, 20-25 parts pore-forming agent, 0.5-0.8 parts crosslinking agent, 1.3-1.5 parts initiator, and 50-70 parts water. The oil absorbent of this invention expands after absorbing oil and possesses a certain rigidity, compensating for defects without causing a decrease in the mechanical properties of the cement stone. Furthermore, the addition of this oil absorbent allows the cement stone to meet the low elasticity requirements under multi-stage fracturing conditions, enhancing the elasticity of the cement stone and improving the long-term sealing performance of the cement sheath.

Description

TECHNICAL FIELD

[0001] The present application relates to an oil absorption agent for cementing, in particular to a core-shell structure oil absorption agent for cementing under oil-based drilling fluid conditions and a preparation method thereof. BACKGROUND

[0002] During drilling, due to low displacement efficiency or insufficient performance of the preflush, the oil-based drilling fluid is not completely displaced and remains in the annulus. When the cement slurry contacts the oil-based drilling fluid, the cement slurry is contaminated, the basic properties of the cement slurry are changed, the cement slurry cannot normally set to form a gel structure, and the effect of sealing the formation is affected. On the other hand, under special working conditions, the cement sheath is subjected to multi-stage fracturing, and the defects of the cement sheath caused by mixing the slurry increase, the strength decreases, and the cement sheath is more prone to plastic deformation, resulting in failure of the mechanical integrity of the cement sheath and reduction of the long-term sealing capacity of the cement sheath.

[0003] At present, for cementing under oil-based drilling fluid conditions, the main measure to improve the cementing qualification rate is to improve the performance of the preflush and the displacement efficiency, so that the preflush has the performance of efficiently removing the oil-based drilling fluid.

[0004] At present, there is little research on oil absorption agents that can absorb oil-based drilling fluid to improve the performance of the cement slurry under multi-stage fracturing conditions. Most scholars focus on one performance and do not link the two together. Under specific working conditions, the oil absorption agent still cannot stably play a role. SUMMARY

[0005] The purpose of the present application is to provide a core-shell structure oil absorption agent for cementing under oil-based drilling fluid conditions and a preparation method thereof, which can solve the problem of cement slurry not setting when encountering oil to form defects. The oil absorption agent expands after absorbing oil and has a certain rigidity, which can compensate for the defects without causing a decrease in the mechanical properties of the cement stone. After adding the oil absorption agent, the cement stone can meet the low elasticity required under multi-stage fracturing conditions, enhance the elasticity of the cement stone, and improve the long-term sealing performance of the cement sheath.

[0006] To achieve the above objectives, the present invention provides a core-shell structured oil absorbent for cementing under oil-based drilling fluid conditions. This oil absorbent comprises the following components in parts by weight: 20-25 parts ester monomers, 3-7 parts modified composite material, 1-5 parts dispersant, 20-25 parts pore-forming agent, 0.5-0.8 parts crosslinking agent, 1.3-1.5 parts initiator, and 50-70 parts water; wherein the ester monomers are selected from lauryl methacrylate, butyl methacrylate, methyl methacrylate, dodecyl methacrylate, and methyl methacrylate. The modified composite material is selected from two or more of isooctyl acrylate; the modified composite material is selected from one of hydrophobically modified chitosan or hydrophobically modified cellulose; wherein the hydrophobically modified chitosan and hydrophobically modified cellulose are obtained by treating chitosan and cellulose with a silane coupling agent, respectively; the dispersant is selected from hydrophobically modified fumed silica and / or hydrophobically modified calcium carbonate; wherein the hydrophobically modified fumed silica and hydrophobically modified calcium carbonate are obtained by treating silica and calcium carbonate with a silane coupling agent, respectively.

[0007] The core-shell structured oil absorbent of the present invention has an inorganic nano-dispersant as the shell and a synthetic resin as the core. The modified composite material of the present invention can be interspersed in the oil absorbent particles to increase the specific surface area, while providing channels for oil to enter the oil absorbent and improving the oil absorption efficiency of the oil absorbent.

[0008] Preferably, the hydrophobically modified nano-calcium carbonate is obtained by the following method: adding a silane coupling agent and nano-calcium carbonate to water and reacting at 90°C to obtain hydrophobically modified nano-calcium carbonate; wherein the mass ratio of nano-calcium carbonate, silane coupling agent and water is 25:1:50.

[0009] Preferably, the particle size of the nano-calcium carbonate is 40–80 nm.

[0010] Preferably, in the preparation of the hydrophobically modified nano-calcium carbonate, the reaction is carried out at 90°C for 3 hours.

[0011] Preferably, the hydrophobic modified nano-calcium carbonate is prepared by stirring at 500 r / min.

[0012] Preferably, in the preparation of the hydrophobically modified nano-calcium carbonate, after the reaction is completed, it is cooled to room temperature, washed, dried at 50°C, and ground.

[0013] Preferably, the hydrophobically modified chitosan or hydrophobically modified cellulose is obtained by the following method: adding a silane coupling agent and chitosan or cellulose to water at a ratio of 1:30, reacting at 80°C, and cooling to room temperature after the reaction is completed to obtain hydrophobically modified chitosan or hydrophobically modified cellulose.

[0014] Preferably, the silane coupling agent is hexamethyldisilazane.

[0015] Preferably, in the preparation of the hydrophobically modified chitosan and hydrophobically modified cellulose, the reaction is carried out at 80°C for 3 hours.

[0016] Preferably, the hydrophobic modified chitosan and hydrophobic modified cellulose are prepared by stirring at 500 r / min.

[0017] Preferably, in the preparation of the hydrophobically modified chitosan and hydrophobically modified cellulose, after the reaction is completed, the mixture is cooled to room temperature, the precipitate is filtered out, washed, centrifuged, dried at 50°C, and ground.

[0018] Preferably, the ester monomer is a compound of two or more monomers, and each monomer is used in 5 to 15 parts by weight, and the mass ratio of any one monomer to the total mass of the other monomers is less than or equal to 1:4.

[0019] Preferably, the ester monomer is selected from any one of the following: a combination of lauryl methacrylate and butyl methacrylate, a combination of methyl methacrylate and butyl methacrylate, a combination of methyl methacrylate, butyl methacrylate and lauryl methacrylate, a combination of methyl methacrylate, butyl methacrylate and dodecyl methacrylate, and lauryl methacrylate and isooctyl methacrylate.

[0020] Preferably, the ester monomers are selected from any one of the following: a combination of lauryl methacrylate and butyl methacrylate in a mass ratio of 10:13; a combination of methyl methacrylate and butyl methacrylate in a mass ratio of 5:7; a combination of methyl methacrylate, butyl methacrylate and lauryl methacrylate in a mass ratio of 1:1:1; a combination of methyl methacrylate, butyl methacrylate and dodecyl methacrylate in a mass ratio of 1:2:2; and a combination of lauryl methacrylate and isooctyl methacrylate in a mass ratio of 2:3.

[0021] Preferably, the weight fraction of the dispersant should be less than or equal to 0.1 times the weight fraction of water to ensure uniform dispersion in the solution.

[0022] Preferably, the oil absorbent comprises the following components in parts by weight:

[0023] 20-25 parts ester monomers, 3-7 parts modified composite material, 2-4 parts dispersant, 23-25 ​​parts pore-forming agent, 0.5-0.8 parts crosslinking agent, 1.3-1.5 parts initiator and 50-70 parts water.

[0024] Preferably, the pore-forming agent is selected from any one or more of ethyl acetate, anhydrous ethanol, and isobutanol. The purpose of the pore-forming agent is to increase the specific surface area of ​​the oil absorbent after dispersion, and to control the particle size of the oil absorbent between 1 and 100 nm in combination with dispersants of different sizes and processes (stirring rate, etc.).

[0025] Preferably, the crosslinking agent is selected from divinylbenzene.

[0026] Preferably, the initiator is benzoyl peroxide.

[0027] Another object of the present invention is to provide a method for preparing a core-shell structured oil absorbent for cementing under oil-based drilling fluid conditions, the method comprising the following steps:

[0028] (1) Water, modified composite material and dispersant are stirred and dispersed to obtain inorganic dispersion; ester monomer, crosslinking agent, initiator and pore-forming agent are mixed evenly under magnetic stirrer to obtain organic mixture;

[0029] (2) The inorganic dispersion is kept at 75°C and stirred, while the organic mixture is added dropwise to the inorganic dispersion. After the addition is complete, the reaction is carried out.

[0030] (3) After the reaction is complete, filter the product, wash and dry it to obtain the core-shell structure oil absorbent for cementing under oil-based drilling fluid conditions.

[0031] Preferably, in step (1), water and dispersant are stirred at high speed at 800-1300 r / min for 3-5 hours to fully disperse them. Depending on the degree of dispersion of the hydrophobic dispersant, a speed of 800-1300 r / min is selected to disperse the dispersion. The lower the particle size of the dispersant, the higher the speed and the longer the dispersion time are required. When the dispersant and water present a uniform white turbid liquid, the dispersion is complete.

[0032] Preferably, in step (2), the inorganic dispersion is kept at a constant temperature of 75-85°C and stirred at a speed of 300-500 r / min, while the organic mixture is slowly added dropwise to the inorganic dispersion at a rate of 2-5 mL / min, and the reaction is carried out for 2-3 hours after the addition is completed.

[0033] Preferably, the product is dried at 50°C for 24 hours.

[0034] The present invention relates to a core-shell structured oil absorbent for cementing under oil-based drilling fluid conditions and its preparation method, which solves the problem of cement slurry failing to solidify and forming defects when encountering oil, and has the following advantages:

[0035] (1) In order to better improve the oil absorption stability of cement stone and the elasticity required by cement under fracturing conditions, the present invention designs a core-shell type oil absorbent coated with an inorganic dispersant. The shell is an inorganic nano dispersant and the core is a synthetic resin. The inorganic material used as the outer shell can improve the adhesion of oil-absorbing small molecule particles to cement and their dispersibility in cement. Therefore, the synthetic resin has strong adhesion to cement and stable performance. The oil absorbent also has the functions of reducing the elastic modulus of cement stone and eliminating local defects in cement stone caused by oil-based drilling fluid pollution.

[0036] (2) Under oil-based drilling fluid conditions, large oil droplets in some areas of the cement sheath after cementing prevent the cement sheath from setting properly, thus affecting its sealing effect. The oil absorbent of this invention can absorb the large oil droplets agglomerated in the cement slurry. Due to the controlled oil absorption ratio of the oil absorbent, it can be ensured that the oil absorbent particles do not change significantly after oil absorption, which is beneficial for absorbing and dispersing the large oil droplets agglomerated inside the cement slurry into small particles. After cement sets, it helps to reduce the large local defects in the cement sheath caused by oil phase aggregation.

[0037] (3) The hydrophobic core-shell structure design of the present invention makes it easier for the oil absorbent to disperse in the cement slurry and improves the adhesion between the oil absorbent and the cement stone; the shell design not only facilitates dispersion, but also encapsulates the oil absorbent, providing a certain degree of protection. In complex environments, the structure of the oil absorbent is not easily destroyed, thus improving the durability of the oil absorbent.

[0038] (4) The oil absorbent of the present invention is a low elastic modulus material, which can reduce the elastic modulus of cement stone. After oil absorption, the elastic modulus is further reduced. As elastic particles, it is dispersed in the cement stone matrix. By reducing defects, the elastic modulus of cement stone is reduced, turning harm into benefit and improving the long-term sealing integrity of cement sheath under oil-bearing complex formation conditions (such as multi-stage fracturing after cementing of shale gas and shale oil). Attached Figure Description

[0039] Figure 1 The SEM microstructure of the oil absorbent in Example 2 of this invention is shown below; (A) scale bar 200 μm; (B) scale bar 10 μm.

[0040] Figure 2 The images show the morphology of the oil absorbent before (left) and after (right) oil absorption in Example 2 of this invention.

[0041] Figure 3 The infrared spectrum of the oil absorbent in Example 2 of this invention is shown.

[0042] Figure 4 This is the thermogravimetric curve of the oil absorbent in Example 2 of the present invention. Detailed Implementation

[0043] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] The present invention discloses a core-shell structured oil absorbent for cementing under oil-based drilling fluid conditions. The oil absorbent comprises the following components in parts by weight: 20-25 parts ester monomers, 3-7 parts modified composite material, 1-5 parts dispersant, 20-25 parts pore-forming agent, 0.5-0.8 parts crosslinking agent, 1.3-1.5 parts initiator, and 50-70 parts water; wherein the ester monomers are selected from lauryl methacrylate, butyl methacrylate, methyl methacrylate, dodecyl methacrylate, and isooctyl methacrylate. Two or more of the following are selected: the modified composite material is selected from hydrophobically modified chitosan or hydrophobically modified cellulose; wherein the hydrophobically modified chitosan and hydrophobically modified cellulose are obtained by treating chitosan and cellulose with a silane coupling agent, respectively; the dispersant is selected from hydrophobically modified fumed silica and / or hydrophobically modified calcium carbonate; wherein the hydrophobically modified fumed silica and hydrophobically modified calcium carbonate are obtained by treating silica and calcium carbonate with a silane coupling agent, respectively.

[0045] Regarding the aforementioned ester monomers, this application screened a large number of ester monomers and obtained several ester monomers with high oil absorption ratios and oil absorption expansion ratios of approximately 3 to 5 times. Subsequently, compounding experiments with different gradient ratios were conducted to study the effect of different monomer ratios on the oil absorption ratio. Under the condition that other components and their contents are the same, the effect of monomer ratios on the oil absorption ratio is shown in Table 1 below.

[0046] Table 1. Effects of different monomer combinations and their ratios on oil absorption ratio.

[0047]

[0048]

[0049] Note: Monomers 1, 2 and 3 correspond to methyl methacrylate, butyl methacrylate and lauryl methacrylate, respectively.

[0050] The monomers selected in the above experiments were methyl methacrylate, butyl methacrylate, and lauryl methacrylate. That is, in the compound monomers, the ratio of two or three of them should not be too different. When the ratio difference is too large, the experimental results show that the oil absorption ratio gradually decreases. Therefore, in the invention, the compound ratio of the oil-absorbing monomers should be small (less than 1:4).

[0051] The following examples, comparative examples, and experimental examples provide a detailed description of the core-shell structure oil absorbent for cementing under oil-based drilling fluid conditions provided by the present invention.

[0052] Example 1

[0053] A core-shell structured oil absorbent for cementing under oil-based drilling fluid conditions, comprising the following components in parts by weight: 23 parts ester monomers (10 parts lauryl methacrylate and 13 parts butyl methacrylate), 2 parts hydrophobically modified fumed silica nanoparticles (as a dispersant), 3 parts modified chitosan (as a modified composite material), 23 parts ethyl acetate (as a pore-forming agent), 0.5 parts divinylbenzene (as a crosslinking agent), 1.3 parts benzoyl peroxide (as an initiator), and 50 parts water.

[0054] Among them, the hydrophobically modified fumed nano silica is obtained by deep processing of hydrophilic nano silica with HMDS (hexamethyldisilazane), and can be purchased directly from Hubei Huifu Nanomaterials Co., Ltd.

[0055] The preparation method of the core-shell structure oil absorbent for cementing under the above-mentioned oil-based drilling fluid conditions includes:

[0056] (1) Water, hydrophobic modified fumed silica and modified chitosan were stirred at high speed at 1000 r / min for 5 h to fully disperse them and obtain an inorganic dispersion; ester monomers, crosslinking agent, initiator and pore-forming agent were mixed evenly under magnetic stirrer to obtain an organic mixture; wherein, the hydrophobic modified chitosan was obtained by the following method: silane coupling agent and chitosan were added to deionized water, the mass ratio of silane coupling agent, chitosan and water was 1:30:150, and the reaction was carried out at 80℃. After the reaction was completed, the mixture was cooled to room temperature to obtain hydrophobic modified chitosan powder;

[0057] (2) Place the above inorganic dispersion in a constant temperature water bath and heat it to 75°C by stirring at a speed of 300 r / min. At the same time, slowly add the above organic mixture to the inorganic dispersion by a peristaltic pump at a rate of 2 mL / min. After the addition is complete, react for 2 h.

[0058] (3) After the reaction is complete, filter the product, wash it, and dry it at 50°C for 24 hours. The dried product is a white powdery and flocculent solid mixture.

[0059] Example 2

[0060] A core-shell structured oil absorbent for cementing under oil-based drilling fluid conditions, comprising the following components in parts by weight: 24 parts ester monomers (10 parts methyl methacrylate and 14 parts butyl methacrylate), 2.5 parts hydrophobically modified fumed silica nanoparticles (as a dispersant), 5 parts hydrophobically modified chitosan (as a modified composite material), 24 parts ethyl acetate (as a pore-forming agent), 0.8 parts divinylbenzene (as a crosslinking agent), 1.5 parts benzoyl peroxide (as an initiator), and 60 parts water.

[0061] The preparation method of the core-shell structure oil absorbent for cementing under the above-mentioned oil-based drilling fluid conditions is basically the same as that in Example 1, except that:

[0062] In step (1), water, hydrophobically modified fumed silica and hydrophobically modified chitosan are stirred at high speed at 1200 r / min for 3 h to fully disperse them;

[0063] In step (2), the organic mixture is added dropwise to the inorganic dispersion and reacted for 2.5 hours.

[0064] The obtained product is a white powdery solid, such as Figure 1 The image shows the SEM microstructure of the oil absorbent in Example 2 of this invention; (A) scale bar 200 μm; (B) scale bar 10 μm. Figure 2 The image shows the morphology of the oil absorbent before (left) and after (right) oil absorption in Example 2 of the present invention.

[0065] like Figure 3 The image shown is the infrared spectrum of the oil absorbent in Example 2 of this invention. The oil absorbent contains 3436 cm⁻¹. -1 The peak represents the stretching vibration of -OH, at 2959 cm⁻¹. -1 The peaks are for the stretching vibrations of -CH2 and -CH3, at 1732 cm⁻¹. -1 This is the stretching vibration peak of -C=O. 1632 cm⁻¹ -1 The peaks for -C=C- are due to stretching vibrations. The peaks for -C=O and -C=C- are very weak, indicating that a significant number of monomers have participated in the reaction. (809 cm⁻¹) -1 The absorption peak of -(CH2)n represents the absorption peak of -(CH2)3 in butyl methacrylate; the peak intensity and characteristic peaks show that the C=O and C=C have low intensity and have participated more in the polymerization reaction, forming the target product oil absorbent.

[0066] like Figure 4 The figure shows the thermogravimetric curve of the oil absorbent in Example 2 of the present invention. The mass loss at 147°C represents the decomposition of bound water in the sample, the mass loss at 287°C represents the mass loss of -OH in the sample, the mass loss at 347°C represents the mass loss of O atoms in -C=O or SiO2, and the mass loss at 400°C represents the oxidative weight loss of C atoms in -CH2- and -CH3.

[0067] Example 3

[0068] A core-shell structured oil absorbent for cementing under oil-based drilling fluid conditions, the specific formulation of which is as follows: 24 parts ester monomers (8 parts methyl methacrylate, 8 parts butyl methacrylate and 8 parts lauryl methacrylate), 4 parts hydrophobically modified fumed silica nanoparticles (as dispersant), 7 parts modified chitosan (as modified composite material), 25 parts ethyl acetate (as pore-forming agent), 0.5 parts divinylbenzene (as crosslinking agent), 1.5 parts benzoyl peroxide (as initiator) and 70 parts water.

[0069] The preparation method of the core-shell structure oil absorbent for cementing under the above-mentioned oil-based drilling fluid conditions is basically the same as that in Example 1, except that:

[0070] In step (1), water, hydrophobically modified bio-nano silica and hydrophobically modified chitosan are stirred at high speed at 1300 r / min for 3 h to fully disperse them;

[0071] In step (2), the stirring speed is set to 500 r / min and the temperature is heated to 85°C; the organic mixture is added dropwise to the inorganic dispersion and reacted for 3 hours.

[0072] The obtained product is a white powdery solid.

[0073] Example 4

[0074] A core-shell structure oil absorbent for cementing under oil-based drilling fluid conditions, the specific formulation of which is as follows: 25 parts ester monomers (5 parts methyl methacrylate, 10 parts butyl methacrylate and 10 parts dodecyl methacrylate), 2 parts hydrophobically modified nano-calcium carbonate (as dispersant), 5 parts modified cellulose (as modified composite material), 23 parts ethyl acetate (as pore-forming agent), 0.5 parts divinylbenzene (as crosslinking agent), 1.3 parts benzoyl peroxide (as initiator) and 50 parts water.

[0075] The preparation method of hydrophobically modified nano-calcium carbonate is as follows:

[0076] Nano-calcium carbonate with a particle size of 40-80 nm (available from Xianfeng Nano Co., Ltd.) and silane coupling agent (HMDS) are added to distilled water at a mass ratio of 25:1:50. The mixture is reacted in a water bath at 90°C for 3 hours at 500 RPM. After the reaction is complete, the mixture is cooled to room temperature, filtered, and the filter cake is washed 3-5 times with distilled water. The cake is then dried in a 50°C oven and ground to obtain hydrophobically modified nano-calcium carbonate.

[0077] The preparation method of the core-shell structure oil absorbent for cementing under the above-mentioned oil-based drilling fluid conditions is basically the same as that in Example 1, except that:

[0078] In step (1), water, hydrophobically modified nano-calcium carbonate and hydrophobically modified cellulose are stirred at high speed of 800 r / min for 3 h to fully disperse them; wherein, the preparation method of hydrophobically modified cellulose is the same as the preparation method of hydrophobically modified chitosan, except that chitosan is replaced with cellulose.

[0079] In step (2), the stirring speed is set to 500 r / min and the temperature is heated to 80°C. The organic mixture is slowly added to the inorganic dispersion at a rate of 5 mL / min using a peristaltic pump, and the reaction is carried out for 3 hours after the addition is completed.

[0080] The obtained product is a pale yellow powdery solid.

[0081] Example 5

[0082] A core-shell structured oil absorbent for cementing under oil-based drilling fluid conditions, the specific formulation of which is as follows: 25 parts ester monomers (10 parts lauryl methacrylate and 15 parts isooctyl methacrylate), 2.5 parts hydrophobically modified nano-calcium carbonate (as a dispersant), 7 parts hydrophobically modified cellulose (as a modified composite material), 25 parts ethyl acetate (as a pore-forming agent), 0.5 parts divinylbenzene (as a crosslinking agent), 1.5 parts benzoyl peroxide (as an initiator) and 70 parts water.

[0083] The preparation method of the core-shell structure oil absorbent for cementing under the above-mentioned oil-based drilling fluid conditions is basically the same as that in Example 1, except that:

[0084] In step (1), water, hydrophobically modified nano-calcium carbonate and hydrophobically modified cellulose are stirred at high speed of 800 r / min for 3 h to fully disperse them;

[0085] In step (2), the stirring speed is set to 500 r / min and the temperature is heated to 80°C. The mixture is slowly added dropwise to the inorganic dispersion at a rate of 5 mL / min using a peristaltic pump. After the addition is complete, the reaction is carried out for 3 hours.

[0086] The obtained product is a pale yellow powdery solid.

[0087] Comparative Examples 1-5

[0088] Comparative Examples 1-5 are basically the same as Examples 1-5, except that no modified composite material was added in Comparative Examples 1-5.

[0089] Evaluation of oil absorption performance of the product in Example 1

[0090] 1. The oil absorption performance of Examples 1-5 was evaluated, as follows:

[0091] First, the core-shell structure oil absorbent for cementing in this embodiment was ground into a uniform solid powder. The flocculent solid was crushed and dispersed into small pieces. A certain amount of the product was weighed into a filter screen and immersed in white oil at room temperature for 3 min to 24 h to obtain the oil absorption rate curve of the oil absorbent. At the same time, the oil was weighed at certain time points to calculate the oil absorption ratio of the oil absorbent. The oil absorption ratio and time distribution are shown in Table 2 below. The oil absorbent saturated after the experiment was weighed, the residual oil on the surface was filtered off and weighed, and it was quickly put into a centrifuge set to 1000 r / min and centrifuged for 5 min. After taking it out, the weight of the oil absorbent was weighed and the oil retention rate was calculated. The results are shown in Table 3 below.

[0092] Table 2 Oil absorption ratio and time of oil absorbent

[0093]

[0094]

[0095] Table 3 Oil retention rate of oil absorbent

[0096]

[0097] Experiment 1 shows that the oil absorbent reaches oil saturation in about 12 hours, and the oil absorption ratio is between 4 and 9, which can absorb liquid oil in multiples of itself. At the same time, the oil retention rate experiment shows that the oil retention rate is above 70%, and its own oil absorption stability is guaranteed, indicating that the oil absorbent synthesized in the example has good oil absorption performance.

[0098] 2. Oil absorption test of comparative examples and embodiments

[0099] The specific process of this experiment is the same as the experimental process of "evaluating the oil absorption performance of Examples 1 to 5" above. The oil absorption experiment of the products of each comparative example and example was carried out for 8 hours and the experimental results were measured.

[0100] The comparative examples all showed a higher oil absorption rate than the formulations in the examples. The experimental results are shown in Table 4 below.

[0101] Table 4. Oil absorption results of the products from each comparative example and embodiment.

[0102]

[0103] Evaluation of the oil absorption properties of cement stone products from Example 2

[0104] The evaluation of the oil absorption performance of cement stone includes two aspects: (1) directly evaluating the oil absorption capacity of the cement stone by mixing it with oil absorbent; (2) indirectly evaluating the oil absorption capacity of the cement stone by evaluating the strength of the cement stone after the oil absorbent is mixed with the oil slurry and set. The specific experimental contents are as follows:

[0105] 1. Directly evaluate the oil absorption capacity of cement stone mixed with oil absorbent.

[0106] Cement slurry was prepared according to national standard GB / T 10238-2015, with the amount of oil absorbent added being 3% to 7% of the total ash content. During the experiment, the oil absorbent added needed to be soaked in the cement slurry phase in advance to ensure uniform dispersion of the oil absorbent during mixing. The slurry was cured in a 90℃ constant temperature water bath for 72 hours, then removed, dried, weighed, and the original weight was recorded. The cement stone was soaked in white oil, and after 24 hours, the residual oil on the surface was dripped off and weighed. The difference in weight before and after was recorded, and the amount of oil absorbed was calculated. The blank group samples did not contain any oil absorbent, while the other formulas were the same. The specific results are shown in Table 5 below.

[0107] Table 5 Oil Absorption Capacity of Oil Absorbent

[0108]

[0109] 2. Evaluation of the strength of cement paste after setting with oil absorbent in mixed-oil cement slurry.

[0110] Cement slurry was prepared according to the national standard GB / T 10238-2015, with 10% white oil added by volume, along with 1% emulsifier and 5% oil absorbent. As mentioned above, the oil absorbent added during the experiment needed to be soaked in the cement slurry beforehand to ensure uniform dispersion of the oil absorbent during mixing. The slurry was cured in a 90℃ constant temperature water bath for 72 hours, and then placed at room temperature for compressive strength testing. The strength data of cement stone mixed with different oil absorbents and pure mixed oil cement stone (as a blank group) were recorded respectively. The specific experimental results are shown in Table 6 below.

[0111] Table 6

[0112]

[0113]

[0114] In Experiment 2, both the oil absorption evaluation of the cement stone itself and the strength test of the mixed cement stone showed that the performance was far superior to the conventional blank group without oil absorbent, indicating that the oil absorbent product in the example has good oil absorption capacity after being added to the cement stone.

[0115] Experimental Example 3: Elasticity Test of Cement Stone Product

[0116] Cement slurry was prepared according to the national standard GB / T 10238-2015, with an oil absorbent added at 3%–7% of the total cement content. A control group was used, consisting of cement slurry without added oil absorbent. The oil absorbent added during the experiment was pre-soaked in the cement slurry to ensure uniform dispersion during mixing. 1% emulsifier and 5% white oil (by volume of the total cement slurry) were added. The mixture was thoroughly stirred and homogenized for 20 minutes in a 90℃ atmospheric pressure thickener. The cement slurry was then poured into a cylindrical mold with a diameter of 25 mm and a height of 50 mm and cured at 90℃ and 20.7 MPa for 168 hours. The elastic modulus of the cement paste was tested using a triaxial rock mechanics testing device under the following conditions: room temperature, confining pressure of 10 MPa, and loading rate of 2.5 kN / min.

[0117] Table 7 Results of Elastic Modulus of Cement Stone

[0118]

[0119] The experiment in Example 3 shows that the elastic modulus of the blank group was 8.9 GPa, while the elastic modulus of Examples 1 to 5 was below 7 GPa, indicating that the addition of oil absorbent can effectively improve the elasticity of cement.

[0120] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A core-shell structured oil absorbent for cementing under an oil-based drilling fluid, characterized by, The oil absorbent comprises the following components in parts by weight: 20~25 parts of ester monomer, 3~7 parts of modified composite material, 1~5 parts of dispersant, 20~25 parts of pore forming agent, 0.5~0.8 parts of crosslinking agent, 1.3~1.5 parts of initiator and 50~70 parts of water; The ester monomer is selected from any one of the following combinations: lauryl methacrylate and butyl methacrylate at a mass ratio of 10:13, methyl methacrylate and butyl methacrylate at a mass ratio of 5:7, methyl methacrylate, butyl methacrylate and lauryl methacrylate at a mass ratio of 1:1:1, methyl methacrylate, butyl methacrylate and dodecyl methacrylate at a mass ratio of 1:2:2, and lauryl methacrylate and isooctyl methacrylate at a mass ratio of 2:3; The modified composite material is selected from one of hydrophobically modified chitosan or hydrophobically modified cellulose; the hydrophobically modified chitosan and the hydrophobically modified cellulose are obtained by treating chitosan and cellulose with a silane coupling agent, respectively; the hydrophobically modified chitosan and the hydrophobically modified cellulose are obtained by the following method: adding the silane coupling agent and the chitosan or the cellulose at a mass ratio of 1:30 into water, and reacting at 80°C; after the reaction is completed, cooling to room temperature to obtain the hydrophobically modified chitosan or the hydrophobically modified cellulose; The dispersant is selected from hydrophobically modified fumed nano-silica or / and hydrophobically modified nano-calcium carbonate; the hydrophobically modified fumed nano-silica and the hydrophobically modified nano-calcium carbonate are obtained by treating nano-silica and nano-calcium carbonate with a silane coupling agent, respectively.

2. The core-shell structured oil absorbent for cementing under oil-based drilling fluid according to claim 1, characterized by, The hydrophobically modified nano-calcium carbonate is obtained by the following method: adding the silane coupling agent and the nano-calcium carbonate into water, and reacting at 90°C to obtain the hydrophobically modified nano-calcium carbonate; the mass ratio of the nano-calcium carbonate, the silane coupling agent and water is 25:1:

50.

3. The core-shell structured oil-based drilling fluid absorbent for cementing under oil-based drilling fluid conditions according to claim 1, characterized by, The weight fraction of the dispersant should be less than or equal to 0.1 times the weight fraction of water.

4. The core-shell structured oil-based drilling fluid absorbent for cementing under oil-based drilling fluid conditions according to claim 1, characterized by, The pore forming agent is selected from any one or more than two of ethyl acetate, anhydrous ethanol and isobutyl alcohol.

5. The core-shell structured oil-based drilling fluid absorbent for cementing under oil-based drilling fluid conditions according to claim 1, characterized by, The crosslinking agent is selected from divinylbenzene.

6. The core-shell structured oil-based drilling fluid absorbent for cementing under oil-based drilling fluid conditions according to claim 1, characterized by, The initiator is benzoyl peroxide.

7. A process for preparing the core-shell structured oil absorbent for cementing under oil-based drilling fluid conditions according to any one of claims 1 to 6, characterized by, The method comprises the following steps: (1) stirring water, the modified composite material and the dispersant to fully disperse to obtain an inorganic dispersion liquid; mixing the ester monomer, the crosslinking agent, the initiator and the pore forming agent under a magnetic stirrer to obtain an organic mixed liquid; (2) keeping the inorganic dispersion liquid at a constant temperature of 75°C and stirring, while dropping the organic mixed liquid into the inorganic dispersion liquid, and reacting after the dropping is completed; (3) after the reaction is completed, filtering the product, washing, drying to obtain the oil-based drilling fluid condition core cementing use oil absorbent with core-shell structure.

8. The production method according to claim 7, characterized by, In step (1), water and dispersant are dispersed at a rotation speed of 800-1300 r / min for 3-5 h; in step (2), the inorganic dispersion liquid is kept at a constant temperature of 75-85 ℃ and stirred at a rotation speed of 300-500 r / min, and the organic mixed liquid is slowly added to the inorganic dispersion liquid at a rate of 2-5 mL / min, and the reaction is carried out for 2-3 h after the addition is completed.

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