A gas-philic modified proppant for oil and gas well fracturing and preparation method thereof

Abstract

The present invention relates to an aerophilic modified proppant for oil and gas well fracturing, which is prepared by pre-treating a conventional proppant and then modifying it with an aerophilic modifier, a modified catalyst and an organic solvent; the pre-treatment refers to first slightly dissolving the conventional proppant with dilute acid and then depositing and growing active silicate on its surface; the aerophilic modifier has both a hydrophobic group and a hydrophilic group. The beneficial effect achieved by the present invention is that a large amount of aerophilic modifiers with an amphiphilic structure are grafted on the surface of the conventional proppant, so that the tiny bubbles formed by nitrogen in the fracturing fluid can be adsorbed very well, and the suspension and carrying state of the proppant in the low-viscosity slippery water fracturing fluid can be greatly improved by the buoyancy of the bubbles, thereby optimizing the fracturing process parameters.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas mining materials, in particular to an aerophilic modified proppant for oil and gas well fracturing and a preparation method thereof. Background Art

[0002] In the development of unconventional oil and gas resources, volume fracturing is the most important means of reservoir production enhancement and transformation. In order to form a complex fracture network and increase the transformation volume, low-viscosity slickwater fracturing fluid (hereinafter referred to as slickwater) is often used as the main fracturing fluid. Slickwater has low viscosity, weak ability to suspend and carry proppants, fast proppant sedimentation rate, uneven proppant laying during construction (more accumulation near the wellbore area and less accumulation in the far wellbore area), and a high risk of "sand plugging". To solve this problem, on the one hand, the proppant concentration is reduced in the fracturing process parameters, but in order to inject enough proppant to achieve effective support for the fracture, a large amount of fracturing fluid needs to be injected, forming the process characteristics of "ten thousand cubic meters of water, thousands of cubic meters of sand", which not only increases the cost of fracturing but also consumes water resources; on the other hand, the viscosity of the fracturing fluid is increased to improve its ability to suspend and carry proppants, but it also increases the cost of the fracturing fluid and damages the reservoir.

[0003] By reducing the specific gravity of the proppant, its sedimentation rate in the fracturing fluid can be reduced. One method is to use low-density or ultra-low-density materials to prepare the proppant, but its compressive strength is insufficient, and the preparation process is complex and costly. Another method is to modify the proppant, that is, to coat or graft a layer of water-absorbing resin material on its surface. The resin material swells when it encounters water and reduces the specific gravity of the proppant, but the swelling of the resin seriously affects the size of the gaps between the proppant particles, resulting in a significant decrease in the conductivity of the proppant filling layer, affecting the fracturing transformation effect. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide an air-affinity modified proppant for oil and gas well fracturing and a preparation method thereof. The air-affinity modified proppant can very well adsorb tiny bubbles formed by nitrogen in the fracturing fluid (liquid nitrogen is injected during fracturing construction, and the liquid nitrogen vaporizes to form tiny bubbles), and the buoyancy generated by the bubbles is used to improve the suspension and carrying state of the proppant in the low-viscosity slippery water fracturing fluid, thereby optimizing the fracturing process parameters and achieving "liquid control and sand enhancement", and the air-affinity modification has no effect on the mechanical properties of the proppant and the conductivity of the filling layer.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] (First aspect)

[0007] An aerosol-modified proppant for oil and gas well fracturing is prepared by pre-treating a conventional proppant and then modifying it with an aerosol-modifying agent, a modified catalyst and an organic solvent;

[0008] The pretreatment refers to firstly subjecting the conventional proppant to mild dissolution with dilute acid, and then depositing and growing active silicate on its surface;

[0009] The aerophilic modifier is one or more combinations having the following molecular structures:

[0010]

[0011] Wherein, n is an even number greater than or equal to 6;

[0012] m = 5 to 30;

[0013] R is either methyl or ethyl.

[0014] The conventional proppant is natural quartz sand or ceramsite fired from bauxite.

[0015] In this scheme, the aerophilic modifier used contains a siloxane structure, which can react with the active X-OH structure (X is Si or Al) on the surface of the proppant by coupling reaction, so that the aerophilic modifier is grafted on the surface of the proppant, and its fixing effect is much stronger than physical adsorption based on electrostatic attraction, van der Waals force, etc. The molecular structure of the aerophilic modifier in this scheme contains hydrophobic aerophilic perfluoroalkyl chains, hydrophilic polyethoxy chain segments and hydroxyl groups at the same time, and its structure is similar to that of a surfactant. When the aerophilic modified proppant of the present invention is used, the aerophilic modifier grafted on its surface interacts with the microbubbles, that is, the hydrophobic aerophilic perfluoroalkyl chains enter the gas phase in the microbubbles, and the hydrophilic polyethoxy chain segments and hydroxyl groups enter the liquid phase of the microbubbles. This surfactant-like amphiphilic structure can effectively reduce the interfacial tension between the gas and liquid phases, thereby improving the stability of the microbubbles and the adsorption stability of the bubbles on the proppant surface.

[0016] It should be noted that the more active X-OH (X is Si or Al) structures on the proppant surface, the more aerophilic modifiers can be grafted, and the better the aerophilic modification effect. However, the surface of conventional proppants contains very few active X-OH (X is Si or Al) structures, and the number of aerophilic modifiers that can be grafted is very limited, which cannot meet the requirements of adsorbing bubbles and effectively reducing specific gravity. Therefore, in this scheme, some active silica is deposited and grown on the surface of conventional proppants: the active silica is nanoscale, has a large specific surface area, and contains a large number of active Si-OH groups, both of which are conducive to the modification reaction - that is, more aerophilic modifiers can be grafted.

[0017] Specifically, conventional proppants can be slightly eroded during the dilute acid treatment process, exposing more active atoms or groups such as O, Si, Al, OH, etc. on their surface, namely active sites; then these active atoms or groups are used as base points to deposit and grow active silicate in real time. The protruding active silicate deposits formed on the active sites have a large specific surface area and a large number of active Si-OH, which are conducive to grafting more aerophilic modifiers; and because the active silicate shares active atoms or groups with the proppant surface, the bonding strength between the active silicate and the proppant can be greatly enhanced, so compared with general physical coating, its bonding effect is more obvious.

[0018] The principle of preparing modified proppants, in simple terms, is to first slightly dissolve the conventional proppants with dilute acid to expose the active sites; then deposit active silicic acid, which has a large surface area and a large number of active Si-OH structures, on the active sites; then use an amphiphilic air-philic modifier to undergo a coupling reaction with the Si-OH structure on the active silicic acid, thereby grafting the modifier onto the proppant surface to form a modified proppant.

[0019] Furthermore, the present invention uses an organic acid as a catalyst, such as formic acid, acetic acid or a mixture thereof. The organic acid can promote the decomposition reaction of the siloxane structure in the aerophilic modifier, accelerate the coupling reaction, and improve the conversion rate of the aerophilic modifier.

[0020] Furthermore, the organic solvent is dimethyl sulfoxide, dimethylformamide or a mixture thereof.

[0021] (Second aspect)

[0022] A method for preparing an aerosol-modified proppant for oil and gas well fracturing comprises the following preparation steps:

[0023] S1, proppant pretreatment;

[0024] After washing the conventional proppant, stir it in the mixed dilute acid solution for 20 to 40 minutes, and then filter it dry;

[0025] Then, the pickled proppant is mixed with a sodium metasilicate aqueous solution, and diluted hydrochloric acid is added in batches to maintain an appropriate pH value to allow active silicate to precipitate and grow, and then washed with clean water for multiple times, dried at 70°C to 80°C, and set aside for use;

[0026] S2, dissolving the aerophilic modifier and the modified catalyst in an organic solvent to prepare a modifier solution;

[0027] S3, spraying the modifier solution onto the pretreated proppant, and then heating and baking for 20 minutes to 30 minutes; and then cooling naturally to obtain a finished modified proppant.

[0028] Furthermore, in the mixed dilute acid, there are hydrofluoric acid with a concentration of 1% to 3% and hydrochloric acid with a concentration of 2% to 4%; when the mixed dilute acid is mixed with the proppant, the volume ratio of the two is (2 to 3):1.

[0029] Furthermore, the aqueous concentration of sodium metasilicate is 5% to 8%; the volume ratio of sodium metasilicate solution to proppant is 2:1; the concentration of dilute hydrochloric acid is 4% to 6%; and the pH value is 2 to 5.

[0030] Furthermore, in the modifier solution, the mass ratio of aerophilic modifier: organic solvent: modified catalyst is (20-40): (60-80): (1-3).

[0031] Furthermore, in the spraying step, when the modifier solution is sprayed onto the pretreated conventional proppant, the mass ratio of the pretreated conventional proppant to the modifier solution is 1000:(3-8).

[0032] Furthermore, in the baking step, high temperature baking is adopted, for example, the baking temperature is 100° C. to 150° C. High temperature baking can accelerate the coupling reaction, help shorten the reaction time, and improve the continuous production efficiency.

[0033] The present invention has the following advantages:

[0034] (1) The aerophilic modified proppant provided by the present invention reduces its own specific gravity by adsorbing bubbles, thereby improving its suspension and carrying state in the low-viscosity fracturing fluid, and the aerophilic modification has no effect on the mechanical properties of the proppant and the conductivity of the filling layer;

[0035] (2) By pretreating the conventional proppant with a dilute acid for mild dissolution and activation and then depositing active silicate, the surface of the proppant can be enriched with active sites that can be used for aerophilic modification, so that more aerophilic modifiers can be grafted and the modification effect can be improved.

[0036] (3) The present invention simultaneously introduces hydrophobic and air-philic perfluoroalkyl chains, hydrophilic polyethoxy chain segments and hydroxyl groups into the molecular structure of the modifier. This surfactant-like amphiphilic structure can effectively reduce the interfacial tension between the gas and liquid phases, thereby improving the stability of microbubbles and the adsorption stability of bubbles on the proppant surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The figure is a comparison of the 10-min sedimentation state of the proppant of Examples 1 to 2 of the present invention and the unmodified proppant under the simulated microbubble conditions (a, b, c, d from left to right are Example 1, unmodified ceramsite, Example 2, and unmodified quartz sand, respectively);

[0038] Figure 2The 10-minute sedimentation state of Comparative Examples 1 and 2 under simulated microbubble conditions (the left picture is Comparative Example 1, and the right picture is Comparative Example 2);

[0039] Figure 3 The 10-min sedimentation state of Comparative Examples 3 to 4 under simulated microbubble conditions (the left picture is Comparative Example 3, and the right picture is Comparative Example 4);

[0040] Figure 4 The flow conductivity of Examples 1 to 2 of the present invention and the unmodified proppant is compared under different closure pressures. DETAILED DESCRIPTION

[0041] The present invention is further described below in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited to the following description.

[0042] The present invention discloses a method for preparing an aerophilic modified proppant for oil and gas well fracturing, and the preparation steps are as follows:

[0043] S1, proppant pretreatment;

[0044] After washing the conventional proppant, stir it in a mixed dilute acid solution for 20 to 40 minutes, and then filter it dry; wherein the volume ratio of the mixed dilute acid to the proppant is (2 to 3):1; the mixed dilute acid contains hydrofluoric acid with a concentration of 1% to 3% and hydrochloric acid with a concentration of 2% to 4%;

[0045] The pickled proppant is then mixed with a 5% to 8% sodium metasilicate aqueous solution in a volume ratio of 1:2, and a 4% to 6% dilute hydrochloric acid is added in batches to maintain a pH value of 2 to 5 to deposit and grow active silicate, and then washed with clean water for multiple times, dried at 70°C to 80°C, and set aside;

[0046] S2, dissolving the aerophilic modifier and the modified catalyst in an organic solvent to prepare a modifier solution; in the modifier solution, the mass ratio of the aerophilic modifier: the organic solvent: the modified catalyst is (20-40): (60-80): (1-3);

[0047] S3. Spray the modifier solution onto the conventional proppant, and then heat and bake it for 20min to 30min at a temperature of 100°C to 150°C; then cool it naturally to obtain a finished modified proppant; wherein, during spraying, the mass ratio of conventional proppant to modifier solution is 1000:(3 to 8).

[0048] In the specific implementation process, the corresponding parameters can be selected according to the needs, for example: in S1, the stirring time between the support particles and the mixed dilute acid solution is 5 minutes, and the volume ratio of the mixed dilute acid to the support agent is 2:1; in the mixed dilute acid, there are 3% hydrofluoric acid and 2% hydrochloric acid; in S2, in the modifier solution, the mass ratio of the aerophilic modifier: the organic solvent: the modified catalyst is 20:60:1; in S3, the heating and baking is 20 minutes, the baking temperature is 100°C, and the support particles: the modifier solution is 1000:3 by mass ratio during spraying;

[0049] Or for example: in S1, the stirring time between the support particles and the mixed dilute acid solution is 20 minutes, and the volume ratio of the mixed dilute acid to the support agent is 3:1; in the mixed dilute acid, there are 1% hydrofluoric acid and 4% hydrochloric acid; in S2, in the modifier solution, the mass ratio of the aerophilic modifier: the organic solvent: the modified catalyst is 40:80:3; in S3, the heating and baking is 30 minutes, the baking temperature is 150°C, and the support particles: the modifier solution is 1000:8 by mass ratio during spraying;

[0050] Or for example: in S1, the stirring time between the support particles and the mixed dilute acid solution is 20 minutes, and the volume ratio of the mixed dilute acid to the support agent is 2:1; in the mixed dilute acid, there are 2% hydrofluoric acid and 3% hydrochloric acid; in S2, in the modifier solution, the mass ratio of the aerophilic modifier: the organic solvent: the modified catalyst is 30:70:2; in S3, the heating and baking is 25 minutes, the baking temperature is 125°C, and the support particles: the modifier solution is 1000:5 by mass ratio during spraying.

[0051] The present invention also discloses an aerophilic modified proppant for oil and gas well fracturing, which is prepared by pre-treating a conventional proppant and then modifying it with an aerophilic modifier, a modified catalyst and an organic solvent;

[0052] The aerophilic modifier is one or more combinations having the following molecular structures:

[0053]

[0054] Wherein, n is an even number greater than or equal to 6; m=5 to 30; and R is either a methyl group or an ethyl group.

[0055] In this embodiment, the conventional proppant is natural quartz sand or ceramsite fired from bauxite.

[0056] In this embodiment, the modified catalyst used is an organic acid, such as formic acid, acetic acid or a mixture thereof.

[0057] In this embodiment, the organic solvent used is dimethyl sulfoxide, dimethylformamide or a mixture thereof.

[0058] The specific components and preparation steps are implemented as follows:

[0059] (Example 1) An aerophilic modified ceramsite proppant, prepared as follows:

[0060] S1, 40 / 70 ceramsite proppant (apparent density 3.18g / cm 3 , volume density 1.70g / cm 3 ) and stirred in a mixed dilute acid solution for 30 min, and then filtered; wherein the mixed dilute acid contains 2% hydrofluoric acid and 3% hydrochloric acid, and the volume ratio of the mixed dilute acid to the proppant is 2.5:1;

[0061] Then, the acid-washed ceramsite proppant is mixed with an 8% sodium metasilicate aqueous solution, and 5% dilute hydrochloric acid is added in batches to maintain pH=3, and active silicate is deposited and grown, and then washed with clean water for multiple times, dried at 70°C to 80°C, and set aside;

[0062] S2, the aerophilic modifier, the organic solvent dimethyl sulfoxide and the modified catalyst acetic acid are mixed uniformly in a mass ratio of 30:70:2 to prepare a modifier solution, wherein the structure of the aerophilic modifier is as follows:

[0063]

[0064] S3, spraying the modifier solution onto the proppant at a mass ratio of 1000:8 between the proppant and the modifier solution, and then heating and baking at 120° C. for 30 min, and cooling naturally to obtain a modified 40 / 70 ceramsite proppant;

[0065] (Example 2) An aerophilic modified quartz sand proppant, prepared as follows:

[0066] S1, 40 / 70 quartz sand proppant (apparent density 2.65g / cm 3 , volume density 1.51g / cm 3 ) and stirred in a mixed dilute acid solution for 30 min, and then filtered; wherein the mixed dilute acid contains 3% hydrofluoric acid and 2% hydrochloric acid, and the volume ratio of the mixed dilute acid to the proppant is 2.5:1;

[0067] Then, the acid-washed quartz sand proppant is mixed with a 5% sodium metasilicate aqueous solution, and 5% dilute hydrochloric acid is added in batches to maintain pH=3, and active silicate deposition growth is performed, and then it is washed with clean water for multiple times, dried at 70°C to 80°C, and set aside;

[0068] S2, the aerophilic modifier, the organic solvent dimethyl sulfoxide and the modified catalyst acetic acid are mixed uniformly in a mass ratio of 30:70:2 to prepare a modifier solution, wherein the structure of the aerophilic modifier is as follows:

[0069]

[0070] S3. Spray the modifier solution onto the proppant at a mass ratio of 1000:5 between the proppant and the modifier solution, and then heat and bake at 120° C. for 30 minutes and cool naturally to obtain a modified 40 / 70 quartz sand proppant.

[0071] (Comparative Example 1) An aerophilic modified ceramsite proppant, prepared as follows:

[0072] S1, 40 / 70 ceramsite proppant (apparent density 3.18g / cm 3 , volume density 1.70g / cm 3 ) Wash, dry at 70℃~80℃ and set aside;

[0073] S2, the aerophilic modifier, the organic solvent dimethyl sulfoxide and the modified catalyst acetic acid are mixed uniformly in a mass ratio of 30:70:2 to prepare a modifier solution, wherein the structure of the aerophilic modifier is as follows:

[0074]

[0075] S3, spraying the modifier solution onto the proppant at a mass ratio of 1000:8 between the proppant and the modifier solution, and then heating and baking at 120° C. for 30 min, and cooling naturally to obtain a modified 40 / 70 ceramsite proppant;

[0076] (Comparative Example 2) An aerophilic modified quartz sand proppant, prepared as follows:

[0077] S1. Wash 40 / 70 quartz sand proppant (apparent density 2.65 g / cm3, bulk density 1.51 g / cm3), dry at 70°C to 80°C, and set aside;

[0078] S2, the aerophilic modifier, the organic solvent dimethyl sulfoxide and the modified catalyst acetic acid are mixed uniformly in a mass ratio of 30:70:2 to prepare a modifier solution, wherein the structure of the aerophilic modifier is as follows:

[0079]

[0080] S3. Spray the modifier solution onto the proppant at a mass ratio of 1000:5 between the proppant and the modifier solution, and then heat and bake at 120° C. for 30 minutes and cool naturally to obtain a modified 40 / 70 quartz sand proppant.

[0081] (Comparative Example 3) An aerophilic modified ceramsite proppant, prepared as follows:

[0082] S1, 40 / 70 ceramsite proppant (apparent density 3.18g / cm 3 , volume density 1.70g / cm 3 ) and stirred in a mixed dilute acid solution for 30 min, and then filtered; wherein the mixed dilute acid contains 2% hydrofluoric acid and 3% hydrochloric acid, and the volume ratio of the mixed dilute acid to the proppant is 2.5:1;

[0083] Then, the acid-washed ceramsite proppant is mixed with an 8% sodium metasilicate aqueous solution, and 5% dilute hydrochloric acid is added in batches to maintain pH=3, and active silicate is deposited and grown, and then washed with clean water for multiple times, dried at 70°C to 80°C, and set aside;

[0084] S2, the aerophilic modifier, the organic solvent dimethyl sulfoxide and the modified catalyst acetic acid are mixed uniformly in a mass ratio of 30:70:2 to prepare a modifier solution, wherein the structure of the aerophilic modifier is as follows:

[0085]

[0086] S3, spraying the modifier solution onto the proppant at a mass ratio of 1000:8 between the proppant and the modifier solution, and then heating and baking at 120° C. for 30 min, and cooling naturally to obtain a modified 40 / 70 ceramsite proppant;

[0087] (Comparative Example 4) An aerophilic modified quartz sand proppant, prepared as follows:

[0088] S1, 40 / 70 quartz sand proppant (apparent density 2.65g / cm 3 , volume density 1.51g / cm 3 ) and stirred in a mixed dilute acid solution for 30 min, and then filtered; wherein the mixed dilute acid contains 3% hydrofluoric acid and 2% hydrochloric acid, and the volume ratio of the mixed dilute acid to the proppant is 2.5:1;

[0089] Then, the acid-washed quartz sand proppant is mixed with a 5% sodium metasilicate aqueous solution, and 5% dilute hydrochloric acid is added in batches to maintain pH=3, and active silicate deposition growth is performed, and then it is washed with clean water for multiple times, dried at 70°C to 80°C, and set aside;

[0090] S2, the aerophilic modifier, the organic solvent dimethyl sulfoxide and the modified catalyst acetic acid are mixed uniformly in a mass ratio of 30:70:2 to prepare a modifier solution, wherein the structure of the aerophilic modifier is as follows:

[0091]

[0092] S3. Spray the modifier solution onto the proppant at a mass ratio of 1000:5 between the proppant and the modifier solution, and then heat and bake at 120° C. for 30 minutes and cool naturally to obtain a modified 40 / 70 quartz sand proppant.

[0093] (Experimental Example 1)

[0094] Using Examples 1-2 and unmodified proppants, the first performance test was performed:

[0095] In order to verify that the air-affinity modified proppant of the present invention can absorb bubbles to reduce its own specific gravity and improve its suspension and carrying state in low-viscosity fracturing fluid, a proppant sedimentation experiment (proppant concentration 300kg / m 3 ), 10min static sedimentation results are shown in the attached Figure 1 Before the sedimentation experiment, a high-speed agitator is used to stir the slick water and the aerophilic modified proppant at 5500 r / min for 90 s. High-speed stirring will generate a large number of bubbles, which can simulate the microbubbles generated by the liquid nitrogen injected during fracturing construction.

[0096] from Figure 1 It can be seen that after 10 minutes of static sedimentation, most of Example 1 and Example 2 are suspended in the low-viscosity slippery water, with only a small amount of sedimentation. The proppant is relatively fluffy due to the adsorption of bubbles; the two unmodified proppant samples have completely settled, and are relatively densely stacked due to the inability to adsorb bubbles. The above results show that the air-affinity modification in the present invention can enable the proppant to have the ability to adsorb bubbles, thereby improving its suspension and carrying state in the low-viscosity fracturing fluid.

[0097] (Experimental Example 2)

[0098] Using Comparative Examples 1-2, the second performance test was performed:

[0099] In order to verify the effect of proppant pretreatment on the subsequent modification effect in the present invention, a proppant sedimentation experiment (proppant concentration 200kg / m 3 ), 10min static sedimentation results are shown in the attached Figure 2 Similarly, before the sedimentation experiment, a high-speed stirrer is used to stir the slick water and the aerophilic modified proppant at 5500 r / min for 90 s.

[0100] from Figure 2It can be seen that after standing and settling for 10 minutes, both Comparative Examples 1 and 2 are almost completely settled, with only a small amount of suspension, and the settled part is relatively densely stacked. The suspension effect of Comparative Examples 1-2 is much worse than that of Examples 1-2, indicating that the amount of aerophilic modifiers that can be grafted on the surface of the proppant that has not been pretreated cannot meet the requirement of self-suspension after gas adsorption. This is mainly because the amount of active X-OH (X is Si or Al) that can be used to react with the aerophilic modifier on the surface of the proppant that has not been pretreated is very small, and the amount of aerophilic modifier that can be grafted is insufficient; after pretreatment, the active silicate deposited and grown on the proppant surface contains a large amount of Si-OH, which can be grafted with a large amount of aerophilic modifiers, and the modification effect is good, thereby achieving the effect of self-suspension after gas adsorption.

[0101] (Experimental Example 3)

[0102] Using Comparative Examples 3 to 4, the third performance test was performed:

[0103] In order to verify the effect of the surfactant-like structure of the air-philic modifier on the modification effect, a proppant sedimentation experiment (proppant concentration 200 kg / m 3 ), 10min static sedimentation results are shown in the attached Figure 3 Similarly, before the sedimentation experiment, the slick water fracturing fluid and the gas-affinity modified proppant need to be stirred at 5500 r / min for 90 s using a high-speed stirrer.

[0104] from Figure 3 It can be seen that most of the comparative example 3 (ceramsite) with high apparent density has settled, while the comparative example 4 (quartz sand) with relatively low apparent density can achieve partial suspension, and the settled parts of both are fluffy and piled up, indicating that both have a certain adsorption effect on bubbles, but the number of adsorbed bubbles is not enough to suspend them in the liquid, and the modification effect is worse than that of Examples 1 to 2. Comparing the molecular structures of the modifiers used in Examples 1 to 2 and Comparative Examples 3 to 4, the difference is that hydrophilic polyethoxy segments and hydroxyl groups are introduced into the modifier molecules of Examples 1 to 2, indicating that the introduction of hydrophilic polyethoxy segments and hydroxyl groups into the molecular structure of the modifier helps to improve the stability of microbubbles and the adsorption stability of bubbles on the proppant surface, and further improves the suspension and carrying performance of the proppant.

[0105] (Experimental Example 4)

[0106] Using Examples 1-2 and unmodified proppants, the crushing rate and conductivity tests were performed:

[0107] According to the petroleum and natural gas industry standard SY / T 5108-2014 "Proppant Performance Test Method for Hydraulic Fracturing and Gravel Packing Operations", the breakage rate of the proppant before and after modification was tested, and the results are shown in Table 1.

[0108] Table 1 Comparison of the crushing rates of Examples 1 to 2 and unmodified proppants

[0109]

[0110] From the experimental results, the breakage rate of the proppant before and after the air-affinity modification is basically the same, indicating that the air-affinity modification has no effect on the mechanical strength of the proppant.

[0111] The API standard flow chamber was used to examine the change in the flow conductivity of the proppant before and after modification. In this experiment, the proppant laying concentration was set at 5 kg / m 2 The results are attached. Figure 4 .

[0112] from Figure 4 It can be seen that the API conductivity of the aerophilic modified proppant of the present invention is slightly higher than that of the unmodified conventional proppant. This is because after the proppant surface is hydrophobic and aerophilic, the contact angle with water increases, which reduces the capillary resistance and thus improves the conductivity, indicating that the aerophilic modification has no negative impact on the conductivity of the proppant.

[0113] In summary, the air-affinity modified proppant of the present invention can reduce its own specific gravity by adsorbing bubbles, thereby improving its suspension and carrying state in low-viscosity slippery water fracturing fluid, and the air-affinity modification has no effect on the mechanical properties of the proppant and the conductivity of the filling layer. Therefore, the air-affinity modified proppant has good prospects in improving the laying profile of the proppant in the fracture, optimizing the fracturing process parameters, achieving "liquid control and sand enhancement", reducing costs and increasing efficiency, etc.

[0114] The above embodiments only express preferred implementation modes, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention.

Claims

1. A gas-philic modified proppant for oil and gas well fracturing, characterized in that: The proppant is pretreated and then modified with an aerophilic modifier, a modified catalyst and an organic solvent to obtain the product; The specific preparation method of the air-affinity modified proppant is as follows: S1, pretreatment of the proppant; after washing the proppant, stir it in a mixed dilute acid solution for 20min to 40min, and then filter it dry; then mix the acid-washed proppant with a sodium metasilicate aqueous solution, add dilute hydrochloric acid in batches, maintain an appropriate pH value, and carry out active silicate deposition and growth, and then wash it with clean water for multiple times, dry it at 70°C to 80°C, and set it aside; wherein the mixed dilute acid has a concentration of 1% to 3% of hydrofluoric acid and a concentration of 2% to 4% of hydrochloric acid; when the mixed dilute acid is mixed with the proppant, the volume ratio of the two is (2 to 3): 1; wherein, The aqueous concentration of sodium metasilicate is 5%-8%; the volume ratio of sodium metasilicate solution to proppant is 2:1; the concentration of dilute hydrochloric acid is 4%-6%; the pH value is 2-5; S2, dissolving an aerophilic modifier and a modified catalyst in an organic solvent to prepare a modifier solution; in the modifier solution, the mass ratio of the aerophilic modifier: organic solvent: modified catalyst is (20-40): (60-80): (1-3); S3, spraying the modifier solution onto the pretreated proppant, and then heating and baking for 20min-30min; and then cooling naturally to obtain a modified proppant finished product The aerophilic modifier has one or more combinations of the following molecular structures: Wherein, n is an even number greater than or equal to 6; m＝5～30； R is either methyl or ethyl; The modified catalyst is one of formic acid and acetic acid or a mixture thereof; The proppant is natural quartz sand or ceramsite fired from bauxite.

2. The aerophilic modified proppant for oil and gas well fracturing according to claim 1, characterized in that: The organic solvent is dimethyl sulfoxide, dimethylformamide or a mixture thereof.

3. A method for preparing an aerophilic modified proppant for oil and gas well fracturing as claimed in claim 1, characterized in that: The method comprises the following preparation steps: S1, proppant pretreatment; After the proppant is washed, stir it in the mixed dilute acid solution for 20 to 40 minutes, and then filter it dry; The pickled proppant is then mixed with a sodium metasilicate aqueous solution, diluted hydrochloric acid is added in batches, an appropriate pH value is maintained, active silicate deposition and growth is performed, and then the mixture is washed with clean water for multiple times, dried at 70°C to 80°C, and set aside for use; wherein the mixed diluted acid contains hydrofluoric acid with a concentration of 1% to 3% and hydrochloric acid with a concentration of 2% to 4%; when the mixed diluted acid is mixed with the proppant, the volume ratio of the two is (2 to 3):1; wherein the aqueous concentration of sodium metasilicate is 5% to 8%; the volume ratio of the sodium metasilicate solution to the proppant is 2:1; the concentration of the diluted hydrochloric acid is 4% to 6%; and the pH value is 2 to 5; S2, dissolving the aerophilic modifier and the modified catalyst in an organic solvent to prepare a modifier solution; in the modifier solution, the mass ratio of the aerophilic modifier: the organic solvent: the modified catalyst is (20-40): (60-80): (1-3); S3, spraying the modifier solution onto the pretreated proppant, and then heating and baking for 20 minutes to 30 minutes; and then cooling naturally to obtain a finished modified proppant.

4. The method for preparing an aerophilic modified proppant for oil and gas well fracturing according to claim 3, characterized in that: In the spraying step of step S3, when the modifier solution is sprayed onto the pretreated proppant, the mass ratio of the pretreated proppant to the modifier solution is 1000:(3-8).

5. The method for preparing an aerophilic modified proppant for oil and gas well fracturing according to claim 3, characterized in that: In the baking step of step S3, the baking temperature is 100°C to 150°C.

Images