Super-hydrophobic modifier based on carbonate rock core, modification method and application

Abstract

The invention relates to the technical field of oil and gas field development, and provides a super-hydrophobic modifier based on a carbonate rock core, a modification method and application, the modifier is composed of a polysiloxane solution, stearic acid and super-hydrophobic nano-silica; the super-hydrophobic nano silicon dioxide is obtained by modifying nano silicon dioxide in a solvent by using an alkylsilane series modifier with the concentration of 0.5-5wt%; the solvent is composed of N, N-dimethylformamide, tetrahydrofuran and carbon tetrachloride according to the mass ratio of (5-6): 2: (1-2), the concentration of polysiloxane is 1.5-2.5 mg / L, and the concentration of stearic acid is 0.1-1 mg / L. According to the invention, rough super-hydrophobic particles are grafted on the surface of the smooth carbonate rock, so that a hydrophobic barrier is formed on the surface of the rock core, and water drops rapidly roll on the surface of the rock core. After the surface of the carbonate rock is subjected to super-hydrophobic modification, the seepage resistance of water is reduced, so that the capacity of water adsorbed on the surface of a rock core is greatly weakened, and stable output of gas in an actual carbonate rock gas reservoir is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field development technology, and more specifically, to a superhydrophobic modifier based on carbonate rock cores, a modification method, and its application. Background Technology

[0002] In carbonate gas reservoirs, both microfractures and large fractures significantly impact fluid flow. Microfractures are widely distributed throughout the formation, closely connected to pores, forming seepage channels and promoting fluid exchange between pores. Large fractures, on the other hand, are sparse and unevenly distributed, extending from meters to kilometers. Fluid flow in these large fractures exceeds the conventional Darcy flow range, exhibiting characteristics of high-speed non-Darcy flow. After a gas well in a water-gas reservoir is put into production, the pressure drop caused by production activities rapidly propagates along the large fractures connected to edge and bottom water. This rapid propagation mechanism causes formation water to rush into the well bottom along the large fractures, forming the so-called "fracture water channeling" phenomenon. This phenomenon not only accelerates formation water intrusion but can also significantly impact the stable production of gas wells and the overall development strategy of the gas reservoir.

[0003] Water control technology in gas reservoirs is a crucial aspect of oil and gas field development, playing a vital role in improving reservoir recovery and extending well lifespan. Existing water control technologies primarily focus on physical plugging or chemical displacement, but these methods suffer from drawbacks such as "blocking both water and gas," "poor temperature and salinity resistance," and "short-lasting modification effects." Physical plugging can easily lead to irreversible damage to reservoir permeability, while chemical displacement agents are prone to decomposition and failure in high-temperature, high-salinity environments, making it difficult to meet the long-term development needs of carbonate gas reservoirs.

[0004] Therefore, developing a superhydrophobic modification technology for carbonate rocks that is simple to implement, has strong environmental stability, and can achieve "water blocking without gas blocking" is of great practical significance for solving the water-locking problem in gas reservoirs and improving recovery rates. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a superhydrophobic modifier based on carbonate rock cores, a modification method, and its application. This invention grafts rough superhydrophobic particles onto the surface of carbonate rocks, thereby forming a hydrophobic barrier on the core surface, reducing water seepage resistance, and thus significantly weakening the ability of water to adsorb onto the core surface, ensuring stable gas production in actual carbonate gas reservoirs.

[0006] The technical solution of this invention is as follows:

[0007] In a first aspect, the present invention provides a superhydrophobic modifier based on carbonate rock core, wherein the superhydrophobic modifier is composed of polysiloxane solution, stearic acid and superhydrophobic nano silica.

[0008] The superhydrophobic nano-silica is obtained by modifying nano-silica in a solvent with a modifier at a concentration of 0.5~5wt%;

[0009] The solvent is composed of N,N-dimethylformamide, tetrahydrofuran and carbon tetrachloride in a mass ratio of (5~6):2:(1~2);

[0010] The concentration of the polysiloxane is 1.5~2.5 mg / L, and the concentration of the stearic acid is 0.1~1 mg / L;

[0011] The modifier includes at least one of alkylsilane coupling agents and aluminate coupling agents.

[0012] Furthermore, the superhydrophobic nano-silica in the superhydrophobic modifier has a mass percentage of 10-30%.

[0013] Furthermore, the alkylsilane coupling agent includes at least one of isooctyltriethoxysilane, dodecyltriethoxysilane, and n-octyltrimethoxysilane.

[0014] Furthermore, the preparation method of the alkylsilane coupling agent is as follows:

[0015] The alkylsilane is catalytically hydrolyzed in the solvent, and 0.1-0.5% hydrochloric acid or sulfuric acid is added to accelerate the catalytic hydrolysis to obtain the alkylsilane coupling agent.

[0016] Furthermore, the preparation method of the superhydrophobic nano-silica is as follows:

[0017] The nano-silica was dispersed in the solvent, the modifier was added, and the mixture was ultrasonically dispersed for 20 min, stirred at 3000 r / min for 20 min, and modified at 75°C for 10-12 h. After washing, centrifugation, drying and grinding, the superhydrophobic nano-silica was obtained.

[0018] Furthermore, the preparation method of the superhydrophobic modifier is as follows:

[0019] The polysiloxane and stearic acid are dissolved in the solvent, and the superhydrophobic nano silica is added and dispersed evenly to obtain the superhydrophobic modifier.

[0020] Secondly, based on the same inventive concept, this invention provides a method for superhydrophobic modification of carbonate rock cores using the superhydrophobic modifier described in any one of the first aspects, comprising the following steps:

[0021] The carbonate rock core slices were placed in the superhydrophobic modifier and modified at 120°C for 6 hours to obtain carbonate rock cores with preliminary surface modification.

[0022] The surface-modified carbonate rock core was dried at 60°C for 6-10 hours to obtain superhydrophobic carbonate rock.

[0023] Furthermore, the modified superhydrophobic carbonate rock has a contact angle ≥135° and a roll-off angle ≤9°.

[0024] Furthermore, the carbonate rock core includes one or more of calcite, dolomite, and a mixture of real carbonate rock cores.

[0025] Thirdly, based on the same inventive concept, this invention provides an application of the superhydrophobic modification method described in any of the second aspects in water control and production enhancement of carbonate gas reservoirs.

[0026] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects:

[0027] 1. After modification, the contact angle of the core is ≥135°, with an optimal value of 151.58°, and the roll-off angle is ≤9°, allowing the droplet to roll rapidly on the surface; at 120℃ and 3×10 5 It retains its superhydrophobicity even after being immersed in a high-salt environment of mg / L for 50 days, exhibiting outstanding temperature and salt resistance, and excellent and stable hydrophobic properties.

[0028] 2. Achieve precise control of water blocking without gas blocking. Under a displacement pressure difference of 0.5~4.0MPa, the gas phase seepage velocity is increased by more than 50% compared with the unmodified core, while the water phase seepage velocity is significantly reduced, effectively solving the problem of reduced production caused by water intrusion, and the selective hydrophobic effect is significant. Attached Figure Description

[0029] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a hydrophilicity curve for Test Example 1 of the present invention;

[0032] Figure 2 This is a graph showing the oil absorption rate of Test Example 2 of the present invention;

[0033] Figure 3 This is a schematic diagram of the wetting contact angles before and after modification for test examples 3 OL-1~OL-4 of the present invention;

[0034] Figure 4This is a schematic diagram of the wetting contact angles after the combined modification of OL-1 to OL-4 in Test Example 3 of the present invention;

[0035] Figure 5 This is a graph showing the contact angle and roll-off angle curves of the modified carbonate rock surface in Example 1 of Test Example 4 of the present invention.

[0036] Figure 6 This is a graph showing the contact angle and roll-off angle of the modified carbonate rock surface in Example 2 of Test Example 4 of the present invention.

[0037] Figure 7 This is a graph showing the contact angle and roll-off angle curves of the modified carbonate rock surface in Example 3 of Test Example 4 of the present invention.

[0038] Figure 8 This is a transient image of droplet rolling on the surface of a superhydrophobic carbonate rock core in Test Example 5 of this invention;

[0039] Figure 9 In Test Example 6 of this invention, 3×10 at 120℃ 5 Core contact angle and roll angle after soaking in mg / L for 10 days;

[0040] Figure 10 In Test Example 6 of this invention, 3×10 at 120℃ 5 Droplet morphology characteristics of core samples after soaking in mg / L for 10 days;

[0041] Figure 11 This is a graph showing the pressure curves at the injection port of the aqueous phase at different seepage velocities in Test Example 7 of the present invention.

[0042] Figure 12 This is a graph showing the change in the flow velocity of the aqueous phase before and after modification under different injection pressure differentials in Test Example 7 of the present invention.

[0043] Figure 13 This is a graph showing the change in aqueous phase flow rate before and after modification under different gas phase injection pressure differentials in Test Example 7 of this invention.

[0044] Figure 14 This is a graph showing the change in relative seepage velocity of the water phase during gas / water two-phase displacement before and after modification under different injection pressure differences in test example 7 of this invention.

[0045] Figure 15 This is a schematic diagram of droplet rolling in Comparative Example 3 of Test Example 8 of the present invention;

[0046] Figure 16 This is a schematic diagram of the hydrophobic effect of Comparative Example 3 in Test Example 8 of the present invention;

[0047] Figure 17 This is a schematic diagram of droplet rolling in Example 3 of Test Example 8 of the present invention. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0049] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0050] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed according to national standards. If no corresponding national standard exists, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0051] Example 1

[0052] This embodiment 1 provides a superhydrophobic modification method based on carbonate rock cores, including the following steps:

[0053] S1. Solvent preparation: Mix dimethylformamide (DMF), tetrahydrofuran (THF) and carbon tetrachloride in a mass ratio of 6:2:1, and stir until homogeneous for later use;

[0054] S2. Catalytically hydrolyze the aluminate coupling agent (molecular formula (C3H7O)x·Al(OCOR1)m·(OCOR2)n) in a solvent, and add 0.1% hydrochloric acid to accelerate the catalytic hydrolysis to obtain a modifier OL-1 with a concentration of 0.5wt%.

[0055] S3. Dissolve OL-1 in anhydrous ethanol, place it in a 50 mL beaker, and sonicate it at room temperature for 30 min to mix evenly. Place 10 nm nano-silica particles in 10 mL of OL-1 and sonicate them for 20 min. Stir at 3000 r / min in a high-speed stirrer for 20 min, and place them in a 75 °C electric heating drying oven for 12 h for modification. After the reaction, remove the supernatant, wash the nano-silica several times with deionized water and anhydrous ethanol, centrifuge, dry at 60 °C, and grind to obtain superhydrophobic nano-silica.

[0056] S3. Add polysiloxane (PD) to a solvent to prepare a concentration of 1.5 mg / L, stir at 75°C for 6 hours to fully dissolve, add 0.5 mg / L stearic acid and 10% superhydrophobic nano silica, and stir at high speed to disperse evenly to obtain a superhydrophobic modifier.

[0057] S4. Calcite and dolomite powders were mixed and pressed into core sheets, which were then soaked in a superhydrophobic modifier, kept at 120°C for 6 hours, washed with anhydrous ethanol, and dried at 60°C for 12 hours to obtain superhydrophobic modified carbonate rock.

[0058] Example 2

[0059] Example 2 provides a superhydrophobic modification method based on carbonate rock cores. The only difference from Example 1 is that the modifier is dodecyltriethoxysilane with a concentration of 1 wt%, named OL-2, the nano silica particle size is 50 nm, the polysiloxane concentration is 2.0 mg / L, the stearic acid concentration is 0.1 mg / L, and the superhydrophobic nano silica is 20%.

[0060] Example 3

[0061] This embodiment 3 provides a superhydrophobic modification method based on carbonate rock cores. The only difference from embodiment 1 is that the modifier is isooctyltriethoxysilane with a concentration of 3wt%, named OL-3, the nano silica particle size is 100nm, the polysiloxane concentration is 2.5mg / L, the stearic acid concentration is 1mg / L, and the superhydrophobic nano silica is 30%.

[0062] Example 4

[0063] Example 4 provides a superhydrophobic modification method based on carbonate rock cores. The only difference from Example 1 is that the modifier is n-octyltrimethoxysilane with a concentration of 5 wt%, named OL-4.

[0064] Example 5

[0065] This embodiment 5 provides a superhydrophobic modification method based on carbonate rock cores. The only difference from embodiment 1 is that the modifiers are OL-1 and OL-4, and the mass ratio of OL-1 to OL-4 is 1:1.

[0066] Example 6

[0067] This embodiment 6 provides a superhydrophobic modification method based on carbonate rock cores. The only difference from embodiment 1 is that the modifiers are OL-1, OL-2 and OL-4, and the mass ratio of OL-1, OL-2 and OL-4 is 1:1:1.

[0068] Comparative Example 1

[0069] Comparative Example 1 uses unmodified calcite to verify the hydrophobic effect of unmodified carbonate rocks.

[0070] Comparative Example 2

[0071] Comparative Example 2 uses only polysiloxane to modify carbonate rocks without adding superhydrophobic nano-silica. The modification method is the same as in Example 1 to verify the hydrophobic effect of carbonate rocks after polysiloxane modification.

[0072] Comparative Example 3

[0073] In this example, ratio 3 uses octadecyl methoxysilane and polytetrafluoroethylene to modify carbonate rocks in order to verify the modification effect of conventional modifiers on carbonate rocks. The modification method is basically the same as that in Example 1, except that OL-1 is replaced with octadecyl methoxysilane and polysiloxane and stearic acid are replaced with polytetrafluoroethylene.

[0074] To better understand the present invention, the carbonate rocks or intermediate products obtained in Examples 1-6 and Comparative Examples 1-3 were tested using the following methods:

[0075] Test Example 1

[0076] Test Example 1 is used to test the water absorption rate of superhydrophobic nano-silica. The test method is as follows:

[0077] Take a certain amount of superhydrophobic nano-silica powder, sprinkle it on a clean glass slide and record the weight as m1. Add deionized water to the top of the powder and wait for it to absorb water automatically for 5 minutes. Then, use absorbent paper to wipe away the surface water droplets and record the mass of the superhydrophobic nano-silica powder agglomerates as m2. Calculate the water absorption rate η using the following formula. w .

[0078]

[0079] It should be noted that, in order to obtain the water absorption rate effect diagram, multiple sets of experiments were conducted on the OL modifier series in Examples 1-4, with concentrations of 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, and 5wt%, respectively.

[0080] Tests were conducted on Examples 1 (OL-1), 2 (OL-2), 3 (OL-3), and 4 (OL-4), and the test results are as follows. Figure 1 As shown in the figure, the data shows that for OL-1, the water absorption rate of nano-SiO2 is close to 100% at a concentration of 0.5wt%, and decreases to 25.05% when the concentration increases to 5wt%; for OL-2, the water absorption rate is only 1.70% at 3wt%; for OL-3, the water absorption rate decreases significantly to 8.75% after the concentration increases to 3wt%, and the change in water absorption rate is small with the continuous increase of concentration; for OL-4, the water absorption rate of nano-SiO2 is as high as 83.38% at a concentration of 0.5wt%, and decreases to 8.83% when the concentration increases to 3wt%, and the change in water absorption rate is small with the continuous increase of concentration.

[0081] Test Example 2

[0082] Test Example 2 is used to test the oil absorption rate of superhydrophobic nano-silica. The test method is as follows:

[0083] Measure 25 mL of deionized water using a 50 mL graduated cylinder. Weigh 1 g of superhydrophobic nano-silica powder using a balance and add it to the water; the powder floats on the surface. Pour toluene into a burette and slowly titrate it into the graduated cylinder until the powder is completely wetted. Record the volume of toluene added at this point as V. Calculate the oil absorption rate η using the following formula. O .

[0084]

[0085] It should be noted that, in order to obtain the oil absorption rate effect diagram, multiple sets of experiments were conducted on the OL modifier series in Examples 1-4 with concentrations of 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, and 5wt%, respectively.

[0086] Tests were conducted on Examples 1 (OL-1), 2 (OL-2), 3 (OL-3), and 4 (OL-4), and the test results are as follows. Figure 2 As shown in the figure, the data shows that OL-1 has an oil absorption rate of 5.58% for nano-SiO2 at a concentration of 0.5wt%, which increases to 70.08% when the concentration increases to 5wt%; OL-2 has an oil absorption rate of 78.24% at 3wt%; OL-3 has an oil absorption rate that decreases to 52.72% at a concentration of 2wt%, but increases significantly to 78.15% at 3wt%, with little change in oil absorption rate as the concentration continues to increase; OL-4 has an oil absorption rate of only 17.65% for nano-SiO2 at a concentration of 0.5wt%, which increases significantly to 77.60% at 3wt%, with little change in oil absorption rate as the concentration continues to increase.

[0087] Test Example 3

[0088] Test Example 3 is used to test the droplet wetting contact angle of superhydrophobic nano-silica. The test method is as follows:

[0089] A grooved quartz slide was ultrasonically cleaned in toluene and methanol for 25 minutes, followed by multiple rinsings with deionized water. Finally, the slide was dried in a 75°C oven for later use. A certain amount of superhydrophobic nano-silica powder was placed in the groove of the slide and pressed with a glass slide for 5 minutes. Then, the contact angle measuring instrument was turned on, and the camera light source was adjusted so that the slide was located in the display area of ​​the test software. The density and related parameters of the measured deionized water and the measured superhydrophobic nano-silica were set, and the micro-pump speed was set to 1 μL / s. Deionized water was dropped into the sample interface for 5 seconds. After the droplet stabilized for 5 minutes, the droplet state was quickly photographed and recorded by the software. Then, the wetting contact angle of the droplet was determined by Young's equation.

[0090] It should be noted that during the testing, multiple sets of experiments were conducted on the OL modifier series in Examples 1-4, with concentrations of 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, and 5wt%, respectively.

[0091] Tests were conducted on Examples 1 (OL-1), 2 (OL-2), 3 (OL-3), and 4 (OL-4), and the test results are as follows. Figure 3 As shown in the figure, the data shows that when the concentration of the modifier (OL) reaches 3wt%, the interfacial wetting contact angle reaches a stable state.

[0092] Tests were conducted on Examples 5 and 6, and the test results are as follows: Figure 4 As shown, according to Figure 4 When the modifiers are combined, the wetting contact angle increases to 145.91° when OL-1:OL-4 is 1:1, and to 151.58° when OL-1:OL-2:OL-4 is 1:1:1. This is mainly because long carbon chains and metal and non-metal alkyl segments are attached to the particle surface, and the combination of metal X (OCOR') with non-metal RSiOH increases the nano-dispersion, resulting in an air layer in the contact state between the liquid and the particle surface, causing the liquid to exhibit a Cassie state, thus resulting in a wetting contact angle greater than 150°.

[0093] Test Example 4

[0094] Test Example 4 in this paper is used to test the roll-off angle of superhydrophobic nano-silica. The test method is as follows:

[0095] The contact angle meter measures the liquid-solid contact angle by using a 5 μL deionized water droplet at room temperature using the seated drop method. The average of five measurements of all samples is recorded as the liquid-solid contact angle. The roll-off angle is the critical angle formed by the inclined interface and the horizontal plane when the droplet just rolls on the inclined interface, denoted by α.

[0096] It should be noted that during the testing, multiple groups of rock powder were set up according to the rock powder ratio of calcite:dolomite mass ratio of 5:0, 4:1, 3:2, 2:3, 1:4 and 0:5 in the mixed rock cores of Examples 1-3.

[0097] The superhydrophobic nano-silica obtained in Examples 1-3 were tested. The test results of Example 1 are as follows: Figure 5 As shown, the test results of Example 2 are as follows: Figure 6 As shown, the test results of Example 3 are as follows: Figure 7 As shown in the figure, the data shows that the contact angle of nano-SiO2 modified with OL-4 at the core interface with different proportions is much greater than 140°, exhibiting a strong hydrophobic state, which is not affected by the mineral ratio. The roll-off angle averages 3° under different mineral ratios, which means that it still has superhydrophobic properties and does not change with the mineral ratio. Therefore, the superhydrophobic nano-SiO2 modified with 2.5 mg / L PD + 1.0 mg / L stearic acid + 30% OL-4 can modify cores with different mineral compositions into a strong hydrophobic state.

[0098] Test Example 5

[0099] Test Example 5 was used to test the droplet rolling effect on the surface of carbonate rocks. Core samples of superhydrophobic nano-silica prepared in Example 3 with different mineral ratios were tested. The test method was as follows:

[0100] The roll-off angle was measured using a contact angle meter with a 5 μL deionized water droplet at room temperature via the seated drop method. The test results are as follows: Figure 8 As shown in the figure, the contact angle of the superhydrophobic nano-silica at the core interface with different mineral ratios is greater than 135°, exhibiting a strong hydrophobic state. The roll-off angle averages 9° with different mineral ratios and does not change with the mineral ratio. This indicates that when the roll-off angle of the droplet is measured at the modified interface, due to its hydrophobic properties, the droplet cannot land on the core and begins to roll after 0.03s.

[0101] Test Example 6

[0102] Test Example 6 was used to test the salt and temperature resistance of the modified carbonate rock cores. Contact angle and roll-off angle tests were performed on the carbonate rock cores from Example 1 and Comparative Example 1. The test results are as follows: Figure 9 and Figure 10 As shown in the figure, the modified carbonate rock core at 120℃ under 3×10⁻⁶ ℃ 5After soaking in mg / L water for 10 days, the contact angle and roll-off angle decreased slightly. When soaked in high-mineralization ions, the roll-off angle increased slightly, with the average roll-off angle for different mineral proportions after wetting being approximately 4–7°. After soaking the superhydrophobic modified core in high-mineralization water for 10 days, although a small amount of salt particles precipitated at the core interface, "cavitation" was still observed between the droplets and the core interface, thus maintaining its superhydrophobic properties. Figure 10 As shown.

[0103] It should be noted that when conducting contact angle and roll-off angle tests, multiple groups of rock powder were set up according to the calcite and dolomite mixed rock cores in Example 1 with rock powder ratios of 5:0, 4:1, 3:2, 2:3, 1:4 and 0:5.

[0104] Test Example 7

[0105] Test Example 7 was used to test the water-blocking and gas-free effect of modified carbonate rock cores. The injection port pressure was tested at different seepage velocities and the water phase flow velocity was tested at different injection pressure differentials for Example 3 and Comparative Examples 1-2.

[0106] In the aqueous phase test, the test results are as follows: Figure 11 and Figure 12 As shown in the figure, the core displacement pressure after PD modification (Comparative Example 2) shows an increasing trend under different displacement rates. The core displacement pressure after PD + 30% superhydrophobic nano silica (Example 3) modification is twice that without nanoparticles at a low speed of 0.01 mL / min. When the speed is increased to 0.1 mL / min, the displacement pressure increases less. The combination of ultra-low interfacial force and nanoparticles modifies the fracture into superhydrophobic. The seepage resistance of deionized water at low speed is much higher than that of PD-modified fractures.

[0107] In gas phase testing, the test results are as follows: Figure 13 As shown in the figure, it can be seen that the gas phase flow velocity of the crack after PD superhydrophobic modification (Comparative Example 2) is higher than that of the unmodified crack (Comparative Example 1) under different displacement pressure differences. The gas phase flow velocity increased by 16.95%, 30.13%, 32.57%, 63.94%, 75.58%, and 47.67% under displacement pressure differences of 0.5~4.0 MPa. The gas phase flow velocity of the crack modified with PD+30% superhydrophobic nano silica further increased on the basis of PD modification. The gas phase flow velocity growth rates were 50.44%, 59.52%, 60.10%, 63.22%, 82.26%, and 68.05% under displacement pressure differences of 0.5~4.0 MPa.

[0108] In the gas-liquid two-phase test, the test results are as follows: Figure 14As shown in the figure, the core samples after PD modification (Comparative Example 2) exhibit a weakly hydrophobic and aerophilic interface, resulting in an increase in the relative seepage velocity of the water phase of 80.95%, 73.75%, 54.09%, 27.41%, 15.85%, and 18.23% under a displacement pressure difference of 0.5–4.0 MPa. However, the core samples modified with PD + 30% superhydrophobic nano-silica exhibit a significantly higher relative seepage velocity of the water phase under the same displacement pressure difference compared to the PD-modified core samples. The increase rates of water phase seepage velocity under pressure differentials of 0.5–4.0 MPa were 105.24%, 182.24%, 144.97%, 85.53%, 44.15%, and 50.22%, respectively. 30% superhydrophobic nano-silica synergistic with PD can make cracks superhydrophobic. “Voids” exist at the interface between water and cracks, resulting in negative slip of the liquid at the interface. Under the same pressure differential, the relative seepage rate of deionized water phase is much higher than that of unmodified water (Comparative Example 1).

[0109] Test Example 8

[0110] Test Example 8 was used to test the contact angle of the conventional hydrophobic modifier in Comparative Example 3. The test results are as follows: Figure 15 and Figure 16 As shown, by Figure 15 It can be seen that the modifier in Comparative Example 3 did not roll off even when the tilt angle reached 53.23°. Figure 16 It can be seen that the droplets still hang on the surface of the rock core when it is at a 90° angle.

[0111] The same tests were performed on the modified carbonate rock core from Example 3, and the test results are as follows: Figure 17 As shown in the figure, the droplet begins to roll when the tilt angle is 3.09°, and the hydrophobic effect is significantly improved compared to Comparative Example 3. Figure 15 and Figure 17 This clearly demonstrates that the hydrophobic effect of conventional hydrophobic modifiers is significantly different from that of the embodiments of this invention.

[0112] Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible subranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the range referred to.

[0113] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A superhydrophobic modifier based on carbonate rock cores, characterized in that, The superhydrophobic modifier is composed of polysiloxane solution, stearic acid, and superhydrophobic nano silica. The superhydrophobic nano-silica is obtained by modifying nano-silica in a solvent with a modifier at a concentration of 0.5~5wt%; The solvent is composed of N,N-dimethylformamide, tetrahydrofuran and carbon tetrachloride in a mass ratio of (5~6):2:(1~2); The concentration of the polysiloxane is 1.5~2.5 mg / L, and the concentration of the stearic acid is 0.1~1 mg / L; The modifier includes at least one of alkylsilane coupling agents and aluminate coupling agents.

2. The modifier according to claim 1, characterized in that, The superhydrophobic nano-silica in the superhydrophobic modifier has a mass percentage of 10-30%.

3. The modifier according to claim 1, characterized in that, The alkylsilane coupling agent includes at least one of isooctyltriethoxysilane, dodecyltriethoxysilane, and n-octyltrimethoxysilane.

4. The modifier according to claim 3, characterized in that, The preparation method of the alkylsilane coupling agent is as follows: The alkylsilane is catalytically hydrolyzed in the solvent, and 0.1-0.5% hydrochloric acid or sulfuric acid is added to accelerate the catalytic hydrolysis to obtain the alkylsilane coupling agent.

5. The modifier according to claim 1, characterized in that, The preparation method of the superhydrophobic nano-silica is as follows: The nano-silica was dispersed in the solvent, the modifier was added, and the mixture was ultrasonically dispersed for 20 min, stirred at 3000 r / min for 20 min, and modified at 75°C for 10-12 h. After washing, centrifugation, drying and grinding, the superhydrophobic nano-silica was obtained.

6. The modifier according to claim 1, characterized in that, The preparation method of the superhydrophobic modifier is as follows: The polysiloxane and stearic acid are dissolved in the solvent, and the superhydrophobic nano silica is added and dispersed evenly to obtain the superhydrophobic modifier.

7. A method for superhydrophobic modification based on carbonate rock cores, using the superhydrophobic modifier according to any one of claims 1-6, characterized in that, Includes the following steps: The carbonate rock core slices were placed in the superhydrophobic modifier and modified at 120°C for 6 hours to obtain carbonate rock cores with preliminary surface modification. The surface-modified carbonate rock core was dried at 60°C for 6-10 hours to obtain superhydrophobic carbonate rock.

8. The method according to claim 7, characterized in that, The modified superhydrophobic carbonate rock has a contact angle ≥135° and a roll-off angle ≤9°.

9. The method according to claim 7, characterized in that, The carbonate rock core includes one or more of calcite, dolomite, and a mixture of real carbonate rock cores.

10. The application of a superhydrophobic modification method based on carbonate rock cores as described in any one of claims 7-9 in water control and production enhancement of carbonate gas reservoirs.

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