Rock modifier and application thereof in tight gas reservoir exploitation

Abstract

The invention discloses a rock modifier and application thereof in tight gas reservoir exploitation, and relates to the technical field of oil and gas exploitation, the rock modifier comprises the following components by weight: 10-30 parts of 3-aminopropyltrimethoxysilane, 20-40 parts of perfluorinated organic acid or perfluorinated organic acid salt, and 40-80 parts of a 40-60vt% ethanol solution. The invention further discloses application of the rock modifier in hydrophobic and oleophobic modification of the rock surface and exploitation of tight gas reservoirs. The rock modifier can perform stable hydrophobic and oleophobic modification on the rock surface, is resistant to high temperature and scouring, can maintain the wettability improvement effect for a long time, has the effects of guaranteeing smooth flowback of fracturing fluid and improving the oil and gas recovery ratio, and has a relatively high application value in tight gas reservoir exploitation.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas exploitation, and in particular to a rock modifier and application thereof in the exploitation of tight gas reservoirs. Background Art

[0002] Tight gas reservoirs are mainly composed of micron and nanometer pores, which are the main storage space for natural gas. During fracturing operations, the fracturing fluid first fills the macropores and then penetrates into the microcracks. Macropores are easy to discharge fracturing fluid due to their high porosity, while micropores and microcracks cause fracturing fluid retention due to their strong capillary force, affecting the overall flowback efficiency.

[0003] During the fracturing process, the fracturing fluid will penetrate into the matrix pore throats. Due to the influence of capillary resistance, it is difficult for the fracturing fluid immersed in the pores to flow back smoothly, resulting in water lock damage and affecting production capacity. According to the capillary force theory, the capillary binding resistance of the fracturing fluid depends on its surface tension and the contact angle on the surface of the reservoir rock pores. Therefore, the development of new rock modifiers, the improvement of rock wettability, and the smooth flow back of fracturing fluid are of great significance to the recovery of permeability of low-permeability gas reservoirs and the improvement of gas well production capacity. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide a rock modifier and its application in the exploitation of tight gas reservoirs. The rock modifier can perform stable hydrophobic and oleophobic modification on the rock surface, is resistant to high temperature and erosion, can maintain the wettability improvement effect for a long time, and has the effect of ensuring smooth return of fracturing fluid and improving oil and gas recovery rate. It has great application value in the exploitation of tight gas reservoirs.

[0005] The technical solution of the present invention to solve the above technical problems is as follows: a rock modifier is provided, comprising the following components in parts by weight: 10-30 parts of 3-aminopropyltrimethoxysilane, 20-40 parts of perfluoroorganic acid or perfluoroorganic acid salt, and 40-80 parts of 40-60vt% ethanol solution.

[0006] Furthermore, the perfluoroorganic acid is at least one of perfluorohexanoic acid, perfluoroheptanoic acid and perfluorooctanoic acid.

[0007] Furthermore, the perfluoro organic acid salt is at least one of ammonium perfluorohexanoate, ammonium perfluoroheptanoate, sodium perfluorooctanoate and tetramethylammonium perfluorooctanoate.

[0008] The present invention also provides the use of the above rock modifier in the hydrophobic and oleophobic modification of rock surfaces.

[0009] The present invention also provides application of the rock modifier in the exploitation of tight oil and gas reservoirs.

[0010] Further, it is applied to carbon dioxide fracturing.

[0011] Furthermore, the injection volume of the fracturing fluid containing the rock modifier is 0.05-0.10 PV.

[0012] The present invention has the following beneficial effects:

[0013] 1. The 3-aminopropyltrimethoxysilane molecule in the rock modifier of the present invention contains (OCH3)3Si- and NH2- groups. When it is added to liquid carbon dioxide and injected into the reservoir, Figure 1 As shown, the silanol generated by the hydrolysis of (OCH3)3Si- can react with the hydroxyl groups on the rock surface to produce a covalent bond chemical reaction and introduce amino groups into the rock surface. The amino groups undergo a condensation reaction with the carboxyl groups in an acidic environment and under reservoir geothermal conditions, stably introducing fluorocarbon chains, thereby forming a hydrophobic and oleophobic modified interface on the rock surface.

[0014] 2. The wettability of the rock treated with the rock modifier of the present invention is excellent, and the contact angles of water and oil are both greater than 90°. The modified rock surface has the advantages of high temperature resistance and erosion resistance, and can maintain the wettability improvement effect for a long time, ensuring smooth return of the fracturing fluid and improving the dialysis recovery rate of oil and gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the rock surface reaction principle;

[0016] Figure 2 is the contact angle of the core surface after modification at different temperatures;

[0017] Figure 3 Figure 1 shows the results of the scour resistance test for rock surface modification;

[0018] Figure 4 This is the result diagram of the effect of rock surface modification on the flowback rate. DETAILED DESCRIPTION

[0019] The principles and features of the present invention are described below, and the examples are only used to explain the present invention and are not used to limit the scope of the present invention. If no specific conditions are specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0020] Example 1

[0021] A rock modifier comprises the following components in parts by weight: 20 parts of 3-aminopropyltrimethoxysilane, 30 parts of perfluorohexanoic acid and 50 parts of 50vt% ethanol solution.

[0022] Example 2

[0023] A rock modifier comprises the following components in parts by weight: 10 parts of 3-aminopropyltrimethoxysilane, 20 parts of sodium perfluorooctanoate, and 80 parts of 40vt% ethanol solution.

[0024] Example 3

[0025] A rock modifier comprises the following components in parts by weight: 30 parts of 3-aminopropyltrimethoxysilane, 40 parts of perfluoroheptanoic acid, and 40 parts of 60vt% ethanol solution.

[0026] Test Example 1 Contact Angle

[0027] 0.05% of the rock modifier of Example 1 was added, and the temperature conditions were set at 25°C, 40°C, 60°C, 80°C, 100°C and 120°C, respectively. The reaction time was 30 min, and the effect of temperature on the contact angle of the core slice was measured. The results are as follows: Figure 2 shown.

[0028] Depend on Figure 2 It can be seen that the rock flakes and rock modifiers can react in a wide temperature range of 25°C to 120°C. When the reaction temperature is 25°C, the reaction efficiency is relatively low, showing a certain degree of hydrophobicity, but the effect is not significant. As the reaction temperature increases, the hydrophobicity of the rock flake surface changes significantly. When the reaction temperature increases, the contact angle of the treated rock flake surface exceeds 120°, showing strong hydrophobicity. This result shows that high temperature conditions help to improve the reaction efficiency between the rock modifier and the rock flakes, thereby enhancing the hydrophobicity of the rock flakes. The results show that within the high temperature range of 60-120°C, the rock flakes can achieve a good hydrophobic state. In practical applications, rock modifiers can be successfully used in high-temperature reservoirs to achieve effective regulation of the hydrophobicity of the rock surface.

[0029] Test Example 2 Modified Strength

[0030] The core was surface modified with 0.05% rock modifier, and the initial wetting contact angle was measured after drying. The core was placed in a core holder and flushed with fracturing fluid. The seepage linear velocities were 0.05m / d, 0.10m / d, 1.5m / d, 2.0m / d and 4.0m / d, and the flushing time was 14d. After the flushing, the core was taken out and dried. The wetting contact angle was measured multiple times at different positions, and the average value was calculated to explore the stability of the low permeability core after continuous fluid flushing and the change law of wettability. The results are shown in Figure 3 shown.

[0031] Depend on Figure 3It can be seen that after continuous flushing of fracturing fluid at different linear velocities, the wetting contact angle of the core decreased slightly, but the change in the wetting contact angle was small, and it still showed good hydrophobic performance, indicating that the rock modifier has a strong binding force with the rock surface and will not be easily peeled off due to external force. Unlike the adsorption and retention of ordinary surfactants, the chemical bonds produced by the reaction of rock modifiers with rocks are strong, and the covalent bonds formed increase the adhesion and interaction between the rock modifier and the rock surface, so that the rock modifier can still be firmly attached to the rock surface when flushed and is not easy to fall off. This characteristic gives the rock modifier the ability to continue to play a role throughout the entire process of fracturing fluid flowback construction. It can not only effectively maintain the hydrophobic properties of the rock surface, but also have a positive impact on improving the fracturing effect and increasing the recovery rate of gas reservoirs.

[0032] Test Example 3 Flowback Rate

[0033] The permeability is selected to be about 0.3×10 -3 μm 2 Experiments were conducted on cores with porosity less than 10%, length of about 5 cm, diameter of about 2.5 cm and similar lithology. They were divided into two groups. Fracturing fluid with a rock modifier mass concentration of 0.05% was injected into one group of cores, and pure fracturing fluid was injected into the other group of cores. The flowback rate was tested under different injection rates. The results are as follows Figure 4 shown.

[0034] Depend on Figure 4 It can be seen that the core injected with fracturing fluid containing rock modifier has a much higher flowback rate than the unmodified core under the same injection volume. Under the condition of a small injection volume of rock modifier, the flowback rate can reach 50%, which shows that the rock modifier carried by the fracturing fluid can more fully travel in the low-permeability capillaries, and the modified rock surface covers a wider area, thereby displacing the fracturing fluid retained in the micro-pores to the greatest extent. After the injection volume of rock modifier reaches a certain value, the flowback effect will not continue to be significantly improved, and the flowback rate tends to be stable. The best flowback effect can be achieved by adding rock modifier to 0.05-0.10PV fracturing fluid.

[0035] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A rock modifier, characterized in that: The invention comprises the following components in parts by weight: 10-30 parts of 3-aminopropyltrimethoxysilane, 20-40 parts of perfluoro organic acid or perfluoro organic acid salt, and 40-80 parts of 40-60vt% ethanol solution.

2. The rock modifier according to claim 1, characterized in that The perfluoro organic acid is at least one of perfluorohexanoic acid, perfluoroheptanoic acid and perfluorooctanoic acid.

3. The rock modifier according to claim 1, characterized in that The perfluoro organic acid salt is at least one of ammonium perfluorohexanoate, ammonium perfluoroheptanoate, sodium perfluorooctanoate and tetramethylammonium perfluorooctanoate.

4. Use of the rock modifier according to any one of claims 1 to 3 in hydrophobic and oleophobic modification of rock surfaces.

5. Use of the rock modifier according to any one of claims 1 to 3 in the exploitation of tight gas reservoirs.

6. The use according to claim 5, characterized in that Application in carbon dioxide fracturing.

7. The use according to claim 6, characterized in that The injection amount of the fracturing fluid containing the rock modifier is 0.05-0.10PV.

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