Interface wetting regulator for tight gas reservoir water control fracturing and preparation method of interface wetting regulator
By preparing a nanoparticle interface wetting regulator with multiple adsorption sites, the problem of water flow channels after fracturing in tight gas reservoirs was solved, the flowback rate of fracturing fluid was improved, and the production enhancement effect of tight gas reservoirs was achieved.
Patent Information
- Application Number
- CN202411537270.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-31
- Publication Date
- 2026-05-01
AI Technical Summary
In existing technologies, tight carbonate gas reservoirs are prone to forming water channels after acid fracturing, which leads to increased water content and shortens the production enhancement period. Commonly used surfactants and silane coupling agents are unstable in high-temperature and high-salt environments, affecting the properties of fracturing fluids and making them susceptible to corrosion.
Ultra-small nanoparticles were prepared by cellulose acid hydrolysis and hydrothermal method, and then compounded with Gemini surfactant and quaternary ammonium salt cationic surfactant to form an interfacial wetting regulator with multiple adsorption sites, which improves rock wettability and reduces aqueous phase permeability.
It improved the flowback rate of fracturing fluid, realized water-controlled fracturing and increased production in tight gas reservoirs, and solved the problem of inapplicability of wetting regulation performance under high temperature and high salinity conditions.
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Figure CN121950277A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of nanomaterial reservoir modification technology, specifically to an interface wetting modifier for controlled water fracturing in tight gas reservoirs and its preparation method. Background Technology
[0002] Tight carbonate gas reservoirs are characterized by complex pore structures, small pore sizes, and numerous micro / nanoscale pores and microfractures. Acid fracturing is a widely used production enhancement measure in the development of tight carbonate gas reservoirs. However, in tight gas reservoirs with abundant mobile water in the gas-water co-existing layer, the artificial fractures created after acid fracturing can become channels for formation water flow, causing a rapid increase in water cut. This shortens the effective period of fracturing-enhanced production, leading to a decrease in gas production or even production shutdown. To address the water production problem after fracturing in tight gas reservoirs, selective water-blocking agents need to be added to the gas well for reservoir stimulation.
[0003] Selective water shut-off agents are mainly divided into two categories: selective aqueous phase plugging agents and phase permeability modifiers. The former includes polymers, active heavy oil, oil-soluble resins, and oil-based cement, but selective plugging agents are too large or difficult to apply, making them unsuitable for fracturing and developing tight gas reservoirs. The latter includes copolymers or their weak gel systems, surfactants and their compound systems, nanoemulsions, modified nanoparticles, and other nanomaterials. Among these, copolymers and their weak gel systems, due to their large size, can only be used for water shut-off in medium-to-high permeability formations and are not suitable for tight gas reservoirs with low or ultra-low permeability. For tight gas reservoirs, surfactants and silane coupling agents can enter the micro / nano-scale pores, improving reservoir rock wettability and reducing aqueous phase permeability. However, commonly used cationic surfactants adsorb onto the rock surface through physical adsorption, which is greatly affected by high-temperature and high-salt environments and has poor erosion resistance. While silane coupling agents are chemically adsorbed, they are easily hydrolyzed in neutral environments to form cross-linking products, leading to pore blockage in tight gas reservoirs. Although the hydrolysis of silane coupling agents can be inhibited in acidic environments, adding them to fracturing fluids can severely affect the properties of the fracturing fluids, and adding them alone can also cause certain corrosion problems.
[0004] To address the aforementioned issues, this invention utilizes cellulose to prepare ultra-small nanoparticles via acid hydrolysis and hydrothermal methods. Compared to surfactants, these nanoparticles possess multiple adsorption sites and high surface properties, exhibiting stronger adsorption on rock surfaces and excellent wetting properties. They can transform hydrophilic surfaces into a neutral wetting state, reducing aqueous permeability. Simultaneously, their low surface tension enhances fracturing fluid flowback rates, enabling water-controlled fracturing and increased production in tight gas reservoirs. Summary of the Invention
[0005] The purpose of this invention is to provide an interface wetting modifier for water-controlled fracturing in tight gas reservoirs and its preparation method, so as to solve the problem that surfactants and silane coupling agents are not suitable for interface wetting regulation in high-temperature and high-salinity tight gas reservoirs.
[0006] The present invention is achieved as follows: According to one aspect of the present invention, a method for preparing an interface wetting modifier for water-controlled fracturing in tight gas reservoirs is provided, comprising the following steps:
[0007] S100, Acid hydrolysis of cellulose;
[0008] S200, The cellulose acid hydrolysis product and Gemini surfactant are subjected to a hydrothermal reaction;
[0009] S300: The quaternary ammonium salt cationic surfactant is compounded with the product of step S200 to obtain an interface wetting regulator for water-controlled fracturing of high-temperature and high-salinity tight gas reservoirs.
[0010] Furthermore, the cellulose is cellulose powder with a particle size of 20–250 μm.
[0011] Furthermore, the Gemini surfactant is a carboxylic acid-based Gemini surfactant.
[0012] Furthermore, the carbon chain of the carboxylic acid Gemini surfactant is C12 to C18, preferably C18.
[0013] Furthermore, the linking group of the carboxylic acid Gemini surfactant is C2 to C8, preferably C2.
[0014] Furthermore, in step S100, 5.0 g of cellulose is dissolved in 50 mL of 1 mol / L to 5 mol / L nitric acid solution, the acid hydrolysis temperature is 70 °C, the acid hydrolysis time is 2 to 12 hours, and after the acid hydrolysis is completed, the pH of the solution is adjusted to neutral with NaOH.
[0015] Furthermore, in step S200, a certain amount of carboxylic acid Gemini surfactant is added to the solution obtained in step S100 to carry out a hydrothermal reaction, and the mass ratio of cellulose to Gemini surfactant is 1:0.1 to 1:1.
[0016] Furthermore, the temperature of the hydrothermal reaction is 160℃~240℃, and the reaction time is 8 hours~24 hours.
[0017] Furthermore, the quaternary ammonium salt cationic surfactant is a C12 to C18 quaternary ammonium salt cationic surfactant, preferably octadecyltrimethylammonium chloride; the mass ratio of the quaternary ammonium salt cationic surfactant to cellulose is 100:1 to 100:8.
[0018] According to a second aspect of the present invention, the present invention provides an interface wetting modifier for controlled water fracturing in tight gas reservoirs, which is prepared using the above-mentioned method for preparing an interface wetting modifier for controlled water fracturing in tight gas reservoirs.
[0019] Compared with existing technologies, the beneficial effects of this invention are as follows: The interface wetting modifier for controlled water fracturing in tight gas reservoirs prepared by the method provided by this invention has multiple adsorption sites and high surface properties, resulting in stronger adsorption on rock surfaces and excellent wetting performance. It can transform hydrophilic surfaces into a neutral wetting state, reducing the permeability of the aqueous phase. Simultaneously, its low surface tension can improve the flowback rate of fracturing fluid, thereby achieving increased production through controlled water fracturing in tight gas reservoirs. Attached Figure Description
[0020] Figure 1 This is a comparison chart of aqueous phase permeability curves before and after modification with an interface wetting modifier for water-controlled fracturing in tight gas reservoirs;
[0021] Figure 2 This is a comparison chart of gas phase permeability curves before and after modification with an interface wetting modifier for water-controlled fracturing in tight gas reservoirs. Detailed Implementation
[0022] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.
[0023] The following description, in conjunction with the accompanying drawings and specific embodiments, provides further details:
[0024] Example 1
[0025] This embodiment provides a method for preparing an interface wetting modifier for water-controlled fracturing in tight gas reservoirs, and further evaluates its wetting performance and surface activity. The preparation steps are as follows:
[0026] 5.0g of particles with a diameter of 20 μCellulose powder of mass m was added to 50 mL of 2 mol / L nitric acid and acid-hydrolyzed at 70 °C for 8 hours. The pH of the solution was then adjusted to neutral with NaOH. A carboxylic acid Gemini surfactant with a C18 carbon chain and a C2 linking group was dissolved in the acid-hydrolyzed solution at a mass ratio of cellulose to Gemini surfactant of 1:0.5. The mixture was then hydrothermally reacted at 200 °C for 12 hours. Octadecyltrimethylammonium chloride was weighed and added to the hydrothermal reaction solution at a mass ratio of 100:6 to cellulose, and stirred until homogeneous to obtain an interface wetting modifier for water-controlled fracturing in high-temperature, high-salinity tight gas reservoirs.
[0027] To evaluate the wetting control performance of the wetting modifier on hydrophilic glass slides: Glass slides and 0.3% of the wetting modifier were added to a brine solution (sodium chloride and calcium chloride at concentrations of 50 g / L and 5 g / L, respectively), and placed in a sealable high-temperature reactor. Modification was carried out at 110°C (formation temperature) for 12 hours. After the solution cooled, the surface tension and water droplet contact angle of the glass were measured using a surface tensiometer at 30°C. Then, the brine solution (without the wetting modifier) and the modified glass slides were placed in a high-temperature, high-pressure reactor and stirred at 300 rpm for 12 hours. After drying, the contact angle of the glass slides was measured to evaluate the erosion resistance of the wetting modifier.
[0028] The comparison of aqueous phase permeability curves before and after modification with the interfacial wetting modifier for controlled hydraulic fracturing of high-temperature, high-salinity tight gas reservoirs prepared in this embodiment is shown in the figure below. Figure 1 As shown in the figure, the gas phase permeability curves before and after modification with the interface wetting modifier for water-controlled fracturing of high-temperature, high-salinity tight gas reservoirs prepared in this embodiment are compared. Figure 2 As shown.
[0029] Example 2
[0030] This embodiment provides a method for preparing an interface wetting modifier for water-controlled fracturing in tight gas reservoirs, and further evaluates its wetting performance and surface activity. The preparation steps are as follows:
[0031] 5.0 g of cellulose powder with a particle size of 250 μm was added to 50 mL of 5 mol / L nitric acid and acid-hydrolyzed at 70 °C for 2 hours. The pH was then adjusted to neutral with NaOH. A carboxylic acid Gemini surfactant with a C16 carbon chain and a C4 linking group was dissolved in the acid-hydrolyzed solution at a mass ratio of cellulose to Gemini surfactant of 1:0.8. The mixture was then hydrothermally reacted at 240 °C for 8 hours. Octadecyltrimethylammonium chloride was weighed and added to the hydrothermal reaction solution at a mass ratio of 100:8 to cellulose. After thorough stirring, an interface wetting modifier for water-controlled fracturing in high-temperature, high-salinity tight gas reservoirs was obtained.
[0032] To evaluate the wetting control performance of the wetting modifier on hydrophilic glass slides: Glass slides and 0.3% of the wetting modifier were added to a brine solution (sodium chloride and calcium chloride at concentrations of 50 g / L and 5 g / L, respectively). The solution was placed in a sealable high-temperature reactor and modified at 110°C (formation temperature) for 12 hours. After cooling, the surface tension and water droplet contact angle of the glass were measured using a surface tensiometer at 30°C. Then, the brine solution (without the wetting modifier) and the modified glass slides were placed in a high-temperature, high-pressure reactor and stirred at 300 rpm for 12 hours. After drying, the contact angle of the glass slides was measured to evaluate the erosion resistance of the wetting modifier.
[0033] Example 3
[0034] This embodiment provides a method for preparing an interface wetting modifier for water-controlled fracturing in tight gas reservoirs, and further evaluates its wetting performance and surface activity. The preparation steps are as follows:
[0035] 5.0 g of cellulose powder with a particle size of 20 μm was added to 50 mL of 1 mol / L nitric acid and acid-hydrolyzed at 70 °C for 12 hours. The pH was then adjusted to neutral with NaOH. A carboxylic acid Gemini surfactant with a C12 carbon chain and a C18 linking group was dissolved in the acid-hydrolyzed solution at a mass ratio of cellulose to Gemini surfactant of 1:0.1. The mixture was then hydrothermally reacted at 160 °C for 24 hours. Dodecyltrimethylammonium chloride was weighed and added to the hydrothermal reaction solution at a mass ratio of 100:1 to cellulose. After thorough stirring, the interfacial wetting modifier for water-controlled fracturing in high-temperature, high-salinity tight gas reservoirs was obtained.
[0036] To evaluate the wetting control performance of the wetting modifier on hydrophilic glass slides: Glass slides and 0.3% of the wetting modifier were added to a brine solution (sodium chloride and calcium chloride at concentrations of 50 g / L and 5 g / L, respectively). The solution was placed in a sealable high-temperature reactor and modified at 110°C (formation temperature) for 12 hours. After cooling, the surface tension and water droplet contact angle of the glass were measured using a surface tensiometer at 30°C. Then, the brine solution (without the wetting modifier) and the modified glass slides were placed in a high-temperature, high-pressure reactor and stirred at 300 rpm for 12 hours. After drying, the contact angle of the glass slides was measured to evaluate the erosion resistance of the wetting modifier.
[0037] Comparative Examples 1-3
[0038] The wetting regulators used were octadecyltrimethylammonium bromide (C18TAB), sodium dodecyl sulfate (SDS), and fatty alcohol polyoxyethylene ether (AEO-9), respectively. Other test conditions were the same as in Examples 1-3. The comparative results are shown in Table 1.
[0039] Table 1 Comparison of Contact Angle and Surface Tension Data
[0040]
[0041] This invention first obtains small-molecule acid hydrolysis products from cellulose through acid hydrolysis, and then performs hydrothermal synthesis with Gemini surfactants containing hydrophobic chains to prepare ultra-small nanoparticles. The nanoparticles have hydrophilic groups of cellulose and Gemini surfactants, as well as hydrophobic carbon chains of Gemini surfactants, and are therefore amphiphilic.
[0042] The aforementioned nanoparticles are then combined with cationic surfactants. These cationic surfactants bind to the surface of the nanoparticles through electrostatic or hydrophobic interactions, thus dispersing them. Once inside the formation, the cationic surfactants adsorb onto the rock surface, regulating the wetting of surfaces where the nanoparticles have not yet adsorbed, ultimately achieving a synergistic effect in regulating the wetting of the rock.
[0043] Compared to surfactants, these nanoparticles possess multiple adsorption sites and high surface properties, exhibiting stronger adsorption on rock surfaces and excellent wetting properties. They can transform hydrophilic surfaces into a neutral wetting state, reducing aqueous permeability. Simultaneously, their low surface tension can improve fracturing fluid flowback rates, enabling water-controlled fracturing and increased production in tight gas reservoirs.
[0044] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for preparing an interface wetting modifier for water-controlled fracturing in tight gas reservoirs, characterized in that, Includes the following steps: S100, Acid hydrolysis of cellulose; S200, The cellulose acid hydrolysis product and Gemini surfactant are subjected to a hydrothermal reaction; S300: The quaternary ammonium salt cationic surfactant is compounded with the product of step S200 to obtain an interface wetting regulator for water-controlled fracturing of high-temperature and high-salinity tight gas reservoirs.
2. The method for preparing the interface wetting regulator for water-controlled fracturing in tight gas reservoirs according to claim 1, characterized in that, The cellulose is cellulose powder with a particle size of 20-250 μm.
3. The method for preparing the interface wetting regulator for water-controlled fracturing in tight gas reservoirs according to claim 1, characterized in that, The Gemini surfactant is a carboxylic acid-based Gemini surfactant.
4. The method for preparing the interface wetting regulator for water-controlled fracturing in tight gas reservoirs according to claim 3, characterized in that, The carbon chain of the carboxylic acid Gemini surfactant is C12 to C18, preferably C18.
5. The method for preparing the interface wetting regulator for water-controlled fracturing in tight gas reservoirs according to claim 3, characterized in that, The linking group of the carboxylic acid Gemini surfactant is C2 to C8, preferably C2.
6. The method for preparing the interface wetting regulator for water-controlled fracturing in tight gas reservoirs according to claim 1, characterized in that, In step S100, 5.0 g of cellulose is dissolved in 50 mL of 1 mol / L to 5 mol / L nitric acid solution. The acid hydrolysis temperature is 70 °C and the acid hydrolysis time is 2 to 12 hours. After the acid hydrolysis is completed, the pH of the solution is adjusted to neutral with NaOH.
7. The method for preparing the interface wetting regulator for water-controlled fracturing in tight gas reservoirs according to claim 6, characterized in that, In step S200, a certain amount of carboxylic acid Gemini surfactant is added to the solution obtained in step S100 to carry out a hydrothermal reaction, and the mass ratio of cellulose to Gemini surfactant is 1:0.1 to 1:
1.
8. The method for preparing the interface wetting modifier for water-controlled fracturing in tight gas reservoirs according to claim 7, characterized in that, The hydrothermal reaction temperature is 160℃~240℃, and the reaction time is 8 hours~24 hours.
9. The method for preparing the interface wetting modifier for water-controlled fracturing in tight gas reservoirs according to claim 1, characterized in that, The quaternary ammonium salt cationic surfactant is a C12 to C18 quaternary ammonium salt cationic surfactant, preferably octadecyltrimethylammonium chloride; the mass ratio of the quaternary ammonium salt cationic surfactant to cellulose is 100:1 to 100:
8.
10. An interface wetting modifier for water-controlled fracturing in tight gas reservoirs, characterized in that, It was prepared using the method for preparing the interface wetting regulator for controlled water fracturing of tight gas reservoirs as described in any one of claims 1-9.