CN118853127B - A plugging agent suitable for CO2 gas channeling - Google Patents
A plugging agent suitable for CO2 gas channeling Download PDFInfo
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Abstract
The invention provides a plugging agent suitable for CO 2 gas channeling and a preparation method thereof, and relates to the field of petroleum exploitation. The weight percentage is that the composition comprises 5-10% of acrylamide, 1-5% of acrylic acid, 1-5% of nano chitosan, 0.5-1% of bentonite, 1-5% of hydroxyethyl cellulose, 0.1-0.5% of initiator, 1-2% of cross-linking agent, 0.1-0.5% of surfactant and the balance of water. The preparation method comprises the steps of adding the acrylamide, bentonite and the surfactant into water, performing ultrasonic dispersion for 20-30min, adding nano chitosan and acrylic acid, uniformly stirring, adding the rest raw materials, and uniformly stirring. The plugging agent can be used in CO 2 gas flooding wells to prevent and control CO 2 gas channeling, and has high gel strength and good plugging effect after gel formation.
Description
Technical Field
The invention relates to the field of petroleum exploitation, in particular to a plugging agent suitable for CO 2 gas channeling and a preparation method thereof.
Background
CO 2 gas-driven oil extraction is achieved by injecting CO 2 gas into an oil layer, CO 2 has high solubility in oil and water, when the CO 2 gas is dissolved in crude oil in a large amount, can expand the volume of the crude oil, increases the elastic energy of the stratum, reduces the viscosity, and reduces the interfacial tension between oil and water. under appropriate pressure, temperature and crude oil composition conditions, CO 2 mixes with crude oil to form a miscible front, and thus a miscible liquid, forms a single liquid phase, to effectively displace formation crude oil to the production well. in addition, the acid formed after CO 2 is dissolved in water can also play a role in acidification, and is helpful for further improving the recovery ratio to improve the oil recovery ratio of an oil field. However, the CO 2 gas has low viscosity density, is easy to flow in an oil layer, and causes a channeling phenomenon. Secondly, factors such as heterogeneity of oil reservoirs, permeability, longitudinal heterogeneity of oil reservoirs, crack development, deposition characteristics, reservoir physical properties and the like can also cause that CO 2 is easy to flow in a channeling manner in the oil displacement process, CO 2 breaks through an oil-containing zone prematurely, is a large amount of crude oil is reserved in a stratum, crude oil recovery rate is reduced, CO 2 gas channeling can also cause abnormal fluctuation of gas pressure in a pipeline, influences the stability of system operation, pipeline condensation is caused, sealing filler leakage and the like. Therefore, it is important to take effective measures to prevent and control gas channeling during the CO 2 flooding process, .
The plugging material for preventing gas channeling mainly comprises gel, foam, organic amine salts, nano materials and the like, and the gel plugging material does not react with the cross-linking agent and the polymer basically when the base solution is prepared. After the base solution is injected into the stratum, the initiator obtains activity under the stratum condition and starts to initiate crosslinking polymerization reaction to generate gel to block the CO 2 gas channeling channel, so as to prevent and control the gas channeling. The gel plugging material can effectively plug a high permeable layer, but has poor injectability to a low permeable layer, low gel strength, low gel forming rate at high temperature and poor plugging effect.
Disclosure of Invention
The invention aims to provide a plugging agent suitable for CO 2 gas channeling, which can prevent and control CO 2 gas channeling, has high gel strength and long duration after gel formation, is not easy to crack in the acidic environment of CO 2, and has good stability and good plugging effect.
The invention further aims to provide a preparation method of the plugging agent suitable for CO 2 gas channeling, which is simple, and the plugging agent prepared by the method has good plugging effect in a CO 2 gas flooding well.
The invention solves the technical problems by adopting the following technical scheme.
On one hand, the embodiment of the invention provides a plugging agent suitable for CO 2 gas channeling, which comprises, by mass, 5-10% of acrylamide, 1-5% of acrylic acid, 1-5% of nano chitosan, 0.5-1% of bentonite, 1-5% of hydroxyethyl cellulose, 0.1-0.5% of an initiator, 1-2% of a cross-linking agent, 0.1-0.5% of a surfactant and the balance of water.
In some embodiments of the invention, the raw materials comprise, by mass, 5% of acrylamide, 1% of acrylic acid, 1% of nano chitosan, 0.5% of bentonite, 1% of hydroxyethyl cellulose, 0.1% of an initiator, 2% of a cross-linking agent, 0.1% of a surfactant, and the balance of water.
In some embodiments of the invention, the surfactant is one or more of sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, sodium dodecyl sulfate, betaine.
In some embodiments of the invention, the cross-linking agent is one of ethylene glycol dimethacrylate, N-methylenebisacrylamide.
In some embodiments of the invention, the initiator is one or more of potassium persulfate, sodium persulfate, ammonium persulfate.
In some embodiments of the invention, the nanoschitosan has a particle size of 100-200nm.
In some embodiments of the present invention, 1-2% by mass of a reinforcing agent is also included.
In some embodiments of the invention, the reinforcing agent comprises, by weight, 10-20 parts of citric acid, 1-5 parts of calcium carbonate powder, 1-5 parts of porous silica, 5-10 parts of chitosan, 10-20 parts of ethanol aqueous solution and 10-20 parts of sodium hydroxide solution.
In some embodiments of the invention, the enhancer is prepared by adding citric acid into an ethanol water solution, stirring and dispersing uniformly, adding chitosan, performing ultrasonic dispersion for 30-60min, adding calcium carbonate powder and porous silicon dioxide powder, performing ultrasonic dispersion for 30-60min, then dropwise adding into a sodium hydroxide solution, standing for 10-20h, and filtering to obtain the enhancer.
Firstly, dispersing citric acid and chitosan in an ethanol solution to enable part of functional groups of chitosan molecules to be carboxylated, then adding calcium carbonate and porous silicon dioxide, and dripping the uniformly dispersed calcium carbonate and the porous silicon dioxide into an alkaline solution, wherein carboxylated chitosan is taken as a shell, calcium carbonate and silicon dioxide are taken as cores in the alkaline solution, so that a porous core-shell structure is formed. The metal ions in the bentonite in the plugging agent are unstable, the citric acid group on the surface of the core-shell structure can be complexed with the metal ions through chelation, forms a stable chelate, the stable chelate is attached or adsorbed in the three-dimensional network structure of the gel, and the connection strength of the calcium carbonate and the silicon dioxide in the core-shell structure and the three-dimensional network structure is increased, so that the strength of the gel is increased.
On the other hand, the embodiment of the invention provides a preparation method of a plugging agent suitable for CO 2 gas channeling, which comprises the following steps of adding acrylamide, bentonite and a surfactant into water, performing ultrasonic dispersion for 20-30min, adding nano chitosan and acrylic acid, uniformly stirring, adding the rest raw materials, and uniformly stirring.
When the plugging agent is prepared, firstly, acrylamide, bentonite and a surfactant are dispersed in water, under the action of the surfactant, the bentonite and the acrylamide can be fully and uniformly dispersed to reduce the viscosity of a system, and then nano chitosan and acrylic acid are added for dispersion, so that the main raw materials forming gel are uniformly dispersed.
Compared with the prior art, the embodiment of the invention has at least the following advantages or beneficial effects:
The plugging agent provided by the invention is injected into a CO 2 gas drive well, an initiator is activated in the temperature environment of an oil well, and under the action of the initiator, acrylamide and acrylic acid undergo addition, crosslinking, polymerization and other reactions to generate macromolecules, so that gel is formed, and CO 2 gas channeling is plugged. In the process of polymerization reaction, nano chitosan can be adsorbed on the surface of a high molecular polymer, and the molecular chains of chitosan and ethyl cellulose contain hydroxyl groups, so that the hydroxyl groups can also participate in addition polymerization reaction to form a three-dimensional network structure. The main component of bentonite is montmorillonite, the montmorillonite has a unique 2:1 crystal structure, and is composed of two silicon oxygen tetrahedrons which are sandwiched by a layer of aluminum oxide octahedron, and the montmorillonite is added into acrylamide and acrylic acid, can participate in addition polymerization reaction, is combined with a polymerization main chain, is embedded into a network structure, and further increases the stability of gel. The surfactant can reduce the viscosity of the plugging agent system, thereby improving the injectability of the plugging agent, especially the injectability of the low-permeability layer. In addition, the hydroxyl groups in the chitosan and cellulose molecular chains in the raw materials can promote the hydrophilicity of the plugging agent system, so that the initial viscosity of the plugging agent system is reduced, and after the reaction, the chitosan and cellulose molecular chains can be grafted, entangled and the like with the main chains formed by acrylamide and acrylic acid, so that the viscosity and the strength of gel after gel formation are improved.
In conclusion, the plugging agent provided by the invention can be used in a CO 2 gas flooding well to prevent and control CO 2 gas channeling, and has high gel strength and good plugging effect after gel formation.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other. The present invention will be described in detail with reference to specific examples.
The features and capabilities of the present invention are described in further detail below in connection with the examples.
Example 1
The preparation method comprises the following steps of:
5% of acrylamide, 1% of acrylic acid, 1% of nano chitosan, 1% of bentonite, 1% of hydroxyethyl cellulose, 0.1% of an initiator (potassium persulfate), 2% of a cross-linking agent (ethylene glycol dimethacrylate), 0.1% of a surfactant (sodium dodecyl sulfate) and the balance of water. Wherein the average particle size of the nano chitosan is 150nm.
The blocking agent of this example was prepared as follows:
adding the acrylamide, bentonite and the surfactant into water, performing ultrasonic dispersion for 30min, adding nano chitosan and acrylic acid, stirring uniformly, adding the rest raw materials, and stirring uniformly.
Example 2
The preparation method comprises the following steps of:
10% of acrylamide, 5% of acrylic acid, 5% of nano chitosan, 0.5% of bentonite, 5% of hydroxyethyl cellulose, 0.4% of an initiator (potassium persulfate), 2% of a cross-linking agent (ethylene glycol dimethacrylate), 0.5% of a surfactant (sodium dodecyl sulfate) and the balance of water. Wherein the average particle size of the nano chitosan is 150nm.
The blocking agent of this example was prepared as follows:
adding the acrylamide, bentonite and the surfactant into water, performing ultrasonic dispersion for 30min, adding nano chitosan and acrylic acid, stirring uniformly, adding the rest raw materials, and stirring uniformly.
Example 3
The preparation method comprises the following steps of:
8% of acrylamide, 3% of acrylic acid, 3% of nano chitosan, 0.8% of bentonite, 3% of hydroxyethyl cellulose, 0.5% of an initiator (potassium persulfate), 1.5% of a cross-linking agent (ethylene glycol dimethacrylate), 0.3% of a surfactant (sodium dodecyl sulfate) and the balance of water. Wherein the average particle size of the nano chitosan is 150nm.
The blocking agent of this example was prepared as follows:
adding the acrylamide, bentonite and the surfactant into water, performing ultrasonic dispersion for 30min, adding nano chitosan and acrylic acid, stirring uniformly, adding the rest raw materials, and stirring uniformly.
Example 4
The preparation method comprises the following steps of:
5% of acrylamide, 1% of acrylic acid, 3% of nano chitosan, 1% of bentonite, 1% of hydroxyethyl cellulose, 0.1% of an initiator (potassium persulfate), 2% of a cross-linking agent (ethylene glycol dimethacrylate), 0.1% of a surfactant (sodium dodecyl sulfate) and the balance of water. Wherein the average particle size of the nano chitosan is 150nm.
The preparation method is the same as in example 1.
Example 5
The preparation method comprises the following steps of:
5% of acrylamide, 1% of acrylic acid, 5% of nano chitosan, 1% of bentonite, 1% of hydroxyethyl cellulose, 0.1% of an initiator (potassium persulfate), 2% of a cross-linking agent (ethylene glycol dimethacrylate), 0.1% of a surfactant (sodium dodecyl sulfate) and the balance of water. Wherein the average particle size of the nano chitosan is 150nm.
The preparation method is the same as in example 1.
Example 6
The preparation method comprises the following steps of:
5% of acrylamide, 1% of acrylic acid, 5% of nano chitosan, 0.8% of bentonite, 1% of hydroxyethyl cellulose, 0.1% of an initiator (potassium persulfate), 2% of a cross-linking agent (ethylene glycol dimethacrylate), 0.1% of a surfactant (sodium dodecyl sulfate) and the balance of water. Wherein the average particle size of the nano chitosan is 150nm.
The preparation method is the same as in example 1.
Example 7
The preparation method comprises the following steps of:
5% of acrylamide, 1% of acrylic acid, 5% of nano chitosan, 0.5% of bentonite, 1% of hydroxyethyl cellulose, 0.1% of an initiator (potassium persulfate), 2% of a cross-linking agent (ethylene glycol dimethacrylate), 0.1% of a surfactant (sodium dodecyl sulfate) and the balance of water. Wherein the average particle size of the nano chitosan is 150nm.
The preparation method is the same as in example 1.
Example 8
The preparation method comprises the following steps of:
5% of acrylamide, 1% of acrylic acid, 5% of nano chitosan, 0.5% of bentonite, 1% of hydroxyethyl cellulose, 0.1% of an initiator (potassium persulfate), 2% of a cross-linking agent (ethylene glycol dimethacrylate), 0.1% of a surfactant (sodium dodecyl sulfate), 1% of a reinforcing agent and the balance of water. Wherein the average particle size of the nano chitosan is 150nm.
The reinforcing agent is prepared by the following steps:
adding 10 parts by weight of citric acid into 20 parts by weight of ethanol water solution (volume fraction is 80%), stirring and dispersing uniformly, adding 5 parts by weight of chitosan, performing ultrasonic dispersion for 60min, adding 1 part by weight of calcium carbonate powder and 1 part by weight of porous silicon dioxide powder, performing ultrasonic dispersion for 30min, then dripping into 20 parts by weight of sodium hydroxide solution (5 wt%), standing for 20h, and filtering to obtain the reinforcing agent.
The blocking agent of this example was prepared as in the preparation of example 1.
Example 9
The difference from example 8 is that in this example, the mass fraction of the reinforcing agent is 1.5%.
Example 10
The difference from example 8 is that in this example, the mass fraction of the reinforcing agent is 2%.
Comparative example 1
The difference from example 1 is that, in this example, no nano chitosan, bentonite and hydroxyethyl cellulose were added, and the mass percentages of the respective raw materials are as follows.
5% Of acrylamide, 1% of acrylic acid, 0.1% of an initiator, 2% of a cross-linking agent, 0.1% of a surfactant and 91.8% of water.
Comparative example 2
The difference from example 1 is that, in this example, no nano chitosan and hydroxyethyl cellulose were added, and the mass percentages of the respective raw materials are as follows.
5% Of acrylamide, 1% of acrylic acid, 1% of bentonite, 0.1% of initiator, 2% of cross-linking agent, 0.1% of surfactant and 90.8% of water.
Comparative example 3
The difference from example 1 is that bentonite and hydroxyethyl cellulose are not added in this example, and the mass percentages of the respective raw materials are as follows.
5% Of acrylamide, 1% of acrylic acid, 1% of nano chitosan, 0.1% of initiator, 2% of cross-linking agent, 0.1% of surfactant and 90.8% of water.
Experimental example
1. Plugging agent viscosity test
The blocking agents of examples 1 to 3, examples 8 to 10 and comparative examples 1 to 3 were used as subjects, and the viscosity of the blocking agents was measured. The specific test method is as follows:
(1) The initial viscosity of the above-described blocking agent was tested using a brookfield dv-III rotary viscometer at room temperature;
(2) And placing the plugging agent into a constant-temperature oven at 90 ℃, counting the gel forming time after the reaction is finished, and testing the viscosity after the gel forming.
The test results are shown in Table 1.
TABLE 1 viscosity of the blocking agents
In table 1, the gel forming time was judged by visual inspection code standard, and when the gel reached class I, rigid gel, and the glass bottle was turned over, the gel surface was not deformed, namely, was regarded as gel forming. As can be seen from Table 1, the plugging agent provided by the embodiment of the invention has the initial viscosity of less than 10 mPa s at normal temperature, low viscosity, strong injectability, high viscosity of gel after gelling and good plugging effect. Compared with comparative examples 1-3, the initial viscosity of the nano chitosan and hydroxyethyl cellulose is high because the nano chitosan and hydroxyethyl cellulose contain a large amount of hydroxyl groups, have hydrophilicity, and can reduce the viscosity of the plugging agent system. In the gel three-dimensional network structure in the comparative example, the gel does not contain related molecular chains of chitosan and cellulose, the gel degree after gel formation is correspondingly reduced, and the blocking effect is poor.
In examples 8-10, a core-shell structured reinforcing agent was added, which after gelling, the reinforcing agent could be embedded or attached to the three-dimensional network structure, and the chitosan group could increase the viscosity of the gel and act as a thickening agent, thus the viscosity after gelling of examples 8-10 increased as compared to examples 1-3.
2. Gel strength test
Taking the blocking agents of examples 1-3, examples 8-10 and comparative examples 1-3 as experimental objects, respectively reacting the blocking agents in a constant temperature oven at 90 ℃,100 ℃ and 110 ℃ for 8 hours, measuring the viscoelasticity of gel after gel formation by using an MCR301 interface rheometer, wherein <1Pa is a weak gel, 1Pa-10Pa is a medium strength gel and >10Pa is a strong gel according to standard SY/T6296-2013. The results are shown in Table 2.
TABLE 2 post-gel strength of the blocking agents
As can be seen from Table 2, the strength of each blocking agent after gelling reached the strong gel grade, but the blocking agent provided in the examples had a higher strength after gelling than the comparative examples. The plugging agent of comparative example 1 contains no nano chitosan, bentonite and hydroxyethyl cellulose, the gel is mainly a polymer of acrylamide and acrylic acid reaction, the strength is low, the bentonite is added to the plugging agent of comparative example 2 based on comparative example 1, the bentonite can be used as a reinforcing agent and embedded into the network structure of the gel, the strength of the gel is further improved, and the strength of comparative example 2 is slightly higher than that of comparative example 1 from table 2.
In examples 8-10, the reinforcing agent is added on the basis of example 1, the surface of the reinforcing agent with a core-shell structure is citric acid carboxylated chitosan, and citric acid groups of the reinforcing agent can form chelate with bentonite, so that the bonding strength of the reinforcing agent and a gel network structure is improved, the overall emphasis of gel is improved, and the gel strength of examples 8-10 is higher than that of examples 1-3.
3. Simulated plugging experiments
The method comprises the steps of injecting acidic brine into an artificial microcrack sandstone core through a constant-pressure constant-speed pump, testing the permeability of the core after the injection rate is 1ml/min and the pressure is stable, selecting the artificial core with the permeability of 1-2mD as an experimental object, then injecting the plugging agent in the embodiment and the comparative example into the core, reacting for 8 hours in a constant-temperature oven at 90 ℃, injecting CO 2 for displacement experiment, and measuring the plugging efficiency, wherein the result is shown in table 3.
TABLE 3 blocking Properties of the blocking agents
As can be seen from table 3, the plugging agent provided in the examples can achieve a plugging efficiency of more than 90% in the simulated plugging experiment in the low-permeability core. The plugging agent provided by the comparative example has lower viscosity and strength after gelling, and the corresponding plugging efficiency is reduced to some extent, and the plugging effect is poor.
In summary, the plugging agent provided by the embodiment of the invention has the advantages that the addition, the crosslinking, the polymerization and the like of acrylamide and acrylic acid are performed to generate macromolecules, so that gel is formed to plug CO 2 gas channeling. In the process of polymerization reaction, nano chitosan can be adsorbed on the surface of a high molecular polymer, and the molecular chains of chitosan and ethyl cellulose contain hydroxyl groups, so that the hydroxyl groups can also participate in addition polymerization reaction to form a three-dimensional network structure, and the strength of gel is improved. Secondly, montmorillonite in bentonite can be added into the addition polymerization reaction of acrylamide and acrylic acid, combined with a polymerization main chain and embedded into a network structure, so that the stability and strength of gel are improved.
The surface groups of the reinforcing agent with the core-shell structure can form chelate compounds by metal ions in the three-dimensional network structure, and the calcium carbonate and the silicon dioxide in the reinforcing agent are reinforcing particles, and the inside and outside synergistic effect can obviously improve the gel strength. The surfactant can reduce the viscosity of the plugging agent system, thereby improving the injectability of the plugging agent, especially the injectability of the low-permeability layer. The plugging agent can be used in a CO 2 gas flooding well to prevent and control CO 2 gas channeling, and has high gel strength and high plugging efficiency after gel formation.
The embodiments described above are some, but not all embodiments of the invention. The detailed description of the embodiments of the invention is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Claims (5)
1. The plugging agent suitable for CO 2 gas channeling is characterized by comprising the following raw materials in percentage by mass:
5-10% of acrylamide, 1-5% of acrylic acid, 1-5% of nano chitosan, 0.5-1% of bentonite, 1-5% of hydroxyethyl cellulose, 0.1-0.5% of an initiator, 1-2% of a cross-linking agent, 0.1-0.5% of a surfactant, 1-2% of a reinforcing agent and the balance of water;
The reinforcing agent comprises, by weight, 10-20 parts of citric acid, 1-5 parts of calcium carbonate powder, 1-5 parts of porous silica, 5-10 parts of chitosan, 10-20 parts of ethanol aqueous solution and 10-20 parts of sodium hydroxide solution
Adding citric acid into an ethanol water solution, stirring and dispersing uniformly, adding chitosan, performing ultrasonic dispersion for 30-60min, adding calcium carbonate powder and porous silicon dioxide powder, performing ultrasonic dispersion for 30-60min, then dripping into a sodium hydroxide solution, standing for 10-20h, and filtering to obtain the reinforcing agent;
The preparation method of the plugging agent comprises the steps of adding the acrylamide, bentonite and the surfactant into water, performing ultrasonic dispersion for 20-30min, adding nano chitosan and acrylic acid, uniformly stirring, adding the rest raw materials, and uniformly stirring.
2. The plugging agent for CO 2 gas channeling according to claim 1, wherein the plugging agent comprises the following raw materials in mass percent:
5% of acrylamide, 1% of acrylic acid, 1% of nano chitosan, 0.5% of bentonite, 1% of hydroxyethyl cellulose, 0.1% of an initiator, 2% of a cross-linking agent, 0.1% of a surfactant, 1% of a reinforcing agent and the balance of water.
3. The plugging agent for CO 2 gas channeling of claim 1, wherein the surfactant is one or more of sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, sodium dodecyl sulfate, betaine.
4. The plugging agent for CO 2 gas channeling according to claim 1, wherein the crosslinking agent is one of ethylene glycol dimethacrylate and N, N-methylenebisacrylamide.
5. The plugging agent for CO 2 gas channeling of claim 1, wherein the nano chitosan has a particle size of 100-200nm.
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| CN106188403A (en) * | 2016-07-19 | 2016-12-07 | 西南石油大学 | Anti-CO2 gas channeling plugging agent for high-temperature and high-salt reservoirs and preparation method thereof |
| CN109468123A (en) * | 2017-09-07 | 2019-03-15 | 中国海洋石油集团有限公司 | A kind of drilling fluid environmental protection polymer micro Nano material and preparation method thereof |
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