An anti-gas channeling plugging composition and application thereof

Abstract

The application provides a gas channeling prevention plugging composition and application thereof, and the gas channeling prevention plugging composition comprises a first system and a second system; the first system comprises a crosslinking monomer, a crosslinking agent, a gelation control agent and an initiator; and the second system comprises sodium dodecyl sulfate and N, N, N', N'-tetramethyl-1, 3 propanediamine. The gas channeling prevention plugging composition provided by the application comprises two systems, and the two systems have complementary effects; when the gas channeling prevention plugging composition is used in carbon dioxide displacement exploitation, the plugging rate is high and the application range is wide.

Description

Technical Field

[0001] This invention belongs to the field of petroleum extraction technology, and particularly relates to a gas channeling prevention and sealing composition and its application. Background Technology

[0002] CO2 flooding is currently one of the important methods for increasing oil production in low-permeability oilfields. CO2, as a supercritical fluid, is non-toxic and chemically stable, exhibiting excellent solubility in crude oil and the ability to penetrate low-permeability areas to improve oil recovery. However, in field applications, due to factors such as the different mobility ratios between CO2 and crude oil and reservoir heterogeneity, gas channeling can easily occur during injection, leading to gas overflow in the produced well and reducing the sweep efficiency of CO2 on crude oil, thus decreasing the recovery rate. Natural fractures, artificial fractures, and relatively high-permeability layers in the reservoir are the main channels for gas channeling. Currently, a series of methods, including water-gas alternating injection, gel sealing, foam sealing, chemical precipitation, and CO2 thickening, are used to adjust the reservoir and address the gas channeling problem.

[0003] However, the water-gas alternating injection method is not suitable for reservoirs with strong heterogeneity. Frequent water-gas alternating injection increases the water saturation of the reservoir, reduces the contact efficiency between CO2 and crude oil, increases the relative viscosity of the crude oil, worsens its fluidity, and reduces the displacement efficiency. Furthermore, the unstable mobility ratio during water-gas alternating injection can corrode the equipment. The gel sealing method has limited injectability and cannot effectively seal deep reservoirs. The foam sealing method is difficult to maintain stability under different temperature and pH conditions, limiting its large-scale industrial development and application. The chemical precipitation method is not only difficult to determine the sealing location but also difficult to inject in low-permeability reservoirs. The CO2 thickening method is costly and difficult to prepare. Therefore, developing a carbon dioxide flooding method with high sealing efficiency and wide applicability is of great significance. Summary of the Invention

[0004] The main objective of this invention is to provide a gas channeling prevention and plugging composition that can be used in carbon dioxide flooding mining, with a high plugging rate and wide applicability.

[0005] The present invention also provides a method for carbon dioxide flooding mining, which uses the above-mentioned anti-gas channeling and plugging composition, thus achieving a high plugging rate and having a wide range of applications.

[0006] In a first aspect, the present invention provides an anti-gas channeling and sealing composition, comprising a first system and a second system;

[0007] The first system includes: crosslinking monomer, crosslinking agent, gelation control agent, and initiator;

[0008] The second system comprises sodium dodecyl sulfate and N,N,N',N'-tetramethyl-1,3-propanediamine.

[0009] In the gas channeling prevention and blocking composition described above, the molar ratio of sodium dodecyl sulfate and N,N,N',N'-tetramethyl-1,3-propanediamine is 1 to 3:1.

[0010] The gas channeling prevention and plugging composition as described above, wherein the first system comprises: 3-5% crosslinking monomer, crosslinking agent, 10-15% gelation control agent, 0.1-0.15% initiator, and the balance being deionized water.

[0011] In the gas channeling prevention and blocking composition described above, the crosslinking monomer is partially hydrolyzed polyacrylamide; the partially hydrolyzed polyacrylamide has a weight-average (or number-average / Z-average) molecular weight of 10 million to 30 million and a degree of hydrolysis of 5% to 50%.

[0012] The gas channeling prevention and plugging composition as described above, wherein the crosslinking agent comprises: 0.8–1% sodium dichromate, 1–2% thiourea, and 0.1–0.3% sodium thiosulfate; and / or,

[0013] The gelling control agent includes arginine.

[0014] The gas channeling prevention and sealing composition described above also includes a third system, which is a 3-5% persulfate solution.

[0015] In the gas channel blocking composition described above, the mass ratio of the first system to the third system is 1 to 5:1.

[0016] In the gas channel blocking composition described above, the mass ratio of the first system to the second system is 1 to 5:1.

[0017] Secondly, the present invention provides a method for carbon dioxide flooding mining, using the aforementioned gas channeling prevention and plugging composition.

[0018] The method described above, after extraction, also includes: introducing N2 into the reservoir, and introducing a 3-5% persulfate solution for gel breaking treatment.

[0019] The gas channeling prevention and plugging composition provided by the present invention comprises two systems with complementary effects. When used in carbon dioxide flooding mining, it has a high plugging rate and a wide range of applications. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0021] In a first aspect, the present invention provides an anti-gas channeling and sealing composition, comprising a first system and a second system;

[0022] The first system includes: crosslinking monomer, crosslinking agent, gelation control agent, and initiator;

[0023] The second system comprises sodium dodecyl sulfate and N,N,N',N'-tetramethyl-1,3-propanediamine.

[0024] It is understandable that CO2 channeling occurs primarily due to two factors: natural or artificial fractures in the reservoir, and areas with relatively high permeability within the reservoir. For plugging large pore throat fractures that facilitate CO2 channeling, a plugging agent with high gel strength and good stability should be selected. When plugging relatively high-permeability layers in the reservoir, the injection performance of the plugging agent should be emphasized, requiring good injectability and subsequent stable performance within the reservoir. Since the anti-channeling plugging composition is designed for CO2 flooding, it must maintain stable performance under acidic conditions.

[0025] The gas channeling prevention and plugging composition provided by this invention comprises two systems, namely a first system and a second system. The first system comprises: crosslinking monomers, a crosslinking agent, a gelation control agent, and an initiator. In the presence of the initiator, the crosslinking agent functions to crosslink the crosslinking monomers. During the process, the gelation control agent can control the crosslinking of the crosslinking monomers, thereby delaying gelation and facilitating injection into the reservoir. The resulting gel system is particularly suitable for plugging large-scale fractures, such as natural or artificial fractures with large pore throats.

[0026] The second system comprises sodium dodecyl sulfate (SDS) and N,N,N',N'-tetramethyl-1,3-propanediamine (TMPDA), a carbon dioxide-responsive system. Before contact with carbon dioxide, its solution viscosity is similar to that of water, exhibiting low viscosity, good fluidity, and good injection properties. Upon contact with carbon dioxide, the viscosity begins to increase, demonstrating a plugging effect, particularly suitable for plugging relatively high-permeability areas in reservoirs. The increase in viscosity after contact with carbon dioxide is presumably due to the presence of a protonable hydrophobic quaternary ammonium salt in TMPDA, which ionizes upon CO2 dissolution in water to produce H+. + Among them, hydrophobic quaternary ammonium salts and H + When the quaternary ammonium salt is protonated, it becomes hydrophilic. At this point, the TMPDA molecule is positively charged. Since the SDS molecule is negatively charged, two negatively charged SDS molecules and one positively charged TMPDA molecule form a molecular "bridge" to form worm-like micelles with high viscosity, thereby increasing the viscosity of the system.

[0027] The gas channeling prevention and plugging composition provided by this invention comprises two systems. The first system is a high-strength plugging system that is resistant to temperature and salt, and its colloid has high rigidity, toughness and stability, and has a good plugging effect, especially on fractured CO2 gas channeling channels. The second system has good fluidity and has a good plugging effect, especially on relatively high-permeability layers in reservoirs, when CO2 is introduced. Therefore, the two systems have complementary effects and can be used in carbon dioxide flooding exploitation with a high plugging rate and wide applicability.

[0028] In some embodiments of the present invention, the molar ratio of sodium dodecyl sulfate and N,N,N',N'-tetramethyl-1,3-propanediamine is 1 to 3:1.

[0029] In this invention, the molar ratio of sodium dodecyl sulfate (SDS) and N,N,N',N'-tetramethyl-1,3-propanediamine (TMPDA) in the second system, namely the carbon dioxide responsive system, is controlled to be 1 to 3:1. This satisfies the requirement for SDS molecules and TMPDA to form worm-like micelles with high viscosity through molecular "bridging", thereby increasing the viscosity of the system and further achieving a higher carbon dioxide blocking rate in the reservoir, especially in high-permeability areas.

[0030] In some embodiments of the present invention, the first system comprises: 3-5% crosslinking monomer, crosslinking agent, 10-15% gelation control agent, 0.1-0.15% initiator, and the balance being deionized water.

[0031] The first system in this invention comprises: 3-5% crosslinking monomer, crosslinking agent, 10-15% gelation control agent, 0.1-0.15% initiator, and the balance being deionized water. The content of each component is within a suitable range, which allows the first system to be used as a plugging agent, especially for plugging gas channeling channels in cracks with large pore throats. It has a long gelation time, high stability, good injection performance, and high economic benefits.

[0032] In some embodiments of the present invention, the crosslinking monomer is partially hydrolyzed polyacrylamide; the partially hydrolyzed polyacrylamide has a weight-average (or number-average / Z-average) molecular weight of 10 million to 30 million and a degree of hydrolysis of 5% to 50%.

[0033] In this invention, the crosslinking monomer of the first system is partially hydrolyzed polyacrylamide (HPAM), and the weight-average (or number-average / Z-average) molecular weight of the partially hydrolyzed polyacrylamide is 10 million to 30 million, and the degree of hydrolysis is 5% to 50% (molar percentage). Within a suitable range, the partially hydrolyzed polyacrylamide undergoes a crosslinking reaction with the crosslinking agent through its amide groups, thereby forming a polymer gel system. The appropriate weight-average molecular weight and degree of hydrolysis can adjust the viscosity of the first system within a suitable range.

[0034] The present invention limits the weight-average molecular weight and degree of hydrolysis of the crosslinked monomer partially hydrolyzed polyacrylamide in the first system, which can further improve the blocking effect on CO2 gas channeling channels in the reservoir, especially fracture-type CO2 gas channeling channels.

[0035] In some embodiments of the present invention, the crosslinking agent comprises: 0.8–1% sodium dichromate, 1–2% thiourea, and 0.1–0.3% sodium thiosulfate; and / or,

[0036] The gelling control agent includes arginine.

[0037] The crosslinking agent in the first system of this invention comprises: 0.8–1% sodium dichromate, 1–2% thiourea, and 0.1–0.3% sodium thiosulfate, within a suitable range, Cr 3+ It reacts with carboxylic acids to form a polymer gel system, but the chromium in sodium dichromate is in the +6 oxidation state. Prior to this, Cr... 6+ It needs to be reduced to Cr 3+ Compared to salts of trivalent chromium ions, sodium dichromate is relatively inexpensive. Both thiourea and sodium thiosulfate are reducing agents; however, thiourea alone has poor reducing properties, while sodium thiosulfate is inconvenient to purchase and expensive. Using thiourea and sodium thiosulfate in a certain ratio results in better reduction and is more economical.

[0038] This invention adds arginine as a gelation control agent, which can delay the gelation of crosslinking agents. In a redox reaction environment, arginine has an effect on Cr 3+ It has chelating ability and can slow down Cr 3+ The time required for the reaction with carboxylic acids to form a polymer. This system can delay gelation, and the gelled colloid remains stable for 30 days without aging.

[0039] In some embodiments of the present invention, a third system is also included, wherein the third system is a 3-5% persulfate solution.

[0040] In this invention, the third system of the anti-gas channeling blocking composition is a 3-5% persulfate solution, for example, a 3-5% sodium persulfate solution. After the first and second systems in the blocking composition have achieved blocking of carbon dioxide gas, the 3-5% persulfate solution is added, which can react with the Cr in the first system. 3+ The reaction disrupts the gel structure, thus enabling the gel-breaking process of the first system.

[0041] In this invention, the third system is a 3-5% persulfate solution, which can break down the first system and prevent it from remaining in the reservoir after injection, thus avoiding formation pollution.

[0042] In some embodiments of the present invention, the mass ratio of the first system to the third system is 1 to 5:1.

[0043] In this invention, the mass ratio of the first system to the third system in the anti-gas channeling blocking composition is controlled to be 1–5:1. Within a suitable range, the third system, i.e., a 3–5% persulfate solution, can be injected into the reservoir to achieve the effect of controlling the first system, i.e., HPAM / Cr. 3+ The system's gel breaking process is more thorough, and it can also avoid the addition of excessive amounts of 3-5% persulfate solution, which may remain in the formation and cause contamination.

[0044] In some embodiments of the present invention, the mass ratio of the first system to the second system is 1 to 5:1.

[0045] In this invention, the mass ratio of the first system to the second system in the anti-gas channeling blocking composition is controlled to be 1 to 5:1. Within a suitable range, the blocking effect on carbon dioxide gas can be further improved, and the complementary effect of the two is more obvious, which can further improve the blocking rate.

[0046] Secondly, the present invention provides a method for carbon dioxide flooding mining, using the aforementioned gas channeling prevention and plugging composition.

[0047] In the carbon dioxide flooding extraction method of the present invention, the above-mentioned anti-gas channeling blocking composition is used to block carbon dioxide, which has a high blocking rate and a wide range of applications.

[0048] In some embodiments of the present invention, the process after extraction further includes: introducing N2 into the reservoir, and / or introducing a 3-5% persulfate solution for gel breaking treatment.

[0049] After mining is completed, this invention introduces N2 into the reservoir to break down the second system, namely the carbon dioxide-responsive system. After N2 removes CO2 from the solution, the quaternary ammonium salt is deprotonated to a tertiary amine, forming spherical micelles with low initial viscosity. Moreover, this transformation from spherical to worm-like micelles is reversible and can be repeated multiple times. Introducing a 3-5% persulfate solution into the reservoir is to break down the first system, namely HPAM / Cr... 3+ The system undergoes a gel breaking process.

[0050] The carbon dioxide flooding extraction method of this invention provides a reversible plugging effect, avoiding the situation where plugging agents used in existing technologies remain in the reservoir after injection, causing formation pollution. The HPAM / Cr in this invention... 3+ Adding 3% persulfate solution to the system as a breaker resulted in good breaker performance. The worm-like micelles formed after the carbon dioxide-responsive system reacted with CO2 expelled CO2 from the system after N2 was introduced, reducing the system viscosity. The system could be discharged from the formation like an aqueous solution, allowing it to be returned to the surface after operation, thus achieving harmless operation to the formation.

[0051] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0052] Example 1

[0053] The carbon dioxide flooding extraction method of this embodiment includes the following steps:

[0054] 1) Take 100mL of beaker and add pure water. Add 3% partially hydrolyzed polyacrylamide (HPAM) crystals and stir until completely dissolved. The degree of hydrolysis of partially hydrolyzed polyacrylamide is 25%, and the weight average molecular weight is 10 million. Then add crosslinking agent (containing 0.8% sodium dichromate, 1% thiourea, and 0.1% sodium thiosulfate) until completely dissolved. Add 15% amino acid as a gelation control agent and continue stirring until evenly dispersed. Purge nitrogen gas into the above solution for 30 minutes. Add 0.1% ammonium thiosulfate as an initiator and continue purging nitrogen gas for 5 minutes to obtain the first system.

[0055] 2) Add SDS, TMPDA and water to a beaker, wherein the molar ratio of SDS to TMPDA is 2:1, denoted as ratio 1. Stir and dissolve at 55°C for 6 minutes. Seal the solution system and let it stand at 25°C for half an hour to stabilize. Remove the foam in the system to obtain the second system.

[0056] 3) Take out one high-permeability core and one low-permeability core, and artificially create fractures in the high-permeability core, recording its weight. Then, vacuum-pump the core to saturate it with water, recording the wet weight to calculate the core's pore volume. Next, push water at a rate of 0.5 mL / min until the pressure stabilizes, recording the pressure and calculating the core's permeability. Then, inject simulated formation oil at the same rate until the core is saturated to its maximum oil saturation, recording the saturated oil volume to calculate the bound water volume.

[0057] 4) In a high-temperature oven at 70℃, a core holder with two parallel tubes was used to displace CO2 at a rate of 1.0 mL / min until CO2 was observed to escape from the outlet. The first and second systems were injected at a rate of 1.0 mL / min. The mass ratio of the first and second systems was 3:1, which was recorded as ratio 2. After stopping the injection, the system was sealed and allowed to stand for 20 hours.

[0058] 5) After releasing the injection pressure at the inlet, proceed with subsequent CO2 gas drive at a rate of 1.0 mL / min until CO2 is observed to escape from the outlet. Calculate the plugging rate and recovery rate.

[0059] Example 2-19

[0060] The methods for carbon dioxide flooding extraction in Examples 2-19 are basically the same as those in Example 1, except that one or more steps of the extraction method are changed. Specific results are shown in Tables 1-2.

[0061] Example 20

[0062] The method of carbon dioxide flooding extraction in Example 20 is basically the same as that in Example 1, except that step 6) is added: N2 is introduced at a rate of 1.0 mL / min and 3% sodium persulfate solution is introduced at a rate of 1.0 mL / min, wherein the mass ratio of the first system to the 3% sodium persulfate solution is 3:1, in order to perform gel breaking treatment.

[0063] Examples 21-22

[0064] The methods for carbon dioxide flooding extraction in Examples 21-22 are basically the same as those in Example 20, except that the concentration of the sodium persulfate solution is changed. Specific results are shown in Tables 1-2.

[0065] Comparative Example 1

[0066] The method used in this comparative example is basically the same as that in Example 1 for carbon dioxide flooding, except that only the first system is injected in step 4). The specific results are shown in Tables 1-2.

[0067] Comparative Example 2

[0068] This comparative example uses a method essentially the same as that of carbon dioxide flooding extraction in Example 1, except that only the second system is injected in step 4). Specific results are shown in Tables 1-2.

[0069] Comparative Example 3

[0070] The comparative example is basically the same as the carbon dioxide flooding extraction method in Example 1, except that the second system in step 4) includes a small molecule amine compound (DMTA) and an anionic surfactant (NADS). Specific results are shown in Tables 1-2.

[0071] Comparative Example 4

[0072] The method used in this comparative example is basically the same as that used in Example 1 for carbon dioxide flooding, except that a gel-type foam plugging agent (mainly composed of polyacrylamide, chromium acetate, sodium dodecylbenzenesulfonate, etc.) is injected in step 4). Specific results are shown in Tables 1-2.

[0073] Experimental example:

[0074] 1. The formula for calculating the core plugging rate is: Plugging rate (%) = (permeability before plugging - permeability after plugging) / permeability before plugging * 100%;

[0075] The formula for calculating core permeability is:

[0076] Kg: Core permeability, μm;

[0077] Q0: Gas volumetric flow rate at the core outlet, mL / s;

[0078] Pa: Atmospheric pressure (absolute), MPa;

[0079] L: Core length, cm;

[0080] μ: Liquid viscosity of carbon dioxide at experimental temperature and atmospheric pressure, MPa;

[0081] A: Cross-sectional area of ​​the core, in cm² 2 ;

[0082] P1: Absolute pressure at the core inlet, MPa;

[0083] P2: Absolute pressure at the core outlet, MPa.

[0084] 2. Method for testing the gelation time and gel strength of the first system: Place the prepared first system in a 60℃ oven. During the constant temperature process in the oven, take it out every 5 days to observe whether gelation has occurred and test the viscosity. The time when the viscosity is greater than E is the gelation time, and the gel strength is I.

[0085] Ten days later, the gel viscosity was rapidly measured at 70°C.

[0086] The results of the gel strength are shown in the table below:

[0087] Time / day 10 15 30 40 50 60 rubber strength G I I I I I

[0088] 3. Method for testing the gelation time and gel strength of the second system: Transfer the prepared second system to a beaker, introduce CO2 gas at a flow rate of 50 mL / min for 2 min, and stir the solution to ensure thorough mixing of gas and solution to form a CO2-responsive gel system. Then place it in a constant temperature environment of 80℃ for 3 days. Observe the gelation time and gel strength.

[0089] The viscosity of the second system before CO2 introduction was tested using a rheometer. At 80°C, the viscosity of this system was 25.6 mPa·s. The viscosity of the gel system formed after CO2 introduction was 3268 mPa·s.

[0090] Table 1

[0091]

[0092]

[0093] Table 2

[0094]

[0095]

[0096] As shown in Tables 1-2, compared with the comparative examples, the anti-gas channeling plugging composition provided by the present invention comprises two systems. The first system is a high-strength plugging system that is resistant to temperature and salt, and its colloid has high rigidity, toughness and stability, and has a good plugging effect, especially on fractured CO2 gas channeling channels. The second system has good fluidity, and when CO2 is introduced, it has a good plugging effect, especially on relatively high-permeability layers in the reservoir. Therefore, the two systems have complementary effects, and when used in carbon dioxide flooding, the plugging rate is high and the applicability is wide.

[0097] As can be seen from the comparison between Example 1 and Comparative Examples 1-4, the carbon dioxide flooding extraction method provided by the present invention has a higher plugging rate and a significantly improved recovery rate.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A gas channeling prevention and sealing composition, characterized in that, Including the first system, the second system, and the third system; The first system comprises: 3-5% partially hydrolyzed polyacrylamide as a crosslinking monomer, a crosslinking agent, 10-15% a gelation control agent, 0.1-0.15% an initiator, and the balance being deionized water; the crosslinking agent comprises: 0.8-1% sodium dichromate, 1-2% thiourea, and 0.1-0.3% sodium thiosulfate; the partially hydrolyzed polyacrylamide has a molecular weight of 10-30 million and a degree of hydrolysis of 5-50%; the first system is a gel system formed in the presence of the initiator, where the crosslinking agent acts to crosslink the crosslinking monomers, and the gelation control agent controls the crosslinking of the crosslinking monomers to delay gelation; the first system is used to seal large-scale cracks; The second system comprises sodium dodecyl sulfate and N,N,N',N'-tetramethyl-1,3propanediamine; the molar ratio of sodium dodecyl sulfate to N,N,N',N'-tetramethyl-1,3propanediamine is 1 to 3:

1. The second system is a carbon dioxide-responsive system. Before contact with carbon dioxide, its solution viscosity is similar to that of water, with a relatively low viscosity. After contact with carbon dioxide, N,N,N',N'-tetramethyl-1,3-propanediamine contains a hydrophobic quaternary ammonium salt that can be protonated. This ionizes upon CO2 dissolving in water to produce H₂. + Among them, hydrophobic quaternary ammonium salts and H + When combined with protonation, the quaternary ammonium salt becomes hydrophilic. At this point, the N,N,N',N'-tetramethyl-1,3-propanediamine molecule carries a positive charge. Since the sodium dodecyl sulfate molecule carries a negative charge, two negatively charged sodium dodecyl sulfate molecules and one positively charged N,N,N',N'-tetramethyl-1,3-propanediamine molecule undergo molecular "bridging" to form worm-like micelles with high viscosity, increasing the viscosity of the system. This is used to plug areas with relatively high permeability in reservoirs. The mass ratio of the first system to the second system is 1 to 5:1; The third system is a 3-5% persulfate solution; the mass ratio of the first system to the third system is 1-5:

1.

2. The gas channeling prevention and sealing composition according to claim 1, characterized in that, The gelling control agent includes arginine.

3. A method for carbon dioxide flooding extraction, characterized in that, Use the gas channel blocking composition according to any one of claims 1-2.

4. The method according to claim 3, characterized in that, Post-mining procedures also include: introducing N2 into the reservoir, and / or introducing a 3-5% persulfate solution for gel breaking treatment.

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