A gel profile control agent for oilfield waterflooding

Abstract

The present application relates to a kind of gel profile control agent for oilfield water flooding oil layer channeling, belong to petroleum engineering technical field.The gel profile control agent of the present application is mainly made of partially hydrolyzed polyacrylamide, organic chromium crosslinking agent, reinforcing agent, glue accelerator and water;The mass ratio of partially hydrolyzed polyacrylamide, chromium salt crosslinking agent, reinforcing agent and glue accelerator is 0.4-0.6:0.3-0.5:2-4:0.3-0.4;Reinforcing agent is sodium bentonite and modified starch, and the mass ratio of sodium bentonite and modified starch is 1-2:1-2;Glue accelerator is resorcinol, urotropine and organic acid, and the mass ratio of resorcinol, urotropine and organic acid is 0.9-1.2:0.9-1.2:0.8-1.3.The gel profile control agent is applied to the gel profile control agent for oilfield water flooding oil layer channeling, can effectively improve the sealing strength, and can selectively enter channeling channel, and low permeability layer is little polluted.

Description

TECHNICAL FIELD

[0001] The present application relates to a gel profile control agent for blocking channeling in water flooding oil reservoirs, and belongs to the technical field of petroleum engineering. BACKGROUND

[0002] In the process of water flooding oil reservoirs, due to the heterogeneity of the formation and the oil reservoir, the injected water "breaks through" along the high permeability direction in the oil reservoir. With the increase of the injection time and the injection volume, the unevenness of the injection profile increases, forming a "channeling" channel, which leads to a large amount of water production in some direction of the oil well. In order to improve the oil displacement effect and increase the recovery rate, it is necessary to use a profile control agent to block the channeling channel. In order to reduce the pollution of the blocking channeling profile control to the medium and low permeability layer and achieve large-dose deep profile control, the profile control agent is required to have high sealing strength and strong selectivity to enter the channeling channel.

[0003] Gel is a solid or semi-solid colloidal system, which has a space network structure mainly based on intramolecular crosslinking of colloidal particles and high molecules, and auxiliary intermolecular crosslinking. The structure gap is full of liquid, which is fixed and cannot move, so that the system loses fluidity. Its properties are between solid and liquid, and the strength is enough to prevent water flow through the formation. The gel profile control agent is often used for blocking channeling in water flooding oil reservoirs due to its colloidal properties and thermodynamic stability.

[0004] The existing gel profile control agent for blocking channeling in water flooding oil reservoirs can be divided into underground polymerization gel profile control agent and underground crosslinking gel profile control agent according to the gelation reaction property. Among them, the commonly used underground polymerization gel profile control agent has the following formula (mass %): AM 4%~5%, modified starch 4%~5%, initiator 0.01~0.05%, water 90%~92%, and high sealing strength meets the requirements of high pore and high permeability profile control. The shortcomings are that the AM single agent concentration is high, the dosage is large, the single formula cost of the profile control agent is high, and due to the limitation of gelation time, it is difficult to achieve large-dose deep profile control. The profile control design dosage is not matched with the volume of the channeling channel, the sealing effective period is short, and new water channeling channels are easily formed around the sealing section. Compared with the underground polymerization gel profile control agent, the underground crosslinking gel profile control agent has low cost and can achieve large-dose deep profile control, but due to the low crosslinking strength of the gel agent, the sealing strength of the channeling channel is weak, and degradation phenomenon occurs in the formation for a long time, so the sealing effective period is short. For example, the commonly used underground crosslinking gel profile control agent has the following formula (mass %): partially hydrolyzed polyacrylamide (HPAM, molecular weight 1200 million, hydrolysis degree 20%) 0.4%~0.6%, crosslinking agent (chromium lactate) 0.4%~0.6%, water 98.8%~99.2%, and the sealing strength in the laboratory is less than 0.02 MPa / cm. SUMMARY

[0005] The gel profile control agent for blocking channeling of oil layer driven by water in oil field has higher blocking strength.

[0006] In order to achieve the above object, the technical scheme adopted by the present application is:

[0007] The gel profile control agent for blocking channeling of oil layer driven by water in oil field is mainly made of partially hydrolyzed polyacrylamide, organic chromium crosslinking agent, reinforcing agent, gelation accelerator and water; the mass ratio of the partially hydrolyzed polyacrylamide, chromium salt crosslinking agent, reinforcing agent and gelation accelerator is 0.4-0.6:0.3-0.5:2-4:0.3-0.4; the reinforcing agent is sodium-based bentonite and modified starch, and the mass ratio of the sodium-based bentonite and modified starch is 1-2:1-2; the gelation accelerator is resorcinol, urotropin and organic acid, and the mass ratio of the resorcinol, urotropin and organic acid is 0.9-1.2:0.9-1.2:0.8-1.3.

[0008] When the gel profile control agent is applied to blocking channeling of oil layer driven by water in oil field, the hydrophilic groups of the partially hydrolyzed polyacrylamide and the hydroxyl groups on the surface of the sodium-based bentonite and modified starch particles are bridged by hydrogen bonds when the sodium-based bentonite and modified starch particles meet the partially hydrolyzed polyacrylamide in water, forming flocculation bodies, which can effectively improve the blocking strength of the gel system, and the indoor experiment shows that the blocking strength is greater than 0.17 MPa / cm after the gelation, and the long-chain macromolecules of the polyacrylamide can selectively enter the channeling channel due to the pulling effect, which can cause little pollution to the medium and low permeability layer, and the gel profile control agent is suitable for large-dose deep profile control.

[0009] The gel profile control agent is a composite gel body mainly made of polyacrylamide-phenolic resin, and the urotropin (hexamethylene tetramine (CH2)6N4) in the raw material can slowly release formaldehyde (the chemical reaction is (CH2)6N4+6H2O----4NH3+6HCHO) in the acid medium under heat, so the crosslinking time of the system can be prolonged, which is beneficial to large-dose treatment, and the resorcinol in the raw material can also introduce aromatic rings into the network structure of the gel profile control agent, improving the thermal stability of the gel profile control agent, so that the profile control agent can adapt to the sandstone oil reservoir with a formation temperature of 30-80℃.

[0010] Further, the mass ratio of the partially hydrolyzed polyacrylamide, chromium salt crosslinking agent, reinforcing agent and gelation accelerator is 0.4-0.6:0.3-0.5:3:0.3. The mass ratio of the sodium-based bentonite and modified starch is 1:2. The mass ratio of the resorcinol, urotropin and organic acid is 1:1:1.

[0011] Partially hydrolyzed polyacrylamide (HPAM) is also known as anionic polyacrylamide, which has good thermal stability and chemical stability. Since the molecule chain of the partially hydrolyzed polyacrylamide contains active amide group -CONH2 and carboxyl group -COOH, the partially hydrolyzed polyacrylamide can form a bridge with sodium bentonite and hydroxyl group on the surface of modified starch particles through hydrogen bond to form a flocculation body, which can enhance the mechanical strength of the gel and improve the shear resistance of the gel, thereby improving the plugging strength of the gel profile control agent. Further, the partially hydrolyzed polyacrylamide has a molecular weight of 8-12 million and a hydrolysis degree of 20-25%, for example, a hydrolysis degree of 25%.

[0012] Further, the organic chromium crosslinking agent is chromium acetate and / or chromium lactate. The organic chromium crosslinking agent is preferably chromium lactate. Compared with chromium acetate, chromium lactate releases Cr 3+ at a slower speed in the gel forming process, and can better adjust the gel forming time.

[0013] Further, the mass ratio of the partially hydrolyzed polyacrylamide to water is 0.4-0.6:98.3-98.7. Using a lower concentration of partially hydrolyzed polyacrylamide can reduce the profile control cost, ensure the effect and benefit of large-dose deep profile control, and solve the problems of high cost of existing underground polymer gel profile control agent and weak strength of underground crosslinking gel profile control agent, and the effect and benefit of the profile control are not ideal.

[0014] Further, the preparation method of the gel profile control agent comprises the following steps: mixing water and an organic chromium crosslinking agent to obtain a crosslinking agent solution; mixing a mixture of partially hydrolyzed polyacrylamide, a reinforcing agent and a gelation accelerator with the crosslinking agent solution, and the gel profile control agent is obtained.

[0015] The smaller the particle size of sodium bentonite and modified starch is, the more conducive it is to the combination of the polar groups on the surface of the sodium bentonite and the modified starch with the partially hydrolyzed polyacrylamide, which ensures the uniformity and strength of the gel system. Further, the particle size of the sodium bentonite and the modified starch is 150 mesh (including 150 mesh) or more, for example, 150 mesh, 200 mesh or 300 mesh.

[0016] Further, the modified starch is pre-gelatinized starch, for example, pre-gelatinized corn starch.

[0017] Further, the organic acid is citric acid. The citric acid in the gelation accelerator can adjust the pH value of the reaction environment of urotropine, thereby controlling the reaction speed of urotropine, and can effectively adjust the gel forming time and strength of the gel profile control agent.

[0018] The gel profile control agent for oilfield water flooding oil layer channeling of the present application is prepared on site when used, and then continuously injected into the profile control well by using an injection pump. DETAILED DESCRIPTION

[0019] The technical scheme of the present application is further described below in combination with the specific embodiments.

[0020] The modified starch used in the following embodiments is specifically pregelatinized corn starch, specifically pregelatinized corn starch produced by Ningjin County Jiahe Energy-saving Material Co., Ltd., with a purity of 99.9% and a particle size of 150 mesh. The pregelatinized corn starch can swell in cold water (0-4℃).

[0021] Embodiment 1

[0022] The gel profile control agent for blocking channeling of oil reservoirs driven by water in oil fields of this embodiment is made from the following raw materials in parts by weight: partially hydrolyzed polyacrylamide 0.4 parts, organic chromium crosslinking agent 0.3 parts, reinforcing agent 3 parts, gelation accelerator 0.3 parts, and water 98.7 parts. The partially hydrolyzed polyacrylamide (HPAM) used has a relative molecular weight of 12 million and a hydrolysis degree of 25%. The organic chromium crosslinking agent used is chromium lactate. The reinforcing agent used is a uniform mixture of sodium-based bentonite and modified starch, and the particle size of the sodium-based bentonite and the modified starch is 150 mesh. The mass ratio of sodium-based bentonite to modified starch in the mixture is 1:2. The gelation accelerator used is a uniform mixture of resorcinol, urotropine, and citric acid, and the mass ratio of resorcinol, urotropine, and citric acid in the mixture is 1:1:1.

[0023] The preparation method of the gel profile control agent for blocking channeling of oil reservoirs driven by water in oil fields of this embodiment includes the following steps:

[0024] 1) Add the organic chromium crosslinking agent to water to prepare a uniform crosslinking agent aqueous solution;

[0025] 2) Add the partially hydrolyzed polyacrylamide, reinforcing agent, and gelation accelerator to a mixer, mix uniformly, and obtain a mixture;

[0026] 3) Pour the crosslinking agent aqueous solution prepared in step 1) and the mixture prepared in step 2) into a stirring tank together using a jet pump, and stir for 40 minutes to obtain the gel profile control agent.

[0027] The gel profile control agent of Embodiment 1 is suitable for plugging the channeling channels of sandstone oil reservoirs at 30℃-80℃, and the plugging strength is 0.18 MPa / cm. The current cost of the gel profile control agent is 353 yuan / square meter.

[0028] Embodiment 2

[0029] The gel profile control agent for blocking channeling of oil reservoirs driven by water in oil fields of the embodiment is made from the following raw materials in parts by weight: partially hydrolyzed polyacrylamide 0.5 parts, organic chromium crosslinking agent 0.3 parts, reinforcing agent 3 parts, gelation accelerator 0.3 parts, and water 98.6 parts; the partially hydrolyzed polyacrylamide (HPAM) used has a relative molecular weight of 12 million and a degree of hydrolysis of 25%; the organic chromium crosslinking agent used is chromium lactate; the reinforcing agent used is a uniform mixture of sodium bentonite and modified starch, the particle size of the sodium bentonite and the modified starch is 150 mesh, and the mass ratio of the sodium bentonite to the modified starch in the mixture is 1:2; and the gelation accelerator used is a uniform mixture of resorcinol, urotropine, and citric acid, and the mass ratio of resorcinol, urotropine, and citric acid in the mixture is 1:1:1.

[0030] The preparation method of the gel profile control agent for blocking channeling of oil reservoirs driven by water in oil fields of the embodiment includes the following steps:

[0031] 1) Add the organic chromium crosslinking agent into water to prepare a uniform crosslinking agent aqueous solution;

[0032] 2) Add the partially hydrolyzed polyacrylamide, the reinforcing agent, and the gelation accelerator into a mixer, mix uniformly to obtain a mixture;

[0033] 3) Pour the crosslinking agent aqueous solution prepared in step 1) and the mixture prepared in step 2) into a stirring tank together using a jet pump, and stir for 40 minutes to obtain the gel profile control agent.

[0034] The gel profile control agent of Example 2 is suitable for plugging the channeling flow channels of sandstone oil reservoirs at 30℃ to 80℃, and the plugging strength is 0.20 MPa / cm. The current cost of the gel profile control agent is 369 yuan / square meter.

[0035] Example 3

[0036] The gel profile control agent for blocking channeling of oil reservoirs driven by water in oil fields of the embodiment is made from the following raw materials in parts by weight: partially hydrolyzed polyacrylamide 0.5 parts, organic chromium crosslinking agent 0.3 parts, reinforcing agent 3 parts, gelation accelerator 0.3 parts, and water 98.6 parts; the partially hydrolyzed polyacrylamide (HPAM) used has a relative molecular weight of 12 million and a degree of hydrolysis of 25%; the organic chromium crosslinking agent used is chromium lactate; the reinforcing agent used is a uniform mixture of sodium bentonite and modified starch, the particle size of the sodium bentonite and the modified starch is 150 mesh, and the mass ratio of the sodium bentonite to the modified starch in the mixture is 1:2; and the gelation accelerator used is a uniform mixture of resorcinol, urotropine, and citric acid, and the mass ratio of resorcinol, urotropine, and citric acid in the mixture is 1:1:1.

[0037] The preparation method of the gel profile control agent for blocking channeling of oil reservoirs driven by water in oil fields of the embodiment includes the following steps:

[0038] 1) adding organic chromium crosslinking agent into water, preparing uniform crosslinking agent aqueous solution;

[0039] 2) adding partially hydrolyzed polyacrylamide, reinforcing agent and glue promoter into a mixer, mixing uniformly to obtain mixture;

[0040] 3) adding the crosslinking agent aqueous solution prepared in step 1) and the mixture prepared in step 2) into a stirring tank by jet pump, stirring for 40 minutes to obtain gel profile control agent.

[0041] The gel profile control agent of example 3 is suitable for plugging the channeling flow passage of sandstone reservoir at 30℃-80℃, the plugging strength is 0.23 MPa / cm, and the current cost of the gel profile control agent is 393 yuan / square meter.

[0042] Example 4

[0043] The gel profile control agent for plugging channeling flow passage of oil reservoir by water flooding in this example is made of the following raw materials in weight fraction: partially hydrolyzed polyacrylamide 0.6 parts, organic chromium crosslinking agent 0.5 parts, reinforcing agent 2 parts, glue promoter 0.4 parts, water 98.3 parts; the relative molecular weight of the partially hydrolyzed polyacrylamide (HPAM) used is 8 million, and the degree of hydrolysis is 20%; the organic chromium crosslinking agent used is chromium acetate; the reinforcing agent used is a uniform mixture of sodium-based bentonite and modified starch, the particle size of sodium-based bentonite and modified starch is 150 mesh, and the mass ratio of sodium-based bentonite to modified starch in the mixture is 1:1; the glue promoter used is a uniform mixture of resorcinol, urotropine and citric acid, and the mass ratio of resorcinol, urotropine and citric acid in the mixture is 0.9:1.2:0.8.

[0044] The preparation method of the gel profile control agent for plugging channeling flow passage of oil reservoir by water flooding in this example is the same as that of example 3, which will not be described here. The gel profile control agent of example 4 is suitable for plugging the channeling flow passage of sandstone reservoir at 30℃-80℃, and the plugging strength is 0.19 MPa / cm.

[0045] Example 5

[0046] The gel profile control agent for blocking channeling of oil reservoirs driven by water in oil fields of the present example is made from the following raw materials in parts by weight: partially hydrolyzed polyacrylamide 0.6 parts, organic chromium crosslinking agent 0.5 parts, reinforcing agent 4 parts, gelation accelerator 0.3 parts, and water 98.3 parts; the partially hydrolyzed polyacrylamide (HPAM) used has a relative molecular weight of 12 million and a degree of hydrolysis of 25%; the organic chromium crosslinking agent used is chromium lactate; the reinforcing agent used is a uniform mixture of sodium bentonite and modified starch, the particle size of the sodium bentonite and the modified starch is 150 mesh, and the mass ratio of the sodium bentonite to the modified starch in the mixture is 2:1; the gelation accelerator used is a uniform mixture of resorcinol, urotropine, and citric acid, and the mass ratio of resorcinol, urotropine, and citric acid in the mixture is 1.2:0.9:1.3.

[0047] The preparation method of the gel profile control agent for blocking channeling of oil reservoirs driven by water in oil fields of the present example is the same as that of Example 3, which will not be described here again. The gel profile control agent of Example 5 is suitable for blocking the channeling of sandstone oil reservoirs at 30-80°C, and the blocking strength is 0.28 MPa / cm.

[0048] Comparative Example 1

[0049] The gel profile control agent of the present comparative example differs from that of Example 1 only in that the weight fraction of the reinforcing agent is adjusted to 2 parts. The blocking strength of the gel profile control agent of the present comparative example is 0.11 MPa / cm.

[0050] Comparative Example 2

[0051] The gel profile control agent of the present comparative example differs from that of Example 1 only in that the weight fraction of the reinforcing agent is adjusted to 1 part. The blocking strength of the gel profile control agent of the present comparative example is 0.08 MPa / cm.

[0052] Comparative Example 3

[0053] The gel profile control agent of the present comparative example differs from that of Example 1 only in that the mass ratio of sodium bentonite to modified starch in the reinforcing agent is adjusted to 2:1. The blocking strength of the gel profile control agent of the present comparative example is 0.12 MPa / cm.

[0054] Comparative Example 4

[0055] The gel profile control agent of the present comparative example differs from that of Example 1 only in that the sodium bentonite in the reinforcing agent is replaced by calcium bentonite. The blocking strength of the gel profile control agent of the present comparative example is 0.08 MPa / cm.

[0056] Comparative Example 5

[0057] The gel profile control agent of the present comparative example differs from the gel profile control agent of Example 3 only in that the present comparative example adjusts the weight fraction of the gelation accelerator to 2 parts. The shut-off strength of the gel profile control agent of the present comparative example is 0.08 MPa / cm.

[0058] Comparative Example 6

[0059] The gel profile control agent of the present comparative example differs from the gel profile control agent of Example 3 only in that the present comparative example adjusts the mass ratio of resorcinol, urotropine and citric acid in the gelation accelerator to 0.5:1:1. The shut-off strength of the gel profile control agent of the present comparative example is 0.06 MPa / cm.

[0060] Comparative Example 7

[0061] The gel profile control agent of the present comparative example differs from the gel profile control agent of Example 3 only in that the present comparative example adjusts the mass ratio of resorcinol, urotropine and citric acid in the gelation accelerator to 1:0.5:1. The shut-off strength of the gel profile control agent of the present comparative example is 0.06 MPa / cm.

[0062] Comparative Example 8

[0063] The gel profile control agent of the present comparative example differs from the gel profile control agent of Example 3 only in that the present comparative example adjusts the mass ratio of resorcinol, urotropine and citric acid in the gelation accelerator to 1:1:0.5. The shut-off strength of the gel profile control agent of the present comparative example is 0.05 MPa / cm.

[0064] Comparative Example 9

[0065] The gel profile control agent of the present comparative example differs from the gel profile control agent of Example 3 only in that the present comparative example uses a uniform mixture of resorcinol and urotropine as the gelation accelerator, the total amount of the gelation accelerator being the same as in Example 3. The shut-off strength of the gel profile control agent of the present comparative example is 0.02 MPa / cm.

[0066] Comparative Example 10

[0067] The gel profile control agent of the present comparative example differs from the gel profile control agent of Example 3 only in that the present comparative example replaces the modified starch used in Example 3 with conventional corn starch. The shut-off strength of the gel profile control agent of the present comparative example is 0.03 MPa / cm.

[0068] The testing method of the plugging strength of the gel profile control agents in Examples 1-5 and Comparative Examples 1-10 above is a laboratory physical model experiment method. A self-made sand filling tube is used, which is 30 cm long, quartz sand (particle size 425-850 μm), and the driving pressure is adjustable from 0 to 10 MPa. When measuring, the prepared gel profile control agent is injected into the sand filling tube, then placed in a constant temperature water bath at 55°C for 7 days, and then taken out and installed on the physical model experiment device to conduct driving pressure experiment, and the plugging strength of the gel profile control agent is obtained.

[0069] The gel profile control agents for oilfield water flooding oil layer channeling control in Examples 1-5 are prepared on site when used, and then continuously injected into the profile control well by using an injection pump.

Claims

1. A gel profile control agent for plugging and controlling channeling in water-drive oil reservoirs in oilfields, characterized in that: The gel profile control agent is mainly made of partially hydrolyzed polyacrylamide, organic chromium crosslinking agent, reinforcing agent, glue promoter and water; the mass ratio of the partially hydrolyzed polyacrylamide, chromium salt crosslinking agent, reinforcing agent and glue promoter is 0.4-0.6:0.3-0.5:2-4:0.3-0.4; the reinforcing agent is sodium bentonite and modified starch, and the mass ratio of the sodium bentonite and modified starch is 1-2:1-2; the glue promoter is resorcinol, urotropine and organic acid, and the mass ratio of the resorcinol, urotropine and organic acid is 0.9-1.2:0.9-1.2:0.8-1.3; the organic chromium crosslinking agent is chromium acetate and / or chromium lactate; the mass ratio of the partially hydrolyzed polyacrylamide and water is 0.4-0.6:98.3-98.7; the modified starch is pregelatinized starch; and the organic acid is citric acid.

2. The gel profile control agent for use in waterflooding of oil reservoirs according to claim 1, characterized in that: The molecular weight of the partially hydrolyzed polyacrylamide is 8-12 million, and the degree of hydrolysis is 20-25%.

3. The gel profile control agent for use in waterflooding of oil reservoirs according to claim 1 or 2, characterized in that: The mass ratio of the partially hydrolyzed polyacrylamide, organic chromium crosslinking agent, reinforcing agent and glue promoter is 0.4-0.6:0.3-0.5:3:0.

3.

4. The gel profile control agent for blocking channeling of an oil reservoir by oilfield water according to claim 1 or 2, characterized by: The modified starch is pregelatinized corn starch.

5. The gel profile control agent for blocking channeling of an oil reservoir by oilfield water according to claim 1 or 2, characterized by: The preparation method of the gel profile control agent comprises the following steps: uniformly mixing water and organic chromium crosslinking agent to obtain a crosslinking agent solution; uniformly mixing a mixture of partially hydrolyzed polyacrylamide, reinforcing agent and glue promoter with the crosslinking agent solution, and the gel profile control agent is obtained.

6. The gel profile control agent for blocking channeling of an oil reservoir by oilfield water according to claim 1 or 2, characterized by: The particle size of the sodium bentonite and modified starch is more than 150 mesh.