Bacteria-resistant hydrogel profile control agent as well as preparation method and application thereof

Abstract

The invention relates to a bacteria-resistant hydrogel profile control agent as well as a preparation method and application thereof. The antibacterial hydrogel profile control agent is prepared from the following components in percentage by weight: 0.10 to 0.50 percent of polymer, 0.10 to 1.00 percent of organic resin, 0.10 to 0.60 percent of cross-linking agent, 0.01 to 0.30 percent of conditioning agent, 0.05 to 0.30 percent of bacteriostatic agent and the balance of oilfield injection water. According to the antibacterial hydrogel profile control agent provided by the invention, a polymer and water-soluble phenolic resin are used as main structures of a gel network, organic chromium is used as a cross-linking agent, oxalic acid or ammonium chloride is used as a regulator, and sodium nitrite is used as a bacteriostatic agent; by promoting the reproduction of nitrate reducing bacteria in water, the growth of sulfate reducing bacteria, saprophytic bacteria and iron bacteria is inhibited, the influence of strains on a gel system is reduced, and the gel has controllable gel forming time and strength, excellent bacteria resistance and long-term stability.

Description

Technical Field

[0001] The invention relates to a bacteria-resistant hydrogel profile control agent and a preparation method and application thereof, belonging to the technical field of oil and gas development. Background Art

[0002] Injecting profile control agents into water injection wells is the main method for plugging high permeability layers / zones in oil fields at home and abroad. Profile control plugging agents can divert the flow of injected water and transfer it into low permeability layers / zones, thereby expanding the swept volume of injected water and improving oil recovery efficiency, thereby recovering crude oil from low permeability layers / zones. Polymer gel profile control agents have the advantages of controllable gel strength, adjustable crosslinking time, and low price, so they are widely used in water plugging and profile control operations in oil reservoirs. Among them, the most widely used are partially hydrolyzed polyacrylamide (HPAM) plugging agents, which mainly include HPAM / inorganic delayed crosslinking system and HPAM / organic crosslinking system.

[0003] Although the above plugging agents meet the requirements of temperature and salt resistance, they have played a good role in the production practice of high-temperature and high-mineralization oil fields. However, in the process of oil field production, as a large amount of water and chemicals are injected into the formation, the microbial population of the ground system inside the formation changes, leading to the growth of some harmful bacteria. These harmful bacteria are roughly divided into three categories, namely sulfate-reducing bacteria (SRB), saprophytic bacteria (TGB) and iron bacteria (FB). These bacteria will destroy the gelation stability of the gel, causing the viscosity of the gel to drop rapidly, and the gel will turn black and smelly. Among them, sulfate-reducing bacteria (SRB) is the most important harmful bacteria that affects the gelation stability of the gel. There are two main reasons why SRB causes the viscosity of the gel to decrease: ① SRB directly grows and reproduces with HPAM as a carbon source or nitrogen source, and HPAM is degraded into small molecules, causing the viscosity to decrease; ② SO4 produced by SRB metabolism 2- And the Fe produced by SRB corrosion 2+ The degradation products are used by SRB as nutrient substrates, promoting the growth and reproduction of SRB and further degrading HPAM.

[0004] However, due to the limitations of regional environment and cost control, the existing profile control agents mainly use oilfield injection water as preparation water, so they inevitably contain sulfate-reducing bacteria, saprophytes or iron bacteria. At present, the control measures for SRB mainly include physical methods (ultraviolet rays, ultrasound, etc.), chemical fungicides, electrochemical protection, etc., but these methods cannot completely eliminate SRB, and chemical drugs such as fungicides themselves will also damage the gel structure, resulting in low gel viscosity, thereby affecting the water plugging and profile control operations of the reservoir. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a bacteria-resistant hydrogel profile control agent and its preparation method and application. The profile control agent effectively solves the technical problems of the existing partially hydrolyzed polyacrylamide (HPAM) profile control agent, such as gel blackening, odor, viscosity reduction, poor stability and short plugging validity period, which are easy to occur when the oil field produced fluid with high content of sulfate-reducing bacteria is used as injection water to prepare the gel system.

[0006] The technical solution of the present invention is as follows:

[0007] A bacterium-resistant hydrogel profile control agent, comprising the following components by weight percentage:

[0008] Polymer 0.10-0.50%, organic resin 0.10-1.00%, cross-linking agent 0.10-0.60%, regulator 0.01-0.30%, antibacterial agent 0.05-0.30%, and the balance is oil field injection water.

[0009] Preferably according to the present invention, the polymer is partially hydrolyzed polyacrylamide.

[0010] More preferably, the viscosity average molecular weight of the partially hydrolyzed polyacrylamide is 25 to 30 million.

[0011] According to the preferred embodiment of the present invention, the organic resin is a phenolic resin;

[0012] More preferably, the organic resin is a water-soluble phenolic resin.

[0013] Preferably according to the present invention, the cross-linking agent is an organic chromium cross-linking agent.

[0014] More preferably, the cross-linking agent is chromium acetate.

[0015] Preferably according to the present invention, the regulator is oxalic acid or ammonium chloride.

[0016] Preferably according to the present invention, the antibacterial agent is sodium nitrite.

[0017] According to the present invention, the preparation method of the above-mentioned antibacterial hydrogel profile control agent comprises the following steps:

[0018] (1) dissolving the antibacterial agent in a portion of the oil field injection water, stirring and dissolving, and preparing an antibacterial agent solution with a mass fraction of 5 to 20%;

[0019] (2) Adding the antibacterial agent solution to the remaining oil field injection water according to the ratio, stirring and dissolving; then adding the organic resin, the regulator and the polymer in sequence, stirring and dissolving; then adding the cross-linking agent, stirring and dissolving; finally, after constant temperature drying, obtaining the antibacterial hydrogel profile control agent.

[0020] The preparation method provided by the present invention first prepares the antibacterial agent into an antibacterial agent solution with a mass fraction of 5 to 20%, and then adds the antibacterial agent into the reaction system, so as to better control the progress of the reaction.

[0021] Preferably according to the present invention, in step (2), the stirring and dissolving time is 5 to 180 minutes.

[0022] Preferably according to the present invention, in step (2), the temperature of the constant temperature drying oven is 55°C.

[0023] Application of the above-mentioned bacteria-resistant hydrogel profile control agent in oil and gas reservoir exploitation.

[0024] The technical features of the present invention are as follows:

[0025] The antibacterial hydrogel profile control agent provided by the present invention forms a self-crosslinking network through the polycondensation reaction of a water-soluble phenolic resin, forms an inorganic crosslinking network with a polymer and an organic chromium, and forms an organic crosslinking network with a polymer and a phenolic resin. These three types of crosslinking networks together form an inorganic / organic hybrid crosslinking system, and realize the interpenetrating structure of rigid and flexible segments in a three-dimensional gel network. The antibacterial properties of the rigid structure and the physical barrier effect on the polymer flexible network are combined with the chemical antibacterial effect of the antibacterial agent in the gel system, which together give the present invention excellent antibacterial properties.

[0026] The present invention is specially developed for preparing a profile control system using oilfield produced fluid with high content of sulfate-reducing bacteria (SRB) as injection water. Its bacterial resistance is achieved through the following strategies: (1) using the partial network constructed by phenolic resin to strengthen the antibacterial properties of the gel structure; (2) adding sodium nitrite to activate the activity of nitrate-reducing bacteria (NRB) or denitrifying bacteria (DNB), and inhibiting the growth of SRB through matrix competition; (3) introducing metal ion-assisted cross-linking agents to improve the mechanical properties of the gel. These technical improvements effectively inhibit the influence of SRB on the stability of the profile control system, while significantly enhancing the strength of the gel and prolonging its stability period.

[0027] Beneficial effects of the present invention:

[0028] 1. The present invention provides a bacteriostatic hydrogel profile control agent, which has polymer and water-soluble phenolic resin as the main structure of the gel network, organic chromium as a cross-linking agent, oxalic acid or ammonium chloride as a regulator, and sodium nitrite as an antibacterial agent. The profile control agent has controllable gelation time and strength, excellent bacteriostatic performance, and long-term stability.

[0029] 2. The antibacterial hydrogel profile control agent provided by the present invention adopts sodium nitrite as an antibacterial agent, which promotes the reproduction of nitrate-reducing bacteria in water, thereby inhibiting the growth of sulfate-reducing bacteria, saprophytes and iron bacteria, and reducing the influence of bacteria on the gel system.

[0030] 3. The preparation method of the antibacterial hydrogel profile control agent provided by the present invention is simple to operate, has strong operability, is suitable for large-scale industrial production, and the obtained product has stable quality and excellent environmental adaptability.

[0031] 4. The oilfield hydrogel profile control agent provided by the present invention has a base liquid in a solution state on the ground. After being injected into the formation, the formation temperature is used to prompt the cross-linking agent to release active substances, which react with the polymer to promote the condensation reaction of the phenolic resin, and cross-link with the active groups on the polymer macromolecular chain to form an inorganic / organic hybrid cross-linked three-dimensional gel network structure, thereby forming a gel embolism in the high permeability strip or large pore, thereby improving the plugging efficiency. DETAILED DESCRIPTION

[0032] The technical scheme of the present invention is further described below in conjunction with the embodiments, but the protection scope of the present invention is not limited thereto. The materials involved in the embodiments, unless otherwise specified, are all common commercially available products; the experimental operations involved in the embodiments, unless otherwise specified, are all conventional operations in the art.

[0033] The experimental instruments used in the present invention are conventional experimental instruments such as an electric stirrer, a precision electronic balance, a Brookfield viscometer, and a constant temperature drying oven.

[0034] The oilfield injection water of the present invention is the oilfield injection water from Daqing, which contains sulfate-reducing bacteria, saprophytic bacteria or iron bacteria, and the content of sulfate-reducing bacteria is 0.25-2.5×10 4 Pieces / mL.

[0035] The total mineralization of the oil field injected from Daqing is 4696.9 mg / L, and the specific components are shown in Table 1 below:

[0036] Table 1

[0037] Ionic composition <![CDATA[Na + ]]> <![CDATA[Mg 2+ ]]> <![CDATA[Ca 2+ ]]> <![CDATA[HCO3 - ]]> <![CDATA[SO4 2- ]]> <![CDATA[CO3 2- ]]> <![CDATA[Cl - ]]> Content (mg / L) 1278.7 32.5 42.6 2627.9 4.5 140 570.7

[0038] Example 1

[0039] A bacterium-resistant hydrogel profile control agent, comprising the following components by weight percentage:

[0040] 2.500g (0.25%) partially hydrolyzed polyacrylamide, 2.000g (0.20%) water-soluble phenolic resin, 2.000g (0.20%) chromium acetate, 2.000g (0.20%) ammonium chloride, 0.500g (0.05%) sodium nitrite, 991g (99.1%) oil field injection water.

[0041] The viscosity average molecular weight of the partially hydrolyzed polyacrylamide is 25 million, and the content of sulfate-reducing bacteria in the oil field injection water is 2500 / mL.

[0042] The preparation method of the above-mentioned antibacterial hydrogel profile control agent comprises the following steps:

[0043] (1) Dissolve sodium nitrite in 2 g of oilfield injection water, stir and dissolve for 8 min until uniform, and prepare a sodium nitrite solution with a mass fraction of 20% (mass: 2.5 g);

[0044] (2) According to the proportion, add sodium nitrite solution to the remaining 989g of oil field injection water, stir and dissolve for 8 minutes until uniform; add phenolic resin, stir and dissolve for 8 minutes until uniform; add ammonium chloride, stir and dissolve for 8 minutes until uniform; add partially hydrolyzed polyacrylamide, stir and dissolve for 120 minutes until uniform; then add chromium acetate, stir and dissolve for 12 minutes until uniform, to obtain a bacteria-resistant hydrogel profile control agent.

[0045] Example 2

[0046] A bacterium-resistant hydrogel profile control agent, comprising the following components by weight percentage:

[0047] 1.500g (0.15%) partially hydrolyzed polyacrylamide, 2.000g (0.20%) water-soluble phenolic resin, 3.000g (0.30%) chromium acetate, 2.000g (0.20%) ammonium chloride, 0.500g (0.05%) sodium nitrite, 991g (99.1%) oil field injection water.

[0048] The viscosity average molecular weight of the partially hydrolyzed polyacrylamide is 25 million, and the content of sulfate-reducing bacteria in the oil field injection water is 2500 / mL.

[0049] The preparation method of the above-mentioned antibacterial hydrogel profile control agent comprises the following steps:

[0050] (1) Dissolve sodium nitrite in 2 g of oilfield injection water, stir and dissolve for 8 min until uniform, and prepare a sodium nitrite solution with a mass fraction of 20% (mass: 2.5 g);

[0051] (2) According to the proportion, add sodium nitrite solution to the remaining 989g of oil field injection water, stir and dissolve for 8 minutes until uniform; add phenolic resin, stir and dissolve for 8 minutes until uniform; add ammonium chloride, stir and dissolve for 8 minutes until uniform; add partially hydrolyzed polyacrylamide, stir and dissolve for 120 minutes until uniform; then add chromium acetate, stir and dissolve for 12 minutes until uniform, to obtain a bacteria-resistant hydrogel profile control agent.

[0052] Example 3

[0053] A bacterium-resistant hydrogel profile control agent, comprising the following components by weight percentage:

[0054] 2.500g (0.25%) partially hydrolyzed polyacrylamide, 2.000g (0.20%) water-soluble phenolic resin, 3.000g (0.30%) chromium acetate, 0.500g (0.05%) oxalic acid, 0.500g (0.05%) sodium nitrite, 991.5g (99.15%) oil field injection water.

[0055] The viscosity average molecular weight of the partially hydrolyzed polyacrylamide is 25 million, and the content of sulfate-reducing bacteria in the oil field injection water is 2500 / mL.

[0056] The preparation method of the above-mentioned antibacterial hydrogel profile control agent comprises the following steps:

[0057] (1) Dissolve sodium nitrite in 2 g of oilfield injection water, stir and dissolve for 8 min until uniform, and prepare a sodium nitrite solution with a mass fraction of 20% (mass: 2.5 g);

[0058] (2) According to the proportion, add sodium nitrite solution to the remaining 989g of oil field injection water, stir and dissolve for 8 minutes until uniform; add phenolic resin, stir and dissolve for 8 minutes until uniform; add oxalic acid, stir and dissolve for 8 minutes until uniform; add partially hydrolyzed polyacrylamide, stir and dissolve for 120 minutes until uniform; then add chromium acetate, stir and dissolve for 12 minutes until uniform, to obtain a bacteria-resistant hydrogel profile control agent.

[0059] Example 4

[0060] A bacterial-resistant hydrogel profile control agent, the specific components and preparation method are the same as those described in Example 1, except that the content of sulfate-reducing bacteria in the oil field injection water is 1×10 4 Pieces / mL.

[0061] Example 5

[0062] A bacterial-resistant hydrogel profile control agent, the specific components and preparation method are the same as those described in Example 1, except that the content of sulfate-reducing bacteria in the oil field injection water is 2.5×10 4 Pieces / mL.

[0063] Comparative Example 1

[0064] A hydrogel profile control agent, the specific components and preparation method are the same as those described in Example 1, except that no water-soluble phenolic resin, ammonium chloride and sodium nitrite are added, and only partially hydrolyzed polyacrylamide and chromium acetate are used.

[0065] Comparative Example 2

[0066] A hydrogel profile control agent, the specific components and preparation method are the same as those described in Comparative Example 1, except that the content of sulfate-reducing bacteria in the oil field injection water is 1×104 Pieces / mL.

[0067] Comparative Example 3

[0068] A hydrogel profile control agent, the specific components and preparation method are the same as those described in Comparative Example 1, except that the content of sulfate-reducing bacteria in the oil field injection water is 2.5×10 4 Pieces / mL.

[0069] Comparative Example 4

[0070] A hydrogel profile control agent, the specific components and preparation method are the same as those described in Example 1, except that no partially hydrolyzed polyacrylamide and chromium acetate are added, and only water-soluble phenolic resin, ammonium chloride and sodium nitrite are used.

[0071] Comparative Example 5

[0072] A hydrogel profile control agent, the specific components and preparation method are the same as those described in Comparative Example 4, except that the content of sulfate-reducing bacteria in the oil field injection water is 1×10 4 Pieces / mL.

[0073] Comparative Example 6

[0074] A hydrogel profile control agent, the specific components and preparation method are the same as those described in Comparative Example 4, except that the content of sulfate-reducing bacteria in the oil field injection water is 2.5×10 4 Pieces / mL.

[0075] Test Example 1

[0076] The performance of the hydrogel profile control agents for oil field profile control prepared in Examples 1, 4 to 5 and Comparative Examples 1 to 3 was evaluated.

[0077] 1. Determination of gelling properties

[0078] The antibacterial hydrogel profile controlling agents prepared in Examples 1, 4-5 and the hydrogel profile controlling agents prepared in Comparative Examples 1-3 were placed in sample bottles, sealed, and placed in an electric constant temperature drying oven at 55°C. The bottles were taken out regularly, and the gelling time of the hydrogel profile controlling agents in Examples 1, 4-5 and Comparative Examples 1-3 was measured respectively, and the gelling strength was measured using a Brookfield viscometer. The experimental results of Examples 1, 4-5 and Comparative Examples 1-3 are shown in Tables 2 and 3 below.

[0079] Table 2. Gelation time and gel strength of the gels in Examples 1 and 4 to 5

[0080] Group Sulfate-reducing bacteria / unit / mL Gelation time / h Gel strength / mPa.s Example 1 2500 38 33600 Example 4 <![CDATA[1.0×10 4 ]]> 60 18300 Example 5 <![CDATA[2.5×10 4 ]]> 65 18000

[0081] Table 3. Gelation time and gelation strength of gels in comparative examples 1 to 3

[0082] Group Sulfate-reducing bacteria / unit / mL Gelation time / h Gel strength / mPa.s Comparative Example 1 2500 10 22600 Comparative Example 2 <![CDATA[1.0×10 4 ]]> 16 11200 Comparative Example 3 <![CDATA[2.5×10 4 ]]> 20 8600

[0083] From the data comparison of Table 2 and Table 3, it can be seen that Examples 1, 4-5 and Comparative Examples 1-3 can all form stable deformable gel systems with good mechanical properties, but the gelling strength in Examples 1, 4-5 is significantly higher than that in Comparative Examples 1-3, and the gelling time is also longer than that in the latter. This shows that the present invention inhibits the growth of sulfate-reducing bacteria by adding phenolic resin, regulator and antibacterial agent, reduces the influence of bacteria on the gel system, plays a good antibacterial effect, and exhibits excellent antibacterial performance. Under the same sulfate-reducing bacteria experimental conditions as Examples 1, 4-5, Comparative Examples 1-3 can enhance the gelling strength of the gel system and prolong the gelling time, which is beneficial for the profile control system to effectively adjust the water absorption profile of the deep part of the reservoir.

[0084] 2. Determination of long-term stability of gel

[0085] The antibacterial hydrogel profile control agents prepared in Examples 1, 4-5 and the hydrogel profile control agents prepared in Comparative Examples 1-3 were placed in sample bottles, sealed, and placed in an electric constant temperature drying oven at 55°C. The samples were taken out regularly to measure the viscosity of the hydrogel profile control agents in Examples 1, 4-5 and Comparative Examples 1-3, and to observe the long-term stability of the gels. The experimental results of Examples 1, 4-5 and Comparative Examples 1-3 are shown in Tables 4 and 5 below.

[0086] Table 4 Gel viscosity of Examples 1, 4 to 5 at different times

[0087]

[0088] Table 5. Gel viscosity of the gels of Comparative Examples 1 to 3 at different times

[0089]

[0090] It can be seen from Tables 4 to 5 that the antibacterial hydrogel profile control agents prepared in Examples 1, 4 to 5 of the present invention can still maintain a relatively high gel viscosity at 180 days. The hydrogel profile control agents prepared in Comparative Examples 1 to 3 will rapidly reduce viscosity in about 5 to 10 days, and their gel viscosity is much lower than the viscosity of the gel under the conditions of the antibacterial hydrogel profile control agents in Examples 1, 4 to 5 of the present invention. This fully demonstrates that the long-term stability of the antibacterial hydrogel profile control agents prepared in Examples 1, 4 to 5 of the present invention is significantly better than that of the hydrogel profile control agents in Comparative Examples 1 to 3. This is because the present invention fully utilizes the antibacterial properties of the rigid structure formed by the water-soluble phenolic resin and the physical barrier effect on the flexible polymer network by adding water-soluble phenolic resin, ammonium chloride and sodium nitrite, while producing antibacterial function, it also improves the long-term stability of the profile control agent.

[0091] Test Example 2

[0092] The performance of the hydrogel profile control agents for oil field profile control prepared in Examples 1, 4 to 5 and Comparative Examples 4 to 6 was evaluated.

[0093] 1. Determination of gelling properties

[0094] The experimental method is as in Experimental Example 1, the experimental results of Examples 1, 4 to 5 are shown in Table 1, and the experimental results of Comparative Examples 4 to 6 are shown in Table 6 below.

[0095] Table 6. Gelation time and gel strength of gels in comparative examples 4 to 6

[0096] Group Sulfate-reducing bacteria / unit / mL Gelation time / h Gel strength / mPa.s Comparative Example 4 2500 - Colloidal flocculation precipitation Comparative Example 5 <![CDATA[1.0×10 4 ]]> - Colloidal flocculation precipitation Comparative Example 6 <![CDATA[2.5×10 4 ]]> - Colloidal flocculation precipitation

[0097] From the comparison of the data in Table 1 and Table 6, it can be seen that, under the same experimental conditions as Examples 1 and 4 to 5, Comparative Examples 4 to 6 exhibited the phenomenon of colloid flocculation and precipitation, and failed to form a stable deformable gel system with good mechanical properties.

[0098] 2. Determination of long-term stability of gel

[0099] The hydrogel-type profile control agents of Comparative Examples 4 to 6 were colloidally flocculated and precipitated, and no stability was observed.

[0100] In summary, the antibacterial hydrogel profile control agent provided by the present invention has polymer and water-soluble phenolic resin as the main structure of the gel network, organic chromium as a cross-linking agent, oxalic acid or ammonium chloride as a regulator, and sodium nitrite as an antibacterial agent. It has controllable gelation time and strength, excellent antibacterial properties, and long-term stability.

[0101] The above-described embodiments are only preferred specific implementation schemes of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A bacterium-resistant hydrogel profile control agent, characterized in that: The composition is as follows by weight percentage: Polymer 0.10-0.50%, organic resin 0.10-1.00%, cross-linking agent 0.10-0.60%, regulator 0.01-0.30%, antibacterial agent 0.05-0.30%, and the balance is oil field injection water.

2. The antibacterial hydrogel profile control agent according to claim 1, characterized in that: The polymer is partially hydrolyzed polyacrylamide; More preferably, the viscosity average molecular weight of the partially hydrolyzed polyacrylamide is 25 to 30 million.

3. The antibacterial hydrogel profile control agent according to claim 1, characterized in that: The organic resin is a phenolic resin; More preferably, the organic resin is a water-soluble phenolic resin.

4. The antibacterial hydrogel profile control agent according to claim 1, characterized in that: The cross-linking agent is an organic chromium cross-linking agent; More preferably, the cross-linking agent is chromium acetate.

5. The antibacterial hydrogel profile control agent according to claim 1, characterized in that: The regulator is oxalic acid or ammonium chloride.

6. The antibacterial hydrogel profile control agent according to claim 1, characterized in that: The antibacterial agent is sodium nitrite.

7. The method for preparing the antibacterial hydrogel profile control agent according to claim 1, characterized in that: The steps include: (1) dissolving the antibacterial agent in a portion of the oil field injection water, stirring and dissolving, and preparing an antibacterial agent solution with a mass fraction of 5 to 20%; (2) Adding the antibacterial agent solution to the remaining oil field injection water according to the ratio, stirring and dissolving; then adding the organic resin, the regulator and the polymer in sequence, stirring and dissolving; then adding the cross-linking agent, stirring and dissolving; finally, after constant temperature drying, obtaining the antibacterial hydrogel profile control agent.

8. The preparation method according to claim 7, characterized in that: In step (2), the stirring and dissolving time is 5 to 180 minutes.

9. The preparation method according to claim 7, characterized in that: In step (2), the temperature of the constant temperature drying oven is 55°C.

10. Use of the bacteria-resistant hydrogel profile control agent according to claim 1 in oil and gas reservoir exploitation.

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