Active polymer microgels, methods of making and using the same

Abstract

The application provides an active polymer microgel and a preparation method and application thereof. The active polymer microgel is prepared by emulsion polymerization with N,N-dimethyl acrylamide, a hydroxymethyl amide monomer, a methacrylic acid ester monomer and an emulsifier as raw materials under the action of a chain extender and an initiator. The inventor controls a large number of active groups in the active polymer microgel to provide crosslinking sites, improves the crosslinking density of subsequent plugging gels, and makes the plugging gels have a three-dimensional network structure after solidification, so that the crosslinking speed and crosslinking quality are improved, and the technical requirements of the plugging gels applied to deep high-temperature leakage layers on crosslinking agents are met.

Description

Technical Field

[0001] This invention belongs to the field of drilling leakage prevention and plugging technology, and particularly relates to an active polymer microgel, its preparation method and application. Background Technology

[0002] As oilfield exploration and development continue, drilling fluid losses are becoming increasingly frequent in complex geological conditions, posing new challenges to the performance requirements of plugging materials. Conventional rigid materials are mainly composed of rigid particles and fibers. These materials form a sealing layer through bridging to plug leaks, but their effectiveness is often poor due to limitations such as significant gravity settling and inability to penetrate deep into the leaking layer. Gel plugging agents, with their flexible gelation time and adaptability to leak space, have become an important branch of plugging materials. Based on whether a crosslinking agent is used, polymer gels are mainly divided into crosslinked gel-forming gels and non-crosslinked gels. Crosslinked gel-forming gels refer to viscoelastic gels formed by injecting polymers (or monomers), crosslinking agents, catalysts, etc., in the form of an aqueous solution into the downhole leakage channel, where a crosslinking reaction occurs in the formation environment. After gelling in the formation environment, they can seal the leakage channel, exhibiting better adaptability and wider application.

[0003] High temperatures and drilling fluid loss are common problems encountered during deep formation drilling. Compared to shallow and medium-depth formations, deep formation plugging places higher demands on the temperature resistance of materials. Commonly used plugging gel crosslinking agents generally have a temperature resistance below 120℃, exhibiting poor high-temperature stability. This results in the plugging gel failing to effectively seal deep leakage spaces, leading to a high risk of re-leakage later. Existing crosslinking agents have not shown effective performance at higher temperatures, and traditional organometallic crosslinking agents have poor environmental friendliness, making them unsuitable for deep formation plugging requirements. Therefore, it is necessary to design and develop crosslinking agents for plugging gels with good high-temperature stability to ensure effective sealing of deep, high-temperature leakage formations. Summary of the Invention

[0004] To address the problem of poor high-temperature resistance of existing crosslinking agents used as crosslinking agents in plugging gels, this invention provides an active polymer microgel, its preparation method, and its application. The active polymer microgel possesses excellent temperature resistance and can effectively crosslink plugging gels in high-temperature formation environments, ensuring the plugging effect of the plugging gel in deep, high-temperature leaking formations.

[0005] To achieve the above objectives, the first aspect of the present invention provides an active polymer microgel, which is a polymer product obtained by emulsion polymerization using N,N-dimethylacrylamide, hydroxymethylamide compounds, methacrylate compounds and emulsifiers as raw materials, under the action of chain extenders and initiators.

[0006] According to the present invention, the molecular weight of the active polymer microgel is 500,000 to 5,000,000.

[0007] According to the present invention, the mass ratio of the N,N-dimethylacrylamide, hydroxymethylamide compound, and methacrylate compound is (25-30):1:(5-8); and / or

[0008] The total mass of the N,N-dimethylacrylamide, hydroxymethylamide, and methacrylate compounds is 100%, the mass of the emulsifier is 2.50-6.00 wt%, the mass of the chain extender is 0.10-0.60 wt%, and the mass of the initiator is 0.25-0.90 wt%.

[0009] According to the present invention, the hydroxymethylamide compounds include at least one of N-hydroxymethylacetamide, N-hydroxymethylacrylamide, and N-hydroxymethylbenzamide; and / or

[0010] The methacrylate compounds include at least one of methyl methacrylate, butyl methacrylate, and lauryl methacrylate; and / or

[0011] The emulsifier is selected from at least one of Span-80, Tween-80, Span-60, Tween-60 and OP-10;

[0012] and / or

[0013] The chain extender is ethylenediaminetetraacetic acid; and / or

[0014] The initiator is a mixture of potassium persulfate and sodium bisulfite.

[0015] According to the present invention, the HLB value of the emulsifier is 7-11; and / or

[0016] In the initiator, the mass ratio of potassium persulfate to sodium bisulfite is 3:1.

[0017] A second aspect of the present invention provides a method for preparing active polymer microgels as described in the first aspect of the present invention, comprising the following steps:

[0018] Step 1) Mix the N,N-dimethylacrylamide, hydroxymethylamide compound, emulsifier and water to obtain an aqueous phase;

[0019] Step 2) Using the methacrylate compound as the oil phase, drop it into the aqueous phase to obtain an oil-in-water emulsion;

[0020] Step 3) The oil-in-water emulsion is subjected to emulsion polymerization under the action of the chain extender and initiator to obtain the active polymer microgel.

[0021] According to the present invention, the total mass concentration of the oil-in-water emulsion, N,N-dimethylacrylamide, hydroxymethylamide compounds, methacrylate compounds and emulsifier is 35.50-36.50 wt%, which is 100% by mass.

[0022] and / or

[0023] The mass ratio of the N,N-dimethylacrylamide, hydroxymethylamide compound, and methacrylate compound is (25-30):1:(5-8); and / or

[0024] The total mass of the N,N-dimethylacrylamide, hydroxymethylamide, and methacrylate compounds is 100%, the mass of the emulsifier is 2.50-6.00 wt%, the mass of the chain extender is 0.10-0.60 wt%, and the mass of the initiator is 0.25-0.90 wt%.

[0025] According to the present invention, in step 3), the oil-in-water emulsion is first deoxygenated and heated, and then the chain extender and initiator are added to carry out the emulsion polymerization reaction.

[0026] According to the present invention, the temperature of the emulsion polymerization reaction is 50°C; and / or the duration is 5-8 hours.

[0027] The application of the active polymer microgel according to the present invention or the active polymer microgel prepared by the method of the present invention as a crosslinking agent, especially in the preparation of plugging gel.

[0028] The beneficial effects of this invention are:

[0029] To address the problem of poor high-temperature resistance of existing crosslinking agents used as crosslinking agents in sealing gels, this invention provides an active polymer microgel, its preparation method, and its application. The active polymer microgel is prepared by emulsion polymerization using N,N-dimethylacrylamide, hydroxymethylamide compounds, methacrylate compounds, and emulsifiers as raw materials, under the action of chain extenders and initiators. The inventors, through raw material formulation and preparation process design, control the presence of numerous active groups in the active polymer microgel to provide crosslinking sites. This helps to improve the crosslinking density of the subsequent sealing gel, resulting in a three-dimensional network structure after curing, thus improving both the crosslinking speed and quality. Indoor experiments have shown that the sealing gel prepared using the active polymer microgel provided by this invention, after curing, exhibits: 1) a manual tensile strength exceeding 7.5 times after aging at 160℃ for 24 hours before fracture, demonstrating high shear toughness; 2) effective sealing of 5mm wide cracks after heating at 160℃ for 3 hours, with a sealing compressive strength exceeding 7MPa. The above-mentioned indoor experimental results demonstrate that the crosslinking effect of the active polymer microgel provided by this invention on the plugging gel remains stable and effective at high temperatures not lower than 160°C. The plugging gel prepared using the active polymer microgel as a crosslinking agent can rapidly solidify into an adhesive after injection into the target leaking layer to seal it. This sealing remains effective at high temperatures not lower than 160°C, and its high shear toughness also gives it excellent crack adaptability, enabling it to prevent and seal leaks in cracks in different geological environments. As can be seen from the various raw materials used in preparing the active polymer microgel of this invention, compared with traditional organometallic crosslinking agents, the active polymer microgel and its preparation method provided in this application have better environmental friendliness. In summary, the active polymer microgel prepared by the method provided by this invention, or the active polymer microgel provided by this invention, can meet the technical requirements for crosslinking agents in plugging gels applied to deep high-temperature leaking layers. Attached Figure Description

[0030] Figure 1 The infrared spectrum of the active polymer microgel G1 prepared in Example 1 is shown.

[0031] Figure 2 The image shows a physical picture of the plugging gel A1 obtained by crosslinking the active polymer microgel G1 prepared in Example 1 as a crosslinking agent. Detailed Implementation

[0032] The present invention will be further described below with reference to the embodiments. However, the embodiments of the present invention are merely illustrative examples and should not be construed as limiting the present invention under any circumstances.

[0033] Example 1

[0034] Step 1) Weigh 8.00g of N,N-dimethylacrylamide and 0.30g of N-hydroxymethylacrylamide, and slowly add them to 18.6g of deionized water. Stir at about 300r / min for 10min to fully dissolve N,N-dimethylacrylamide and N-hydroxymethylacrylamide. Then, while stirring, add the emulsifier (specifically a mixture of 0.13g of Span-80 and 0.16g of Tween-80, with an HLB value of 10.20) to the above liquid and stir at about 500r / min for about 10min until fully dispersed to obtain the aqueous phase.

[0035] Step 2) Weigh 1.70g of methyl methacrylate as the oil phase and add it dropwise to the aqueous phase obtained in Step 1). Stir at a speed of about 500r / min for 20min to obtain an oil-in-water emulsion.

[0036] Step 3) Transfer the oil-in-water emulsion obtained in Step 2) to a three-necked flask, purge with nitrogen, heat to 50°C, and then add 0.029 g of ethylenediaminetetraacetic acid as a chain extender and initiator (specifically 0.0435 g of potassium persulfate and 0.0145 g of sodium bisulfite) to initiate the polymerization reaction. After reacting for 6 hours, discharge the material. The resulting viscous liquid is the active polymer microgel G1, which is a crosslinking agent.

[0037] Example 2

[0038] Step 1) Weigh 8.06g of N,N-dimethylacrylamide and 0.32g of N-hydroxymethylbenzamide, and slowly add them to 18.6g of deionized water. Stir at about 300r / min for 15min to fully dissolve N,N-dimethylacrylamide and N-hydroxymethylbenzamide. Then, while stirring, add the emulsifier (specifically a mixture of 0.18g of Span-60 and 0.11g of Tween-60, with an HLB value of 8.56) to the above liquid. Stir at about 500r / min for about 10min until fully dispersed to obtain the aqueous phase.

[0039] Step 2) Weigh 1.61g of butyl methacrylate as the oil phase and add it dropwise to the aqueous phase obtained in Step 1). Stir at a speed of about 500r / min for 20min to obtain an oil-in-water emulsion.

[0040] Step 3) Transfer the oil-in-water emulsion obtained in Step 2) to a three-necked flask, purge with nitrogen, heat to 50°C, and then add 0.0145g of ethylenediaminetetraacetic acid as a chain extender and initiator (specifically including 0.0218g of potassium persulfate and 0.0073g of sodium bisulfite) to initiate the polymerization reaction. After reacting for 5 hours, discharge the material. The resulting viscous liquid is the active polymer microgel G2, which is a crosslinking agent.

[0041] Example 3

[0042] Step 1) Weigh 7.69g of N,N-dimethylacrylamide and 0.26g of N-hydroxymethylacetamide, and slowly add them to 18.6g of deionized water. Stir at about 300r / min for 20min to fully dissolve N,N-dimethylacrylamide and N-hydroxymethylacetamide. Then, while stirring, add the emulsifier (specifically a mixture of 0.33g of Span-80 and 0.25g of OP-10, with an HLB value of 8.26) to the above liquid and stir at about 500r / min for about 10min until fully dispersed to obtain the aqueous phase.

[0043] Step 2) Weigh 2.05g lauryl methacrylate as the oil phase and add it dropwise to the aqueous phase obtained in Step 1). Stir at a speed of about 500r / min for 20min to obtain an oil-in-water emulsion.

[0044] Step 3) Transfer the oil-in-water emulsion obtained in Step 2) to a three-necked flask, purge with nitrogen, heat to 50°C, and then add 0.058 g of ethylenediaminetetraacetic acid as a chain extender and initiator (specifically 0.0654 g of potassium persulfate and 0.0218 g of sodium bisulfite) to initiate the polymerization reaction. After reacting for 8 hours, the product is discharged, and the resulting viscous liquid is the active polymer microgel G3, which is a crosslinking agent.

[0045] Comparative Example 1

[0046] This comparative example provides an organoaluminum zirconium crosslinking agent, purchased from Zhengzhou Derong Technology Co., Ltd.

[0047] Comparative Example 2

[0048] This comparative example provides diethylenetriamine as a crosslinking agent.

[0049] Comparative Example 3

[0050] This comparative example provides N,N'-methylenebisacrylamide as a crosslinking agent.

[0051] Comparative Example 4

[0052] This comparative example follows the steps of Example 1, except that N,N-dimethylacrylamide in Example 1 is replaced with acrylamide, while the rest is the same as in Example 1, to prepare active polymer microgel DG1.

[0053] Comparative Example 5

[0054] This comparative example follows the steps of Example 1, except that the chain extender ethylenediaminetetraacetic acid (EDTA) in Example 1 is removed. Otherwise, it is the same as Example 1, and active polymer microgel DG2 is prepared.

[0055] Comparative Example 6

[0056] This comparative example follows the steps of Example 1, except that the mass of N,N-dimethylacrylamide and the mass of methyl methacrylate in Example 1 are adjusted to 1.7g and 8g respectively, while the rest is the same as in Example 1, to prepare active polymer microgel DG3.

[0057] Comparative Example 7

[0058] This comparative example follows the steps of Example 1, except that sodium bisulfite is not added and the mass of potassium persulfate is adjusted to 0.058 g. Otherwise, it is the same as Example 1, and active polymer microgel DG4 is prepared.

[0059] Comparative Example 8

[0060] Step 1) Weigh 8g of N,N-dimethylacrylamide and 0.3g of N-hydroxymethylacrylamide, and slowly add them to 18.6g of deionized water. Stir at about 300r / min for 10-20min to fully dissolve N,N-dimethylacrylamide and N-hydroxymethylacrylamide. Then, while stirring, add emulsifier (specifically 0.29g of Span-80, HLB value 4.3) to the above liquid and stir at about 500r / min for about 10min until fully dispersed to obtain the aqueous phase.

[0061] Step 2) Weigh 1.7g of methyl methacrylate and dissolve it in 25.2g of liquid paraffin as the oil phase. Add the aqueous phase obtained in Step 1) dropwise into the oil phase and stir at a speed of about 500r / min for 20min to obtain a reverse water-in-oil emulsion with an oil-water mass ratio of 1:1.

[0062] Step 3) Transfer the reversed water-in-oil emulsion obtained in Step 2) to a three-necked flask, purge with nitrogen, heat to 50°C, and then add 0.029 g of ethylenediaminetetraacetic acid as a chain extender and initiator (specifically 0.0435 g of potassium persulfate and 0.0145 g of sodium bisulfite) to initiate the polymerization reaction. After reacting for 6 hours, the product is discharged, and the resulting viscous liquid is the active polymer microgel DG5.

[0063] The following preparation examples are provided to prepare plugging gels using the active polymer microgels provided in Examples 1-3 and Comparative Examples 4-8, and the crosslinking agents provided in Comparative Examples 1-3.

[0064] Preparation Example 1

[0065] (1) First, weigh 10g of the high-temperature resistant compound (specifically, a mixture of acrylamide and 2-acrylamide-2-methylpropanesulfonic acid in a mass ratio of 1:1) and dissolve it in 100g of deionized water in a three-necked flask. Add 0.8g of the active polymer microgel G1 prepared in Example 1 as a crosslinking agent, place a magnetic stir bar in the flask, and stir thoroughly at room temperature for a period of time using a magnetic stirrer to obtain solution A.

[0066] (2) Weigh ammonium persulfate and sodium bisulfite in a mass ratio of 1:1, dissolve them in deionized water, and prepare an initiator solution B with a total mass concentration of 30wt% for ammonium persulfate and sodium bisulfite.

[0067] (3) Add initiator solution B dropwise to the prepared solution A to obtain a blend. The total mass of initiator solution B added accounts for 0.5 wt% of the mass of solution A. Stir continuously for 30 min, and connect the nitrogen bottle to the three-necked flask to purge nitrogen for 20 min to remove oxygen. After completion, transfer the blend to a water bath at 60°C for polymerization reaction for 6 h to obtain the plugging gel A1.

[0068] Preparation Example 2

[0069] The active polymer microgel G1 prepared in Example 1 of Preparation Example 1 was replaced with an equal mass of active polymer microgel G2 prepared in Example 2, and all other aspects were the same as in Preparation Example 1, to obtain the plugging gel A2.

[0070] Preparation Example 3

[0071] The active polymer microgel G1 prepared in Example 1 of Preparation Example 1 was replaced with an equal mass of active polymer microgel G3 prepared in Example 3, and all other aspects were the same as in Preparation Example 1, to obtain the plugging gel A3.

[0072] Comparative Preparation Example 1

[0073] The active polymer microgel G1 prepared in Example 1 of Preparation Example 1 was replaced with an equal mass of the organoaluminum zirconium crosslinking agent provided in Comparative Example 1, and all other aspects were the same as in Preparation Example 1, to obtain the plugging gel DA1.

[0074] Comparative Preparation Example 2

[0075] The active polymer microgel G1 prepared in Example 1 of Preparation Example 1 was replaced with an equal mass of diethylenetriamine provided in Comparative Example 2, and all other aspects were the same as in Preparation Example 1, to obtain the plugging gel DA2.

[0076] Comparative preparation example 3

[0077] The active polymer microgel G1 prepared in Example 1 of Preparation Example 1 was replaced with an equal mass of N,N'-methylenebisacrylamide provided in Comparative Example 3, and the rest was the same as in Preparation Example 1, to obtain the plugging gel DA3.

[0078] Comparative preparation example 4

[0079] The active polymer microgel G1 prepared in Example 1 of Preparation Example 1 was replaced with an equal mass of active polymer microgel DG1 prepared in Comparative Example 4, and all other steps were the same as in Preparation Example 1, to obtain the plugging gel DA4.

[0080] Comparative preparation example 5

[0081] The active polymer microgel G1 prepared in Example 1 of Preparation Example 1 was replaced with an equal mass of active polymer microgel DG2 prepared in Comparative Example 5, and all other steps were the same as in Preparation Example 1, to obtain the plugging gel DA5.

[0082] Comparative preparation example 6

[0083] The active polymer microgel G1 prepared in Example 1 of Preparation Example 1 was replaced with an equal mass of active polymer microgel DG3 prepared in Comparative Example 6, and the rest was the same as in Preparation Example 1, to obtain the leak-stopping gel DA6.

[0084] Comparative preparation example 7

[0085] The active polymer microgel G1 prepared in Example 1 of Preparation Example 1 was replaced with an equal mass of active polymer microgel DG4 prepared in Comparative Example 7, and the rest was the same as in Preparation Example 1, to obtain the leak-stopping gel DA7.

[0086] Comparative Preparation Example 8

[0087] The active polymer microgel G1 prepared in Example 1 of Preparation Example 1 was replaced with an equal mass of active polymer microgel DG5 prepared in Comparative Example 8, and the rest was the same as in Preparation Example 1, to obtain the leak-stopping gel DA8.

[0088] Test Example 1 - Characterization of the structure of active polymer microgels

[0089] Infrared spectroscopy was performed on the active polymer microgels G1-G3 prepared in Examples 1-3. The infrared spectrum of active polymer microgel G1 prepared in Example 1 is used as an example for detailed explanation.

[0090] Figure 1 The infrared spectrum of the active polymer microgel G1 prepared in Example 1 is shown. It can be seen that at 750 cm⁻¹... -1 The characteristic peaks at the left and right are caused by the -COC- vibration, 1650 cm⁻¹ -1 The characteristic peaks at the left and right are caused by the vibration of the C=C double bond, 2930 cm⁻¹. -1 The absorption peaks at the left and right are caused by the CH vibration in -CH3, 3558 cm⁻¹ -1The characteristic peaks at the left and right are caused by the NH stretching vibration, indicating that the monomers in the active polymer microgel G1 have been successfully polymerized.

[0091] Based on the infrared spectral determination and analysis of the active polymer microgels G2 and G3 prepared in Examples 2 and 3, it was found that each monomer in Examples 2 and 3 was successfully polymerized.

[0092] Test Example 2 - Shear toughness determination of plugging gel after high-temperature aging

[0093] First, the plugging gels prepared in Preparation Examples 1-3 and Comparative Preparation Examples 1-8 were heated and aged at a certain temperature. Then, the shear toughness of the aged plugging gel was measured by manually stretching the gel samples. The shear toughness was characterized by the ratio of the stretched length of the aged plugging gel to the original length of the aged plugging gel (or the stretching ratio). The larger the ratio of the stretched length to the original length, the better the shear toughness of the aged plugging gel. The specific test steps and conditions are as follows.

[0094] A. Weigh out appropriate and equal amounts of sealing gels A1-A3 and DA1-DA8, place them in a constant temperature and humidity chamber at 160℃ and heat for aging for 24 hours to obtain aged sealing gels for later use.

[0095] B. Prepare cylindrical dumbbell test samples of uniform specifications from the various aged plugging gels obtained in A. The total length of the cylindrical dumbbell test samples is 10cm, the length of the middle section of the dumbbell is 5cm, and the diameter of the middle section is 1cm. Stretch each cylindrical dumbbell sample by hand and measure the stretching length with a long ruler. Keep the stretching rate consistent for each stretching test. Record the stretching length of each cylindrical dumbbell sample when it breaks, and then calculate the ratio of the stretching length to the corresponding initial length to obtain the stretching ratio. Here, the stretching length and the initial length both refer to the length of the middle section of the dumbbell sample. It should be noted that plugging gel DA8 is a viscous liquid before and after aging and cannot be gelled for subsequent testing. Therefore, only the experimental data of plugging gels A1-A3 and DA1-DA7 are listed in Table 1.

[0096] Table 1. Determination of shear toughness of plugging gel

[0097]

[0098] As can be seen from Table 1, the plugging gel prepared using the active polymer microgel provided by this invention as a crosslinking agent exhibits excellent shear toughness. After aging at 160℃ for 24 hours, it only fractured after being manually stretched more than 7.5 times, demonstrating good high-temperature stability and ensuring the sealing effect on deep, high-temperature leaking formations. This indicates that the active polymer microgel provided by this invention has strong crosslinking ability as a crosslinking agent, resulting in better high-temperature resistance, better toughness, and a more stable structure after the plugging gel is formed. This is beneficial for improving the sealing performance of the plugging gel on leaking formations at high temperatures.

[0099] Furthermore, it can be seen that the shear toughness of the plugging gels prepared using the organoaluminum zirconium crosslinking agent, crosslinking agent diethylenetriamine, and crosslinking agent N,N'-methylenebisacrylamide provided in Comparative Examples 1-3 is significantly worse than that of the plugging gels prepared using the active polymer microgels prepared in Examples 1-3 as crosslinking agents. The shear toughness is shorter and the elongation ratio is lower. Among them, the plugging gel DA2 prepared using diethylenetriamine as a crosslinking agent in Comparative Example 2 fractured after being manually stretched no more than 4 times after aging at 160°C for 24 hours, exhibiting the worst shear toughness. This indicates that commercially available organoaluminum zirconium crosslinking agents, crosslinking agents diethylenetriamine, and crosslinking agents N,N'-methylenebisacrylamide are not suitable as crosslinking agents for plugging gels and for use in plugging operations in deep, high-temperature, and leaky formations.

[0100] Secondly, it can be observed that the plugging gels DA4-DA7, prepared by using the active polymer microgels DG1-DG4 (with modified synthesis conditions compared to Example 1) from Comparative Examples 4-7 as crosslinking agents, showed a significant decrease in shear toughness compared to the active polymer microgel A1. Furthermore, the plugging gel DA8, prepared by using the active polymer microgel DG5 (obtained through reverse emulsion polymerization) from Comparative Example 8 as a crosslinking agent, failed to gel and remained in a viscous liquid state after aging at 160°C for 24 hours, making it impossible to prepare columnar dumbbell test samples for tensile testing. This demonstrates that only the process provided by this invention can successfully prepare active polymer microgels with effective crosslinking properties for use as plugging gels.

[0101] Test Example 3 - Determination of the sealing performance of the plugging gel crack

[0102] Here, the HB-1 type high temperature and high pressure fracture core flow device was used to test the sealing performance of the plugging gels A1-A3 and DA1-DA7 provided by the preparation examples 1-3 and the comparative preparation examples 1-7 under high temperature conditions on the fractures (among which DA8 obtained by the comparative preparation example 8 is a viscous liquid and cannot be used for plugging). The specific conditions and operation steps are as follows.

[0103] i. Fractured core and fracture information in the HB-1 type high temperature and high pressure fractured core flow device

[0104] In the HB-1 type high temperature and high pressure fractured core flow device, the fractured core has a diameter of 3.8 cm and a length of 10 cm. The uniform fracture runs through the core and has a width of 5 mm.

[0105] ii. Place the fractured core in the core holder and apply ring pressure to 3 MPa. Add solution A prepared in (1) and initiator solution B prepared in (2) of Preparation Example 1 to the two intermediate containers and seal them. Use a high-displacement horizontal flow pump to inject water into the intermediate containers through a six-way valve, pushing the pistons in the two intermediate containers upward, so that solution A and initiator solution B enter the fractured core in the core holder. Control the injected mass of initiator solution B to be 5 wt% of the injected mass of solution A. After injection, The temperature was set at 60℃ and left to stand for 6 hours to allow it to fully gel and solidify, forming plugging gel A1. The temperature was then raised to 160℃ to simulate the effect of high formation temperature on the plugging layer. After heating at 160℃ for 3 hours, a large-displacement horizontal flow pump was used to inject water into the core holder through a six-way valve. The injection pressure was controlled to increase uniformly from 1MPa. Every time the pressure increased by 1MPa, it was observed whether liquid flowed out from the outlet end of the fracture core. The injection pressure when liquid flowed out from the outlet end of the fracture core was recorded, which is the maximum pressure bearing capacity of plugging gel A1 to seal a 5mm wide fracture.

[0106] Following the method in section ii, sealing experiments were conducted on 5mm wide cracks using sealing gels A2, A3, and DA1-DA7, and the maximum pressure-bearing capacity of each sealing gel for sealing 5mm wide cracks was measured. For example, when testing sealing gel A2, solutions A and B prepared in preparation examples (1) and (2) of section ii were used, and the experiments on other sealing gels were conducted in the same manner.

[0107] The experimental results are shown in Table 2.

[0108] Table 2. Evaluation of the plugging performance of the plugging gel

[0109]

[0110] As shown in Table 2, the plugging gel prepared using the active polymer microgel provided by this invention as a crosslinking agent successfully sealed a 5mm crack at a high temperature of 160℃, with a sealing pressure resistance exceeding 7MPa, meeting the plugging requirements of deep, high-temperature leaking formations. This also demonstrates that the active polymer microgel provided by this invention, as a crosslinking agent for the plugging gel, enables rapid and effective crosslinking. Under the action of the active polymer microgel, the plugging gel can quickly react and crosslink after entering the target leaking layer, and after curing into a gel, it can effectively and firmly seal the leaking layer at a high temperature of not less than 160℃. The plugging gels DA1-DA7 all exhibited dripping leakage and failed to seal at different stages during the process of increasing the injection pressure from 1 MPa to 7 MPa. Some of the plugging gels even showed relatively serious linear leakage. Specifically, the plugging pressure resistance of plugging gels DA1-DA3 using conventional crosslinking agents did not exceed 4 MPa, and dripping occurred at injection pressures of 4 MPa or 5 MPa, resulting in sealing failure. When the injection pressure reached 7 MPa, plugging gel DA2 showed serious linear leakage. The plugging pressure resistance of plugging gels DA4-DA7 prepared using active polymer microgels DG1-DG4 prepared by modifying the preparation process of Example 1 as crosslinking agents was within 3-5 MPa, which was lower than that of plugging gel A1 prepared in Example 1. Furthermore, plugging gel DA6 showed linear leakage when the injection pressure reached 6 MPa. The experimental results of the above-mentioned plugging gels DA1-DA7 demonstrate that the existing conventional crosslinking agents have poor crosslinking performance and cannot maintain a stable and effective crosslinking state in the plugging gel under high temperature conditions. Furthermore, changing the preparation process provided by this invention, such as changing the type of monomer, missing raw materials (including but not limited to not adding chain extenders or missing initiator components), changing the mass relationship between raw materials, or the polymerization method, will result in a decrease in the crosslinking performance of the prepared plugging gel. This leads to a decrease in the shear toughness and sealing performance at high temperatures, which fails to meet the technical requirements of crosslinking agents for plugging gels in deep high-temperature leak layers.

[0111] While the present invention has been described with reference to specific embodiments, those skilled in the art will understand that various changes can be made without departing from the true spirit and scope of the invention. Furthermore, numerous modifications can be made to the subject, spirit, and scope of the invention to suit specific situations, materials, material compositions, and methods. All such modifications are included within the scope of the claims of the present invention.

Claims

1. An active polymer microgel, which is a polymeric product obtained by emulsion polymerization using N,N-dimethylacrylamide, hydroxymethylamide compounds, methacrylate compounds and emulsifiers as raw materials, under the action of chain extenders and initiators.

2. The active polymer microgel according to claim 1, characterized in that, The molecular weight of the active polymer microgel is 500,000 to 5,000,000.

3. The active polymer microgel according to claim 1 or 2, characterized in that, The mass ratio of the N,N-dimethylacrylamide, hydroxymethylamide compound, and methacrylate compound is (25-30):1:(5-8); and / or The total mass of the N,N-dimethylacrylamide, hydroxymethylamide, and methacrylate compounds is 100%, the mass of the emulsifier is 2.50-6.00 wt%, the mass of the chain extender is 0.10-0.60 wt%, and the mass of the initiator is 0.25-0.90 wt%.

4. The active polymer microgel according to any one of claims 1 to 3, characterized in that, The hydroxymethylamide compounds include at least one of N-hydroxymethylacetamide, N-hydroxymethylacrylamide, and N-hydroxymethylbenzamide; and / or The methacrylate compounds include at least one of methyl methacrylate, butyl methacrylate, and lauryl methacrylate; and / or The emulsifier is selected from at least one of Span-80, Tween-80, Span-60, Tween-60 and OP-10; and / or The chain extender is ethylenediaminetetraacetic acid; and / or The initiator is a mixture of potassium persulfate and sodium bisulfite.

5. The active polymer microgel according to claim 4, characterized in that, The emulsifier has an HLB value of 7-11; and / or In the initiator, the mass ratio of potassium persulfate to sodium bisulfite is 3:

1.

6. A method for preparing the active polymer microgel as described in any one of claims 1 to 5, comprising the following steps: Step 1) Mix the N,N-dimethylacrylamide, hydroxymethylamide compound, emulsifier and water to obtain an aqueous phase; Step 2) Using the methacrylate compound as the oil phase, drop it into the aqueous phase to obtain an oil-in-water emulsion; Step 3) The oil-in-water emulsion is subjected to emulsion polymerization under the action of the chain extender and initiator to obtain the active polymer microgel.

7. The method according to claim 6, characterized in that, The total mass concentration of the N,N-dimethylacrylamide, hydroxymethylamide compounds, methacrylate compounds, and emulsifier, taken as 100% by weight, is 35.50-36.50 wt%; and / or The mass ratio of the N,N-dimethylacrylamide, hydroxymethylamide compound, and methacrylate compound is (25-30):1:(5-8); and / or The total mass of the N,N-dimethylacrylamide, hydroxymethylamide, and methacrylate compounds is 100%, the mass of the emulsifier is 2.50-6.00 wt%, the mass of the chain extender is 0.10-0.60 wt%, and the mass of the initiator is 0.25-0.90 wt%.

8. The method according to claim 6 or 7, characterized in that, In step 3), the oil-in-water emulsion is first deoxygenated and heated, and then the chain extender and initiator are added to carry out the emulsion polymerization reaction.

9. The method according to any one of claims 6 to 8, characterized in that, The emulsion polymerization reaction is carried out at a temperature of 50°C and / or for a duration of 5-8 hours.

10. The use of the active polymer microgel according to any one of claims 1 to 5 or the active polymer microgel prepared by the method according to any one of claims 6 to 9 as a crosslinking agent, especially in the preparation of plugging gels.

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