Temperature-sensitive gel plugging agent as well as preparation method and application thereof

Abstract

The invention provides a temperature-sensitive gel plugging agent as well as a preparation method and application thereof. The temperature-sensitive gel plugging agent is prepared from the following raw materials in specific parts by weight: hydroxyethyl acrylamide, a cross-linking agent, a stabilizer, an initiator, a chain terminator, a cosolvent and water. According to the temperature-sensitive gel plugging agent, the gelling time can be adjusted according to the temperature change, the water invasion resistance and the salt and gypsum invasion resistance are high after gelling, the high pressure-bearing strength of gel after gelling can be guaranteed, and the pressure-bearing capacity of a low-pressure stratum is greatly improved; meanwhile, degradation can be carried out through gel breaking according to needs, the plugging removal effect is achieved, the plugging agent is suitable for high-permeability, fissure and karst cave malignant leakage plugging, and oil, gas and water layers can be effectively separated to meet the site construction requirement.

Description

Technical Field

[0001] This invention belongs to the field of drilling fluid technology, specifically relating to a temperature-sensitive gel plugging agent, its preparation method, and its application. Background Technology

[0002] Loss in wells is a common downhole problem in drilling operations. Addressing it consumes significant drilling time, wastes drilling cycles and drilling fluid, and severe loss can lead to a series of complex situations such as stuck pipe, blowouts, and well collapse, even resulting in well abandonment and substantial economic losses, posing significant challenges to oil and gas resource exploration and development. Losses are prevalent in oilfield development, causing not only overflows and well collapses but also stuck pipe and other downhole accidents, severely impacting drilling safety and construction progress. Statistics show that loss in wells accounts for over 58% of complex downhole accidents in drilling, and this proportion increases as drilling proceeds to deeper and more complex areas.

[0003] Conventional well leakage repair methods are mainly divided into two categories: static plugging methods and methods for handling well leakage under special and complex conditions. Static plugging methods include plugging with granular plugging materials, plugging with granular plugging agents plus accelerator cement, MTC plugging method, and high-expansion network solidification plugging technology. Methods for handling well leakage under special and complex conditions include plugging of leakage from extra-large cavities and fractures, plugging of leakage from water layers, plugging of leakage from multi-pressure strata, plugging of well leakage in abnormal pressure zones, and leakage from the bottom layer of salt layers.

[0004] Leak-sealing materials are the hardware foundation of leak-sealing construction. Judging from the current situation of leak sealing, choosing unsuitable leak-sealing materials can lead to well leakage that cannot be resolved for a long time or repeated leakage. While drilling plugging agents have shown some effectiveness in field applications, their high price limits their widespread use. Gel plugging agents, on the other hand, suffer from weak mechanical properties and poor viscoelasticity. As a result, the main problems with current plugging drilling fluid technology are as follows: (1) Current plugging agents cannot stay in the lost layer, are easily diluted by water, are difficult to retain and accumulate near the entrance of the lost layer, and are difficult to block the leakage channels; (2) Current plugging agents are difficult to form a stable pressure-bearing sealing layer on the smooth fracture wall, resulting in low pressure bearing capacity; (3) Current drilling plugging technologies almost all use solid particles of different sizes, which are difficult to match with the lost pores and fractures. The plugging agents are difficult to retain in the lost pores and fractures, resulting in poor pressure bearing effect, low pressure bearing capacity and success rate, and easy to seal the gate; (4) Current gel plugging agents have weak resistance to water intrusion and salt gypsum intrusion, and the gel is greatly affected by temperature, making degradation difficult; (5) Current gel plugging agents cannot meet the requirements of new pressure-bearing plugging technologies for sealing different types of lost layers.

[0005] Therefore, in order to solve the above-mentioned technical problems, it is urgent to develop a temperature-sensitive gel sealing agent with high pressure resistance, strong resistance to salt plaster invasion, and suitable for sealing leaks in highly permeable, cracked, and karst caves. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a temperature-sensitive gel sealing agent, its preparation method, and its application. This temperature-sensitive gel sealing agent allows for adjustment of the gelation time through temperature changes, ensuring high compressive strength of the gel. It can also be degraded through gel breaking as needed to achieve unblocking effects. Furthermore, it possesses strong resistance to water and salt deposit intrusion, and high compressive strength, making it suitable for sealing leaks in highly permeable, fractured, and karst cavernous leaks. It can also separate oil, gas, and water layers to meet on-site construction requirements.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a temperature-sensitive gel sealing agent, wherein the raw materials of the temperature-sensitive gel sealing agent comprise the following components in parts by weight:

[0009]

[0010]

[0011] The temperature-sensitive gel sealing agent provided by this invention significantly improves the mechanical properties of the resulting gel by introducing covalent polymers and performing appropriate cross-linking, thus overcoming the shortcomings of supramolecular polymer gels, such as weak mechanical properties and poor viscoelasticity. Simultaneously, by introducing chain terminators to control the degree of polymerization, the resulting gel exhibits excellent temperature responsiveness, allowing for adjustment of gelation time based on temperature changes. It has a wide application range, usable from 60 to 160°C, and can be degraded through gel breaking to achieve unblocking effects.

[0012] When the temperature-sensitive gel plugging agent provided by this invention is applied to wellbore leakage during drilling operations, it can gel under the high temperature of the wellbore leakage. After gelation, it has strong resistance to water intrusion and salt deposits, and high pressure resistance. It can effectively solve the technical problems of existing plugging agents, such as not being able to stay in the leakage layer, being easily diluted by water, being difficult to retain and accumulate near the entrance of the leakage layer, being difficult to block the leakage channel, having low pressure resistance, weak resistance to water intrusion and salt deposits, and being greatly affected by temperature. At the same time, it creates a new pressure-bearing plugging technology that meets the needs of sealing different types of leakage layers, greatly improving the pressure resistance of low-pressure formations. It is suitable for plugging high-permeability, fractured, and karst cavernous leakage, and can separate oil, gas and water layers to meet the requirements of on-site construction.

[0013] In some preferred embodiments, the crosslinking agent includes N,N-dimethylbisacrylamide and / or dimethyldiallylammonium chloride.

[0014] In some preferred embodiments, the stabilizer comprises magnesium hydroxide fiber and / or sepiolite fiber.

[0015] In some preferred embodiments, the initiator includes azobisisobutyronitrile and / or potassium persulfate.

[0016] In some preferred embodiments, the chain terminator comprises calcium formate and / or sodium formate.

[0017] In some preferred embodiments, the co-solvent includes sodium sulfate and / or urea.

[0018] In some preferred embodiments, the water is distilled water.

[0019] In a second aspect, the present invention provides a method for preparing the temperature-sensitive gel sealing agent as described in the first aspect, the preparation method comprising the following steps:

[0020] (1) Add hydroxyethyl acrylamide, stabilizer and cosolvent to water and mix, then add crosslinking agent and mix to obtain a mixture;

[0021] (2) Add an initiator to the mixture obtained in step (1) to carry out a polymerization reaction, and then add a chain terminator to mix to obtain the thermosensitive gel plugging agent.

[0022] In some preferred embodiments, the polymerization reaction in step (2) is carried out at a temperature of 40 to 50°C, such as 40°C, 42°C, 44°C, 46°C, 48°C or 50°C.

[0023] In some preferred embodiments, the polymerization reaction time in step (2) is 0.5 to 1 hour, for example, 0.5 hours, 0.6 hours, 0.7 hours, 0.8 hours, 0.9 hours or 1 hour.

[0024] In some preferred embodiments, the mixing time in step (2) is 0.2 to 1 hour, for example, 0.2 hours, 0.3 hours, 0.4 hours, 0.5 hours, 0.6 hours, 0.7 hours, 0.8 hours, 0.9 hours, or 1 hour.

[0025] Thirdly, the present invention provides an application of the temperature-sensitive gel plugging agent as described in the first aspect in well leakage during drilling operations.

[0026] When applying the temperature-sensitive gel plugging agent provided by the present invention to drilling fluid, the amount of the temperature-sensitive gel plugging agent provided by the present invention can be 15% to 25% based on a water volume of 100 mL, such as 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, or 25%.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The raw materials of the thermosensitive gel plugging agent provided by this invention include specific weight parts of hydroxyethyl acrylamide, crosslinking agent, stabilizer, initiator, chain terminator, cosolvent, and water. The thermosensitive gel plugging agent can adjust the gelation time by temperature changes, and after gelation, it has strong resistance to water intrusion and salt paste intrusion. It can also ensure high pressure bearing strength of the gel, significantly improving the pressure bearing capacity of low-pressure formations. At the same time, it can be degraded by gel breaking as needed to achieve the effect of unblocking. It is suitable for plugging leaks in high-permeability, fractured, and karst cavernous areas, and can effectively separate oil, gas, and water layers to meet on-site construction requirements. Attached Figure Description

[0029] Figure 1 A process flow diagram for preparing the temperature-sensitive gel sealing agent provided by the present invention;

[0030] Figure 2 A photograph of the thermosensitive gel sealant provided in Example 1;

[0031] Figure 3 A photograph of the actual product of the thermosensitive gel sealing agent provided in Example 1, which was prepared into a sealing slurry with a concentration of 17 g / mL and stirred at room temperature for 20 min.

[0032] Figure 4 A photograph of the actual product after the thermosensitive gel sealing agent provided in Example 1 was prepared into a sealing slurry with a concentration of 17 g / mL and allowed to stand at 70°C for 4 hours;

[0033] Figure 5 A photograph of the actual product of the thermosensitive gel sealing agent provided in Example 1, which was prepared into a sealing slurry with a concentration of 17 g / mL and then allowed to stand at 70°C for 20 h.

[0034] Figure 6 A photograph of the actual product of the thermosensitive gel sealing agent provided in Example 1, which was prepared into a sealing slurry with a concentration of 20 g / mL and stirred at room temperature for 20 min.

[0035] Figure 7 A photograph of the actual product after the thermosensitive gel sealing agent provided in Example 1 was prepared into a sealing slurry with a concentration of 20 g / mL and allowed to stand at 70°C for 4 hours;

[0036] Figure 8 A photograph of the actual product of the thermosensitive gel sealing agent provided in Example 1, which was prepared into a sealing slurry with a concentration of 20 g / mL and then allowed to stand at 70°C for 20 h.

[0037] Figure 9 The image shows the actual product of the thermosensitive gel sealing agent provided in Example 2, which was mixed with water to make a sealing slurry with a concentration of 17 g / mL and stirred at room temperature for 20 min.

[0038] Figure 10The image shows the actual product of the thermosensitive gel sealing agent provided in Example 2, which was mixed with water to make a sealing slurry with a concentration of 17 g / mL and then aged at 140°C for 4 hours.

[0039] Figure 11 The image shows the actual product of the thermosensitive gel sealing agent provided in Example 2, which was mixed with water to make a sealing slurry with a concentration of 17 g / mL and then aged at 140°C for 14 hours.

[0040] Figure 12 The image shows the actual product of the thermosensitive gel plugging agent provided in Example 2, mixed with water and on-site well slurry to prepare a plugging slurry with a concentration of 17 g / mL, and stirred at room temperature for 20 minutes.

[0041] Figure 13 The image shows the actual product of the thermosensitive gel plugging agent provided in Example 2, which was mixed with water and field well slurry to prepare a plugging slurry with a concentration of 17 g / mL and aged at 140°C for 4 hours.

[0042] Figure 14 The image shows the actual product of the thermosensitive gel plugging agent provided in Example 2, which was mixed with water and field well slurry to prepare a plugging slurry with a concentration of 17 g / mL and aged at 140°C for 14 hours.

[0043] Figure 15 A physical image of the gel sealing agent provided for Comparative Example 1;

[0044] Figure 16 A photograph of the mixture of the gel sealant and tap water provided in Comparative Example 1, stirred at room temperature for 20 minutes.

[0045] Figure 17 A photograph of the mixture of the gel sealant provided in Comparative Example 1 and tap water after standing at 70°C for 4 hours. Detailed Implementation

[0046] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0047] Unless otherwise specified, the raw materials involved in the following specific embodiments are all conventional materials in the art and can be purchased from commercially available products.

[0048] Example 1

[0049] A temperature-sensitive gel sealing agent, the components and dosages of which are listed in Table 1:

[0050] Table 1

[0051]

[0052] The process flow diagram for preparing the temperature-sensitive gel sealing agent provided in this embodiment is as follows: Figure 1 As shown, the specific steps include the following:

[0053] (1) Add distilled water to the reaction vessel, turn on the stirrer, then add hydroxyethyl acrylamide, magnesium cellulose and sodium sulfate and mix them, then slowly add dimethyl diallyl ammonium chloride and stir evenly to obtain a mixture;

[0054] (2) Slowly add azobisisobutyronitrile to the mixture obtained in step (1), and polymerize at 45°C for 0.8 h. Then slowly add sodium formate and stir for 0.5 h to obtain a viscous liquid, which is the temperature-sensitive gel sealing agent, which can be discharged, packaged, tested and stored.

[0055] Rubber Evaluation:

[0056] Experimental scheme ①: Take 300mL of tap water, add 50g of the thermosensitive gel sealing agent provided in Example 1 to obtain a sealing slurry with a concentration of 17g / mL, stir it at low speed for 20min at room temperature and 200rpm, then put it in a water bath at 70℃, let it stand and observe its viscosity change.

[0057] Upon observation, the physical image of the temperature-sensitive gel sealing agent provided in Example 1 is shown below. Figure 2 As shown, the actual product of the thermosensitive gel sealing agent provided in Example 1, after being prepared into a sealing slurry with a concentration of 17 g / mL and stirred at room temperature for 20 minutes, is shown in the figure. Figure 3 As shown, the actual product image of the thermosensitive gel sealing agent provided in Example 1, after being prepared into a sealing slurry with a concentration of 17 g / mL and left to stand at 70°C for 4 hours, is shown below. Figure 4 As shown, and a physical image of the thermosensitive gel sealing agent provided in Example 1 after being prepared into a sealing slurry with a concentration of 17 g / mL and left to stand at 70°C for 20 hours, are also shown. Figure 5 As shown;

[0058] from Figures 2-5 It can be seen that the temperature-sensitive gel sealant provided in Example 1 has good fluidity before being mixed with tap water. After the temperature-sensitive gel sealant provided in Example 1 is prepared into a sealant with a concentration of 17 g / mL, it still has good fluidity after being stirred at room temperature for 20 min. After standing at 70℃ for 4 h, the sealant forms a gel. After standing at 70℃ for 20 h, the gel strength of the sealant is significantly enhanced.

[0059] Experimental scheme ②: Take 300mL of tap water, add 60g of the temperature-sensitive gel sealing agent provided in Example 1 to obtain a sealing slurry with a concentration of 20g / mL, stir it at low speed for 20min at room temperature and 200rpm, then put it in a water bath at 70℃, let it stand and observe the viscosity change.

[0060] The actual product image after the thermosensitive gel sealing agent provided in Example 1 was prepared into a sealing slurry with a concentration of 20 g / mL and stirred at room temperature for 20 minutes is shown below. Figure 6 As shown, the actual product image of the thermosensitive gel sealing agent provided in Example 1, after being prepared into a sealing slurry with a concentration of 20 g / mL and left to stand at 70°C for 4 hours, is shown below. Figure 7 As shown, and a physical image of the thermosensitive gel sealing agent provided in Example 1 after being prepared into a sealing slurry with a concentration of 20 g / mL and left to stand at 70°C for 20 hours, is also shown. Figure 8 As shown;

[0061] from Figures 6-8 It can be seen that after the thermosensitive gel sealing agent provided in Example 1 is prepared into a sealing slurry with a concentration of 20g / mL, it also has good fluidity after being stirred at room temperature for 20 minutes. After standing at 70℃ for 4 hours, the resulting sealing slurry forms a gel. Furthermore, after standing at 70℃ for 20 hours, the gel strength of the resulting sealing slurry is significantly enhanced.

[0062] In summary, the temperature-sensitive gel sealing agent provided in Example 1 has a temperature-sensitive gelling effect.

[0063] Example 2

[0064] A temperature-sensitive gel sealing agent, the components and dosages of which are listed in Table 2:

[0065] Table 2

[0066]

[0067] The preparation method of the temperature-sensitive gel sealing agent provided in this embodiment specifically includes the following steps:

[0068] (1) Add distilled water to the reaction vessel, turn on the stirrer, then add hydroxyethyl acrylamide, magnesium cellulose and sodium sulfate and mix them, then slowly add N,N-dimethylbisacrylamide and stir evenly to obtain a mixture;

[0069] (2) Slowly add azobisisobutyronitrile to the mixture obtained in step (1), and polymerize at 50°C for 0.5 h. Then slowly add sodium formate and stir for 0.5 h to obtain a viscous liquid, which is the thermosensitive gel sealing agent.

[0070] Rubber Evaluation:

[0071] Experimental scheme ①: Take 300mL of tap water, add 60g of the temperature-sensitive gel sealing agent provided in Example 2 to obtain a sealing slurry with a concentration of 20g / mL, stir it at low speed for 20min at room temperature and 200rpm, and then put it into an aging tank at 140℃ for aging treatment and observe the viscosity change.

[0072] The actual product image after the thermosensitive gel sealing agent provided in Example 2 was prepared into a sealing slurry with a concentration of 20 g / mL and stirred at room temperature for 20 minutes is shown below. Figure 9 As shown, the actual product image after the temperature-sensitive gel sealing agent provided in Example 2 was prepared into a sealing slurry with a concentration of 20 g / mL and aged at 140°C for 4 hours is shown. Figure 10 As shown, and the actual product image of the sealing slurry prepared with the temperature-sensitive gel sealing agent provided in Example 2 at a concentration of 20 g / mL after aging at 140°C for 14 hours, is also shown. Figure 11 As shown;

[0073] from Figures 9-11 It can be seen that the thermosensitive gel sealing agent provided in Example 2, when prepared into a sealing slurry with a concentration of 20 g / mL, has good fluidity after being stirred at room temperature for 20 min. After aging at 140℃ for 4 h, the sealing slurry forms a gel. After further aging at 140℃ for 14 h, the strength of the sealing slurry gel is significantly enhanced.

[0074] Experimental scheme ②: Take 300mL of the mixture (according to tap water: water-based field well slurry = 95:5), add 50g of the temperature-sensitive gel plugging agent provided in Example 2 to obtain a plugging slurry with a concentration of 17g / mL, stir it at low speed for 20min at room temperature and 200rpm, and then put it into an aging tank at 140℃ for aging treatment and observe the viscosity change.

[0075] The actual product of the thermosensitive gel sealing agent provided in Example 2, after being prepared into a sealing slurry with a concentration of 17 g / mL and stirred at room temperature for 20 minutes, is shown in the image below. Figure 12 As shown, the actual product image of the thermosensitive gel sealing agent provided in Example 2, after being prepared into a sealing slurry with a concentration of 17 g / mL and aged at 140°C for 4 hours, is shown below. Figure 13 As shown, and a physical image of the sealing slurry prepared with the temperature-sensitive gel sealing agent provided in Example 2 at a concentration of 17 g / mL after aging at 140°C for 14 hours, is also shown. Figure 14 As shown;

[0076] from Figures 12-14 It can be seen that the thermosensitive gel sealing agent provided in Example 2, when prepared into a sealing slurry with a concentration of 17 g / mL, also has good fluidity after being stirred at room temperature for 20 min. After aging at 140℃ for 4 h, the sealing slurry forms a gel, and after aging at 140℃ for 14 h, the gel strength of the sealing slurry is significantly enhanced.

[0077] In summary, the temperature-sensitive gel sealing agent provided in Example 2 also has a temperature-sensitive gelling effect.

[0078] Example 3

[0079] A temperature-sensitive gel sealing agent, the components and dosages of which are listed in Table 3:

[0080] Table 3

[0081]

[0082] The preparation method of the temperature-sensitive gel sealing agent provided in this embodiment specifically includes the following steps:

[0083] (1) Add distilled water to the reaction vessel, turn on the stirrer, then add hydroxyethyl acrylamide, sepiolite fiber and urea and mix them, then slowly add dimethyl diallyl ammonium chloride and stir evenly to obtain a mixture;

[0084] (2) Potassium persulfate is slowly added to the mixture obtained in step (1), and the polymerization reaction is carried out at 40°C for 1 hour. Then sodium formate is slowly added and stirred for 0.5 hours to obtain a viscous liquid, which is the temperature-sensitive gel sealing agent.

[0085] Example 4

[0086] A temperature-sensitive gel sealing agent, which differs from Example 1 in that calcium formate is used instead of sodium formate as the chain terminator, while the other substances, dosages and preparation methods are the same as in Example 1.

[0087] Example 5

[0088] A temperature-sensitive gel sealing agent, which differs from Example 1 in that the amount of sodium formate used is 1 part by weight, while the other substances, amounts and preparation methods are the same as in Example 1.

[0089] Example 6

[0090] A temperature-sensitive gel sealing agent differs from Example 1 in that the amount of sodium formate used is 3 parts by weight, while the other substances, amounts, and preparation methods are the same as in Example 1.

[0091] Comparative Example 1

[0092] A gel-based sealing agent, the components and dosages of which are listed in Table 4:

[0093] Table 4

[0094]

[0095] The preparation method of the gel sealing agent provided in this comparative example specifically includes the following steps:

[0096] (1) Add distilled water to the reaction vessel, turn on the stirrer, then add hydroxyethyl acrylamide, magnesium cellulose and sodium sulfate and mix them, then slowly add dimethyl diallyl ammonium chloride and stir evenly to obtain a mixture;

[0097] (2) Slowly add azobisisobutyronitrile to the mixture obtained in step (1) and polymerize it at 45°C for 3 hours to obtain the gel sealing agent.

[0098] Rubber Evaluation:

[0099] (1) The actual image of the gel sealing agent obtained in Comparative Example 1 is shown below. Figure 15 As shown;

[0100] from Figure 15 It can be seen that the gel sealing agent obtained in Comparative Example 1 has completely gelled and does not have fluidity.

[0101] (2) Take 300 mL of tap water, add 60 g of the gel sealing agent provided in Comparative Example 1, stir it at room temperature and 200 rpm for 20 min, then put it in a water bath at 70 ℃, let it stand and observe the viscosity change.

[0102] The actual image of the mixture formed by the gel sealant and tap water provided in Comparative Example 1 after stirring at room temperature for 20 minutes is shown below. Figure 16 As shown, the actual product image of the mixture of the gel sealant provided in Comparative Example 1 and tap water after standing at 70°C for 4 hours is shown. Figure 17 As shown;

[0103] from Figure 16 and Figure 17 It can be seen that the gel sealant provided in Comparative Example 1 has already gelled and cannot be evenly dispersed in tap water, so it cannot be used.

[0104] Comparative Example 2

[0105] A gel sealing agent, which differs from the thermosensitive gel sealing agent provided in Example 1 only in that the crosslinking agent dimethyl diallyl ammonium chloride is not added, while the other substances, dosages and preparation methods are the same as in Example 1.

[0106] Performance testing:

[0107] (1) Gel formation time: Measure 300mL of distilled water into a high-speed stirring cup, and slowly add 75.0g of sealing agent while stirring on a high-speed stirrer with a speed of 3000r / min for 30min to obtain the test slurry;

[0108] Pour the obtained test slurry into a 500mL beaker, place the beaker in an 80℃ water bath, and observe and record the results every 15 minutes until the slurry loses its fluidity. The recorded time is the gelation time.

[0109] (2) Pressure bearing capacity: Measure 300 mL of distilled water into a high-speed stirring cup, and slowly add 75.0 g of sealing agent while stirring on a high-speed stirrer with a speed of 3000 r / min for 30 min to obtain the test slurry;

[0110] Place a 2mm sealing plate at the bottom of the cup of the high-temperature and high-pressure leak sealing instrument, seal the bottom cover, tighten the set screw, close the lower valve rod, pour the test slurry into the cup to the scale line, seal the top cover, tighten the set screw, connect the air line, pressurize to 0.7MPa, open the lower valve rod, let 2mL flow out, and close the lower valve rod; according to the high-temperature and high-pressure dehydration operation procedure, raise the temperature to 140℃, continue aging for 8 hours, open the lower valve rod, pressurize at 0.5MPa for 2 minutes, and record the pressure until the filtrate appears.

[0111] (3) Anti-backflow capability: After the experiment in (2) above, the cup was cooled, the pressure was released, and it was placed upside down in the heating jacket. The gas line was connected and pressurized. The upper and lower valves were opened and the pressure was increased at 0.5 MPa for 2 minutes. The pressure was recorded until the filtrate appeared.

[0112] (4) Viscoelasticity: After aging at 140℃ for 16h, the gel sample was tested for changes in storage modulus (G') and dissipation modulus (G”) at different frequencies using a HAKKE rheometer to examine its viscoelastic characteristics.

[0113] (5) Breakage rate: Measure 200mL of 20% breaking solution and pour it into the aging tank. Weigh 100g of gel aged at 140℃ for 72h and pour it into the tank. Place the aging tank in a 140℃ oven and let it stand for 24h, 48h, and 72h. Observe the state of the gel after opening the tank. Weigh the unbroken gel pieces and calculate the breakage rate according to the following formula:

[0114] P = (M-M1) / M × 100%;

[0115] Where P is the gel breaking rate (%), M is the gel mass (g), and M1 is the mass of the remaining gel block (g).

[0116] The gelation time, pressure bearing capacity, anti-backflow capacity, viscoelasticity and breakage rate of the gel sealing agents provided in Examples 1-6 and Comparative Examples 1-2 were tested according to the above test methods. The test results are shown in Table 5.

[0117] Table 5

[0118]

[0119] According to the data in Table 5:

[0120] The temperature-sensitive gel sealing agents provided in Examples 1-6 have suitable gelation time, high pressure resistance and anti-backflow ability, and low breakage rate after being placed at 140°C for 72 hours; while the gel sealing agent provided in Comparative Example 2 has a longer gelation time and lower pressure resistance and anti-backflow ability because no crosslinking agent was added.

[0121] The applicant declares that this invention illustrates a temperature-sensitive gel sealing agent, its preparation method, and its application through the above embodiments. However, this invention is not limited to the above process steps, meaning that this invention does not necessarily rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of the raw materials used in this invention, additions of auxiliary components, and selection of specific methods all fall within the protection and disclosure scope of this invention.

Claims

1. A temperature-sensitive gel sealing agent, characterized in that, The raw materials of the temperature-sensitive gel sealing agent include the following components in parts by weight:

2. The temperature-sensitive gel sealing agent according to claim 1, characterized in that, The crosslinking agent includes N,N-dimethylbisacrylamide and / or dimethyldiallylammonium chloride.

3. The temperature-sensitive gel sealing agent according to claim 1 or 2, characterized in that, The stabilizer includes magnesium hydroxide fiber and / or sepiolite fiber.

4. The temperature-sensitive gel sealing agent according to any one of claims 1 to 3, characterized in that, The initiator includes azobisisobutyronitrile and / or potassium persulfate.

5. The thermosensitive gel sealant according to any one of claims 1 to 4, characterized in that, The chain terminator includes calcium formate and / or sodium formate.

6. The thermosensitive gel sealant according to any one of claims 1 to 5, characterized in that, The co-solvent includes sodium sulfate and / or urea.

7. The thermosensitive gel sealant according to any one of claims 1 to 6, characterized in that, The water is distilled water.

8. A method for preparing a thermosensitive gel sealing agent as described in any one of claims 1 to 7, characterized in that, The preparation method includes the following steps: (1) Add hydroxyethyl acrylamide, stabilizer and cosolvent to water and mix, then add crosslinking agent and mix to obtain a mixture; (2) Add an initiator to the mixture obtained in step (1) to carry out a polymerization reaction, and then add a chain terminator to mix to obtain the thermosensitive gel plugging agent.

9. The preparation method according to claim 8, characterized in that, The polymerization reaction in step (2) is carried out at a temperature of 40–50 °C. Preferably, the polymerization reaction in step (2) takes 0.5 to 1 hour; Preferably, the mixing time in step (2) is 0.2 to 1 hour.

10. The application of a temperature-sensitive gel plugging agent as described in any one of claims 1 to 7 in well leakage during drilling operations.

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