Water-activated self-hardening gel system as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of oil and gas engineering, and particularly relates to a water-activated self-hardening gel system as well as a preparation method and application thereof. The water-activated self-hardening gel system provided by the invention comprises the following components in parts by weight: 20-100 parts of oily epoxy resin; 0.1 to 5 parts of a tackifier; 1-30 parts of a diluent; 0.1 to 45 parts of a latent curing agent; 0-22 parts of magnesium oxide, but not 0 part; and 0.5 to 18 parts of monopotassium phosphate. The water-activated self-hardening gel system is good in flowability, easy to pump and capable of quickly entering a leakage formation; the system is activated when meeting water, rapidly forms a fluid with a certain viscosity, and can be self-crosslinked and cured, so that slurry loses fluidity, and residence of the slurry in leak fluid is facilitated; the water-activated self-hardening gel system does not need to be fully mixed with water, the gel strength is rapidly developed as long as the water-activated self-hardening gel system is in contact with the water, the body strength is high after curing, and the plugging effect on abnormal water outlet stratums is remarkable.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas engineering, and in particular relates to a water-activated self-hardening gel system and a preparation method and application thereof. Background Art

[0002] Well leakage refers to the situation in which the working fluid (drilling fluid, workover fluid, cementing slurry, etc.) in the well leaks into the formation due to drilling, well repair and other construction in the process of oil or natural gas exploration and development. With the continuous deepening of oil and gas exploration, the formation is complex and changeable, and the number of malignant, cavernous and abnormally water-producing formations encountered increases. The problem of leakage will not only increase the drilling cost, but also may cause well wall instability, collapse, and even dangerous accidents such as blowouts in severe cases. At present, the commonly used plugging methods are ordinary bridge plugging and cement slurry plugging. However, due to formation water or cave accumulation, cement slurry is easily replaced with formation water or diluted by formation water before solidification and cannot solidify, resulting in plugging failure. Therefore, many scholars have conducted some research on polymer gel plugging technology. Chinese patent CN106349113A discloses a hydrophobic monomer and a hydrogel for drilling plugging based on the monomer. The hydrogel uses the association effect between hydrophobic groups to form hydrophobic association micro-regions, acting as physical cross-linking points in the three-dimensional network structure, with strong cohesive force, and is retained in the leaking layer to form a certain viscosity "segment plug". The hydrogel is not easily diluted by water after gelation. Chinese patent CN105567190A discloses a gel plugging agent for oil and gas field drilling plugging operations and its preparation method, which adopts aqueous solution polymerization, has the advantages of strong water absorption and expansion ability, and contains a variety of functional groups that can form mechanical interactions with the leaking layer to improve the retention capacity of the plugging material in the leaking layer.

[0003] Although the above-mentioned polymer gel plugging technology has achieved certain results, it is not easy to control the gelling time, pumping time and gelling time of these plugging technologies. If the gelling time is too long, the gel cannot be effectively solidified, the pressure bearing capacity cannot meet the requirements, and the re-leakage phenomenon occurs from time to time, resulting in the failure of the plugging operation. In addition, it was found through analysis that abnormal water-producing formations have large instantaneous water inflow or hidden rivers, which usually occur when the lower or underlying formations are restricted by the water level. There is currently little research on drilling plugging for abnormal water-producing formations. Traditional polymer gel plugging technology cannot fundamentally solve the serious well leakage problem in abnormal water-producing formations, which brings great challenges to drilling operations. Summary of the invention

[0004] The purpose of the present invention is to provide a water-activated self-hardening gel system and a preparation method and application thereof. The water-activated self-hardening gel system provided by the present invention has good fluidity and is easy to pump, and can quickly enter the leaking formation; and the system is activated when it encounters water, and quickly forms a solid body with high compressive strength, and has a significant effect on plugging abnormal water-producing formations.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a water-activated self-hardening gel system, comprising the following components in parts by weight:

[0007] 20-100 parts of oily epoxy resin; 0.1-5 parts of tackifier; 1-30 parts of diluent; 0.1-45 parts of latent curing agent; 0-22 parts of magnesium oxide (not 0 parts); 0.5-18 parts of potassium dihydrogen phosphate.

[0008] Preferably, the mass ratio of the oily epoxy resin, the diluent and the latent curing agent is (6-8):(2-4):1.

[0009] Preferably, the oily epoxy resin includes one or more of phenyl epoxy resin, tyrosine epoxy resin, glycidyl ester epoxy resin and glycidyl amine epoxy resin.

[0010] Preferably, the diluent includes one or more of ethylene glycol diglycidyl ether with diepoxy groups, o-cresyl glycidyl ether, 1,6-hexanediol diacrylate, β-hydroxyethyl methacrylate, glycerol and diethylene glycol.

[0011] Preferably, the latent curing agent includes one or more of triethylenetetramine, diaminodiphenylmethane, dicyandiamide compounds, aromatic diamines and boron trifluoride-amine complexes.

[0012] Preferably, the magnesium oxide is obtained by thermal decomposition of a magnesium-containing raw material; the magnesium-containing raw material includes magnesite and / or dolomite; and the thermal decomposition temperature is 600-800°C.

[0013] Preferably, the potassium dihydrogen phosphate is obtained by chemical reaction of phosphorus pentoxide and potassium oxide; the mass ratio of phosphorus pentoxide to potassium oxide is (1-2):(1-3).

[0014] Preferably, the tackifier includes one or more of hydrogenated rosin glycerol ester, rosin resin, polyisobutylene and petroleum resin emulsion.

[0015] The present invention provides a method for preparing the water-activated self-hardening gel system described in the above technical solution, comprising the following steps:

[0016] The components of the water-activated self-hardening gel system are mixed to obtain the water-activated self-hardening gel system.

[0017] The present invention provides the use of the water-activated self-hardening gel system described in the above technical solution or the water-activated self-hardening gel system prepared by the preparation method described in the above technical solution in plugging abnormal water-producing formations during drilling.

[0018] The present invention provides a water-activated self-hardening gel system, comprising the following components in mass fractions: 20 to 100 parts of oily epoxy resin; 0.1 to 5 parts of tackifier; 1 to 30 parts of diluent; 0.1 to 45 parts of latent curing agent; 0 to 22 parts of magnesium oxide, and not 0 parts; 0.5 to 18 parts of potassium dihydrogen phosphate. The water-activated self-hardening gel system provided by the present invention has good flowability and is easy to pump in anhydrous state by reasonably selecting the types of components in the system and the mass ratio of each component. It can quickly enter the leakage formation and is easy to construct; at the same time, on the one hand, the present invention can self-gel and solidify into a solidified body by mixing magnesium oxide and potassium dihydrogen phosphate in the above-mentioned mass ratio and reacting rapidly with water, and adding it to the oily epoxy resin mixed liquid can increase the strength of the gel solidified body. On the other hand, the latent curing agent is mixed with a certain amount of diluent and oily epoxy resin, and the activity is enhanced under moisture (water) conditions to form a paraffin-like self-crosslinking epoxy resin body, which reacts rapidly to achieve solidification. Therefore, the water-activated self-hardening gel system provided by the present invention is activated when it meets water, quickly forms a fluid with a certain viscosity, and quickly self-crosslinks and solidifies. It can be mixed with water in any proportion and can gel in 5 to 10 minutes, so that the slurry loses fluidity, which is conducive to its retention in the leaky fluid; and the water-activated self-hardening gel system does not need to be fully mixed with water. As long as the gel contacts water, it can form a solidified body with a compressive strength greater than 3.6 MPa within 3.5 hours. The gel strength develops rapidly, and the body strength is high after solidification, which can effectively realize the plugging of abnormal water-producing formations, thereby achieving a significant plugging effect for abnormal water-producing formations. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a morphology comparison diagram of the water-activated self-hardening gel system prepared in Example 3 of the present invention when in contact with different volumes of water without shearing;

[0020] Figure 2 This is a comparison chart of the fluidity of the water-activated self-hardening gel system prepared in Example 3 of the present invention after contacting with different volumes of water and then shearing for 5 minutes. DETAILED DESCRIPTION

[0021] The present invention provides a water-activated self-hardening gel system, comprising the following components in parts by weight:

[0022] 20-100 parts of oily epoxy resin; 0.1-5 parts of tackifier; 1-30 parts of diluent; 0.1-45 parts of latent curing agent; 0-22 parts of magnesium oxide (not 0 parts); 0.5-18 parts of potassium dihydrogen phosphate.

[0023] In the present invention, unless otherwise specified, all preparation raw materials / components are commercially available products well known to those skilled in the art.

[0024] In terms of parts by mass, the water-activated self-hardening gel system provided by the present invention includes 20 to 100 parts of an oily epoxy resin, preferably 30 to 80 parts, more preferably 40 to 65 parts, and specifically preferably 56 parts, 49 parts or 42 parts. In the present invention, the oily epoxy resin preferably includes one or more of phenyl epoxy resin, tyrosine epoxy resin, glycidyl ester epoxy resin and glycidyl amine epoxy resin, and more preferably at least three of phenyl epoxy resin, tyrosine epoxy resin, glycidyl ester epoxy resin and glycidyl amine epoxy resin. When the oily epoxy resin is preferably three of the above substances, the mass ratio of any of the above three resins is preferably (1 to 2): (1 to 3): (1 to 2), and specifically preferably 1:3:1. In a specific embodiment of the present invention, the oily epoxy resin is a mixture of phenyl epoxy resin, tyrosine epoxy resin and glycidyl amine epoxy resin in a mass ratio of 1:3:1. The oily epoxy resin is preferably a liquid resin, and the solid content of the oily epoxy resin is preferably 50-90%.

[0025] In the present invention, when the oily epoxy resin, latent curing agent and diluent are in contact with water, the oily epoxy resin containing two or more active epoxy groups undergoes a cross-linking reaction with the latent curing agent and diluent to form a three-dimensional cross-linked body similar to paraffin wax. At the same time, magnesium oxide and potassium dihydrogen phosphate in the system also help to promote the curing efficiency of the entire system.

[0026] Based on the mass fraction of the oily epoxy resin, the water-activated self-hardening gel system provided by the present invention includes 0.1 to 5 parts of a tackifier, preferably 0.5 to 4 parts, more preferably 0.8 to 3 parts, and specifically preferably 1 part. In the present invention, the tackifier preferably includes one or more of hydrogenated rosin glycerol ester, rosin resin, polyisobutylene and petroleum resin emulsion, more preferably at least two of hydrogenated rosin glycerol ester, rosin resin, polyisobutylene and petroleum resin emulsion. When the tackifier is preferably two of the above substances, the mass ratio of any two of the above substances is preferably 1: (2 to 4), more preferably 1: 3. In an embodiment of the present invention, the tackifier is a mixture of hydrogenated rosin glycerol ester and rosin resin in a mass ratio of 1: 3.

[0027] In the present invention, the thickener can significantly improve the viscosity and suspension stability of the system, so that it remains stable during the construction process and reduces sagging and sedimentation.

[0028] Based on the mass fraction of the oily epoxy resin, the water-activated self-hardening gel system provided by the present invention includes 1 to 30 parts of diluent, preferably 5 to 30 parts, more preferably 10 to 29 parts, and specifically preferably 14 parts, 21 parts or 28 parts. In the present invention, the diluent preferably includes one or more of ethylene glycol diglycidyl ether, o-cresyl glycidyl ether, 1,6-hexanediol diacrylate, β-hydroxyethyl methacrylate, glycerol and diethylene glycol, and more preferably at least two of ethylene glycol diglycidyl ether, o-cresyl glycidyl ether, 1,6-hexanediol diacrylate, β-hydroxyethyl methacrylate, glycerol and diethylene glycol. When the diluent is preferably two of the above substances, the mass ratio of any of the above substances is preferably 1: (2 to 5), and more preferably 1: 4. In a specific embodiment of the present invention, the diluent is a mixture of diepoxy ethylene glycol diglycidyl ether and diethylene glycol in a mass ratio of 1:4.

[0029] In the present invention, the diluent has good solubility and stability, and can adjust the viscosity of the system to improve the stability and uniformity of the system.

[0030] Based on the mass fraction of the oily epoxy resin, the water-activated self-hardening gel system provided by the present invention includes 0.1 to 45 parts of a latent curing agent, preferably 1 to 40 parts, more preferably 5 to 20 parts, further preferably 6 to 10 parts, and specifically preferably 7 parts. In the present invention, the latent curing agent preferably includes one or more of triethylenetetramine, diaminodiphenylmethane, dicyandiamide compounds, aromatic diamines and boron trifluoride-amine complexes, and more preferably at least three of triethylenetetramine, diaminodiphenylmethane, dicyandiamide compounds, aromatic diamines and boron trifluoride-amine complexes. When the latent curing agent is preferably three of the above substances, the mass ratio of any of the above three curing agents is preferably (1 to 2): (1 to 3): (1 to 2), and specifically preferably 1:3:2. In a specific embodiment of the present invention, the latent curing agent is a mixture of diaminodiphenylmethane, a dicyandiamide compound (obtained by reacting 4,4' diaminodiphenyl ether with dicyandiamide) and an aromatic diamine in a mass ratio of 1:3:2. In the present invention, the dicyandiamide compound is preferably a dicyandiamide derivative obtained by reacting 4,4' diaminodiphenyl ether (DDE) with dicyandiamide. The aromatic diamine preferably includes one or more of diaminodiphenyl sulfone, diaminodiphenylmethane and an aromatic diamine containing an ether / ester group (P-650), more preferably diaminodiphenyl sulfone and diaminodiphenylmethane. The mass ratio of the diaminodiphenyl sulfone to diaminodiphenylmethane is preferably 2:1 or 1:4. The boron trifluoride-amine complex preferably includes a boron trifluoride-monoethylamine complex.

[0031] In the present invention, the latent curing agent is mixed with a certain amount of diluent and oily epoxy resin. The activity of the latent curing agent is enhanced under moisture (water) conditions to form a paraffin-like self-crosslinking epoxy resin body, which reacts rapidly to achieve curing.

[0032] In the present invention, the mass ratio of the oily epoxy resin, the diluent and the latent curing agent is preferably (6-8):(2-4):1, and specifically preferably 8:2:1, 7:3:1 or 6:4:1.

[0033] Based on the mass fraction of the oily epoxy resin, the water-activated self-hardening gel system provided by the present invention includes 0 to 22 parts of magnesium oxide, and is not 0 parts, preferably 5 to 20 parts, more preferably 8 to 15 parts, and specifically preferably 10 parts. In the present invention, the magnesium oxide is preferably obtained by thermal decomposition of a magnesium-containing raw material; the magnesium-containing raw material preferably includes one or more of magnesite, dolomite (MgCO3·CaCO3) and seawater; the temperature of the thermal decomposition is preferably 600 to 800°C. The present invention preferably prepares magnesium oxide by thermal decomposition. The present invention destroys the aggregated structure of the polymorph of the magnesium-containing raw material by high-temperature calcination at 600 to 800°C, thereby obtaining magnesium oxide with good dispersibility.

[0034] Based on the mass fraction of the oily epoxy resin, the water-activated self-hardening gel system provided by the present invention includes 0.5 to 18 parts of potassium dihydrogen phosphate, preferably 1 to 16 parts, more preferably 5 to 15 parts, and particularly preferably 12 parts. In the present invention, the potassium dihydrogen phosphate is preferably obtained by chemical reaction of phosphorus pentoxide and potassium oxide; the mass ratio of phosphorus pentoxide to potassium oxide is preferably (1-2):(1-3), more preferably 1:3. In a specific embodiment of the present invention, the potassium dihydrogen phosphate is preferably obtained by reacting phosphorus pentoxide and potassium oxide in water.

[0035] The present invention provides a method for preparing the water-activated self-hardening gel system described in the above technical solution, comprising the following steps:

[0036] The components of the water-activated self-hardening gel system are mixed to obtain the water-activated self-hardening gel system.

[0037] In the present invention, the mixing is preferably carried out at room temperature. The mixing preferably includes the following steps: premixing the oily epoxy resin, diluent and latent curing agent to obtain a resin base liquid; first mixing the tackifier and the resin base liquid to obtain a first mixed liquid; second mixing the first mixed liquid, magnesium oxide and potassium dihydrogen phosphate. The first mixing is preferably carried out under ultrasonic conditions, the power of the ultrasound is preferably 5 to 500 W, and the frequency is preferably 20 to 100 KHz. The second mixing is preferably carried out under stirring conditions, and the stirring speed is preferably 3000 rpm.

[0038] The present invention provides the use of the water-activated self-hardening gel system described in the above technical solution or the water-activated self-hardening gel system prepared by the preparation method described in the above technical solution in plugging abnormal water-producing formations during drilling.

[0039] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0040] Example 1

[0041] The water-activated self-hardening gel system provided in this embodiment includes the following components in parts by weight, based on a total weight of 100 parts:

[0042] 1 part of tackifier, 56 parts of oily epoxy resin, 14 parts of diluent, 7 parts of latent curing agent, 10 parts of magnesium oxide, 12 parts of potassium dihydrogen phosphate, wherein the tackifier is a mixture of hydrogenated rosin glycerol ester and rosin resin in a mass ratio of 1:3, and the oily epoxy resin is a mixture of phenyl epoxy resin, tyrosine epoxy resin and glycidylamine epoxy resin in a mass ratio of 1:3:1 (phenyl epoxy resin, tyrosine epoxy resin and glycidylamine epoxy resin are mixed in a mass ratio of 1:3:1). The solid content of the three resins is 50-90%, the diluent is a mixture of ethylene glycol diglycidyl ether with a diepoxy group and diethylene glycol in a mass ratio of 1:4, and the latent curing agent is a mixture of diaminodiphenylmethane, a dicyandiamide compound (obtained by the reaction of 4,4' diaminodiphenyl ether and dicyandiamide) and an aromatic diamine (the aromatic diamine is a mixture of diaminodiphenyl sulfone and diaminodiphenylmethane in a mass ratio of 1:4) in a mass ratio of 1:3:2.

[0043] The preparation method of the water-activated self-hardening gel system provided in this embodiment includes:

[0044] First, the oily epoxy resin, diluent and latent curing agent are pre-mixed to obtain a resin base liquid for standby use, and then the tackifier is added to the pre-mixed resin base liquid by ultrasonic dispersion, and then magnesium oxide and potassium dihydrogen phosphate are added, and stirred to obtain a water-activated self-hardening gel system.

[0045] Example 2

[0046] The water-activated self-hardening gel system provided in this embodiment includes the following components in parts by weight, based on a total weight of 100 parts:

[0047] 1 part of tackifier, 49 parts of oily epoxy resin, 21 parts of diluent, 7 parts of latent curing agent, 10 parts of magnesium oxide, 12 parts of potassium dihydrogen phosphate, wherein the tackifier is a mixture of hydrogenated rosin glycerol ester and rosin resin in a mass ratio of 1:3, and the oily epoxy resin is a mixture of phenyl epoxy resin, tyrosine epoxy resin and glycidylamine epoxy resin in a mass ratio of 1:3:1 (phenyl epoxy resin, tyrosine epoxy resin and glycidylamine epoxy resin are mixed in a mass ratio of 1:3:1). The solid content of the three resins is 50-90%, the diluent is a mixture of ethylene glycol diglycidyl ether with a diepoxy group and diethylene glycol in a mass ratio of 1:4, and the latent curing agent is a mixture of diaminodiphenylmethane, a dicyandiamide compound (obtained by the reaction of 4,4' diaminodiphenyl ether and dicyandiamide) and an aromatic diamine (the aromatic diamine is a mixture of diaminodiphenyl sulfone and diaminodiphenylmethane in a mass ratio of 1:4) in a mass ratio of 1:3:2.

[0048] The preparation method of the water-activated self-hardening gel system provided in this embodiment includes:

[0049] First, the oily epoxy resin, diluent and latent curing agent are pre-mixed to obtain a resin base liquid for standby use, and then the tackifier is added to the pre-mixed resin base liquid by ultrasonic dispersion, and then magnesium oxide and potassium dihydrogen phosphate are added, and stirred to obtain a water-activated self-hardening gel system.

[0050] Example 3

[0051] The water-activated self-hardening gel system provided in this embodiment includes the following components in parts by weight, based on a total weight of 100 parts:

[0052] 1 part of tackifier, 42 parts of oily epoxy resin, 28 parts of diluent, 7 parts of latent curing agent, 10 parts of magnesium oxide, 12 parts of potassium dihydrogen phosphate, wherein the tackifier is a mixture of hydrogenated rosin glycerol ester and rosin resin in a mass ratio of 1:3, and the oily epoxy resin is a mixture of phenyl epoxy resin, tyrosine epoxy resin and glycidylamine epoxy resin in a mass ratio of 1:3:1 (phenyl epoxy resin, tyrosine epoxy resin and glycidylamine epoxy resin are mixed in a mass ratio of 1:3:1). The solid content of the three resins is 50-90%, the diluent is a mixture of ethylene glycol diglycidyl ether with a diepoxy group and diethylene glycol in a mass ratio of 1:4, and the latent curing agent is a mixture of diaminodiphenylmethane, a dicyandiamide compound (obtained by the reaction of 4,4' diaminodiphenyl ether and dicyandiamide) and an aromatic diamine (the aromatic diamine is a mixture of diaminodiphenyl sulfone and diaminodiphenylmethane in a mass ratio of 1:4) in a mass ratio of 1:3:2.

[0053] The preparation method of the water-activated self-hardening gel system provided in this embodiment includes:

[0054] First, the oily epoxy resin, diluent and latent curing agent are pre-mixed to obtain a resin base liquid for standby use, and then the tackifier is added to the pre-mixed resin base liquid by ultrasonic dispersion, and then magnesium oxide and potassium dihydrogen phosphate are added, and stirred to obtain a water-activated self-hardening gel system.

[0055] Test Case

[0056] (1) Rheological evaluation of water-activated self-hardening gel system

[0057] After the water-activated self-hardening gel system prepared in Examples 1 to 3 was cured at 80°C for 2 hours, its rheological parameters were measured using a six-speed rotational viscometer. The results are shown in Table 1. Φ600 to Φ3 in Table 1 represent the readings of the rotational viscometer at a rotation speed of 600 to 3 r / min. In this test, the flow index n and the consistency coefficient K are used to accurately represent the rheological properties of the cement slurry. Among them, The common gel cement slurry in Table 1 is gel purchased from the market, and the manufacturer is Hubei Jianghan Petroleum Technology Co., Ltd.

[0058] Table 1 Rheological parameters of the water-activated self-hardening gel system prepared in Examples 1 to 3

[0059] type Ф600 Ф300 Ф200 Ф100 Ф6 Ф3 n <![CDATA[K(Pa·s n )]]> Ordinary gel cement slurry - 170 115 80 15 7 0.6861 1.2037 Example 1 168 105 70 45 5 3 0.7713 0.4372 Example 2 140 100 62 40 4 2 0.8341 0.2814 Example 3 108 85 54 27 3 1 1.0108 0.0795

[0060] As can be seen from Table 1, the fluidity of the water-activated self-hardening gel system prepared in Examples 1 to 3 after curing at 80°C for 2 hours is significantly better than that of the ordinary gel cement slurry. The fluidity index n of the water-activated self-hardening gel system prepared in Examples 1 to 3 is greater than 0.5, and the consistency coefficient K is less than 0.7, indicating that the water-activated self-hardening gel system has excellent fluidity, and as the ratio of the oily epoxy resin to the diluent increases, the fluidity gradually improves.

[0061] (2) Evaluation of the water-activated self-hardening gel system’s fluidity when exposed to water

[0062] The water-activated self-hardening gel system prepared in Example 3 was added with a certain amount of water, and the volume ratio of water to the water-activated self-hardening gel system was 1:9, 2:8, 3:7, 4:6, 5:5 and 6:4, respectively. The fluidity of the water-activated self-hardening gel system after contact with different volumes of water and before and after shearing was observed, as shown in Table 2. Figure 1 and Figure 2 shown.

[0063] Table 2 Relationship between shear time and fluidity of the water-activated self-hardening gel system prepared in Example 3

[0064]

[0065] Figure 1The flow state of the water-activated self-hardening gel system prepared in Example 3 before shearing after contacting with water, Figure 2 The flow state of the water-activated self-hardening gel system prepared in Example 3 after being in contact with water for 5 minutes after shearing. It can be seen from Table 2 that when water is in contact with the water-activated self-hardening gel prepared in Example 3 at different proportions, the gel will solidify in a certain period of time as long as it is in contact with water when no shearing occurs, and the strength of the solidified body is not uniform. The water-activated self-hardening gel system was sheared with different volumes of water for 5 minutes and 7 minutes, and the gel quickly lost its fluidity. This shows that the water-activated self-hardening gel system prepared in Example 3 is miscible with water in different proportions, and can self-cross-link as long as it is in contact with water. It can gel in 5 to 10 minutes, making the slurry lose its fluidity, which is conducive to its retention in the leak. However, ordinary gel cement slurry cannot gel quickly when it comes into contact with water, which will result in the later curing strength not meeting the requirements, which is not conducive to the plugging of abnormal water-producing formations.

[0066] (3) Evaluation of curing strength of water-activated self-hardening gel system

[0067] A certain amount of water was added to the water-activated self-hardening gel system prepared in Example 3, and the gel was cured at 80° C. for 3.5 h. The gel curing strength was tested, as shown in Table 3:

[0068] Table 3 Strength evaluation of water-activated self-hardening gel system

[0069] Water: Volume ratio of water-activated self-hardening gel system Curing strength / MPa 1:9 6.7 2:8 6.3 3:7 5.8 4:6 5.0 5:5 4.3 6:4 3.7

[0070] From the experimental results in Table 3, it can be seen that the water-activated self-hardening gel system prepared in Example 3 is cured for 3.5 hours at 80°C, and the curing strength is greater than 3.6 MPa, indicating that the water-activated self-hardening gel system prepared in Example 3 has strong curing ability and fast strength development, and can improve the plugging ability of abnormal water-producing formations. In summary, it can be seen that the water-activated self-hardening gel system has a certain strength in different proportions, and as long as it contacts water and stands for 3 hours, a certain curing strength can be formed, which can maximize the formation of a curing barrier in the leak and meet the conditions for plugging abnormal water-producing formations.

[0071] Comparative Example 1

[0072] The preparation method is basically the same as that of Example 3, except that the water-activated self-hardening gel system provided in this comparative example does not include 10 parts of magnesium oxide, thereby obtaining a gel system without magnesium oxide.

[0073] According to the method of "(3) Evaluation of curing strength of water-activated self-hardening gel system" in the above test example, a certain amount of water was added to the gel system without magnesium oxide obtained in this comparative example, and the gel system was cured at 80° C. for 3.5 h, and the gel curing strength was tested, as shown in Table 4:

[0074] Table 4 Strength evaluation of gel system without magnesium oxide

[0075]

[0076]

[0077] It can be seen from Table 4 that the curing strength of the gel system without magnesium oxide is significantly reduced. This is because the lack of magnesium oxide prevents potassium dihydrogen phosphate from reacting with water to form a self-gelling solidification body, further increasing the strength of the gel solidified body.

[0078] It can be seen from the above embodiments that in order to overcome the shortcomings of existing plugging and plugging operations for abnormal water-producing formations and solve the problems of slow strength development and low curing strength of existing plugging materials, the present invention provides a water-activated self-hardening gel system for plugging abnormal water-producing formations. The water-activated self-hardening gel system has good fluidity and is easy to pump, and can quickly enter the leaking formation; the system is activated when it meets water, and quickly forms a fluid of a certain viscosity, and can self-crosslink and solidify, and can be mixed with water in any proportion and can gel in 5 to 10 minutes, so that the slurry loses fluidity, which is conducive to its retention in the leaking fluid; the water-activated self-hardening gel system does not need to be fully mixed with water. As long as the gel contacts water, it can form a solidified body with a compressive strength greater than 3.6 MPa within 3.5 hours. The gel strength develops rapidly, and the body strength is high after curing, and the plugging effect for abnormal water-producing formations is remarkable.

[0079] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A water-activated self-hardening gel system, characterized in that: The composition includes the following components in parts by weight: 20-100 parts of oily epoxy resin; 0.1-5 parts of tackifier; 1-30 parts of diluent; 0.1-45 parts of latent curing agent; 0-22 parts of magnesium oxide (not 0 parts); 0.5-18 parts of potassium dihydrogen phosphate.

2. The water-activated self-hardening gel system according to claim 1, characterized in that: The mass ratio of the oily epoxy resin, the diluent and the latent curing agent is (6-8):(2-4):

1.

3. The water-activated self-hardening gel system according to claim 1 or 2, characterized in that: The oily epoxy resin includes one or more of phenyl epoxy resin, tyrosine epoxy resin, glycidyl ester epoxy resin and glycidyl amine epoxy resin.

4. The water-activated self-hardening gel system according to claim 1 or 2, characterized in that: The diluent includes one or more of ethylene glycol diglycidyl ether with a diepoxy group, o-cresyl glycidyl ether, 1,6-hexanediol diacrylate, β-hydroxyethyl methacrylate, glycerol and diethylene glycol.

5. The water-activated self-hardening gel system according to claim 1 or 2, characterized in that: The latent curing agent includes one or more of triethylenetetramine, diaminodiphenylmethane, dicyandiamide compounds, aromatic diamines and boron trifluoride-amine complexes.

6. The water-activated self-hardening gel system according to claim 1, characterized in that: The magnesium oxide is obtained by thermal decomposition of a magnesium-containing raw material; the magnesium-containing raw material includes magnesite and / or dolomite; and the thermal decomposition temperature is 600-800°C.

7. The water-activated self-hardening gel system according to claim 1, characterized in that: The potassium dihydrogen phosphate is obtained by chemical reaction of phosphorus pentoxide and potassium oxide; the mass ratio of phosphorus pentoxide to potassium oxide is (1-2):(1-3).

8. The water-activated self-hardening gel system according to claim 1, characterized in that: The tackifier includes one or more of hydrogenated rosin glycerol ester, rosin resin, polyisobutylene and petroleum resin emulsion.

9. The method for preparing a water-activated self-hardening gel system according to any one of claims 1 to 8, characterized in that: The following steps are involved: The components of the water-activated self-hardening gel system are mixed to obtain the water-activated self-hardening gel system.

10. Use of the water-activated self-hardening gel system according to any one of claims 1 to 8 or the water-activated self-hardening gel system prepared by the preparation method according to claim 9 in plugging abnormal water-producing formations during drilling.

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