Temperature-sensitive anti-collapse plugging agent, preparation method thereof and water-based drilling fluid

Abstract

The invention provides a temperature-sensitive anti-sloughing plugging agent and a preparation method thereof and a water-based drilling fluid, the preparation method of the temperature-sensitive anti-sloughing plugging agent comprises the following steps: carrying out polymerization reaction on 2-acrylamido-2-methylpropanesulfonic acid, oleic acid, n-butyl acrylate and tetraphenylethylene under the action of an initiator by adopting a soap-free emulsion polymerization method to obtain the temperature-sensitive anti-sloughing plugging agent. The temperature-sensitive anti-collapse plugging agent is obtained. The water-based drilling fluid obtained based on the temperature-sensitive anti-sloughing plugging agent prepared by the invention can be used for enhancing plugging and sloughing prevention of high-temperature micro-crack stratums and improving the well wall stability of the high-temperature crack stratums.

Description

Technical Field

[0001] This invention belongs to the field of oilfield development and relates to a temperature-sensitive anti-collapse sealing agent, its preparation method, and a water-based drilling fluid. Background Technology

[0002] As drilling engineering has now entered the development stage of ultra-deep and complex wells, downhole temperatures can reach over 200°C. Therefore, anti-collapse plugging agents used in water-based drilling fluids must possess temperature resistance, which is the most important performance characteristic of anti-collapse plugging agents.

[0003] Currently, research on anti-collapse plugging agents for water-based drilling fluids is extensive, but high-temperature resistant anti-collapse plugging agents are relatively lacking. In high-temperature environments, most non-mineral plugging agents are prone to carbonization and chain breakage, reducing their effectiveness. Therefore, it is necessary to develop a temperature-sensitive anti-collapse plugging agent to meet the technical requirements of high-temperature anti-collapse plugging at different wellbores, achieving the goal of adapting to different formation temperatures and efficiently plugging nanofissures in formations. Summary of the Invention

[0004] The purpose of this invention is to provide a temperature-sensitive anti-collapse plugging agent, its preparation method, and a water-based drilling fluid, which are used to strengthen the plugging and anti-collapse of high-temperature micro-fractured formations and improve the wellbore stability of high-temperature fractured formations.

[0005] This invention is achieved through the following technical solution:

[0006] A method for preparing a temperature-sensitive anti-collapse plugging agent involves using soap-free emulsion polymerization of 2-acrylamido-2-methylpropanesulfonic acid and oleic acid with n-butyl acrylate and tetraphenylethylene under the action of an initiator to obtain the temperature-sensitive anti-collapse plugging agent.

[0007] Preferably, the preparation method of the temperature-sensitive anti-collapse sealing agent of the present invention specifically includes:

[0008] 2-Acrylamido-2-methylpropanesulfonic acid and oleic acid were dissolved in water, and the pH was adjusted to 5-7. Under stirring, n-butyl acrylate and tetraphenylethylene were added, the temperature was raised to the reaction temperature, an initiator was added, and polymerization was carried out under a protective atmosphere to obtain a thermosensitive anti-collapse sealing agent.

[0009] Preferably, in the preparation method of the temperature-sensitive anti-collapse sealing agent, the reaction temperature is 55-75℃ and the reaction time is 5.5-7.5h.

[0010] Preferably, in the preparation method of the temperature-sensitive anti-collapse sealing agent, the mass ratio of oleic acid, 2-acrylamido-2-methylpropanesulfonic acid, tetraphenylethylene, n-butyl acrylate and initiator is (0.0576-0.0976):(0.0476-0.0876):(0.078-0.136):(0.0188-0.0768):(0.007-0.019).

[0011] This invention provides a temperature-sensitive anti-collapse sealing agent prepared by the method described above.

[0012] This invention provides a water-based drilling fluid, including the temperature-sensitive anti-collapse plugging agent as described above.

[0013] Preferably, the water-based drilling fluid comprises, by weight, 100 parts water, 2-8 parts bentonite, 0.1-0.4 parts sodium carbonate, 2-6 parts viscosity reducer, 2-8 parts filtration loss reducer, 3-7 parts inhibitor, 2-7 parts alkalinity adjuster, 18-34 parts weighting agent, and 0.5-4.5 parts temperature-sensitive anti-collapse and plugging agent.

[0014] Preferably, the bentonite is one of calcium-based bentonite, calcium-sodium-based bentonite, and calcium-magnesium-based bentonite;

[0015] And / or, the viscosity reducer is one of tannin alkali solution, iron-chromium lignin sulfonate, iron-chromium salt and tannin.

[0016] Preferably, the filtration loss reducing agent is one of sodium nitrohumate, potassium humate, chromium humic acid, and hydroxypropyl starch;

[0017] And / or, the inhibitor is one of polyacrylamide, potassium chloride, potassium silicate, and polyamine.

[0018] Preferably, the alkalinity regulator is one of sodium hydroxide and calcium oxide;

[0019] And / or, the weighting agent is one of API barite, magnetite powder, manganese tetroxide, and calcium carbonate.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The preparation method of the anti-collapse plugging agent of this invention introduces n-butyl acrylate and tetraphenylethylene containing hydrophobic groups, and 2-acrylamido-2-methylpropanesulfonic acid and oleic acid containing hydrophilic groups. 2-acrylamido-2-methylpropanesulfonic acid and oleic acid are temperature-sensitive, giving the anti-collapse plugging agent temperature-sensitive properties. As the temperature rises, when the temperature exceeds the minimum co-solution temperature of the temperature-sensitive anti-collapse plugging agent, the hydrophilic groups in 2-acrylamido-2-methylpropanesulfonic acid and oleic acid break, and the surface of the anti-collapse plugging agent changes from hydrophilic to hydrophobic. When the temperature-sensitive anti-collapse plugging agent enters the fracture, it first bridges and fills the fracture, forming a tight-sealing layer with the fracture wall through hydrogen bonds. When the temperature is higher than the minimum co-solution temperature, the surface of the temperature-sensitive anti-collapse plugging agent changes to oleophilic, forming a hydration film on the rock surface, preventing the filtrate from hydrating the fracture wall, reducing rock fracture pressure, and thus improving the wellbore stability performance in high-temperature fractured formations. The oleic acid used in this invention is not only a temperature-sensitive material but also a high-performance phase change material. It can undergo a reversible solid-liquid transformation at a given temperature. This solid-to-liquid transition endows the anti-collapse plugging agent with heat storage properties. This property allows the drilling fluid to cool down when facing high-temperature formations, preventing the rheological properties and other characteristics of the drilling fluid from being affected by high temperatures and thus avoiding increased energy consumption. The introduction of 2-acrylamido-2-methylpropanesulfonic acid can prevent precipitation when encountering formations containing calcium and magnesium ions, thus preventing significant changes in the rheological properties of the drilling fluid. The tetraphenylethylene used in this invention is a compound containing carbon-carbon double bonds and four benzene rings. Its non-coplanar side groups facilitate electronic transitions and polymerization. Furthermore, its four benzene rings give it good pressure-bearing capacity. n-Butyl acrylate is an important intermediate in the temperature-sensitive anti-collapse plugging agent, and its strong polarity makes it difficult for the polymer chains to rotate, improving the polymer's pressure-bearing capacity. Therefore, the anti-collapse plugging agent possesses a certain pressure-bearing capacity. Furthermore, the present invention employs an environmentally friendly soap-free emulsion polymerization method, which not only reduces costs but also results in polymers with good dispersibility, easy cleaning, and high purity.

[0022] The temperature-sensitive anti-collapse plugging agent of this invention has good compatibility with water-based drilling fluid. It not only does not have a significant impact on the rheological properties of the fluid itself, but also significantly improves its plugging efficiency. When the temperature-sensitive anti-collapse plugging agent is added to the water-based drilling fluid, the plugging rate reaches more than 98%, and the strength of the plugging layer is as high as 7 MPa. Detailed Implementation

[0023] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0024] It should be noted that the process equipment or apparatus not specifically mentioned in the following embodiments are all conventional equipment or apparatus in the art.

[0025] It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or apparatuses. Furthermore, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not intended to limit the order of the method steps or define the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0026] The first aspect of this invention provides a method for preparing a temperature-sensitive anti-collapse plugging agent, the method comprising: polymerizing 2-acrylamido-2-methylpropanesulfonic acid and oleic acid with n-butyl acrylate and tetraphenylethylene using a soap-free emulsion polymerization method under the action of an initiator to obtain a temperature-sensitive anti-collapse plugging agent.

[0027] According to the present invention, the polymerization method is a relatively environmentally friendly soap-free emulsion polymerization method. Soap-free emulsion polymerization optimizes the original emulsion polymerization method. Emulsion polymerization, due to the addition of a large amount of emulsifier, makes the polymer difficult to wash with water, and the emulsifier is expensive, increasing costs. In contrast, soap-free emulsion polymerization only utilizes initiators or polar monomers, grafting the functional groups of the polar monomers onto the macromolecule, allowing the polymer itself to act as a surfactant. Furthermore, the polymer prepared by soap-free emulsion polymerization has good dispersibility, is easy to clean, and has high purity, greatly improving its utilization rate. The thermosensitive anti-collapse sealing agent of the present invention, polymerized using this method, significantly reduces polymerization costs and has a positive effect on its field application.

[0028] According to the present invention, the initiator is selected from one of ammonium persulfate, potassium persulfate, and hydrogen peroxide, and is more preferably ammonium persulfate.

[0029] Specifically, the ammonium persulfate initiator is a 20wt% ammonium persulfate solution.

[0030] In this invention, a temperature-sensitive anti-collapse plugging agent is used. When the initiator is ammonium persulfate, in order to maximize the minimum co-solution temperature and match the temperature of the deep well shale to achieve a better plugging effect, preferably, the mass ratio of deionized water: oleic acid: 2-acrylamido-2-methylpropanesulfonic acid: tetraphenylethylene: n-butyl acrylate: ammonium persulfate is 1:(0.0576-0.0976):(0.0476-0.0876):(0.078-0.136):(0.0188-0.0768):(0.007-0.019), more preferably 1:(0.0624-0.0844):(0.0608-0.0828):(0.09-0.124):(0.0308-0.0648):(0.008-0.015). The oleic acid, 2-acrylamido-2-methylpropanesulfonic acid, tetraphenylethylene, and n-butyl acrylate are subjected to free radical polymerization under the initiation of ammonium persulfate. Ammonium persulfate acts as an initiator, attacking the double bonds of the four monomers to cause polymerization, and also serves as a macromolecular end group, which has a certain emulsifying and stabilizing effect, giving the product better monodispersity.

[0031] According to the present invention, the preparation method of the temperature-sensitive anti-collapse sealing agent specifically includes:

[0032] 2-Acrylamido-2-methylpropanesulfonic acid and oleic acid were dissolved in deionized water, and the pH of the solution was adjusted to 5-7. Under stirring, n-butyl acrylate and tetraphenylethylene were added, the temperature was raised to the reaction temperature, an initiator was added, and polymerization was carried out under a protective atmosphere to obtain a thermosensitive anti-collapse sealing agent.

[0033] Since 2-acrylamido-2-methylpropanesulfonic acid is a water-soluble anionic monomer, it can be hydrolyzed to produce hydrogen ions and is acidic. If its pH is not adjusted to neutral, it is prone to precipitation, making it unstable during the polymerization process.

[0034] The deionized water has a conductivity of ≤0.056 μS / cm (25℃) and a maximum bacterial count of 0.01 CFU / mL.

[0035] According to the present invention, the pH adjuster for creating acidic conditions is selected as NaOH solution, specifically, the NaOH solution has a concentration of 1 mol / L and a purity greater than 99%.

[0036] According to the present invention, the conditions for the polymerization reaction include: a temperature of 55-75°C, more preferably 60°C, and a time of 5.5-7.5 h, more preferably 6.6 h.

[0037] According to a preferred embodiment of the present invention, in order to make the emulsion uniform, a propeller-type stirring rod is used for stirring, wherein the three-blade stirring rod has a length of 400 mm, a blade spread of 60 mm, and a rod diameter of 7 mm, to ensure that the dispersion and aggregation of the solution reach equilibrium.

[0038] According to a preferred embodiment of the present invention, a four-necked flask is selected as the reaction vessel, one of which is connected to a reflux condenser to prevent the loss of substances in the reactor, one of which is connected to a constant pressure dropping funnel to add the initiator, another of which is connected to a stirrer, and the last of which is connected to a protective atmosphere to prevent oxygen from inhibiting polymerization.

[0039] According to the present invention, after the polymerization reaction is completed, a temperature-sensitive anti-collapse sealing agent latex solution is obtained, and the latex solution can be directly used as a sealing agent.

[0040] The second aspect of the present invention provides a temperature-sensitive anti-collapse sealing agent prepared by the method described in the first aspect above, wherein the particle size range of the temperature-sensitive anti-collapse sealing agent is 150-680 nm, preferably meeting the requirements for sealing 1-10 μm cracks in size.

[0041] According to the present invention, the temperature-sensitive anti-collapse sealing agent is temperature-sensitive. When the underground temperature exceeds its minimum co-solution temperature, its surface changes from hydrophilic to oleophilic, playing a good reversal wetting effect on the rock surface and forming a tight sealing layer. Moreover, the temperature-sensitive anti-collapse sealing agent can also generate electrostatic interaction with the crack surface. This intermolecular interaction makes it difficult for it to slip after entering the crack, thus preventing secondary leakage and meeting the requirement that the sealing agent can stay in the crack pores.

[0042] The third aspect of this invention provides the application of the temperature-sensitive anti-collapse plugging agent described in the second aspect above as a plugging agent in water-based drilling fluids.

[0043] A fourth aspect of the present invention provides a water-based drilling fluid containing the temperature-sensitive anti-collapse plugging agent described in the second aspect above.

[0044] According to the present invention, the water-based drilling fluid comprises, by weight, 100 parts water, 2-8 parts bentonite, 0.1-0.4 parts sodium carbonate, 2-6 parts viscosity reducer, 2-8 parts filtration loss reducer, 3-7 parts inhibitor, 2-7 parts alkalinity adjuster, 18-34 parts weighting agent, and 0.5-4.5 parts temperature-sensitive anti-collapse sealing agent.

[0045] According to the present invention, the water-based drilling fluid, in addition to satisfying the above-mentioned composition, preferably comprises the following components: 100 parts water, 3-7 parts bentonite, 0.15-0.35 parts sodium carbonate, 2.5-5.5 parts viscosity reducer, 4-6 parts filtration loss reducer, 4.5-6.5 parts inhibitor, 3.5-6.5 parts alkalinity adjuster, 20-30 parts weighting agent, and 1-4 parts of the temperature-sensitive anti-collapse plugging agent.

[0046] The bentonite is selected from one of calcium-based bentonite, calcium-sodium-based bentonite, and calcium-magnesium-based bentonite, and is more preferably calcium-sodium-based bentonite.

[0047] The viscosity reducer is selected from one of tannin alkali solution, iron-chromium lignin sulfonate, iron-chromium salt, and tannin, and is more preferably iron-chromium lignin sulfonate.

[0048] The filtration loss reducing agent is selected from one of sodium nitrohumate, potassium humate, chromium humic acid, and hydroxypropyl starch, and is more preferably sodium humate.

[0049] The inhibitor is selected from polyacrylamide, potassium chloride, potassium silicate, and the novel polyamine inhibitor HR-2, and is more preferably the novel polyamine inhibitor HR-2. Because the novel polyamine inhibitor HR-2 contains two amine groups, after protonation, it forms ammonium ions, which can be tightly adsorbed with the negative charges in the clay layers, squeezing out the interlayer water and effectively improving the drilling fluid's inhibitory properties.

[0050] The alkalinity regulator is selected from sodium hydroxide and calcium oxide, and is more preferably calcium oxide.

[0051] The weighting agent is selected from one of API barite, magnetite powder, manganese tetroxide, and calcium carbonate, and is more preferably calcium carbonate.

[0052] The water-based drilling fluid provided by this invention has strong plugging properties and can provide guidance for field operations.

[0053] Preparation Example 1

[0054] Step 1: Deionized water, oleic acid, and 2-acrylamido-2-methylpropanesulfonic acid were added to a beaker and stirred at 150 rpm for 15 min to fully dissolve. The pH was then adjusted to 5-7 with NaOH solution. The solution was transferred to a four-necked flask in a water bath. Tetraphenylethylene and n-butyl acrylate were added at 300 rpm, and the temperature was raised to 60°C. When the system temperature reached 60°C, ammonium persulfate solution was added, and the polymerization reaction was carried out under N2 protection for 6.5 h. The weight ratio of deionized water: oleic acid: 2-acrylamido-2-methylpropanesulfonic acid: tetraphenylethylene: n-butyl acrylate: ammonium persulfate was 1:0.0787:0.1:0.0124:0.0488:0.01.

[0055] Step 2: After the polymerization process is completed, a temperature-sensitive anti-collapse sealing agent latex solution is obtained. The latex solution is directly used as the temperature-sensitive anti-collapse sealing agent and is denoted as W1.

[0056] Preparation Example 2

[0057] Step 1: Deionized water, oleic acid, and 2-acrylamido-2-methylpropanesulfonic acid are added to a beaker and stirred at 150 rpm for 15 min to fully dissolve. The pH is then adjusted to 5-7 with NaOH solution. The solution is transferred to a four-necked flask in a water bath. Tetraphenylethylene and n-butyl acrylate are added at 300 rpm, and the temperature is raised to 60°C. When the system temperature reaches 60°C, ammonium persulfate solution is added, and the polymerization reaction is carried out under N2 protection for 6.5 h. The weight ratio of deionized water: oleic acid: 2-acrylamido-2-methylpropanesulfonic acid: tetraphenylethylene: n-butyl acrylate: ammonium persulfate is 1:0.0624:0.0608:0.09:0.0308:0.008.

[0058] Step 2: After the polymerization process is completed, a temperature-sensitive anti-collapse sealing agent latex solution is obtained. The latex solution is directly used as the temperature-sensitive anti-collapse sealing agent and is denoted as W2.

[0059] Preparation Example 3

[0060] Step 1: Deionized water, oleic acid, and 2-acrylamido-2-methylpropanesulfonic acid were added to a beaker and stirred at 150 rpm for 15 min to fully dissolve them. The pH was then adjusted to 5-7 with NaOH solution. The solution was transferred to a four-necked flask in a water bath. Tetraphenylethylene and n-butyl acrylate were added at 300 rpm, and the temperature was raised to 60°C. When the system temperature reached 60°C, ammonium persulfate solution was added, and the polymerization reaction was carried out under N2 protection for 6.5 h. The weight ratio of deionized water: oleic acid: 2-acrylamido-2-methylpropanesulfonic acid: tetraphenylethylene: n-butyl acrylate: ammonium persulfate was 1:0.0844:0.0828:0.124:0.0648:0.015.

[0061] Step 2: After the polymerization process is completed, a temperature-sensitive anti-collapse sealing agent latex solution is obtained. The latex solution is directly used as the temperature-sensitive anti-collapse sealing agent and is denoted as W3.

[0062] Example 1

[0063] The water-based drilling fluid formulation, by weight, consists of: 100 parts tap water, 5 parts calcium-sodium bentonite, 0.25 parts sodium carbonate, 4 parts iron-chromium lignin sulfonate, 5 parts sodium humate, 6 parts novel polyamine inhibitor HR-2, 4.5 parts calcium oxide, 25 parts calcium carbonate, and 3 parts temperature-sensitive anti-collapse plugging agent W1.

[0064] The water-based drilling fluid preparation method is as follows: Calcium-sodium bentonite and sodium carbonate are added to water and stirred at a rate of 4000 r / min for 30 min, then allowed to stand for 24 h for hydration to obtain the base slurry. Ferric chromium lignin sulfonate is added to the base slurry and stirred at a rate of 4000 r / min for 10 min; sodium humate is added and stirred at a rate of 4000 r / min for 10 min; a novel polyamine inhibitor HR-2 is added and stirred at a rate of 4000 r / min for 10 min; calcium oxide is added and stirred at a rate of 4000 r / min for 10 min; calcium carbonate is added and stirred at a rate of 4000 r / min for 30 min; and a temperature-sensitive anti-collapse plugging agent W1 is added and stirred at a rate of 4000 r / min for 10 min to obtain the water-based drilling fluid, denoted as Z1.

[0065] Example 2-3

[0066] Examples 2 and 3 are based on Example 1, except that the temperature-sensitive anti-collapse plugging agent W1 is replaced with temperature-sensitive anti-collapse plugging agents W2 and W3 respectively, while other conditions remain unchanged. The resulting water-based drilling fluids are denoted as Z2 and Z3 respectively.

[0067] Example 4

[0068] The water-based drilling fluid formulation, by weight, is as follows: 100 parts tap water, 3 parts calcium-sodium bentonite, 0.15 parts sodium carbonate, 2.5 parts iron-chromium lignin sulfonate, 4 parts sodium humate, 4.5 parts novel polyamine inhibitor HR-2, 3.5 parts calcium oxide, 20 parts calcium carbonate, and 1 part the temperature-sensitive anti-collapse sealing agent W1 prepared in this invention.

[0069] The water-based drilling fluid preparation method is as follows: Calcium-sodium bentonite and sodium carbonate are added to water and stirred at a rate of 4000 r / min for 30 min, then allowed to stand for 24 h for hydration to obtain the base slurry. Ferric chromium lignin sulfonate is added to the base slurry and stirred at a rate of 4000 r / min for 10 min, sodium humate is added and stirred at a rate of 4000 r / min for 10 min, a novel polyamine inhibitor HR-2 is added and stirred at a rate of 4000 r / min for 10 min, calcium oxide is added and stirred at a rate of 4000 r / min for 10 min, calcium carbonate is added and stirred at a rate of 4000 r / min for 30 min, and finally, a temperature-sensitive anti-collapse plugging agent W1 is added and stirred at a rate of 4000 r / min for 10 min to obtain the water-based drilling fluid, denoted as Z4.

[0070] Examples 5-6

[0071] Examples 5 and 6 are based on Example 4, except that the temperature-sensitive anti-collapse plugging agent W1 is replaced with temperature-sensitive anti-collapse plugging agents W2 and W3 respectively, while other conditions remain unchanged. The resulting water-based drilling fluids are denoted as Z5 and Z6 respectively.

[0072] Example 7

[0073] The water-based drilling fluid formulation, by weight, consists of: 100 parts tap water, 7 parts calcium-sodium bentonite, 0.35 parts sodium carbonate, 5.5 parts iron-chromium lignin sulfonate, 6 parts sodium humate, 6.8 parts novel polyamine inhibitor HR-2, 6.5 parts calcium oxide, 30 parts calcium carbonate, and 4 parts temperature-sensitive anti-collapse plugging agent W1.

[0074] The water-based drilling fluid preparation method is as follows: Calcium-sodium bentonite and sodium carbonate are added to water and stirred at a rate of 4000 r / min for 30 min, then allowed to stand for 24 h for hydration to obtain the base slurry. Ferric chromium lignin sulfonate is added to the base slurry and stirred at a rate of 4000 r / min for 10 min, sodium humate is added and stirred at a rate of 4000 r / min for 10 min, a novel polyamine inhibitor HR-2 is added and stirred at a rate of 4000 r / min for 10 min, calcium oxide is added and stirred at a rate of 4000 r / min for 10 min, calcium carbonate is added and stirred at a rate of 4000 r / min for 30 min, and finally, a temperature-sensitive anti-collapse plugging agent W1 is added and stirred at a rate of 4000 r / min for 10 min to obtain the water-based drilling fluid, denoted as Z7.

[0075] Examples 8-9

[0076] Examples 2 and 3 are based on Example 7, except that the temperature-sensitive anti-collapse plugging agent W1 is replaced with temperature-sensitive anti-collapse plugging agents W2 and W3 respectively, while other conditions remain unchanged. The resulting water-based drilling fluids are denoted as Z8 and Z9 respectively.

[0077] Comparative Example 1

[0078] Comparative Example 1 is based on Example 1, except that the temperature-sensitive anti-collapse sealing agent W1 is omitted, and other conditions remain unchanged, to obtain a water-based drilling fluid, denoted as DZ1.

[0079] Comparative Example 2

[0080] Comparative Example 2 is based on Example 1, but the temperature-sensitive anti-collapse sealing agent W1 is replaced with natural asphalt powder, and other conditions remain unchanged to obtain a water-based drilling fluid, denoted as DZ2.

[0081] Comparative Example 3

[0082] Comparative Example 3 is based on Example 1, but the temperature-sensitive anti-collapse plugging agent W1 is replaced with the thermoplastic polyester plugging agent FDG-EF, while other conditions remain unchanged, to obtain a water-based drilling fluid, denoted as DZ3.

[0083] Comparative Example 4

[0084] Comparative Example 4 is based on Example 1, but the amount of temperature-sensitive anti-collapse sealing agent W1 is modified to 10 parts, while other conditions remain unchanged, to obtain a water-based drilling fluid, denoted as DZ4.

[0085] The composition of the water-based drilling fluid obtained in each embodiment is shown in Table 1, and the composition of the water-based drilling fluid obtained in each comparative example is shown in Table 2.

[0086] Table 1. Composition of water-based drilling fluids in each embodiment.

[0087]

[0088]

[0089] Table 2 Composition of water-based drilling fluids in each comparison example

[0090]

[0091]

[0092] Test case

[0093] The lowest co-solution temperature of the temperature-sensitive anti-collapse plugging agent prepared in this invention was determined, and the plugging performance of the water-based drilling fluid prepared in this invention was tested. The test method refers to GB / T 16783.1-2014 "Field Testing of Drilling Fluids for Petroleum and Natural Gas Industry - Part 1: Water-based Drilling Fluids" to evaluate the water-based drilling fluid prepared in this invention.

[0094] The minimum co-solution temperature was determined by measuring the temperature inflection point corresponding to the sudden change in transmittance of the latex solution of the thermosensitive anti-collapse plugging agents W1-W3 as the temperature changes. Specifically, when the temperature reaches the minimum co-solution temperature, the intermolecular hydrogen bonds in the latex solution of the thermosensitive anti-collapse plugging agent break, and the thermosensitive anti-collapse plugging agent contained in the latex solution becomes lipophilic as a whole. The turbidity of the latex solution leads to a sudden change in transmittance and shows a decreasing trend. Therefore, the temperature corresponding to the inflection point of the sudden change in transmittance is the minimum co-solution temperature of the thermosensitive anti-collapse plugging agent.

[0095] The minimum co-solution temperature of the temperature-sensitive anti-collapse sealing agent was measured using a UV-Vis spectrophotometer.

[0096] Apparent viscosity (AV, mPa·s), plastic viscosity (PV, mPa·s), and dynamic shear force (YP, Pa) were measured using a six-speed rotational viscometer according to the method in GB / T 16783.1-2014.

[0097] The high-temperature high-pressure filtration loss (HTHP, mL) was measured using a high-temperature high-pressure filtration loss meter according to the method in GB / T16783.1-2014;

[0098] API filtration loss (mL) was measured using a medium-pressure filtration loss meter according to the method in GB / T 16783.1-2014;

[0099] The UV-Vis spectrophotometer is manufactured by Shimadzu International Trading (Shanghai) Co., Ltd., and its model is UV-1750.

[0100] The manufacturer of the six-speed rotational viscometer is Micco Corporation, and the model is ZNN-D6B electronic six-speed rotational viscometer.

[0101] The manufacturer of the high-temperature and high-pressure filter is Meike Company, and the model is GGS42-2A High-Temperature and High-Pressure Filter - PID Electronic Temperature Control.

[0102] The manufacturer of the medium-pressure filtration instrument is Kence Company, and the model is ZNS-2 medium-pressure filtration instrument.

[0103] 1. Lowest eutectic temperature test

[0104] The temperatures corresponding to the sudden changes in transmittance are shown in Table 3.

[0105] Table 3. Test results of the lowest eutectic temperature

[0106] Preparation Example Minimum eutectic temperature (°C) W1 198 W2 218 W3 168

[0107] Because the polymer molecules of the temperature-sensitive anti-collapse plugging agent have numerous hydrophilic groups such as carboxyl groups, sulfonic acid groups, amide groups, and hydroxyl groups, these polar groups can form hydrogen bonds with water molecules below the minimum co-solution temperature, causing water molecules to form a hydration film on the surface of the temperature-sensitive anti-collapse plugging agent. Above the minimum co-solution temperature, these hydrogen bonds are broken, and the hydration film ruptures. At this point, the presence of benzene rings and ester groups on the polymer macromolecular chain makes the entire molecular chain hydrophobic. Therefore, as shown in Table 3, when the monomers containing hydrophilic groups (oleic acid and 2-acrylamido-2-methylpropanesulfonic acid) in the temperature-sensitive anti-collapse plugging agent of this invention account for 7.82% of the total monomers (temperature-sensitive anti-collapse plugging agent W2), the maximum minimum co-solution temperature is 218°C.

[0108] 2. Blocking performance test

[0109] The base slurry (water + 5% bentonite + 2.5% sodium carbonate, where the percentage content of each component is based on the weight of water) was placed in the mud cup of a high-temperature and high-pressure filtration loss tester. The high-temperature and high-pressure filtration loss test was conducted for 30 minutes at a temperature of 160℃ and a pressure difference of 3.5MPa. After the test, the slurry was cooled to room temperature, and the base slurry in the mud cup was poured out, leaving a filter cake at the bottom of the mud cup. Distilled water was injected along the inner wall of the mud cup 1-2 times, gently shaking it during the injection process. The distilled water was then poured out to wash away the loose mud on the filter cake. Distilled water was then injected into the mud cup to the mark, and the high-temperature and high-pressure filtration loss test process was repeated at a temperature of 160℃ and a pressure difference of 3.5MPa for 30 minutes to further wash away the loose mud. After the test, the slurry was cooled to room temperature, the distilled water was poured out, the mud cake in the mud cup was removed, and the mud cake permeability of the base slurry was calculated using formula (1) to be 523×10⁻⁶. -2 mD; The above-mentioned base slurry cake is used as a simulated formation with micro-nano fractures;

[0110]

[0111] Where K represents permeability, in mD; q represents average filtration loss per unit time, in cm. 3 / s; l represents the cake thickness in mm; μ represents the drilling fluid viscosity in mPa·s; A represents the cake area in m². 2 Δp represents the pressure difference, in MPa.

[0112] Water-based drilling fluids Z1-Z9 and DB1-DB4 were used as test slurries and aged (aging temperature 160℃, aging time 16h). After cooling to room temperature, they were placed in the mud cups of a high-temperature, high-pressure filtration analyzer (the bottom of the mud cup used the aforementioned base slurry cake as the filtration medium). A high-temperature, high-pressure filtration loss test was conducted for 30 minutes at 160℃ and a pressure difference of 3.5MPa. After the test, the fluid was cooled to room temperature, and the slurry in the mud cup was poured out, leaving a test slurry cake at the bottom. Water was injected along the inner wall of the mud cup 1-2 times, gently agitating it during injection. The water was then poured out to wash away any loose mud on the filter cake. Water was then injected back into the mud cup. The high-temperature and high-pressure filtration loss test process was repeated at the scale, with a temperature of 160℃ and a pressure difference of 3.5MPa. The test time was 30min to further wash away the loose mud. After the test, the mud was cooled to room temperature, the water was poured out, the test mud cake in the mud cup was taken out, and the mud cake permeability of Z1-Z9 and DZ1-DZ4 was calculated according to the formula (1) above (denoted as K1, mD). Based on this, the plugging rate of the simulated formation before and after plugging of Examples Z1-Z9 and Comparative Examples DZ1-DZ4 was calculated using the formula (2) (that is, the plugging rate is used to characterize the plugging effect. The higher the plugging rate, the better the plugging effect of the plugging material). The results are shown in Table 4.

[0113]

[0114] Where Kr represents the plugging rate, %; K0 represents the permeability of the base slurry cake (simulated formation), mD; and K1 represents the permeability of the test slurry cake, mD.

[0115] Table 4 Evaluation of Blocking Effectiveness

[0116]

[0117]

[0118] The evaluation of the plugging effect shows that the temperature-sensitive anti-collapse plugging agent prepared in this invention has good plugging efficiency at higher temperatures, and has a significant advantage compared with the plugging effects of other comparative examples. This is because the temperature-sensitive anti-collapse plugging agent prepared in this invention contains polar groups such as hydroxyl and amide groups, which gives it good dispersibility in water-based drilling fluids. Under positive pressure differential, the temperature-sensitive anti-collapse plugging agent enters the fracture and is held in place by intermolecular forces. As the temperature rises, the temperature-sensitive anti-collapse plugging agent changes from hydrophilic to lipophilic, preventing filtrate intrusion and effectively increasing the plugging rate to over 98%. It can also be seen that when the dosage of the temperature-sensitive anti-collapse plugging agent is too high, the plugging efficiency decreases. This is because excessive dosage causes the plugging agent to agglomerate, preventing it from entering the fracture for plugging. In addition, the addition of oleic acid gives the temperature-sensitive anti-collapse plugging agent phase change heat storage performance. When the drilling fluid is aged at high temperature, oleic acid can absorb heat and change from solid to liquid, making the drilling fluid system more resistant to high temperature and preventing the drilling fluid system from being destroyed by high temperature, thereby improving the plugging rate.

[0119] 3. Compatibility test

[0120] The water-based drilling fluid slurry A is prepared by weight as follows: 100 parts tap water, 7 parts calcium sodium bentonite, 0.25 parts sodium carbonate, 4 parts iron chromium lignin sulfonate, 5 parts sodium humate, 6 parts novel polyamine inhibitor HR-2, 4.5 parts calcium oxide, and 25 parts weighting agent.

[0121] Adding a temperature-sensitive anti-collapse sealing agent W1, accounting for 3% of the mass of tap water, to the above-mentioned base slurry A yields water-based drilling fluid B.

[0122] The rheological parameters of water-based drilling fluid A and water-based drilling fluid B at room temperature were tested respectively, and the results are shown in Table 5.

[0123] Table 5. Rheological parameter test results

[0124] Drilling fluid AV(mPa·s) PV (mPa·s) YP(Pa) A 65 45 7 B 74 41 9

[0125] As can be seen from Table 5, the temperature-sensitive anti-collapse plugging agent of the present invention has little effect on the apparent viscosity, plastic viscosity and dynamic shear force of water-based drilling fluid, and the apparent viscosity increase rate is only 13.8%, indicating that the temperature-sensitive anti-collapse plugging agent prepared by the present invention has good compatibility with water-based drilling fluid.

[0126] 4. Pressure resistance test

[0127] The pressure-bearing capacity of the prepared drilling fluids Z1, Z2, and Z3 was tested, and the results are shown in Table 6.

[0128] Table 6 Pressure Bearing Capacity Test

[0129] withstand pressure 1MPa 5MPa 9MPa 11MPa Z1 √ √ √ √ Z4 √ √ √ × Z7 √ √ × ×

[0130] As shown in Table 6 above, water-based drilling fluid Z1 can withstand 11 MPa pressure and maintain a stable pressure; water-based drilling fluid Z4 has the second highest pressure resistance, with the plugging agent particles deforming and breaking at 9 MPa pressure; water-based drilling fluid Z7 has the weakest pressure resistance, able to withstand 5 MPa pressure, but unable to support 9 MPa pressure. This is because drilling fluid Z7 contains the highest amount of plugging agent, leading to hydrogen bonding between the hydrophilic groups of the plugging agent and causing some aggregation.

[0131] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a temperature-sensitive anti-sloughing plugging agent, characterized in that, The 2-acrylamido-2-methylpropane sulfonic acid and the oleic acid are dissolved in water, the pH value is adjusted to 5-7, the n-butyl acrylate and the tetraphenyl ethylene are added under stirring, the reaction temperature is increased to the reaction temperature, the initiator is added, and the polymerization reaction is carried out under the protection of the atmosphere to obtain the temperature-sensitive anti-sloughing plugging agent.

2. The preparation method of the temperature-sensitive anti-collapse sealing agent according to claim 1, characterized in that, Specifically comprising: The 2-acrylamido-2-methylpropane sulfonic acid and the oleic acid are dissolved in water, the pH value is adjusted to 5-7, the n-butyl acrylate and the tetraphenyl ethylene are added under stirring, the reaction temperature is increased to the reaction temperature, the initiator is added, and the polymerization reaction is carried out under the protection of the atmosphere to obtain the temperature-sensitive anti-sloughing plugging agent.

3. The preparation method of the temperature-sensitive anti-collapse sealing agent according to claim 1, characterized in that, The reaction temperature is 55-75℃, and the reaction time is 5.5-7.5h.

4. The preparation method of the temperature-sensitive anti-collapse sealing agent according to claim 1, characterized in that, The mass ratio of the oleic acid, the 2-acrylamido-2-methylpropane sulfonic acid, the tetraphenyl ethylene, the n-butyl acrylate and the initiator is (0.0576-0.0976):(0.0476-0.0876):(0.078-0.136):(0.0188-0.0768):(0.007-0.019).

5. The temperature-sensitive anti-sloughing plugging agent obtained by the preparation method in any one of claims 1-4.

6. A water-based drilling fluid, characterized by The temperature-sensitive anti-sloughing plugging agent in claim 5.

7. The water-based drilling fluid of claim 6, wherein, According to the mass fraction, it comprises: 100 parts of water, 2-8 parts of bentonite, 0.1-0.4 parts of sodium carbonate, 2-6 parts of viscosity reducer, 2-8 parts of fluid loss reducer, 3-7 parts of inhibitor, 2-7 parts of alkalinity regulator, 18-34 parts of weighting agent, and 0.5-4.5 parts of temperature-sensitive anti-sloughing plugging agent.

8. The water-based drilling fluid of claim 7, wherein, The bentonite is one of calcium-based bentonite, calcium-sodium-based bentonite and calcium-magnesium-based bentonite. And / or, the viscosity reducer is one of tannin liquor, iron-chromium lignin sulfonate, iron-chromium salt and tannin extract.

9. The water-based drilling fluid of claim 7, wherein, The fluid loss reducer is one of nitro humic acid sodium, humic acid potassium, chromium humic acid and hydroxypropyl starch. And / or, the inhibitor is one of polyacrylamide, potassium chloride, potassium silicate and polyamine.

10. The water-based drilling fluid of claim 7, wherein, The alkalinity regulator is one of sodium hydroxide and calcium oxide. And / or, the weighting agent is one of API barite, magnetite powder, manganese tetroxide and calcium carbonate.

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