Rope knot temporary plugging ball with empennage for acid fracturing and preparation method of rope knot temporary plugging ball

Abstract

The invention discloses a rope knot temporary plugging ball with empennages for acid fracturing and a preparation method thereof, and relates to the technical field of oil and gas development, and the preparation method comprises the following steps: uniformly mixing homopolyamide fibers, modified polyamide-imide fibers PAI-X, an antioxidant, a coupling agent and a plasticizer, and carrying out melt extrusion granulation to obtain inner-layer spherical particles; part of the inner-layer sphere particles are treated through melt spinning and twisting and doubling processes to obtain fiber fine lines, then the fiber fine lines are woven into ropes and cut off to obtain short ropes, the short ropes and the inner-layer spheres are bonded and assembled to obtain knots, the knots are stretched, and the stretched knots are subjected to dip coating treatment to obtain the composite material. The rope knot temporary plugging ball with the empennage for acid fracturing has a unique flexible deformation rope knot shape design and a high-molecular degradable polymer material, the double-layer structure can effectively improve the pressure bearing capacity and plugging capacity of the rope knot temporary plugging ball, and a good sealing effect can be formed on perforation holes with irregular shapes and sizes.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas development, in particular to a temporary plugging ball with a tail wing knot for acid fracturing and a preparation method thereof. Background Art

[0002] During the acid fracturing of deep carbonate rocks, the reservoir thickness is large and the vertical heterogeneity is strong, which leads to limited effect of general reservoir transformation; the mechanical tool layered and segmented transformation operation is complex, the safety risk is high, and the construction cost is high. In view of the above situation, the existing chemical plugging is generally carried out by using degradable temporary plugging materials. The temporary plugging materials can temporarily reduce the permeability of the formation or temporarily plug the high permeability oil and gas layer. After being mixed with the traditional acid fracturing working fluid and injected into the well, they can quickly form a dense temporary plugging zone of the oil and gas layer under the action of pressure difference, and can be unblocked by themselves after a certain period of time. However, due to the large span of carbonate reservoirs, the diversity and complexity of geological structures, the strong heterogeneity of some reservoirs, and the large difference in the opening pressure of the formation, there are many reasons in the process of acid fracturing construction, such as it is difficult to achieve the effective opening of the whole cluster, some perforation clusters have not been transformed or the transformation is insufficient, and the existing temporary plugging materials are not temperature-resistant in the acid solution and degrade too quickly, and the pressure bearing capacity is insufficient, resulting in low temporary plugging pressure, and it is unable to meet the full transformation of high-temperature and high-pressure deep carbonate wells.

[0003] As in the prior art, Chinese patent CN2020104473635 discloses a temporary plugging agent with tassels at both ends, its preparation method and application, the preparation method comprising: making water-absorbing swelling and deforming fibers and high-strength rigid fibers to be combined and paralleled to form a temporary plugging fiber bundle; knotting the temporary plugging fiber bundle to form a temporary plugging fiber bundle with a tassel knot body in the middle and tassels at both ends; and impregnating the temporary plugging fiber bundle with tassels at both ends with polyester resin to obtain a temporary plugging agent with tassels at both ends. The temporary plugging agent with tassels at both ends of the present invention has a pressure-bearing strength of up to 70MPa, which can plug perforations, even deformed perforations, and reduce the amount of bridge plugs and temporary plugging agents, or even replace bridge plugs to form a more effective plugging, but it degrades quickly in acid and has poor plugging pressure-bearing capacity.

[0004] In recent years, as carbonate rock development advances into deep areas, reservoir temperatures and pressures are getting higher and higher. There is no report on temporary plugging balls with tail knots suitable for acid fracturing with formation temperatures above 170°C and pressures above 65MPa. Summary of the invention

[0005] In view of this, the present invention has developed a temporary plugging ball with a tail knot for acid fracturing, which is prepared by a series of processing techniques using high-strength, flexible and acid-degradable polymer fibers, and has a strong ability to adapt to different perforation hole shapes and sizes, and can form a good temporary plugging effect on perforation holes with irregular shapes and sizes. In the temporary plugging acidizing construction, the temporary plugging ball with a tail knot can block part of the holes, prompting the acid to be pumped into the perforation clusters that have not been transformed or are insufficiently transformed for transformation, thereby expanding the transformation volume. After a period of time after the construction is completed, the temporary plugging ball with a tail knot can be degraded in the acid to release the hole blockage and resume production.

[0006] The invention discloses a method for preparing a temporary plugging ball with a tail knot for acid fracturing, which mainly comprises the following steps:

[0007] Step S1: homopolyamide, modified polyamide-imide fiber PAI-X, antioxidant, coupling agent and plasticizer are mixed and then melt-extruded and granulated to obtain inner spherical particles, wherein the modified polyamide-imide fiber PAI-X is synthesized by modification with chiral N,N-pyromellitoyl-bis-L-amino acid;

[0008] Step S2: melt spinning and twisting of some inner spherical particles are sequentially processed to obtain fiber threads, and then the fiber threads are sequentially braided into ropes, sheared, and long ropes are cut to obtain short ropes, and the short ropes are bonded to the surface of the inner sphere by an adhesive to assemble into a knot and stretch the knot;

[0009] Step S3: The stretched rope knot is subjected to an immersion coating treatment to obtain the temporary plugging ball with a tail wing rope knot for acid fracturing.

[0010] Preferably, the method for preparing a temporary plugging ball with a tail knot for acid fracturing in the present invention specifically comprises the following steps:

[0011] Step 1: Dry each component separately at 120°C;

[0012] Step 2: Using a multi-component spinning machine, the mixed component materials are melt-extruded and granulated with a single-screw extruder to obtain an inner spherical structure, and then a fiber wire with a diameter of about 1 mm is made according to different proportions through a twisting and doubling process (twist coefficient is 0.5);

[0013] Step 3: Setting a certain tension, rotation speed and twist to twist the plurality of polymer fiber threads into strands;

[0014] Step 4: The fiber thin wires are twisted in an S-twist manner according to 4 to 9 strands and woven into a rope to form a fiber thin rope;

[0015] Step 5: Use a cutting machine to cut the fiber rope into long ropes according to the required knot size, and use an adhesive to adhere the cut short ropes to the surface of the inner spherical structure to obtain a knot, and then stretch the assembled knot with a tensile machine.

[0016] Step 6: Dip the knot into the coating at 50°C for 1 hour, then air-dry it for 24 hours. Adjust the hydrophilicity and hydrophobicity of the coating material according to the working environment in the wellbore.

[0017] The diameter of the temporary plugging ball with tail wing knot for acid fracturing in the present invention mainly depends on the size of the perforation hole. In order to make the knot for acid fracturing better seated in the hole, the diameter of the temporary plugging ball with tail wing knot is determined according to the size of the perforation hole, and is generally larger than the hole diameter. Therefore, in the present invention, the diameter range of the inner layer ball of the temporary plugging ball with tail wing knot for acid fracturing is as shown in formula (1):

[0018] 1.3R <d<2.0R (1)

[0019] In formula (1), d is the inner diameter of the temporary plugging ball with tail knot for acid fracturing, mm, R is the diameter of the hole to be plugged, mm;

[0020] After being assembled with the inner sphere, the diameter of the knot is 1-3 mm larger than the diameter of the inner sphere.

[0021] The schematic diagram of the appearance structure of the temporary plugging ball with tail wing knot for acid fracturing described in the present invention is in the shape of a knot, as shown in FIG. Figure 1 As shown, the knot length is 80-90mm, and the density is different according to the density of the raw materials themselves. The density of the finished product is 1.20-1.30g / cm 3 between.

[0022] In the present invention, in order to avoid the problem of divergence of degradable materials caused by low twist during knot processing, the knot is coated using an immersion coating technique. Preferably, the coating accounts for 5%-7% of the knot mass, and the coating material formula is: by mass fraction, 10%-15% of polycationic electrolyte, 8%-15% of polyzwitterionic electrolyte, 2%-10% of heterocycloalkyl-modified silica nanoparticles, and the balance is an aqueous solvent.

[0023] The modified polyamide-imide fiber PAI-X is a thermoplastic resin composed of a flexible amide group and a heat-resistant imide ring arranged in a regular pattern, and has the characteristics of better rigid structure, excellent heat resistance, good chemical stability, etc., wherein the modified polyamide-imide fiber PAI-X is modified and synthesized by using N, N-pyromellitic acid-bis-L-amino acid, and the introduction of amino acid fragments makes PAI-X have better solubility, and its degradation time in acid solution can be regulated by controlling the proportion of PAI-X in the knot temporary plugging ball. In the present invention, the preparation method of the modified polyamide-imide fiber PAI-X comprises the following steps:

[0024] Step (1): N, N- (pyrrolyl) -bis-L-amino acid (2a), 4, 4'-diaminodiphenyl ether, triphenyl phosphate, pyridine, CaCl2 and N-methyl-2-pyrrolidone are uniformly mixed, and stirred at 120 ° C for 8 hours, wherein the mass ratio of N, N- (pyrrolyl) -bis-L-amino acid (2a), 4, 4'-diaminodiphenyl ether, triphenyl phosphate, pyridine, CaCl2, and N-methyl-2-pyrrolidone is 1-2: 1-1.5: 6-6.5: 4.5-5.0: 2-3: 20-22 in terms of mass;

[0025] Step (2): After the reaction is completed, cool to room temperature and transfer the polymer to ethanol for precipitation while stirring. Filter and wash the precipitate, and vacuum dry at 40-50° C. for at least 12 h.

[0026] One embodiment of the present invention is that the homopolyamide is PA4T / 46, and PA4T contains a high-density amide group and a benzene ring structure, so that it has excellent heat resistance and mechanical strength, but the melting point of PA4T (325°C) exceeds its decomposition temperature (310°C), which increases its processing difficulty. By integrating the characteristics of PA4T and PA46, the processing performance and dimensional stability of each can be improved, and the heat resistance and mechanical properties (compressive strength>110MPa, melting point 300°C) can be further improved.

[0027] The preparation method of PA4T / 46 can refer to the prior art. Preferably, the PA4T / 46 in the present invention is synthesized by low-temperature solution polycondensation, and the synthesis steps are as follows:

[0028] (1) Add dry N,N-dimethylacetamide and anhydrous calcium chloride to a three-necked flask equipped with a mechanical stirrer, and introduce N2 to purge and replace the air. Repeat the purge three or more times to remove the relevant components in the air to prevent them from interfering with the experiment.

[0029] (2) Heat the solution to 70°C and stir for 2 hours. After the calcium chloride solid is completely dissolved, apply an ice water bath. At the same time, add triethylamine and 1,4-butanediamine solution under nitrogen protection. After the raw materials are evenly mixed, slowly add terephthaloyl chloride and adipoyl chloride solution dropwise while vigorously stirring.

[0030] (3) Maintain the water bath temperature at about 0°C for 30 minutes, then continue to maintain at room temperature for 6 hours, and a white precipitate will appear at the bottom. Pour the solution into deionized water, and all the reaction products will precipitate out. Rinse thoroughly with methanol and acetone to remove triethylamine hydrochloride impurities and N,N-dimethylacetamide solvent residues, and place the product obtained by suction filtration in a constant temperature drying oven to dry to constant weight to obtain homopolyamide PA4T / 46.

[0031] The specification of the homopolyamide fiber PA4T / 46 is 600-1500D. Preferably, the specification of the homopolyamide fiber PA4T / 46 used in the present invention is 800D, and the specification of the modified polyamide-imide fiber PAI-X is 900-1000D. Preferably, the specification of the modified polyamide-imide fiber PAI-X in the present invention is 1000D. The larger the D, the thicker the fiber. The thicker the fiber, the worse the sealing performance during twisting and forming. The larger the gap between the fibers, the worse the pressure bearing capacity. However, the smaller the D, the smaller the fiber, the smaller the pressure it can withstand during twisting and forming, and the easier it is to be broken. The fibers may break before they are tightened, making it difficult to tighten and form. Through a large number of experiments, different fiber bundles of this model and specification are selected by comprehensive consideration.

[0032] The assembled knot also needs to be stretched using a tensile testing machine to increase its strength. The main purpose of stretching the knot is to increase its own strength. Therefore, the tension used for the knot cannot be less than 700kg. If it is too small, the knot will not be strong enough and there will be more space gaps. If it is too large, it will be easily broken due to the tensile resistance of the raw material itself. Preferably, the tension used to stretch the knot in the present invention is between 700kg and 1000kg.

[0033] One embodiment of the present invention is that, in parts by mass, the ratio of the homopolyamide, the modified polyamide-imide fiber PAI-X, the antioxidant, the coupling agent, the plasticizer, and the adhesive is 6-8:1-2:0.01-0.2:0.01-0.2:0.006-0.03:0.05-0.1.

[0034] One embodiment of the present invention is that the antioxidant is antioxidant 1098, the coupling agent is one or more combinations of KH550, KH560, and KH792, the plasticizer is one or more combinations of neopentyl glycol, pentaerythritol, and triethanolamine, and the adhesive is acrylate-modified waterborne polyurethane WPUA.

[0035] Preferably, the adhesive acrylate-modified waterborne polyurethane WPUA is prepared by first modifying the waterborne polyurethane with melamine, and then modifying the waterborne polyurethane with acrylate to obtain WPUA, which can effectively improve its heat resistance. The synthesis steps are as follows:

[0036] (1) Weigh poly(1,4-butylene adipate) diol and add it to a three-necked flask equipped with a stirring rod and a thermometer, and dehydrate it at a temperature of 100°C and a vacuum degree of 0.095 MPa for 1 hour; then weigh isophorone diisocyanate and add it to the three-necked flask, and react it at 90°C for 3 hours; weigh dimethylolpropionic acid, 1,4-butylene glycol, melamine, and acetone, and react it at 80°C for 1 hour; dropwise add stannous octoate and dibutyltin dilaurate, and Add acetone and react at 70°C for 4 hours; cool to 55°C, weigh hydroxyethyl acrylate and add it to a three-necked flask, and react at 65°C for 2 hours; cool to 50°C, put the product into an emulsification barrel, add triethylamine for neutralization, add water at 900r / min for emulsification, then add ethylenediamine for chain extension, and react for 25 minutes; finally, remove acetone at a temperature of 60°C and a vacuum degree of 0.095MPa to obtain a water-based polyurethane emulsion. Among them, in terms of mass fractions, the mass ratios of poly(1,4-butylene adipate) glycol, isophorone diisocyanate, dihydroxymethylpropionic acid, 1,4-butanediol, melamine, acetone, stannous octoate, dibutyltin dilaurate, hydroxyethyl acrylate, triethylamine, and ethylenediamine are 8330-8340:3700-3705:495-500:284-288:260-265:2630-2640:1-1.2:1-1.5:140-142:337-340:190-195.

[0037] (2) Weigh methyl methylpropionate, butyl acrylate, emulsifier, potassium persulfate, synthesized waterborne polyurethane, and deionized water in a three-necked flask equipped with a thermometer and a stirring rod, emulsify at 700 r / min for 20 min; heat to 75° C. for 6 h; and cool naturally to 40° C. to terminate. The mass ratio of methyl methylpropionate, butyl acrylate, emulsifier, potassium persulfate, and synthesized waterborne polyurethane is 0.5-1:2-3:0.01-0.03:0.003-0.007:6-8 in terms of mass fraction.

[0038] At the same time, the invention also discloses a temporary plugging ball with a tail knot for acid fracturing prepared by the method.

[0039] The technical effects of the present invention are:

[0040] (1) The temporary plugging ball with tail wing for acid fracturing in the present invention has a unique flexible deformable knot-shaped design and a high molecular biodegradable polymer material. The double-layer structure can effectively improve the pressure bearing capacity and sealing capacity of the temporary plugging ball, and can form a good sealing effect on perforations of irregular shapes and sizes.

[0041] (2) The temporary plugging ball with tail knot for acid fracturing in the present invention can be fully dissolved in an acidic environment (pH 1-6), and the complete dissolution time in a 20% hydrochloric acid solution is >32h, and the pressure bearing capacity is >65MPa. It has excellent acid resistance, pressure bearing strength and flexible deformation capacity, is suitable for acidic wellbore environment and has no environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a schematic diagram of the finished product structure of a temporary plugging ball with a tail knot for acid fracturing in the present invention;

[0043] Figure 2 (a) is an annular filling container for evaluating temporary plugging balls with tail knots for acid fracturing in the present invention;

[0044] Figure 2 (b) is a flow test device for evaluating temporary plugging balls with tail knots for acid fracturing in the present invention;

[0045] Figure 3 The graph is a construction curve of acid fracturing in a deep high-temperature carbonate well using the temporary plugging ball with a tail knot for acid fracturing of the present invention. DETAILED DESCRIPTION

[0046] The present invention will be further described in detail below in conjunction with the examples, but the embodiments of the present invention are not limited thereto. The experimental methods used in the following examples are conventional methods unless otherwise specified; the materials, reagents, etc. used therein are all commercially available unless otherwise specified.

[0047] Example 1

[0048] Step S1: homopolyamide PA4T / 46, modified polyamide-imide fiber PAI-X, antioxidant, coupling agent, and plasticizer are mixed and melt-extruded to obtain inner spherical particles, wherein the mass ratios of homopolyamide PA4T / 46, modified polyamide-imide fiber PAI-X, antioxidant 1098, coupling agent KH550, plasticizer pentaerythritol, and acrylate-modified waterborne polyurethane WPUA adhesive are 7:1:0.1:0.15:0.01:0.05, respectively, and the mass ratios of modified polyamide PA4T / 46, modified polyamide-imide fiber PAI-X, antioxidant 1098, coupling agent KH550, plasticizer pentaerythritol, and acrylate-modified waterborne polyurethane WPUA adhesive are 7:1:0.1:0.15:0.01:0.05, respectively. The amide-imide fiber PAI-X is synthesized according to the above method, and the proportions of the raw materials in its synthesis are, by mass, N,N-(pyrrolyl)-bis-L-amino acid (2a), 4,4'-diaminodiphenyl ether, triphenyl phosphate, pyridine, CaCl2, and N-methyl-2-pyrrolidone are 1:1.2:6:4.5:2:20; the specification of the homopolyamide fiber PA4T / 46 is 800D, the specification of the modified polyamide-imide fiber PAI-X is 1000D, and the diameter of the inner layer spherical particles is 13 mm.

[0049] Step S2: Process part of the inner spherical particles by melt spinning and twisting to obtain fiber threads, and then weave the fiber threads into ropes, shear, and cut the long ropes to obtain short ropes. In this process, 6 polymer fibers are twisted into strands; in combination with the tensile strength of the fiber to avoid breaking, the tension is set to 18N; in combination with the deformation during the stretching process and the friction exothermic effect, the rotation speed is set to 160r / min and the twist is set to 90 twists / m. Then, the short rope and the inner sphere are glued together and stretched to obtain a knot. After assembly, the total diameter of the knot temporary blocking ball including the part of the knot wrapped around the inner sphere is 14-16mm, and the knot length is 85mm. The long rope is cut into short ropes according to the required knot size by a cutting machine and placed neatly. The middle part of the cut short rope is adhered to the surface of the inner sphere structure using an acrylate-modified water-based polyurethane WPUA adhesive, and then the assembled knot is stretched using a tensile testing machine with a force of 800kg to increase its own strength.

[0050] Step S3: The knot is subjected to coating immersion treatment to obtain the temporary plugging ball with tail wing knot for acid fracturing, wherein the coating accounts for 5% of the mass of the knot, and the coating material formula is: polydimethyldiallylammonium chloride PDADMAC 12%, poly 4-vinylpyridine-N-(2-ethoxycarbonylethyl) 12%, methyltrimethoxysilane MTMS modified nano-silica 6%, and polyethylene glycol 70%.

[0051] Example 2

[0052] Step S1: homopolyamide PA4T / 46, modified polyamide-imide fiber PAI-X, antioxidant, coupling agent, and plasticizer are mixed and melt-extruded to obtain inner spherical particles, wherein the mass ratios of homopolyamide PA4T / 46, modified polyamide-imide fiber PAI-X, antioxidant 1098, coupling agent KH550, plasticizer pentaerythritol, and acrylate-modified waterborne polyurethane WPUA adhesive are 8:2:0.2:0.1:0.02:0.07, and the mass ratios of modified polyamide-imide fiber PAI-X and modified polyamide-imide fiber PAI-X are 8:2:0.2:0.1:0.02:0.07, respectively. The amine fiber PAI-X is synthesized according to the above method, and the proportions of the raw materials in its synthesis are, by mass, N,N-(pyrrolyl)-bis-L-amino acid (2a), 4,4'-diaminodiphenyl ether, triphenyl phosphate, pyridine, CaCl2, and N-methyl-2-pyrrolidone are 1.2:1.5:6.5:4.5:2.5:21; the specification of the homopolyamide fiber PA4T / 46 is 900D, the specification of the modified polyamide-imide fiber PAI-X is 1000D, and the diameter of the inner layer spherical particles is 15mm.

[0053] Step S2: Process part of the inner spherical particles by melt spinning and twisting to obtain fiber threads, and then weave the fiber threads into ropes, shear, and cut the long ropes to obtain short ropes. In this process, 6 polymer fibers are twisted into strands; in combination with the tensile strength of the fiber to avoid breaking, the tension is set to 18N; in combination with the deformation during the stretching process and the friction exothermic effect, the rotation speed is set to 160r / min and the twist is set to 90 twists / m. Then, the short rope and the inner sphere are glued together and stretched to obtain a knot. After assembly, the total diameter of the knot temporary blocking ball including the part of the knot wrapped around the inner sphere is 16-18mm, and the knot length is 90mm. The long rope is cut into short ropes according to the required knot size by a cutting machine and placed neatly. The middle part of the cut short rope is adhered to the surface of the inner sphere structure using an acrylate-modified water-based polyurethane WPUA adhesive, and then the assembled knot is stretched using a tensile testing machine with a force of 850kg to increase its own strength.

[0054] Step S3: The knot is subjected to coating immersion treatment to obtain the temporary plugging ball with tail wing knot for acid fracturing, wherein the coating accounts for 7% of the mass of the knot, and the coating material formula is: 15% polydimethyldiallylammonium chloride PDADMAC, 15% poly 4-vinylpyridine-N-(2-ethoxycarbonylethyl), 10% methyltrimethoxysilane (MTMS) modified nano-silica, and 60% polyethylene glycol.

[0055] In order to better illustrate the technical effects of the present invention, performance evaluation and field application evaluation are provided for relevant embodiments below.

[0056] 1. Acid degradation performance evaluation:

[0057] The degradation time of the temporary plugging ball with tail knot for acid fracturing prepared in the embodiment was tested under 10%, 15% and 20% hydrochloric acid conditions to evaluate the acid degradation performance of the temporary plugging ball. The evaluation device was a ring-shaped filling container with an inner diameter of one inch, as shown in the following example. Figure 2 As shown in (a), when the experiment is carried out, Figure 2 (b) is carried out in the flow experiment device shown in FIG. 1 , and the specific process is as follows:

[0058] Fill the test sample in Figure 2 (a) In a circular container, place Figure 2 (b) The pressure bearing strength, degradation rate in acid and complete degradation time were tested in the flow test device shown. The temperature of the core holder was raised to the test temperature, and 15% hydrochloric acid was injected by pumping. The temporary plugging ball with tail knot will cause the injection pressure to rise sharply. The injection pressure was stabilized at the test pressure, the test temperature was maintained, and the tolerance temperature, temporary plugging strength and temporary plugging time were observed and recorded.

[0059] Take a temporary plugging ball with a tail knot and weigh it as M1, and place it in a 500mL sealed bottle; add 400mL of clean water, and then place the sample in a constant temperature box set at a certain temperature. After a certain period of time, filter the sample with filter paper, dry it and weigh it, and record the mass of the remaining temporary plugging ball with a tail knot as M2.

[0060] The degradation rate R in the temporary plugging ball with tail wing knot is calculated according to formula (2):

[0061] R=(M1-M2) / M1×100% (2)

[0062] In the formula: M1 is the original mass of the temporary blocking ball with a tail knot, g; M2 is the remaining mass of the temporary blocking ball with a tail knot, g.

[0063] The specific experimental results are shown in Table 1:

[0064] Table 1 Acid solution temporary plugging test evaluation results

[0065]

[0066] It can be seen from Table 1 that the temporary plugging ball with a tail knot for acid fracturing in Example 1-2 can be fully dissolved in an acidic environment (pH is 1 to 6), and under high temperature conditions (≤185°C), the complete dissolution time in a 20% hydrochloric acid solution is ≥32h, and the pressure bearing capacity is ≥65MPa, which means that the temporary plugging ball with a tail knot for acid fracturing can be used in an environment below 185°C, has a high compressive strength, and can be accelerated by acid to remove the plugging.

[0067] 2. Field application:

[0068] Taking the fracturing of a deep carbonate gas well as an example, the well was drilled to a depth of 7480 meters and the formation temperature was between 170-180℃. The acidification + knot temporary plugging + alternating injection acid fracturing process was used to fully transform the 6588-6615m (upper perforation section) and 6623-6641m (lower perforation section). The upper perforation section (6588-6615m) was firstly treated with acidification to remove the pollution blockage, and then the knot temporary plugging was used to plug the upper perforation section, and the alternating injection acid fracturing process was used to connect the far well reservoir to the lower perforation section (6623-6641m). The total design scale is 800m 3 , including 240m3 of acid reduction 3 , gelling acid 340m 3 , autogenous acid 220m 3 , 432 knots temporarily blocked, designed gelled acid ≥5m 3 / min, autogenous acid ≥ 4m 3 / min, the perforation aperture is 10mm, the pressure bearing capacity is required to be ≥60MPa, and the temporary plugging ball with tail knot is 16-18mm in diameter. The composition of the raw materials in Example 2 is used to prepare 432 temporary plugging balls with tail knot for acid fracturing applied to ultra-high temperature reservoirs <180℃. The construction pressure curve is as follows Figure 3 As shown in the figure, the difference between the temporary plugging pressure increase and the construction pressure before and after temporary plugging is large, indicating that the temporary plugging ball with tail rope knot successfully plugs the perforation hole after reaching the perforation hole, causing the fluid to turn between the perforation clusters, forcing the unfractured perforation clusters to fracture and create new fractures, and the pressure rises significantly, achieving the expected temporary plugging effect; after the construction is completed, the temporary plugging ball with tail rope knot is completely degraded under the action of the bottom hole temperature, leaving no residue and causing zero damage to the formation. The specific fracturing construction steps are as follows:

[0069] First construction: casing displacement 0.3m 3 / min, low displacement and drag acid liquid volume up to 25m 3 When the clean water in the pipe column is completely replaced, the water starts to flow at 2.2m 3 / min pumping 195m 3 The high squeeze-drop acid removes the crack contamination, the oil pressure drops, and the crack is successfully opened.

[0070] Second construction: Add temporary plugging balls with tail wing knots for acid fracturing to the ground high-pressure three-way pipeline before construction. 432 temporary plugging balls with tail wing knots were thrown in a 2.7m 3 / min displacement was used for pumping. After the acid fracturing was temporarily plugged with a tail rope knot to the perforation hole, the oil pressure increased by 4.0MPa and the casing pressure increased by 5.1MPa. Then the casing displacement was increased to 6.5m 3 / min, and then the high-extrusion autogenous acid and high-extrusion gel acid were pumped alternately in two stages, 220m each 3 and 340m 3, stop the pump for 30 minutes, wait for the crack to close, and then pump at 2.0-3.0m 3 / min displacement pumping 20m 3 Closed acidizing was performed with low squeeze-out acid resistance, and finally 2.0-3.0m 3 / min displacement pumping 30m 3 The resistance-reducing water will completely displace the acid in the well formation.

[0071] It can be seen that the application principle of the temporary plugging ball with a tail knot for acid fracturing provided by the present invention in the acid fracturing process is that: after being pumped into the wellbore, the temporary plugging ball with a tail knot for acid fracturing flows along the direction of least resistance with the acid liquid, firstly plugging the opened layer section, and plugging the perforation holes in the low pressure zone formed by the opened layer section; since the temporary plugging agent is in the shape of a knot, the material is flexible and has high strength, and can form an excellent sealing effect on the perforation holes of irregular size and shape through deformation, forcing the subsequent fluid to enter the perforation holes in the unfractured high pressure zone, promoting the generation of new cracks and forming a complex seam network, and at the same time, the temporary plugging ball with a tail knot for acid fracturing is made of degradable fiber, and after the construction is completed, it can be degraded within the required time range of fracturing, without polluting the formation and affecting production; at the same time, the applicable formation temperature and degradation time can be controlled by adjusting the ratio of each degradable material. The temporary plugging ball with a tail knot for acid fracturing provided by the present invention has the characteristics of achieving efficient plugging of irregular perforations, strong pressure bearing capacity, and controllable degradation in acid solution without residue.

[0072] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the embodiments of the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing a temporary plugging ball with a tail knot for acid fracturing, characterized in that: The following steps are involved: Step S1: homopolyamide fiber, modified polyamide-imide fiber PAI-X, antioxidant, coupling agent and plasticizer are mixed and melt-extruded to form granules to obtain inner spherical particles, wherein the modified polyamide-imide fiber PAI-X is synthesized by modification with chiral N,N-pyromellitic acid-bis-L-amino acid, and the fiber specification is 900-1000D; Step S2: melt spinning and twisting of some inner spherical particles are sequentially processed to obtain fiber threads, and then the fiber threads are sequentially braided into ropes, sheared, and long ropes are cut to obtain short ropes, and the short ropes are bonded to the surface of the inner sphere by an adhesive to assemble into a knot and stretch the knot; Step S3: The stretched rope knot is subjected to an immersion coating treatment to obtain the temporary plugging ball with a tail wing rope knot for acid fracturing.

2. The method for preparing a temporary plugging ball with a tail knot for acid fracturing according to claim 1, characterized in that: Calculated by mass, the ratio of the homopolyamide, the modified polyamide-imide fiber PAI-X, the antioxidant, the coupling agent, the plasticizer and the adhesive is 6-8:1-2:0.01-0.2:0.01-0.2:0.006-0.03:0.05-0.

1.

3. The method for preparing a temporary plugging ball with a tail knot for acid fracturing according to claim 1, characterized in that: The homopolyamide fiber is PA4T / 46, and its fiber specification is 600-1500D.

4. The method for preparing a temporary plugging ball with a tail knot for acid fracturing according to claim 1, characterized in that: The antioxidant is antioxidant 1098, the coupling agent is one or more combinations of KH550, KH560, and KH792, the plasticizer is one or more combinations of neopentyl glycol, pentaerythritol, and triethanolamine, and the adhesive is acrylate-modified waterborne polyurethane WPUA.

5. The method for preparing a temporary plugging ball with a tail knot for acid fracturing according to claim 1, characterized in that: The diameter range of the inner layer of the temporary plugging ball with tail knot for acid fracturing is as shown in formula (1): 1.3R <d<2.0R (1) In formula (1), d is the inner diameter of the temporary plugging ball with tail knot for acid fracturing, mm, R is the diameter of the hole to be plugged, mm; After being assembled with the inner sphere, the diameter of the knot is 1-3 mm larger than the diameter of the inner sphere.

6. The method for preparing a temporary plugging ball with a tail knot for acid fracturing according to claim 1, characterized in that: The knot length of the temporary plugging ball with a tail knot for acid fracturing is 80-90 mm, and the tension range for stretching the knot is 700 kg-1000 kg.

7. The method for preparing a temporary plugging ball with a tail knot for acid fracturing according to claim 1, characterized in that: The twist coefficient in the twisting and doubling process is 0.5, the diameter of the obtained fiber wire is 0.8-1.2 mm, and the outer fiber rope is woven from 4-9 fiber wires twisted in the S direction.

8. The method for preparing a temporary plugging ball with a tail knot for acid fracturing according to claim 1, characterized in that: The coating material used in the dip coating treatment accounts for 5%-7% of the knot mass, wherein, by mass fraction, the coating material includes the following components: 10%-15% polycationic electrolyte, 8%-15% polyzwitterionic electrolyte, 2%-10% heterocycloalkyl-modified silica nanoparticles, and the balance is aqueous solvent.

9. The method for preparing a temporary plugging ball with a tail knot for acid fracturing according to claim 1, characterized in that: The preparation method of the modified polyamide-imide fiber PAI-X comprises the following steps: Step (1): N, N- (pyrrolyl) -bis-L-amino acid (2a), 4, 4'-diaminodiphenyl ether, triphenyl phosphate, pyridine, CaCl2 and N-methyl-2-pyrrolidone are uniformly mixed, and stirred at 120 ° C for 8 hours, wherein the mass ratio of N, N- (pyrrolyl) -bis-L-amino acid (2a), 4, 4'-diaminodiphenyl ether, triphenyl phosphate, pyridine, CaCl2, and N-methyl-2-pyrrolidone is 1-2: 1-1.5: 6-6.5: 4.5-5.0: 2-3: 20-22 in terms of mass; Step (2): After the reaction is completed, cool to room temperature and transfer the polymer to ethanol for precipitation while stirring. Filter and wash the precipitate, and vacuum dry at 40-50° C. for at least 12 h.

10. A temporary plugging ball with a tail knot for acid fracturing, characterized in that: The method is prepared by any one of claims 1 to 9.

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