Solid sustained-release anti-fouling microparticles for oil and gas reservoir development and a preparation method thereof

Abstract

The application provides a solid slow-release anti-fouling particle for oil and gas reservoir development and a preparation method thereof, and belongs to the technical field of oil and gas well formation and wellbore fouling prevention and treatment. The application provides a solid slow-release anti-fouling particle for oil and gas reservoir development, which comprises the following components in parts by mass: polyester slow-release carrier 50-85 parts, polyester modifier 0.5-3 parts and scale inhibitor 12-49.5 parts, wherein the polyester modifier comprises one or more of isophthalic acid, diethylene glycol and polycarbodiimide. The application solves the technical difficulties: the scale inhibitor is combined with the polyester slow-release carrier, which overcomes the disadvantages of low effective component, large dosage and short period of conventional modified anti-fouling proppant and liquid anti-fouling agent. The solid slow-release anti-fouling particle for oil and gas reservoir development provided by the application slowly dissolves and releases in the formation fracture, can achieve the anti-fouling target of the formation and wellbore, and has the technical advantages of low single-well dosage, good anti-fouling effect, long slow-release period and complete degradation.

Description

Technical Field

[0001] This invention relates to the field of scale prevention and control technology for oil and gas well formations and wellbore, and particularly to a solid slow-release scale inhibitor microparticle for oil and gas reservoir development and its preparation method. Background Technology

[0002] With the increasing development of unconventional oil and gas wells such as shale oil, shale gas, coal gas, ultra-deep wells, and ultra-long horizontal wells, the large-scale promotion and application of offshore oil and gas fields, and the repeated fracturing of old oil and gas wells as an important measure for stabilizing and increasing production, the conflict between near-formation and wellbore scaling is becoming increasingly prominent. Due to the requirements of repeated fracturing of unconventional oil and gas wells and old wells, reservoir fracturing is generally required before extraction to artificially create flow-conducting fractures. Therefore, adding chemical scale inhibitors during the fracturing process is a very effective scale prevention technology that can simultaneously delay near-formation and wellbore scaling.

[0003] In fracturing operations in oil and gas fields, solid slow-release anti-scaling microparticles enter the oil layer fractures with the fracturing fluid. Under certain temperature, pressure and production fluid medium, they slowly dissolve and release, and the scale inhibitor contained in them is also released into the production fluid and maintains a certain concentration. Through the chemical anti-scaling effect of the scale inhibitor, the deposition of various scales on the surface of the oil layer, wellbore and its pipes is prevented and slowed down.

[0004] Currently, there are many types of slow-release scale inhibitors both domestically and internationally. For example, Chinese patent CN105038750A discloses a slow-release scale inhibitor for oil well modification, which, by weight percentage, comprises 35-45% main agent, 5-15% auxiliary agent, and 40-50% skeleton. Chinese patent CN112080264A discloses scale inhibitor particles, their preparation method, and applications, comprising a slow-release core layer and a rapid-release outer layer. The rapid-release outer layer wraps around the slow-release core layer, thereby inhibiting the scale release of the scale inhibitor. Formulated as immediate / slow-release granules, these scale inhibitors offer both immediate and slow-release rates, and boast a high agent loading rate, resulting in a long-lasting protective effect on oil wells. Chinese patent CN111909675A discloses a solid granular scale inhibitor comprising a binder, adsorbent, composite scale inhibitor, slow-release agent, and crosslinking agent. Through the combined effects of the slow-release action of polyvinyl alcohol, the locking effect of the adsorbent, and the slow-dissolving outer shell, the solid granular scale inhibitor is slowly released into the wellbore pocket, with an effective period exceeding 60 days. However, existing slow-release scale inhibitors all suffer from the drawback of a short effective period. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a solid slow-release scale inhibitor microparticle for oil and gas reservoir development and its preparation method. The solid slow-release scale inhibitor microparticle for oil and gas reservoir development provided by this invention has a long slow-release effective period (complete degradation in indoor simulation experiments requires 1114 days).

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a solid slow-release scale inhibitor microparticle for oil and gas reservoir development, comprising the following components in parts by weight: 50-85 parts of polyester slow-release carrier, 0.5-3 parts of polyester modifier, and 12-49.5 parts of scale inhibitor, wherein the polyester modifier comprises one or more of isophthalic acid, diethylene glycol, and polycarbodiimide.

[0008] Preferably, the polyester slow-release carrier comprises thermoplastic polyester.

[0009] Preferably, the thermoplastic polyester comprises one or more of polyethylene terephthalate (PET), polylactic acid (PLA), polybutylene succinate (PBS), polybutylene terephthalate, polypropylene terephthalate, polycaprolactone, and polyβ-hydroxybutyric acid.

[0010] Preferably, the thermoplastic polyester includes one or more of polyethylene terephthalate, polylactic acid, and polybutylene succinate.

[0011] Preferably, the thermoplastic polyester comprises polyethylene terephthalate and polylactic acid, wherein the mass ratio of polyethylene terephthalate to polylactic acid in the thermoplastic polyester is 60-96:4-40.

[0012] Preferably, the thermoplastic polyester comprises polylactic acid and polybutylene succinate, wherein the mass ratio of polylactic acid to polybutylene succinate in the thermoplastic polyester is 90-95:5-10.

[0013] Preferably, the thermoplastic polyester comprises polyethylene terephthalate, polylactic acid, and polybutylene succinate, wherein the mass ratio of polyethylene terephthalate, polylactic acid, and polybutylene succinate in the thermoplastic polyester is 94-98:1-3:1-3.

[0014] Preferably, the polyester modifier comprises isophthalic acid, diethylene glycol, and polycarbodiimide, wherein the mass ratio of isophthalic acid, diethylene glycol, and polycarbodiimide is 0–0.4:0.1–0.8:0–0.8.

[0015] Preferably, the scale inhibitor comprises one or more of ethylenediaminetetramethylenephosphonic acid (EDTMP), hexamethylenediaminetetramethylenephosphonic acid (HDTMPA), disodium ethylenediaminetetraacetate (EDTA-2Na), 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA), and polyepoxysuccinic acid (PESA).

[0016] This invention also provides a method for preparing the solid slow-release scale inhibitor particles for oil and gas reservoir development described in the above technical solution, comprising the following steps:

[0017] The polyester slow-release carrier, polyester modifier and scale inhibitor are mixed and then granulated to obtain the solid slow-release scale inhibitor microparticles for oil and gas reservoir development.

[0018] This invention provides a solid slow-release scale inhibitor microparticle for oil and gas reservoir development, comprising the following components in parts by weight: 50-85 parts of polyester slow-release carrier, 0.5-3 parts of polyester modifier, and 12-49.5 parts of scale inhibitor, wherein the polyester modifier comprises one or more of isophthalic acid, diethylene glycol, and polycarbodiimide.

[0019] In this invention, the polyester slow-release carrier is a long-chain polymer material. In the oil and gas well production environment, the H in the water... + It will first come into contact with the carbonyl oxygen atom, causing it to be protonated, which will increase the positive charge of the carbonyl carbon and enhance its ability to accept water molecule attack. Then the water molecules can more easily come into contact with the carbonyl carbon and destroy the ester group through addition-elimination reaction to form carboxylic acid and alcohol. The long molecular carbon chain breaks, which is macroscopically manifested as the slow degradation of the carrier from the outside to the inside, releasing the encapsulated scale inhibitor into the oil and gas well production fluid.

[0020] The polyester modifier, interphthalic acid (IPA), can disrupt the high symmetry and regularity of the macromolecular chains of the polyester slow-release carrier. The increased free volume resulting from its meta-substitution increases the spacing between the macromolecular chains, loosening the chain arrangement and increasing the mobility of the macromolecular chains, thus lowering the melting point of the polyester slow-release carrier. Simultaneously, it accelerates the diffusion and arrangement of chain segments towards the crystal nucleus during crystallization, leading to incomplete and more disordered crystallization of the polyester slow-release carrier. This results in a decrease in crystallization rate and crystallinity, lowering the melting point of the polyester slow-release carrier, disrupting the regularity of the macromolecular chains, thereby reducing processing temperature, simplifying processing, and improving processing efficiency and yield. Diethylene glycol (DEG) can also disrupt the regularity of the polyester slow-release carrier molecular chains, reducing intermolecular forces, lowering the melting point of the polyester slow-release carrier, and lowering the processing temperature. Because DEG... The main chain is relatively long and contains ether bonds that facilitate the rotation of the polyester sustained-release carrier molecular chain. The introduction of DEG greatly improves the flexibility of the polyester sustained-release carrier molecular chain, lowers the melting point of the polyester sustained-release carrier, thereby reducing the processing and molding temperature, reducing processing difficulty, and improving processing efficiency and yield. The role of polycarbodiimide: It grafts onto the broken chains of the polyester sustained-release carrier, thereby restoring or partially restoring the performance of the polymer material and extending its service life. The carbodiimide groups in the polycarbodiimide group have high reactivity with the carboxyl groups in the polyester sustained-release carrier, which can generate structurally stable urea compounds. This reduces the carboxyl groups generated by the hydrolysis of ester bonds in the polyester sustained-release carrier molecular chain due to water erosion in the application environment (oil and gas well production fluids), effectively inhibiting molecular chain breakage caused by hydrolysis of the polyester sustained-release carrier, reducing the product dissolution rate, and extending the effective life cycle.

[0021] The scale inhibitor achieves its scale prevention and inhibition purpose by chelating scale cations to increase solubility, preventing and slowing down the formation of scale crystal nuclei, and interfering with and destroying the precipitation and deposition process of scale crystals.

[0022] This invention is the first to combine scale inhibitors with polyester slow-release carriers, overcoming the drawbacks of conventional modified scale inhibitor proppants and liquid scale inhibitors, such as low effective components, large dosage, and short cycle. The solid slow-release scale inhibitor microparticles for oil and gas reservoir development provided by this invention slowly dissolve and release in formation fractures, achieving the scale prevention goals of formation and wellbore. It has technical advantages such as low dosage per well, good scale prevention effect, long slow-release cycle, and complete degradation, and has broad market prospects.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1. Long effective period: The product has an effective period of more than 3 years, as the scale inhibitor continues to dissolve and release slowly;

[0025] 2. Stable structure: The polyester slow-release carrier material has high strength, good compressive strength, and stable structure under high temperature and high pressure.

[0026] 3. Excellent scale prevention effect: The product has a good scale inhibition effect and can prevent scale formation in near-surface pores and wellbore at the same time;

[0027] 4. Complete degradation: The polyester slow-release carrier can be completely degraded into small molecule products and is weakly acidic, which can reduce the pH of the product liquid and produce a continuous weak acidification effect.

[0028] 5. Convenient construction: The product is mixed into fracturing sand and injected into the formation in conjunction with the fracturing fluid system, making construction convenient;

[0029] 6. Minimal Loss: The product is in the form of solid particles, which allows it to better remain in the formation, resulting in minimal leakage and loss.

[0030] 7. No adverse effects on the formation: It does not react with the formation to form scale, does not clog the formation, and does not contaminate the oil layer;

[0031] 8. Good compatibility: It does not affect the permeability of the fracturing fluid system and does not react chemically with the fracturing fluid system.

[0032] The present invention also provides a method for preparing the solid slow-release anti-scaling microparticles for oil and gas reservoir development described in the above technical solution. The preparation method provided by the present invention is simple and easy to implement and is suitable for industrial application. Attached Figure Description

[0033] Figure 1 This is a flowchart illustrating the preparation of solid slow-release anti-scaling microparticles for oil and gas reservoir development according to the present invention. Detailed Implementation

[0034] This invention provides a solid slow-release scale inhibitor microparticle for oil and gas reservoir development, comprising the following components in parts by weight: 50-85 parts of polyester slow-release carrier, 0.5-3 parts of polyester modifier, and 12-49.5 parts of scale inhibitor, wherein the polyester modifier comprises one or more of isophthalic acid, diethylene glycol, and polycarbodiimide.

[0035] Unless otherwise specified, all raw materials used in this invention are commercially available products in the field.

[0036] The preferred mass fraction of the polyester slow-release carrier in the solid slow-release scale inhibitor microparticles for oil and gas reservoir development provided by the present invention is 60-80 parts, more preferably 73.7-79 parts.

[0037] In this invention, the polyester slow-release carrier preferably comprises thermoplastic polyester.

[0038] In this invention, the thermoplastic polyester preferably includes one or more of polyethylene terephthalate (PET), polylactic acid (PLA), polybutylene succinate (PBS), polybutylene terephthalate, polypropylene terephthalate, polycaprolactone, and polyβ-hydroxybutyric acid.

[0039] In this invention, the thermoplastic polyester preferably includes one or more of polyethylene terephthalate, polylactic acid, and polybutylene succinate.

[0040] In this invention, the thermoplastic polyester preferably includes polyethylene terephthalate and polylactic acid, and the mass ratio of polyethylene terephthalate to polylactic acid in the thermoplastic polyester is preferably 60-96:4-40, more preferably 3:1.

[0041] In this invention, the thermoplastic polyester preferably includes polylactic acid and polybutylene succinate, and the mass ratio of polylactic acid to polybutylene succinate in the thermoplastic polyester is preferably 90-95:5-10, more preferably 9:1.

[0042] In this invention, the thermoplastic polyester preferably includes polyethylene terephthalate, polylactic acid and polybutylene succinate, and the mass ratio of polyethylene terephthalate, polylactic acid and polybutylene succinate in the thermoplastic polyester is preferably 94-98:1-3:1-3, more preferably 70:2.2:1.5.

[0043] In this invention, the mechanism of action of the polyester slow-release carrier is as follows: the polyester slow-release carrier is a long-chain polymer material. In the oil and gas well production environment, the H in the water... +It will first come into contact with the carbonyl oxygen atom, causing it to protonate, which will enhance the positive charge of the carbonyl carbon. This will enhance its ability to accept water molecule attacks. Then, water molecules can more easily come into contact with the carbonyl carbon and destroy the ester group through addition-elimination reaction to form carboxylic acids and alcohols. The long molecular carbon chain breaks, which is macroscopically manifested as the slow degradation of the carrier from the outside to the inside, releasing the encapsulated scale inhibitor into the oil and gas well production fluid.

[0044] The preferred mass fraction of the polyester modifier in the solid slow-release scale inhibitor microparticles for oil and gas reservoir development provided by the present invention is 0.5 to 2 parts, more preferably 0.8 to 1 part.

[0045] In this invention, the polyester modifier preferably comprises isophthalic acid, diethylene glycol, and polycarbodiimide, and the mass ratio of isophthalic acid, diethylene glycol, and polycarbodiimide is preferably 0–0.4:0.1–0.8:0–0.8. In specific embodiments of this invention, the ratios are 0.3:0.5:0.2, 0.4:0.8:0.8, and 0.1:0.1:0.8.

[0046] The preferred mass fraction of the scale inhibitor in the solid slow-release scale inhibitor microparticles for oil and gas reservoir development provided by the present invention is 18 to 39 parts, more preferably 19.5 to 25.5 parts, and most preferably 20 parts.

[0047] In this invention, the scale inhibitor preferably comprises one or more of ethylenediaminetetramethylenephosphonic acid, hexamethylenediaminetetramethylenephosphonic acid, disodium ethylenediaminetetraacetate, 2-phosphonobutane-1,2,4-tricarboxylic acid, and polyepoxysuccinic acid. The scale inhibition mechanism is as follows: The phosphonic acid group -PO3H2 and carboxylic acid group -COOH in the scale inhibitor increase solubility by chelating scale cations, inhibiting and slowing down the formation of scale crystal nuclei, and interfering with and destroying the precipitation and deposition process of scale crystals, thereby achieving the purpose of scale prevention and inhibition. The specific mechanism of action is as follows: Solubilization effect: The scale inhibitor can react with Ca 2+ 、Sr 2+ Ba 2+The scale inhibitor forms soluble complexes or chelates with the cations that form scale, increasing the solubility of insoluble inorganic salts (i.e., scale) in water and reducing the probability of scale precipitation. Dispersion effect: The negatively charged polyions dissociated from the scale inhibitor collide with scale-forming microcrystals, undergoing physical and chemical adsorption, resulting in a dispersed state. They remain suspended in the aqueous solution without precipitating and can be discharged with the fluid, without adhering to the metal surface to form scale. Electrostatic repulsion effect: The charged groups on the scale inhibitor's molecular chain repel each other, causing the molecular chain to expand. Positively charged inorganic salt microcrystals adsorb onto the polyions, and the charge on the microcrystals increases the electrostatic repulsion between particles, hindering collisions and the formation of large crystals that precipitate as scale. Crystal distortion effect: After dissolving in water, the scale inhibitor chelates with metal cations, occupying a certain position in the scale lattice. This hinders or interferes with the normal growth of non-scale-forming microcrystals, causing inorganic salt lattice distortion, preventing the formation of large crystal precipitates and reducing deposition intensity.

[0048] In one specific embodiment of the present invention, the scale inhibitor comprises hexamethylenediaminetetramethylenephosphonic acid, disodium ethylenediaminetetraacetate, and polyepoxysuccinic acid, wherein the mass ratio of hexamethylenediaminetetramethylenephosphonic acid, disodium ethylenediaminetetraacetate, and polyepoxysuccinic acid is 17:1:2; in another specific embodiment of the present invention, the scale inhibitor comprises ethylenediaminetetramethylenephosphonic acid and polyepoxysuccinic acid, wherein the mass ratio of ethylenediaminetetramethylenephosphonic acid and polyepoxysuccinic acid is 13:5; in yet another specific embodiment of the present invention, the scale inhibitor comprises ethylenediaminetetramethylenephosphonic acid, hexamethylenediaminetetramethylenephosphonic acid, disodium ethylenediaminetetraacetate, and 2-phosphonobutane-1,2,4-tricarboxylic acid, wherein the mass ratio of ... is 17:1:2; The mass ratio of phosphonic acid, hexamethylenediaminetetramethylenephosphonic acid, disodium ethylenediaminetetraacetate, and 2-phosphonobutane-1,2,4-tricarboxylic acid is 12:1.5:2:4. In another specific embodiment of the present invention, the scale inhibitor comprises hexamethylenediaminetetramethylenephosphonic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, and polyepoxysuccinic acid, wherein the mass ratio of hexamethylenediaminetetramethylenephosphonic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, and polyepoxysuccinic acid is 1.5:4:20. In another specific embodiment of the present invention, the scale inhibitor comprises ethylenediaminetetramethylenephosphonic acid and polyepoxysuccinic acid, wherein the mass ratio of ethylenediaminetetramethylenephosphonic acid and polyepoxysuccinic acid is 9:30.

[0049] In this invention, the solid slow-release anti-scaling microparticles for oil and gas reservoir development are preferably spherical or cylindrical particles. The diameter of the spherical particles is preferably 0.6 to 1.7 mm, and the diameter of the cylindrical particles is preferably 0.8 to 1.2 mm, and the height is preferably 1.0 mm.

[0050] This invention also provides a method for preparing the solid slow-release scale inhibitor particles for oil and gas reservoir development described in the above technical solution, comprising the following steps:

[0051] The polyester slow-release carrier, polyester modifier and scale inhibitor are mixed and then granulated to obtain the solid slow-release scale inhibitor microparticles for oil and gas reservoir development.

[0052] In this invention, the polyester slow-release carrier and the scale inhibitor are preferably dried separately before mixing. The drying is preferably vacuum drying, and the scale inhibitor is preferably dried to a weight loss rate of less than 0.3% at a constant temperature of 160°C for 24 hours.

[0053] In this invention, the scale inhibitor preferably further includes being pulverized into a fine powder of 100-200 mesh after drying.

[0054] In this invention, the granulation is preferably carried out in a twin-screw extruder.

[0055] In this invention, the granulation temperature is preferably 60-190°C, more preferably 160-180°C.

[0056] In this invention, the granulation preferably includes the following three methods:

[0057] Method 1: The material is drawn from the die of the twin-screw extruder, cooled by air cooling, and then cut into pellets by a pelletizer;

[0058] Method 2: The material is drawn from the die of the twin-screw extruder, cooled by liquid cooling, the coolant is blown away by an air knife, and then cut into pellets by a pelletizer;

[0059] Method 3: The material is extruded from the die of the twin-screw extruder and cut off by a rotating cutter along the die surface in the coolant. The extruded material is then centrifuged to remove the coolant.

[0060] After granulation, the present invention preferably further processes the material through a vibrating screen to obtain the solid slow-release anti-scaling microparticles for oil and gas reservoir development.

[0061] Figure 1 This is a flowchart illustrating the preparation of solid slow-release anti-scaling microparticles for oil and gas reservoir development according to the present invention.

[0062] The present invention also provides the application of the solid slow-release scale inhibitor particles for oil and gas reservoir development described in the above technical solution, preferably including the following steps:

[0063] After the solid slow-release anti-scaling microparticles used for oil and gas reservoir development are mixed with fracturing sand, they enter the formation fractures and remain there.

[0064] In this invention, the amount of solid slow-release anti-scaling microparticles used for oil and gas reservoir development is preferably 0.03 to 0.5% of the volume of fracturing sand, more preferably 0.07 to 0.09%.

[0065] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0066] This invention relates to the performance indicators and testing methods of solid slow-release anti-scaling microparticles for oil and gas reservoir development.

[0067] The performance evaluation indicators of solid slow-release scale inhibitor particles for oil and gas reservoir development in this invention include sample morphology, apparent density, sieve compliance rate (characterizing particle size range), breakage rate (characterizing compressive strength), scale inhibition rate, viscosity retention rate (characterizing compatibility with fracturing fluid), average dissolution rate (characterizing effective period), and compatibility with formation water.

[0068] The test method for the performance index of solid slow-release anti-scaling microparticles for oil and gas reservoir development in this invention is implemented in accordance with the enterprise standard document "Q / HD 001-2024 Formation Long-term Slow-release Anti-scaling Microparticles" of Shaanxi Hongda Zhongwei Petroleum Technology Co., Ltd., which has been published on the enterprise standard information public service platform.

[0069] The performance indicators of the solid slow-release anti-scaling microparticles for oil and gas reservoir development of this invention are shown in Table 1.

[0070] Table 1 Performance indicators of solid slow-release scale inhibitor particles for oil and gas reservoir development according to the present invention

[0071]

[0072]

[0073] In the embodiments, "parts" refers to parts by mass.

[0074] Raw material source description:

[0075] Polyethylene terephthalate (PET) was selected from CR-8863 type from China Resources Chemical Materials Technology Co., Ltd.; polylactic acid (PLA) was selected from REVODE213S type from Zhejiang Hisun Biomaterials Co., Ltd.; and polybutylene succinate (PBS) was selected from TH803S type from Xinjiang Lanshan Tunhe Technology Co., Ltd.

[0076] IPA was selected from the product of Beijing Yanshan Branch of China Petroleum & Chemical Corporation, diethylene glycol (DEG) was selected from the product of CNOOC Shell Petrochemical Co., Ltd., and polycarbodiimide was selected from BASF WO2 type.

[0077] Ethylenediaminetetramethylenephosphonic acid (EDTMP) and hexamethylenediaminetetramethylenephosphonic acid (HDTMPA) were selected from the solid products of Shandong Kairui Chemical Co., Ltd., 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA) was selected from the solid products of Hebei Longke Water Treatment Co., Ltd., and disodium ethylenediaminetetraacetate (EDTA-2Na) and polyepoxysuccinic acid (PESA) were selected from the solid products of Shandong Taihe Technology Co., Ltd.

[0078] Example 1

[0079] The solid slow-release scale inhibitor microparticles for oil and gas reservoir development consist of 79 parts polyethylene terephthalate, 0.3 parts isophthalic acid, 0.5 parts diethylene glycol, 0.2 parts polycarbodiimide, 17 parts hexamethylenediaminetetramethylenephosphonic acid, 1 part disodium ethylenediaminetetraacetate, and 2 parts polyepoxysuccinic acid.

[0080] The above scale inhibitors (hexamethylenediaminetetramethylenephosphonic acid, disodium ethylenediaminetetraacetate, and polyepoxysuccinic acid) are vacuum dried for 5 hours and kept at 160°C for 24 hours. The weight loss rate is less than 0.3% to be considered qualified. They are then pulverized into 180-200 mesh fine powder by an airflow pulverizer and stored in a sealed container.

[0081] The above-mentioned polyester slow-release carrier (polyethylene terephthalate) was vacuum dried for 5 hours.

[0082] The treated polyester slow-release carrier, scale inhibitor, and polyester modified components were added to a high-speed mixer and mixed evenly for 1 hour.

[0083] The uniformly mixed material is added to a twin-screw extruder. The extruder temperature is set in zones from 60 to 190°C, and the screw speed is 150 to 200 r / min. The material exiting the twin-screw extruder die is drawn into strands, cooled in an air-cooling tank, then pelletized by a pelletizer, and finally screened by a vibrating screen to determine the particle size. Cylindrical particles with a length of 1.0 mm.

[0084] Effective lifespan tests of solid slow-release scale inhibitor microparticles for oil and gas reservoir development in simulated formation fluids were conducted. The results are shown in Table 2. By fitting the mass loss data of the scale inhibitor microparticles, the effective dissolution period can be calculated. Under the condition of the fastest release rate, the calculated complete dissolution period is greater than 3 years. The application environment of the scale inhibitor microparticles is oil-water mixed; in actual applications, the dissolution rate will be lower than under pure high-salinity water immersion conditions, and its actual complete dissolution period is much greater than 3 years.

[0085] Table 2. Cumulative mass loss rate of solid slow-release scale inhibitor particles used in oil and gas reservoir development in Example 1 (unit: %)

[0086]

[0087] Release test of scale inhibitors from solid slow-release microparticles for oil and gas reservoir development in formation simulated fluid. Evaluation method: 3g ± 0.1g of scale inhibitor sample was accurately weighed using an analytical balance and placed in 1000mL of formation simulated fluid. The solution was kept at a static temperature of 60℃ for a certain period. After soaking, the sample was removed, and the lost soaking solution was replenished. The phosphorus content of the soaking solution was determined by ICP-MS. Using the scale inhibitor ratio set before processing as a standard, the scale inhibitor release amount and cumulative release loss ratio in the soaking solution were compared and calculated. The above steps were repeated. The total scale inhibitor content in the accurately weighed scale inhibitor sample was taken as 100%, and the cumulative scale inhibitor loss ratio for each soaking was subtracted. The results are shown in Table 3. In the early stage of the test, the scale inhibitor on the surface and in the shallow layer of the scale inhibitor particles dissolved quickly upon contact with water, resulting in a high initial scale inhibitor release concentration. In the middle and later stages, the scale inhibitor release rate was mainly controlled by and synchronized with the dissolution of the carrier. Only after the slow-release carrier degraded could the scale inhibitor contained within it be released into the production fluid, resulting in a slower release rate and a longer release period.

[0088] Table 3. Test rate of scale inhibitor residue in solid slow-release scale inhibitor particles for oil and gas reservoir development in Example 1 (unit: %)

[0089]

[0090] Table 4 compares the technical specifications of the solid slow-release scale inhibitor microparticles for oil and gas reservoir development in Example 1 with those of other examples and similar products at home and abroad.

[0091] Example 2

[0092] The solid slow-release scale inhibitor microparticles for oil and gas reservoir development consist of 80 parts polylactic acid, 0.4 parts isophthalic acid, 0.8 parts diethylene glycol, 0.8 parts polycarbodiimide, 13 parts ethylenediaminetetramethylenephosphonic acid, and 5 parts polyepoxysuccinic acid.

[0093] The above scale inhibitors (ethylenediaminetetramethylenephosphonic acid and polyepoxysuccinic acid) are qualified if the weight loss rate is less than 0.3% after vacuum drying for 5 hours and constant temperature at 160℃ for 24 hours. They are then pulverized into 100-150 mesh fine powder by airflow pulverizer and stored in a sealed container.

[0094] The above-mentioned polyester slow-release carrier (polylactic acid) was vacuum dried for 5 hours.

[0095] The treated polyester slow-release carrier, scale inhibitor, and polyester modified components were added to a high-speed mixer and mixed evenly for 1 hour.

[0096] The uniformly mixed material is added to a twin-screw extruder. The extruder temperature is set between 60 and 160°C, and the screw speed is between 160 and 220 r / min. The material exiting the twin-screw extruder die is cut and extruded in ethylene glycol coolant by a rotating cutter along the die surface. The extruded material is then centrifuged to remove the ethylene glycol coolant, and then screened by a vibrating screen to determine the particle size. Spherical particles.

[0097] Table 4 compares the technical specifications of the solid slow-release scale inhibitor microparticles for oil and gas reservoir development in Example 2 with those of other examples and similar products at home and abroad.

[0098] Example 3

[0099] 60 parts polyethylene terephthalate, 20 parts polylactic acid, 0.2 parts isophthalic acid, 0.3 parts polycarbodiimide, 12 parts ethylenediaminetetramethylenephosphonic acid, 1.5 parts hexamethylenediaminetetramethylenephosphonic acid, 2 parts disodium ethylenediaminetetraacetate, and 4 parts 2-phosphonobutane-1,2,4-tricarboxylic acid.

[0100] The above scale inhibitors (ethylenediaminetetramethylenephosphonic acid, hexamethylenediaminetetramethylenephosphonic acid, disodium ethylenediaminetetraacetate and 2-phosphonobutane-1,2,4-tricarboxylic acid) are vacuum dried for 5 hours and kept at 160℃ for 24 hours. The weight loss rate is less than 0.3% to be considered qualified. They are then pulverized into 180-200 mesh fine powder by an air jet mill and stored in a sealed container.

[0101] The above-mentioned polyester slow-release carriers (polyethylene terephthalate and polylactic acid) were vacuum dried for 5 hours.

[0102] The treated polyester slow-release carrier, scale inhibitor, and polyester modified components were added to a high-speed mixer and mixed evenly for 1 hour.

[0103] The uniformly mixed material is added to a twin-screw extruder. The extruder temperature is set in zones from 60 to 180°C, and the screw speed is 150 to 200 r / min. The material exiting the twin-screw extruder die is drawn into strands, cooled in an ethylene glycol liquid cooling bath, the coolant is blown off by an air knife, then granulated by a pelletizer, and finally screened by a vibrating screen to determine the particle size. Cylindrical particles with a length of 1.0 mm.

[0104] Table 4 compares the technical specifications of the solid slow-release scale inhibitor particles for oil and gas reservoir development in Example 3 with those of other examples and similar products at home and abroad.

[0105] Example 4

[0106] 70 parts polyethylene terephthalate, 2.2 parts polylactic acid, 1.5 parts polybutylene succinate, 0.4 parts diethylene glycol, 0.4 parts polycarbodiimide, 1.5 parts hexamethylenediaminetetramethylenephosphonic acid, 4 parts 2-phosphonobutane-1,2,4-tricarboxylic acid, and 20 parts polyepoxysuccinic acid.

[0107] The above scale inhibitors (hexamethylenediaminetetramethylenephosphonic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid and polyepoxysuccinic acid) are vacuum dried for 5 hours and kept at 160℃ for 24 hours. The weight loss rate is less than 0.3% to be considered qualified. They are then pulverized into 180-200 mesh fine powder by an airflow pulverizer and stored in a sealed container.

[0108] The above-mentioned polyester slow-release carriers (polyethylene terephthalate, polylactic acid and polybutylene succinate) were vacuum dried for 5 hours.

[0109] The treated polyester slow-release carrier, scale inhibitor, and polyester modified components were added to a high-speed mixer and mixed evenly for 1 hour.

[0110] The uniformly mixed materials are added to a twin-screw extruder. The extruder temperature is set in zones from 60 to 190°C, and the screw speed is 150 to 200 r / min. The material exiting the twin-screw extruder die is cut and extruded in ethylene glycol coolant by a rotating cutter along the die surface. The extruded material is then centrifuged to remove the ethylene glycol coolant, and finally screened by a vibrating screen to determine the particle size. Spherical particles.

[0111] Table 4 compares the technical specifications of the solid slow-release scale inhibitor microparticles for oil and gas reservoir development in Example 4 with those of other examples and similar products at home and abroad.

[0112] Example 5

[0113] 54 parts polylactic acid, 6 parts polybutylene succinate, 0.1 parts isophthalic acid, 0.1 parts diethylene glycol, 0.8 parts polycarbodiimide, 9 parts ethylenediaminetetramethylenephosphonic acid, and 30 parts polyepoxysuccinic acid.

[0114] The above scale inhibitors (ethylenediaminetetramethylenephosphonic acid and polyepoxysuccinic acid) are qualified if the weight loss rate is less than 0.3% after vacuum drying for 5 hours and constant temperature at 160℃ for 24 hours. They are then pulverized into 100-150 mesh fine powder by airflow pulverizer and stored in a sealed container.

[0115] The above-mentioned polyester slow-release carriers (polylactic acid and polybutylene succinate) were vacuum dried for 5 hours.

[0116] The treated polyester slow-release carrier, scale inhibitor, and polyester modified components were added to a high-speed mixer and mixed evenly for 1 hour.

[0117] The uniformly mixed material is added to a twin-screw extruder. The extruder temperature is set between 60 and 160°C, and the screw speed is between 160 and 220 r / min. The material exiting the twin-screw extruder die is drawn into strands, cooled in an air-cooling tank, then pelletized by a pelletizer, and finally screened by a vibrating screen to determine the particle size. Cylindrical particles with a length of 1.0 mm.

[0118] Table 4 compares the technical specifications of the solid slow-release scale inhibitor microparticles for oil and gas reservoir development in Example 5 with those of other examples and similar products at home and abroad.

[0119] Table 4 compares the solid slow-release scale inhibitor particles used in oil and gas reservoir development with other similar products.

[0120]

[0121] As can be seen from Table 4, the solid slow-release scale inhibitor particles prepared in Examples 1-5 for oil and gas reservoir development are superior to similar products at home and abroad in four important aspects: particle breakage rate (characterizing compressive strength), scale inhibition rate, viscosity retention rate (characterizing compatibility with fracturing fluid), and average dissolution rate (characterizing effective period), demonstrating significant technical advantages.

[0122] The technical solution of the present invention can be adjusted in terms of the type and proportion of carriers according to the actual needs on site, so as to be suitable for oil and gas reservoir environments with different temperatures, pressures and ion contents of produced liquids.

[0123] The type and proportion of scale inhibitor in the technical solution of the present invention are adjusted according to the actual needs on site to be suitable for oil and gas reservoir environments with different scale crystal forms, temperatures and product liquid ion contents.

[0124] Field implementation cases (all using solid slow-release scale inhibitor particles for oil and gas reservoir development prepared in Example 1)

[0125] The finished product produced according to Example 1 has been applied in the field to a current volume of 260 tons. The types of wells used include conventional newly developed oil wells, shale oil horizontal wells, old wells that have undergone repeated fracturing, shale oil exploratory wells, and coal gas wells. All construction processes have been successful and the scale prevention effect is good.

[0126] Field Application Case 1

[0127] The shale oil well, HX-XX, was designed with 49 fracturing stages, a horizontal stage length of 4035m, and a designed fluid volume of 50700m³. 3 The total designed sand volume (quartz sand) is 7720 m³. 3 The designed injection volume of anti-scaling microparticles was 4.8 tons, accounting for 0.077% (by volume) of the total sand volume. The actual fluid injected during fracturing was 51,751 m³. 3 The total amount of sand-carrying fluid and displacement fluid is approximately 11,040 m³. 3 .

[0128] Scale-inhibiting microparticles are uniformly mixed with small-sized quartz sand during the fracturing and proppant-carrying fluid stage, and then injected into the formation fractures together. No scale-inhibiting microparticles are added during the proppant-carrying and displacement fluid stages using large-sized quartz sand. In stages 1-2, 70 / 140 mesh quartz sand is uniformly mixed in; in stages 3-49, 40 / 70 mesh quartz sand is uniformly mixed in. The mixing ratio of quartz sand to quartz sand (by volume) is 0.09%-0.11%. The fracturing process proceeded smoothly without any abnormal fluctuations, and sufficient quantities were injected into the formation as designed.

[0129] After fracturing, the well was shut in for 24 days before fluid discharge began. On the 85th day after discharge, scale inhibitor particles at 38.2 mg / L were detected in the produced fluid, at which point the cumulative discharge volume was 1087 m³. 3 The drainage rate (cumulative drainage volume / total drainage volume) was 2.1%. As of the 331st day of continuous drainage, the cumulative drainage volume was 2000 m³. 3 The drainage rate (cumulative drainage volume / total liquid entering the ground) was 3.9%, and the average detected scale-inhibiting particles were 377.5 mg / L.

[0130] As of the 331st day of continuous drainage, the experimental well was producing normally, with no well repairs or shutdowns caused by scaling. The concentrations of scaling cations (calcium, magnesium, barium, and strontium) in the produced fluid of the experimental well were all higher than those of the nine adjacent wells in the same layer on the same platform and the clean water used during fracturing operations, indicating a good scale prevention effect.

[0131] Field Application Case 2

[0132] The old well, Luoping XX well, was repeatedly fractured. It was designed to fracture 19 stages with a designed fluid volume of 29,496 m³. 3 The total designed sand volume (quartz sand) is 2570m³. 3 The anti-scaling microparticles are designed to be added in a volume of 2.0 tons, accounting for 0.09% of the total sand volume (by volume).

[0133] During the fracturing and sand-carrying fluid construction stage, the scale-inhibiting microparticles were uniformly mixed with small-sized 40 / 70 mesh quartz sand at a volume ratio of 0.32% and entered the formation fractures together. The construction process was smooth, with no abnormal fluctuations in the fracturing process, and the required amount was injected into the formation in accordance with the construction design.

[0134] After fracturing, the well was shut in for 30 days before fluid discharge began. On the 42nd day after discharge, scale-inhibiting particles were detected in the produced fluid at a concentration of 46.5 mg / L, at which point the cumulative discharge volume was 1506 m³. 3 The drainage rate (cumulative drainage volume / total drainage volume) was 5.1%. As of the 220th day of continuous drainage, the cumulative drainage volume was 4163 m³. 3 The drainage rate (cumulative drainage volume / total liquid entering the ground) was 24.3%, and the average detected value of scale-inhibiting particles was 208 mg / L.

[0135] As of the 220th day of continuous drainage, the experimental well was producing normally, with no well repairs or shutdowns caused by scaling. The concentrations of scaling cations (calcium, magnesium, barium, and strontium) in the produced fluid of the experimental well were all higher than those of two adjacent wells in the same layer on the same platform and the clean water used during fracturing operations, indicating a good scale prevention effect.

[0136] Field Application Case 3

[0137] Shale oil exploratory well West XXXHX, designed with 18 fracturing stages, a horizontal stage length of 1300m, and 960m of pre-fracturing CO2. 3 Designed liquid volume 22404m³ 3 The total designed sand volume (quartz sand) is 2753.4 m³. 3 The anti-scaling microparticles are designed to be added in a volume of 1.534 tons, accounting for 0.07% of the total sand volume (by volume).

[0138] During the fracturing and sand-carrying fluid construction stage, the scale-inhibiting microparticles were uniformly mixed with 70 / 140 and 40 / 70 mesh quartz sand at a volume ratio of 0.09% and entered the formation fractures together. The construction process was smooth, with no abnormal fluctuations in fracturing, and the required amount was injected into the formation in accordance with the construction design.

[0139] Field Application Case 4

[0140] The coal and rock gas exploratory well, with a design fracturing stage of 15 sections, reached a final drilling depth of 4006m and a pre-drilling CO2 depth of 2680m. 3 The total designed sand volume (quartz sand) is 6100 m³. 3 The anti-scaling microparticles are designed to be added at a rate of 1.65 tons, accounting for 0.034% (by volume) of the total sand volume.

[0141] During the fracturing and sand-carrying fluid construction stage, the scale-inhibiting microparticles were uniformly mixed with 40 / 70 mesh quartz sand at a volume ratio of 0.15% and entered the formation fractures together. The construction process was smooth, with no abnormal fluctuations in the fracturing process, and the amount injected into the formation was sufficient as designed.

[0142] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A solid slow-release scale inhibitor microparticle for oil and gas reservoir development, characterized in that, It comprises the following components in parts by weight: 50-85 parts polyester slow-release carrier, 0.5-3 parts polyester modifier, and 12-49.5 parts scale inhibitor. The polyester slow-release carrier is a thermoplastic polyester; The thermoplastic polyester includes one or more of polyethylene terephthalate, polylactic acid, and polybutylene succinate; The polyester modifier comprises isophthalic acid, diethylene glycol, and polycarbodiimide, wherein the mass ratio of isophthalic acid, diethylene glycol, and polycarbodiimide is 0~0.4:0.1~0.8:0~0.8; The scale inhibitor includes one or more of ethylenediaminetetramethylenephosphonic acid, hexamethylenediaminetetramethylenephosphonic acid, disodium ethylenediaminetetraacetate, 2-phosphonobutane-1,2,4-tricarboxylic acid, and polyepoxysuccinic acid.

2. The solid slow-release scale inhibitor microparticles for oil and gas reservoir development according to claim 1, characterized in that, The thermoplastic polyester includes polyethylene terephthalate and polylactic acid, wherein the mass ratio of polyethylene terephthalate to polylactic acid in the thermoplastic polyester is 60~96:4~40.

3. The solid slow-release scale inhibitor particles for oil and gas reservoir development according to claim 1, characterized in that, The thermoplastic polyester includes polylactic acid and polybutylene succinate, wherein the mass ratio of polylactic acid to polybutylene succinate in the thermoplastic polyester is 90~95:5~10.

4. The solid slow-release scale inhibitor particles for oil and gas reservoir development according to claim 1, characterized in that, The thermoplastic polyester includes polyethylene terephthalate, polylactic acid, and polybutylene succinate, wherein the mass ratio of polyethylene terephthalate, polylactic acid, and polybutylene succinate in the thermoplastic polyester is 94~98:1~3:1~3.

5. The method for preparing solid slow-release scale inhibitor particles for oil and gas reservoir development according to any one of claims 1 to 4, characterized in that, Includes the following steps: The polyester slow-release carrier, polyester modifier and scale inhibitor are mixed and then granulated to obtain the solid slow-release scale inhibitor microparticles for oil and gas reservoir development.

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