In-situ thermally activated iron tailings-based all-solid waste oil well cement and its preparation and construction methods

Abstract

This invention relates to an in-situ thermally activated iron tailings-based all-solid waste oil well cement, its preparation, and construction method. The oil well cement is made from the following raw materials in parts by weight: 50-65 parts of pretreated primary iron tailings powder; 20-30 parts of graded and granulated blast furnace slag powder; 5-10 parts of stabilized steel slag powder; 4-8 parts of graded and granulated desulfurized gypsum; 1-3 parts of anhydrous sodium sulfate; 0.5-2 parts of sodium carbonate; 1-1.5 parts of functional additives; 0.08-0.15 parts of organic-inorganic composite corrosion inhibitor; 0.1-0.3 parts of composite dispersible nanocrystalline nucleating agent; and 1-3 parts of trace non-alkali activator solid masterbatch. This invention solves the problems of uncontrollable in-situ activation, poor construction adaptability, and high-temperature strength reduction in existing technologies, and can be widely applied to cementing projects for various oil wells, including low-temperature wells, conventional wells, and thermal recovery wells.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to an in-situ thermally activated iron tailings-based all-solid waste oil well cement and its preparation and construction methods. Background Technology

[0002] Cementing is a crucial step in oil drilling engineering. Its core function is to inject cement slurry to form a dense, high-strength, high-temperature-resistant cement paste between the wellbore and casing, thereby stabilizing the wellbore and isolating oil and gas. Currently, the widely used industrial oil well cement primarily uses silicate cement clinker as its raw material. However, its production process requires calcination at temperatures above 1450℃, resulting in extremely high energy consumption and significant carbon dioxide emissions.

[0003] Iron tailings are industrial solid waste generated during iron ore mining and beneficiation, with global annual emissions exceeding hundreds of millions of tons and low comprehensive utilization rates. Existing technologies have attempted to use iron tailings in the preparation of building materials, but most require high-temperature calcination pretreatment, resulting in high energy consumption and costs. While alkali activation technology can utilize iron tailings at room temperature, it presents the following technical problems: First, high alkalinity can severely corrode oil well casing, shortening the service life of oil and gas wells, and may also trigger alkali-aggregate reactions, leading to cement stone cracking and reduced strength; second, alkali activators are highly corrosive and hygroscopic, posing safety hazards during storage, transportation, and on-site use; third, in high-temperature oil well environments, the gelling products formed by alkali activation are easily decomposed, leading to strength reduction and failing to meet the cementing requirements of thermal recovery wells.

[0004] Therefore, developing an oil well cement that requires no high-temperature pretreatment, is free from alkali corrosion, is composed entirely of solid waste, and is suitable for a wide temperature range of oil wells is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The present invention aims to overcome the shortcomings of the prior art and provides an in-situ thermally activated iron tailings-based all-solid waste oil well cement and its preparation and construction methods.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In-situ thermally activated iron tailings-based all-solid waste oil well cement, wherein the oil well cement is made from the following raw materials in parts by weight:

[0008] Pre-treat 50-65 parts of primary iron tailings powder;

[0009] 20-30 parts of graded and granulated blast furnace slag powder;

[0010] Stabilized steel slag powder 5-10 parts;

[0011] Graded and ground desulfurized gypsum 4-8 parts;

[0012] 1-3 parts anhydrous sodium sulfate;

[0013] Sodium carbonate 0.5-2 parts;

[0014] 1-1.5 parts of functional admixture;

[0015] 0.08-0.15 parts of organic-inorganic composite corrosion inhibitor;

[0016] 0.1-0.3 parts of composite dispersible nanocrystalline nucleating agent;

[0017] 1-3 parts of trace non-alkali activator solid masterbatch;

[0018] The oil well cement does not contain alkali metal hydroxides or alkali metal silicate activators;

[0019] When the oil well cement is used for cementing oil wells, it undergoes in-situ thermal activation and hydration reactions in an environment of 80-350℃ downhole.

[0020] Specifically, the pretreated primary iron tailings powder has an iron mass fraction ≤8%, a moisture content ≤1.0%, and a specific surface area of ​​350-450 m². 2 / kg, and the batch fluctuation of the main chemical components of SiO2 and Al2O3 is ≤1.5%; the pretreatment method of the pretreated primary iron tailings powder includes the following steps:

[0021] S1. Combined iron removal: Iron removal is achieved by combining a permanent magnet drum and a high-frequency vibrating screen. The magnetic field strength of the permanent magnet drum is 0.15-0.25T, the frequency of the high-frequency vibrating screen is 30-50Hz, and the screen aperture is 0.075-0.15mm.

[0022] S2. Low-temperature drying and pre-activation: Under normal pressure, dry at 150℃ for 30 minutes;

[0023] S3, Mechanochemical-Microwave Assisted Activation: Under normal pressure conditions, mechanochemical and microwave synergistic activation is adopted. The mechanochemical activation speed is 300-500 r / min, the microwave power is 800-1200W, the frequency is 2450MHz, and the total activation time is 5-10 min.

[0024] S4. Grading and grinding: Closed-circuit grinding with ball mill and classifier for 30-60 minutes;

[0025] S5. Closed-loop homogenization: The sample is fed into a continuous homogenization chamber and homogenized for ≥2 hours under normal pressure and closed environment.

[0026] Specifically, the stabilized steel slag powder has an f-CaO content ≤ 1.5% and an f-MgO content ≤ 3%; the stabilization pretreatment method for the stabilized steel slag powder includes the following steps:

[0027] P1. Coarse grinding of steel slag: Raw steel slag is ground using a ball mill to a specific surface area of ​​200-250 m². 2 / kg, to remove large pieces of metallic iron and coarse aggregate from steel slag;

[0028] P2. Aging treatment: The ground steel slag is naturally aged in a closed silo at 20±5℃ for ≥12h.

[0029] P3. Addition of composite stabilizer: Add 2%-5% of the composite stabilizer by mass to the aged steel slag. The composite stabilizer is a mixture of industrial grade lime and industrial gypsum in a mass ratio of 1:1-1:2.

[0030] P4. Maturation and stabilization treatment: The steel slag with added composite stabilizer is left to stand in a closed environment at 20±5℃ for 24 hours.

[0031] Specifically, the graded and granulated blast furnace slag powder and the graded and granulated desulfurized gypsum are respectively graded and ground until the absolute deviation of their specific surface area from that of the pretreated primary iron tailings powder is ≤20m². 2 / kg, and the batch fluctuation of their respective main chemical components of SiO2, Al2O3, and CaO is ≤1.5%.

[0032] Specifically, the composite dispersible nanocrystalline nucleating agent is: a compound of nano-SiO2 with hydrophobic modification of the surface of a silane coupling agent and talc; or a compound of nano-Al2O3 with hydrophobic modification of the surface of a silane coupling agent and talc.

[0033] Specifically, in the trace non-alkali activator solid masterbatch, the effective mass fraction of the trace non-alkali activator is 10%, and the trace non-alkali activator is a fluorosilicate or a phosphate.

[0034] Specifically, the functional additive consists of a base component and optional components;

[0035] The basic components include: 0.2-0.4 parts of citric acid or boric acid retarder, 0.4-0.6 parts of polyacrylamide or cellulose-based water loss reducing agent, and 0.1-0.5 parts of naphthalene-based or melamine-based high-temperature dispersant;

[0036] The optional components are any one of the following: 0.2-0.4 parts of calcium aluminate-based low-temperature early strength agent and 0.2-0.4 parts of high-temperature stabilizer obtained by compounding zircon sand powder and silica fume in a mass ratio of 1:1.

[0037] Specifically, the oil well cement is classified into the following three categories according to well temperature:

[0038] Low-temperature type: suitable for well temperatures of 80-120℃, the functional admixture includes the low-temperature early strength agent;

[0039] Medium-temperature type: suitable for well temperatures greater than 120℃ and not exceeding 300℃, and the functional admixture does not contain the low-temperature early-strength agent and the high-temperature stabilizer;

[0040] High-temperature type: suitable for well temperatures greater than 300℃ and not exceeding 350℃, the functional additives include the high-temperature stabilizer; the oil well cement also contains 0.2 parts of basalt fiber and 0.3 parts of elastic microspheres.

[0041] A method for preparing in-situ thermally activated iron tailings-based all-solid waste oil well cement includes the following steps:

[0042] Y1. Raw material pretreatment:

[0043] Preparation of pretreated primary iron tailings powder;

[0044] Stabilized steel slag powder was prepared and graded and milled until the absolute deviation of its specific surface area from that of the pretreated primary iron tailings powder was ≤20 μm. 2 / kg, followed by homogenization;

[0045] Granulated blast furnace slag powder and desulfurized gypsum are separately graded and ground until the absolute deviation of their specific surface area from that of the pretreated primary iron tailings powder is ≤20m². 2 / kg, and then homogenized separately;

[0046] The composite dispersed nanocrystalline nucleating agent, the trace non-alkali activator solid masterbatch, the functional additive, and the organic-inorganic composite corrosion inhibitor are premixed at 20±5℃ and 100-150r / min for 5-10min.

[0047] Y2. Preparation of dry powder: Add all raw materials into a horizontal dry mixing equipment and stir at 150-200 r / min for 15-20 min to obtain dry powder;

[0048] Y3. Packaging: The dry powder is packaged in a moisture-proof and sealed container to obtain the finished oil well cement product.

[0049] A method for cementing in-situ thermally activated iron tailings-based fully solidified waste oil wells includes the following steps:

[0050] N1. Select low-temperature, medium-temperature, or high-temperature oil well cement according to the downhole temperature of the oil well;

[0051] N2. Mix the oil well cement with water at a water-to-solid ratio of 0.45 and stir for 2-5 minutes to obtain cement slurry;

[0052] N3. The cement slurry is pumped into the annulus of the oil well. Relying on the high temperature environment of 80-350℃ downhole, the in-situ thermal activation and hydration reaction are completed to form cement stone.

[0053] The core mechanism of this invention is the combined effect of "low-temperature pre-activation, high-temperature in-situ thermal activation downhole, composite chemical activation of pure salt-crystal nuclei-trace non-alkali activator (masterbatch premix), and synergistic effect of raw material stabilization," as detailed below:

[0054] 1. Low-temperature pre-activation and in-situ high-temperature thermal activation mechanism in oil wells: The continuous high-temperature environment of 80-350℃ in oil wells is equivalent to a "mobile activation furnace," which can generate thermal vibration on the primary iron tailings, destroying the stable Si-O and Al-O covalent bonds inside, causing the crystal structure of the iron tailings to transform into a metastable state, undergoing a depolymerization reaction, and releasing active SiO2 and Al2O3, providing sufficient active components for the gelation reaction; combined with low-temperature drying pre-activation (30 min at 150℃), the dependence on the high temperature in the well is reduced, and the activation can be guaranteed even if the well temperature fluctuates. The high temperature accelerates the ion dissociation and diffusion rate of the salt activator, significantly increasing the activation reaction rate and compensating for the insufficient activation intensity of pure salt activation at room temperature. Combined with mechanochemical-microwave-assisted activation pretreatment, the intrinsic activity of iron tailings is further enhanced, and normal hydration can be achieved at a minimum temperature of 80℃. For different temperature ranges, the activation efficiency and hydration rate are precisely matched by pre-formed dry powder, the addition of low-temperature early strength agent, and the combination of zircon sand micro powder and silica fume compound high-temperature stabilizer, avoiding insufficient activation at low temperatures and strength reduction at high temperatures, and ensuring long-term high-temperature performance.

[0055] 2. Pure salt-crystal nucleus-trace non-alkali activator (masterbatch premix) composite activation mechanism: SO4 dissociated from sulfate activators (desulfurized gypsum, anhydrous sodium sulfate) 2- The Ca released from granulated blast furnace slag powder and steel slag powder in the system 2+ Al 3+ The reaction produces high-temperature stable hydrated calcium sulfoaluminate (AFt / AFm), a mineral phase that can fill the pores of cement stone, improving its strength and density; the CO3 released from the carbonate activator (sodium carbonate) 2- On the one hand, it can regulate the hydration rate of the system, preventing the cement paste from setting too early due to excessively rapid hydration reaction; on the other hand, it can react with Ca... 2+The reaction produces calcium carbonate, further optimizing the microstructure of the cement stone and improving its high-temperature resistance and corrosion resistance. A composite dispersible nanocrystalline nucleating agent (hydrophobically modified nano-SiO2, Al2O3, talc) provides the hydration reaction nuclei at room temperature, activating the hydration process, preventing dry powder agglomeration, exhibiting low moisture absorption and strong stability, reducing dependence on downhole high temperatures, and solving the problem of room-temperature inertia caused by pure salt activation. A trace amount of non-alkali activator (fluorosilicate / phosphate) is formulated into a 10% concentration solid masterbatch, with no industrial measurement error, further improving room-temperature activation efficiency without altering the near-neutral / weakly alkaline properties of the system (pH 9.5±0.3), eliminating the risk of alkali corrosion and alkali-aggregate reaction. By optimizing the dosage ratio of activator, nucleating agent, and trace non-alkali activator, the problems of insufficient pure salt activation efficiency and room-temperature inertia are solved, while simultaneously controlling SO4 levels. 2- To control the content and avoid the risk of sulfate erosion and expansion.

[0056] 3. Raw Material Stabilization Synergistic Mechanism: By using permanent magnet drums and high-frequency vibrating screens for combined iron removal, low-temperature drying pre-activation, mechanochemical-microwave assisted activation, and continuous homogenization chamber closed-loop homogenization treatment for iron tailings, the intrinsic activity of iron tailings is improved, and the problems of large fluctuations in composition and interference of iron oxides with hydration are solved, making it suitable for industrial batch production. By using steel slag grinding, aging, and composite stabilizer maturation treatment (industrial-grade lime and gypsum compound) for steel slag, the potential for later expansion is completely eliminated, the treatment cycle is shortened, no CO2 gas source is required, and industrial feasibility is improved. Granulated blast furnace slag powder, desulfurization gypsum and other solid wastes are graded, ground and homogenized, and their properties are matched with iron tailings powder to ensure uniform mixing and stable performance of each raw material. At the same time, general-purpose grinding equipment is used to reduce grinding energy consumption. The above-mentioned raw material processing methods, together with the in-situ thermal activation and composite activation system, work synergistically to enable the entire solid waste system to rapidly and stably hydrate and harden, forming cement stone that meets the requirements of oil well cementing. This eliminates the need for cement clinker and alkali activators, achieving the goal of low-carbon, environmentally friendly, and low-cost cementing.

[0057] The beneficial effects of this invention are:

[0058] Alkali-free design: Completely eliminates alkali activators, thoroughly solving the problems of casing corrosion, safety hazards and high-temperature strength reduction caused by alkali activation. It is environmentally friendly and suitable for on-site construction requirements in oil fields.

[0059] In-situ thermal activation: Iron tailings do not undergo any high-temperature calcination pretreatment. Instead, they are thermally activated and depolymerized in situ using the high-temperature environment of the oil well, replacing the traditional high-temperature pretreatment in factories and significantly reducing energy consumption and production costs.

[0060] Solid waste resource utilization: Using raw iron tailings as the main raw material, combined with granulated blast furnace slag powder, steel slag powder, desulfurization gypsum and other industrial solid wastes, without any silicate cement clinker, to achieve 100% resource utilization of industrial solid waste, which is low-carbon and environmentally friendly.

[0061] Wide temperature range adaptability: By adjusting the functional additives in the formula (low-temperature early strength agent or high-temperature stabilizer), it can be adapted to three well temperature conditions of 80-120℃, 120-300℃, and 300-350℃ respectively, avoiding the problems of slow solidification at low temperature and strength shrinkage at high temperature, and meeting the cementing needs of different oil wells. Detailed Implementation

[0062] The present invention will be further described below with reference to embodiments:

[0063] In-situ thermally activated iron tailings-based all-solid waste oil well cement, wherein the oil well cement is made from the following raw materials in parts by weight:

[0064] 50-65 parts of pretreated primary iron tailings powder; wherein, the pretreated primary iron tailings powder has an iron mass fraction ≤8%, a moisture content ≤1.0%, and a specific surface area of ​​350-450 m². 2 / kg, and the batch fluctuation of the main chemical components of SiO2 and Al2O3 is ≤1.5%; the pretreatment method of the pretreated primary iron tailings powder includes the following steps:

[0065] S1. Combined iron removal: Iron removal is achieved by combining a permanent magnet drum and a high-frequency vibrating screen. The magnetic field strength of the permanent magnet drum is 0.15-0.25T, the frequency of the high-frequency vibrating screen is 30-50Hz, and the screen aperture is 0.075-0.15mm.

[0066] S2. Low-temperature drying and pre-activation: Under normal pressure, dry at 150℃ for 30 minutes;

[0067] S3, Mechanochemical-Microwave Assisted Activation: Under normal pressure conditions, mechanochemical and microwave synergistic activation is adopted. The mechanochemical activation speed is 300-500 r / min, the microwave power is 800-1200W, the frequency is 2450MHz, and the total activation time is 5-10 min.

[0068] S4. Grading and grinding: Closed-circuit grinding with ball mill and classifier for 30-60 minutes;

[0069] S5. Closed-loop homogenization: The sample is fed into a continuous homogenization chamber and homogenized for ≥2 hours under normal pressure and closed environment.

[0070] 5-10 parts of stabilized steel slag powder; wherein, the f-CaO content in the stabilized steel slag powder is ≤1.5% and the f-MgO content is ≤3%; the stabilization pretreatment method for the stabilized steel slag powder includes the following steps:

[0071] P1. Coarse grinding of steel slag: Raw steel slag is ground using a ball mill to a specific surface area of ​​200-250 m². 2 / kg, to remove large pieces of metallic iron and coarse aggregate from steel slag;

[0072] P2. Aging treatment: The ground steel slag is naturally aged in a closed silo at 20±5℃ for ≥12h.

[0073] P3. Addition of composite stabilizer: Add 2%-5% of the composite stabilizer by mass to the aged steel slag. The composite stabilizer is a mixture of industrial grade lime and industrial gypsum in a mass ratio of 1:1-1:2.

[0074] P4. Maturation and stabilization treatment: The steel slag with added composite stabilizer is left to stand in a closed environment at 20±5℃ for 24 hours.

[0075] 20-30 parts of graded and granulated blast furnace slag powder; 4-8 parts of graded and granulated desulfurized gypsum; wherein the graded and granulated blast furnace slag powder and the graded and granulated desulfurized gypsum are respectively graded and granulated until the absolute deviation of their specific surface area from that of the pretreated primary iron tailings powder is ≤20 μm. 2 / kg, and the batch fluctuation of their respective main chemical components of SiO2, Al2O3, and CaO is ≤1.5%.

[0076] 1-3 parts anhydrous sodium sulfate; 0.5-2 parts sodium carbonate; 0.08-0.15 parts organic-inorganic composite corrosion inhibitor.

[0077] 1-1.5 parts of functional admixture; wherein the functional admixture is composed of a basic component and optional components;

[0078] The basic components include: 0.2-0.4 parts of citric acid or boric acid retarder, 0.4-0.6 parts of polyacrylamide or cellulose-based water loss reducing agent, and 0.1-0.5 parts of naphthalene-based or melamine-based high-temperature dispersant;

[0079] The optional components are any one of the following: 0.2-0.4 parts of calcium aluminate-based low-temperature early strength agent and 0.2-0.4 parts of high-temperature stabilizer obtained by compounding zircon sand powder and silica fume in a mass ratio of 1:1.

[0080] 0.1-0.3 parts of composite dispersible nanocrystalline nucleating agent; wherein the composite dispersible nanocrystalline nucleating agent is: a compound of nano-SiO2 modified with silane coupling agent and talc powder; or a compound of nano-Al2O3 modified with silane coupling agent and talc powder.

[0081] 1-3 parts of trace non-alkali activator solid masterbatch; wherein, in the trace non-alkali activator solid masterbatch, the effective mass fraction of trace non-alkali activator is 10%, and the trace non-alkali activator is fluorosilicate or phosphate.

[0082] The oil well cement does not contain alkali metal hydroxides or alkali metal silicate activators; when the oil well cement is used for oil well cementing, it completes in-situ thermal activation and hydration reactions in an environment of 80-350℃ downhole.

[0083] The oil well cement is classified into the following three categories according to the well temperature:

[0084] Low-temperature type: suitable for well temperatures of 80-120℃, the functional admixture includes the low-temperature early strength agent;

[0085] Medium-temperature type: suitable for well temperatures greater than 120℃ and not exceeding 300℃, and the functional admixture does not contain the low-temperature early-strength agent and the high-temperature stabilizer;

[0086] High-temperature type: suitable for well temperatures greater than 300℃ and not exceeding 350℃, the functional additives include the high-temperature stabilizer; the oil well cement also contains 0.2 parts of basalt fiber and 0.3 parts of elastic microspheres.

[0087] A method for preparing in-situ thermally activated iron tailings-based all-solid waste oil well cement includes the following steps:

[0088] Y1. Raw material pretreatment:

[0089] Preparation of pretreated primary iron tailings powder;

[0090] Stabilized steel slag powder was prepared and graded and milled until the absolute deviation of its specific surface area from that of the pretreated primary iron tailings powder was ≤20 μm. 2 / kg, followed by homogenization;

[0091] Granulated blast furnace slag powder and desulfurized gypsum are separately graded and ground until the absolute deviation of their specific surface area from that of the pretreated primary iron tailings powder is ≤20m². 2 / kg, and then homogenized separately;

[0092] The composite dispersed nanocrystalline nucleating agent, the trace non-alkali activator solid masterbatch, the functional additive, and the organic-inorganic composite corrosion inhibitor are premixed at 20±5℃ and 100-150r / min for 5-10min.

[0093] Y2. Preparation of dry powder: Add all raw materials into a horizontal dry mixing equipment and stir at 150-200 r / min for 15-20 min to obtain dry powder;

[0094] Y3. Packaging: The dry powder is packaged in a moisture-proof and sealed container to obtain the finished oil well cement product.

[0095] A method for cementing in-situ thermally activated iron tailings-based fully solidified waste oil wells includes the following steps:

[0096] N1. Select low-temperature, medium-temperature, or high-temperature oil well cement according to the downhole temperature of the oil well;

[0097] N2. Mix the oil well cement with water at a water-to-solid ratio of 0.45 and stir for 2-5 minutes to obtain cement slurry;

[0098] N3. The cement slurry is pumped into the annulus of the oil well. Relying on the high temperature environment of 80-350℃ downhole, the in-situ thermal activation and hydration reaction are completed to form cement stone.

[0099] Example 1: Conventional medium-temperature well application (applicable well temperatures 120-300℃)

[0100] In-situ thermally activated iron tailings-based all-solid waste oil well cement is produced from the following raw materials in parts by weight: 55 parts pretreated primary iron tailings powder, 25 parts graded and granulated blast furnace slag powder, 8 parts stabilized steel slag powder, 6 parts graded and granulated desulfurized gypsum, 2 parts anhydrous sodium sulfate, 1 part sodium carbonate, functional additives (0.3 parts citric acid retarder, 0.5 parts polyacrylamide-based water loss reducer, 0.2 parts naphthalene-based high-temperature dispersant), 0.1 parts organic-inorganic composite corrosion inhibitor, 0.2 parts composite dispersible nanocrystalline nucleating agent (compound of surface-hydrophobic modified nano-SiO2 and talc), and 2 parts trace non-alkali activator solid masterbatch (fluorosilicate, 10% concentration masterbatch). All raw materials are continuously homogenized in a closed-loop homogenization chamber, with a composition fluctuation of ≤1.5%.

[0101] Oil well cement preparation:

[0102] Y1. Raw material pretreatment: Pretreated primary iron tailings powder was prepared. 55 parts of primary iron tailings were subjected to iron removal by a combination of permanent magnet drum and high-frequency vibrating screen, low-temperature drying and pre-activation (150℃ for 30 min), mechanochemical-microwave assisted activation for 10 min, and graded grinding to a specific surface area of ​​400 m². 2 / kg, continuous homogenization chamber closed-loop homogenization for 2.5h;

[0103] Stabilized steel slag powder was prepared by grinding, aging, and stabilizing with a composite stabilizer for 24 hours. It was then stabilized with industrial-grade lime and gypsum, with f-CaO=1.2% and f-MgO=2.8%. The slag was then graded and ground together with granulated blast furnace slag powder and desulfurized gypsum to achieve the same specific surface area, and then homogenized.

[0104] The composite dispersion nanocrystal nucleating agent, trace amount of non-alkali activator solid masterbatch, functional additive, and organic-inorganic composite corrosion inhibitor were premixed for 5-10 min at 20±5℃ and 100-150 r / min.

[0105] Y2. Preparation of dry powder: Add all raw materials to a horizontal dry mixing equipment and stir at 180 r / min for 18 min. The mixing uniformity is 96%, and dry powder is obtained.

[0106] Y3. Packaging: Double-layer moisture-proof and sealed packaging with a film-coated woven bag and an aluminum-plastic inner bag (with built-in desiccant) is used to obtain medium-temperature set dry powder. The moisture absorption rate is tested to be 0.6%. After the cement slurry water loss, thickening time and free liquid content meet the standards, it is shipped out and a 3-month turnover inventory is maintained.

[0107] Cementing of oil wells: On-site, a fully automatic slurry mixing station common in oilfields was used. Water was added at a water-to-solid ratio of 0.45, and the mixture was stirred for 3 minutes using conventional oilfield mixing equipment to prepare cement slurry. The results showed: water loss of 36 mL, thickening time of 110 min, free fluid of 0.3%, high pressure resistance of 18.2 MPa, and H2S / CO2 erosion resistance meeting the standards. The cement slurry was pumped into the annulus of the oil well at a temperature of 100℃ using a temperature-segmented pumping process, with real-time monitoring of the activation status, which showed normal activation.

[0108] Performance test results: After curing at 100℃ for 24 hours, the compressive strength is 16.8 MPa; after curing at 150℃ for 24 hours, the compressive strength is 18.2 MPa; API fluid loss is 36 mL; thickening time is 110 min; free fluid is 0.3%; no corrosion to P110 casing; no significant shrinkage; acoustic variable density logging adhesive bonding pass rate is 98.5%; after 3 months of curing, the compressive strength is 20.1 MPa; after 1 year of curing, the compressive strength is 21.5 MPa; after 5 years of curing, the compressive strength is 20.8 MPa; the strength decay in the simulated 20-year accelerated aging test is ≤8%; after 50 cycles of hot and cold cycling (-20℃-150℃), there are no cracks and the strength decay is ≤5%.

[0109] Example 2: High-temperature wells for thermal recovery (applicable well temperatures 300-350℃)

[0110] In-situ thermally activated iron tailings-based all-solid waste oil well cement, wherein the oil well cement is made from the following raw materials in parts by weight: 50 parts of pretreated primary iron tailings powder, 28 parts of graded and granulated blast furnace slag powder, 10 parts of stabilized steel slag powder, 7 parts of graded and granulated desulfurized gypsum, 3 parts of anhydrous sodium sulfate, 1.5 parts of sodium carbonate, functional admixtures (0.4 parts of boric acid retarder, 0.6 parts of cellulose-based water loss reducer, 0.5 parts of melamine-based high-temperature dispersant, 0.3 parts of zircon sand micro powder and silica fume compound high-temperature stabilizer (1:1), 0.15 parts of organic-inorganic composite corrosion inhibitor, 0.3 parts of composite dispersible nanocrystalline nucleating agent (compound of surface hydrophobic modified nano SiO2 and talc powder), 3 parts of trace non-alkali activator solid masterbatch (phosphate, 10% concentration masterbatch), 0.2 parts of basalt fiber, and 0.3 parts of elastic microspheres. All raw materials undergo continuous homogenization in a closed-loop homogenization chamber, with composition fluctuations ≤1.5%.

[0111] Oil well cement preparation:

[0112] Y1. Raw material pretreatment: Pretreated primary iron tailings powder was prepared by passing 50 parts of primary iron tailings through a combination of permanent magnet drum and high-frequency vibrating screen for iron removal, low-temperature drying and pre-activation (150℃ for 30 min), mechanochemical-microwave assisted activation for 8 min, and graded grinding to a specific surface area of ​​450 m². 2 / kg, continuous homogenization chamber closed-loop homogenization for 3 hours;

[0113] Stabilized steel slag powder was prepared by grinding, aging, and stabilizing with a composite stabilizer for 24 hours. It was then stabilized with industrial-grade lime and gypsum, with f-CaO=1.3% and f-MgO=2.9%. The slag was then graded and ground together with granulated blast furnace slag powder and desulfurized gypsum to achieve the same specific surface area, and then homogenized.

[0114] The composite dispersion nanocrystal nucleating agent, trace amount of non-alkali activator solid masterbatch, functional additives, organic-inorganic composite corrosion inhibitor, basalt fiber, and elastic microspheres were premixed for 5-10 min at 20±5℃ and 100-150 r / min.

[0115] Y2. Preparation of dry powder: Add all raw materials to a horizontal dry mixing equipment and stir at 200 r / min for 20 min until the mixing uniformity is 97% to obtain dry powder.

[0116] Y3. Packaging: Double-layer moisture-proof and sealed packaging with a film-coated woven bag and an aluminum-plastic inner bag (with built-in desiccant) is used to obtain high-temperature shaped dry powder. The moisture absorption rate is tested to be 0.5%. After the cement slurry water loss, thickening time and free liquid content meet the standards, it is shipped out and a 3-month turnover inventory is maintained.

[0117] Cementing of oil wells: On-site, a fully automatic slurry mixing station common in oilfields was used. Water was added at a water-to-solid ratio of 0.45, and the mixture was stirred for 4 minutes using conventional oilfield mixing equipment to prepare cement slurry. The results showed: water loss of 42 mL, thickening time of 150 min, free fluid of 0.2%, high pressure resistance of 22.5 MPa, and H2S / CO2 erosion resistance meeting the standards. The cement slurry was pumped into the annulus of the oil well at a temperature of 250℃ using a temperature-segmented pumping process, with real-time monitoring of the activation status, which showed normal activation. A 1000-hour thermal stability test at 350℃ was also conducted, and the performance met the standards.

[0118] Performance test results: 20.5 MPa compressive strength after 24 hours of curing at 200℃, 22.3 MPa after 24 hours of curing at 250℃, and 21.8 MPa after 72 hours of curing at 300℃, with no strength shrinkage; API water loss of 42 mL, thickening time of 150 min, free fluid of 0.2%, excellent high-temperature stability, and meeting the interfacial bonding strength standard; 99% pass rate for acoustic variable density logging adhesive; 23.1 MPa compressive strength after 3 months of curing, 24.5 MPa after 1 year of curing, and 23.8 MPa after 5 years of curing; strength attenuation ≤7% after 20 years of accelerated aging test; no cracks and strength attenuation ≤4% after 50 cycles of hot and cold cycling (-20℃ to 300℃).

[0119] Example 3: Low-temperature well application (applicable well temperature 80~120℃)

[0120] In-situ thermally activated iron tailings-based all-solid waste oil well cement is produced from the following raw materials in parts by weight: 65 parts pretreated primary iron tailings powder, 20 parts graded and granulated blast furnace slag powder, 5 parts stabilized steel slag powder, 4 parts graded and granulated desulfurized gypsum, 1 part anhydrous sodium sulfate, 0.5 parts sodium carbonate, functional additives (0.2 parts citric acid retarder, 0.4 parts polyacrylamide-based water loss reducer, 0.1 parts naphthalene-based high-temperature dispersant, 0.3 parts calcium aluminate-based low-temperature early strength agent), 0.08 parts organic-inorganic composite corrosion inhibitor, 0.1 parts composite dispersible nanocrystalline nucleating agent (compound of surface-hydrophobic modified nano-SiO2 and talc), and 1 part trace non-alkali activator solid masterbatch (fluorosilicate, 10% concentration masterbatch). All raw materials are continuously homogenized in a closed-loop homogenization chamber with a composition fluctuation of ≤1.5%.

[0121] Oil well cement preparation:

[0122] Y1. Raw material pretreatment: Pretreated primary iron tailings powder was prepared by passing 65 parts of primary iron tailings through a combination of permanent magnet drum and high-frequency vibrating screen for iron removal, low-temperature drying and pre-activation (150℃ for 30 min), mechanochemical-microwave assisted activation for 5 min, and graded grinding to a specific surface area of ​​350 m². 2 / kg, continuous homogenization chamber closed-loop homogenization for 2 hours;

[0123] Stabilized steel slag powder was prepared by grinding, aging, and stabilizing with a composite stabilizer for 24 hours. It was then stabilized with industrial-grade lime and gypsum, with f-CaO=1.1% and f-MgO=2.7%. The slag was then graded and ground together with granulated blast furnace slag powder and desulfurized gypsum to achieve the same specific surface area, and then homogenized.

[0124] The composite dispersion nanocrystal nucleating agent, trace amount of non-alkali activator solid masterbatch, functional additive, and organic-inorganic composite corrosion inhibitor were premixed for 5-10 min at 20±5℃ and 100-150 r / min.

[0125] Y2. Preparation of dry powder: Add all raw materials to a horizontal dry mixing equipment and stir at 150 r / min for 15 min until the mixing uniformity is 95% to obtain dry powder.

[0126] Y3. Packaging: Double-layer moisture-proof and sealed packaging with a film-coated woven bag and an aluminum-plastic inner bag (with built-in desiccant) is used to obtain low-temperature shaped dry powder. The moisture absorption rate is tested to be 0.7%. After the cement slurry water loss, thickening time and free liquid content meet the standards, it is shipped out and is kept in a 3-month turnover inventory.

[0127] Cementing of oil wells: On-site, a fully automatic slurry mixing station common in oilfields was used. Water was added at a water-to-solid ratio of 0.45, and the mixture was stirred for 5 minutes using conventional oilfield mixing equipment to prepare cement slurry. The test results showed: water loss of 48 mL, thickening time of 60 min, free fluid of 0.4%, high pressure resistance of 15.3 MPa, and H2S / CO2 erosion resistance meeting the standards. The cement slurry was pumped into the annulus of the oil well at a temperature of 80℃, using a temperature-segmented pumping process. The activation status was monitored in real time, and the activation was normal.

[0128] Performance test results: After curing at 80℃ for 24 hours, the compressive strength is 13.5 MPa; after curing at 80℃ for 72 hours, the compressive strength is 18.6 MPa; API fluid loss is 48 mL; thickening time is 60 min; free fluid is 0.4%, meeting the requirements for low-temperature well cementing; the sonic variable density logging shows a cement bond pass rate of 98%; after 3 months of curing, the compressive strength is 19.2 MPa; after 1 year of curing, the compressive strength is 20.3 MPa; after 5 years of curing, the compressive strength is 19.8 MPa; the strength decay in the simulated 20-year accelerated aging test is ≤9%; after 50 cycles of hot and cold cycling (-20℃-100℃), there are no cracks and the strength decay is ≤6%.

[0129] The cement slurry of this invention, after curing at 80-350℃, achieves a compressive strength of 13.5-22.3 MPa (24 h), API water loss ≤48 mL, thickening time adjustable from 60-150 min, free fluid ≤0.4%, and no corrosion to P110 casing. It exhibits excellent long-term durability, with a strength decay of ≤9% in a simulated 20-year accelerated aging test, and no cracking or strength decay of ≤6% after 50 cycles of hot and cold cycling. This invention solves the problems of uncontrollable in-situ activation, poor construction adaptability, and high-temperature strength reduction in existing technologies, and can be widely applied to cementing engineering of various oil wells, including cryogenic wells, conventional wells, and thermal recovery wells.

[0130] The present invention has been described above by way of example. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any improvements made by adopting the inventive concept and technical solution of the present invention, or direct application to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. In-situ thermally activated iron tailings-based all-solid waste oil well cement, characterized in that, The oil well cement is made from the following raw materials in parts by weight: Pre-treat 50-65 parts of primary iron tailings powder; 20-30 parts of graded and granulated blast furnace slag powder; Stabilized steel slag powder 5-10 parts; Graded and ground desulfurized gypsum 4-8 parts; 1-3 parts anhydrous sodium sulfate; Sodium carbonate 0.5-2 parts; 1-1.5 parts of functional admixture; 0.08-0.15 parts of organic-inorganic composite corrosion inhibitor; 0.1-0.3 parts of composite dispersible nanocrystalline nucleating agent; 1-3 parts of trace non-alkali activator solid masterbatch; The oil well cement does not contain alkali metal hydroxides or alkali metal silicate activators; When the oil well cement is used for oil well cementing, it undergoes in-situ thermal activation and hydration reactions in an environment of 80-350℃ downhole. The pretreated primary iron tailings powder has an iron mass fraction ≤8%, a moisture content ≤1.0%, and a specific surface area of ​​350-450 m². 2 / kg, and the batch fluctuation of the main chemical components of SiO2 and Al2O3 is ≤1.5%; the pretreatment method of the pretreated primary iron tailings powder includes the following steps: S1. Combined iron removal: Iron removal is achieved by combining a permanent magnet drum and a high-frequency vibrating screen. The magnetic field strength of the permanent magnet drum is 0.15-0.25T, the frequency of the high-frequency vibrating screen is 30-50Hz, and the screen aperture is 0.075-0.15mm. S2. Low-temperature drying and pre-activation: Under normal pressure, dry at 150℃ for 30 minutes; S3, Mechanochemical-Microwave Assisted Activation: Under normal pressure conditions, mechanochemical and microwave synergistic activation is adopted. The mechanochemical activation speed is 300-500 r / min, the microwave power is 800-1200W, the frequency is 2450MHz, and the total activation time is 5-10 min. S4. Grading and grinding: Closed-circuit grinding with ball mill and classifier for 30-60 minutes; S5. Closed-loop homogenization: The sample is fed into a continuous homogenization chamber and the closed-loop homogenization time is ≥2h under normal pressure and closed environment. The composite dispersible nanocrystalline nucleating agent is: a compound of nano-SiO2 modified with a silane coupling agent and talc powder; or a compound of nano-Al2O3 modified with a silane coupling agent and talc powder. In the trace non-alkali activator solid masterbatch, the trace non-alkali activator is fluorosilicate or phosphate; The functional additive consists of a base component and optional components; The basic components include: 0.2-0.4 parts of citric acid or boric acid retarder, 0.4-0.6 parts of polyacrylamide or cellulose-based water loss reducing agent, and 0.1-0.5 parts of naphthalene-based or melamine-based high-temperature dispersant; The optional components are any one of the following: 0.2-0.4 parts of calcium aluminate-based low-temperature early strength agent and 0.2-0.4 parts of high-temperature stabilizer obtained by compounding zircon sand powder and silica fume in a mass ratio of 1:

1.

2. The in-situ thermally activated iron tailings-based all-solid waste oil well cement according to claim 1, characterized in that, The stabilized steel slag powder has an f-CaO content ≤ 1.5% and an f-MgO content ≤ 3%; the stabilization pretreatment method for the stabilized steel slag powder includes the following steps: P1. Coarse grinding of steel slag: Raw steel slag is ground using a ball mill to a specific surface area of ​​200-250 m². 2 / kg, to remove large pieces of metallic iron and coarse aggregate from steel slag; P2. Aging treatment: The ground steel slag is naturally aged in a closed silo at 20±5℃ for ≥12h. P3. Addition of composite stabilizer: Add 2%-5% of the composite stabilizer by mass to the aged steel slag. The composite stabilizer is a mixture of industrial grade lime and industrial gypsum in a mass ratio of 1:1-1:

2. P4. Maturation and stabilization treatment: The steel slag with added composite stabilizer is left to stand in a closed environment at 20±5℃ for 24 hours.

3. The in-situ thermally activated iron tailings-based all-solid waste oil well cement according to claim 1, characterized in that, The graded and granulated blast furnace slag powder and the graded and granulated desulfurized gypsum are respectively graded and ground until the absolute deviation of their specific surface area from that of the pretreated primary iron tailings powder is ≤20m². 2 / kg, and the batch fluctuation of their respective main chemical components of SiO2, Al2O3, and CaO is ≤1.5%.

4. The in-situ thermally activated iron tailings-based all-solid waste oil well cement according to claim 1, characterized in that, The oil well cement is classified into the following three categories according to the well temperature: Low-temperature type: suitable for well temperatures of 80-120℃, the functional admixture includes the low-temperature early strength agent; Medium-temperature type: suitable for well temperatures greater than 120℃ and not exceeding 300℃, and the functional admixture does not contain the low-temperature early-strength agent and the high-temperature stabilizer; High-temperature type: suitable for well temperatures greater than 300℃ and not exceeding 350℃, and the functional admixture includes the high-temperature stabilizer.

5. A method for preparing in-situ thermally activated iron tailings-based all-solid waste oil well cement according to any one of claims 1-4, characterized in that, Includes the following steps: Y1. Raw material pretreatment: Preparation of pretreated primary iron tailings powder; Stabilized steel slag powder was prepared and graded and milled until the absolute deviation of its specific surface area from that of the pretreated primary iron tailings powder was ≤20 μm. 2 / kg, followed by homogenization; Granulated blast furnace slag powder and desulfurized gypsum are separately graded and ground until the absolute deviation of their specific surface area from that of the pretreated primary iron tailings powder is ≤20m². 2 / kg, and then homogenized separately; The composite dispersed nanocrystalline nucleating agent, the trace non-alkali activator solid masterbatch, the functional additive, and the organic-inorganic composite corrosion inhibitor are premixed at 20±5℃ and 100-150r / min for 5-10min. Y2. Preparation of dry powder: Add the raw materials to a horizontal dry mixing equipment and stir at 150-200 r / min for 15-20 min to obtain dry powder; Y3. Packaging: The dry powder is packaged in a moisture-proof and sealed container to obtain the finished oil well cement product.

6. A method for cementing in-situ thermally activated iron tailings-based fully solidified waste oil wells using cement, as described in claim 4, characterized in that... Includes the following steps: N1. Select low-temperature, medium-temperature, or high-temperature oil well cement according to the downhole temperature of the oil well; N2. Mix the oil well cement with water at a water-to-solid ratio of 0.45 and stir for 2-5 minutes to obtain cement slurry; N3. The cement slurry is pumped into the annulus of the oil well. Relying on the high temperature environment of 80-350℃ downhole, the in-situ thermal activation and hydration reaction are completed to form cement stone.