A method for preparing an expansion agent for cementing gelling material

Abstract

The present invention discloses a method for preparing an expansion agent for cementing cementing materials, and relates to the technical field of oil and gas well cementing materials. The preparation method of the present invention uses 30-70 parts of calcium material, 10-30 parts of magnesium material, 12-35 parts of iron and aluminum materials, and 0-10 parts of other materials as expansion agent raw materials. The expansion agent raw materials are ground using different grinding particle sizes of different materials, calcined at high temperature and then ground to control the specific surface area to 240-300m 2 / kg; the mineral composition of the prepared expansive agent includes free lime, periclase, iron phase, tetracalcium aluminoferrite, and calcium sulfosilicate, wherein the free lime and periclase are encapsulated by tetracalcium aluminoferrite. The expansive agent prepared by the present invention can achieve step-by-step expansion of different expansive components in Portland cement and participate in the hydration reaction of Portland cement, achieving the purpose of synergistic expansion reaction of the expansive agent and cement hydration reaction.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas well cementing materials, and more particularly to a method for preparing an expansion agent for cementing gelling materials. Background Art

[0002] Cementing is a crucial step in oil and gas resource development. The quality of the cement sheath is crucial to ensuring the long-term safe production of oil and gas wells. The bond quality of the primary and secondary cementing surfaces of the cement sheath is a key factor influencing cementing quality. The better the bond between the cement, the formation, and the casing, the better the cementing quality. Existing cement slurry systems primarily use Portland cement as the binder. During the setting and hardening process, Portland cement undergoes "chemical shrinkage" because the specific gravity of the reactants is lower than that of the products. This degrades the cement sheath's bond quality and, in severe cases, can even cause cracking and the formation of microgaps. Studies have shown that even microgaps as small as 0.01mm at the cement sheath interface can cause gas channeling, while microgaps of 0.05-0.07mm can result in substandard cementing quality.

[0003] To mitigate the problem of deteriorating interfacial bonding quality caused by volume shrinkage in oil well cement, it is often necessary to add a certain amount of expansive agent to the cementing slurry. The goal is to improve cementing quality by allowing the volume expansion of the agent to offset the volume shrinkage during cement hydration. Currently, there are two main types of expansive agents used in oil well cement: gas-generating agents (such as hydrogen and nitrogen) and lattice-type expansive agents (such as ettringite, free lime, and periclase). Gas-generating expansive agents primarily use the gas generated by the reaction of alkali-reactive metal powders with the alkaline solution in the cement slurry as their expansion source. They are suitable for low-pressure environments and shallow wells, as their gas generation time is temperature-controlled, resulting in a narrow range of applications. Lattice-type expansive agents primarily compensate for the volume shrinkage of cement during hardening by generating ettringite, hydrogenated free lime, and hydrogenated periclase, which improve the cement paste structure to a certain extent.

[0004] CN101481605A discloses a cement expansive agent that improves the expansion properties of cement paste by adding calcium, magnesium, silicon, and aluminum raw materials, along with modifying materials. The plastic expansion rate of the cement slurry can reach 1%-3%. However, comparative tests with the comparative examples and examples found that the effect was unsatisfactory above 95°C, and it was only effective in controlling the compressive strength of the cement paste after 24 hours of curing. CN111454032A discloses a toughening expansive agent for cementing slurry and a toughened, slightly expansive cement slurry system. The addition of magnesium oxide particles, aluminum oxide particles, calcium oxide particles, and calcium carbonate whiskers improves the expansion properties and toughness of the cement paste, but does not significantly improve its compressive strength. All of these expansive agents have certain side effects, namely, they can cause the strength of the cement paste to decline.

[0005] Because cementing operations have a wide temperature range and complex environments, the expansion agent reacts too quickly when the formation temperature is high. To delay the expansion agent's action, a process currently uses organic polymer encapsulation to slow the expansion reaction. However, this method is limited by the properties of the polymer, resulting in a narrow decomposition temperature of the polymer shell and a similarly narrow temperature range. Summary of the Invention

[0006] To overcome the defects and shortcomings of the aforementioned prior art, the present invention provides a method for preparing an expansive agent for cementing materials. The present invention aims to optimize the composition and preparation process of the expansive agent, addressing the narrow temperature range of application and the mismatch between the expansion process and the cement hydration process of existing expansive agents for cementing materials. By optimizing the compatibility of the expansive agent components, controlling the particle size of each component, and further controlling the calcination temperature, the present invention allows the cement mineral material in the prepared expansive agent to encapsulate the expansive components, achieving a synergistic effect between the expansive agent expansion process and the cement hydration process, thereby enhancing the expansive agent's effectiveness and improving cementing quality.

[0007] In order to solve the above problems in the prior art, the present invention is implemented through the following technical solutions.

[0008] The present invention provides a method for preparing an expansion agent for cementing gelling material, the preparation method comprising the following steps:

[0009] S1. Prepare an expander raw material, wherein the expander raw material comprises, by weight, 30-70 parts of calcium material, 10-30 parts of magnesium material, 12-35 parts of iron and aluminum material, and 0-10 parts of other materials;

[0010] S2. Grinding of expander raw material: Grinding expander raw material with different grinding particle sizes of different materials. Specifically, the calcium material and the magnesium material are mixed and ground. After the calcium material and the magnesium material are mixed and ground, the particle distribution is V 45μm-200μm ∈[35%,60%], particles with a size greater than 200 μm <5%;

[0011] Control V in the particle distribution of mixed grinding of iron and aluminum materials 45μm-200μm ∈[25%,40%], particles with a size greater than 200 μm <2%;

[0012] S3, mixing the ground calcium material, magnesium material, iron, aluminum material and other materials to obtain an expander raw material;

[0013] S4. Pressing into cakes: Add the expander raw material obtained in step S3 to a binder and press into cakes, baking in an oven at 105°C ± 5°C, and controlling the moisture content to 2%-5%;

[0014] S5, calcination, placing the expansion agent raw material cake baked in step S4 into a high-temperature furnace, heating it from room temperature to 800-900°C, keeping it at that temperature for 20-60 minutes, and then heating it to 1100-1280°C and calcining it for 20-60 minutes;

[0015] S6, cooling and grinding, after calcination, use liquid nitrogen cooling to cool to room temperature, send it into the ball mill for grinding, and control the specific surface area to 240-300m 2 / kg;

[0016] The mineral composition of the expansion agent prepared through the above steps includes free lime, periclase, iron phase, tetracalcium aluminoferrite and calcium sulfosilicate, wherein the free lime and periclase are wrapped by tetracalcium aluminoferrite.

[0017] Further preferably, the chemical composition of the expander raw material is controlled within the range of SiO2≤3.5%, SO3>2.4%, and Al2O3:Fe2O3>0.64%.

[0018] More preferably, the applicable temperature of the prepared expansion agent is 30°C-90°C.

[0019] More preferably, when the prepared expansion agent is mixed with a cementing gel material, the amount of the expansion agent used is 5%-10% of the cementing gel material by mass.

[0020] More preferably, the calcareous material is any one or a combination of any two or more of a mixture of carbide slag and limestone, marble and white mud, wherein the CaO content is ≥52.00% and the SiO2 is ≤1.5%.

[0021] More preferably, the magnesia material is any one or more combinations of dolomite, magnesite and sepiolite, wherein the MgO content in dolomite is ≥19.00%, the MgO content in magnesite is ≥40.00%, and the MgO content in sepiolite is ≥19.0%.

[0022] Further preferably, the iron material in the iron and aluminum materials is copper slag, magnetite, sulfuric acid slag or steel slag, and the F2O3 content is ≥50.00%; the aluminum material in the iron and aluminum materials is bauxite, aluminum ash slag or high-iron bauxite, wherein the Al2O3 content in bauxite is ≥70.00%, SiO2≤2.0, the aluminum content in aluminum ash slag is ≥65.00%, SiO2≤2.0, the Al2O3 content in high-iron bauxite is ≥29.00%, and the F2O3 content is ≥15.00%.

[0023] More preferably, the other materials are fluorite and dihydrate gypsum, anhydrite, mixed gypsum, desulfurized gypsum, phosphogypsum or fluorgypsum, wherein the F ion content in fluorite is ≥25.00% and the SO3 in gypsum is ≥30.00%.

[0024] Compared with the prior art, the beneficial technical effects brought about by the present invention are as follows:

[0025] 1. The present invention differentially controls the raw material particle size through the design of the expansion agent composition and structure, adopts low-temperature calcination, uses trace elements to control the liquid phase viscosity, and uses liquid nitrogen cooling for rapid cooling after calcination to regulate the distribution state of different minerals, thereby achieving step-by-step expansion of different expansion components in silicate cement and participating in the hydration reaction of silicate cement, thereby achieving the function of compensating for shrinkage and controlling expansion, and realizing the purpose of synergistic expansion reaction of the expansion agent and cement hydration reaction.

[0026] 2. The advantage of this expansion agent over other expansion agents is that it uses calcium materials, iron materials, aluminum materials and other materials, can use waste and make rational use of resources, realize the greening and resource utilization of waste, and has certain social benefits.

[0027] 3. Control the particle size of raw materials in steps: increase the coarse particle content of the raw materials of the main expansion minerals - free calcium oxide and periclase, and increase the specific surface area of ​​free calcium oxide and periclase particles; significantly increase the iron and aluminum content, and increase the liquid phase volume; reduce the particle size of aluminum and iron materials, reduce the liquid phase viscosity, and increase the liquid phase fluidity and encapsulation; add suitable mineralizers - fluorite and gypsum to adjust the liquid phase viscosity, etc. to adjust the liquid phase to achieve the encapsulation of free calcium oxide and periclase by iron.

[0028] 4. The particle size of the expansive agent is controlled by the specific surface area method. The hydration rate of the three main mineral components in the expansive agent and the cement is adjusted by the size, thereby achieving compensation for shrinkage and synergistic reaction of micro-expansion and hydration reaction and achieving a tighter bonding performance between the cement stone and the casing.

[0029] 5. The calcination and hydration reaction mechanism of the expansion agent of the present invention is:

[0030] ——During the calcination process, by adjusting the content of alumina and iron oxide in the raw material, the solid phase reaction of active calcium oxide, active iron oxide and active alumina is promoted to form dicalcium ferrite and calcium aluminate. As the temperature rises, dicalcium ferrite continuously dissolves calcium aluminate, and the resulting liquid phase viscosity is lower. Compared with silicate cement clinker, the liquid phase volume also increases. When the remaining calcium oxide cannot react with calcium aluminate, free calcium oxide is formed; magnesium oxide is easily dissolved in the iron phase to form a eutectic, and the remaining magnesium oxide cannot be dissolved in the liquid phase, forming periclase during the cooling process. The eutectic has a lower liquid phase viscosity under high temperature conditions, which can achieve the encapsulation of free lime and active magnesium oxide. Under liquid nitrogen cooling conditions, the unreacted magnesium oxide and calcium oxide are not crystallized in time, thereby achieving the effect of most of them being encapsulated by the liquid phase.

[0031] ——The iron phase is a composition of (C2F-C6AF2-C4AF-C 62 C4AF is a key mineral component of Portland cement. It exhibits a moderate hydration rate and high early and late strength. C4AF is formed by adjusting the mineral composition of the raw materials, such as Al2O3 / Fe2O3. Its hydration rate also tends to accelerate with increasing temperature. Under high temperature conditions, retarders are often added to adjust the thickening time of cementing slurries. These retarders slow the hydration process of the cement by flocculating and encapsulating it. These retarders have a retarding effect on all mineral phases in Portland cement and also slow the dissolution rate of the iron phase. Even at different temperatures, the dissolution rate of the iron phase remains consistent with the cement hydration process. When the cement is highly hydrated and begins to set, the iron phase in the expansive agent begins to dissolve. Once the dissolution reaction is complete, the free lime and periclase begin to react with water, causing expansion.

[0032] The expansive agent contains three expansive components, each producing a continuous expansion effect at different stages. First, the iron phase begins to hydrate to form iron hydroxide and aluminum hydroxide. The aluminum hydroxide reacts with free gypsum and calcium hydroxide generated by hydration of gypsum and cement to form ettringite, which contributes to the initial expansion through its volume growth. After the iron phase reaction is complete, the free lime and periclase come into contact with the aqueous solution. After calcination at 1100-1280°C, the free lime and periclase react differently with water. The free lime reacts first to form calcium hydroxide, causing mid-stage expansion. The periclase, in its heavily burned state, has a higher activation energy for its reaction with water than the free lime and a much slower hydration rate than calcium oxide, primarily responsible for the late-stage expansion effect. The continuous expansion of the three expansive minerals at different stages effectively maintains a sustained expansion effect, effectively counteracting chemical shrinkage in the cement paste.

[0033] Calcium sulfosilicate is a low-temperature cement mineral phase with a certain degree of hydration activity. The raw material content and composition of magnesium-containing raw materials, fluorite, fluorgypsum, and gypsum are adjusted to ensure a relatively low temperature to promote the formation of a liquid phase, stabilize the calcium sulfosilicate mineral, and increase the gypsum content. Gypsum reacts with silica and calcium oxide introduced by other raw materials to form calcium sulfosilicate. Even during temperature fluctuations during the production process, calcium sulfosilicate decomposes at higher temperatures to form α'-C2S and free gypsum. These minerals remain more hydrating at temperatures between 30°C and 90°C than under ambient hydration conditions. Free gypsum is also formed during the cooling process, ensuring the formation of calcium sulfosilicate. By controlling the mass ratio of aluminum oxide to iron oxide, highly reactive anhydrous calcium sulfoaluminate is formed, effectively minimizing the impact of the addition of expansive agents on the strength of the cement paste. During hydration, gypsum reacts with free lime and aluminum hydroxide to form ettringite, which enhances the expansion of the expansive agent. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is the XRD diffraction pattern of the expanding agent of Example 1 of the present invention;

[0035] Figure 2 This is an EDS surface scan of the free lime of the expansion agent in Example 2 of the present invention.

[0036] Figure 3 This is an EDS surface scan of the expansion agent periclase in Example 2 of the present invention.

[0037] Figure 4 This is an EDS surface scan of the expanding agent ferric oxide in Example 2 of the present invention.

[0038] Figure 5 This is an EDS surface scan of aluminum oxide, the expansion agent in Example 2 of the present invention.

[0039] Figure 6 This is a petrographic picture of the expansion agent in Example 2 of the present invention. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0041] Example 1

[0042] As a preferred embodiment of the present invention, this embodiment provides a method for preparing an expansion agent for cementing gelling material, the preparation method comprising the following steps:

[0043] S1. Prepare expansion agent raw meal, which includes 68 parts of calcareous material, 10 parts of magnesia material, 14 parts of iron and aluminum materials, and 8 parts of other materials in parts by weight; wherein, the calcareous material is selected from 6 parts of limestone and 62 parts of carbide slag; the CaO content of the limestone is 54.82%, and the SiO2 content is 0.19%; the CaO content of the carbide slag is 68.21%, and the SiO2 content is 1.20%; the magnesia material is selected from 10 parts of magnesite, and the MgO content of the magnesite is 45.85%; the iron and aluminum materials are selected from 9 parts of sulfate slag and 5 parts of bauxite, the Fe2O3 content of the sulfate slag is 72.2, and the Al2O3 content of the bauxite is 71.20%; the other materials are selected from 1 part of fluorite and 7 parts of anhydrite, the F content of the fluorite is 27.21%, and the SO3 content of the anhydrite is 40.18%;

[0044] The composition of the expansion agent is controlled to be SiO2=1.73%, SO3=3.23%, Al2O3:Fe2O3=0.74;

[0045] S2. Grinding of expander raw material: Grinding expander raw material with different grinding particle sizes of different materials. Specifically, the calcium material and the magnesium material are mixed and ground. The particle distribution of calcium and magnesium materials is V 45μm-200μm =56.0%, particle size greater than 200μm = 3.5%; iron and aluminum materials are mixed and ground, and the particle distribution is controlled by V 45μm-200μm =36.0%, particles larger than 200 μm = 0.12%;

[0046] S3. Evenly mix the ground calcium material, magnesium material, iron, aluminum material and other materials (mix in a test mill for 10 minutes) to obtain an expander raw meal;

[0047] S4, pressing into cakes, adding a binder to the expander raw material obtained in step S3 and pressing into cakes, baking in an oven at 105°C, and controlling the moisture content to 2%;

[0048] S5, calcination, placing the expansion agent raw material cake baked in step S4 into a high-temperature furnace, heating it from room temperature to 850°C, keeping it at that temperature for 30 minutes, and then heating it to 1200°C and calcining it for 30 minutes;

[0049] S6, cooling and grinding, after calcination, use liquid nitrogen cooling to cool to room temperature, send it into the ball mill for grinding, and control the specific surface area at 240m 2 / kg;

[0050] The applicable temperature of the expansion agent is 30-90°C, and the amount used is 5.0% of the mass fraction of the cementing gel material.

[0051] As an example of this embodiment, the limestone and carbide slag selected as the above-mentioned calcium materials can also be replaced in combination with marble or white mud; the dolomite selected as the above-mentioned magnesium material can also be replaced with dolomite or sepiolite; the fluorite and anhydrite selected as the above-mentioned other materials can also be replaced in combination with dihydrate gypsum, mixed gypsum, desulfurized gypsum, phosphogypsum or fluorgypsum.

[0052] Example 2

[0053] As another preferred embodiment of the present invention, this embodiment provides a method for preparing an expansion agent for cementing gelling material, the preparation method comprising the following steps:

[0054] S1. Prepare expander raw material, which includes 50 parts of calcium material, 18 parts of magnesia material, 24 parts of iron and aluminum materials, and 8 parts of other materials in parts by weight; wherein the calcium material is 10 parts of white mud and 40 parts of carbide slag; the CaO content in the white mud is 52.02%, and the SiO2 content is 1.10%, the CaO content in the carbide slag is 69.1%, and the SiO2 content is 1.15%; the magnesia material is 8 parts of magnesite and 10 parts of sepiolite, the MgO content in magnesite is 45.85%; the MgO content in sepiolite is 21.42%; the iron and aluminum materials are 13 parts of magnetite and 11 parts of aluminum ash, the Fe2O3 content in magnetite is 69.45%, and the Al2O3 content in aluminum ash is 69.23%; the other materials are 0.8 parts of fluorite and 7.2 parts of dihydrate gypsum, the F content in fluorite is 28.46%, and the SO3 content in dihydrate gypsum is 33.45%;

[0055] The composition of the expansion agent is controlled to be SiO2=3.53%, SO3=3.56%, Al2O3:Fe2O3=0.70%;

[0056] S2. Grinding of expander raw material: Grinding expander raw material with different grinding particle sizes of different materials. Specifically, the calcium material and the magnesium material are mixed and ground. The particle distribution of calcium and magnesium materials is V 45μm-200μm =35.0%, particle size greater than 200μm = 2.1%; iron and aluminum materials are mixed and ground, and the particle distribution is controlled by V 45μm-200μm =40.0%, particles with a diameter greater than 200 μm = 1.0%;

[0057] S3. Evenly mix the ground calcium material, magnesium material, iron, aluminum material and other materials (mix in a test mill for 8 minutes) to obtain an expander raw meal;

[0058] S4, pressing into cakes: adding the expander raw material obtained in step S3 to a binder and pressing into cakes, baking in an oven at 105°C, and controlling the moisture content to 2.6%;

[0059] S5, calcination, placing the expansion agent raw material cake baked in step S4 into a high-temperature furnace, heating it from room temperature to 900°C, keeping it at that temperature for 40 minutes, and then heating it to 1280°C and calcining it for 48 minutes;

[0060] S6, cooling and grinding, after calcination, use liquid nitrogen cooling to cool to room temperature, send it into the ball mill for grinding, and control the specific surface area at 298m 2 / kg;

[0061] The applicable temperature of the expansion agent is 30-90°C, and the amount used is 9.0% of the mass fraction of the cementing gel material.

[0062] Example 3

[0063] As another preferred embodiment of the present invention, this embodiment provides a method for preparing an expansion agent for cementing gelling material, the preparation method comprising the following steps:

[0064] S1. Prepare expander raw material, which includes 53 parts of calcium material, 14 parts of magnesia material, 34 parts of iron and aluminum materials, and 9 parts of other materials in parts by weight; wherein, the calcium material is 53 parts of carbide slag; the CaO content of the carbide slag is 69.51%, and the SiO2 content is 1.05%; the magnesia material is 6 parts of magnesite and 8 parts of dolomite, the MgO content of the magnesite is 42.63%; the MgO content of the dolomite is 20.45%; the iron and aluminum materials are 10 parts of magnesia, 10 parts of magnesia and 10 parts of dolomite. The raw materials are 10 parts copper slag, 3 parts steel slag, 17 parts bauxite and 4 parts high-alumina bauxite. The Fe2O3 content in the copper slag is 69.45%, and the Fe2O3 content in the steel slag is 50.00%. The Al2O3 content of bauxite and high-alumina bauxite is 69.23%, and the Al2O3 content of high-iron bauxite is 29.00%. The other materials are 0.5 parts fluorite and 8.5 parts phosphogypsum. The F content in fluorite is 28.46%, and the SO3 content in phosphogypsum is 33.45%.

[0065] The composition of the expansion agent is controlled to be SiO2=3.53%, SO3=1.46%, Al2O3:Fe2O3=0.70%;

[0066] S2. Grinding of expander raw material: Grinding expander raw material with different grinding particle sizes of different materials. Specifically, the calcium material and the magnesium material are mixed and ground. The particle distribution of calcium and magnesium materials is V 45μm-200μm =50.0%, particle size greater than 200μm = 1.2%; iron and aluminum materials are mixed and ground, and V is controlled in the particle distribution 45μm-200μm = 25.0%, particles larger than 200 μm = 0.9%;

[0067] S3. Evenly mix the ground calcium material, magnesium material, iron, aluminum material and other materials (mix in a test mill for 5 minutes) to obtain an expander raw meal;

[0068] S4, pressing into cakes, adding a binder to the expander raw material obtained in step S3 and pressing into cakes, baking in an oven at 105°C, and controlling the moisture content to 2.1%;

[0069] S5, calcination, placing the expansion agent raw material cake baked in step S4 into a high-temperature furnace, heating it from room temperature to 850°C, keeping it at that temperature for 20 minutes, and then heating it to 1260°C and calcining it for 35 minutes;

[0070] S6, cooling and grinding, after calcination, use liquid nitrogen cooling to cool to room temperature, send it into the ball mill for grinding, and control the specific surface area at 260m 2 / kg;

[0071] The applicable temperature of the expansion agent is 30-90°C, and the amount used is 7.0% of the mass fraction of the cementing gel material.

[0072] Example 4

[0073] As another preferred embodiment of the present invention, this embodiment provides a method for preparing an expansion agent for cementing gelling material, the preparation method comprising the following steps:

[0074] S1. Prepare an expansion agent raw meal, which comprises, by weight, 70 parts of a calcareous material, 11 parts of a magnesia material, 12 parts of an iron and aluminum material, and 7 parts of other materials; wherein the calcareous material is 40 parts of marble and 30 parts of carbide slag; the marble has a CaO content of 51.21% and a SiO2 content of 1.3%; the carbide slag has a CaO content of 65.23% and a SiO2 content of 1.5%; the magnesia material is 11 parts of magnesite, and the magnesite has a MgO content of 39.21%; the iron and aluminum materials are 5 parts of bauxite and 7 parts of magnetite, the magnetite has a Fe2O3 content of 65.12%, and the bauxite has an Al2O3 content of 52.13%; the other materials are 0.6 parts of fluorite and 6.4 parts of dihydrate gypsum, the fluorite has a F content of 19.21%, and the dihydrate gypsum has a SO3 content of 28.56%;

[0075] The composition of the expansion agent is controlled to be SiO2=1.56%, SO3=2.10%, Al2O3:Fe2O3=0.66;

[0076] S2. Grinding of expander raw material: Grinding expander raw material with different grinding particle sizes of different materials. Specifically, the calcium material and the magnesium material are mixed and ground. The particle distribution of calcium and magnesium materials is V 45μm-200μm=45.2%, particle size greater than 200μm = 2.1%; iron and aluminum materials are mixed and ground, and V is controlled in the particle distribution 45μm-200μm =33.2%, particles larger than 200 μm = 1.2%;

[0077] S3. Evenly mix the ground calcium material, magnesium material, iron, aluminum material and other materials (mix in a test mill for 10 minutes) to obtain an expander raw meal;

[0078] S4, pressing into cakes: adding the expander raw material obtained in step S3 to a binder and pressing into cakes, baking in an oven at 105°C, and controlling the moisture content to 3.2%;

[0079] S5, calcination, placing the expansion agent raw material cake baked in step S4 into a high-temperature furnace, heating it from room temperature to 900°C, keeping it at that temperature for 40 minutes, and then heating it to 1180°C and calcining it for 25 minutes;

[0080] S6, cooling and grinding, after calcination, use liquid nitrogen cooling to cool to room temperature, send it into the ball mill for grinding, and control the specific surface area at 280m 2 / kg;

[0081] The applicable temperature of the expansion agent is 30-90°C, and the amount used is 10% of the mass fraction of the cementing gel material.

[0082] Example 5

[0083] As another preferred embodiment of the present invention, this embodiment provides a method for preparing an expansion agent for cementing gelling material, the preparation method comprising the following steps:

[0084] S1. Prepare an expansion agent raw material, which includes, by weight, 30 parts of a calcium material, 30 parts of a magnesium material, 20 parts of an iron and aluminum material, and 10 parts of other materials; wherein the calcium material is 30 parts of limestone, wherein the CaO content is 54.23%, and the SiO2 content is 0.12%; the magnesium material is 30 parts of dolomite, and the MgO content in the dolomite is 21.53%; the iron and aluminum materials are 12 parts of bauxite and 8 parts of sulfate slag, wherein the Fe2O3 content is 71.02%, and the Al2O3 content in the bauxite is 66.89%; the other materials are 1 part of fluorite and 9 parts of dihydrate gypsum, wherein the F content in the fluorite is 19.21%, and the SO3 content in the dihydrate gypsum is 33.12%;

[0085] The composition of the expansion agent is controlled to be SiO2=2.30%, SO3=2.20%, Al2O3:Fe2O3=0.71;

[0086] S2. Grinding of expander raw material: Grinding expander raw material with different grinding particle sizes of different materials. Specifically, the calcium material and the magnesium material are mixed and ground. The particle distribution of calcium and magnesium materials is V 45μm-200μm =36.9%, particle size greater than 200μm = 0.5%; iron and aluminum materials are mixed and ground, and V is controlled in the particle distribution 45μm-200μm =30.0%, particles larger than 200 μm = 1.2%;

[0087] S3. Evenly mix the ground calcium material, magnesium material, iron, aluminum material and other materials (mix in a test mill for 10 minutes) to obtain an expander raw meal;

[0088] S4, pressing into cakes, adding the expander raw material obtained in step S3 to a binder and pressing into cakes, baking in an oven at 105°C, with the temperature fluctuating within 5°C, and controlling the moisture content to 5%;

[0089] S5, calcination, placing the expansion agent raw material cake baked in step S4 into a high-temperature furnace, heating it from room temperature to 800°C, keeping it at that temperature for 60 minutes, and then heating it to 1100°C and calcining it for 60 minutes;

[0090] S6, cooling and grinding, after calcination, use liquid nitrogen cooling to cool to room temperature, send it into the ball mill for grinding, and control the specific surface area to 300m 2 / kg;

[0091] The applicable temperature of the expansion agent is 30-90°C, and the usage amount is 5.6% of the mass fraction of the cementing gel material.

[0092] Example 6

[0093] As another preferred embodiment of the present invention, this embodiment provides a method for preparing an expansion agent for cementing gelling material, the preparation method comprising the following steps:

[0094] S1. Prepare an expander raw material, which comprises, by weight, 45 parts of a calcium material, 20 parts of a magnesia material, and 35 parts of an iron and aluminum material; wherein the calcium material is 45 parts of white mud; the CaO content of the white mud is 49.23%, and the SiO2 content is 2.0%; the magnesia material is 20 parts of magnesite, and the MgO content of the magnesite is 37.25%; the iron and aluminum materials are 12 parts of bauxite and 23 parts of pyrite, and the Fe2O3 content of the pyrite is 50.19%, and the Al2O3 content of the bauxite is 59.14%;

[0095] The composition of the expansion agent is controlled to be SiO2=1.56%, SO3=2.10%, Al2O3:Fe2O3=0.66;

[0096] S2. Grinding of expander raw material: Grinding expander raw material with different grinding particle sizes of different materials. Specifically, the calcium material and the magnesium material are mixed and ground. The particle distribution of calcium and magnesium materials is V 45μm-200μm =56.0%, particle size greater than 200μm = 4.9%; iron and aluminum materials are mixed and ground, and the particle distribution is controlled by V 45μm-200μm =35.0%, particles larger than 200 μm = 1.2%;

[0097] S3. Evenly mix the ground calcium material, magnesium material, iron material, and aluminum material (mix in a test mill for 10 minutes) to obtain an expander raw meal;

[0098] S4, pressing into cakes, adding the expander raw material obtained in step S3 to a binder and pressing into cakes, baking in an oven at 105°C with the temperature fluctuating within 5°C and the moisture content at 4%;

[0099] S5, calcination, placing the expansion agent raw material cake baked in step S4 into a high-temperature furnace, heating it from room temperature to 830°C, keeping it at that temperature for 25 minutes, and then heating it to 1100°C and calcining it for 20 minutes;

[0100] S6, cooling and grinding, after calcination, use liquid nitrogen cooling to cool to room temperature, send it into the ball mill for grinding, and control the specific surface area at 260m 2 / kg;

[0101] The applicable temperature of the expansion agent is 30-90°C, and the usage amount is 6.5% of the mass fraction of the cementing gel material.

[0102] Comparative Example 1

[0103] In order to highlight the performance of the expansion agent for cementing cementing material proposed in the present invention, a comparative example is specially prepared. In this comparative example, limestone is used as raw material, crushed and sent into a high-temperature furnace, calcined at 1200℃ for 30 minutes to obtain calcium oxide expansion agent, and then ball-milled into powder. The specific surface area is controlled to be 285m 2 / kg.

[0104] Comparative Example 2

[0105] In order to highlight the performance of the expansion agent for cementing cementing material proposed in the present invention, a comparative example is specially prepared. In this comparative example, magnesite is used as raw material, crushed and sent into a high-temperature furnace, calcined at 1200℃ for 30 minutes to obtain magnesium oxide expansion agent, and then ball-milled into powder. The specific surface area is controlled to be 276m 2 / kg.

[0106] Test Example 1

[0107] According to Examples 1-4 and Comparative Examples 1-2, a 3% addition amount was added to Grade G oil well cement. Cement slurries were prepared in accordance with the relevant provisions of GB / T19139, wherein the mixing water accounted for 44% of the mass of the cement. The prepared cement slurries were poured into expansion rings and strength molds, respectively, and cured in water baths at 30°C, 60°C, and 90°C, respectively. The expansion values ​​of the cement were tested at 1 day, 3 days, and 7 days in accordance with the relevant requirements of GB / T33293-2016. The specific test results are shown in Tables 1, 2, and 3.

[0108] Table 1 shows the expansion rate and compressive strength of the expansion agent at 30°C

[0109]

[0110] Table 2 shows the expansion value of the expansion agent at 60°C

[0111]

[0112] Table 3 shows the expansion value of the expansion agent at 90°C

[0113]

[0114] According to the data in the table above, under the same water-cement ratio, the expansion values ​​of Schemes 1-4 at different curing temperatures and ages are significantly better than those of the control sample. This indicates that during the hydration process, due to the different expansion sources of the expansive agent, during the hydration process of G-grade oil well cement, a small amount of free gypsum and gypsum react with tricalcium aluminate and iron phase water to form ettringite, which provides an early hydration mineral skeleton, an early expansion source, and early strength support. The iron phase and glass phase that encapsulate the free calcium oxide and periclase are also consumed at the same time, forming ettringite to increase the density of the silicate hydration product. Immediately after the encapsulated iron phase is consumed, the free calcium oxide particles encapsulated within react moderately to form calcium hydroxide, which expands in volume and fills the space occupied by the water after the reaction of silicate minerals. The water hydrates the calcium silicate gel, and the ettringite and the expansive agent produce alternating hydration products. After the external encapsulation is completely hydrated, the periclase continues to hydrate to form magnesium hydroxide, which continues to fill part of the space between the water and the gelling product, further improving the density of the cement paste and the cement strength.

[0115] The expansive agent compensates for shrinkage and continues to expand during hydration, resulting in excellent bonding between the casing and the cement paste. Data from Schemes 1-4 and the comparative sample show that as curing temperature increases, the gypsum in the base material (Grade G oil well cement) hydrates with the tricalcium aluminate and iron phase in the cement to form ettringite. Etringite does not decompose at low temperatures (30-60°C), resulting in high stability and superior expansion performance compared to Comparative Samples 1-2. Under high-temperature curing conditions (90°C), ettringite becomes unstable and prone to decomposition. This is why Schemes 3-4, with their lower sulfur trioxide content and controlled free gypsum and calcium sulfosilicate content, inhibit the early formation of ettringite at high temperatures. The hydration of the encapsulated free calcium oxide and periclase assists expansion, effectively controlling shrinkage throughout the entire process and achieving minimal expansion of the cement paste, reducing shrinkage at high temperatures. Expansion performance is positively correlated with cement paste strength.

[0116] The expansion agent in Example 1 was subjected to phase analysis, and the Figure 1 As shown, it is confirmed that there are free calcium oxide and periclase in the expansion agent, as well as a large amount of iron phase, among which the content of tetracalcium aluminoferrite is relatively high, a small amount of low-temperature mineral calcium sulfosilicate, and a certain amount of free gypsum. This is consistent with the mineral design of the present invention. Figure 2 , Attachment Figure 3 , Attachment Figure 4 and attached Figure 5 The electron microscope analysis of each mineral of the expansion agent of Example 2 is shown in Figure 2. Through EDX analysis, it can be seen that the distribution of periclase and free calcium oxide is uniform, and there is less formation of large-particle ore nests. Instead, they are uniformly wrapped by the iron phase and the glass phase, which can effectively regulate the hydration reaction of free calcium oxide and periclase. Figure 6 It can also be concluded from the petrographic analysis diagram that the free calcium oxide with colorful pockmarked morphology and the periclase minerals with straight edges and raised black edges are evenly wrapped by the iron phase and glass phase, which more intuitively reflects the sintering process of the expansion agent.

[0117] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention and are intended to illustrate the technical solutions of the present invention, rather than limiting them, and certainly not limiting the patent scope of the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features therein may be replaced by equivalents. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention. In other words, any changes or refinements made to the main design concept and spirit of the present invention that have no substantive significance, provided that the technical problems they solve are still consistent with those of the present invention, should be included in the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention to other related technical fields should also be included in the patent protection scope of the present invention.

Claims

1. A method for preparing an expansion agent for cementing gelling material, characterized in that: The preparation method comprises the following steps: S1. Prepare an expander raw material, wherein the expander raw material comprises, by weight, 30-70 parts of calcium material, 10-30 parts of magnesium material, 12-35 parts of iron and aluminum material, and 0-10 parts of other materials; S2. Grinding of expander raw material: Grinding expander raw material with different grinding particle sizes of different materials. Specifically, the calcium material and the magnesium material are mixed and ground. After the calcium material and the magnesium material are mixed and ground, the particle distribution is V 45μm-200μm ∈[35%,60%], particles with a size greater than 200 μm <5%; Mix and grind the iron and aluminum materials, and control the V 45μm-200μm ∈[25%,40%], particles with a size greater than 200 μm <2%; S3, mixing the ground calcium material, magnesium material, iron, aluminum material and other materials to obtain an expander raw material; S4. Pressing into cakes: The expander raw material obtained in step S3 is mixed with a binder and pressed into cakes, which are then baked in an oven at 105°C ± 5°C to control the moisture content to 2%-5%. S5, calcination, placing the expansion agent raw material cake baked in step S4 into a high-temperature furnace, heating it from room temperature to 800-900°C, keeping it at that temperature for 20-60 minutes, and then heating it to 1100-1280°C and calcining it for 20-60 minutes; S6, cooling and grinding, after calcination, use liquid nitrogen cooling to cool to room temperature, send it into the ball mill for grinding, and control the specific surface area to 240-300m 2 / kg; The mineral composition of the expansion agent prepared through the above steps includes free lime, periclase, iron phase, tetracalcium aluminoferrite and calcium sulfosilicate, wherein the free lime and periclase are wrapped by tetracalcium aluminoferrite.

2. The method for preparing an expansion agent for cementing gelling material according to claim 1, wherein: The chemical composition of the expander raw material is controlled within the range of SiO2≤3.5%, SO3>2.4%, and Al2O3:Fe2O3>0.64%.

3. The method for preparing an expansion agent for cementing gelling material according to claim 1, wherein: The applicable temperature of the prepared expansion agent is 30°C-90°C.

4. The method for preparing an expansion agent for cementing gelling material according to any one of claims 1 to 3, characterized in that: The calcareous material is any one or a combination of any two or more of a mixture of carbide slag and limestone, marble and white mud, wherein the CaO content is ≥52.00% and the SiO2 is ≤1.5%.

5. The method for preparing an expansion agent for cementing gelling material according to any one of claims 1 to 3, characterized in that: The magnesia material is any one or more combinations of dolomite, magnesite and sepiolite, wherein the MgO content in dolomite is ≥19.00%, the MgO content in magnesite is ≥40.00%, and the MgO content in sepiolite is ≥19.0%.

6. The method for preparing an expansion agent for cementing gelling material according to any one of claims 1 to 3, characterized in that: The iron material in the iron and aluminum materials is copper slag, magnetite, sulfuric acid slag or steel slag, and the Fe2O3 content is ≥50.00%; the aluminum material in the iron and aluminum materials is bauxite, aluminum ash slag or high-iron bauxite, wherein the Al2O3 content in bauxite is ≥70.00%, SiO2≤2.0%, the Al2O3 content in aluminum ash slag is ≥65.00%, SiO2≤2.0%, the Al2O3 content in high-iron bauxite is ≥29.00%, and the Fe2O3 content is ≥15.00%.

7. The method for preparing an expansion agent for cementing gelling material according to any one of claims 1 to 3, characterized in that: The other materials are fluorite and dihydrate gypsum, anhydrite, mixed gypsum, desulfurized gypsum, phosphogypsum or fluorgypsum, wherein the F ion content in the fluorite is ≥25.00% and the SO3 in the gypsum is ≥30.00%.

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