Method for inducing calcium carbonate precipitation to bond loose sand grains through double polymers

Abstract

The invention relates to the technical field of geotechnical engineering, and discloses a method for inducing calcium carbonate to precipitate and bond loose sand grains through double polymers. Comprising the following steps: preparing a CaCl2-HPMA mixed solution from hydrolytic polymaleic anhydride and calcium chloride; the preparation method comprises the following steps: preparing a Na2CO3-APAM mixed solution from anionic polyacrylamide and sodium carbonate; after the CaCl2-HPMA mixed solution is injected into the loose sand body, the Na2CO3-APAM mixed solution with the same volume as the CaCl2-HPMA mixed solution is injected into the loose sand body; and the designed cementing liquid injection amount is completed for the loose sand body, and cementing is completed after calcium carbonate is completely reacted. The method is convenient to construct and use and low in time and material cost; the cemented sand body does not need to be dried and has higher unconfined compressive strength in a humid environment; the used cementing substance has good water solubility, the cementing liquid has good fluidity among sand grain pores, and the effective cementing range is large.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering technology, specifically to a method for inducing calcium carbonate precipitation and cementing loose sand particles using hydrolyzed polymaleic anhydride and anionic polyacrylamide. Background Technology

[0002] The cementation of loose sand particles plays a crucial role in engineering geology, oil and gas extraction, civil engineering, and environmental remediation. For example, it reduces the risk of sand layer liquefaction, improves the stability of sandy slopes, prevents sand layer seepage damage, controls sand production in oil and gas reservoirs, and reduces the spread of groundwater pollution. Induced calcium carbonate precipitation, a high-performance, environmentally friendly, and controllable modern technology, fills the pores between loose sand particles and bonds adjacent sand particles, significantly increasing the strength and stiffness of the sand body, reducing the possibility of deformation and liquefaction, decreasing overall permeability, and improving internal erosion resistance. It also alleviates geotechnical engineering problems in a non-destructive manner, can be applied over large areas at room temperature, and the cementation process has minimal impact on the soil itself and the surrounding environment.

[0003] Microbial-induced carbonate precipitation (MICP), a biomineralization-based induced carbonate precipitation technology, has been widely studied for its high-efficiency cementing and reinforcement performance. However, in practical applications of MIP, microbial activity is easily affected by adverse environmental factors, and the decomposition of urea produces harmful byproducts such as ammonium and nitrates. To overcome the limitations of using microorganisms, biomimetic calcium carbonate induced precipitation (BCICP) has been proposed. This technology uses calcium carbonate mineralization additives to control the crystallization system, regulating the deposition process of calcium carbonate crystals on the surface of soil particles through mineralization regulators, thereby cementing loose sand particles and improving the engineering mechanical properties of sandy soils. Previous studies on BCICP have required drying the cemented sand after the cementing solution is injected. However, in most geotechnical engineering environments, sand bodies are constantly in a moist, unsaturated state, making effective drying difficult. Therefore, it is still necessary to further study the mechanism of calcium carbonate induced precipitation cementing loose sand particles, and to propose improved schemes based on inheriting the superior cementing properties of calcium carbonate, avoiding the limitations of using microorganisms or requiring drying treatment.

[0004] It should be noted that the above statements are only used to provide background information related to this application and do not necessarily constitute prior art. Summary of the Invention

[0005] To address the shortcomings of existing calcium carbonate precipitation techniques, this invention provides a method for inducing calcium carbonate precipitation and cementing loose sand particles using two polymers: hydrolyzed polymaleic anhydride and anionic polyacrylamide. This method utilizes two polymers, hydrolyzed polymaleic anhydride and anionic polyacrylamide, to jointly regulate the deposition process of calcium carbonate between loose sand particles. This results in the generated calcium carbonate having highly efficient cementing properties for the sand particles. This method is convenient to implement, provides rapid cementation, and generates no harmful byproducts. The cemented sand body does not require drying treatment and exhibits high unconfined compressive strength in a humid, unsaturated environment.

[0006] A method for inducing calcium carbonate precipitation and cementing loose sand particles using a dual polymer comprises the following steps:

[0007] (1) Preparation of cementing solution A: First, dissolve hydrolyzed polymaleic anhydride (HPMA) in water and stir until homogeneous. Then, add calcium chloride (CaCl2) to the solution and stir until homogeneous to prepare a CaCl2-HPMA mixed solution. The concentration of hydrolyzed polymaleic anhydride is 2 g / L-3 g / L, the molecular weight of hydrolyzed polymaleic anhydride is 400 g / mol-800 g / mol, and the concentration of calcium chloride is 0.5 mol / L-1 mol / L.

[0008] (2) Preparation of cementing solution B: First, dissolve anionic polyacrylamide (APAM) in water and stir until homogeneous. Then, add sodium carbonate (Na2CO3) to the solution and stir until homogeneous to prepare a Na2CO3-APAM mixed solution. The concentration of polyacrylamide is 1 g / L-2 g / L, the molecular weight of polyacrylamide is 6,000,000 g / mol-15,000,000 g / mol, and the concentration of sodium carbonate is 0.5 mol / L-1 mol / L.

[0009] (3) After injecting the CaCl2-HPMA mixed solution into the loose sand body, inject an equal volume of Na2CO3-APAM mixed solution into the loose sand body; one injection of cementing solution A and one injection of cementing solution B constitute one injection cycle;

[0010] (4) After the sand body has completed multiple injection cycles to achieve the total injection volume designed, the sand body is left to stand for a preset curing time to complete the bonding.

[0011] Furthermore, in step (3), the injection volume of cementing liquid A or cementing liquid B in a single injection cycle is 25%-50% of the total pore volume of the sand body, and the number of injection cycles is greater than or equal to 8.

[0012] In some embodiments, the method of injecting cementing liquid A or cementing liquid B into the sand body in step (3) is surface spraying or pumping injection.

[0013] In some embodiments, if the surface spraying method is used in step (3), a single injection cycle consists of spraying cementitious liquid A onto the surface of the loose sand body, allowing it to stand for a period of time greater than or equal to a preset interval after cementitious liquid A has completely penetrated the sand body, and then spraying cementitious liquid B onto the surface of the sand body, and allowing it to stand for a period of time greater than or equal to a preset interval after cementitious liquid B has completely penetrated the sand body, and then allowing it to stand for a period of time greater than or equal to a preset interval. The preset interval is greater than or equal to 0.5h.

[0014] In some embodiments, if the pumping injection method is used in step (3), a single injection cycle consists of pumping cementing liquid A into the sand body, allowing it to stand for a preset interval, then pumping cementing liquid B into the sand body and allowing it to stand for a preset interval. The preset interval is greater than or equal to 0.5h.

[0015] In some embodiments, the preset maintenance time in step (4) is greater than or equal to 12 hours.

[0016] The beneficial effects of the present invention include at least the following:

[0017] (i) Compared with the microbial-induced carbonate precipitation technology for cementing sand particles, the present invention does not require the use of microorganisms, does not have strict requirements for the cementing environment, and produces no harmful byproducts during the cementing process.

[0018] (II) Compared with the previous additive-based induced calcium carbonate precipitation technology for cementing sand particles, the present invention does not require drying of the cemented sand sample after the cementing liquid is injected. The cemented sand sample formed in a humid unsaturated environment has high unconfined compressive strength.

[0019] (III) The combined induction of HPMA and APAM in this invention can increase the cementing ability of calcium carbonate generated by the metathesis reaction of calcium chloride and sodium carbonate by more than 15 times in a humid environment. The unconfined compressive strength of the cemented sand body with added polymer in a humid environment can reach 1.32 MPa.

[0020] (iv) The present invention is easy to construct and quick to bond. The cementing material used has good water solubility, and the cementing liquid formed has good fluidity in the pores of sand and soil, with a large effective bonding range. Attached Figure Description

[0021] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0022] Figure 1 This is a schematic diagram of the cylindrical sand body bonding device in Embodiments 1 and 2 of this application;

[0023] Figure 2 This is a schematic diagram of the cylindrical sand body bonding device in Embodiment 3 of this application;

[0024] Figure 3 The unconfined compressive strength values ​​and calcium carbonate content of the cemented sand bodies in working conditions A1-A4 of Example 1 of this application;

[0025] Figure 4 The unconfined compressive strength values ​​of the cemented sand body in working conditions B1-B3 of Example 2 of this application;

[0026] Figure 5 The unconfined compressive strength and calcium carbonate content of sand samples at different heights of the cemented sand body in Example 3 of this application;

[0027] Figure 6 SEM images of cemented sand obtained under working conditions A1 and A4 in Example 1 of this application: Figure 6 (a) is a SEM image of the cemented sand body under working condition A1 at a magnification of 500. Figure 6 (b) is a SEM image of the cemented sand body under condition A1 with a magnification of 5000. Figure 6 (c) is a SEM image of the cemented sand body under working condition A4, magnified 500 times. Figure 6 (d) is a SEM image of the cemented sand body under working condition A4 with a magnification of 5000.

[0028] Explanation of reference numerals in the attached figures:

[0029] 1. Plastic film; 2. Filter paper; 3. Acrylic tube mold; 4. Cylindrical sand body; 5. Plastic bowl; 6. Metal perforated plate with 1mm pore diameter; 7. Plastic cup; 8. Iron stand; 9. Fixture. Detailed Implementation

[0030] The embodiments of this application are described in detail below, with examples of these embodiments shown in the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0031] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit this application; unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).

[0032] The terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are open-ended expressions, meaning they include what is specified in this application but do not exclude other aspects.

[0033] In the description of this application, all figures disclosed herein, whether or not the words "approximately" or "about" are used, are approximate values. Each figure may vary by less than 10% or by a difference that is considered reasonable by one of the art, such as 1%, 2%, 3%, 4%, or 5%.

[0034] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0035] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0036] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0037] This invention employs a dual-polymer co-induced calcium carbonate precipitation method. The metathesis reaction between calcium chloride and sodium carbonate between loose sand particles is regulated by hydrolyzing polymaleic anhydride (HPMA) and anionic polyacrylamide (APAM). This allows the generated calcium carbonate to fully fill the pores between sand particles and deposit at the contact points, bonding adjacent sand particles and thus cementing and reinforcing the sand body. The chemical composition of quartz sand particles is mainly silicon dioxide (SiO2). When liquid water is present in the pores between particles, silanol groups capable of forming hydrogen bonds will exist on the particle surface, and the surface is usually negatively charged. After the CaCl2-HPMA mixed solution is injected into the sand body, Ca... 2+ Combined with the carboxyl group in the HPMA molecule, Ca 2+ A cation bridge is formed between HPMA molecules and the negatively charged SiO2 surface, allowing HPMA molecules to be effectively adsorbed onto the surface of sand particles and bind with Ca. 2+ HPMA molecules adsorbed on the surface of sand particles will serve as nucleation sites for CaCO3 crystals. Subsequently, a Na2CO3-APAM mixed solution is injected, and the Ca molecules at the nucleation sites on the sand particle surface... 2+ Combined with CO3 2- CaCO3 precipitate forms due to the adsorption of HPMA molecules, which effectively adsorb onto the surface of sand particles, thus binding them. APAM molecules can adsorb onto the surface of sand particles via cation bridges and hydrogen bonds, accelerating the flocculation of the CaCO3 suspension in the pores of the sand particles, allowing different CaCO3 particles to effectively combine and form larger CaCO3 aggregates. HPMA enhances the bonding between CaCO3 particles and sand particles, while APAM enhances the bonding between different CaCO3 particles.

[0038] In some embodiments, in the CaCl2-HPMA mixed solution, the concentration of the hydrolyzed polymaleic anhydride is 2 g / L-3 g / L, and the molecular weight of the hydrolyzed polymaleic anhydride is 400 g / mol-800 g / mol; and / or, the concentration of the calcium chloride is 0.5 mol / L-1 mol / L. In the Na2CO3-APAM mixed solution, the concentration of the anionic polyacrylamide is 1 g / L-2 g / L, and the molecular weight of the anionic polyacrylamide is 6,000,000 g / mol-15,000,000 g / mol; and / or, the concentration of the sodium carbonate is 0.5 mol / L-1 mol / L. Thus, the resulting CaCl2-HPMA mixed solution and Na2CO3-APAM mixed solution exhibit high fluidity, HPMA and APAM efficiently regulate the metathesis reaction of CaCl2 and Na2CO3, and the generated calcium carbonate precipitate is highly effective in cementing loose sand particles.

[0039] In some embodiments, during the cementing treatment, the volume of cementing solution A or cementing solution B injected in a single cycle is 25%-50% of the total pore volume of the sand body. This allows for sufficient contact and reaction between CaCl2 in cementing solution A and Na2CO3 in cementing solution B as they flow between the pores of the sand particles.

[0040] In some embodiments, the number of injection cycles in the cementing treatment is greater than or equal to 8. This allows sufficient calcium carbonate to form between sand particles, establishing effective cementation between adjacent sand particles, and significantly improving the unconfined compressive strength of the sand body. Furthermore, the greater the number of cycles, the greater the increase in sand body strength.

[0041] In some embodiments, during the cementing treatment, the preset interval between the injection of cementing solution A or cementing solution B into the circulation is greater than or equal to 0.5 hours. This allows HPMA in cementing solution A and APAM in cementing solution B sufficient time to remain and adhere to the sand grain surface, which is beneficial for subsequent control of the calcium carbonate reaction.

[0042] In some embodiments, the curing time in the cementation treatment is preset to be greater than or equal to 12 hours. This facilitates the transformation of calcium carbonate crystals into a more stable state and enhances the cementing effect of calcium carbonate.

[0043] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art. It should be noted that the description of these embodiments is for the purpose of aiding understanding of the present invention, but does not constitute a limitation thereof. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially. The embodiments of the present invention provide a method for inducing calcium carbonate precipitation and cementation of loose sand particles by hydrolysis of polymaleic anhydride and anionic polyacrylamide. The basic operating steps in Examples 1-3 below all conform to the following operating flow:

[0044] (1) Preparation of cementing solution: Dissolve hydrolyzed polymaleic anhydride in water and stir evenly, then add calcium chloride to the solution and stir evenly to prepare a CaCl2-HPMA mixed solution, so that the HPMA concentration is the designed concentration and the CaCl2 concentration is 1 mol / L; dissolve anionic polyacrylamide in water and stir evenly, then add sodium carbonate to the solution and stir evenly to prepare a Na2CO3-APAM mixed solution, so that the APAM concentration is the designed concentration and the Na2CO3 concentration is 1 mol / L.

[0045] (2) Injection of cementing solution into the sand body: Surface spraying is selected as the cementing construction method. First, the designed amount of CaCl2-HPMA mixed solution (cementing solution A) is sprayed onto the surface of the sand body. After standing for a period of time greater than or equal to the preset interval, cementing solution A is allowed to completely penetrate the sand sample. Then, an equal volume of Na2CO3-APAM mixed solution (cementing solution B) is sprayed onto the surface of the sand sample. After standing for a period of time greater than or equal to the preset interval, cementing solution B is allowed to completely penetrate the sand sample. This constitutes one complete spraying cycle. The above spraying cycle is repeated until the designed number of cycles is reached. Cementing solution is allowed to flow out from the bottom of the sand sample through the metal orifice plate at any time during the entire spraying process. After completing the designed spraying cycle, the sand body is allowed to stand for a preset curing time, and the cementing is completed.

[0046] Example 1

[0047] In this embodiment, the sand particles to be cemented are crushed quartz sand, with particle sizes ranging from 0.075mm to 2mm. Four working conditions, A1-A4, are implemented. (Reference) Figure 1 A sand-binding device was set up for testing. The acrylic tube mold 3 had a height of 8 cm and an inner diameter of 4 cm. After the bonding device was assembled, loose quartz sand particles were poured into a container consisting of the acrylic tube mold 3 and a metal perforated plate 6. The sample was prepared using a layered compaction method. After compaction and leveling, a layer of filter paper 2 was placed on the upper surface of the sand body, forming a cylindrical sand body 4 with a height of 8 cm and a diameter of 4 cm. The mass of the cylindrical sand body was 170.90 g, and the dry density was 1.7 g / cm³. 3 After sample preparation, the steps of preparing the cementing solution and injecting the cementing solution into the sand body are carried out. The operation process is the same as described above. The test design parameters and strength values ​​under different working conditions are shown in Table 1.

[0048] Table 1

[0049]

[0050]

[0051] Test method:

[0052] After cementation, the moist unsaturated cemented sand was immediately demolded, and an unconfined uniaxial compressive strength test was immediately conducted. After the uniaxial compressive strength test, the calcium carbonate content of the cemented sand was determined by hydrochloric acid washing.

[0053] Test results:

[0054] The uniaxial compressive strength results are shown in Table 1 and Figure 3 . Figure 3These represent the unconfined compressive strength (UCS) and calcium carbonate content of cemented sand bodies under working conditions A1-A4. From working condition A1, it can be seen that calcium carbonate generated solely from the metathesis of calcium chloride and sodium carbonate is insufficient to effectively cement sand particles, with a cemented sand body UCS of only 0.03 MPa. When 2 g / L APAM is added to regulate calcium carbonate crystallization, the sand body UCS increases to 0.14 MPa; when 3 g / L HPMA is added to regulate calcium carbonate crystallization, the sand body UCS increases to 0.24 MPa. The cementing effect of calcium carbonate precipitation induced by both HPMA and APAM is significantly improved, with the wet unsaturated cemented sand body achieving a UCS of 0.55 MPa, at which point the calcium carbonate content is 4.6%.

[0055] Figure 6 SEM images of cemented sand bodies under conditions A1 and A4 are shown. Smooth areas marked represent the smooth surfaces of sand grains, and small particles marked represent calcium carbonate precipitates. A large amount of calcium carbonate crystals were deposited on the surface of the sand grains under both conditions. Figure 6 (a)(b), For condition A1, without the addition of polymer, CaCO3 presents as cubic calcite, with different CaCO3 particles scattered randomly on the surface of the sand grains. In this case, the calcium carbonate precipitation has a very weak cementing effect on the sand grains. For example... Figure 6 (c)(d) For operating condition A4, when HPMA and APAM are jointly involved in regulation, CaCO3 appears as peanut-shaped or irregularly shaped particles. Many CaCO3 particles combine to form large-volume agglomerates. CaCO3 particles deposit on the surface of sand grains to form coating and filling patterns, and deposit at the contact points of sand grains to form cementing patterns. At this time, calcium carbonate precipitation has a strong cementing effect on sand grains.

[0056] Example 2

[0057] The sand particles selected for this embodiment were sea sand from Rizhao City, Shandong Province, with a particle size between 0.1 mm and 1 mm. Three working conditions, B1-B3, were implemented. The sand bonding device and sand sample preparation process were the same as in Example 1. The prepared sand mass was 170.90 g, and the dry density was 1.7 g / cm³. 3 After sample preparation, the steps of preparing the cementing solution and injecting the cementing solution into the sand body are carried out. The operation process is the same as in Example 1. The test design parameters and strength values ​​under different working conditions are shown in Table 2.

[0058] Table 2

[0059]

[0060]

[0061] Test method:

[0062] After cementation is completed, the damp unsaturated cemented sand body is immediately demolded, and an unconfined uniaxial compressive strength test is immediately conducted.

[0063] Test results:

[0064] Figure 4 The figure shows the unconfined compressive strength (UCS) of the cemented sand under working conditions B1-B3. As can be seen from the figure, the strength of the cemented sand increases when the HPMA concentration is 3 g / L and the APAM concentration increases from 0.4 g / L to 2 g / L. The UCS of the cemented sand increases significantly to 0.46 MPa when the HPMA concentration is 3 g / L and the APAM concentration is 2 g / L.

[0065] Example 3

[0066] In this embodiment, the sand particles to be cemented are crushed quartz sand, with particle sizes ranging from 0.075mm to 2mm. (Reference) Figure 2 A sand-binding device was set up, with an acrylic tube mold 3 having a height of 30cm and an inner diameter of 4cm. After the binding device was assembled, loose quartz sand particles were poured into a container consisting of the acrylic tube mold 3 and a metal perforated plate 6. A layered compaction method was used for sample preparation. After compaction and leveling, a layer of filter paper 2 was placed on the upper surface of the sand body, resulting in a cylindrical sand body 4 with a height of 30cm and a diameter of 4cm. The mass of the cylindrical sand body was 640.87g, and its dry density was 1.7g / cm³. 3 After sample preparation, the steps of preparing the cementing solution and injecting the cementing solution into the sand body are carried out. The operation process is the same as in Example 1, and the experimental design parameters are shown in Table 3.

[0067] Table 3

[0068]

[0069] Test method:

[0070] After cementation, the moist unsaturated cemented sand body was immediately demolded, and the cemented sand body, with a height of 30cm and a diameter of 4cm, was cut into three equal parts, named C1 (height 0-10cm), C2 (height 10cm-20cm), and C3 (height 20cm-30cm) from top to bottom. The upper and lower surfaces of sand samples C1-C3 were polished to a height of 8cm. At this point, the length-to-diameter ratio of sand samples C1-C3 was 2:1, and an unconfined uniaxial compressive strength test was immediately performed. After the uniaxial compressive strength test, the calcium carbonate content of the cemented sand samples was determined by hydrochloric acid washing.

[0071] Test results:

[0072] Figure 5The figures show the unconfined compressive strength (UCS) and calcium carbonate content of cemented sand samples C1-C3. As can be seen from the figure, the surface spraying method can effectively cement the entire sand body with a height of 30 cm and a diameter of 4 cm. The highest UCS for cemented sand sample C1 at the top is 1.32 MPa, while the UCS for sand samples C2 in the middle and C3 at the bottom are similar, at 0.80 MPa and 0.81 MPa, respectively. The calcium carbonate content follows the same trend as the UCS, with the highest at the top (8.3%), and similar values ​​at the middle and bottom (5.8% and 5.0%, respectively). This example demonstrates that the method of using dual polymers to induce calcium carbonate precipitation and cement loose sand particles has a deep effective cementing range.

[0073] In the description of this application, it should be understood that the terms "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0074] In the description of this application, "multiple" means two or more.

[0075] In the description of this application, "A and / or B" can include any of the cases of A alone, B alone, or A and B, where A and B are merely examples and can be any technical feature connected by "and / or" in this application.

[0076] In this application, the order in which the steps are written does not imply a strict execution order and does not limit the implementation process. The specific execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps in this application can be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0077] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for inducing calcium carbonate precipitation and cementing loose sand particles using a dual polymer, characterized in that, Follow these steps: (1) Preparation of cementing solution A: First, dissolve hydrolyzed polymaleic anhydride in water and stir evenly, then add calcium chloride to the solution and stir evenly to prepare a CaCl2-HPMA mixed solution. (2) Preparation of cementing solution B: First, dissolve anionic polyacrylamide in water and stir evenly, then add sodium carbonate to the solution and stir evenly to prepare a Na2CO3-APAM mixed solution. (3) After injecting the CaCl2-HPMA mixed solution into the loose sand body, inject an equal volume of the Na2CO3-APAM mixed solution into the loose sand body; one injection of cementing solution A and one injection of cementing solution B constitute one injection cycle; (4) After the sand body has undergone multiple injection cycles to complete the total injection volume designed, the cementation is completed.

2. The method for inducing calcium carbonate precipitation and cementing loose sand particles according to claim 1, characterized in that, In step (1), the concentration of hydrolyzed polymaleic anhydride is 2 g / L-3 g / L, the molecular weight of hydrolyzed polymaleic anhydride is 400 g / mol-800 g / mol, and the concentration of calcium chloride is 0.5 mol / L-1 mol / L.

3. The method for inducing calcium carbonate precipitation and cementing loose sand particles by a dual polymer according to claim 1, characterized in that, In step (2), the concentration of polyacrylamide is 1 g / L-2 g / L, the molecular weight of polyacrylamide is 6,000,000 g / mol-1,500,000 g / mol, and the concentration of sodium carbonate is 0.5 mol / L-1 mol / L.

4. The method for inducing calcium carbonate precipitation and cementing loose sand particles by a dual polymer according to claim 1, characterized in that, In step (3), the injection volume of cementing liquid A or cementing liquid B in a single injection cycle is 25%-50% of the total pore volume of the sand body, and the number of injection cycles is greater than or equal to 8.

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