CN120622899A - Thixotropic cement paste and preparation method thereof - Google Patents
Thixotropic cement paste and preparation method thereofInfo
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- CN120622899A CN120622899A CN202510754306.4A CN202510754306A CN120622899A CN 120622899 A CN120622899 A CN 120622899A CN 202510754306 A CN202510754306 A CN 202510754306A CN 120622899 A CN120622899 A CN 120622899A
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/42—Compositions for cementing, e.g. for cementing casings into boreholes; Compositions for plugging, e.g. for killing wells
- C09K8/428—Compositions for cementing, e.g. for cementing casings into boreholes; Compositions for plugging, e.g. for killing wells for squeeze cementing, e.g. for repairing
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/24—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing alkyl, ammonium or metal silicates; containing silica sols
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- C—CHEMISTRY; METALLURGY
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- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/42—Compositions for cementing, e.g. for cementing casings into boreholes; Compositions for plugging, e.g. for killing wells
- C09K8/46—Compositions for cementing, e.g. for cementing casings into boreholes; Compositions for plugging, e.g. for killing wells containing inorganic binders, e.g. Portland cement
- C09K8/467—Compositions for cementing, e.g. for cementing casings into boreholes; Compositions for plugging, e.g. for killing wells containing inorganic binders, e.g. Portland cement containing additives for specific purposes
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- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/42—Compositions for cementing, e.g. for cementing casings into boreholes; Compositions for plugging, e.g. for killing wells
- C09K8/46—Compositions for cementing, e.g. for cementing casings into boreholes; Compositions for plugging, e.g. for killing wells containing inorganic binders, e.g. Portland cement
- C09K8/467—Compositions for cementing, e.g. for cementing casings into boreholes; Compositions for plugging, e.g. for killing wells containing inorganic binders, e.g. Portland cement containing additives for specific purposes
- C09K8/487—Fluid loss control additives; Additives for reducing or preventing circulation loss
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/20—Resistance against chemical, physical or biological attack
- C04B2111/27—Water resistance, i.e. waterproof or water-repellent materials
- C04B2111/275—Making materials water insoluble
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
- C04B2201/20—Mortars, concrete or artificial stone characterised by specific physical values for the density
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
- C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
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- Chemical Kinetics & Catalysis (AREA)
- Structural Engineering (AREA)
- Curing Cements, Concrete, And Artificial Stone (AREA)
Abstract
本发明属于油田固井水泥浆技术领域，具体涉及一种触变水泥浆及其制备方法。本发明提供的触变水泥浆，包括：水、干粉材料、改性硅溶胶、聚合物类降失水剂和其他外加剂。本发明的水泥浆具有粘弹性、水下不分散、触变性及堵漏特性。
The present invention belongs to the technical field of oilfield cementing slurries, specifically relating to a thixotropic cement slurry and its preparation method. The thixotropic cement slurry provided by the present invention comprises water, dry powder material, modified silica sol, a polymer-based fluid loss additive, and other admixtures. The cement slurry of the present invention exhibits viscoelasticity, underwater non-dispersion, thixotropy, and leak-proof properties.
Description
Technical Field
The invention belongs to the technical field of oilfield cementing cement paste, and particularly relates to thixotropic cement paste and a preparation method thereof.
Background
Lost circulation is one of the main causes of increased costs in well construction. From hundreds of thousands of dollars lost due to moderate loss of drilling or cementing fluid, to tens of thousands of dollars that have to be invested in sidetracking or rescue-hole handling lost circulation. Thixotropic cement slurries are one means of coping with lost circulation. On one hand, the thixotropic cement paste has self-supporting performance in an annulus, and partial hydrostatic column pressure is shared on the surface of a stratum and the casing wall, so that the thixotropic cement paste is beneficial to reducing the leakage of the stratum with low fracture pressure, and on the other hand, when the thixotropic cement paste enters a leakage layer, the gel strength and the flow resistance of the cement paste are gradually increased and the leakage amount is gradually reduced due to the reduction of the shear rate, so that the cement paste is rapidly hydrated and the leakage layer is solidified.
In the prior art, thixotropic cement paste implementation approaches are largely divided into four categories. The first type is clay-based cement slurry system, the pre-hydrated clay presents a 'clamping house' structure in the cement slurry, and can endow the cement slurry with gel strength and thixotropic property, for example, as reported in U.S. patent No. 10479923, hectorite is adoptedRD, BYK company) clay mineral is thixotropic agent, the second type is sulfate cement slurry system, calcium sulfate, aluminum sulfate, ferrous sulfate or C 3 A phase in cement is often utilized to generate ettringite, the ettringite is adsorbed on the surface of cement particles in a needle shape and plays a role of connecting different cement particles, the connection is destroyed when stirring and is formed again when standing, thus the cement slurry gel strength and thixotropy can be endowed, for example, U.S. Pat. No. 3, 3847635 reports that semi-hydrated gypsum is adopted as thixotropic agent, the third type is a crosslinked polymer system, in-situ crosslinked cellulose ether, polyvinyl alcohol, polyacrylamide and the like of titanium-containing, zirconium-chromium compounds in cement slurry body are used, when the cement slurry is static, a crosslinking reaction takes place rapidly, and a net-shaped structure is formed, for example, as reported in U.S. Pat. No. 4515216, the thixotropic cellulose ether is prepared by adopting titanium chelate crosslinked, and the fourth type is associated or self-assembled system, as second-order cationic energy is adopted to enable the viscoelastic surfactant to generate a ' worm ' structure ' in aqueous solution, the structure is recovered when shearing destruction and standing, and the cement slurry has the thixotropic activity of patent, for example, the cement slurry has the viscosity and the oxygen-blocking property of 9695351 is endowed with the thixotropic property.
Although the four thixotropic cement slurries have some mature methods, along with the expansion of the oil and gas drilling field and higher requirements on the technical scheme, certain defects still exist, and the method is characterized in that clay ore is used as a thixotropic agent, the pre-hydrolysis and slurry making process is needed, sulfate is used as the thixotropic agent, thixotropy is difficult to be exerted on high-sulfate-resistance cement (low C 3 A content), a crosslinked polymer system is used for constructing the thixotropic cement slurry, engineering accidents are easy to occur when the crosslinking reaction is not well controlled, and an association or self-assembly system is used, so that an expensive viscoelastic surfactant is needed. Thus, the field is still the direction and focus of research by researchers in the industry.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides thixotropic cement paste and a preparation method thereof.
Specifically, the invention is realized by the following technical scheme:
In a first aspect, the invention provides a thixotropic cement paste comprising water, a dry powder material, a modified silica sol, a polymer fluid loss additive and other additives.
The thixotropic cement paste comprises, by 100 parts of dry powder material, 38-106 parts of water, 0.3-6 parts of modified silica sol, 2-12 parts of polymer fluid loss agent and 0.5-1.3 parts of other additives.
The thixotropic cement paste comprises, by 100 parts of dry powder material, 60-100 parts of water, 0.5-5 parts of modified silica sol, 3-10 parts of polymer fluid loss agent and 0.6-1.3 parts of other additives.
The thixotropic cement paste is characterized in that the dry powder material is oil well cement or a mixture of oil well cement and auxiliary dry powder material.
The thixotropic cement paste is characterized in that the auxiliary dry powder material is one or more of silica fume, fly ash, slag and metakaolin.
The thixotropic cement paste is characterized in that the modified silica sol is an epoxy silane coupling agent modified silica sol.
The thixotropic cement paste is characterized in that the polymer fluid loss agent is a polymer formed by copolymerizing monomers through aqueous solution free radicals, wherein the monomers comprise AMPS monomers and acrylamide monomers.
The thixotropic cement paste is characterized in that the acrylamide monomer is one or more of acrylamide, N-dimethylformamide and N, N-diethylformamide.
The thixotropic cement paste has the granularity of 5-50 nm, the solid content of 20-40%, and the molecular weight of 20-200 ten thousand and the solid content of 10-30%.
The thixotropic cement paste comprises one or more of retarder, accelerator, defoamer, early strength agent, dispersant and plugging material.
The thixotropic cement paste is characterized in that the retarder is a mixture of a common retarder for well cementation and silane, wherein the common retarder for well cementation is a carboxylic acid polymer synthesized by lignin, organic phosphoric acid, gluconic acid and carboxylic acid monomers.
The thixotropic cement paste is characterized in that the silane is one or two of aminosilane and epoxy silane.
The thixotropic cement paste, wherein the coagulant is hydrated calcium silicate gel.
The thixotropic cement paste comprises polyether defoamer, organic silicon defoamer or mineral oil defoamer.
The thixotropic cement paste, wherein the early strength agent comprises chloride salt or sulfate.
The thixotropic cement paste comprises a naphthalene dispersant or an aliphatic dispersant.
The thixotropic cement paste comprises one or more of chopped glass fibers, chopped polypropylene fibers, polyester sheets, mica sheets, glass sheets, calcium carbonate particles, coal powder particles and rock asphalt particles with different lengths.
In a second aspect, the invention also provides a preparation method of the thixotropic cement paste, which comprises the following steps:
(1) Adding the polymer fluid loss agent and the modified silica sol into water, and uniformly stirring;
(2) Adding other additives, and uniformly stirring to obtain mixed water;
(3) And mixing the dry powder material with the mixed water to obtain thixotropic cement paste.
In a third aspect, the invention also provides a thixotropic cement paste which is prepared by the preparation method.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
(1) The thixotropic cement paste has thixotropic property, namely after the cement paste is tested by a rotary viscometer and is stood for 10 seconds and 10 minutes, the value added before and after the standing is respectively not lower than 10 and 25, the larger the value added is, the larger the thixotropic property is, and again, according to a well cementation cement paste thixotropic property evaluation method of a pressurizing thickener (laboratory research and discussion, 39 volumes of 4 th period), the phenomenon of 'shear thinning' after starting is obvious on a thickening curve obtained by the experiment, the phenomenon can be found at 135 ℃ and within, and the more obvious the phenomenon is, the larger the thixotropic property of the cement paste is;
(2) The thixotropic cement paste has viscoelasticity, wherein the amplitude scanning is carried out by an oscillation rheometer, the cement paste has an obvious linear viscoelasticity area and a flow point, and the storage modulus (G ') is larger than the loss modulus (G') in the linear viscoelasticity area;
(3) The thixotropic cement paste has the characteristics of no dispersion under water, namely 50ml of fresh water is filled in a 100ml beaker, 10ml of cement paste is sucked by a syringe, the cement paste is pumped into the beaker on the water surface of the beaker, the turbidity degree of the fresh water in the beaker is observed, the pH value is tested, the lower the turbidity degree is, the better the water-resistant dispersion performance of the cement paste is, the water-resistant dispersion performance of the cement paste is tested by adopting the method, the fresh water in the flask is almost free from turbidity, and the pH value can maintain the neutral pH value of the fresh water;
(4) The thixotropic cement paste has the plugging property that plugging materials are introduced into the cement paste with the characteristics of viscoelasticity, no underwater dispersion, thixotropy and plugging, so that the plugging capability of the cement paste can be improved;
(5) According to the method, cement paste with the water cement ratio of 0.40-1.20 can be prepared, the characteristics of thixotropy, viscoelasticity and non-dispersion under water can be simultaneously realized in the same cement paste, and the basic performance of the cement paste meets the requirements of well cementation engineering.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention.
FIGS. 1 and 2 show the thickening curves of cement slurries numbered 9# and comparative example 2# during a shutdown test, respectively;
FIG. 3 is a graph showing the water dispersion resistance of cement paste of No. 9 and comparative example No. 2;
FIG. 4 is an amplitude sweep for comparative example 1 and cement slurry # 5;
FIG. 5 is an amplitude sweep for comparative example 3 and a cement slurry numbered 7;
FIG. 6 is a graph of exotherms of 0.70 cement to cement slurries monitored by an isothermal calorimeter (45 ℃) for different amounts of modified silica sol and silica sol introduced.
Detailed Description
The present invention will be described in detail with reference to the following embodiments for a full understanding of the objects, features, and effects of the present invention. The process of the present invention is carried out by methods or apparatus conventional in the art, except as described below. The following terms have the meanings commonly understood by those skilled in the art unless otherwise indicated.
When a range of values is disclosed herein, the range is considered to be continuous and includes both the minimum and maximum values for the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values of the range is included. Further, when multiple range description features or characteristics are provided, the ranges may be combined. In other words, unless otherwise indicated, all ranges disclosed herein are to be understood to include any and all subranges subsumed therein.
The thixotropic cement paste comprises water, dry powder material, modified silica sol, polymer fluid loss agent and other additives.
The synergistic effect of the components in the thixotropic cement paste is inferred to be that carboxyl groups on the polymer-type fluid loss agent polymer chains form ionic bond adsorption on the surfaces of cement particles, and meanwhile, modified silica sol nano particles and hydrophilic groups on the polymer-type fluid loss agent polymer chains form hydrogen bond adsorption, so that the modified silica sol plays a role in bridge connection in the polymer cement paste, and the connection has the recovery characteristics of breaking and removing during shearing and macroscopically shows the thixotropic property, viscoelasticity and underwater non-dispersion characteristic of the cement paste.
The following describes the components of the thixotropic cement paste of the present invention in detail.
Water and its preparation method
The thixotropic cement paste adopts fresh water.
In some preferred embodiments, the thixotropic cement paste of the present invention comprises 38-106 parts water per 100 parts dry powder material.
It is further preferred that the thixotropic cement paste of the present invention comprises 60 to 100 parts of water per 100 parts of dry powder material.
Dry powder material
In cement paste, the main function of the dry powder material is to form a solid structure through hydration reaction, so that the cement paste is endowed with necessary performances to meet different engineering requirements.
The dry powder material adopted by the invention is oil well cement of different grades or cement mixture mixed with auxiliary dry powder materials (such as silica fume, fly ash, slag and metakaolin).
In some preferred embodiments, the dry powder materials employed in the present invention are API grade G cements or mixtures of API grade G cements with crystalline silica.
The crystalline silicon dioxide is prepared by physically mixing 60 parts of 300-mesh silicon powder, 20 parts of 70-mesh silicon powder and 20 parts of 800-mesh silicon powder.
In the invention, the blending ratio of water and dry powder material (i.e. water-ash ratio) is 0.44-1.20 according to engineering requirements
Wherein the water comprises water in the liquid additive when calculating the water to ash ratio.
Modified silica sol
In the art, silica sols have shown a "setting accelerator" effect in cement slurries, and the inventors have surprisingly found that modified silica sols have shown a "setting retarder" effect in cement slurries (i.e., as their loading increases, the setting time of the cement slurries increases).
The invention can dispense with or reduce the dosage of the retarder of the oil well cement by applying the modified silica sol, or can obtain the setting time and the cement slurry performance required by engineering application by combining the modified silica sol and the silica sol.
In some preferred embodiments, the modified silica sol is a silane coupling agent modified silica sol, and more preferably an epoxy silane coupling agent modified silica sol.
In the present invention, the epoxy silane coupling agent modified silica sol is a composite material in which an epoxy silane coupling agent is chemically introduced into a silica sol structure. Which can be obtained by existing methods or commercially available. For example, the product can be prepared according to the method described in document "Greenwood P,Gevert B.Aqueous silane modified silica sols:Theory and preparation[J].Pigment&Resin Technology,2011,40(5):275-284.DOI:10.1108/03699421111176171", or can be purchased directly from Nouryon company LEVASIL CC301, LEVASIL CC151, LEVASIL CC401.
In some preferred embodiments, the particle size of the modified silica sol is from 5nm to 50nm, with particle sizes from 7nm to 15nm being even more preferred. The solid content of the modified silica sol is 20% -40%. The modified silica sol is used in an amount of 5% -15% (based on the mass of water).
The thixotropic property of the cement paste is increased along with the increase of the dosage of the modified silica sol and the polymer fluid loss agent. When the addition amount of the modified silica sol is larger, the thixotropic property of the cement paste is larger; too little, little thixotropic. In some preferred embodiments, the modified silica sol in the thixotropic cement slurries of the present invention is present in an amount of 0.3 to 6 parts by weight based on 100 parts dry powder material.
It is further preferred that the modified silica sol in the thixotropic cement paste of the present invention is 0.5 to 5 parts by weight based on 100 parts of the dry powder material.
Polymer fluid loss additive
The fluid loss agent is mainly used for controlling the water loss of cement slurry in the construction process.
In the invention, the polymer fluid loss agent is a polymer formed by copolymerizing monomers through aqueous solution free radicals, wherein the monomers mainly comprise AMPS monomers and acrylamide monomers. The polymer fluid loss agent has wide sources and can be commercially purchased from the market belonging to the field.
In some preferred embodiments, the acrylamide-based monomer is one or more of acrylamide, N-dimethylformamide, N-diethylformamide.
In some preferred embodiments, the molecular weight of the polymeric fluid loss agent is 20-200 tens of thousands and the solids content is 10% -30%.
In some preferred embodiments, the polymeric fluid loss additive is used in an amount of 5% to 15% (based on the mass of water)
The thixotropic properties of cement slurries are related to modified silica sols and polymer-based fluid loss additives, and the amounts of the modified silica sols and polymer-based fluid loss additives increase and the thixotropic properties increase. In cement slurries with large cement ratios, the modified silica sol and polymer are used in large amounts.
In some preferred embodiments, the thixotropic cement paste of the present invention comprises 2 to 12 parts by weight of the polymeric fluid loss additive based on 100 parts dry powder material.
Further preferably, the thixotropic cement paste of the present invention comprises 3 to 10 parts by weight of the polymer-based fluid loss agent based on 100 parts by weight of the dry powder material.
Other additives
To meet specific engineering requirements, different chemical additives can be added to the cement slurries of the present invention, thereby altering their properties.
Optionally, in order to extend the setting time of the cement slurry, allowing longer operating times and adapting to high temperature environments, retarders may be added to the cement slurry of the present invention.
The retarder adopted by the invention is a mixture of a common retarder for well cementation and silane. Wherein, the well cementation is usually performed by retarder, such as carboxylic acid polymer synthesized by lignin, organic phosphoric acid, gluconic acid and carboxylic acid monomer, and the silane is amino silane, epoxy silane or the mixture of the amino silane and the epoxy silane. Wherein, the retarder dosage is prepared according to the required thickening time. The retarder is widely available and commercially available from the market to which the art pertains.
Optionally, in order to accelerate the hydration reaction of the cement, shorten the setting time and make the cement reach the primary strength more quickly, a setting accelerator can be added into the cement slurry of the invention.
The setting accelerator used in the invention is a hydrated calcium silicate gel setting accelerator, such as Master X-Seed 100 of BASF corporation. Wherein the amount of the coagulant is formulated according to the setting time.
Optionally, in order to improve the compactness and strength of the cement paste structure, an antifoaming agent can be added into the cement paste, so that bubbles in the cement paste are reduced or eliminated, and the formation of pores is avoided.
Wherein, the defoamer adopted in the invention is a common defoamer for well cementation, such as polyethers, organic silicon and mineral oil. Wherein, the amount of the defoamer is added according to the required defoaming condition.
Optionally, in order to make the cement paste bear load faster, an early strength agent can be added into the cement paste.
Wherein, the early strength agent is a common early strength agent for well cementation, such as chloride and sulfate. The dosage of the early strength agent is regulated according to the required rheological property requirement.
Optionally, the cement paste can be added with dispersing agents for improving the fluidity of the cement paste, reducing the water consumption and simultaneously keeping good workability, thereby being beneficial to preparing high-strength concrete.
Wherein the dispersing agent is a common dispersing agent for well cementation, such as naphthalene and aliphatic. The amount of dispersant is added according to the desired rheological properties.
Optionally, a plugging material may be added to the cement slurries of the present invention to prevent or slow the flow of fluids through the cracks or holes.
The plugging materials adopted by the invention are common materials for oil fields, such as chopped glass fibers, chopped polypropylene fibers and the like with different lengths, such as polyester sheets, mica sheets, glass sheets and the like, such as calcium carbonate particles, coal particles, rock asphalt particles and the like, or composite plugging materials formed by the above various components are used for improving the plugging capability of cement paste. These lost circulation materials are widely available and commercially available from the market to which the art pertains.
In some preferred embodiments, the other additives of the present invention are present in an amount of 0.5 to 1.3 parts by weight based on 100 parts dry powder material.
Further preferably, the other additives of the present invention are present in an amount of 0.6 to 1.3 parts by weight based on 100 parts of the dry powder material.
On the other hand, the invention also provides a preparation method of the thixotropic cement paste, which comprises the following steps:
(1) Adding the polymer fluid loss agent and the modified silica sol into water, and uniformly stirring;
(2) Adding other additives, and uniformly stirring to obtain mixed water;
(3) And mixing the dry powder material with the mixed water to obtain thixotropic cement paste.
The thixotropic cement paste is prepared through compounding cement slurry with cement base dry powder material, regulating the amount of modified silica sol and polymer as water reducing agent to obtain stable cement paste with water-cement ratio of 0.40-1.20, and adding plugging material to obtain cement paste with viscoelasticity, no water dispersion, thixotropic property and plugging property. The cement paste prepared by the method can be used for cementing wells with narrow pressure windows, cementing wells with water injection wells around or containing high-pressure stratum water, cementing wells with easy-to-leak intervals and the like.
Examples
The invention is further illustrated by means of the following examples, which are not intended to limit the scope of the invention. The experimental methods without specific conditions noted in the following examples follow conventional methods and conditions. In the examples described below, the materials used are shown in Table 1 and are all commercially available without any particular explanation.
TABLE 1
Example 1
This example examined the effect of material feed sequencing in the compounding of water. Taking cement paste with a cement ratio of about 0.70 as an example. In Table 2, each numbered cement slurry comprises oil well cement SD G100G, fresh water 61G, fluid loss agent G80L 6G, dispersant F44L 0.8G, defoamer X60L 0.1G, retarder H21L 0.1G, modified silica sol M3010-1 2G and early strength agent A95L 2.0G. The mixing water preparation of each numbered cement slurry adopts different feeding sequences, and the qualitative description of the final mixing cement slurry performance is shown in table 2.
TABLE 2
As can be seen from table 2, the order of material addition when formulating the mix water has a significant impact on the final mix cement slurry properties. The analysis shows that in order to obtain cement slurry with good sedimentation stability, thixotropic property and water-resistant dispersibility, the addition should follow a certain order, namely, the polymer fluid loss agent and the modified silica sol are required to be added into water and stirred uniformly, and then the defoamer, retarder, early strength agent and dispersing agent are added.
Example 2
The present example examined the formulation and performance of cement slurries of different cement ratios. No. 5# -10# is the cement slurry provided by the invention, and comparative examples 1# and 2# use unmodified silica sol to prepare the cement slurry. From table 3, the following conclusion can be reached.
(1) The basic properties of the No. 5# -10 cement paste, such as paste rheology (300-turn and 3-turn readings of a six-speed viscometer), density difference (upper and lower density difference of the cured cement paste), water loss (water loss of API specification) and strength (compressive strength of the cured cement paste) reach the general requirements of the well cementation engineering.
(2) After the cement paste with the number of 5# and 10# is tested by a 6-speed viscometer for 10s and 10min, the value of the 3-turn reading is not less than 10 and 25 before and after the standing, the larger the value is, which shows that the thixotropic property of the cement paste is larger, and in addition, the cement paste with the number of 9# and the comparative example 2# is selected and passed through the "shutdown experiment" in the well cementation cement paste thixotropic property evaluation method of a pressurizing and thickening instrument "(laboratory research and discussion, 39 volume, 4 th). The thickening curve for cement # 9 showed a "shear thinning" after start-up, which was not apparent in comparison to the cement slurry of comparative example # 2. See fig. 1 and 2 for details.
(3) By adopting the method described in the summary of the invention, the cement paste No. 5-10 has obvious water-dispersion resistance, while comparative examples No. 1, no. 2 and No. 3 have substantially no water-dispersion resistance. Wherein, the water-dispersion resistant effect graphs of cement slurries of comparative example No. 2 and No. 9 are shown in FIG. 3.
TABLE 3 Table 3
Note that the coincidence "-" in table 3 indicates no test.
Example 3
In the embodiment, the viscoelasticity of the cement paste is inspected by adopting vibration rheometer amplitude scanning. The amplitude scan results are shown in FIG. 4 for cement slurry numbered 5 and comparative example 1 at a water to cement ratio of 0.44, and in FIG. 5 for cement slurry numbered 7 and comparative example 3 at a water to cement ratio of 1.20. As can be seen from fig. 4 and 5, at water cement ratios of 0.44 and 1.20, the cement slurries numbered 5# and 7# containing the modified silica sol have distinct linear viscoelastic regions and greater flow points than the cement slurries of comparative examples 1# and 3# containing the unmodified silica sol, and the storage modulus (G') is greater than the loss modulus (G ") in the linear viscoelastic regions.
Example 4
This example examined the effect of modified silica sol on cement slurry cure. The cement paste with the water cement ratio of 0.70, numbered 6 in table 3, was selected AS a base paste, and when the modified silica sol CC301 and the unmodified silica sol AS30 were 1.0%, 1.5% and 2.0%, respectively, the exotherm of the cement paste at 45 ℃ was monitored (obtained by TAM air calorimeter, TA company) and the result was shown in fig. 6. AS can be seen from fig. 6, the unmodified silica sol AS30 exhibited a "set accelerator effect" and the modified silica sol CC301 exhibited a "set retarder effect" AS compared to the reference cement slurry. When the cement paste formulation is designed, the use amount of the oil well cement retarder can be saved or reduced by utilizing the retarding effect of the modified silica sol, or the setting time and the cement paste performance required by engineering application can be obtained by combining the modified silica sol and the silica sol.
The present invention has been disclosed above in terms of preferred embodiments, but it will be understood by those skilled in the art that these embodiments are merely illustrative of the present invention and should not be construed as limiting the scope of the present invention. It should be noted that all changes and substitutions equivalent to those of the embodiments are considered to be covered by the scope of the claims of the present invention. The scope of the invention should, therefore, be determined with reference to the appended claims.
Claims (15)
1. The thixotropic cement paste is characterized by comprising water, dry powder materials, modified silica sol, polymer fluid loss agent and other additives.
2. The thixotropic cement paste according to claim 1, wherein the thixotropic cement paste comprises 38 to 106 parts of water, 0.3 to 6 parts of modified silica sol, 2 to 12 parts of polymer fluid loss agent and 0.5 to 1.3 parts of other additives based on 100 parts of dry powder material.
3. The thixotropic cement paste according to claim 2, wherein the thixotropic cement paste comprises 60-100 parts of water, 0.5-5 parts of modified silica sol, 3-10 parts of polymer fluid loss agent and 0.6-1.3 parts of other additives based on 100 parts of dry powder material.
4. A thixotropic cement paste according to any one of claims 1 to 3, wherein the dry powder material is oil well cement or a mixture of oil well cement and an auxiliary dry powder material.
5. The thixotropic cement paste of claim 4, wherein the auxiliary dry powder material is one or more of silica fume, fly ash, slag, metakaolin.
6. A thixotropic cement paste according to any one of claims 1 to 3, characterised in that the modified silica sol is an epoxy silane coupling agent modified silica sol.
7. The thixotropic cement paste according to any one of claims 1 to 3, wherein the polymer-based fluid loss agent is a polymer obtained by copolymerizing monomers by aqueous solution free radicals, wherein the monomers comprise AMPS monomers and acrylamide monomers.
8. The thixotropic cement paste of claim 7, wherein said acrylamide-based monomer is one or more of acrylamide, N-dimethylformamide, N-diethylformamide.
9. A thixotropic cement paste according to any one of claims 1 to 3, wherein the modified silica sol has a particle size of 5nm to 50nm and a solid content of 20% to 40%, and the polymer-based fluid loss agent has a molecular weight of 20 ten thousand to 200 ten thousand and a solid content of 10% to 30%.
10. A thixotropic cement paste according to any one of claims 1 to 3, characterised in that said other additives comprise, but are not limited to, one or more of retarders, setting accelerators, defoamers, early strength agents, dispersants, plugging materials.
11. The thixotropic cement paste of claim 10, wherein the retarder is a mixture of a conventional retarder for well cementation and silane, wherein the conventional retarder for well cementation is a carboxylic acid polymer synthesized by lignin, organic phosphoric acid, gluconic acid and carboxylic acid monomers, and the silane is one or two of aminosilane and epoxysilane.
12. The thixotropic cement paste according to claim 10, wherein the setting accelerator is a hydrated calcium silicate gel, the defoamer comprises a polyether defoamer, an organosilicon defoamer or a mineral oil defoamer, the early strength agent comprises a chloride salt or a sulfate salt, and the dispersant comprises a naphthalene-based dispersant or an aliphatic-based dispersant.
13. The thixotropic cement paste of claim 10, wherein the plugging material comprises one or more of chopped glass fibers, chopped polypropylene fibers, polyester flakes, mica flakes, glass flakes, calcium carbonate particles, coal particles, rock asphalt particles of varying lengths.
14. A method of preparing a thixotropic cement paste according to any one of claims 1 to 13, comprising:
(1) Adding the polymer fluid loss agent and the modified silica sol into water, and uniformly stirring;
(2) Adding other additives, and uniformly stirring to obtain mixed water;
(3) And mixing the dry powder material with the mixed water to obtain thixotropic cement paste.
15. A thixotropic cement paste prepared by the preparation method according to claim 14.
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