Anti-freezing coagulant, application thereof and well cementation cement slurry system

Abstract

The invention relates to the field of oil field well cementation, and discloses an anti-freezing coagulant, application thereof and a well cementation cement slurry system. The anti-freezing coagulant comprises a water-soluble inorganic salt, a water-soluble organic compound, a surfactant and optional water, wherein the water-soluble organic compound comprises water-soluble cellulose, and further comprises at least one of a water-soluble alcohol compound, a water-soluble carboxylic acid compound and a water-soluble amide compound. The anti-freezing coagulant provided by the invention has anti-freezing and coagulation-accelerating effects, can enable negative-temperature well cementation cement slurry to have good anti-freezing performance, good rheological property, moderate thickening time and relatively high compressive strength, and can meet construction requirements.

Description

Technical Field

[0001] The present invention relates to the field of oilfield cementing, and particularly to an antifreeze accelerating agent, its application in low-temperature cementing, and a cement slurry system for cementing. Background Art

[0002] In important oil and gas reservoirs in polar regions, permafrost areas are widely distributed, with a temperature of -5 to -8 °C, a formation ice content as high as 80%, and a depth of up to 500 m. In a conventional cement slurry system for cementing, the strength development is extremely slow under low-temperature conditions. When the ambient temperature is lower than 20 °C, the induction period of the cement is prolonged and the cement hydration is slow. When the ambient temperature is lower than 0 °C, since the water in the cement slurry condenses and freezes, and even does not participate in the cement hydration reaction at all, the cement slurry does not solidify and has no strength, making it difficult to meet the requirements of cementing and posing a great challenge to the cementing operation.

[0003] Scholars have conducted some research on the influence of negative temperature on the hydration process of cement slurry. It is generally believed that the physical influence of negative temperature on cement hydration reaction lies in: in the initial stage of cement hydration, the continuous phase in the cement slurry is liquid. As hydration proceeds, the gel-like products increase continuously, and the system gradually transforms into a solid with a gelling mineral as the continuous phase, completing the liquid-solid transformation. When the external ambient temperature gradually drops below the freezing point of the liquid phase of the cement slurry, ice first nucleates and grows in the continuous liquid phase of the large pores. As the temperature further decreases, the ice grows into the surface of the cement particles and pores with smaller sizes, forming a locally closed hydraulic system. In the cement slurry system, due to the phase change of water molecules on the surface of the cement particles to ice, the liquid phase pressure decreases and no longer penetrates into the interior of the cement particles, and the hydration reaction slows down until it stops. In addition, based on the physical process of the volume expansion of water during freezing, if the unfilled pores inside the hydraulic system are not sufficient to accommodate the approximately 9% volume expansion generated by freezing, the excess water will flow outwards and form pressure, destroying the structure of the initial hydration products of the cement and preventing it from cementing and solidifying to form strength.

[0004] At present, there are few anti-freezing technologies for cement slurries in low-temperature environments and they are mostly used in the construction field. To ensure the construction of concrete in winter, technicians in the construction field often use alcohols, alcohol ethers, chlorinated hydrocarbons, inorganic salts, etc. as anti-freezing agents. By changing the liquid phase concentration of concrete, the freezing point is reduced, and the ability of concrete to resist freezing damage is enhanced. However, these additives have little effect on concrete below -2°C. In the construction of building cement and concrete in a negative temperature environment, it is usually necessary to preheat water and aggregates, cover the surface with heat-insulating materials, lay heating piles in greenhouses and other physical methods to keep warm and heat up to ensure the low-temperature hydration of cement. Obviously, these means cannot be applied to the cementing engineering of oil and gas wells several thousand meters deep. In addition, the mineral composition, performance requirements and application environment of the cement slurry used in the cementing field are also different from those of building cement. As a heavy industry that affects the national economy and people's livelihood, the petroleum industry has the characteristics of high investment, high risk and strict technical requirements. To ensure construction safety and quality, in addition to the mechanical strength performance of the cementing cement slurry system needing to meet the requirement of stabilizing the casing (compressive strength ≥ 3.5 MPa), it also needs to meet good rheological properties to reduce the pumping pressure for easy injection into the well, an appropriate thickening time (too short cannot guarantee construction safety, too long will affect the cementing quality), and a low water loss (≤ 50 ml) to prevent wellbore collapse, gas channeling and a series of requirements. Otherwise, it will lead to cementing construction accidents at least, and the entire well will be scrapped at worst, causing huge economic losses. After investigation, it is found that there are few types of cement slurries used in low-temperature environments.

[0005] "A liquid colloid-filled low-temperature cementing cement slurry system" of CN201610841418.4 discloses a low-temperature cement slurry containing 100 parts of portland cement; 80 - 120 parts of ultrafine portland cement; 10 - 30 parts of hollow glass microspheres; 10 - 20 parts of microsilica; 8 - 12 parts of liquid colloid; 2 - 6 parts of early strength agent; 1 - 2 parts of drag reducer; 4 - 8 parts of fluid loss reducer; 1 - 2 parts of defoamer; and 120 - 150 parts of water. The density of this cement slurry can be adjusted between 1.35 - 1.65 g / cm 3 and it has high early strength at low temperatures, good thickening performance and fluidity, and small water loss, and can be used for cementing the deepwater surface section at about 15°C.

[0006] "A low-temperature cementing cement slurry system and composition" of CN201510786765.7 discloses a low-temperature cement slurry composed of 100 parts of oil well cement, 62 - 175 parts of oil well ultrafine cement, 7.3 - 23 parts of nano-silica, 10 - 32 parts of reactive calcium silicate, 15 - 50 parts of hollow glass microspheres, 3.6 - 10 parts of early strength agent, 3.2 - 8.6 parts of fluid loss reducer, 0.8 - 2.0 parts of dispersant, and 120 - 195 parts of water. The density of this cement slurry is between 1.30 - 1.60 g / cm3 and is suitable for cementing operations in the deep-sea low-temperature surface casing section at about 15°C.

[0007] There have been many studies on low-temperature cement slurries in domestic and foreign literature. Among them, some literature reported the PSD cement technology of Schlumberger Company. After curing for 16 hours at a simulated temperature of 11°C, the low-temperature cement slurry system reached 3.5 Mpa (Qi Fengzhong, Zhuang Xiaoqian, Tang Chunjing. Overview of CemCRETE Cement Slurry Cementing Technology [J]. Drilling Fluid & Completion Fluid, 2006, 23(6): 68-70); some literature conducted research on deepwater low-temperature cement slurries for the difficulties in deepwater surface cementing, such as slow strength development of low-temperature cement stone, shallow layer flow, and easy loss. It mainly included low-temperature early-strength cement, density reducers, and supporting additives. The density of this cement slurry was between 1.2 and 1.7 g / cm 3 3. It had fast low-temperature strength development and a stable system, and could be applied in the range of 4-20°C, with good comprehensive performance (Xi Fangzhu, Qu Jiansheng, Lü Guangming, etc. Research on Deepwater Low-Temperature Cement Slurry [J]. Oil Drilling & Production Technology, 2010, 32(1): 40-43); some literature aimed at the problem of slow early strength development in coalbed methane low-temperature cementing and deepwater surface casing cementing. By compounding colloidal SiO2, sulfates, and alkanolamines, a composite non-chlorine early-strength agent AA was developed. By adding lightweight materials and supporting additives to the cement, a low-temperature cement slurry system with a density of 1.35-1.87 g / cm 3 3 was formed. The compressive strength of this low-temperature cement slurry could reach 13 MPa at 30°C in 24 hours (Bu Yuhuan, Hou Xianhai, Guo Shenglai. Laboratory Study on Low-Temperature Cement Slurry System [J]. Drilling Fluid & Completion Fluid, 2016, 33(1): 79-83); there was also some literature that studied the changes in the conventional properties of low-temperature cement slurries before and after adding redispersible latex powder at different temperatures between 10°C and 60°C. It was found that redispersible latex powder could significantly reduce the permeability of cement stone, improve the interfacial bonding strength, and the thickening time was longer at lower curing temperatures (Wang Xuguang. Influence of Redispersible Latex Powder on the Properties of Low-Temperature Cement Slurry [J]. Drilling Fluid & Completion Fluid, 2015, 32(6): 65-71).

[0008] When the conventional cement system is in an ambient temperature below 0°C, since the water in the slurry freezes and does not participate in the cement hydration reaction, the cement slurry does not solidify and has no strength, making it difficult to meet the needs of cementing work. In the construction industry, technicians often use alcohols, alcohol ethers, chlorinated hydrocarbons, inorganic salts, etc. as antifreeze agents. By changing the liquid phase concentration of concrete, the freezing point is reduced to ensure that there is a liquid phase in concrete at negative temperatures, promoting cement hydration and enhancing the ability of concrete to resist freezing damage. However, these reagents have a great impact on the rheological properties and thickening time of cement slurry, and also affect the strength, so they cannot be directly used in complex oil and gas well construction projects.

[0009] It can be seen that in the field of well cementing in oil and gas wells, there are few reports on cement slurry systems in domestic and foreign cement slurry technologies that are truly applicable to low temperatures, especially to well cementing in negative temperature permafrost areas below 0°C. Even for low-density cement slurry systems at 4-8°C, there are not many, and the cost is relatively high, mostly applicable to deep-sea well cementing. Moreover, the antifreeze technology, which is the basic additive for negative temperature well cementing cement systems, is almost in a blank state, with very little relevant research, making it difficult to meet the needs of well cementing operations in frozen soil layers in polar cold sea areas. Therefore, the development of an antifreeze for negative temperature well cementing cement slurry is of great significance. Summary of the Invention

[0010] The object of the present invention is to overcome the problem existing in the prior art that when the conventional cement system is in an ambient temperature below 0°C, due to the condensation and freezing of the slurry water, which does not participate in the cement hydration reaction, resulting in the cement slurry not setting and having no strength, and it is difficult to meet the needs of well cementing work. The present invention provides an antifreeze and accelerating agent and its application in low-temperature well cementing, as well as a well cementing cement slurry system. This antifreeze and accelerating agent has both antifreeze and accelerating effects, can make the negative temperature well cementing cement slurry have good antifreeze performance, good rheological properties, moderate thickening time, and high compressive strength, and can meet the construction requirements.

[0011] To achieve the above object, in the first aspect of the present invention, an antifreeze and accelerating agent is provided, wherein the antifreeze and accelerating agent includes: water-soluble inorganic salts, water-soluble organic compounds, surfactants, and optionally water;

[0012] Among them, the water-soluble organic compound includes water-soluble cellulose, and also includes at least one selected from water-soluble alcohol compounds, water-soluble carboxylic acid compounds, and water-soluble amide compounds.

[0013] In the second aspect of the present invention, a well cementing cement slurry system is provided, wherein the well cementing cement slurry system includes cement and the antifreeze and accelerating agent provided by the present invention.

[0014] In the third aspect of the present invention, an application of the antifreeze and accelerating agent provided by the present invention in low-temperature well cementing is provided.

[0015] In the fourth aspect of the present invention, an application of a water-soluble organic compound including water-soluble cellulose and at least one of water-soluble alcohol compounds, water-soluble carboxylic acid compounds, and water-soluble amide compounds in improving the antifreeze temperature of cement slurry and improving the fluidity of cement slurry is provided.

[0016] Through the above technical solutions, the beneficial effects of the present invention at least include:

[0017] The anti-freezing and coagulation-promoting agent provided by the present invention contains water-soluble inorganic salts, which can promote coagulation by salts and lower the freezing point of the liquid phase of the cement slurry; supplemented with water-soluble organic compounds, the anti-freezing and coagulation-promoting effect can be further enhanced, and the fluidity can be improved. Each component in the water-soluble organic compounds has a good synergistic effect; adding surfactants can optimize the ionic composition of the hydration film of cement particles, reduce the salt dosage, and protect the structure of the initial hydration products of cement. The anti-freezing and coagulation-promoting agent provided by the present invention has both anti-freezing and coagulation-promoting effects, solves the problems that the liquid phase of the well cement slurry freezes and the hydration products do not solidify due to freezing damage in a negative temperature environment, improves the early strength of the cement slurry and the stability of the hydration products under low temperature conditions, solves the problem of poor low temperature tolerance of low temperature well cement, meets the requirements of well cementing construction in negative temperature areas, enables the low temperature cement slurry to have good rheology in an environment below 0 °C, can avoid adverse effects such as freezing damage caused by the low temperature environment on the hydration of the cement slurry, has a moderate thickening time, and has a relatively high compressive strength.

[0018] In a preferred embodiment of the present invention, by selecting appropriate component ratios of each component of the anti-freezing and coagulation-promoting agent, the composition and component ratios of the water-soluble inorganic salts, the types of water-soluble organic compounds, and the types of surfactants, each component in the anti-freezing and coagulation-promoting agent can play a better synergistic effect. In addition, the present invention selects the dosage of the anti-freezing and coagulation-promoting agent in the cement slurry system, as well as the types and dosages of each component in the cement slurry system, so that the anti-freezing and coagulation-promoting agent can better play its role in the cement slurry, further improves the anti-freezing and coagulation-promoting effect and compressive strength of the cement slurry, further improves the rheological properties of the cement slurry, and makes the cement slurry have a more suitable thickening time. Under preferred conditions, the anti-freezing temperature of the anti-freezing and coagulation-promoting agent provided by the present invention can reach below -18 °C, the thickening time is 180 - 300 min, and the 24-hour compressive strength can reach above 3.5 MPa. Detailed implementation mode

[0019] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0020] The first aspect of the present invention provides an anti-freezing and coagulation-promoting agent, wherein the anti-freezing and coagulation-promoting agent includes: water-soluble inorganic salts, water-soluble organic compounds, surfactants and optionally water; wherein, the water-soluble organic compounds include water-soluble cellulose, and further include at least one selected from water-soluble alcohol compounds, water-soluble carboxylic acid compounds and water-soluble amide compounds.

[0021] The anti-freezing and coagulation-promoting agent provided by the present invention contains water-soluble inorganic salts, which can promote coagulation by salts and lower the freezing point of the liquid phase of the cement slurry; supplemented with water-soluble organic compounds, the anti-freezing and coagulation-promoting effect can be further enhanced, and the fluidity can be improved; adding surfactants can optimize the ionic composition of the hydration film of cement particles, reduce the salt dosage, and protect the structure of the initial hydration products of cement. The anti-freezing and coagulation-promoting agent provided by the present invention has both anti-freezing and coagulation-promoting effects, providing a way to form early structures at negative temperatures for cement.

[0022] In order to make each component play a better synergistic role and further improve the anti-freezing and coagulation-promoting effect, preferably, in the anti-freezing and coagulation-promoting agent, the weight ratio of the water-soluble inorganic salt, the water-soluble organic compound and the surfactant is 50:(10 - 375):(5 - 25), preferably 1:(1 - 5):(0.1 - 0.5), and more preferably 1:(1 - 5):(0.1 - 0.4).

[0023] Preferably, the weight ratio of the water-soluble inorganic salt and water in the anti-freezing and coagulation-promoting agent is 50:(50 - 1000), preferably 1:(1 - 16), and more preferably 1:(4 - 16).

[0024] In a preferred embodiment of the present invention, in the anti-freezing and coagulation-promoting agent, the weight ratio of the water-soluble inorganic salt, the water-soluble organic compound, the surfactant and water is 50:(10 - 375):(5 - 25):(50 - 1000), preferably 1:(1 - 5):(0.1 - 0.5):(1 - 16).

[0025] In a more preferred embodiment of the present invention, in the anti-freezing and coagulation-promoting agent, the weight ratio of the water-soluble inorganic salt, the water-soluble organic compound, the surfactant and water is 50:(10 - 375):(5 - 25):(50 - 1000), preferably 1:(1 - 5):(0.1 - 0.4):(4 - 16).

[0026] The present invention does not particularly limit the types of water-soluble inorganic salts, and salts conventionally used as coagulation-promoting agents in the art can be used. Preferably, the water-soluble inorganic salt is selected from at least one of water-soluble sodium salts, water-soluble calcium salts and water-soluble magnesium salts.

[0027] In order to further improve the synergistic effect of the water-soluble inorganic salt with the water-soluble organic compound and the surfactant, preferably, the content of the water-soluble sodium salt in the water-soluble inorganic salt is 60 - 100wt%; and / or, the content of the water-soluble calcium salt in the water-soluble inorganic salt is 0 - 40wt%; and / or, the content of the water-soluble magnesium salt in the water-soluble inorganic salt is 0 - 20wt%.

[0028] According to the present invention, preferably, the water-soluble sodium salt is selected from sodium chloride and / or sodium nitrite; and / or, the water-soluble calcium salt is selected from calcium chloride and / or calcium nitrate; and / or, the water-soluble magnesium salt is magnesium chloride.

[0029] According to a preferred embodiment of the present invention, the content of sodium chloride in the water-soluble inorganic salt is 60-100 wt%;

[0030] and / or, the content of sodium nitrite in the water-soluble inorganic salt is 0-20 wt%;

[0031] and / or, the content of calcium chloride in the water-soluble inorganic salt is 0-20 wt%;

[0032] and / or, the content of calcium nitrate in the water-soluble inorganic salt is 0-20 wt%;

[0033] and / or, the content of magnesium chloride in the water-soluble inorganic salt is 0-20 wt%.

[0034] According to a more preferred embodiment of the present invention, the content of sodium chloride in the water-soluble inorganic salt is 60-80 wt%, the content of sodium nitrite is 5-10 wt%, the content of calcium chloride is 5-20 wt%, the content of calcium nitrate is 5-20 wt%, and the content of magnesium chloride is 5-10 wt%.

[0035] According to a particularly preferred embodiment of the present invention, the content of sodium chloride in the water-soluble inorganic salt is 60-65 wt%, the content of sodium nitrite is 5-8 wt%, the content of calcium chloride is 17-20 wt%, the content of calcium nitrate is 5-8 wt%, and the content of magnesium chloride is 8-10 wt%.

[0036] The present invention does not particularly limit the types of water-soluble alcohol compounds, water-soluble carboxylic acid compounds, water-soluble amide compounds, and water-soluble cellulose in the water-soluble organic compound, and water-soluble alcohol compounds, water-soluble carboxylic acid compounds, water-soluble amide compounds, and water-soluble cellulose conventionally used in the art as antifreeze can be used. Preferably, the water-soluble alcohol compound is selected from at least one of methanol, ethanol, isopropanol, ethylene glycol, propylene glycol, and diethylene glycol;

[0037] and / or, the water-soluble carboxylic acid compound is selected from at least one of sodium acetate, sodium benzoate, sodium oxalate, and sodium stearate;

[0038] and / or, the water-soluble amide compound is selected from at least one of formamide, acetamide, urea, and fatty acid amide;

[0039] and / or, the water-soluble cellulose is selected from carboxymethyl cellulose and / or lignosulfonate.

[0040] Preferably, the weight-average molecular weight of the water-soluble cellulose is 10,000 - 200,000 g / mol, and the apparent viscosity of an aqueous solution of the water-soluble cellulose with a concentration of 0.3 wt% is ≤ 25 mPa·s at 25°C.

[0041] According to the present invention, preferably, in the water-soluble organic compound, the weight ratio of at least one of a water-soluble alcohol compound, a water-soluble carboxylic acid compound, and a water-soluble amide compound to the water-soluble cellulose is (20 - 100):1, more preferably (20 - 50):1.

[0042] In order to further improve the synergistic effect of the water-soluble organic compound with the water-soluble inorganic salt and the surfactant, preferably, the water-soluble organic compound includes a water-soluble alcohol compound and a water-soluble cellulose.

[0043] In a preferred embodiment of the present invention, the water-soluble organic compound is a mixture including ethylene glycol and lignosulfonate.

[0044] In a preferred embodiment of the present invention, in the water-soluble organic compound, the weight ratio of ethylene glycol to lignosulfonate is (20 - 100):1, more preferably (20 - 50):1.

[0045] The present invention has no particular limitation on the type of the surfactant, and surfactants that can reduce the surface tension of a liquid and are conventional in the art can be used. Preferably, the surfactant is selected from at least one of an acidic phosphate ester amine salt, an alkylamine, a fatty acid amide, an organic acid ester, and an alkyl succinimide.

[0046] In order to further improve the synergistic effect of the surfactant with other components, the surfactant is more preferably an acidic phosphate ester amine salt.

[0047] In the present invention, an antifreeze and coagulation promoter can be prepared by directly mixing the respective components. In a specific embodiment of the present invention, the water-soluble inorganic salt, the water-soluble organic compound, and the surfactant are weighed according to the required amounts, dissolved in an appropriate amount of water, and stirred evenly to obtain the antifreeze and coagulation promoter.

[0048] The second aspect of the present invention provides a well cement slurry system, wherein the well cement slurry system includes cement and the antifreeze and coagulation promoter provided by the present invention.

[0049] The present invention has no particular limitation on the type of the cement, and conventional cement used for preparing cement slurry can be used. In a preferred embodiment of the present invention, a silicate aluminate composite cement is selected.

[0050] In a preferred embodiment of the present invention, the aluminosilicate composite cement comprises high alumina cement, gypsum and ultra-fine portland cement; wherein, the aluminum content in the high alumina cement is 45-75 wt%; and / or, the D 90 particle size of the ultra-fine portland cement is 5-18 μm; and / or, the weight ratio of the high alumina cement, gypsum and ultra-fine portland cement in the aluminosilicate composite cement is 5:(1-3):(4-6). The inventors found that the anti-freezing and accelerating setting agent provided by the present invention can better play the role of anti-freezing and accelerating setting in the aluminosilicate composite cement satisfying this condition.

[0051] In order to further improve the anti-freezing and accelerating setting effect of the anti-freezing and accelerating setting agent on the cement, preferably, in the well cement slurry system, based on 600 parts by weight of the cement, the content of the anti-freezing and accelerating setting agent is 160-500 parts by weight, more preferably 230-240 parts by weight.

[0052] In order to further improve the early strength performance, preferably, the well cement slurry system further comprises an early strength agent; in the well cement slurry system, based on 600 parts by weight of the cement, the content of the early strength agent is 2-10 parts by weight, more preferably 2-3 parts by weight.

[0053] The present invention does not particularly limit the type of the early strength agent. For example, it can be one or more of alcohol-amine early strength agents, formate early strength agents, calcium salt early strength agents, chloride salt early strength agents, sulfate salt early strength agents, nitrite early strength agents, carbonate early strength agents and calcium silicate hydrate (C-S-H) seeds, and preferably an alcohol-amine early strength agent.

[0054] In a preferred embodiment of the present invention, the alcohol-amine early strength agent is an aqueous solution of triethanolamine with a concentration of 8-12 wt%.

[0055] In order to further optimize the thickening time and rheological properties of the cement slurry, preferably, the well cement slurry system further comprises a retarder; in the well cement slurry system, based on 600 parts by weight of the cement, the content of the retarder is 3-60 parts by weight, more preferably 3-5 parts by weight.

[0056] The present invention does not particularly limit the type of the retarder. For example, it can be one or more of lignosulfonates, phosphates, organic phosphates, borax, gluconates, sugars and tartaric acid, and preferably gluconates.

[0057] In a preferred embodiment of the present invention, the retarder is sodium gluconate.

[0058] To further improve the stability of cement hydration products, preferably, the well cement slurry system further comprises an expansion agent; in the well cement slurry system, based on 600 parts by weight of cement, the content of the expansion agent is 10-30 parts by weight, more preferably 10-15 parts by weight.

[0059] The present invention has no particular limitation on the type of the expansion agent. In a preferred case, a light metal expansion agent is selected, for example, it can be one or more of magnesium oxide, iron oxide, calcium oxide, calcium sulfoaluminate, aluminum powder and iron powder, and preferably magnesium oxide.

[0060] To further optimize the water loss and rheology of the cement slurry, preferably, the well cement slurry system further comprises a fluid loss reducer; in the well cement slurry system, based on 600 parts by weight of cement, the content of the fluid loss reducer is 3-60 parts by weight, more preferably 3-5 parts by weight.

[0061] The present invention has no particular limitation on the type of the fluid loss reducer. In a preferred case, a non-ionic polymer fluid loss reducer and / or an anionic polymer fluid loss reducer are selected; among them, the non-ionic polymer fluid loss reducer can be, for example, modified cellulose such as carboxymethyl cellulose, hydroxyethyl cellulose and carboxymethyl hydroxyethyl cellulose, etc., and the anionic polymer fluid loss reducer can be, for example, an AMPS terpolymer, etc.

[0062] Further, the fluid loss reducer is selected from anionic polymer fluid loss reducers, more preferably an AMPS terpolymer, and further preferably a terpolymer containing structural units from AMPS, structural units from acrylamide monomers and structural units from carboxylate monomers.

[0063] In a preferred embodiment of the present invention, the weight average molecular weight of the AMPS terpolymer is 30,0000-90,0000 g / mol; in the AMPS terpolymer, the weight ratio of the structural units from AMPS, the structural units from acrylamide monomers and the structural units from carboxylate monomers is (2-100):(2.5-50):1, more preferably (10-50):(10-20):1.

[0064] In a specific embodiment of the present invention, when preparing the cement slurry system, other components of the well cement slurry system except the anti-freezing and accelerating agent are weighed and mixed according to the required proportions; the anti-freezing and accelerating agent provided by the present invention is placed in a freezer at -10°C to -25°C for at least 24 h according to the experimental conditions, and then the frozen anti-freezing and accelerating agent is poured into a slurry cup and stirred, and other components of the well cement slurry system that are mixed well are quickly added to the slurry cup, and after stirring evenly, the well cement slurry system is obtained.

[0065] The present invention has no particular limitation on the manner and conditions of stirring before and after adding other components of the well cement slurry system to the slurry cup, as long as the system can be stirred evenly. In a preferred case, a stirrer is used to stir the materials in the slurry cup. After the antifreeze accelerating agent is poured into the slurry cup, it is stirred at a stirring speed of 1500 - 4500 r / min for at least 30 s; after adding other components of the cement slurry system, it is then stirred at a stirring speed of 4500 - 12000 r / min for at least 60 s.

[0066] The third aspect of the present invention provides an application of the antifreeze accelerating agent provided by the present invention in low-temperature well cementing, especially in low-temperature well cementing in an environment below 0°C. In a preferred case, the antifreeze accelerating agent provided by the present invention can be applied to well cementing in an environment of -25°C to 0°C, so that the cement slurry has good rheological properties, a moderate thickening time, and relatively high compressive strength in an environment of -25°C to 0°C.

[0067] The fourth aspect of the present invention provides an application of a water-soluble organic compound including water-soluble cellulose and at least one of water-soluble alcohol compounds, water-soluble carboxylic acid compounds, and water-soluble amide compounds in increasing the antifreeze temperature of the cement slurry and increasing the fluidity of the cement slurry.

[0068] The present invention will be described in detail below through examples and comparative examples. In the following examples and comparative examples, unless otherwise specified, all are conventional methods; the reagents and materials used, unless otherwise specified, can be obtained from commercial channels.

[0069] The following examples are used to illustrate the preparation method of the well cement slurry system, and the parts are all parts by weight.

[0070] Example 1

[0071] S1. A composite water-soluble inorganic salt (60 wt% sodium chloride, 5 wt% sodium nitrite, 20 wt% calcium chloride, 5 wt% calcium nitrate, 10 wt% magnesium chloride), a water-soluble organic compound (the mass ratio of ethylene glycol and sodium lignosulfonate (the apparent viscosity of an aqueous solution of sodium lignosulfonate with a weight-average molecular weight of 100,000 g / mol and a concentration of 0.3 wt% is 20 mPa·s at 25°C) is 20:1), and a surfactant (sodium amine phosphate) are fully dissolved in water to prepare an antifreeze accelerating agent, so that the weight ratio of the composite water-soluble inorganic salt, the water-soluble organic compound, the surfactant, and water is 160:200:20:770, and it is placed in a freezer at -18°C for at least 24 h.

[0072] S2. Pour 239 portions of the above-mentioned pre-frozen anti-freezing and coagulation-promoting agent solution into the slurry cup, start the stirrer and stir at a low speed (2000 r / min), and quickly add 600 portions of aluminosilicate composite cement (high-alumina cement with an aluminum content of 65 wt%, gypsum, and D 90 ultrafine silicate cement with a particle size of 18 μm, and the mass ratio of the three is 5:2:5), 2.5 portions of early strength agent (triethanolamine aqueous solution with a concentration of 10 wt%), 3 portions of retarder (sodium gluconate), 10 portions of light metal expansive agent (magnesium oxide), 3 portions of fluid loss reducer (AMPS terpolymer with a weight average molecular weight of 500,000 g / mol, and the weight ratio of the structural unit from AMPS, the structural unit from acrylamide monomer, and the structural unit from carboxylate monomer is 10:15:1). After stirring at a high speed (10000 r / min) for 1 min, a negative-temperature well cement slurry is obtained.

[0073] Example 2

[0074] S1. Dissolve the composite water-soluble inorganic salt (with the same composition as the composite water-soluble inorganic salt in the example), water-soluble organic compound (the mass ratio of ethylene glycol and sodium lignosulfonate (sodium lignosulfonate aqueous solution with a weight average molecular weight of 100,000 g / mol and a concentration of 0.3 wt% has an apparent viscosity of 20 mPa·s at 25 °C) is 50:1), and surfactant (sodium phosphoester amine) in water to prepare an anti-freezing and coagulation-promoting agent, so that the weight ratio of the composite water-soluble inorganic salt, water-soluble organic compound, surfactant, and water is 50:250:20:770, and place it in a freezer at -18 °C for at least 24 h.

[0075] S2 is the same as S2 in Example 1.

[0076] Example 3

[0077] S1. Dissolve the composite water-soluble inorganic salt (80 wt% sodium chloride, 5 wt% sodium nitrite, 5 wt% calcium chloride, 5 wt% calcium nitrate, 5 wt% magnesium chloride), water-soluble organic compound (the mass ratio of ethylene glycol and sodium lignosulfonate (sodium lignosulfonate aqueous solution with a weight average molecular weight of 100,000 g / mol and a concentration of 0.3 wt% has an apparent viscosity of 20 mPa·s at 25 °C) is 100:1), and surfactant (sodium phosphoester amine) in water to prepare an anti-freezing and coagulation-promoting agent, so that the weight ratio of the composite water-soluble inorganic salt, water-soluble organic compound, surfactant, and water is 160:200:20:1600, and place it in a freezer at -18 °C for at least 24 h.

[0078] S2 is the same as S2 in Example 1.

[0079] Example 4

[0080] S1. Dissolve a composite water-soluble inorganic salt (70 wt% sodium chloride, 5 wt% sodium nitrite, 15 wt% calcium chloride, 5 wt% calcium nitrate, 5 wt% magnesium chloride), a water-soluble organic compound (the mass ratio of ethylene glycol and sodium lignosulfonate (the weight-average molecular weight is 200,000 g / mol, and the apparent viscosity of an aqueous solution of sodium lignosulfonate with a concentration of 0.3 wt% is 20 mPa·s) is 20:1), and a surfactant (sodium amine phosphate) in water to prepare an antifreeze and coagulation promoter, such that the weight ratio of the composite water-soluble inorganic salt, the water-soluble organic compound, the surfactant, and water is 50:50:20:770, and place it in a freezer at -18°C for at least 24 h.

[0081] S2. Pour 239 parts of the above-previously frozen antifreeze and coagulation promoter solution into a slurry cup, start the stirrer and stir at a low speed (2000 r / min), and quickly add 600 parts of aluminosilicate composite cement (high-alumina cement with an aluminum content of 65 wt%, gypsum, and 90 ultrafine silicate cement with a particle size of 18 μm, and the mass ratio of the three is 5:1:5), 5 parts of an early strength agent (10 wt% triethanolamine aqueous solution), 10 parts of a retarder (sodium gluconate), 20 parts of a light metal expansion agent (magnesium oxide), and 20 parts of a fluid loss reducer (AMPS terpolymer with a weight-average molecular weight of 500,000 g / mol, and the weight ratio of the structural unit from AMPS, the structural unit from acrylamide monomer, and the structural unit from carboxylate monomer is 10:15:1). Stir at a high speed (10000 r / min) for 1 min to obtain a negative-temperature well cement slurry.

[0082] Example 5

[0083] Prepare the well cement slurry according to the formula and method of Example 1, except that in S1, replace "such that the weight ratio of the composite water-soluble inorganic salt, the water-soluble organic compound, the surfactant, and water is 160:200:20:770" with "such that the weight ratio of the composite water-soluble inorganic salt, the water-soluble organic compound, the surfactant, and water is 500:200:20:770". Obtain the well cement slurry.

[0084] Example 6

[0085] Prepare the well cement slurry according to the formula and method of Example 1, except that in S1, replace "composite water-soluble inorganic salt (60 wt% sodium chloride, 5 wt% sodium nitrite, 20 wt% calcium chloride, 5 wt% calcium nitrate, 10 wt% magnesium chloride)" with "water-soluble inorganic salt (100 wt% sodium chloride)". Obtain the well cement slurry.

[0086] Example 7

[0087] Prepare the well cement slurry according to the formulation and method of Example 1, except that in S1, replace "such that the weight ratio of the composite water-soluble inorganic salt, water-soluble organic compound, surfactant and water is 160:200:20:770" with "such that the weight ratio of the composite water-soluble inorganic salt, water-soluble organic compound, surfactant and water is 160:200:20:3000". Obtain the well cement slurry.

[0088] Example 8

[0089] Prepare the well cement slurry according to the formulation and method of Example 1, except that the content of each component in the composite water-soluble inorganic salt is different. Specifically, replace "composite water-soluble inorganic salt (60 wt% sodium chloride, 5 wt% sodium nitrite, 20 wt% calcium chloride, 5 wt% calcium nitrate, 10 wt% magnesium chloride)" with "composite water-soluble inorganic salt (20 wt% sodium chloride, 5 wt% sodium nitrite, 20 wt% calcium chloride, 5 wt% calcium nitrate, 50 wt% magnesium chloride)". Obtain the well cement slurry.

[0090] Example 9

[0091] Prepare the well cement slurry according to the formulation and method of Example 1, except that the content of each component in the composite water-soluble inorganic salt is different. Specifically, replace "composite water-soluble inorganic salt (60 wt% sodium chloride, 5 wt% sodium nitrite, 20 wt% calcium chloride, 5 wt% calcium nitrate, 10 wt% magnesium chloride)" with "composite water-soluble inorganic salt (20 wt% sodium chloride, 80 wt% calcium chloride)". Obtain the well cement slurry.

[0092] Example 10

[0093] Prepare the well cement slurry according to the formulation and method of Example 1, except that the weight ratio of the alcohol compound and lignosulfonate in the water-soluble organic compound is different. Specifically, replace "the mass ratio of ethylene glycol and sodium lignosulfonate is 20:1" with "the mass ratio of ethylene glycol and sodium lignosulfonate is 1:1". Obtain the well cement slurry.

[0094] Example 11

[0095] Prepare the well cement slurry according to the formulation and method of Example 1, except that the type of water-soluble alcohol compound in the water-soluble organic compound is different. Specifically, in S1, replace an equal weight of ethylene glycol with methanol. Obtain the well cement slurry.

[0096] Example 12

[0097] Prepare the well cement slurry according to the formulation and method of Example 1, except that the type of surfactant is different. Specifically, replace sodium phosphoester amine of equal weight with alkyl succinimide. Obtain the well cement slurry.

[0098] Example 13

[0099] Prepare the well cement slurry according to the formulation and method of Example 1, except that the type of cement in the well cement slurry is different. Specifically, in S2, replace the aluminosilicate composite cement of equal weight with G-class portland cement. Obtain the well cement slurry.

[0100] Example 14

[0101] Prepare the well cement slurry according to the formulation and method of Example 1, except that in S1, replace "so that the weight ratio of the composite water-soluble inorganic salt, water-soluble organic compound, surfactant and water is 160:200:20:770" with "so that the weight ratio of the composite water-soluble inorganic salt, water-soluble organic compound, surfactant and water is 50:600:20:770". Obtain the well cement slurry.

[0102] Comparative Example 1

[0103] Prepare the well cement slurry according to the formulation and method of Example 1, except that in S1, replace the water-soluble organic compound of equal weight with water. Obtain the well cement slurry.

[0104] Comparative Example 2

[0105] Prepare the well cement slurry according to the formulation and method of Example 1, except that replace ethylene glycol of equal weight with sodium lignosulfonate having a weight-average molecular weight of 100,000 g / mol and an apparent viscosity of 20 mPa·s in a 0.3 wt% aqueous solution at 25°C. Obtain the well cement slurry.

[0106] Comparative Example 3

[0107] Prepare the well cement slurry according to the formulation and method of Example 1, except that replace the composite water-soluble inorganic salt of equal weight with microsilica (200 mesh). Obtain the well cement slurry.

[0108] Comparative Example 4

[0109] Prepare the well cement slurry according to the formulation and method of Example 1, except that the anti-freezing and accelerating agent does not contain water-soluble organic compounds, and the weight ratio of the composite water-soluble inorganic salt, surfactant and water in the anti-freezing and accelerating agent is 160:20:770. Obtain the well cement slurry.

[0110] Test Example

[0111] The anti-freezing temperature, rheological properties, thickening time and compressive strength of the cement slurries prepared according to each example and comparative example were measured respectively.

[0112] Method for measuring anti-freezing temperature: Place the anti-freezing accelerator in a cold source, insert a low-temperature-resistant thermometer that automatically records temperature into the solution, and then lower the solution temperature to -30°C. After 24 hours, read the change of the liquid thermometer temperature over time. If the temperature-time curve remains stable for a period of time, then this temperature is the anti-freezing temperature of this solution.

[0113] The measuring methods for rheological properties, thickening time and compressive strength are carried out in accordance with the API RP10B oil well cement test method, the 22nd edition standard. Immediately after the slurry preparation is completed, pour the cement slurry into the standard thickening instrument cup and cure it in an environment of -18°C. The compressive strength test is carried out when the sample is at -10°C and -18°C.

[0114] The test results are shown in Table 1.

[0115] Table 1

[0116]

[0117]

[0118] It can be seen from the results in Table 1 that the well cement slurries prepared with the anti-freezing accelerator of the present invention in Examples 1-14 have a lower anti-freezing temperature, excellent anti-freezing performance in a negative temperature environment, good rheological properties, a moderate thickening time, and a certain compressive strength at -10°C and -18°C. In Comparative Example 1, water was used to replace an equal weight of water-soluble organic compound, in Comparative Example 2, sodium lignosulfonate was used to replace an equal weight of ethylene glycol, in Comparative Example 3, microsilica was used to replace an equal weight of composite water-soluble inorganic salts, and in Comparative Example 4, no water-soluble organic compound was contained. Compared with Examples 1-14, the anti-freezing temperatures of Comparative Examples 1 and 2 are only -3°C and -4°C. Although Comparative Examples 3 and 4 still have anti-freezing temperatures of -25°C and -20°C, the thickening time is too long or too fast. If the thickening time is too long, the risk of gas channeling at the bottom of the well will increase, and it is difficult to ensure the well cementing quality. If the thickening time is too fast, the construction safety is relatively poor.

[0119] In addition, in Example 5, the dosage of the composite water-soluble inorganic salt was increased. Compared with Example 1, although the compressive strengths at antifreeze temperatures of -25°C, -10°C, and -18°C were also relatively high, the viscosity of the system was too high, the fluidity was poor, and the thickening time was relatively fast (the thickening time is most suitable between 180°C and 300°C), resulting in high difficulty in construction pumping and slightly poor safety; in Example 6, the water-soluble inorganic salt only included sodium chloride, in Example 8, the ratio of each component in the composite water-soluble inorganic salt was changed, and in Example 9, the water-soluble inorganic salt only included sodium chloride and calcium chloride. Compared with Example 1, the compressive strengths at -10°C and -18°C decreased; in Example 7, the proportion of water in the antifreeze accelerating agent increased, and the corresponding proportions of the composite water-soluble inorganic salt and the water-soluble organic compound decreased. Compared with Example 1, the antifreeze temperature of the cement slurry was -10°C, the antifreeze performance decreased, the thickening time was longer, and the compressive strengths at -10°C and -18°C also decreased; in Example 10, the mass ratio of ethylene glycol and sodium lignosulfonate was changed, and in Example 11, methanol was used to replace an equal weight of ethylene glycol. Compared with Example 1, the antifreeze performance of the cement slurry decreased, the thickening time increased, and the compressive strengths at -10°C and -18°C also decreased; in Example 12, the type of surfactant in the antifreeze accelerating agent was changed. Compared with Example 1, the antifreeze performance of the cement slurry decreased, and the compressive strengths at -10°C and -18°C also decreased; in Example 13, the type of cement in the cement slurry was changed. Compared with Example 1, the thickening time increased, and the compressive strengths at -10°C and -18°C also decreased; in Example 14, the content of the water-soluble organic compound in the antifreeze accelerating agent was increased. Compared with Example 2, the thickening time increased, and the compressive strengths at -10°C and -18°C also decreased. This shows that when the ratios of the water-soluble inorganic salt, the water-soluble organic compound, the surfactant, and water in the antifreeze accelerating agent, the composition and ratio of the water-soluble inorganic salt, the composition and ratio of the water-soluble organic compound, and the type of surfactant meet the preferred conditions, the antifreeze performance and rheological properties of the cement slurry in a negative temperature environment can be further improved, the cement slurry has a more suitable thickening time, and the compressive strength of the cement slurry is further increased.

[0120] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. An anti-freezing and coagulation-promoting agent, characterized in that, The anti-freezing and coagulation-promoting agent includes: water-soluble inorganic salts, water-soluble organic compounds, surfactants, and optionally water; Among them, the water-soluble organic compound includes water-soluble cellulose, and also includes at least one selected from water-soluble alcohol compounds, water-soluble carboxylic acid compounds, and water-soluble amide compounds.

2. The anti-freezing and coagulation-promoting agent according to claim 1, wherein In the anti-freezing and coagulation-promoting agent, the weight ratio of the water-soluble inorganic salt, the water-soluble organic compound, and the surfactant is 50:(10 - 375):(5 - 25), preferably 1:(1 - 5):(0.1 - 0.5); Preferably, in the anti-freezing and coagulation-promoting agent, the weight ratio of the water-soluble inorganic salt and water is 50:(50 - 1000), preferably 1:(1 - 16).

3. The anti-freezing and coagulation-promoting agent according to claim 1 or 2, characterized in that, The water-soluble inorganic salt is selected from at least one of water-soluble sodium salts, water-soluble calcium salts, and water-soluble magnesium salts; Preferably, the content of the water-soluble sodium salt in the water-soluble inorganic salt is 60 - 100 wt%; and / or, the content of the water-soluble calcium salt in the water-soluble inorganic salt is 0 - 40 wt%; and / or, the content of the water-soluble magnesium salt in the water-soluble inorganic salt is 0 - 20 wt%; Preferably, the water-soluble sodium salt is selected from sodium chloride and / or sodium nitrite; and / or, the water-soluble calcium salt is selected from calcium chloride and / or calcium nitrate; and / or, the water-soluble magnesium salt is magnesium chloride.

4. The anti-freezing and coagulation-promoting agent according to claim 3, wherein The content of sodium chloride in the water-soluble inorganic salt is 60 - 100 wt%, preferably 60 - 80 wt%; and / or, the content of sodium nitrite in the water-soluble inorganic salt is 0 - 20 wt%, preferably 5 - 10 wt%; and / or, the content of calcium chloride in the water-soluble inorganic salt is 0 - 20 wt%, preferably 5 - 20 wt%; and / or, the content of calcium nitrate in the water-soluble inorganic salt is 0 - 20 wt%, preferably 5 - 20 wt%; and / or, the content of magnesium chloride in the water-soluble inorganic salt is 0 - 20 wt%, preferably 5 - 10 wt%.

5. The anti-freezing and coagulation-promoting agent according to any one of claims 1-4, characterized in that, The water-soluble alcohol compound is selected from at least one of methanol, ethanol, isopropanol, ethylene glycol, propylene glycol, and diethylene glycol; and / or, the water-soluble carboxylic acid compound is selected from at least one of sodium acetate, sodium benzoate, sodium oxalate, and sodium stearate; and / or, the water-soluble amide compound is selected from at least one of formamide, acetamide, urea, and fatty acid amide; and / or, the water-soluble cellulose is selected from carboxymethyl cellulose and / or lignosulfonate; Preferably, the weight-average molecular weight of the water-soluble cellulose is 10,000 - 200,000 g / mol, and the apparent viscosity of an aqueous solution of water-soluble cellulose with a concentration of 0.3 wt% at 25 °C ≤ 25 mPa·s.

6. The anti-freezing and coagulation-promoting agent according to any one of claims 1-5, characterized in that In the water-soluble organic compound, the weight ratio of at least one of the water-soluble alcohol compound, the water-soluble carboxylic acid compound, and the water-soluble amide compound to the water-soluble cellulose is (20 - 100):1; Preferably, the water-soluble organic compound includes a water-soluble alcohol compound and water-soluble cellulose; Preferably, the water-soluble organic compound is a mixture including ethylene glycol and lignosulfonate; Preferably, in the water-soluble organic compound, the weight ratio of ethylene glycol to lignosulfonate is (20-100):

1.

7. The anti-freezing and coagulation-promoting agent according to any one of claims 1-6, characterized in that, The surfactant is selected from at least one of acidic phosphate amine salts, alkylamines, fatty acid amides, organic acid esters, and alkyl succinimides, and preferably an acidic phosphate amine salt.

8. A cementing slurry system, characterized in that, The well cement slurry system includes cement and the antifreeze accelerating agent according to any one of claims 1-7; Preferably, in the well cement slurry system, based on 600 parts by weight of cement, the content of the antifreeze accelerating agent is 160-500 parts by weight; Preferably, the well cement slurry system further includes an early strength agent; in the well cement slurry system, based on 600 parts by weight of cement, the content of the early strength agent is 2-10 parts by weight; Preferably, the well cement slurry system further includes a retarder; in the well cement slurry system, based on 600 parts by weight of cement, the content of the retarder is 3-60 parts by weight; Preferably, the well cement slurry system further includes an expansion agent; in the well cement slurry system, based on 600 parts by weight of cement, the content of the expansion agent is 10-30 parts by weight; Preferably, the well cement slurry system further includes a fluid loss reducer; in the well cement slurry system, based on 600 parts by weight of cement, the content of the fluid loss reducer is 3-60 parts by weight.

9. Application of the antifreeze accelerating agent according to any one of claims 1-8 in well cementing in a low-temperature environment, preferably in well cementing in an environment below 0°C, more preferably in well cementing in an environment of -25°C to 0°C.

10. Application of a water-soluble organic compound including water-soluble cellulose and at least one of water-soluble alcohol compounds, water-soluble carboxylic acid compounds, and water-soluble amide compounds in increasing the antifreeze temperature of cement slurry and increasing the fluidity of cement slurry.

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