Ultrahigh-temperature seawater cement slurry system and preparation method thereof

Abstract

The invention belongs to the technical field of oilfield chemistry, and relates to an ultrahigh-temperature well cementation cement slurry technology, in particular to an ultrahigh-temperature seawater cement slurry system and a preparation method thereof. The invention provides an ultrahigh-temperature seawater cement slurry system. The ultrahigh-temperature seawater cement slurry system comprises cement, a high-temperature anti-declining agent, a fluid loss agent, a retarder, a suspension stabilizer, a defoaming agent and seawater. The ultrahigh-temperature seawater cement paste system can be applied to seawater at the temperature of 230 DEG C and has excellent ultrahigh-temperature resistance, the cement paste fluidity is good, API water loss is low, the thickening time is adjustable, the compressive strength meets the well cementation construction requirement, no free liquid is generated, and the well cementation construction requirement is completely met.

Description

Technical Field

[0001] The invention belongs to the technical field of oilfield chemistry, relates to ultra-high temperature cementing slurry technology, and in particular to an ultra-high temperature seawater cement slurry system and a preparation method thereof. Background Art

[0002] my country is a large maritime country with abundant marine oil and gas resources. However, the overall development level of my country's abundant marine oil and gas resources is relatively low. As the recoverable and easily recoverable amount of onshore oil gradually decreases, the development of offshore exploration and development as well as deep and ultra-deep well cementing technology is a major trend in future technological development. Marine oil and gas resources are also widely distributed in the world, accounting for about half of the total reserves in the four oceans and the Persian Gulf, and the circulation temperature of some seawater wells can reach an ultra-high temperature of 210°C.

[0003] At present, most cement slurry systems used in offshore cementing operations are prepared with fresh water, which requires fresh water to be transported from land or seawater to be desalinated, which has a certain impact on cost and efficiency. Using seawater to prepare cement slurry can improve the capacity of offshore cementing operations. Seawater slurry can be prepared with local materials and is not restricted by transportation or seawater desalination equipment. Offshore operations are also conducive to reducing costs and increasing efficiency.

[0004] At present, most researchers focus on freshwater cement slurry systems, and pay less attention to seawater cement slurry systems. The cementing additives and cement slurry systems currently used in the market will have the following problems when used in seawater: First, some metal ions such as Ca contained in seawater 2+ Mg 2+ , will bridge and form bridges with the polymer fluid loss agent molecular chains adsorbed on cement particles, resulting in poor cement slurry fluidity and even thixotropy; second, polymer molecular chains are prone to curling in the seawater ion environment, affecting their adsorption on cement particles, resulting in increased high-temperature and ultra-high-temperature water loss. Third, compared with fresh water, the complex ions in seawater will cause cement slurry to have abnormal gelation phenomena such as core encapsulation and thickening. The retarder addition sensitivity and temperature sensitivity are poor, which is a challenge to cementing construction safety.

[0005] The Chinese invention patent with application number 201410492102.X discloses a new high-temperature low-density cement slurry system. The components and weight proportions of the new low-density cement slurry system are: 100 parts of oil well cement, 50-80 parts of fly ash, 30-40 parts of silica sand, 24-76 parts of active enhancer I, 13-60 parts of active enhancer II, 8.0-17 parts of high-temperature fluid loss reducer, 0.2-0.8 parts of high-temperature retarder, 0.0-0.5 parts of dispersant, and 140-200 parts of water. The density of the cement slurry is 1.40-1.60 g / cm 3Adjustable, used for cementing operations in the range of 70 to 150°C. However, for the ultra-high temperature environment of seawater well circulation temperature of 210°C, this cement slurry system cannot meet the operation requirements.

[0006] The Chinese invention patent with application number 201710312962.4 discloses a dispersed solid fluid loss agent for seawater cement slurry and a preparation method. The prepared dispersed fluid loss agent is used in seawater cement slurry and has good fluidity and good water loss control ability, but the water loss test is only carried out at 60°C. However, the water loss control ability of the fluid loss agent under high and ultra-high temperatures of seawater and the comprehensive performance of the cement slurry system are not investigated, the post-treatment of the reaction product requires freeze-drying operation, and the synthesis process is relatively complicated.

[0007] The Chinese invention patent with application number 201710566260.9 discloses a slow-release fluid loss agent for seawater cementing, a preparation method and an application. The prepared fluid loss agent can improve the filtration control effect and has the ability to disperse cement slurry for a long time. However, the invention does not evaluate the performance of the fluid loss agent at high temperature and ultra-high temperature, and lacks an investigation on the comprehensive performance of cement slurry at ultra-high temperature.

[0008] The Chinese invention patent with application number 201910423555.X discloses a cementing slurry system and its application. It includes: cement, high temperature stabilizer, brittleness reducer and high temperature resistant expansion agent with fluid loss reducer, dispersant, retarder and defoamer. After the cementing slurry prepared by the cement slurry system of the invention solidifies and hardens, it not only reduces the elastic modulus of the cement stone, improves the brittleness of the cement stone, improves its deformation capacity after being stressed, improves the impact toughness of the cement stone, maintains high strength, but also compensates for various shrinkages of the cement stone, enhances the cement ring interface bonding ability, and meets the cementing needs of high-pressure gas wells. However, the invention is mainly used in fresh water, and the maximum temperature of the cement slurry system is 140°C. For the ultra-high temperature environment of the seawater well circulation temperature of 210°C, the cement slurry system cannot meet the operation requirements.

[0009] The Chinese invention patent with application number 202110550154.8 discloses a low-density cementing slurry system suitable for medium and high temperature formations and its preparation method, which contains 50% to 55% oil well cement, 30% to 35% fly ash, 7% to 15% microsilica powder, 0.5% to 2% slurry stabilizer, 0.1% to 2% nano-liquid silicon emulsion, 0.2% to 1% early strength agent, 0.5% to 2.5% fluid loss reducer, 0.2% to 0.8% drag reducer, and 0.1% to 2% retarder. Its cement slurry system can be applied to medium and high temperature low-pressure formations in the fresh water range of 80℃-150℃.

[0010] Although the cement slurry systems disclosed in Chinese invention patents with application numbers 202110452959.9, 202010012164.1 and 202211023830.7 can be used at 210°C, they can only be used in fresh water.

[0011] Therefore, researching and developing a seawater cement slurry system that can be used at ultra-high temperatures is still a difficulty in this field. Summary of the invention

[0012] In order to solve the above shortcomings and deficiencies, the present invention provides an ultra-high temperature seawater cement slurry system and a preparation method thereof.

[0013] Specifically, the present invention provides an ultra-high temperature seawater cement slurry system, comprising: cement, a high temperature anti-fading agent, a fluid loss reducer, a retarder, a suspension stabilizer, a defoaming agent, and seawater.

[0014] The above-mentioned ultra-high temperature seawater cement slurry system, by weight, comprises 100 parts of cement, 30-60 parts of high temperature anti-fading agent, 6-13 parts of fluid loss reducer, 2.5-5 parts of retarder, 1-2 parts of suspension stabilizer, 0.25-1.5 parts of defoamer and 40-67 parts of seawater.

[0015] The above-mentioned ultra-high temperature seawater cement slurry system, by weight, comprises 100 parts of cement, 35-50 parts of high temperature anti-fading agent, 8-12 parts of fluid loss reducer, 2.5-4 parts of retarder, 1.5-2 parts of suspension stabilizer, 0.3-1 part of defoamer and 42-65 parts of seawater.

[0016] In the above-mentioned ultra-high temperature seawater cement slurry system, the cement is Class G oil well cement.

[0017] In the above-mentioned ultra-high temperature seawater cement slurry system, the high temperature anti-fading agent is silicon powder with a mass percentage of silicon dioxide greater than 97%.

[0018] In the above-mentioned ultra-high temperature seawater cement slurry system, the particle size of the silicon powder is 100 mesh, 300 mesh and / or 800 mesh.

[0019] In the above-mentioned ultra-high temperature seawater cement slurry system, the fluid loss reducer is a five-membered copolymer of 2-acrylamide-2-methylpropane sulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate and a long side chain functional monomer.

[0020] In the above-mentioned ultra-high temperature seawater cement slurry system, the weight ratio of the 2-acrylamide-2-methylpropane sulfonic acid, the N,N-dimethylacrylamide, the fumaric acid, the sodium styrene sulfonate and the long side chain functional monomer is (60-70):(10-20):(6-10):(2-4):(4-8).

[0021] In the above-mentioned ultra-high temperature seawater cement slurry system, the long side chain functional monomer includes one or more of hexadecyl dimethyl benzyl ammonium chloride, behenyl polyoxyethylene methacrylate, carboxymethyl octadecyl methyl diallyl ammonium chloride, and octadecyl polyoxyethylene ether methacrylate.

[0022] In the above-mentioned ultra-high temperature seawater cement slurry system, the retarder is a 2-acrylamide-2-methylpropane sulfonic acid polymer retarder or a mixture of a 2-acrylamide-2-methylpropane sulfonic acid polymer retarder and an organic phosphonate retarder.

[0023] In the above-mentioned ultra-high temperature seawater cement slurry system, the retarder is a mixture of a 2-acrylamide-2-methylpropane sulfonic acid polymer retarder, an organic phosphonate retarder, and a hydroxycarboxylate retarder in a mass ratio of (2-3):(0.5-1):(0.5-2).

[0024] In the above-mentioned ultra-high temperature seawater cement slurry system, the suspension stabilizer is an inorganic-organic hybrid material compounded with vinyl acetate polymer, Wenlun gum and sepiolite in a mass ratio of 5:(1-2):(3-4).

[0025] In the above-mentioned ultra-high temperature seawater cement slurry system, the defoaming agent is an ester defoaming agent, an organosilicon defoaming agent or a silicone ether oil defoaming agent.

[0026] On the other hand, the present invention also provides a method for preparing the above-mentioned ultra-high temperature seawater cement slurry system, comprising:

[0027] (1) mixing cement and high temperature anti-fading agent according to a proportion to obtain a solid mixture;

[0028] (2) mixing seawater, a fluid loss reducer, a retarder, a suspension stabilizer, and a defoamer according to a proportion to obtain slurry preparation water;

[0029] (3) The slurry preparation water is placed on a stirrer with a rotation speed of 4000±200 rpm, the solid mixture is added to the slurry preparation water within 15 seconds, and the mixture is stirred for 30-50 seconds at a rotation speed of 12000±500 rpm to obtain an ultra-high temperature seawater cement slurry system.

[0030] In the above-mentioned preparation method of the ultra-high temperature seawater cement slurry system, the fluid loss reducer is prepared by the following method:

[0031] a. The weight ratio of (60-70): (10-20): (6-10): (2-4): (4-8) of 2-acrylamide-2-methylpropanesulfonic acid, N, N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate and long side chain monomers were dissolved in water to obtain a mixed solution;

[0032] b. Use alkali to adjust the pH of the mixed solution to 6-7 and heat it to 60-65°C;

[0033] c. After nitrogen is introduced for 20-30 minutes, the initiator is used to initiate the reaction. After 4-6 hours of reaction, the fluid loss reducer is obtained.

[0034] In the above-mentioned method for preparing the ultra-high temperature seawater cement slurry system, the long side chain monomer includes: one or more of hexadecyl dimethyl benzyl ammonium chloride, docosyl polyoxyethylene methacrylate, carboxymethyl octadecyl methyl diallyl ammonium chloride, and octadecyl polyoxyethylene ether methacrylate.

[0035] In the above-mentioned method for preparing the ultra-high temperature seawater cement slurry system, the initiator is one or more of sodium persulfate, ammonium persulfate, and azobisisobutyramidine hydrochloride.

[0036] In the above-mentioned method for preparing the ultra-high temperature seawater cement slurry system, the amount of the initiator added is 0.1-0.3 parts.

[0037] The technical solution of the present invention has the following beneficial effects:

[0038] (1) The ultra-high temperature seawater cement slurry system of the present invention can be used in 230°C seawater, has excellent ultra-high temperature resistance, good slurry fluidity, low API water loss, adjustable thickening time, compressive strength that meets cementing construction requirements, and no free liquid is generated, which fully meets cementing construction requirements;

[0039] (2) The ultra-high temperature seawater cement slurry system of the present invention has wide applicability and can be used to construct low-density, conventional-density, and high-density basic cement slurry systems. It has good compatibility with materials such as latex and resin and can construct functional cement slurry systems.

[0040] (3) The ultra-high temperature seawater cement slurry system of the present invention can meet the cementing technical requirements of special wells such as high temperature seawater wells, ultra-high temperature seawater wells, deep wells, and ultra-deep wells. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the following detailed description of the preferred embodiment.The drawings are only for the purpose of illustrating the preferred embodiments and are not to be construed as limiting the invention.

[0042] Figure 1This is the thickening time curve of the cement slurry system at 180°C of Example 1 of the present invention;

[0043] Figure 2 This is the thickening time curve of the cement slurry system at 210°C of Example 2 of the present invention;

[0044] Figure 3 This is the thickening time curve of the cement slurry system at 230°C of Example 3 of the present invention;

[0045] Figure 4 This is the thickening time curve of the cement slurry system at 210°C of Example 4 of the present invention;

[0046] Figure 5 This is the thickening time curve of the cement slurry system at 220°C of Example 5 of the present invention;

[0047] Figure 6 This is the thickening time curve of the cement slurry system at 200°C of Example 6 of the present invention;

[0048] Figure 7 This is the thickening time curve of the cement slurry system at 200°C of Example 7 of the present invention. DETAILED DESCRIPTION

[0049] In order to fully understand the purpose, features and effects of the present invention, the present invention is described in detail through the following specific embodiments. Except for the following contents, the process method of the present invention adopts conventional methods or devices in the art. Unless otherwise specified, the following terms have the meanings commonly understood by those skilled in the art.

[0050] The words "preferred", "more preferred" and the like in the present invention refer to embodiments of the present invention that can provide certain beneficial effects in certain circumstances. However, other embodiments may also be preferred under the same circumstances or other circumstances. In addition, the description of one or more embodiments does not imply that other embodiments are not applicable, nor is it intended to exclude other embodiments from the scope of the present invention.

[0051] When a numerical range is disclosed herein, the above range is considered to be continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0052] An ultra-high temperature seawater cement slurry system comprises cement, a high temperature anti-fading agent, a fluid loss reducer, a retarder, a suspension stabilizer, a defoamer and seawater.

[0053] In the ultra-high temperature seawater cement slurry system of the present invention, the various components with specific contents act synergistically to meet the cementing technical requirements of special wells such as high temperature seawater wells, ultra-high temperature seawater wells, deep wells, and ultra-deep wells.

[0054] The components of the ultra-high temperature seawater cement slurry system of the present invention are introduced in detail below.

[0055] cement

[0056] Cement is a powdery hydraulic inorganic gelling material, which becomes a slurry when mixed with water. It can harden in the air or in water, and can firmly bond sand, stone and other materials together.

[0057] Preferably, the cement used in the present invention is Grade G oil well cement that meets API specifications.

[0058] G-grade oil well cement has suitable density and setting time, and low viscosity. The cement slurry prepared with it as the base material has good settlement stability and flow performance. During cementing construction, it can quickly solidify and harden and produce a certain compressive strength. After solidification, the cement stone has good impermeability, stability and corrosion resistance, which can meet the requirements of subsequent oil and gas well construction.

[0059] High temperature anti-fading agent

[0060] The compressive strength of G-grade oil well cement will decay rapidly with the extension of curing age at temperatures above 110°C, which will affect the quality of cement ring sealing under high temperature for a long time. Adding high temperature anti-decay agent can make cement stone serve in the high temperature and high pressure environment underground, which can ensure the mechanical strength and bonding performance of cement stone.

[0061] Wherein, the high temperature anti-fading agent is silicon powder with a mass percentage of silicon dioxide greater than 97%.

[0062] Preferably, the particle size of the silicon powder is 100 mesh, 300 mesh and / or 800 mesh.

[0063] Wherein, based on 100 parts by weight of cement, the content of the high temperature anti-decay agent in the cement slurry system of the present invention is 30-60 parts. In the cement slurry system, when the content of the high temperature anti-decay agent is too little, the strength of the cement stone will decline after long-term service, the mechanical properties will decrease, and the permeability will increase; when the content of the high temperature anti-decay agent is too much, it will be difficult to mix the cement slurry, the fluidity of the cement slurry will deteriorate, and it will be unfavorable for pumping.

[0064] Preferably, based on 100 parts by weight of cement, the content of the high temperature anti-fading agent in the cement slurry system of the present invention is 35-50 parts.

[0065] Fluid Loss Additive

[0066] Fluid loss reducer is a type of additive that can control and reduce the loss of cement slurry filtrate into the formation.

[0067] During cementing construction, "percolation" will occur when the cement slurry passes through high permeability formations under pressure. If the cement slurry loses too much water, the cement slurry density, thickening time, and flow properties will change, affecting the safety of the cementing construction; the strong alkaline filtrate of the cement slurry entering the reservoir will also cause a certain degree of damage.

[0068] The fluid loss reducing agent used in the invention is a five-element copolymer of 2-acrylamide-2-methylpropane sulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate and a long side chain functional monomer.

[0069] The long side chain functional monomers include one or more of hexadecyl dimethyl benzyl ammonium chloride, behenyl polyoxyethylene methacrylate, carboxymethyl octadecyl methyl diallyl ammonium chloride, and octadecyl polyoxyethylene ether methacrylate.

[0070] Wherein, the weight average molecular weight of the five-membered copolymer is 800,000-1.2 million.

[0071] Wherein, the preparation method of the fluid loss additive of the present invention comprises the following steps:

[0072] a. The weight ratio of (60-70): (10-20): (6-10): (2-4): (4-8) of 2-acrylamide-2-methylpropanesulfonic acid, N, N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate and long side chain monomers were dissolved in water to obtain a mixed solution;

[0073] b. Use alkali to adjust the pH of the mixed solution to 6-7 and heat it to 60-65°C;

[0074] c. After nitrogen is introduced for 20-30 minutes, the initiator is used to initiate the reaction. After 4-6 hours of reaction, the fluid loss reducer is obtained.

[0075] Wherein, the initiator is one or more of sodium persulfate, ammonium persulfate, and azobisisobutylamidine hydrochloride; and the added amount of the initiator is 0.1 part to 0.3 part.

[0076] In the fluid loss reducer prepared by the method of the present invention, the functional group contains a long side group monomer, which will not form a bridge to produce a network structure in the high-valent metal ion environment of seawater, and will not produce a polyelectrolyte effect to cause the molecular chain to curl up. In this way, the fluid loss reducer can be better adsorbed on the surface of cement particles, block cement pores, and play a good water loss control effect, while maintaining the excellent fluidity of cement slurry without thixotropy and thickening.

[0077] Wherein, based on 100 parts by weight of cement, the content of the fluid loss agent in the cement slurry system of the present invention is 6-13 parts. In the cement slurry system, when the content of the fluid loss agent is too little, the water loss of the cement slurry is uncontrollable, and the properties of the cement slurry such as density, rheology, and thickening time will change; when the content of the fluid loss agent is too much, the cement slurry is thicker and has poor fluidity, which affects pumping.

[0078] Preferably, based on 100 parts by weight of cement, the content of the fluid loss reducer in the cement slurry system of the present invention is 8-12 parts.

[0079] Retarder

[0080] Retarder is an admixture used to prolong the hydration and hardening time of cement, so that the cement slurry can maintain good fluidity during the process of being pumped to the designated location, allowing the cementing construction to proceed safely and smoothly.

[0081] The retarder used in the present invention is a 2-acrylamide-2-methylpropane sulfonic acid polymer retarder or a mixture of a 2-acrylamide-2-methylpropane sulfonic acid polymer retarder and an organic phosphonate retarder or a 2-acrylamide-2-methylpropane sulfonic acid polymer retarder and an organic phosphonate retarder and a hydroxycarboxylate retarder.

[0082] Preferably, the retarder is a mixture of a 2-acrylamide-2-methylpropanesulfonic acid polymer retarder, an organic phosphonate retarder, and a hydroxycarboxylate retarder in a mass ratio of (2-3):(0.5-1):(0.5-2).

[0083] Among them, the retarder is compounded by AMPS polymer, organic phosphate and hydroxycarboxylate. Compared with pure polymer retarder, organic phosphate and hydroxycarboxylate have stronger adsorption and chelation effect on cement particles, which can reduce the cross-linking of carboxyl groups with ions in seawater, effectively solve the abnormal gelation phenomena such as core encapsulation and bulging of cement slurry in seawater, and can also effectively reduce the temperature sensitivity and dosage sensitivity of cement slurry thickening time under high temperature, and can also achieve good compatibility with other materials.

[0084] Among them, the 2-acrylamide-2-methylpropane sulfonic acid polymer is a copolymer of 2-acrylamide-2-methylpropane sulfonic acid (AMPS) and acrylic acid (AA), with a molecular weight between 100,000 and 200,000; the hydroxycarboxylate is one or more of sodium tartrate, sodium citrate, and sodium gluconate; the organic phosphonate is one or more of pentasodium ethylenediaminetetramethylenephosphonate, pentasodium diethylenetriaminepenta(methylenephosphonate), tetrasodium aminotri(methylenephosphonate), and sodium hydroxyethylidene diphosphate.

[0085] Optionally, the retarder is purchased from Blue Ocean Boda Technology Co., Ltd., and the product model is: C-R52L.

[0086] The content of the retarder in the cement slurry system of the present invention is 2.5-5 parts based on 100 parts by weight of cement. In the cement slurry system, when the content of the retarder is too little, the cement slurry will coagulate too quickly, which will bring potential safety hazards to the cementing site construction; when the content of the retarder is too much, the cement slurry will have side effects such as super slow coagulation, long thickening time, and slow strength of cement stone.

[0087] Preferably, based on 100 parts by weight of cement, the content of the retarder in the cement slurry system of the present invention is 2.5-4 parts.

[0088] Suspension stabilizer

[0089] Under high temperature and ultra-high temperature conditions, cement slurry will become thinner, and the ability to suspend solid particles will weaken, and solid particles will tend to aggregate and settle in large quantities. Therefore, under high temperature conditions, suspension stabilizers need to be added to ensure that the cement slurry has good settling stability.

[0090] Among them, the high-temperature suspension stabilizer used in the present invention is an inorganic-organic hybrid material compounded with vinyl acetate polymer, Wenlun glue and sepiolite, which has the advantages of little effect on the rheology of cement slurry at low temperature and good high-temperature suspension stability, and completely solves the problems of slow ash discharging, high viscosity, severe high-temperature\ultra-high-temperature dilution and poor stability during mixing of high-temperature cement slurry.

[0091] Preferably, the mass ratio of vinyl acetate polymer, vinyl gum and sepiolite can be 5:(1-2):(3-4).

[0092] Optionally, the high temperature suspension stabilizer used in the present invention is purchased from Blue Ocean Boda Technology Co., Ltd., and the product batch number is: C-SA56L.

[0093] Wherein, the content of the suspension stabilizer in the cement slurry system of the present invention is 1-2 parts based on 100 parts by weight of cement. In the cement slurry system, when the content of the suspension stabilizer is too little, the cement slurry has poor suspension ability at high temperature, sedimentation will occur, and the slurry is not homogeneous; when the content of the suspension stabilizer is too much, the fluidity of the cement slurry may be deteriorated.

[0094] Preferably, based on 100 parts by weight of cement, the content of the suspension stabilizer in the cement slurry system of the present invention is 1.5-2 parts.

[0095] Defoaming agent

[0096] Defoaming agent, also known as defoaming agent, is used to eliminate harmful foam generated during the preparation of cement slurry system or to inhibit the generation of foam.

[0097] The defoaming agent used in the present invention is an ester defoaming agent or an organosilicon defoaming agent.

[0098] Among them, ester defoamers include Span 80, tributyl phosphate, etc.; silicone defoamers include polydimethylsiloxane, fluorosilicone, and ethylene glycol siloxane.

[0099] The content of the defoamer in the cement slurry system of the present invention is 0.25-1.5 parts based on 100 parts by weight of cement. In the cement slurry system, when the content of the defoamer is too little, a large number of bubbles are generated, the cement slurry density measurement is inaccurate, and in severe cases, the slurry cannot be mixed during on-site construction, resulting in cementing accidents; when the content of the defoamer is too much, a large amount of oily substances will be mixed into the cement slurry, affecting the cement stone bonding.

[0100] Preferably, based on 100 parts by weight of cement, the content of the defoamer in the cement slurry system of the present invention is 0.3-1 part.

[0101] Preferably, in the ultra-high temperature seawater cement slurry system of the present invention, the amount of seawater added is calculated based on the cement slurry density. When different cement slurry densities are designed, the amount of seawater used is also different accordingly.

[0102] Preferably, based on 100 parts by weight of cement, the content of seawater in the cement slurry system of the present invention is 40-67 parts, more preferably 42-65 parts.

[0103] The ultra-high temperature seawater cement slurry system of the present invention may further include a reinforcing agent, which is one or more of high-strength micro-silicon, nano-silicon, and liquid silicon.

[0104] The content of the reinforcing agent in the cement slurry system of the present invention is 4-10 parts per 100 parts by weight of cement. In the cement slurry system, when the content of the reinforcing agent is too little, the strength of the cement paste is low and does not meet the requirements of cementing construction; when the content of the reinforcing agent is too much, the ultrafine material makes it difficult to mix the cement slurry.

[0105] Preferably, based on 100 parts by weight of cement, the content of the reinforcing agent in the cement slurry system of the present invention is 5-8 parts.

[0106] The ultra-high temperature seawater cement slurry system of the present invention may further include a weighting agent, which is one or more of iron ore powder, manganese ore powder, barite, and pure iron powder.

[0107] The content of the weighting agent in the cement slurry system of the present invention is 60-200 parts per 100 parts by weight of cement. In the cement slurry system, when the content of the weighting agent is too little, the water requirement is too little, the cement slurry is difficult to mix, and the slurry fluidity is poor; when the content of the weighting agent is too much, the relative content of the cement gelling component is low, which affects the strength development of the cement paste.

[0108] Preferably, based on 100 parts by weight of cement, the content of the weighting agent in the cement slurry system of the present invention is 80-150 parts.

[0109] The ultra-high temperature seawater cement slurry system of the present invention may further include a resin, which is a styrene-butadiene resin emulsion or a styrene-acrylic resin emulsion.

[0110] The content of resin in the cement slurry system of the present invention is 3-11 parts based on 100 parts by weight of cement. In the cement slurry system, when the content of resin is too little, the anti-gas channeling performance of the cement slurry and the cement-paste bonding performance are not good; when the content of resin is too much, the mixing ability and fluidity of the cement slurry are affected.

[0111] Preferably, based on 100 parts by weight of cement, the content of resin in the cement slurry system of the present invention is 4-7 parts.

[0112] The ultra-high temperature seawater cement slurry system of the present invention may also include latex.

[0113] The content of latex in the cement slurry system of the present invention is 5-12 parts per 100 parts by weight of cement. In the cement slurry system, when the content of latex is too little, the toughness of the cement paste, the sedimentation stability of the cement slurry, and the anti-gas channeling performance are poor; when the content of latex is too much, the latex demulsifies, the slurry is unstable, and the strength development of the cement paste is slow.

[0114] Preferably, based on 100 parts by weight of cement, the content of latex in the cement slurry system of the present invention is 6-11 parts.

[0115] The ultra-high temperature seawater cement slurry system of the present invention may further include a lightening agent, which is one or more of fly ash, diatomaceous earth, water glass, and glass microspheres.

[0116] The content of the lightening agent in the cement slurry system of the present invention is 5-12 parts based on 100 parts by weight of cement. In the cement slurry system, when the content of the lightening agent is too little, it is difficult to adjust the density of the cement slurry, and a large amount of water needs to be added to reduce the density of the cement slurry, which affects the strength development of the cement paste; when the content of the lightening agent is too much, the solid content is too high, and it is difficult to mix the slurry.

[0117] Preferably, based on 100 parts by weight of cement, the content of the lightening agent in the cement slurry system of the present invention is 7-10 parts.

[0118] On the other hand, the present invention also provides a method for preparing an ultra-high temperature seawater cement slurry system, comprising:

[0119] (1) mixing cement and high temperature anti-fading agent according to a proportion to obtain a solid mixture;

[0120] (2) mixing seawater, a fluid loss reducer, a retarder, a suspension stabilizer, and a defoamer according to a proportion to obtain slurry preparation water;

[0121] (3) Place the slurry water on the agitator, rotate the agitator at a low speed (4000±200 rpm), add the solid mixture into the slurry water within 15 seconds, cover the agitator, and continue stirring at a high speed (12000±500 rpm) for 30-50 seconds to mix evenly, thereby obtaining an ultra-high temperature seawater cement slurry system.

[0122] The preparation method of the ultra-high temperature seawater cement slurry system of the present invention is simple, and the obtained cement slurry system has excellent ultra-high temperature resistance, good fluidity, low API water loss, adjustable thickening time, compressive strength that meets cementing construction requirements, and no free liquid is generated, thus meeting cementing construction requirements.

[0123] Example

[0124] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. Among them, Examples 1-7 are prepared according to the preparation method of the ultra-high temperature seawater cement slurry system of the present invention, and the formula of the ultra-high temperature seawater cement slurry system in each example is as follows.

[0125] Example 1

[0126] Experimental temperature: 180℃, cement slurry density: 1.9g / cm 3 .

[0127] Cement slurry formula: 600g oil well cement + 210g high temperature anti-decay agent + 48g fluid loss reducer + 18g retarder + 9g suspension stabilizer + 1.8g defoamer + 285g sea water.

[0128] Wherein, the high temperature anti-fading agent is silicon powder, the mass percentage of silicon dioxide in the silicon powder is greater than 97%, and the particle size is 300 meshes.

[0129] The fluid loss additive is a five-element copolymer of 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate and a long side chain functional monomer, and the specific preparation method is as follows:

[0130] a. Weigh 64 g of 2-acrylamide-2-methylpropanesulfonic acid, 14 g of N,N-dimethylacrylamide, 6 g of fumaric acid, 2 g of sodium styrene sulfonate and 5 g of carboxymethyl octadecylmethyldiallylammonium chloride in portions by weight for later use;

[0131] b. Dissolve 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate and carboxymethyl octadecylmethyldiallylammonium chloride in water with stirring to obtain a mixed solution;

[0132] c. Adjust the pH value of the mixed solution to 6.2 with sodium hydroxide; heat to 63.7°C, introduce nitrogen for 20 minutes, initiate with sodium persulfate, and react for 6 hours to obtain a fluid loss reducer.

[0133] The retarder is C-R52L purchased from Blue Ocean Boda Technology Co., Ltd.

[0134] The defoamer is an ester defoamer C-DF60L purchased from Blue Ocean Boda Technology Co., Ltd.

[0135] The suspension stabilizer is C-SA56L purchased from Blue Ocean Boda Technology Co., Ltd.

[0136] Example 2

[0137] Experimental temperature: 210℃, cement slurry density: 1.9g / cm 3 .

[0138] Cement slurry formula: 600g G-grade Shandong cement + 210g high-temperature anti-fade agent + 48g fluid loss reducer + 21g retarder C-R52L + 9g suspension stabilizer C-SA56L + 1.8g defoamer + 283g sea water.

[0139] Wherein, the high-temperature anti-fading agent is silicon powder, the mass percentage of silicon dioxide in the silicon powder is greater than 97%, and the particle size of the silicon powder is 800 meshes.

[0140] The fluid loss reducer is a five-element copolymer of 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate and behenyl polyoxyethylene methacrylate, and the specific preparation method is as follows:

[0141] a. Weigh 60 g of 2-acrylamide-2-methylpropanesulfonic acid, 18 g of N,N-dimethylacrylamide, 8 g of fumaric acid, 3 g of sodium styrene sulfonate and 4 g of behenyl polyoxyethylene methacrylate, and set aside;

[0142] b. Dissolve 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate and behenyl polyoxyethylene methacrylate in water with stirring to obtain a mixed solution;

[0143] c. Use sodium hydroxide to adjust the pH of the mixed solution to 6.2; heat to 61.5°C, introduce nitrogen for 20 minutes, initiate with ammonium persulfate, and react for 6 hours to obtain a fluid loss reducer.

[0144] The retarder is C-R52L purchased from Blue Ocean Boda Technology Co., Ltd.

[0145] The defoamer is an ester defoamer C-DF60L purchased from Blue Ocean Boda Technology Co., Ltd.

[0146] The suspension stabilizer is C-SA56L purchased from Blue Ocean Boda Technology Co., Ltd.

[0147] Example 3

[0148] Experimental temperature: 230℃, cement slurry density: 1.9g / cm 3 .

[0149] Cement slurry formula: 600g G-grade Shandong cement + 300g high temperature anti-decay agent + 54g fluid loss reducer + 24g retarder C-R52L + 12g suspension stabilizer C-SA56L + 1.8g defoamer + 302g sea water.

[0150] Wherein, the high temperature anti-fading agent is silicon powder, the mass percentage of silicon dioxide in the silicon powder is greater than 97%, and the particle size of the silicon powder is a mixture of 800 mesh and 100 mesh in a mass ratio of 1:1.

[0151] The fluid loss reducer is a five-element copolymer of 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate and octadecyl polyoxyethylene ether methacrylate, and the specific preparation method is as follows:

[0152] a. Weigh 68 g of 2-acrylamide-2-methylpropanesulfonic acid, 10 g of N,N-dimethylacrylamide, 8 g of fumaric acid, 3 g of sodium styrene sulfonate and 8 g of octadecyl polyoxyethylene ether methacrylate in parts by weight for later use;

[0153] b. Dissolve 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate and octadecyl polyoxyethylene ether methacrylate in water with stirring to obtain a mixed solution;

[0154] c. Use sodium hydroxide to adjust the pH of the mixed solution to 6.4; heat to 62.4°C, introduce nitrogen for 20 minutes, initiate with ammonium persulfate, and react for 6 hours to obtain a fluid loss reducer.

[0155] The retarder is C-R52L purchased from Blue Ocean Boda Technology Co., Ltd.

[0156] The defoamer is an ester defoamer C-DF60L purchased from Blue Ocean Boda Technology Co., Ltd.

[0157] The suspension stabilizer is C-SA56L purchased from Blue Ocean Boda Technology Co., Ltd.

[0158] Example 4

[0159] Experimental temperature: 210℃, cement slurry density: 1.68g / cm 3 .

[0160] Cement slurry formula: 600g G-grade Shandong cement + 300g high temperature anti-decay agent + 48g glass beads + 54g fluid loss reducer + 24g retarder C-R52L + 12g suspension stabilizer C-SA56L + 1.8g defoamer + 30g enhancer + 384g sea water.

[0161] Wherein, the high temperature anti-fading agent is silicon powder, the mass percentage of silicon dioxide in the silicon powder is greater than 97%, and the particle size of the silicon powder is a mixture of 800 mesh and 100 mesh in a mass ratio of 1:1.

[0162] The reinforcing agent is high-strength micro-silicon.

[0163] The fluid loss additive is a five-element copolymer of 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate and hexadecyl dimethyl benzyl ammonium chloride, and the specific preparation method is as follows:

[0164] a. Weigh 61 g of 2-acrylamide-2-methylpropanesulfonic acid, 17 g of N,N-dimethylacrylamide, 6 g of fumaric acid, 4 g of sodium styrene sulfonate and 6 g of hexadecyldimethylbenzyl ammonium chloride in portions by weight for later use;

[0165] b. Dissolve 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate and hexadecyldimethylbenzyl ammonium chloride in water with stirring to obtain a mixed solution;

[0166] c. Use sodium hydroxide to adjust the pH of the mixed solution to 6.7; heat to 60.7°C, introduce nitrogen for 25 minutes, initiate with azobisisobutylamidine hydrochloride, and react for 6 hours to obtain a fluid loss reducer.

[0167] The retarder is C-R52L purchased from Blue Ocean Boda Technology Co., Ltd.

[0168] The defoamer is an ester defoamer C-DF60L purchased from Blue Ocean Boda Technology Co., Ltd.

[0169] The suspension stabilizer is C-SA56L purchased from Blue Ocean Boda Technology Co., Ltd.

[0170] Example 5

[0171] Experimental temperature: 220℃, cement slurry density: 2.2g / cm 3 .

[0172] Cement slurry formula: 600g G-grade Shandong cement + 50% high temperature anti-decay agent + 60% weighting agent + 9% fluid loss reducer + 4% retarder C-R52L + 2% suspension stabilizer C-SA56L + 0.3% defoaming agent + 297.18g sea water.

[0173] Wherein, the high temperature anti-fading agent is silicon powder, the mass percentage of silicon dioxide in the silicon powder is greater than 97%, and the particle size of the silicon powder is a mixture of 800 mesh and 100 mesh in a mass ratio of 1:1.

[0174] The weighting agent is a mixture of 200-mesh iron ore powder and 200-mesh iron ore powder in a mass ratio of 1:1.

[0175] The fluid loss reducer is a five-element copolymer of 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate and octadecyl polyoxyethylene ether methacrylate, and the specific preparation method is as follows:

[0176] a. Weigh 65 g of 2-acrylamide-2-methylpropanesulfonic acid, 15 g of N,N-dimethylacrylamide, 8 g of fumaric acid, 4 g of sodium styrene sulfonate and 4 g of octadecyl polyoxyethylene ether methacrylate in parts by weight for later use;

[0177] b. Dissolve 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate and octadecyl polyoxyethylene ether methacrylate in water with stirring to obtain a mixed solution;

[0178] c. Use sodium hydroxide to adjust the pH of the mixed solution to 6.4; heat to 61.6°C, introduce nitrogen for 20 minutes, initiate with azobisisobutylamidine hydrochloride, and react for 6 hours to obtain a fluid loss reducer.

[0179] The retarder is C-R52L purchased from Blue Ocean Boda Technology Co., Ltd.

[0180] The defoamer is an ester defoamer C-DF60L purchased from Blue Ocean Boda Technology Co., Ltd.

[0181] The suspension stabilizer is C-SA56L purchased from Blue Ocean Boda Technology Co., Ltd.

[0182] Example 6

[0183] Experimental temperature: 200℃, cement slurry density: 1.9g / cm 3 .

[0184] Cement slurry formula: 600g G-grade Shandong cement + 210g high-temperature anti-fade agent + 48g fluid loss reducer + 48g resin + 21g retarder C-R52L + 9g suspension stabilizer C-SA56L + 6g defoamer + 257.8g sea water.

[0185] Wherein, the high-temperature anti-fading agent is silicon powder, the mass percentage of silicon dioxide in the silicon powder is greater than 97%, and the particle size of the silicon powder is 100 mesh.

[0186] The resin is styrene-butadiene resin.

[0187] The fluid loss reducer is a five-element copolymer of 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate and carboxymethyl octadecylmethyldiallylammonium chloride, and the specific preparation method is as follows:

[0188] a. Weigh 67 g of 2-acrylamide-2-methylpropanesulfonic acid, 13 g of N,N-dimethylacrylamide, 7 g of fumaric acid, 3 g of sodium styrene sulfonate and 5 g of carboxymethyl octadecylmethyldiallylammonium chloride in portions by weight for later use;

[0189] b. Dissolve 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate and carboxymethyl octadecylmethyldiallylammonium chloride in water with stirring to obtain a mixed solution;

[0190] c. Use sodium hydroxide to adjust the pH of the mixed solution to 6.2; heat to 62.2°C, introduce nitrogen for 20 minutes, initiate with sodium persulfate, and react for 6 hours to obtain a fluid loss reducer.

[0191] The retarder is C-R52L purchased from Blue Ocean Boda Technology Co., Ltd.

[0192] The defoamer is an ester defoamer C-DF60L purchased from Blue Ocean Boda Technology Co., Ltd.

[0193] The suspension stabilizer is C-SA56L purchased from Blue Ocean Boda Technology Co., Ltd.

[0194] Example 7

[0195] Experimental temperature: 200℃, cement slurry density: 1.9g / cm 3 .

[0196] Cement slurry formula: 600g G-grade Shandong cement + 210g high temperature anti-fade agent + 48g fluid loss reducer + 48g latex + 21g retarder C-R52L + 9g suspension stabilizer C-SA56L + 6g defoamer + 240.6g sea water.

[0197] Wherein, the high-temperature anti-fading agent is silicon powder, the mass percentage of silicon dioxide in the silicon powder is greater than 97%, and the particle size of the silicon powder is 800 meshes.

[0198] The fluid loss reducer is a five-element copolymer of 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate and octadecyl polyoxyethylene ether methacrylate, and the specific preparation method is as follows:

[0199] a. Weigh 66 g of 2-acrylamide-2-methylpropanesulfonic acid, 19 g of N,N-dimethylacrylamide, 6 g of fumaric acid, 2 g of sodium styrene sulfonate and 7 g of octadecyl polyoxyethylene ether methacrylate in parts by weight for later use;

[0200] b. Dissolve 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate and octadecyl polyoxyethylene ether methacrylate in water with stirring to obtain a mixed solution;

[0201] c. Use sodium hydroxide to adjust the pH of the mixed solution to 6.4; heat to 60.9°C, introduce nitrogen for 20 minutes, initiate with ammonium persulfate, and react for 6 hours to obtain a fluid loss reducer.

[0202] The retarder is C-R52L purchased from Blue Ocean Boda Technology Co., Ltd.

[0203] The defoamer is an ester defoamer C-DF60L purchased from Blue Ocean Boda Technology Co., Ltd.

[0204] The suspension stabilizer is C-SA56L purchased from Blue Ocean Boda Technology Co., Ltd.

[0205] Comparative Example 1

[0206] Experimental temperature: 210℃, cement slurry density: 1.9g / cm 3 .

[0207] Cement slurry formula: 600g G-grade Shandong cement + 300g high temperature anti-decay agent + 54g fluid loss reducer + 24g retarder C-R52L + 12g suspension stabilizer C-SA56L + 1.8g defoamer + 302g sea water.

[0208] Wherein, the high temperature anti-fading agent is silicon powder, the mass percentage of silicon dioxide in the silicon powder is greater than 97%, and the particle size of the silicon powder is a mixture of 800 mesh and 100 mesh in a mass ratio of 1:1.

[0209] The fluid loss agent is the high-temperature fluid loss agent C-FL80L currently used by COSL. The preparation method of the fluid loss agent is as follows: weigh 71.7g of 2-acrylamide-2-methylpropanesulfonic acid, 7.4g of N,N-dimethylacrylamide, and 0.5g of N,N-methylenebisacrylamide by weight and set aside;

[0210] b. dissolving 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide and N,N-methylenebisacrylamide in water to obtain a mixed solution;

[0211] c. Use sodium hydroxide to adjust the pH of the mixed solution to 5.4; heat to 60.9°C, introduce nitrogen for 20 minutes, initiate with ammonium persulfate, and react for 2.5 hours to obtain a fluid loss reducer.

[0212] The defoamer is an ester defoamer C-DF60L purchased from Blue Ocean Boda Technology Co., Ltd.

[0213] The retarder is C-R52L purchased from Blue Ocean Boda Technology Co., Ltd.

[0214] The suspension stabilizer is C-SA56L purchased from Blue Ocean Boda Technology Co., Ltd.

[0215] The preparation method adopted for the cement slurry system is:

[0216] (1) mixing cement and high temperature anti-fading agent according to a proportion to obtain a solid mixture;

[0217] (2) Mixing seawater, high-temperature fluid loss reducer C-FL80L, retarder, suspension stabilizer, and defoamer according to a proportion to obtain slurry preparation water;

[0218] (3) Place the slurry water on the agitator, rotate the agitator at a low speed (4000±200 rpm), add the solid mixture into the slurry water within 15 seconds, cover the agitator, and continue stirring at a high speed (12000±500 rpm) for 75 seconds to mix evenly to obtain a cement slurry system.

[0219] Comparative Example 2

[0220] Experimental temperature: 210℃, cement slurry density: 1.9g / cm 3 .

[0221] Cement slurry formula: 600g G-grade Shandong cement + 300g high temperature anti-decay agent + 54g fluid loss reducer + 24g retarder C-R52L + 12g suspension stabilizer C-SA56L + 1.8g defoamer + 302g sea water.

[0222] Wherein, the high temperature anti-fading agent is silicon powder, the mass percentage of silicon dioxide in the silicon powder is greater than 97%, and the particle size of the silicon powder is a mixture of 800 mesh and 100 mesh in a mass ratio of 1:1.

[0223] The fluid loss agent is C-FL87L, a seawater fluid loss agent currently used by COSL. The preparation method of the fluid loss agent is as follows: weigh 69.5g of 2-acrylamide-2-methylpropanesulfonic acid, 6.2g of acrylamide, and 1.06g of itaconic acid, and set aside;

[0224] b. dissolving 2-acrylamide-2-methylpropanesulfonic acid, acrylamide and itaconic acid in water to obtain a mixed solution;

[0225] c. Use sodium hydroxide to adjust the pH of the mixed solution to 6.7; heat to 60.9°C, introduce nitrogen for 20 minutes, initiate with ammonium persulfate, and react for 2.5 hours to obtain a fluid loss reducer.

[0226] The defoamer is an ester defoamer C-DF60L purchased from Blue Ocean Boda Technology Co., Ltd.

[0227] The retarder is C-R52L purchased from Blue Ocean Boda Technology Co., Ltd.

[0228] The suspension stabilizer is C-SA56L purchased from Blue Ocean Boda Technology Co., Ltd.

[0229] The preparation method adopted for the cement slurry system is:

[0230] (1) mixing cement and high temperature anti-fading agent according to a proportion to obtain a solid mixture;

[0231] (2) mixing seawater, seawater fluid loss reducer C-FL87L, retarder, suspension stabilizer, and defoamer according to a proportion to obtain slurry water;

[0232] (3) Place the slurry water on the agitator, rotate the agitator at a low speed (4000±200 rpm), add the solid mixture into the slurry water within 15 seconds, cover the agitator, and continue stirring at a high speed (12000±500 rpm) for 35 seconds to mix evenly, thereby obtaining an ultra-high temperature seawater cement slurry system.

[0233] Comparative Example 3

[0234] Experimental temperature: 210℃, cement slurry density: 1.9g / cm 3 .

[0235] Cement slurry formula: 600g G-grade Shandong cement + 300g high-temperature anti-fade agent + 54g fluid loss reducer + 24g retarder C-R52L + 1.8g defoamer + 310.8g sea water.

[0236] Wherein, the high temperature anti-fading agent is silicon powder, the mass percentage of silicon dioxide in the silicon powder is greater than 97%, and the particle size of the silicon powder is a mixture of 800 mesh and 100 mesh in a mass ratio of 1:1.

[0237] The fluid loss reducer is a five-element copolymer of 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate and octadecyl polyoxyethylene ether methacrylate, and the specific preparation method is as follows:

[0238] a. Weigh 68 g of 2-acrylamide-2-methylpropanesulfonic acid, 10 g of N,N-dimethylacrylamide, 8 g of fumaric acid, 3 g of sodium styrene sulfonate and 8 g of octadecyl polyoxyethylene ether methacrylate in parts by weight for later use;

[0239] b. Dissolve 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate and octadecyl polyoxyethylene ether methacrylate in water with stirring to obtain a mixed solution;

[0240] c. Use sodium hydroxide to adjust the pH of the mixed solution to 6.4; heat to 62.4°C, introduce nitrogen for 20 minutes, initiate with sodium persulfate, and react for 6 hours to obtain a fluid loss reducer.

[0241] The defoamer is an ester defoamer C-DF60L purchased from Blue Ocean Boda Technology Co., Ltd.

[0242] The retarder is C-R52L purchased from Blue Ocean Boda Technology Co., Ltd.

[0243] The preparation method adopted for the cement slurry system is:

[0244] (1) mixing cement and high temperature anti-fading agent according to a proportion to obtain a solid mixture;

[0245] (2) mixing seawater, a fluid loss reducer, a retarder, and a defoamer according to a proportion to obtain slurry preparation water;

[0246] (3) Place the slurry water on the agitator, rotate the agitator at a low speed (4000±200 rpm), add the solid mixture into the slurry water within 15 seconds, cover the agitator, and continue stirring at a high speed (12000±500 rpm) for 30 seconds to mix evenly to obtain an ultra-high temperature seawater cement slurry system.

[0247] Comparative Example 4

[0248] Experimental temperature: 210℃, cement slurry density: 1.9g / cm 3 .

[0249] Cement slurry formula: 600g G-grade Shandong cement + 50% high temperature anti-decay agent + 9% fluid loss reducer + 4% retarder + 2% suspension stabilizer C-SA56L + 0.3% defoamer + 302g sea water.

[0250] Wherein, the high temperature anti-fading agent is silicon powder, the mass percentage of silicon dioxide in the silicon powder is greater than 97%, and the particle size of the silicon powder is a mixture of 800 mesh and 100 mesh in a mass ratio of 1:1.

[0251] The fluid loss reducer is a five-element copolymer of 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate and behenyl polyoxyethylene methacrylate, and the specific preparation method is as follows:

[0252] a. Weigh 68 g of 2-acrylamide-2-methylpropanesulfonic acid, 10 g of N,N-dimethylacrylamide, 8 g of fumaric acid, 3 g of sodium styrene sulfonate and 8 g of behenyl polyoxyethylene methacrylate, and set aside;

[0253] b. Dissolve 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate and behenyl polyoxyethylene methacrylate in water with stirring to obtain a mixed solution;

[0254] c. Use sodium hydroxide to adjust the pH of the mixed solution to 6.4; heat to 62.4°C, introduce nitrogen for 25 minutes, initiate with azobisisobutylamidine hydrochloride, and react for 6 hours to obtain a fluid loss reducer.

[0255] The retarder is the polymer retarder C-R40L (a copolymer of 2-acrylamide-2-methylpropanesulfonic acid and itaconic acid, purchased from Weihui Chemical Co., Ltd.) used by CNOOC Oilfield Services.

[0256] The defoamer is an ester defoamer C-DF60L purchased from Blue Ocean Boda Technology Co., Ltd.

[0257] The suspension stabilizer is C-SA56L purchased from Blue Ocean Boda Technology Co., Ltd.

[0258] The preparation method adopted for the cement slurry system is:

[0259] (1) mixing cement and high temperature anti-fading agent according to a proportion to obtain a solid mixture;

[0260] (2) mixing seawater, a fluid loss reducer, a retarder, a suspension stabilizer, and a defoamer according to a proportion to obtain slurry preparation water;

[0261] (3) Place the slurry water on the agitator, rotate the agitator at a low speed (4000±200 rpm), add the solid mixture into the slurry water within 15 seconds, cover the agitator, and continue stirring at a high speed (12000±500 rpm) for 30 seconds to mix evenly to obtain an ultra-high temperature seawater cement slurry system.

[0262] Cement slurry performance test

[0263] The cement slurry performance test was carried out in accordance with GB / T 19139 2012 "Test Methods for Oil Well Cement". The stability test was carried out in accordance with Chapter 15 of GB / T 19139 2012, the water loss test was carried out in accordance with Chapter 10 of GB / T 19139 2012, the compressive strength test was carried out in accordance with Chapter 7 of GB / T 19139 2012, the thickening time test was carried out in accordance with Chapter 9 of GB / T 19139 2012, and the rheological properties test was carried out in accordance with Chapter 12 of GB / T19139 2012. The comprehensive properties of the cement slurries of Examples 1-7 and Comparative Examples 1-4 are summarized in Table 1, and the thickening time curves of the cement slurry systems of Examples 1-7 at high temperatures are shown in Table 1. Figure 1-Figure 7 .

[0264] Table 1 Summary of comprehensive properties of cement slurry

[0265]

[0266] The symbol “-” indicates no data.

[0267] It can be seen from the above table that the cement slurry prepared in Examples 1-7 has the ability to mix cement, slurry fluidity, free liquid, water loss, cement stone stability, and compressive strength that meet the requirements of cementing construction. The thickening curve is stable, and there is no abnormal gelation phenomenon such as core encapsulation and bulging. The fluid loss reducer used in Comparative Example 1 is a high-temperature polymer fluid loss reducer C-FL80L. The polymer fluid loss reducer molecular chains adsorbed on the cement particles are bridged and bridged with the divalent metal ions present in seawater, and the cement slurry is thixotropic. The fluid loss reducer in Comparative Example 2 is the currently used seawater fluid loss reducer, which has a low molecular weight, poor water loss control ability at ultra-high temperatures, and poor slurry stabilization ability. The cement slurry and cement stone settle, and the thickening curve has an abnormal gelation phenomenon of core encapsulation. In Comparative Example 3, no suspension stabilizer was added, and the cement slurry would undergo dilution and sedimentation at ultra-high temperatures. The slurry was unstable, and the difference in density between the upper and lower cement stones was large. The retarder in Comparative Example 4 is a polymer retarder R40L, and the carboxyl group is incompatible with the Ca in seawater. 2+ Cross-linking occurs, and the cement slurry forms a local structure, resulting in bulging.

[0268] The present invention has been disclosed above with preferred embodiments, but those skilled in the art should understand that these embodiments are only used to describe the present invention and should not be understood as limiting the scope of the present invention. It should be noted that all changes and substitutions equivalent to these embodiments should be deemed to be included in the scope of the claims of the present invention. Therefore, the scope of protection of the present invention should be based on the scope defined in the claims.

Claims

1. An ultra-high temperature seawater cement slurry system, characterized in that: include: Cement, high temperature anti-decay agent, fluid loss reducer, retarder, suspension stabilizer, defoamer, sea water.

2. The ultra-high temperature seawater cement slurry system according to claim 1, characterized in that: In terms of weight, the cement is 100 parts, the high temperature anti-fading agent is 30-60 parts, the fluid loss reducer is 6-13 parts, the retarder is 2.5-5 parts, the suspension stabilizer is 1-2 parts, the defoamer is 0.25-1.5 parts, and the seawater is 40-67 parts.

3. The ultra-high temperature seawater cement slurry system according to claim 1, characterized in that: In terms of weight, the cement is 100 parts, the high temperature anti-fading agent is 35-50 parts, the fluid loss reducer is 8-12 parts, the retarder is 2.5-4 parts, the suspension stabilizer is 1.5-2 parts, the defoamer is 0.3-1 parts, and the seawater is 42-65 parts.

4. The ultra-high temperature seawater cement slurry system according to claim 1, characterized in that: The cement is Class G oil well cement.

5. The ultra-high temperature seawater cement slurry system according to claim 1, characterized in that: The high temperature anti-fading agent is silicon powder with a mass percentage of silicon dioxide greater than 97%.

6. The ultra-high temperature seawater cement slurry system according to claim 1, characterized in that: The particle size of the silicon powder is 100 mesh, 300 mesh and / or 800 mesh.

7. The ultra-high temperature seawater cement slurry system according to claim 1, characterized in that: The fluid loss reducer is a five-element copolymer of 2-acrylamide-2-methylpropane sulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate and a long side chain functional monomer.

8. The ultra-high temperature seawater cement slurry system according to claim 7, characterized in that: The weight ratio of the 2-acrylamide-2-methylpropanesulfonic acid, the N,N-dimethylacrylamide, the fumaric acid, the sodium styrene sulfonate and the long side chain functional monomer is (60-70): (10-20): (6-10): (2-4): (4-8).

9. The ultra-high temperature seawater cement slurry system according to claim 7 or 8, characterized in that: The long side chain functional monomer includes one or more of hexadecyl dimethyl benzyl ammonium chloride, behenyl polyoxyethylene methacrylate, carboxymethyl octadecyl methyl diallyl ammonium chloride, and octadecyl polyoxyethylene ether methacrylate.

10. The ultra-high temperature seawater cement slurry system according to claim 1, characterized in that: The retarder is a 2-acrylamide-2-methylpropane sulfonic acid polymer retarder or a mixture of a 2-acrylamide-2-methylpropane sulfonic acid polymer retarder and an organic phosphonate retarder.

11. The ultra-high temperature seawater cement slurry system according to claim 10, characterized in that: The retarder is a mixture of a 2-acrylamide-2-methylpropanesulfonic acid polymer retarder, an organic phosphonate retarder and a hydroxycarboxylate retarder in a mass ratio of (2-3): (0.5-1): (0.5-2).

12. The ultra-high temperature seawater cement slurry system according to claim 1, characterized in that: The suspension stabilizer is an inorganic-organic hybrid material prepared by compounding vinyl acetate polymer, Wenlun gum and sepiolite in a mass ratio of 5:(1-2):(3-4).

13. The ultra-high temperature seawater cement slurry system according to claim 1, characterized in that: The defoaming agent is an ester defoaming agent, an organosilicon defoaming agent or a silicone ether oil defoaming agent.

14. The method for preparing the ultra-high temperature seawater cement slurry system according to any one of claims 1 to 13, characterized in that: include: (1) mixing cement and high temperature anti-fading agent according to a proportion to obtain a solid mixture; (2) mixing seawater, a fluid loss reducer, a retarder, a suspension stabilizer, and a defoamer according to a proportion to obtain slurry preparation water; (3) The slurry preparation water is placed on a stirrer with a rotation speed of 4000±200 rpm, the solid mixture is added to the slurry preparation water within 15 seconds, and the mixture is stirred for 30-50 seconds at a rotation speed of 12000±500 rpm to obtain an ultra-high temperature seawater cement slurry system.

15. The preparation method according to claim 14, characterized in that: The fluid loss reducer is prepared by the following method: a. The weight ratio of (60-70): (10-20): (6-10): (2-4): (4-8) of 2-acrylamide-2-methylpropanesulfonic acid, N, N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate and long side chain monomers were dissolved in water to obtain a mixed solution; b. Use alkali to adjust the pH of the mixed solution to 6-7 and heat it to 60-65°C; c. After nitrogen is introduced for 20-30 minutes, the initiator is used to initiate the reaction. After 4-6 hours of reaction, the fluid loss reducer is obtained.

16. The preparation method according to claim 14, characterized in that: The long side chain monomers include: one or more of hexadecyl dimethyl benzyl ammonium chloride, behenyl polyoxyethylene methacrylate, carboxymethyl octadecyl methyl diallyl ammonium chloride, and octadecyl polyoxyethylene ether methacrylate.

17. The preparation method according to claim 14, characterized in that: The initiator is one or more of sodium persulfate, ammonium persulfate, and azobisisobutyramidine hydrochloride.

18. The preparation method according to claim 14, characterized in that: The added amount of the initiator is 0.1-0.3 parts.

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