A high-temperature seawater cement slurry system and its preparation method

Abstract

This invention belongs to the field of oilfield chemical technology, specifically relating to ultra-high temperature cement slurry technology, and more particularly to an ultra-high temperature seawater cement slurry system and its preparation method. The ultra-high temperature seawater cement slurry system provided by this invention includes: cement, a high-temperature anti-fading agent, a fluid loss reducing agent, a retarder, a suspension stabilizer, a defoamer, and seawater. The ultra-high temperature seawater cement slurry system of this invention can be applied in seawater at 230℃, exhibits excellent ultra-high temperature resistance, and possesses good fluidity, low API fluid loss, adjustable thickening time, compressive strength meeting cementing construction requirements, and no free fluid generation, fully meeting all cementing construction requirements.

Description

Technical Field

[0001] This invention belongs to the field of oilfield chemical technology, and relates to ultra-high temperature cement slurry technology, and particularly to an ultra-high temperature seawater cement slurry system and its preparation method. Background Technology

[0002] my country is a major maritime power with abundant offshore oil and gas resources. However, the overall development level of these resources is currently relatively low. With the recoverable and easily recoverable reserves of onshore oil gradually decreasing, developing offshore exploration and development, as well as deep and ultra-deep well cementing technologies, is a major trend in future technological development. Offshore oil and gas resources are widely distributed globally, accounting for approximately half of the total reserves in the four oceans and the Persian Gulf, with some seawater wells reaching ultra-high temperatures of 210°C.

[0003] Currently, most cement slurry systems used in nearshore cementing operations are prepared with fresh water, requiring the transportation of fresh water from land or the desalination of seawater, which impacts both cost and efficiency. Using seawater to prepare cement slurry can improve the capability of offshore cementing operations. Seawater-based slurry can be sourced locally, without being limited by transportation or desalination equipment, and it also helps reduce costs and increase efficiency in nearshore operations.

[0004] Currently, most researchers focus on freshwater cement slurry systems, paying less attention to seawater cement slurry systems. Commercially available cementing additives and cement slurry systems face the following problems when used in seawater: First, seawater contains some metal ions such as calcium... 2+ Mg 2+ First, bridging and cross-linking can occur between the polymer water-reducing agent molecules adsorbed on cement particles, leading to poor cement slurry fluidity and even thixotropy. Second, polymer molecules are prone to coiling in the seawater ionic environment, affecting their adsorption on cement particles and resulting in increased water loss at high and ultra-high temperatures. Third, compared to freshwater, the complex ions in seawater cause abnormal gelation phenomena in the cement slurry, such as core formation and thickening. The retarder dosage and temperature sensitivity are poor, posing a challenge to the safety of cementing operations.

[0005] Chinese invention patent application number 201410492102.X discloses a novel high-temperature, low-density cement slurry system. The components and their weight proportions of this novel low-density cement slurry system are as follows: 100 parts oil well cement, 50-80 parts fly ash, 30-40 parts silica sand, 24-76 parts active reinforcing agent I, 13-60 parts active reinforcing agent II, 8.0-17 parts high-temperature water loss reducing agent, 0.2-0.8 parts high-temperature retarder, 0.0-0.5 parts dispersant, and 140-200 parts water. The density of this cement slurry is 1.40-1.60 g / cm³. 3It is adjustable and can be used for cementing operations in the range of 70–150°C. However, for the ultra-high temperature environment of seawater wells with a circulating temperature of 210°C, this cement slurry system cannot meet the operational requirements.

[0006] Chinese invention patent application number 201710312962.4 discloses a dispersible solid water loss control agent for seawater cement slurry and its preparation method. The prepared dispersible water loss control agent, when applied to seawater cement slurry, exhibits good fluidity and excellent water loss control ability; however, water loss experiments were only conducted at 60°C. The paper does not investigate the water loss control ability of this agent at high and ultra-high temperatures in seawater, nor its overall performance in relation to the cement slurry system. Furthermore, the reaction product requires freeze-drying, making the synthesis process relatively complex.

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

[0008] Chinese invention patent application number 201910423555.X discloses a cementing slurry system and its application. It includes cement, a high-temperature stabilizer, an anti-brittleness agent, and a high-temperature expansion agent, combined with a filtration loss reducer, a dispersant, a retarder, and a defoamer. The cementing slurry prepared by this invention, after setting and hardening, not only reduces the elastic modulus of the cement stone, improves its brittleness, enhances its deformation capacity under stress, and increases its impact toughness while maintaining high strength, but also compensates for various shrinkages of the cement stone and enhances the bonding capacity of the cement annulus interface, meeting the cementing requirements of high-pressure gas wells. However, this invention is mainly used in freshwater, and the maximum temperature of the cementing slurry system is 140℃. For the ultra-high temperature environment of seawater wells with a circulation temperature of 210℃, this cementing slurry system cannot meet the operational requirements.

[0009] Chinese invention patent application number 202110550154.8 discloses a low-density cement slurry system suitable for medium- and high-temperature formations and its preparation method. The system comprises 50%–55% oil well cement, 30%–35% fly ash, 7%–15% microsilica, 0.5%–2% slurry stabilizer, 0.1%–2% nano-liquid silica emulsion, 0.2%–1% early-strength agent, 0.5%–2.5% fluid loss reducer, 0.2%–0.8% drag reducer, and 0.1%–2% retarder. This cement slurry system is suitable for low-pressure formations at medium- and high temperatures, within the freshwater range of 80℃–150℃.

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

[0011] Therefore, developing a seawater cement slurry system applicable at ultra-high temperatures remains a challenge in this field. Summary of the Invention

[0012] To address the above-mentioned shortcomings and deficiencies, this invention provides an ultra-high temperature seawater cement slurry system and its preparation method.

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

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

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

[0016] The cement in the aforementioned ultra-high temperature seawater cement slurry system is Grade G oil well cement.

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

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

[0019] In the aforementioned ultra-high temperature seawater cement slurry system, the water loss reducing agent is a pentagonal copolymer of 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate, and long-side-chain functional monomers.

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

[0021] In the aforementioned ultra-high temperature seawater cement slurry system, the long side-chain functional monomers include one or more of hexadecyl dimethyl benzyl ammonium chloride, docosyl 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-methylpropanesulfonic acid polymer retarder or a mixture of a 2-acrylamide-2-methylpropanesulfonic acid polymer retarder and an organophosphonate retarder.

[0023] In the above-mentioned ultra-high temperature seawater cement slurry system, the retarder is a mixture of 2-acrylamide-2-methylpropanesulfonic acid polymer retarder, organophosphonate retarder, and 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 composed of vinyl acetate polymer, styrene, 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 defoamer is an ester-based defoamer, an organosilicon-based defoamer, or a silicone ether oil-based defoamer.

[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) Mix cement and high-temperature anti-fading agent according to the proportion to obtain a solid mixture;

[0028] (2) Mix seawater with water loss reducer, retarder, suspension stabilizer and defoamer according to the proportion to obtain slurry water;

[0029] (3) Place the slurry water on a mixer at a speed of 4000±200 rpm, add the solid mixture to the slurry water within 15 seconds, and continue stirring at a speed of 12000±500 rpm for 30-50 seconds to mix evenly, and obtain an ultra-high temperature seawater cement slurry system.

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

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

[0032] b. Adjust the pH of the mixed solution to 6-7 using alkali and heat to 60-65℃;

[0033] c. After purging with nitrogen for 20-30 minutes, initiate the reaction with an initiator. After 4-6 hours of reaction, the dehydration reducing agent is obtained.

[0034] The above-mentioned method for preparing ultra-high temperature seawater cement slurry system includes, in the case of, one or more of the following long-side-chain monomers: 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 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 ultra-high temperature seawater cement slurry system, the amount of 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 applied in seawater at 230℃, has excellent resistance to ultra-high temperature, and has good slurry fluidity, low API water loss, adjustable thickening time, compressive strength that meets the requirements of cementing construction, and no free fluid is generated, which fully meets the requirements of cementing construction.

[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 be used to 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. Attached Figure Description

[0041] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention.

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

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

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

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

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

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

[0048] Figure 7 This is the thickening time curve of the cement slurry system at 200℃ in Example 7 of the present invention. Detailed Implementation

[0049] To fully understand the purpose, features, and effects of this invention, the following detailed embodiments are provided. Except as described below, the process methods of this invention employ conventional methods or apparatus in the art. Unless otherwise specified, the terms and expressions used below have the meanings commonly understood by those skilled in the art.

[0050] The terms "preferred," "more preferred," etc., used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0051] When a range of values ​​is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0052] An ultra-high temperature seawater cement slurry system includes: cement, high temperature anti-fading agent, water loss reducing agent, retarder, suspension stabilizer, defoamer, and seawater.

[0053] In the ultra-high temperature seawater cement slurry system of the present invention, the components with specific contents work 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 will be described in detail below.

[0055] cement

[0056] Cement is a powdery hydraulic inorganic binder that forms a paste when mixed with water. It can harden in air or water and can firmly bind materials such as sand and stone together.

[0057] Preferably, the cement used in this invention is G-grade oil well cement that meets API specifications.

[0058] Grade G oil well cement has suitable density and setting time, and low consistency. Cement slurries prepared using it as a base material exhibit excellent settling stability and flowability. During cementing operations, it can quickly set and harden, generating a certain compressive strength. After solidification, the cement stone has good impermeability, stability, and corrosion resistance, meeting the requirements of subsequent oil and gas well construction.

[0059] High-temperature anti-fading agent

[0060] At temperatures exceeding 110°C, the compressive strength of Grade G oil well cement stone rapidly declines with prolonged curing, which can negatively impact the quality of cement ring sealing under high temperatures over time. Adding a high-temperature anti-fading agent ensures the cement stone's mechanical strength and bonding performance can withstand the high-temperature, high-pressure environment downhole.

[0061] The high-temperature anti-fading agent is a silicon powder with a silicon dioxide content greater than 97% by mass.

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

[0063] In this invention, the content of the high-temperature anti-fading agent in the cement slurry system is 30-60 parts per 100 parts by weight of cement. In the cement slurry system, if the content of the high-temperature anti-fading agent is too low, the cement stone will experience strength degradation, reduced mechanical properties, and increased permeability after long-term service; if the content of the high-temperature anti-fading agent is too high, cement mixing becomes more difficult, the fluidity of the cement slurry deteriorates, and pumping becomes unfavorable.

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

[0065] Water loss reducer

[0066] Water loss reducers are a class of admixtures that can control and reduce the loss of cement slurry filtrate into the formation.

[0067] During cementing operations, the cement slurry will undergo "filtration" when passing through high-permeability formations under pressure. If the cement slurry loses too much water, its density, thickening time, and flow properties will change, affecting the safety of the cementing operation. The highly alkaline filtrate of the cement slurry entering the reservoir can also cause some degree of damage.

[0068] The water loss reducing agent used in this invention is a pentagonal copolymer of 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate and long side-chain functional monomers.

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

[0070] The weight-average molecular weight of the pentagonal copolymer is 800,000 to 1,200,000.

[0071] The preparation method of the water loss reducing agent of the present invention includes the following steps:

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

[0073] b. Adjust the pH of the mixed solution to 6-7 using alkali and heat to 60-65℃;

[0074] c. After purging with nitrogen for 20-30 minutes, initiate the reaction with an initiator. After 4-6 hours of reaction, the water loss reducing agent is obtained.

[0075] The initiator is one or more of sodium persulfate, ammonium persulfate, and azobisisobutyramidine hydrochloride; the amount of the initiator added is 0.1-0.3 parts.

[0076] The water loss control agent prepared according to the method of the present invention contains long side group monomers in its functional groups. These monomers do not bridge to form a network structure in the high-valence metal ion environment of seawater, nor do they produce a polyelectrolyte effect that causes molecular chain coiling. In this way, the water loss control agent can be better adsorbed on the surface of cement particles, block cement pores, and achieve a good water loss control effect, while maintaining the excellent fluidity of cement slurry and avoiding thixotropy and thickening.

[0077] In this invention, the content of the water loss reducing agent in the cement slurry system is 6-13 parts per 100 parts by weight of cement. In the cement slurry system, if the content of the water loss reducing agent is too low, the water loss of the cement slurry becomes uncontrollable, and the properties of the cement slurry, such as density, rheology, and thickening time, will change; if the content of the water loss reducing agent is too high, the cement slurry becomes too thick, has poor fluidity, and affects pumping.

[0078] Preferably, the content of the water loss reducing agent in the cement slurry system of the present invention is 8-12 parts per 100 parts by weight of cement.

[0079] Retarder

[0080] Retarder is an admixture used to extend the hydration and hardening time of cement, so that the cement slurry can maintain good fluidity during the pumping process to the designated location, and the cementing operation can be carried out safely and smoothly.

[0081] The retarder used in this invention is a polymer retarder of 2-acrylamide-2-methylpropanesulfonic acid, or a mixture of polymer retarder of 2-acrylamide-2-methylpropanesulfonic acid and organophosphonate retarder, or a polymer retarder of 2-acrylamide-2-methylpropanesulfonic acid and organophosphonate retarder, or a hydroxycarboxylate retarder.

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

[0083] The retarder is composed of AMPS polymer, organophosphate, and hydroxycarboxylate. Compared with pure polymer retarder, organophosphate and hydroxycarboxylate have stronger adsorption and chelation effects with cement particles, which can reduce the cross-linking of carboxyl groups with ions in seawater, effectively solve abnormal gelation phenomena such as core formation and bulging of cement slurry in seawater, and also effectively reduce the temperature sensitivity and dosage sensitivity of cement slurry thickening time at high temperatures. It can also achieve good compatibility with other materials.

[0084] The 2-acrylamido-2-methylpropanesulfonic acid polymer is a copolymer of 2-acrylamido-2-methylpropanesulfonic 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; and the organophosphonate is one or more of ethylenediaminetetramethylenephosphonate pentasodium, diethylenetriaminepentamethylenephosphonate pentasodium, aminotrimethylenephosphonate tetrasodium, and hydroxyethylidene diphosphate sodium.

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

[0086] In this invention, the retarder content in the cement slurry system is 2.5-5 parts per 100 parts by weight of cement. In the cement slurry system, if the retarder content is too low, the cement slurry will set too quickly, posing a safety hazard to the cementing site; if the retarder content is too high, the cement slurry will exhibit side effects such as excessively slow setting, long thickening time, and slow strength development of the cement stone.

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

[0088] Suspension stabilizer

[0089] Under high and ultra-high temperature conditions, cement slurry thins, reducing its ability to suspend solid particles, which then tend to aggregate and settle. Therefore, under high temperature conditions, a suspending stabilizer needs to be added to ensure good settling stability of the cement slurry.

[0090] The high-temperature suspension stabilizer used in this invention is an inorganic-organic hybrid material composed of vinyl acetate polymer, vinyl acetate, and sepiolite. It has the advantages of minimal impact on the rheology of cement slurry at low temperatures and good suspension stability at high temperatures, thus completely solving the problems of slow mixing, high viscosity, severe dilution at high and ultra-high temperatures, and poor stability of high-temperature cement slurry.

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

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

[0093] In this invention, the content of the suspension stabilizer in the cement slurry system is 1-2 parts per 100 parts by weight of cement. In the cement slurry system, if the content of the suspension stabilizer is too low, the cement slurry will have poor suspension ability at high temperatures, resulting in sedimentation and heterogeneity; if the content of the suspension stabilizer is too high, it may lead to poor fluidity of the cement slurry.

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

[0095] defoaming agent

[0096] Defoamers, also known as foam breakers, are used to eliminate harmful foam or inhibit foam generation during the preparation of cement slurry systems.

[0097] The defoamer used in this invention is an ester-based defoamer or an organosilicon-based defoamer.

[0098] Ester-based defoamers include Span 80 and tributyl phosphate; organosilicon-based defoamers include polydimethylsiloxane, fluorosiloxane, and ethylene glycol siloxane.

[0099] In this invention, the defoamer content in the cement slurry system is 0.25-1.5 parts per 100 parts by weight of cement. In the cement slurry system, if the defoamer content is too low, a large number of air bubbles will be generated, leading to inaccurate cement slurry density measurement. In severe cases, this can even prevent mixing during on-site construction, resulting in cementing accidents. Conversely, if the defoamer content is too high, a large amount of oily substances will be mixed into the cement slurry, affecting the cement stone bonding.

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

[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 density of the cement slurry. When different cement slurry densities are designed, the amount of seawater used will also be different.

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

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

[0104] Based on 100 parts by weight of cement, the content of reinforcing agent in the cement slurry system of the present invention is 4-10 parts. In the cement slurry system, when the content of reinforcing agent is too low, the strength of the cement stone is low, which does not meet the requirements of cementing construction; when the content of reinforcing agent is too high, the ultrafine material makes it difficult to mix the cement slurry.

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

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

[0107] Based on 100 parts by weight of cement, the content of weighting agent in the cement slurry system of the present invention is 60-200 parts. In the cement slurry system, when the content of weighting agent is too low, the water requirement is too low, the cement slurry is difficult to mix, and the slurry fluidity is poor; when the content of weighting agent is too high, the relative content of cementitious components is low, which affects the strength development of cement stone.

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

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

[0110] Based on 100 parts by weight of cement, the resin content in the cement slurry system of this invention is 3-11 parts. In the cement slurry system, if the resin content is too low, the anti-gas channeling performance and cement stone bonding performance of the cement slurry will be poor; if the resin content is too high, it will affect the mixing ability and fluidity of the cement slurry.

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

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

[0113] Based on 100 parts by weight of cement, the latex content in the cement slurry system of this invention is 5-12 parts. In the cement slurry system, when the latex content is too low, the toughness of the cement stone, the settling stability of the cement slurry, and the anti-gas channeling performance are poor; when the latex content is too high, the latex breaks down, the slurry becomes unstable, and the strength development of the cement stone is slow.

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

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

[0116] Based on 100 parts by weight of cement, the content of the light-reducing agent in the cement slurry system of the present invention is 5-12 parts. In the cement slurry system, when the content of the light-reducing agent is too low, 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 stone; when the content of the light-reducing agent is too high, the solid content is too high, and it is difficult to mix the slurry.

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

[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) Mix cement and high-temperature anti-fading agent according to the proportion to obtain a solid mixture;

[0120] (2) Mix seawater with water loss reducer, retarder, suspension stabilizer and defoamer according to the proportion to obtain slurry water;

[0121] (3) Place the grouting water on the mixer, rotate the mixer at a low speed (4000±200 rpm), and add the solid mixture into the grouting water within 15 seconds. Cover the mixer and continue to stir at a high speed (12000±500 rpm) for 30-50 seconds to mix evenly and obtain the ultra-high temperature seawater cement grout system.

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

[0123] Example

[0124] The present invention is further illustrated below by way of examples, but the invention is not limited to the scope of the examples described herein. 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 formulations of the ultra-high temperature seawater cement slurry system in each example are as follows.

[0125] Example 1

[0126] Experimental temperature: 180℃, cement slurry density: 1.9 g / cm³ 3 .

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

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

[0129] The water loss reducing agent is a pentagonal copolymer of 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate, and long-side-chain functional monomers. The specific preparation method is as follows:

[0130] a. Weigh out the following ingredients in the indicated weight proportions: 64g 2-acrylamide-2-methylpropanesulfonic acid, 14g N,N-dimethylacrylamide, 6g fumaric acid, 2g sodium styrene sulfonate, and 5g carboxymethyl octadecylmethyl diallyl ammonium chloride. Set aside for later use.

[0131] b. Dissolve 2-acrylamido-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate, and carboxymethyl octadecylmethyl diallyl ammonium chloride in water to obtain a mixed solution.

[0132] c. Adjust the pH of the mixed solution to 6.2 with sodium hydroxide; heat to 63.7℃, purge with nitrogen for 20 minutes, then initiate with sodium persulfate, and after 6 hours of reaction, the dehydration reducer is obtained.

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

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

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

[0136] Example 2

[0137] Experimental temperature: 210℃, cement slurry density: 1.9g / cm³ 3 .

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

[0139] The high-temperature anti-fading agent is silicon powder, wherein the silicon powder contains more than 97% silicon dioxide by mass and the particle size of the silicon powder is 800 mesh.

[0140] The water loss reducing agent is a pentagonal copolymer of 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate, and docosyl polyoxyethylene methacrylate. The specific preparation method is as follows:

[0141] a. Weigh out the following proportions by weight: 60g 2-acrylamide-2-methylpropanesulfonic acid, 18g N,N-dimethylacrylamide, 8g fumaric acid, 3g sodium styrene sulfonate and 4g dodecyl polyoxyethylene methacrylate. Set aside for later use.

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

[0143] c. The pH of the mixed solution was adjusted to 6.2 using sodium hydroxide; after heating to 61.5℃ and purging with nitrogen for 20 minutes, ammonium persulfate was used as the initiator, and the reaction was carried out for 6 hours to obtain the dehydration reducing agent.

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

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

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

[0147] Example 3

[0148] Experimental temperature: 230℃, cement slurry density: 1.9 g / cm³ 3 .

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

[0150] The high-temperature anti-fading agent is silicon powder, wherein the silicon powder contains more than 97% silicon dioxide by mass, and the silicon powder is a mixture of 800 mesh and 100 mesh particles in a 1:1 mass ratio.

[0151] The water loss reducing agent is a pentagonal copolymer of 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate, and octadecyl polyoxyethylene ether methacrylate. The specific preparation method is as follows:

[0152] a. Weigh out the following components by weight: 68g 2-acrylamide-2-methylpropanesulfonic acid, 10g N,N-dimethylacrylamide, 8g fumaric acid, 3g sodium styrene sulfonate and 8g octadecyl polyoxyethylene ether methacrylate. Set aside 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 to obtain a mixed solution.

[0154] c. The pH of the mixed solution was adjusted to 6.4 using sodium hydroxide; after heating to 62.4℃ and purging with nitrogen for 20 minutes, ammonium persulfate was used as the initiator, and the reaction was carried out for 6 hours to obtain the dehydration reducing agent.

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

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

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

[0158] Example 4

[0159] Experimental temperature: 210℃, cement slurry density: 1.68 g / cm³ 3 .

[0160] Cement slurry formula: 600g Grade G Shandong cement + 300g high temperature anti-fading agent + 48g glass microspheres + 54g water loss reducer + 24g retarder C-R52L + 12g suspension stabilizer C-SA56L + 1.8g defoamer + 30g reinforcing agent + 384g seawater.

[0161] The high-temperature anti-fading agent is silicon powder, wherein the silicon powder contains more than 97% silicon dioxide by mass, and the silicon powder is a mixture of 800 mesh and 100 mesh particles in a 1:1 mass ratio.

[0162] The reinforcing agent is high-strength microsilicon.

[0163] The water loss reducing agent is a pentagonal copolymer of 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate, and hexadecyl dimethyl benzyl ammonium chloride. The specific preparation method is as follows:

[0164] a. Weigh 61g of 2-acrylamide-2-methylpropanesulfonic acid, 17g of N,N-dimethylacrylamide, 6g of fumaric acid, 4g of sodium styrene sulfonate and 6g of hexadecyl dimethyl benzyl ammonium chloride by weight, and set aside.

[0165] b. Dissolve 2-acrylamido-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate and hexadecyl dimethyl benzyl ammonium chloride in water to obtain a mixed solution;

[0166] c. The pH of the mixed solution was adjusted to 6.7 using sodium hydroxide; after heating to 60.7℃ and purging with nitrogen for 25 minutes, azobisisobutyramidine hydrochloride was used as the initiator, and the reaction was carried out for 6 hours to obtain the dehydration reducing agent.

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

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

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

[0170] Example 5

[0171] Experimental temperature: 220℃, cement slurry density: 2.2g / cm³ 3 .

[0172] Cement slurry formula: 600g Grade G Shandong cement + 50% high temperature anti-fading agent + 60% weighting agent + 9% water loss reducing agent + 4% retarder C-R52L + 2% suspension stabilizer C-SA56L + 0.3% defoamer + 297.18g seawater.

[0173] The high-temperature anti-fading agent is silicon powder, wherein the silicon powder contains more than 97% silicon dioxide by mass, and the silicon powder is a mixture of 800 mesh and 100 mesh particles in a 1:1 mass ratio.

[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 water loss reducing agent is a pentagonal copolymer of 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate, and octadecyl polyoxyethylene ether methacrylate. The specific preparation method is as follows:

[0176] a. Weigh out the following ingredients in the indicated weight proportions: 65g 2-acrylamide-2-methylpropanesulfonic acid, 15g N,N-dimethylacrylamide, 8g fumaric acid, 4g sodium styrene sulfonate, and 4g octadecyl polyoxyethylene ether methacrylate. Set aside 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 to obtain a mixed solution.

[0178] c. The pH of the mixed solution was adjusted to 6.4 using sodium hydroxide; after heating to 61.6℃ and purging with nitrogen for 20 min, azobisisobutyramidine hydrochloride was used as the initiator, and the reaction was carried out for 6 h to obtain the dehydration reducing agent.

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

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

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

[0182] Example 6

[0183] Experimental temperature: 200℃, cement slurry density: 1.9 g / cm³ 3 .

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

[0185] The high-temperature anti-fading agent is silicon powder, wherein the silicon powder contains more than 97% silicon dioxide by mass and the particle size of the silicon powder is 100 mesh.

[0186] The resin is styrene-butadiene resin.

[0187] The water loss reducing agent is a pentagonal copolymer of 2-acrylamido-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate, and carboxymethyl octadecylmethyl diallyl ammonium chloride. The specific preparation method is as follows:

[0188] a. Weigh out the following ingredients by weight: 67g 2-acrylamide-2-methylpropanesulfonic acid, 13g N,N-dimethylacrylamide, 7g fumaric acid, 3g sodium styrene sulfonate, and 5g carboxymethyl octadecylmethyl diallyl ammonium chloride. Set aside for later use.

[0189] b. Dissolve 2-acrylamido-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate, and carboxymethyl octadecylmethyl diallyl ammonium chloride in water to obtain a mixed solution.

[0190] c. The pH of the mixed solution was adjusted to 6.2 using sodium hydroxide; after heating to 62.2℃ and purging with nitrogen for 20 minutes, sodium persulfate was used as the initiator, and the reaction was carried out for 6 hours to obtain the dehydration reducing agent.

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

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

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

[0194] Example 7

[0195] Experimental temperature: 200℃, cement slurry density: 1.9 g / cm³ 3 .

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

[0197] The high-temperature anti-fading agent is silicon powder, wherein the silicon powder contains more than 97% silicon dioxide by mass and the particle size of the silicon powder is 800 mesh.

[0198] The water loss reducing agent is a pentagonal copolymer of 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate, and octadecyl polyoxyethylene ether methacrylate. The specific preparation method is as follows:

[0199] a. Weigh out the following ingredients in the indicated weight proportions: 66g 2-acrylamide-2-methylpropanesulfonic acid, 19g N,N-dimethylacrylamide, 6g fumaric acid, 2g sodium styrene sulfonate, and 7g octadecyl polyoxyethylene ether methacrylate. Set aside 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 to obtain a mixed solution.

[0201] c. The pH of the mixed solution was adjusted to 6.4 using sodium hydroxide; after heating to 60.9℃ and purging with nitrogen for 20 minutes, ammonium persulfate was used as the initiator, and the reaction was carried out for 6 hours to obtain the dehydration reducing agent.

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

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

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

[0205] Comparative Example 1

[0206] Experimental temperature: 210℃, cement slurry density: 1.9g / cm³ 3 .

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

[0208] The high-temperature anti-fading agent is silicon powder, wherein the silicon powder contains more than 97% silicon dioxide by mass, and the silicon powder is a mixture of 800 mesh and 100 mesh particles in a 1:1 mass ratio.

[0209] The water loss reducing agent is C-FL80L, a high-temperature water loss reducing agent currently used by CNOOC Oilfield Services. The preparation method of this water loss reducing 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. Dissolve 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, and N,N-methylenebisacrylamide in water to obtain a mixed solution;

[0211] c. Adjust the pH of the mixed solution to 5.4 using sodium hydroxide; heat to 60.9℃, purge with nitrogen for 20 minutes, then initiate with ammonium persulfate, and after 2.5 hours of reaction, the dehydration reducer is obtained.

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

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

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

[0215] The preparation method used for the cement slurry system is as follows:

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

[0217] (2) Mix seawater with high-temperature water loss reducing agent C-FL80L, retarder, suspension stabilizer and defoamer according to the formula to obtain slurry water;

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

[0219] Comparative Example 2

[0220] Experimental temperature: 210℃, cement slurry density: 1.9g / cm³ 3 .

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

[0222] The high-temperature anti-fading agent is silicon powder, wherein the silicon powder contains more than 97% silicon dioxide by mass, and the silicon powder is a mixture of 800 mesh and 100 mesh particles in a 1:1 mass ratio.

[0223] The water loss reducing agent is C-FL87L, a seawater water loss reducing agent currently used by CNOOC Services. The preparation method of this water loss reducing agent is as follows: Weigh 69.5g of 2-acrylamide-2-methylpropanesulfonic acid, 6.2g of acrylamide, and 1.06g of itaconic acid by weight, and set aside.

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

[0225] c. Adjust the pH of the mixed solution to 6.7 using sodium hydroxide; heat to 60.9℃, purge with nitrogen for 20 minutes, then initiate with ammonium persulfate, and after 2.5 hours of reaction, the dehydration reducer is obtained.

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

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

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

[0229] The preparation method used for the cement slurry system is as follows:

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

[0231] (2) Mix seawater, seawater loss reducer C-FL87L, retarder, suspension stabilizer and defoamer according to the ratio to obtain slurry water;

[0232] (3) Place the grouting water on the mixer, rotate the mixer at a low speed (4000±200 rpm), and add the solid mixture into the grouting water within 15 seconds. Cover the mixer and continue to stir at a high speed (12000±500 rpm) for 35 seconds to mix evenly and obtain the ultra-high temperature seawater cement grout system.

[0233] Comparative Example 3

[0234] Experimental temperature: 210℃, cement slurry density: 1.9g / cm³ 3 .

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

[0236] The high-temperature anti-fading agent is silicon powder, wherein the silicon powder contains more than 97% silicon dioxide by mass, and the silicon powder is a mixture of 800 mesh and 100 mesh particles in a 1:1 mass ratio.

[0237] The water loss reducing agent is a pentagonal copolymer of 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate, and octadecyl polyoxyethylene ether methacrylate. The specific preparation method is as follows:

[0238] a. Weigh out the following components by weight: 68g 2-acrylamide-2-methylpropanesulfonic acid, 10g N,N-dimethylacrylamide, 8g fumaric acid, 3g sodium styrene sulfonate and 8g octadecyl polyoxyethylene ether methacrylate. Set aside 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 to obtain a mixed solution.

[0240] c. The pH of the mixed solution was adjusted to 6.4 using sodium hydroxide; after heating to 62.4℃ and purging with nitrogen for 20 minutes, sodium persulfate was used as the initiator, and the reaction was carried out for 6 hours to obtain the dehydration reducing agent.

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

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

[0243] The preparation method used for the cement slurry system is as follows:

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

[0245] (2) Mix seawater with water loss reducer, retarder and defoamer according to the proportion to obtain slurry water;

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

[0247] Comparative Example 4

[0248] Experimental temperature: 210℃, cement slurry density: 1.9g / cm³ 3 .

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

[0250] The high-temperature anti-fading agent is silicon powder, wherein the silicon powder contains more than 97% silicon dioxide by mass, and the silicon powder is a mixture of 800 mesh and 100 mesh particles in a 1:1 mass ratio.

[0251] The water loss reducing agent is a pentagonal copolymer of 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate, and docosyl polyoxyethylene methacrylate. The specific preparation method is as follows:

[0252] a. Weigh out the following components by weight: 68g 2-acrylamide-2-methylpropanesulfonic acid, 10g N,N-dimethylacrylamide, 8g fumaric acid, 3g sodium styrene sulfonate and 8g dodecyl polyoxyethylene methacrylate. Set aside for later use.

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

[0254] c. The pH of the mixed solution was adjusted to 6.4 using sodium hydroxide; after heating to 62.4℃ and purging with nitrogen for 25 minutes, azobisisobutyramidine hydrochloride was used as the initiator, and the reaction was carried out for 6 hours to obtain the dehydration reducing agent.

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

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

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

[0258] The preparation method used for the cement slurry system is as follows:

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

[0260] (2) Mix seawater with water loss reducer, retarder, suspension stabilizer and defoamer according to the proportion to obtain slurry water;

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

[0262] Cement grout performance test

[0263] The performance tests of the cement slurry were conducted according to GB / T 19139-2012 "Test Methods for Oil Well Cement". Stability testing was performed according to Chapter 15 of GB / T 19139-2012; water loss testing according to Chapter 10 of GB / T 19139-2012; compressive strength testing according to Chapter 7 of GB / T 19139-2012; thickening time testing according to Chapter 9 of GB / T 19139-2012; and rheological properties testing according to Chapter 12 of GB / T 19139-2012. The comprehensive performance of the cement slurry in Examples 1-7 and Comparative Examples 1-4 is summarized in Table 1. The thickening time curves of the cement slurry systems in Examples 1-7 at high temperatures are shown in [Table 1]. Figures 1-7 .

[0264] Table 1 Summary of Comprehensive Performance of Cement Grout

[0265]

[0266] The symbol "-" indicates no data.

[0267] As can be seen from the table above, the cement slurries prepared in Examples 1-7 all meet the requirements for cementing construction in terms of mixing ability, fluidity, free fluid, water loss, cement stone stability, and compressive strength. The thickening curves are stable, and no abnormal gelling phenomena such as core inclusions or bulging occur. In Comparative Example 1, the water loss control agent used is the high-temperature polymer water loss control agent C-FL80L. The polymer water loss control agent molecular chains adsorbed on cement particles bridge and cross-link with divalent metal ions present in seawater, causing thixotropy in the cement slurry. In Comparative Example 2, the water loss control agent is a currently used seawater water loss control agent with a lower molecular weight. It has poor water loss control ability at ultra-high temperatures and poor slurry stabilization ability, resulting in sedimentation of the cement slurry and cement stone, and abnormal gelling phenomena with core inclusions appearing in the thickening curve. In Comparative Example 3, no suspension stabilizer was added. The cement slurry will dilute and settle at ultra-high temperatures, resulting in slurry instability and a large density difference between the upper and lower layers of the cement stone. In Comparative Example 4, the retarder is the polymer retarder R40L. The carboxyl groups react with the Ca in seawater... 2+ Cross-linking occurs, and local structures form in the cement slurry, resulting in bulging.

[0268] The present invention has been disclosed above with reference to preferred embodiments. However, those skilled in the art should understand that these embodiments are merely illustrative of the invention and should not be construed as limiting its scope. It should be noted that any variations and substitutions equivalent to these embodiments should be considered to be covered within the scope of the claims. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. An ultra-high temperature seawater cement slurry system, characterized in that, By weight, it includes 100 parts cement, 30-60 parts high-temperature anti-fading agent, 6-13 parts water loss reducing agent, 2.5-5 parts retarder, 1-2 parts suspension stabilizer, 0.25-1.5 parts defoamer, and 40-67 parts seawater. The water loss reducing agent is a pentagonal copolymer of 2-acrylamido-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate, and a long-side-chain functional monomer; the weight ratio of 2-acrylamido-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate, and the long-side-chain functional monomer is (60-70):(10-20):(6-10):(2-4):(4-8); the long-side-chain functional 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. The retarder is a mixture of 2-acrylamide-2-methylpropanesulfonic acid polymer retarder, organophosphonate retarder, and hydroxycarboxylate retarder in a mass ratio of (2-3):(0.5-1):(0.5-2).

2. The ultra-high temperature seawater cement slurry system according to claim 1, characterized in that, By weight, the cement is 100 parts, the high-temperature anti-fading agent is 35-50 parts, the water loss reducing agent 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.

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

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

5. The ultra-high temperature seawater cement slurry system according to claim 4, characterized in that, The silicon powder has a particle size of 100 mesh, 300 mesh and / or 800 mesh.

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

7. The ultra-high temperature seawater cement slurry system according to claim 1, characterized in that, The defoamer is an ester-based defoamer, an organosilicon-based defoamer, or a silicone ether oil-based defoamer.

8. The method for preparing the ultra-high temperature seawater cement slurry system according to any one of claims 1-7, characterized in that, include: (1) Mix cement and high-temperature anti-fading agent according to the proportion to obtain a solid mixture; (2) Mix seawater with water loss reducer, retarder, suspending stabilizer and defoamer according to the proportion to obtain slurry water; (3) Place the slurry water on a mixer with a speed of 4000±200 rpm. Add the solid mixture to the slurry water within 15 seconds and continue stirring for 30-50 seconds at a speed of 12000±500 rpm to mix evenly and obtain an ultra-high temperature seawater cement slurry system.

9. The preparation method according to claim 8, characterized in that, The water loss reducing agent is prepared by the following method: a. Dissolve 2-acrylamide-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, fumaric acid, sodium styrene sulfonate and long side-chain functional monomers in water in a weight ratio of (60-70):(10-20):(6-10):(2-4):(4-8) to obtain a mixed solution; b. Adjust the pH of the mixed solution to 6-7 using alkali and heat to 60-65℃; c. After purging with nitrogen for 20-30 minutes, initiate the reaction with an initiator. After 4-6 hours of reaction, the dehydration reducing agent is obtained.

10. The preparation method according to claim 9, characterized in that, The long side-chain functional monomers include one or more of the following: hexadecyl dimethyl benzyl ammonium chloride, docosyl polyoxyethylene methacrylate, carboxymethyl octadecyl methyl diallyl ammonium chloride, and octadecyl polyoxyethylene ether methacrylate.

11. The preparation method according to claim 9, characterized in that, The initiator is one or more of sodium persulfate, ammonium persulfate, and azobisisobutyramidine hydrochloride.

12. The preparation method according to claim 9, characterized in that, The amount of the initiator added is 0.1-0.3 parts.

Images