An anti-solid dispersion cement paste system and a preparation method thereof

Abstract

The application provides an anti-solid-phase dispersion cement slurry system and a preparation method thereof. The cement slurry system comprises, in parts by weight, 600-700 parts of G-grade oil well cement, 15-25 parts of superfine cement, 0.7-2.1 parts of modified methyl cellulose, 0.5-1.5 parts of anionic polyacrylamide, 0.02-0.05 parts of zwitterionic polyacrylamide, 0.7-3.5 parts of a dispersing agent, 1.4-3.5 parts of gypsum and water. The preparation method of the cement slurry system comprises the following steps: dry mixing the G-grade oil well cement, the superfine cement, the modified methyl cellulose, the dispersing agent and the gypsum; adding the polyacrylamide into water to obtain a polyacrylamide aqueous solution; and adding the dry mixed materials into the polyacrylamide aqueous solution and stirring uniformly to obtain the anti-solid-phase dispersion cement slurry system. The application provides a cement slurry system which can agglomerate solid-phase particles in the cement slurry system and resist solid-phase dispersion and dilution of formation water.

Description

TECHNICAL FIELD

[0001] The present application relates to an anti-solid phase dispersion cement slurry system and a preparation method thereof, and belongs to the technical field of well cementing operation in oilfield development. BACKGROUND

[0002] After long-term water injection in oilfields, water is seen in the wellbore, and it is necessary to carry out the operation of squeezing the water-seeing section of the wellbore to block the water-seeing layer. However, the conventional cement slurry system is easily affected by the formation fluid. The influence of the formation fluid on the cement slurry mainly lies in two aspects. First, the invasion of the formation fluid will dilute and reduce the density of the cement slurry or cause the cement slurry to dissolve and migrate, thereby causing the static liquid column pressure to drop and leading to unstable pressure. Second, the invasion of the formation fluid will destroy the cementation quality of the two interfaces, so as to form a channeling channel between the cement sheath and the formation.

[0003] Especially, the conventional cement slurry system dissolves after seeing water, resulting in poor cementing quality. Specifically, after the conventional cement slurry system is poured into water, a certain solid phase concentration of cement slurry is formed by the dissolution of solid phase particles in water, and then the cement slurry is solidified into cement stone through hydration. However, due to the infinite dilution characteristics of the solid phase particles in water, when the cementing and plugging encounter active water bodies, the cement slurry cannot be solidified into cement stone through hydration, and the cementing and plugging effect cannot be achieved.

[0004] Therefore, it has become one of the problems to be solved in the field to develop a cement slurry system that can resist solid phase dispersion in water. SUMMARY

[0005] To solve the above technical problems, the purpose of the present application is to provide an anti-solid phase dispersion cement slurry system and a preparation method thereof. The present application provides a cement slurry system that can agglomerate and resist solid phase dispersion of solid phase particles in the cement slurry system and resist dilution of formation water. The cement slurry system can solve the problems of the existing cement slurry system, such as the dissolution of solid phase particles in water, poor cementing and plugging quality, and the inability of cement stone to form strength.

[0006] To achieve the above purpose, the first aspect of the present application provides an anti-solid phase dispersion cement slurry system. The cement slurry system comprises the following raw material components in parts by weight: G-grade oil well cement 600-700 parts, ultra-fine cement 15-25 parts, modified methyl cellulose 0.7-2.1 parts, anionic polyacrylamide 0.5-1.5 parts, zwitterionic polyacrylamide 0.02-0.05 parts, polyvinyl sulfonate dispersant 0.7-3.5 parts, gypsum 1.4-3.5 parts, and water 264-476 parts.

[0007] According to the specific embodiment of the present application, preferably, the anti-solid-phase-discrete cement paste system further comprises the following raw material composition: defoaming agent 0-0.001 parts by weight. More preferably, the defoaming agent comprises one or a combination of several of organic esters, polyoxypropylene glycerol ether, and polydimethylsiloxane; and particularly preferably, the organic ester comprises tributyl phosphate.

[0008] In the anti-solid-phase-discrete cement paste system described above, preferably, the particle size of the ultra-fine cement is 800-1000 mesh.

[0009] In the anti-solid-phase-discrete cement paste system described above, preferably, the modified methyl cellulose is prepared by the following steps: mixing 1 part of wood pulp and / or cotton pulp, 1-1.3 parts (more preferably 1 part) of sodium hydroxide, and 1-1.8 parts (more preferably 1.2 parts) of water, soaking for 4-5 hours at 15-25°C; then removing the alkali solution and extruding the residual solid paste (preferably using nitrogen to remove the alkali solution) to obtain block-shaped alkali cellulose, which is ground and broken, and placed in sunlight and air for oxidation (the oxidation time is preferably more than 24 hours), and the viscosity is adjusted to be less than 1000 mpa·s to obtain aged alkali cellulose; suspending the aged alkali cellulose in chloromethane, and reacting at 1.5-2 MPa and 60-70°C for more than 5 hours (to complete etherification); and after washing and drying, the product is obtained as the modified methyl cellulose. The amount of chloromethane used is excessive, and those skilled in the art can make routine adjustments to the amount. More preferably, the washing process can be: first washing in hot water at 80-90°C, then adding an appropriate amount of hydrochloric acid or oxalic acid for decolorization, and then washing to neutral. After the washing, the modified methyl cellulose can be finally obtained as a white or off-white powder through conventional steps such as dehydration and drying.

[0010] In the anti-solid-phase-discrete cement paste system described above, preferably, the molecular weight of the anionic polyacrylamide is 3-6 million.

[0011] In the anti-solid-phase-discrete cement paste system described above, preferably, the zwitterionic polyacrylamide is prepared by the following steps: mixing anionic polyacrylamide 0.8-1.2 parts by weight, water 8-12 parts, and formaldehyde 1.2-1.6 parts, and stirring at room temperature (room temperature can be 20-30°C) for 8-12 hours, then adding dimethylamine 0.8-1.2 parts, and stirring at 35-45°C for 4-4.5 hours, then reducing the temperature to room temperature, adding dimethyl sulfate 0.3-0.5 parts, and stirring for more than 15 hours (preferably 15-20 hours) to obtain the zwitterionic polyacrylamide. More preferably, the molecular weight of the anionic polyacrylamide used is 80-100 million.

[0012] In the anti-solid dispersion cement slurry system described above, preferably, the polyvinyl sulfonate dispersant includes sodium polyvinyl sulfonate and the like.

[0013] In the anti-solid dispersion cement slurry system described above, preferably, the gypsum includes one or a combination of several of natural gypsum, mixed gypsum, and industrial by-product gypsum and the like. Those skilled in the art should understand that the mixed gypsum is a uniform gypsum powder with cementing effect prepared by fully mixing, calcining, grinding, and the like of any two or more gypsum raw materials (natural gypsum or various industrial by-product gypsums). The present application does not limit the specific composition of the mixed gypsum, which can be obtained by commercial purchase.

[0014] In the anti-solid dispersion cement slurry system described above, the G-grade oil well cement is a G-grade oil well portland cement, such as but not limited to one of Jiahua G-grade, Huayou G-grade, Shengwei G-grade, and Mengcheng G-grade and the like.

[0015] According to the specific embodiments of the present application, preferably, the viscosity of the anti-solid dispersion cement slurry system is 10-60 mPa.s.

[0016] According to the specific embodiments of the present application, preferably, the density of the anti-solid dispersion cement slurry system is 1.65-1.90 g / cm 3 .

[0017] According to the specific embodiments of the present application, preferably, the anti-solid dispersion cement slurry system is prepared by the following steps:

[0018] (1) Dry mixing and mixing 600-700 parts of G-grade oil well cement, 15-25 parts of ultra-fine cement, 0.7-2.1 parts of modified methyl cellulose, 0.7-3.5 parts of polyvinyl sulfonate dispersant, and 1.4-3.5 parts of gypsum by weight parts, so that they are uniformly mixed to obtain a dry mixture;

[0019] (2) Adding 0.5-1.5 parts of anionic polyacrylamide and 0.02-0.05 parts of zwitterionic polyacrylamide to 264-476 parts of water, and stirring uniformly to obtain a polyacrylamide aqueous solution;

[0020] (3) Adding the dry mixture to the polyacrylamide aqueous solution, and stirring uniformly to obtain the anti-solid dispersion cement slurry system.

[0021] In step (1), dry mixing can be carried out by multiple mixing to ensure uniform mixing, or by air mixing. The stirring speed and time in step (1) can be routinely adjusted by those skilled in the art. In step (2), the amount of water is calculated according to the density of the cement paste system.

[0022] In the preparation steps of the anti-solid dispersion cement paste system described above, preferably, step (2) further comprises: adding 0-0.001 parts of defoaming agent to the polyacrylamide aqueous solution to obtain a polyacrylamide aqueous solution with added defoaming agent. Those skilled in the art will understand that when the cement paste system of the present application contains a defoaming agent, after obtaining the polyacrylamide aqueous solution with added defoaming agent in step (2), step (3) accordingly adds the dry mixture to the polyacrylamide aqueous solution with added defoaming agent.

[0023] In the preparation steps of the anti-solid dispersion cement paste system described above, preferably, in laboratory preparation, step (2) specifically comprises: adding 0.5-1.5 parts of anionic polyacrylamide and 0.02-0.05 parts of zwitterionic polyacrylamide to water with a stirring speed of 8000-12000 rpm within 35 seconds, then reducing the stirring speed to 3000-4000 rpm, and stirring for more than 15 minutes (preferably 15-20 minutes) to obtain a polyacrylamide aqueous solution. Alternatively, preferably, in field preparation, step (2) specifically comprises: adding 0.5-1.5 parts of anionic polyacrylamide and 0.02-0.05 parts of zwitterionic polyacrylamide to water with a stirring speed of 1000-1200 rpm, and continuously stirring at a stirring speed of 1000-1200 rpm for more than 35 minutes (preferably 35-40 minutes) to obtain a polyacrylamide aqueous solution.

[0024] In the preparation steps of the anti-solid dispersion cement paste system described above, preferably, in laboratory preparation, step (3) specifically comprises: adding the dry mixture to the polyacrylamide aqueous solution with a stirring speed of 8000-12000 rpm within 35 seconds, then reducing the stirring speed to 3000-4000 rpm, and stirring for more than 25 seconds (preferably 25-40 seconds) to obtain the anti-solid dispersion cement paste system. Alternatively, preferably, in field preparation, step (3) specifically comprises: adding the dry mixture to the polyacrylamide aqueous solution with a stirring speed of 1000-1200 rpm within 35 seconds, and continuously stirring at a stirring speed of 1000-1200 rpm for more than 1 minute (preferably 1-3 minutes) to obtain the anti-solid dispersion cement paste system.

[0025] The second aspect of the present application provides a preparation method of the anti-solid dispersion cement slurry system, comprising the following steps:

[0026] (1) mixing and stirring 600-700 parts of G-class oil well cement, 15-25 parts of ultra-fine cement, 0.7-2.1 parts of modified methyl cellulose, 0.7-3.5 parts of polyvinyl sulfonate dispersant, and 1.4-3.5 parts of gypsum by weight to obtain dry mixture;

[0027] (2) adding 0.5-1.5 parts of anionic polyacrylamide and 0.02-0.05 parts of zwitterionic polyacrylamide into 264-476 parts of water, and stirring to obtain an aqueous polyacrylamide solution;

[0028] (3) adding the dry mixture into the aqueous polyacrylamide solution, and stirring to obtain the anti-solid dispersion cement slurry system.

[0029] In the above preparation method, in step (1), the dry mixture can be mixed and stirred for multiple times to make them uniformly mixed, or can be mixed and stirred by air mixing. The stirring speed and time in step (1) can be routinely adjusted by those skilled in the art. In step (2), the amount of water is calculated according to the density of the cement slurry system.

[0030] In the above preparation method, preferably, step (2) further comprises: adding 0-0.001 parts of defoaming agent into the aqueous polyacrylamide solution to obtain a defoaming agent-added aqueous polyacrylamide solution.

[0031] In the above preparation method, preferably, in laboratory preparation, step (2) specifically comprises: adding 0.5-1.5 parts of anionic polyacrylamide and 0.02-0.05 parts of zwitterionic polyacrylamide into water at a stirring speed of 8000-12000 rpm within 35 seconds, then reducing the stirring speed to 3000-4000 rpm, and stirring for 15 minutes or more (preferably 15-20 minutes) to obtain the aqueous polyacrylamide solution. Alternatively, preferably, in field preparation, step (2) specifically comprises: adding 0.5-1.5 parts of anionic polyacrylamide and 0.02-0.05 parts of zwitterionic polyacrylamide into water at a stirring speed of 1000-1200 rpm, and continuously stirring at a stirring speed of 1000-1200 rpm for 35 minutes or more (preferably 35-40 minutes) to obtain the aqueous polyacrylamide solution.

[0032] In the above preparation method, preferably, in the laboratory preparation, step (3) specifically comprises: adding the dry mixture into the aqueous solution of polyacrylamide at a stirring speed of 8000-12000 rpm within 35 seconds, then reducing the stirring speed to 3000-4000 rpm, and stirring for more than 25 seconds (preferably 25-40 seconds) to obtain the anti-solid-phase-dispersion cement slurry system; or, preferably, in the field preparation, step (3) specifically comprises: adding the dry mixture into the aqueous solution of polyacrylamide at a stirring speed of 1000-1200 rpm within 35 seconds, and continuously stirring at a speed of 1000-1200 rpm for more than 1 minute (preferably 1-3 minutes) to obtain the anti-solid-phase-dispersion cement slurry system.

[0033] The cement slurry system provided by the present application has the characteristics of anti-solid-phase-dispersion in water by the selection of raw materials and the ratio design of each raw material. Specifically, the anionic polyacrylamide, the zwitterionic polyacrylamide and the modified methyl cellulose selected in the present application have the following characteristics: on the one hand, the long-chain structure of the high-molecular compound, the negative charge of the active functional groups on the long carbon chain of the anionic polyacrylamide and the zwitterionic polyacrylamide can be adsorbed on the positive charge of the cement particles to form the characteristics of the vertically and horizontally intersected cement particles adsorbed on the long carbon chain, and the various particle sizes of the solid-phase particles in the cement slurry are connected together by coating to form a stable adsorption long-chain multi-chain structure; on the other hand, the functional groups of the anionic polyacrylamide, the zwitterionic polyacrylamide and the modified methyl cellulose have hydroxyl groups, which can form hydrogen bonds with water molecules to increase the affinity between the water molecules. The anionic polyacrylamide, the zwitterionic polyacrylamide and the modified methyl cellulose in the present application can maximize the viscosity of the cement slurry solid-phase particles and the long carbon chain to effectively inhibit the dispersion of the cement solid-phase particles, and ensure the cement slurry to have good anti-solid-phase-dispersion ability in water under the premise of meeting the workability. In addition, the cement slurry system of the present application also adds a polyvinyl sulfonate dispersant, which can effectively control and reduce the problem that the too strong solid-phase ability causes the cement slurry to form a group and cannot flow. After the polyvinyl sulfonate is hydrated, it can reduce the potential energy of the long-chain molecules, and thus can reduce the internal long-chain entanglement of the cement slurry system. Therefore, as shown in the figure, the cement slurry system of the present application can adsorb the cement particles by the long chain of the anionic polyacrylamide and the zwitterionic polyacrylamide, form a agglomerated interface, and adjust the tightness of the long-chain adsorption by the polyvinyl sulfonate, and increase the affinity between the water molecules by the hydroxyl groups on the functional groups of the anionic polyacrylamide and the modified methyl cellulose. Thus, the solid-phase particles in the cement slurry system of the present application can form the characteristics of anti-solid-phase-dispersion after hydration for tens of seconds to about 1 minute. Figure 1

[0034] The anti-solid-phase-dispersion cement slurry system and the preparation method thereof provided by the present application have the following excellent technical effects:​

[0035] (1) The preparation method of the cement slurry system of the present application adopts dry mixing, which reduces the long preparation time caused by a large amount of liquid mixing in the field construction, and effectively shortens the construction period.

[0036] (2) The present application locks the solid-phase particles that are easily dispersed in water in the cement slurry system, solving the problem of dispersion of solid-phase particles in the conventional cement slurry system caused by active water in the formation, which leads to dilution of the cement slurry in the annulus and failure to achieve the preset strength.

[0037] (3) The cement slurry system of the present application has good fluidity and anti-solid-phase dispersion performance, making the construction proceed smoothly.

[0038] In summary, the present application adds specific raw materials to the cement slurry system and adjusts the ratio of each raw material to produce a synergistic effect between the raw materials, thereby improving the cohesion of the cement slurry system and stabilizing the internal structure of the cement slurry system. Therefore, the present application provides a cement slurry system that can agglomerate solid-phase particles in the cement slurry system and resist solid-phase dispersion and dilution by formation water. The cement slurry system can solve the problem of easy erosion by formation water during the setting process of the existing cement slurry system, dispersion of solid-phase particles in the system in water, and unlimited dilution, resulting in poor cementing and plugging quality and inability to form strength of the cement stone, and reduce the problems of reduction of compressive strength caused by dissolution and migration of the cement slurry system under flowing water conditions. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 Figure 1 is a schematic diagram of the anti-solid-phase dispersion principle of the cement slurry system in the present application.

[0040] Figure 2 Figure 2 is a state diagram of the anti-solid-phase dispersion cement slurry system provided in Example 1 when it enters water.

[0041] Figure 3 Figure 3 is a state diagram of the conventional cement slurry system provided in Comparative Example 1 when it enters water.

[0042] Figure 4 Figure 4 is a state diagram of the cement slurry systems of Example 1 and Comparative Example 1 when they sink in water. DETAILED DESCRIPTION

[0043] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present application, the technical solutions of the present application will be described in detail below, but it should not be understood as limiting the scope of the present application.

[0044] Example 1

[0045] The embodiment provides an anti-solid-phase dispersion cement slurry system, which comprises the following raw material components in parts by weight: G-grade oil well cement (portland cement) 600 parts, superfine cement (particle size 800-1000 mesh) 18 parts, modified methyl cellulose 0.7 part, anionic polyacrylamide (molecular weight 3-6 million, Renqiu Tianshi Chemical Co., Ltd.) 0.56 part, zwitterionic polyacrylamide 0.03 part, polyvinyl sulfonic acid sodium dispersant 0.7 part, natural gypsum 1.4 part and water 274 parts.

[0046] The modified methyl cellulose is prepared by the following steps: 1 part of wood pulp and / or cotton pulp, 1 part of sodium hydroxide and 1.2 parts of water are mixed, soaked at 15 DEG C for 4 hours; then the residual solid paste is squeezed after removing the alkali solution by using nitrogen, to obtain blocky alkali cellulose, which is ground and broken, and is placed in sunlight and air for oxidation for 24 hours, and the viscosity is adjusted to be below 1000 mpa·s, to obtain aged alkali cellulose; the aged alkali cellulose is suspended in excess of chloromethane, and is reacted at 1.7 MPa and 60-70 DEG C for 5 hours (etherification is completed); the obtained product is washed in hot water at 80-90 DEG C first, then is decolorized by adding appropriate amount of hydrochloric acid or oxalic acid, and then is washed to be neutral, and is dehydrated and dried to obtain white or off-white powder, to obtain the modified methyl cellulose.

[0047] The zwitterionic polyacrylamide is prepared by the following steps: 1 part of anionic polyacrylamide (molecular weight 800-1000 million), 10 parts of water and 1.2-1.6 parts of formaldehyde are mixed and stirred at 25 DEG C for 10 hours, then 1 part of dimethylamine is added, and stirring is carried out at 35-45 DEG C for 4-4.5 hours, after reducing to room temperature, 0.3-0.5 parts of dimethyl sulfate is added, and stirring is carried out for 15 hours, to obtain the zwitterionic polyacrylamide.

[0048] The anti-solid-phase dispersion cement slurry system is prepared by the following steps:

[0049] (1) the G-grade oil well cement, the superfine cement, the modified methyl cellulose, the polyvinyl sulfonic acid sodium dispersant and the natural gypsum are dry-stirred and mixed in the above weight parts, so that they are uniformly mixed, to obtain dry mixture;

[0050] (2) the anionic polyacrylamide and the zwitterionic polyacrylamide are uniformly poured into water which is stirred at high speed (stirring speed is 8000-12000 revolutions / minute) in the above weight parts within 30 seconds, then the stirring speed is reduced to 3000 revolutions / minute, and stirring is carried out for 15 minutes, to obtain polyacrylamide aqueous solution;

[0051] (3) The dry mixture is poured into the high-speed stirring (stirring speed of 12000 rpm) polyacrylamide aqueous solution at a uniform speed within 25 seconds, and then low-speed stirring is performed at a speed of 3000 rpm for 25 seconds to form a solid phase dispersion resistance feature, thereby obtaining the solid phase dispersion resistance cement slurry system.

[0052] The viscosity of the solid phase dispersion resistance cement slurry system of the present embodiment is about 50 mPa.s, and the density is 1.85 g / cm 3 , and the compressive strength is 32.5 MPa under 80℃ / 48h curing.

[0053] The solid phase dispersion resistance cement slurry system provided in the present embodiment is added into water, and the state of the cement slurry system entering the water is shown in Figure 2 It can be seen that the cement slurry system of the present embodiment is naturally separated from the water body after entering the water, and has no solid phase dispersion resistance feature.

[0054] Embodiment 2

[0055] The solid phase dispersion resistance cement slurry system provided in the present embodiment comprises the following raw material components in parts by weight: G-grade oil well cement (portland cement) 600 parts, ultra-fine cement (particle size of 800-1000 mesh) 18 parts, modified methyl cellulose 0.7 parts, anionic polyacrylamide (molecular weight of 3-6 million, Renqiu Tianshi Chemical Co., Ltd.) 0.56 parts, zwitterionic polyacrylamide 0.03 parts, polyvinyl sulfonate dispersant 0.7 parts, natural gypsum 1.4 parts, and water 360 parts.

[0056] The preparation methods of the modified methyl cellulose and the zwitterionic polyacrylamide are the same as those of Embodiment 1.

[0057] The preparation method of the solid phase dispersion resistance cement slurry system is the same as that of Embodiment 1.

[0058] The viscosity of the solid phase dispersion resistance cement slurry system of the present embodiment is about 40 mPa.s, and the density is 1.75 g / cm 3 .

[0059] Embodiment 3

[0060] The solid phase dispersion resistance cement slurry system provided in the present embodiment has the same raw material components as those of Embodiment 1, except that it further comprises a defoaming agent in an amount of 0-0.001 parts by weight.

[0061] The solid phase dispersion resistance cement slurry system is prepared by the following steps:

[0062] (1) The G-grade oil well cement, the superfine cement, the modified methyl cellulose, the polyvinyl sulfonic acid sodium dispersant, and the natural gypsum are mixed uniformly by using the on-site air mixing method to obtain a dry mixture, according to the weight parts above.

[0063] (2) The polyacrylamide aqueous solution is obtained by adding the anionic polyacrylamide and the zwitterionic polyacrylamide into the stirring water in the cement mixing pool of the cement truck at a slow speed, and continuously stirring at a speed of 1000 rpm for 35 min. If the foaming is obvious, the defoaming agent (for example, tributyl phosphate) is used for defoaming. The amount of the defoaming agent is 0-0.001 parts by weight. The defoaming is performed until the state of the polyacrylamide aqueous solution is not affected.

[0064] (3) The dry mixture is poured into the polyacrylamide aqueous solution with the defoaming agent and stirring (stirring speed is 1000 rpm) at a uniform speed within 25 s, and then the stirring is continuously performed at a speed of 1000 rpm for 1 min. The anti-solid phase dispersion cement slurry system is obtained.

[0065] The viscosity of the anti-solid phase dispersion cement slurry system of the embodiment is 40-60 mPa.s, and the density is 1.85 g / cm 3 .

[0066] Example 4

[0067] The anti-solid phase dispersion cement slurry system of the embodiment is prepared by using the following raw material components in parts by weight: G-grade oil well cement (portland cement) 700 parts, superfine cement (particle size is 800-1000 mesh) 15 parts, modified methyl cellulose 0.7 parts, anionic polyacrylamide (molecular weight is 3-6 million, Rengqu Tianshi Chemical Co., Ltd.) 0.5 parts, zwitterionic polyacrylamide 0.03 parts, polyvinyl sulfonic acid sodium dispersant 0.7 parts, mixed gypsum 1 part, and water 420 parts.

[0068] The preparation methods of the modified methyl cellulose and the zwitterionic polyacrylamide are the same as those of Example 1.

[0069] The preparation method of the anti-solid phase dispersion cement slurry system is the same as that of Example 1.

[0070] The viscosity of the anti-solid phase dispersion cement slurry system of the embodiment is 20 mPa.s, and the density is 1.75 g / cm 3 .

[0071] Comparative Example 1

[0072] The comparative example provides a conventional cement slurry system, which comprises the following raw material components by weight parts: G-grade oil well cement 600 parts and water 274 parts. The G-grade oil well cement is G-grade oil well portland cement, such as but not limited to one of the following: Ji Hua G-grade, Hua oil G-grade, Shengwei G-grade, and Mengcheng G-grade, etc.

[0073] The conventional cement slurry system is prepared by the following steps: G-grade oil well cement 600 parts by weight is poured into water 274 parts in high-speed stirring (stirring speed is 12000 rpm), stirring for 35 s, to obtain the conventional cement slurry system.

[0074] The conventional cement slurry system provided by the comparative example is added to water, and the state of entering the water is as shown in Figure 3 It can be seen that the cement slurry system of the comparative example is obviously discrete and mixed after entering the water.

[0075] Figure 4 The state diagram of the cement slurry system of Example 1 and Comparative Example 1 sinking in water. The left is the anti-solid phase discrete cement slurry system provided by Example 1 sinking in water, it can be seen that the water and the cement slurry system are obviously layered, and there is no mixing and no discrete. The right is the conventional cement slurry system provided by Comparative Example 1 sinking in water, it can be seen that the water and the cement slurry system are not obviously layered, and the discrete state is obvious. After the conventional cement slurry system is poured into water, the mixed slurry formed by removing the discrete by filtration is compared with the cement slurry system of Example 1, the initial viscosity is about 15 mPa.s, and the density is 1.83 g / cm 3 , which is 0.02 kg / m 3 lower than the density of the anti-solid phase discrete cement slurry system in Example 1. The two cement slurry systems are cured at 80℃ for 48 h, and the compressive strength of the conventional cement slurry system is 25.7 MPa, which is lower than the strength of the anti-solid phase discrete cement slurry system of Example 1.

[0076] Comparative Example 2

[0077] The comparative example provides a cement slurry system, which comprises the following raw material components by weight parts: G-grade oil well cement (portland cement) 700 parts, ultra-fine cement (particle size is 800-1000 mesh) 15 parts, modified methyl cellulose 3.0 parts, anionic polyacrylamide (molecular weight is 3-6 million, Renqiu Tianshi Chemical Co., Ltd.) 2.2 parts, polyvinyl sulfonic acid sodium dispersant 0.5 parts, mixed gypsum 1 part, and water 306 parts.

[0078] The preparation method of the cement slurry system is the same as that of Example 1. However, when the polyacrylamide aqueous solution is added to the dry cement mixture in this system, instantaneous flash coagulation lumps are formed.

[0079] The cement slurry system of the present comparative example has a density of 1.85 g / cm 3 However, the fluidity thereof cannot be guaranteed, and the cement slurry system cannot form the feature of resisting solid phase dispersion.

[0080] Comparative Example 3

[0081] The present comparative example provides a cement slurry system, which comprises the following raw material components by weight: G-grade oil well cement (portland cement) 700 parts, superfine cement (particle size of 800-1000 mesh) 15 parts, modified methyl cellulose 3.0 parts, cationic polyacrylamide 0.5-1.2 parts, sodium polyvinyl sulfonate dispersant 0.5 parts, mixed gypsum 1 part, and water 306 parts.

[0082] The cement slurry system is prepared in the same manner as in Example 1. However, instant flash coagulation and lumping occur when the polyacrylamide aqueous solution is added to the dry cement mixture in the system.

[0083] The cement slurry system of the present comparative example has a density of 1.85 g / cm 3 However, the fluidity thereof cannot be guaranteed. In the cement slurry system of the present comparative example, cationic polyacrylamide with an arbitrary molecular weight is used, and no zwitterionic polyacrylamide is added, and thus the system cannot form the feature of resisting solid phase dispersion.

[0084] Comparative Example 4

[0085] The present comparative example provides a cement slurry system, which comprises the following raw material components by weight: G-grade oil well cement (portland cement) 700 parts, superfine cement (particle size of 800-1000 mesh) 15 parts, modified methyl cellulose 3.0 parts, anionic polyacrylamide (molecular weight of 3-6 million, produced by Renqiu Shentian Chemical Co., Ltd.) 2.2 parts, polyhydroxy carboxylic acid (salt) dispersant 0.5-1.0 parts, mixed gypsum 1 part, and water 306 parts. The polyhydroxy carboxylic acid (salt) dispersant comprises one or a combination of several of citric acid, tartaric acid, and salicylic acid.

[0086] The cement slurry system is prepared in the same manner as in Example 1. However, after the polyacrylamide aqueous solution is added to the dry cement mixture in the system, the system is poured into water and exhibits the phenomenon of unstable dispersion and lumping at the same time.

[0087] The cement slurry system of the present comparative example has a density of 1.85 g / cm 3 However, the fluidity thereof cannot be guaranteed. In the cement slurry system of the present comparative example, polyhydroxy carboxylic acid (salt) dispersant is used, and the system cannot form the feature of resisting solid phase dispersion at different amounts.

[0088] Comparative Example 5

[0089] A cement paste system was prepared according to the following formulation: 700 parts of Class G oil well cement (portland cement), 15 parts of ultra-fine cement (800-1000 mesh), 3.0 parts of modified methylcellulose, 0.5-1.2 parts of non-ionic polyacrylamide, 0.5 parts of sodium polyvinyl sulfonate dispersant, 1 part of mixed gypsum, and 306 parts of water.

[0090] The cement paste system was prepared according to the same procedure as in Example 1. However, the system did not have the anti-solid phase dispersion characteristic after the step of adding the polyacrylamide aqueous solution to the dry cement mixture.

[0091] The cement paste system of this comparative example had a density of 1.85 g / cm 3 However, it did not have the anti-solid phase dispersion characteristic. This comparative example used non-ionic polyacrylamide of arbitrary molecular weight in the cement paste system, and did not add zwitterionic polyacrylamide, so the system could not form the anti-solid phase dispersion characteristic.

Claims

1. A cement slurry system resistant to solid-phase dispersion, wherein the cement slurry system comprises the following raw materials in parts by weight: 600-700 parts of Grade G oil well cement, 15-25 parts of ultrafine cement, 0.7-2.1 parts of modified methylcellulose, 0.5-1.5 parts of anionic polyacrylamide, 0.02-0.05 parts of zwitterionic polyacrylamide, 0.7-3.5 parts of polyethylene sulfonate dispersant, 1.4-3.5 parts of gypsum, 0-0.001 parts of defoamer, and 264-476 parts of water; The modified methylcellulose is prepared by the following steps: 1 part by weight of wood pulp and / or cotton pulp, 1-1.3 parts by weight of sodium hydroxide, and 1-1.8 parts by weight of water are mixed and soaked at 15-25°C for 4-5 hours; then, after removing the alkali solution, the remaining solid paste is squeezed to obtain blocky alkali cellulose, which is then ground and crushed, and placed in sunlight and air for oxidation, with its viscosity adjusted to 1000 MPa. Below s, aged alkali cellulose is obtained; the aged alkali cellulose is suspended in chloromethane and reacted at 1.5~2MPa and 60~70℃ for more than 5 hours; the obtained product is washed and dried to obtain the modified methyl cellulose. The anionic polyacrylamide has a molecular weight of 3 million to 6 million. The zwitterionic polyacrylamide is prepared by the following steps: 0.8-1.2 parts by weight of anionic polyacrylamide, 8-12 parts by weight of water, and 1.2-1.6 parts by weight of formaldehyde are mixed and stirred at room temperature for 8-12 hours. Then, 0.8-1.2 parts by weight of dimethylamine are added, and the mixture is stirred at 35-45°C for 4-4.5 hours. After cooling to room temperature, 0.3-0.5 parts by weight of dimethyl sulfate are added, and the mixture is stirred for more than 15 hours to obtain the zwitterionic polyacrylamide. The molecular weight of the anionic polyacrylamide used to prepare the zwitterionic polyacrylamide is 8-10 million.

2. The anti-solid phase dispersion cement slurry system according to claim 1, wherein, The particle size of the ultrafine cement is 800 mesh to 1000 mesh.

3. The anti-solid phase dispersion cement slurry system according to claim 1, wherein, The polyethylene sulfonate dispersant includes sodium polyethylene sulfonate.

4. The anti-solid phase dispersion cement slurry system according to claim 1, wherein, The gypsum includes one or a combination of natural gypsum, mixed gypsum, and industrial by-product gypsum.

5. The anti-solid phase dispersion cement slurry system according to any one of claims 1-4, wherein, The viscosity of the anti-solid phase discrete cement slurry system is 10~60 mPa·s.

6. The anti-solid phase dispersion cement slurry system according to any one of claims 1-4, wherein, The density of the anti-solid phase discrete cement slurry system is 1.65~1.95 g / cm³. 3 .

7. The anti-solid phase dispersion cement slurry system according to claim 1, wherein, The anti-solid phase dispersion cement slurry system is prepared through the following steps: (1) By weight, 600-700 parts of G-grade oil well cement, 15-25 parts of ultrafine cement, 0.7-2.1 parts of modified methylcellulose, 0.7-3.5 parts of polyethylene sulfonate dispersant, and 1.4-3.5 parts of gypsum are mixed in a dry mixing process to obtain a dry mixture. (2) Add 0.5 to 1.5 parts of anionic polyacrylamide and 0.02 to 0.05 parts of zwitterionic polyacrylamide to 264 to 476 parts of water, stir evenly, and then add 0 to 0.001 parts of defoamer to obtain an aqueous solution of polyacrylamide. (3) The dry mixture is added to the polyacrylamide aqueous solution and stirred evenly to obtain the anti-solid phase dispersion cement slurry system.

8. A method for preparing a cement slurry system resistant to solid-phase dispersion according to any one of claims 1-7, comprising the following steps: (1) By weight, 600-700 parts of G-grade oil well cement, 15-25 parts of ultrafine cement, 0.7-2.1 parts of modified methylcellulose, 0.7-3.5 parts of polyethylene sulfonate dispersant, and 1.4-3.5 parts of gypsum are mixed in a dry mixing process to obtain a dry mixture. (2) Add 0.5 to 1.5 parts of anionic polyacrylamide and 0.02 to 0.05 parts of zwitterionic polyacrylamide to 264 to 476 parts of water, stir evenly, and then add 0 to 0.001 parts of defoamer to obtain an aqueous solution of polyacrylamide. (3) The dry mixture is added to the polyacrylamide aqueous solution and stirred evenly to obtain the anti-solid phase dispersion cement slurry system.

9. The method for preparing the anti-solid phase dispersion cement slurry system according to claim 8, wherein, Step (2) specifically includes: adding 0.5 to 1.5 parts of anionic polyacrylamide and 0.02 to 0.05 parts of zwitterionic polyacrylamide to water with a stirring speed of 8000 to 12000 rpm within 35 seconds, then reducing the stirring speed to 3000 to 4000 rpm and stirring for more than 15 minutes to obtain a polyacrylamide aqueous solution; or, step (2) specifically includes: adding 0.5 to 1.5 parts of anionic polyacrylamide and 0.02 to 0.05 parts of zwitterionic polyacrylamide to water with a stirring speed of 1000 to 1200 rpm and stirring continuously at a speed of 1000 to 1200 rpm for more than 35 minutes to obtain a polyacrylamide aqueous solution.

10. The method for preparing the anti-solid phase dispersion cement slurry system according to claim 8, wherein, Step (3) specifically includes: adding the dry mix to the polyacrylamide aqueous solution with a stirring speed of 8000~12000 rpm within 35 seconds, then reducing the stirring speed to 3000~4000 rpm, and stirring for more than 25 seconds to obtain the anti-solid phase dispersion cement slurry system; or, step (3) specifically includes: adding the dry mix to the polyacrylamide aqueous solution with a stirring speed of 1000~1200 rpm within 35 seconds, and stirring continuously at a speed of 1000~1200 rpm for more than 1 minute to obtain the anti-solid phase dispersion cement slurry system.

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