阅读说明：本技术 坑井用水泥浆用添加剂及其保管方法、坑井用水泥浆以及坑井用水泥灌浆施工方法 (Additive for well cement slurry, method for storing additive, well cement slurry, and method for constructing well cement slurry ) 是由 村上智 木全政树 太田勇夫 于 2020-04-07 设计创作，主要内容包括：提供在寒冷地带、温暖地带、高温地带的所有环境下都能够抑制从水泥浆的游离水的产生的坑井用水泥浆用添加剂及其保管方法。坑井用水泥浆用添加剂,其包含采用动态光散射法得到的平均粒径3～200nm的二氧化硅的水性分散液、和作为分散稳定剂的具有醇性羟基的化合物,相对于二氧化硅的水性分散液中的分散介质1000g,包含1～30摩尔的该化合物。(Provided are an additive for a cement slurry for a well, which can suppress the generation of free water from the cement slurry in all environments in a cold zone, a warm zone, and a high-temperature zone, and a method for storing the additive. An additive for a well slurry, which comprises an aqueous dispersion of silica having an average particle diameter of 3 to 200nm obtained by a dynamic light scattering method and a compound having an alcoholic hydroxyl group as a dispersion stabilizer, wherein the compound is contained in an amount of 1 to 30 moles per 1000g of a dispersion medium in the aqueous dispersion of silica.)

1. An additive for a well slurry, which comprises an aqueous dispersion of silica having an average particle diameter of 3 to 200nm obtained by a dynamic light scattering method and a compound having an alcoholic hydroxyl group as a dispersion stabilizer, wherein the compound is contained in an amount of 1 to 30 moles per 1000g of a dispersion medium in the aqueous dispersion of silica.

2. The additive for a well cement slurry according to claim 1, wherein the compound is at least 1 alcohol selected from methanol, ethanol, isopropanol, ethylene glycol, diethylene glycol, propylene glycol, and glycerin.

3. The additive for a well cement slurry according to claim 1 or 2, wherein the compound is at least 1 kind of polyhydric alcohol selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol, and glycerin.

4. The additive for a well cement slurry according to any one of claims 1 to 3, wherein the compound is propylene glycol.

5. The additive for a well cement according to any one of claims 1 to 4, wherein when the additive for a well cement is held at-20 ℃ for 48 hours and then the average particle diameter is measured at +20 ℃ by a dynamic light scattering method, the average particle diameter is in the range of 1.0 to 7.0 times the initial average particle diameter before holding.

6. The additive for a well cement according to any one of claims 1 to 4, wherein when the additive for a well cement is held at +50 ℃ for 7 days and then the average particle diameter is measured at +20 ℃ by a dynamic light scattering method, the average particle diameter is in the range of 1.0 to 7.0 times the initial average particle diameter before holding.

7. The method for storing the additive for a well cement slurry according to any one of claims 1 to 6, comprising: and a step of maintaining the additive for a cement slurry for a well in a liquid state at a temperature ranging from-30 ℃ to +60 ℃.

8. The method for storing the additive for a well cement slurry according to any one of claims 1 to 6, comprising: freezing the additive for the cement slurry for the well; and a step of thawing the frozen well cement slurry with an additive and redispersing the same.

9. A well-cementing slurry comprising the additive according to any one of claims 1 to 6, comprising: 0.1-10% BWOC silica, 30-60% BWOC water and 0.03-3.0% BWOC dispersion stabilizer.

10. The grout for well drilling according to claim 9, further comprising 0.1-5% BWOC cement hardening retarder and 0.001-10% BWOC auxiliary agent selected from at least 1 of dehydration regulator, defoamer, quick hardening agent, cement dispersant, cement strength stabilizer and mud leakage preventive.

11. A method of cementing a well, characterized in that the well cement slurry according to claim 9 or 10 is injected into the gap between the casing inserted into the well and the ground layer and hardened during the excavation of the well.

Technical Field

The present invention relates to an additive for a cement slurry for a well, a method for storing the additive, a cement slurry for a well, and a method for cement grouting for a well.

Background

Among cement grout slurries used for well excavation of oil fields and gas field sites in cold regions such as north america and northern europe, there is a high demand for cement grout slurries that suppress the generation of free water and achieve excellent fluidity and strength, and additives for cement grout that meet the demand are required. Further, in high temperature zones such as the middle and near east, there is a high demand for cement grout for suppressing the generation of free water and achieving excellent fluidity and strength, and additives for cement grout satisfying the demand are required. The desire for a global additive for cement paste that can be used in both cold and hot zones is rising compared to an additive for cement paste that needs to be used separately in cold and hot zones.

The term "cement paste" refers to cement paste prepared by applying water containing cement, water or additives dissolved therein or outside the casing at various locations in a pit or well.

In cement slurry for grouting, as an additive for suppressing free water from the slurry, there has been proposed a method of using a polymer having a particle diameter of about 3 to 20nm, such as an aqueous silica sol, an ABS resin (acrylonitrile-butadiene-styrene copolymer resin), and an ASA resin (acrylonitrile-styrene-acrylate copolymer resin).

For example, patent document 1 discloses that, as a proposal for suppressing the generation of free water from cement paste by adding colloidal silica (silica sol), the addition of a specific surface area of about 50m to the dry weight of cement is performed at a ratio of about 1 to about 30%²/g～1000m²Cement slurry of colloidal silica in g. Discloses the slurry after conditioning (curing) at a specified temperature at 25-91 DEG C0 to 3.2 percent of free water.

Patent document 2 discloses a hydraulic binder, water and a composition containing 0.05 to 3 wt% of Al₂O₃The aluminum-modified colloidal silica of (1) a building material (road, tunnel, bridge, building, cement fixation in a pit, etc.). The document discloses that the specific surface area of the polymer is 80 to 900m²The aluminum modified colloidal silica cement slurry/g is a slurry with good fluidity with essentially zero free water (however, no temperature conditions are disclosed).

In addition, non-patent document 1 describes that the number of cases of horizontally excavating the pay zone is increasing, and as measures for improving the efficiency of replacement of excavation mud water and cement slurry at the time of horizontally excavating the pay zone and for reducing material separation (including free liquid) in the slurry, addition of cement of grade G having a particle size of 0.05 μm and a specific surface area of 500m to cement of grade G is described²The actual construction was carried out on a horizontal portion (length: about 1500m) of colloidal silica (specific gravity of cement slurry: 1.89)/g.

Regarding redispersibility of an aqueous silica sol after freezing and thawing, patent document 3 discloses that a silica sol to which a glycol such as monoethylene glycol or a primary, secondary or tertiary amine is added as an anti-freezing agent of the silica sol (particularly, a silica sol) is more stable after several freeze-thaw tests.

Patent document 4 discloses an aqueous dispersion of silica-based inorganic oxide fine particles, which is an aqueous dispersion containing silica-based inorganic oxide fine particles having an average particle diameter of 1 to 500nm and 1 or more kinds of alcohols selected from methanol, ethanol and isopropanol, wherein the alcohol concentration is in the range of 0.5 to 8% by weight, and the solid content concentration of the silica-based inorganic oxide fine particles contained in the aqueous dispersion is in the range of 0.001 to 60% by weight. In examples 1 to 3, silica sols containing silica fine particles (average particle diameter 10.6nm, SiO)₂Concentration 30.3 wt%, dispersion medium: water) 40g of an aqueous dispersion of silica fine particles containing 3 wt% of ethanol, frozen at-2 ℃ and then thawed at room temperature, the silica fine particles were easily dispersed, and an aqueous dispersion having an average particle diameter substantially the same as that before freezing was obtainedDisclosed is an aqueous dispersion of silica-based inorganic oxide fine particles having excellent redispersibility in freeze-thaw.

As described above, when a polymer such as an ABS resin or an ASA resin is used to suppress the generation of free water from cement slurry for cement grouting, the temperature is often significantly lower than the freezing point in oil fields and gas field sites located in cold regions such as north america and northern europe, and for example, the polymer is vitrified and embrittled during transportation and storage in a cold region environment of-5 to 20 ℃. Therefore, there is a possibility that the effect of suppressing the generation of free water from the cement paste for cement grouting may be significantly reduced.

In addition, in patent document 2 and non-patent document 1, it is easily presumed that both aqueous silica sols are used, and for example, in a cold region environment of-2 to 20 ℃ or lower, the silica sols are frozen during transportation and storage, and even when thawed, the silica sols are greatly aggregated, so that there is a possibility that the effect of suppressing the generation of free water from the cement slurry for cement grouting is almost completely lost.

Therefore, in order to prevent freezing of the aqueous silica sol, it is considered to add a dispersion stabilizer having a freezing point depression function.

The freezing point depression temperature after adding a dispersion stabilizer having a freezing point depression function to water can be determined from the molecular weight and the molar mass concentration of the dispersion stabilizer based on a formula relating the molar mass concentration of the dispersion stabilizer to the freezing point depression for 1000g of water.

Calcium chloride, sodium chloride and urea, which are relatively inexpensive, are widely used as a dispersion stabilizer having a freezing point depression function of water, and addition of these to an aqueous silica sol causes aggregation and gelation of the silica sol, and is therefore not preferable as a dispersion stabilizer for an aqueous silica sol.

Therefore, there has been no disclosure of using a non-freezing silica sol in which a dispersion stabilizer having a freezing point depression function is added to an aqueous silica sol to suppress generation of free water in a cement paste used for grouting.

Further, the anti-freezing silica sol described in patent document 4 is an aqueous silica sol having good redispersibility after freezing and thawing, and is used for dental technicians, and its application is different. Patent document 5 does not describe the use of an aqueous dispersion of silica-based inorganic oxide fine particles for suppressing the generation of free water in cement paste used for cement grouting.

Patent document 5 describes a method of adding ethylene glycol to water glass for ground injection, and also describes that this method has disadvantages of gelation, slow reaction thereafter, and shrinkage after construction. Therefore, patent document 5 describes a main hindrance to the addition of ethylene glycol to the cement for a well.

A cementing method comprising adding an additive for a cement slurry for a well to an aqueous silica sol containing a dispersion stabilizer which stably disperses silica particles having an average particle diameter of 3 to 200nm at-30 ℃ to +60 ℃, wherein a cementing operation for fixing, reinforcing and preventing corrosion of a casing inserted as an inner frame in the well and for injecting a cement slurry into a gap (annular gap: also referred to as "annulas (annular)) between the casing and a ground layer (well wall) in the well during well finishing is performed in well excavation in an oil field, a gas field or the like in a cold region.

In the case of well excavation in an oil field, a gas field, or the like, excavation work using a drill (drilling tool) and the above-described cementing work are repeatedly performed, and as the oil well becomes deeper, the temperature and pressure at the work site increase. In recent years, the frequency of horizontal wells has increased, which can increase the production capacity by horizontally driving the production zone of an oil field or a gas field. Unlike conventional vertical wells and inclined wells, horizontal wells require attention to the properties of muddy water during excavation and the design of cement slurry used for grouting.

The cement slurry for cement grouting is designed according to the well conditions, and is prepared by adding additives such as a cement quick hardening agent, a cement slow hardening agent, a low specific gravity aggregate, a high specific gravity aggregate, a cement dispersant, a cement dehydration regulator, a cement strength stabilizer, a mud leakage preventing agent and the like in addition to cement and water.

Further, pit cement (also referred to as oil well cement, geothermal well cement, or the like) used for cementing has required performance different from that of cement for general structures, and for example, workability such as slurry fluidity and strength development property and durability are required even under high temperature and high pressure.

As a standard considering such required performance, various oil well cements are classified into classes of grades and sulfate resistance classes in API standards (standards for Petroleum established by American Petroleum Institute), and among them, class G cement is the cement most commonly used as cement for oil well excavation.

Documents of the prior art

Patent document

Patent document 1: specification of U.S. Pat. No. 5149370

Patent document 2: japanese patent No. 4146719

Patent document 3: japanese laid-open patent publication No. 2-9707

Patent document 4: japanese patent No. 5693187

Patent document 5: japanese laid-open patent publication No. 59-179579

Non-patent document

Non-patent document 1: journal of the Society of organic Materials, volume Japan 14, 2007, page 464

Disclosure of Invention

Problems to be solved by the invention

However, even if the API standard described above is satisfied, the amount of free water generated from the cement slurry increases in the cold zone environment, and as a result, the fluidity of the cement slurry and the strength of the cement are impaired, and a method capable of suppressing the generation of free water in the above-described well environment is required.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an additive for a cement slurry for a well, which is used in, for example, a cement slurry for cementing (for a well) in an oil field or a gas field, and which can suppress the generation of free water from the cement slurry in all environments such as a cold zone, a warm zone, and a high temperature zone, and a method for storing the additive for a cement slurry for a well. Another object of the present invention is to provide a cement slurry for a well, which contains the above additive.

Another object of the present invention is to provide a method for cementing a well using the above-mentioned cement slurry for a well.

Means for solving the problems

The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that: an additive which is a composition containing an aqueous dispersion of silica and containing a specific amount of a compound having an alcoholic hydroxyl group as a dispersion stabilizer with respect to a dispersion medium in the aqueous dispersion of silica, more preferably a composition produced under specific conditions and/or containing these under specific conditions, can be suitably used as an additive for a cement slurry for a well; further, the present inventors have found that by including the additive in a well cement slurry, the amount of free water generated from the cement slurry can be suppressed in any environment of a cold zone, a warm zone, or a high temperature zone, and excellent dispersibility, fluidity, and cement strength can be obtained, and have completed the present invention.

That is, the gist of the present invention is as follows.

[ 1 ] an additive for a well slurry, which comprises an aqueous dispersion of silica having an average particle diameter of 3 to 200nm obtained by a dynamic light scattering method and a compound having an alcoholic hydroxyl group as a dispersion stabilizer, wherein the compound is contained in an amount of 1 to 30 mol per 1000g of a dispersion medium in the aqueous dispersion of silica.

< 2 > the additive for a well cement slurry according to < 1 >, wherein the compound is at least 1 alcohol selected from the group consisting of methanol, ethanol, isopropanol, ethylene glycol, diethylene glycol, propylene glycol, and glycerin.

< 3 > the additive for a well cement slurry according to < 1 > or < 2 > wherein the compound is at least 1 polyol selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol, and glycerin.

< 4 > the additive for a well cement slurry according to any one of < 1 > to < 3 >, wherein the compound is propylene glycol.

< 5 > the additive for a well cement according to any one of < 1 > to < 4 >, wherein when the additive for a well cement is held at-20 ℃ for 48 hours and then the average particle diameter is measured at +20 ℃ by a dynamic light scattering method, the average particle diameter is in the range of 1.0 to 7.0 times the initial average particle diameter before holding.

< 6 > the additive for a well cement according to any one of < 1 > to < 4 >, wherein when the additive for a well cement is held at +50 ℃ for 7 days and then the average particle diameter is measured at +20 ℃ by a dynamic light scattering method, the average particle diameter is in the range of 1.0 to 7.0 times the initial average particle diameter before holding.

< 7 > the method for storing an additive for a well cement slurry according to any one of < 1 > to < 6 >, comprising: and a step of maintaining the additive for a cement slurry for a well in a liquid state at a temperature ranging from-30 ℃ to +60 ℃.

< 8 > the method for storing an additive for a well cement slurry according to any one of < 1 > to < 6 >, comprising: freezing the additive for the cement slurry for the well; and a step of thawing the frozen well cement slurry with an additive and redispersing the same.

< 9 > a well cement slurry, which is a well cement slurry containing the additive according to any one of < 1 > to < 6 > and which comprises: 0.1-10% BWOC silica, 30-60% BWOC water and 0.03-3.0% BWOC dispersion stabilizer.

< 10 > the cement slurry for a well according to < 9 >, further comprising 0.1-5% BWOC of a cement hardening retarder and 0.001-10% BWOC of at least 1 additive selected from the group consisting of a dehydration modifier, an antifoaming agent, a hardening accelerator, a cement dispersant, a cement strength stabilizer and a mud leakage preventive.

The cement grouting construction method for a well is characterized in that the cement slurry for a well is injected into a gap between a casing inserted into the well and a ground layer during the excavation of the well, and is hardened according to the formula < 9 > to < 10 >.

Effects of the invention

The additive for a well slurry of the present invention has a dispersion stabilizer for stably dispersing silica particles added to an aqueous silica sol, and therefore, does not freeze even in a cold region under a low temperature condition of-30 ℃ or has good redispersibility when thawed even if frozen. Therefore, the cement slurry containing the additive for well cement slurry of the present invention can suppress the generation of free water from the cement slurry, has excellent fluidity, realizes high cement strength, and can suppress insufficient construction (for example, the cement is thin and does not fill a gap with a ground layer, and the fixation of a casing becomes insufficient). In addition, the additive for a cement slurry for a well according to the present invention is stable even in a warm zone of 20 to 25 ℃ and further in a high temperature zone of 60 ℃, and therefore, a cement slurry containing the additive can suppress the generation of free water from the cement slurry, and can realize high cement strength while having excellent fluidity.

Therefore, the additive for a well cement slurry of the present invention can be added to a cement slurry in all environments of a cold zone, a warm zone, and a high temperature zone, thereby stably and highly productively performing well finishing.

Detailed Description

Preferred embodiments of the present invention will be described below. However, the following embodiments are illustrative for explaining the present invention, and the present invention is by no means limited to the following embodiments.

In the present specification, the numerical range expressed by the term "to" means a range including numerical values described before and after the term "to" as a lower limit value and an upper limit value.

Additive for cement slurry for well

The additive for a slurry for a well of the present invention comprises an aqueous dispersion of silica having an average particle diameter (hereinafter, sometimes referred to as DLS particle diameter) of 3 to 200nm obtained by a dynamic light scattering method (DLS method), and contains a compound having an alcoholic hydroxyl group as a dispersion stabilizer. Since the dispersion stabilizer which stably disperses the silica particles is added to the aqueous silica sol as described above, a dispersion having good dispersibility can be obtained, for example, even when stored at a temperature below the freezing point, or even when frozen temporarily and then thawed, as shown in examples described later. In particular, as to whether or not the dispersion is good even after the temporary freezing and when the dispersion is thawed, for example, if the DLS particle diameter of the dispersoid redispersed after thawing is preferably 7.0 times or less, more preferably 1.5 times or less the DLS particle diameter before freezing, it can be judged that the dispersion is good even when the dispersoid is thawed after the temporary freezing.

In one embodiment of the present invention, the additive for a well cement slurry is held at-20 ℃ for 48 hours, and then the average particle diameter measured at +20 ℃ by a dynamic light scattering method is in the range of 1.0 to 7.0 times the initial average particle diameter obtained by the dynamic light scattering method before holding.

In one embodiment of the present invention, the average particle size of the additive for a well cement slurry, measured at 20 ℃ after being held at +50 ℃ for 7 days, by the dynamic light scattering method is in the range of 1.0 to 7.0 times the initial average particle size before holding by the dynamic light scattering method.

In one embodiment of the present invention, the compound having an alcoholic hydroxyl group as a dispersion stabilizer is contained in an amount of 1 to 30 moles per 1000g of a dispersion medium (water) in the aqueous silica dispersion.

The lower limit of the range of the content of the compound with respect to 1000g of the dispersion medium is preferably 1 mol, more preferably 5 mol, and still more preferably 10 mol, and the upper limit of the range of the content of the compound with respect to 1000g of the dispersion medium is preferably 30 mol, more preferably 25 mol, and still more preferably 20 mol.

If the content of the compound with respect to 1000g of the dispersion medium is not less than the lower limit, the additive for cement paste is once frozen at-10 ℃ to-30 ℃ and then thawed, the redispersibility of the silica sol is also good, and the generation of free water from the cement paste can be suppressed, so that it is preferable that the content of the compound with respect to 1000g of the dispersion medium is not more than the upper limit, since the effect thereof can be secured, the amount of the dispersion stabilizer to be added can be suppressed, and the cost can be reduced, and thus it is preferable.

(silica)

As the aqueous silica sol used in the present invention, a commercially available aqueous silica sol can be used. Further, Silica (SiO) in the aqueous silica sol used₂) The concentration is not particularly limited, and may be, for example, 5 to 55 mass%. Examples of commercially available alkaline aqueous silica sols include SNOWTEX (registered trademark) ST-XS, SNOWTEX ST-S, SNOWTEX ST-30, SNOWTEX ST-M30, SNOWTEX ST-20L, SNOWTEX ST-YL, and SNOWTEX ST-ZL (manufactured by Nissan chemical Co., Ltd.), and examples of acidic aqueous silica sols include SNOWTEX (registered trademark) SNOWTEX ST-OXS, SNOWTEX ST-OS, SNOWTEX ST-O-40, SNOWTEX ST-OL, SNOWTEX ST-OYL, and SNOWTEX ST-OZL-35 (manufactured by Nissan chemical Co., Ltd.).

In the present invention, the average particle diameter of the aqueous silica sol (colloidal silica particles) can be determined from the average particle diameter obtained by a dynamic light scattering method (DLS method).

The DLS particle size represents an average value of 2-order particle sizes (dispersion particle sizes), and it is reported that the DLS particle size in a completely dispersed state is about 2 times as large as an average particle size (a specific surface area diameter measured by a nitrogen adsorption method (BET method), representing an average value of 1-order particle sizes). Further, the larger the DLS particle diameter, the more the silica particles in the aqueous silica sol are aggregated.

The average particle diameter of the aqueous silica sol is preferably 3 to 200 nm. When the particle diameter is smaller than 3nm, the stability of the aqueous silica sol may be deteriorated. If the silica sol is larger than 200nm, the generation of free water in the slurry may not be suppressed without adding a large amount of the aqueous silica sol, and the cost may be increased.

The silica particle size of the aqueous silica sol can also be determined from the specific surface area diameter measured by the nitrogen adsorption method (BET method) or the Sears method particle size.

Specific surface area diameter (average particle diameter (specific surface area diameter) D (nm)) measured by Nitrogen adsorption method (BET method) and specific surface area S (m) measured by Nitrogen adsorption method²And/g) was obtained from the formula of d (nm) 2720/S.

The Sears method particle size is based on the literature: "average particle diameter as measured by the Siro- な (1986) at page 1981, anal. chem.28, コロイダルシリカ, particle diameter of G.W. Sears. Specifically, it is prepared from SiO 1.5g₂The specific surface area of the colloidal silica was determined from the amount of 0.1N-NaOH required for titration from pH4 to pH9, and the equivalent diameter (specific surface area diameter) was calculated from the specific surface area.

(Dispersion stabilizer)

As the dispersion stabilizer used in the present invention, a compound having an alcoholic hydroxyl group can be used.

In one embodiment of the present invention, the compound having an alcoholic hydroxyl group as the dispersion stabilizer includes at least 1 alcohol selected from methanol, ethanol, isopropanol, ethylene glycol, diethylene glycol, propylene glycol, and glycerin. Among them, at least 1 kind of polyhydric alcohol selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol and glycerin is preferable, and among them, propylene glycol having low toxicity to a human body and high environmental safety is particularly preferable.

Further, since a polyhydric alcohol such as propylene glycol has a boiling point of 180 to 300 ℃ and a boiling point higher than that of methanol, for example, a cement paste using an additive containing a polyhydric alcohol such as propylene glycol as a dispersion stabilizer instead of methanol is advantageous in that, for example, generation of voids in cement due to heating and vaporization at an underground temperature can be suppressed, and further, reduction in the strength of hardened cement can be suppressed.

In one embodiment of the present invention, as the dispersion stabilizer, a dispersion stabilizer having a freezing point depression function can be preferably used. As the dispersion stabilizer having the freezing point depressing function, in addition to the above-mentioned compounds, water-soluble primary amine, secondary amine, and tertiary amine can be used.

In one embodiment of the present invention, the dispersion stabilizer brings about the following advantages: even when the additive for a well slurry of the present invention is stored in an environment at a temperature ranging from-30 ℃ to +60 ℃ or in an environment at a temperature ranging from-20 ℃ to +50 ℃, the silica particles can be dispersed in the dispersion medium, or can be redispersed in the dispersion medium by freezing and then thawing, and a uniform and good dispersion liquid having extremely excellent storage stability can be obtained.

Method for storing additive for cement slurry for well

In one embodiment of the present invention, a method for storing an additive for a well cement slurry includes a step of maintaining the additive in a liquid state at a temperature ranging from-30 ℃ to +60 ℃.

In one embodiment of the present invention, a method for storing an additive for a well cement slurry includes a step of maintaining the additive in a liquid state at a temperature ranging from-20 ℃ to +50 ℃.

The storage period in the above temperature range is preferably 6 months, more preferably 3 months, further preferably 2 months, and most preferably 1 month.

In one embodiment of the present invention, the present invention includes: freezing the slurry for the well with an additive; and a step of thawing the frozen well cement slurry with an additive and redispersing the same.

As described above, according to the embodiment of the present invention, even when the additive of the present invention is stored in the above-described wide temperature range for a predetermined storage period, as described above, the synergistic effect between the specific dispersion stabilizer used in the present invention and the specific silica particles brings about the following advantages: the additive for a cement slurry for a well bore, which can disperse silica particles in a dispersion medium or can redisperse silica particles in a dispersion medium by freezing the silica particles once and then thawing the frozen silica particles, has excellent storage stability and can be stored and stored uniformly and satisfactorily for a long period of time, is provided.

< cement paste for well >

The slurry for a well of the present invention contains, as an additive, a composition containing an aqueous dispersion of silica having a predetermined average particle diameter and a compound having an alcoholic hydroxyl group as a dispersion stabilizer. As shown in examples described later, by including an aqueous dispersion containing both an aqueous dispersion of silica having a predetermined average particle diameter and a compound having an alcoholic hydroxyl group as a dispersion stabilizer as essential components in a cement slurry as an additive for a well cement slurry, the cement slurry can be stored and stored for a long period of time with good storage stability in a temperature range from below the freezing point to a relatively high temperature, and also has an advantage that generation of free water from the cement slurry can be suppressed.

In one embodiment of the present invention, the well cement slurry is a slurry containing the additive for a well cement slurry according to any one of the embodiments of the present invention, and contains cement such as oil well cement, and further contains 0.1% to 10% BWOC of silica, 30% to 60% BWOC of water, and 0.03% to 3.0% BWOC of a dispersion stabilizer with respect to the cement. The term "% BWOC" as used herein means the mass% of dry solid content based on Cement (By Weight of Cement), and is a matter of art well known to those skilled in the art.

In one embodiment of the present invention, a well cement slurry is a slurry further containing an additive for a well cement slurry according to any one of the embodiments of the present invention, and contains cement such as oil well cement, and further contains 0.1% to 10% BWOC of silica, 30% to 60% BWOC of water, and 0.03% to 3.0% BWOC of a dispersion stabilizer with respect to the cement.

The lower limit of the range of the content ratio of the silica solid component is preferably 0.1% BWOC, more preferably 0.15% BWOC, and still more preferably 0.2% BWOC, and the upper limit of the range of the content ratio of the silica solid component is preferably 10% BWOC, more preferably 1% BWOC, and still more preferably 0.5% BWOC.

If the content ratio of the silica solid component is equal to or greater than the lower limit, it is possible to suppress an excessive decrease in the viscosity of the cement slurry and to suppress the generation amount of the free water (free water), and therefore it is preferable, and if the content ratio of the silica solid component is equal to or less than the upper limit, it is possible to suppress a significant excessive increase in the viscosity of the cement slurry during preparation, and it is possible to charge a predetermined amount of cement without trouble, and therefore it is preferable.

The lower limit of the range of the content ratio of the dispersion stabilizer is preferably 0.03% BWOC, more preferably 0.04% BWOC, and still more preferably 0.1% BWOC, and the upper limit of the range of the content ratio of the dispersion stabilizer is preferably 3.0% BWOC, more preferably 1% BWOC, and still more preferably 0.5% BWOC.

If the content ratio of the dispersion stabilizer is not less than the lower limit, the redispersibility of the silica sol is good even when the additive for cement paste is temporarily frozen and then thawed at-10 ℃ to-30 ℃, and the generation of free water from the cement paste can be suppressed, so that it is preferable, and if the content ratio of the dispersion stabilizer is not more than the upper limit, the addition amount of the dispersion stabilizer can be suppressed while ensuring the effects thereof, and the cost can be reduced, so that it is preferable.

The slurry for a well of the present invention may contain 30 to 60% BWOC water, and fresh water, tap water, industrial water, pure water, seawater, or the like may be suitably used as the water to be used.

(other Inclusion substances)

The well cement slurry of the present invention may contain other additives in addition to the above-mentioned oil well cement and well cement slurry additives and water.

As the oil Well cement, grade A to grade H Cements of API (American Petroleum institute) Standard "APISPEC 10A specifications for centers and Materials for Well" can be used. Among these, the G-class cement and the H-class cement are more preferable because they can be used in a wide range of depths and temperatures because they can be easily adjusted in composition by using additives or auxiliaries.

The cement hardening retarder is used for adjusting the thickening time while maintaining proper fluidity of the cement slurry until the completion of the work.

The cement hardening retarder includes, as main components, lignosulfonates, naphthalenesulfonates, borates, and the like.

In addition, as other additives, at least 1 kind of additives selected from the group consisting of dehydration regulators, antifoaming agents, low specific gravity aggregates, high specific gravity aggregates, cement quick-hardening agents, cement dispersants, cement strength stabilizers, and mud leakage preventing agents can be contained.

The dehydration regulator can be used for the purpose of protecting a water-sensitive formation and preventing early dehydration of a slurry, and includes an organic high molecular polymer, a vinylamide-vinylsulfonic acid copolymer, and the like as a main component.

The defoaming agent contains a silicon compound, a higher alcohol, and the like as main components.

The low specific gravity aggregate can be used for the purpose of reducing the specific gravity of cement paste or the like when it has a water leakage layer or a low pressure layer, and includes bentonite, natural asphalt, diatomaceous earth, pearlite, hollow pearlite hollow particles, fly ash hollow particles, alumina silicate glass hollow particles, sodium borosilicate hollow particles, alumina hollow particles, carbon hollow particles, or the like as a main component.

The high specific gravity aggregate can be used for the purpose of improving the specific gravity of the cement slurry or the like in order to improve the replacement efficiency with the high-pressure formation suppression muddy water, and contains barium sulfate, hematite, ilmenite or the like as a main component.

The cement quick-hardening agent is used for the purpose of shortening initial strength and hardening waiting time, and includes calcium chloride, water glass, gypsum, and the like as a main component.

The cement dispersant can be used for the purpose of reducing the viscosity of cement paste, improving the replacement efficiency with muddy water, and the like, and contains a naphthalenesulfonic acid formalin condensate, a polyacrylic acid condensate, a sulfonated melamine condensate, or the like as a main component.

The cement strength stabilizer includes fly ash, silica powder, and the like as main components.

The anti-cement leakage agent is used for preventing water leakage, and includes inactive granular components that do not affect the properties of cement, and includes walnut shells, mountain stones, natural asphalt, mica, and cellophane waste as a main component.

The cement slurry for a well of the present invention may contain, in addition to the above-mentioned cement such as oil well cement, the additive for a cement slurry for a well of any of the embodiments of the present invention, a cement hardening retarder, and other additives or auxiliary agents, various cements used in general structural cement compositions and concrete compositions, aggregates, and other additives used in these cement compositions.

For example, portland cement (e.g., ordinary portland cement, high-early-strength portland cement, super-high-early-strength portland cement, low-heat/medium-heat portland cement, sulfate-resistant portland cement, etc.), various mixed cements (blast furnace cement, silica cement, fly ash cement, etc.), white portland cement, alumina cement, super-high-speed hard cement (1 clinker fast-hardening cement, 2 clinker fast-hardening cement, magnesium phosphate cement), cement for grouting, low-heat cement (low-heat blast furnace cement, fly ash mixed low-heat blast furnace cement, high belite cement), ultrahigh-strength cement, cement-based curing material, ecological cement (cement produced by using at least one of municipal refuse incineration ash and slag sludge incineration ash as a raw material), etc. can be used as the cement for general structures that has been conventionally used conventionally, and blast furnace cement can be added as the mixing material, Micropowder such as fly ash, cinder ash, clinker ash, rice hull ash, silica fume, silica powder, limestone powder, etc., and gypsum.

As the aggregate, in addition to gravel, crushed stone, crushed slag, recycled aggregate, etc., a refractory aggregate such as silica, clay, zircon, high alumina, silicon carbide, graphite, chromium magnesium, magnesium oxide, etc. can be used.

As other additives used in cement compositions and the like, known cement/concrete additives such as a high-performance AE water reducing agent, a high-performance water reducing agent, an AE water reducing agent, a water reducing agent, an air entraining agent (AE agent), a foaming agent, a separation reducing agent, a thickener, a shrinkage reducing agent, a curing agent, and a water repellent agent can be blended.

Cement grouting construction method for pit

In one embodiment of the present invention, a method of cementing a well is a method of using a well cement slurry according to any one of the aspects of the present invention, wherein the well cement slurry is injected into a gap between a casing inserted into the well and a ground layer and hardened.

In one embodiment of the present invention, the method of cementing a well is used for filling a gap between a ground formation and a casing with oil-well cement in excavation of an oil field or a gas-oil field in a cold region, and can suppress generation of free water from the cement slurry by using the well-cementing slurry according to any one of the embodiments of the present invention.

Examples

The present invention will be described in more detail below based on preparation examples, and comparative examples of additives for a cement slurry for a well, but the present invention is by no means limited by these examples.

(measuring apparatus, method)

Analysis of the additive for cement slurry (silica solid content concentration, pH, conductivity, DLS particle size, viscosity) was performed using the following apparatus.

Silica solid content concentration: the silica solid content was calculated from the amount of commercially available aqueous silica sol having a known silica solid content and a dispersion stabilizer having a freezing point depressing function.

pH: a pH meter (manufactured by east asia DKK (strain)) was used.

Electrical conductivity: a conductivity meter (manufactured by east asia DKK (strain)) was used.

Viscosity: a B-type viscometer (manufactured by tokyo counter, ltd.) was used.

DLS particle size (dynamic light scattering method particle size): a Zetasizer Nano (manufactured by マルバーン, manufactured by スペクトリス K.K.) was used as a particle size measuring apparatus by a dynamic light scattering method.

< preparation of additive for Cement paste >

< additive for cement paste A >

A magnetic stirrer was placed in a 300ml styrene bottle, and SNOWTEX (registered trademark) ST-S (pH 10.1, SiO) as a commercially available aqueous silica sol was placed therein₂30.5% by mass of a solution having a concentration of 4280. mu.S/cm, 10.2 mPas in viscosity, 15.3nm in diameter of DLS, manufactured by Nissan Kagaku Kogyo Co., Ltd.) of 286g was added to the solution, and the mixture was magnetically stirred14.7g of propylene glycol (manufactured by Kanto chemical Co., Ltd.) as a dispersion stabilizer having a freezing point depressing function was added thereto while stirring with a stirrer, and stirred for 30 minutes to prepare an additive A for cement paste (pH 9.9, conductivity 3180. mu.S/cm, SiO)₂The concentration was 29.0 mass%, the propylene glycol concentration was 4.6 mass%, the viscosity was 11.2mPa · s, and the DLS particle diameter was 16.3 nm). The amount of the dispersion stabilizer added at this time corresponds to 1.0 mol based on 1000g of water contained in the aqueous silica sol.

< additive for cement paste B >

The same operation was carried out except that SNOWTEX (registered trademark) ST-S270.0 g, which is a commercially available aqueous silica sol, and propylene glycol (manufactured by kanto chemical corporation) 30.0g, which is a dispersion stabilizer having a freezing point depression function, were added to prepare an additive B for cement paste (pH 10.1, conductivity 2230 μ S/cm, SiO) in which₂The concentration was 27.5 mass%, the propylene glycol concentration was 9.6 mass%, the viscosity was 12.2mPa · s, and the DLS particle diameter was 16.8 nm). The amount of the dispersion stabilizer added at this time corresponds to 2.0 mol based on 1000g of water contained in the aqueous silica sol.

< additive for cement paste C >

An additive C for cement paste (pH 10.5, conductivity 308 μ S/cm, SiO) was prepared in the same manner as in the case of the additive C for cement paste (pH 308.5, manufactured by kanto chemical corporation) except that SNOWTEX (registered trademark) ST-S174.9 g, which is a commercially available aqueous silica sol, and 125.1g of propylene glycol (manufactured by kanto chemical corporation), which is a dispersion stabilizer having a freezing point depressing function, were added to the mixture₂The concentration was 19.3 mass%, the propylene glycol concentration was 41.3 mass%, the viscosity was 19.0mPa · s, and the DLS particle diameter was 18.9 nm). The amount of the dispersion stabilizer added at this time corresponds to 13.5 moles per 1000g of water contained in the aqueous silica sol.

< additive for Cement slurry D (comparative example) >

In addition to SNOWTEX (registered trademark) ST-S293.7 g as a commercially available aqueous silica sol and propylene glycol (manufactured by Kanto chemical Co., Ltd.) 6 as a dispersion stabilizer having a freezing point depressing functionThe same operation was carried out except for 3g to prepare an additive D for cement paste (pH 9.9, conductivity 3680 μ S/cm, SiO)₂The concentration was 29.8 mass%, the propylene glycol concentration was 2.1 mass%, the viscosity was 11.2mPa · s, and the DLS particle diameter was 16.8 nm). The amount of the dispersion stabilizer added at this time corresponds to 0.4 mol based on 1000g of water contained in the aqueous silica sol.

< additive for cement paste E >

A magnetic stirrer was placed in a 300ml styrene bottle, and SNOWTEX (registered trademark) ST-S (pH 10.1, conductivity 3700. mu.S/cm, SiO) as a commercially available aqueous silica sol was placed therein₂293.7g of a dispersion stabilizer having a concentration of 30.5% by mass, a viscosity of 10.2 mPas and a DLS particle diameter of 15.3nm manufactured by Nikkiso Kagaku K.K., was added with 6.3g of methanol (manufactured by Kanto chemical Co., Ltd.) as a dispersion stabilizer having a freezing point depressing function while stirring with a magnetic stirrer, and the mixture was stirred for 30 minutes to prepare an additive E (pH 9.9, SiO) for cement paste₂The concentration was 29.8 mass%, the methanol concentration was 2.1 mass%, the viscosity was 10.8mPa · s, and the DLS particle diameter was 15.1 nm). The amount of the dispersion stabilizer added at this time corresponds to 1.0 mol based on 1000g of water contained in the aqueous silica sol.

< additive for cement paste F >

An additive F (pH 10.0, conductivity 3190 μ S/cm, SiO) for a cement slurry was prepared in the same manner as in the case of adding SNOWTEX (registered trademark) ST-S286.05 g as a commercially available aqueous silica sol and 13.5g of methanol (manufactured by kanto chemical corporation) as a dispersion stabilizer having a freezing point depressing function₂The concentration was 29.0 mass%, the methanol concentration was 4.5 mass%, the viscosity was 11.3mPa · s, and the DLS particle diameter was 16.7 nm). The amount of the dispersion stabilizer added at this time corresponds to 2.0 mol based on 1000g of water contained in the aqueous silica sol.

< additive G for cement paste >

Except that SNOWTEX (registered trademark) ST-S230.4 g as a commercially available aqueous silica sol was added as dispersion stabilizer having a freezing point depression functionThe same operation was carried out except for 69.6G of methanol (manufactured by Kanto chemical Co., Ltd.) as an additive G for cement paste (pH 10.4, conductivity 1260. mu.S/cm, SiO)₂The concentration was 23.4 mass%, the methanol concentration was 23.2 mass%, the viscosity was 18.0mPa · s, and the DLS particle diameter was 17.6 nm). The amount of the dispersion stabilizer added at this time corresponds to 13.5 moles per 1000g of water contained in the aqueous silica sol.

As described later, the additives A to C for cement paste and E to G and D were used in examples 1 to 3, examples 4 to 6 and comparative example 2, respectively. Further, an additive for cement paste, which was prepared by adding only SNOWTEX (registered trademark) ST-S without adding a dispersion stabilizer having a freezing point depressing function, was used as comparative example 1. The additive components for each cement slurry are shown in table 1.

< storage at Low or high temperature and measurement of physical Properties of additive for Cement paste >

For low-temperature storage, 100g of additives A to F for cement paste were put into a propylene container (volume 100ml) with a screw cap, the container was covered with a cap, and the container was stored in a low-temperature incubator at-20 ℃ for 48 hours. Then, the slurry was taken out, the appearance of the additive for cement slurry was observed, and the slurry was returned to normal temperature without freezing, and then the pH value, conductivity, DLS particle diameter and viscosity were measured. After thawing the frozen sample in a thermostatic bath at +25 ℃, the pH, conductivity, DLS particle size and viscosity were measured.

For high-temperature storage, 100g of additives A to F for cement paste were put into a propylene container (volume: 100ml) with a screw cap, and the container was covered with the cap and kept at +50 ℃ for 7 days. Then, the slurry was taken out, the appearance of the additive for cement slurry was observed, and after returning to normal temperature, the pH value, conductivity, DLS particle diameter, and viscosity were measured.

The measurement results are shown in table 2.

The redispersibility of the additive for cement paste stored at low temperature or high temperature was determined by calculating the ratio of DLS particle diameter after storage at low temperature or high temperature to DLS particle diameter before starting storage, and determining the ratio as described below.

Very good: DLS particle diameter ratio of 1.0 or more and less than 1.2, and excellent redispersibility

Good: DLS particle diameter ratio of 1.2 to 1.5, good redispersibility

And (delta): the DLS particle size ratio is 1.6 to 7.0, and the redispersibility is general

X: white particles are produced in large amounts and sedimentation is severe, so redispersibility is very poor

< preparation of Cement paste >

For the preparation of the cement slurry, it was carried out according to API Standard (standards for oil, established by the American Petroleum institute) 10B-2, using a dedicated apparatus and the materials and feed amounts shown in Table 2. That is, pure water was put into a special mixer, and a commercially available dehydration controlling agent, an aqueous silica sol, a commercially available hardening retarder and an antifoaming agent, and a G-grade cement (manufactured by mitsubishi cement (ltd.) of yu division) were put into the mixer at the compounding amounts shown in table 1 for 90 seconds while rotating an agitating blade at 4000rpm, and then the rotation number of the agitating blade was increased to 12000rpm and the mixture was agitated for 35 seconds, thereby preparing a cement paste.

The prepared slurries were evaluated for fluidity by the following procedure, and further for slurry specific gravity, free water amount (free water), and fluid loss by a dedicated apparatus according to API standards.

1) Determination of specific gravity of slurry

The specific gravity of the prepared cement slurry was measured by using a cup type densitometer made of stainless steel and having a volume of 100ml for 100 cc.

2) Determination of the amount of free Water (free Water)

About 460cc of prepared slurry was conditioned by using an Atmospheric Consistometer Model 165AT (manufactured by Fann Instrument Company) as a conditioning device described in API standards, raising the temperature to 88 ℃ over 30 minutes, and then holding AT 88 ℃ for 1 hour.

The prepared cement slurry (250 cc) was charged into a resin cylinder having a target capacity of 250cc, and the cylinder was tilted at 45 degrees and left to stand for 2 hours. At the time of 2 hours after the standing, water that was free at the upper portion of the slurry was collected with a pipette, and the amount thereof (volume% with respect to 250cc of the slurry) was defined as the amount of free water.

Although the API standard does not particularly specify the numerical range of the amount of free water, it is preferably 2% by volume or less.

3) Determination of fluid loss

About 460cc of prepared slurry was conditioned by using an Atmospheric Consistometer Model 165AT (manufactured by Fann Instrument Company) as a conditioning device described in API standards for 30 minutes, raising the temperature to 88 ℃ and then holding AT 88 ℃ for 1 hour.

130cc of conditioned cement slurry was collected, charged into a Fluid Loss measuring apparatus (Fann Instrument Company) described in API Standard, and then water (dehydrated) generated from the cement slurry when a pressure of 1000psi was continuously applied at 88 ℃ for 30 minutes was collected by a resin measuring cylinder having a capacity of 100cc, and a dehydrated amount V at a measurement time t (30 minutes) was measured_tThe fluid loss was calculated in the equation 1.

[ number 1 ]

Although the API standard does not particularly specify a numerical range of the fluid loss, the API standard is preferably about 100ml or less.

The evaluation results obtained for the specific gravity of the cement paste, the amount of free water (free water), and the fluid loss are shown in table 2.

[ TABLE 1 ]

TABLE 1 additive Components for grout, and grout Components (before storage)

[ remarks ] ". 1": SNOWTEX (registered trademark) only ST-S

"-": without data

[ TABLE 2 ]

TABLE 2 evaluation results

[ remarks ] ". x 2": the particles settled down vigorously and could not be measured

"-": without data

Determination of redispersibility: very good: DLS particle diameter ratio of 1.0 to less than 1.2 and excellent redispersibility

O: the DLS particle diameter ratio is 1.2-1.5, and the redispersibility is good

And (delta): the DLS particle size ratio is 1.6-7.0, and the redispersibility is general

X: white particles are generated in large amounts and sedimentation is severe, so redispersibility is very poor

< investigation >)

As shown in comparative example 1, when the aqueous silica sol was stored at room temperature, the amount of free water generated in the slurry was 0% even when no dispersion stabilizer having a freezing point depressing function was added. However, as shown in comparative example 1, it was found that when the slurry was stored at-20 ℃, gelation of the aqueous silica sol occurred drastically, the slurry sedimented as coarse particles, and the amount of free water generated in the slurry was extremely large, 5.8%, resulting in poor quality of the slurry.

Further, as shown in comparative example 2, when an additive for cement paste containing propylene glycol as a dispersion stabilizer having a freezing point depressing function in an amount of 0.4 mol less than 1 mol per 1000g of a dispersion medium in an aqueous silica dispersion was stored at-20 ℃, gelation of an aqueous silica sol occurred, and the ratio of the DLS particle diameter after storage at-20 ℃ to the DLS particle diameter of a product stored at normal temperature was 280, which was very large. Further, in comparative example 2, it was found that the amount of free water generated in the cement paste was 4.0%, and the suppression effect was reduced.

On the other hand, as shown in examples 1 to 3, it is found that the additive for cement paste containing propylene glycol as a dispersion stabilizer having a freezing point depressing function in an amount of 1 to 13.5 moles per 1000g of water contained in the aqueous silica sol is excellent in redispersibility even when the additive is returned to normal temperature after being stored at-20 ℃ and +50 ℃. Further, it was found that the free water generation amount of the cement paste was 0%, and the free water generation suppressing effect was not impaired at all.

Further, as shown in examples 4 to 6, it is found that the additive for cement paste containing methanol as a dispersion stabilizer having a freezing point depression function in an amount of 2 to 13.5 moles per 1000g of water contained in the aqueous silica sol has substantially good redispersibility when stored at-20 ℃ and +50 ℃ and then returned to normal temperature. Further, it was found that the free water generation amount of the cement paste was substantially 0%, and the free water generation suppressing effect was not impaired.

From the above results, it is understood that an additive for cement paste containing 1 to 30 moles of a dispersion stabilizer having a freezing point depressing function per 1000g of a dispersion medium in an aqueous silica dispersion is an additive for cement paste which can be stored and stored at a temperature ranging from-30 ℃ to +60 ℃ and which has an excellent effect of suppressing the generation of free water from cement paste.