WO2015083652A1

WO2015083652A1 - Additive for drilling fluid, drilling fluid composition and ground excavating method

Info

Publication number: WO2015083652A1
Application number: PCT/JP2014/081684
Authority: WO
Inventors: 学鶴田; 雅彦三塚
Original assignee: 三井化学株式会社
Priority date: 2013-12-04
Filing date: 2014-12-01
Publication date: 2015-06-11
Also published as: JPWO2015083652A1

Abstract

An additive for a drilling fluid, consisting of a water-soluble polyurethane which comprises repeating units (a) represented by general formula (I) and repeating units (b) represented by general formula (II) at a ratio of the molar amount of the repeating units (a) to the total molar amount of the repeating units (a) and the repeating units (b) of 0.5 to 0.99. In the general formulae, A is a divalent linking group which contains a poly(oxyalkylene) group, D is a divalent linking group which contains two or more C_4-21 monovalent hydrocarbon groups in the molecule, and B is a divalent linking group.

Description

Drilling mud additive, drilling mud composition and ground excavation method

The present invention relates to an additive for drilling mud used for the purpose of stabilizing mud used for ground excavation in excavation methods such as petroleum, natural gas, civil engineering, and mining. The present invention also relates to a drilling mud composition containing the drilling mud additive and a ground excavation method for excavating the ground in the presence of the drilling mud composition.

When excavating the ground, bentonite mud water, polymer, etc. are used to absorb frictional heat generated during excavation, to transport excavated debris to the ground, to maintain the excavation surface, to prevent the ejection of groundwater and gas, and to support earth pressure. Stabilizing liquid such as mud is used.

However, it is known that the performance of these stabilizers (muddy water) deteriorates due to mixing of cement, seawater, and other electrolytes. For this reason, many methods have been proposed to increase the stability of mud water by adding lignin sulfonic acid compounds and polycarboxylic acids such as carboxymethyl cellulose, polyacrylic acid polymers or copolymers (Patent Documents 1 and 2). reference). Furthermore, for the purpose of enhancing the stability of mud water, nonionic water-soluble cellulose ether is used as a thickener with little deterioration due to the use of polycarboxylic acid polymer having hydrophobic interaction (see Patent Document 3) and salts. The use of thickening polysaccharides such as welan gum has also been studied (see Patent Document 4).

Japanese Patent Laid-Open No. 10-316963 JP 2001-31959 A JP 2011-225758 A Japanese Patent Laid-Open No. 5-17763

However, in recent years, there has been an increase in ground excavation work in the Gulf area, and energy-related drilling is often carried out at sea, and there is a case where a large amount of seawater is mixed in the muddy water. It is getting harsh. If a large amount of seawater is mixed in the muddy water, the viscosity of the muddy water will be reduced and the fluidity will be lost due to the loss of water in the muddy water even if a large amount of the aforementioned polycarboxylic acid additives are added to the muddy water. Therefore, ground excavation becomes difficult. In addition, when a large amount of seawater is mixed in the muddy water, the bentonite in the muddy water is separated, so that the stability of the muddy water is lowered and the excavation waste conveying ability is lowered. In addition, various nonionic cellulose-based and polysaccharide-based polymers added to supplement the stability of muddy water are foaming and derived from natural products. There was a problem.

Therefore, the object of the present invention is to solve the problems of additives added to the muddy water used for ground excavation, even when muddy water using fresh water, seawater containing electrolyte, etc. are mixed in the muddy water. Another object of the present invention is to provide an additive for drilling mud that can prevent a decrease in fluidity and can ensure excellent stability with a small amount of addition.

In order to solve the above-mentioned problems, the present inventors have conducted extensive research. As a result, it has been found that the above problems can be solved by using an additive for drilling mud made of water-soluble polyurethane having a specific structure, and the present invention has been completed. More specifically, the present invention provides the following.
(1) A repeating unit (a) represented by the following general formula (I) and a repeating unit (b) represented by the following general formula (II), the repeating unit (a) and the repeating unit (b) The ratio of the number of moles of the repeating unit (a) to the total number of moles of water is an additive for drilling mud, which is made of water-soluble polyurethane that is 0.5 to 0.99.

(Where
A represents a divalent linking group containing poly (oxyalkylene);
B represents a divalent linking group. )

(Where
D represents a divalent linking group having two or more monovalent hydrocarbon groups having 4 to 21 carbon atoms in the molecule;
B represents a divalent linking group. )
(2) The additive for drilling mud according to (1), wherein D is a group represented by the following general formula (III) and / or the following general formula (IV).

(Where
R ¹ is a hydrocarbon group or a nitrogen-containing hydrocarbon group having 1 to 20 carbon atoms,
R ² and R ³ may be the same or different and are hydrocarbon groups having 4 to 21 carbon atoms,
Here, at least part of the hydrogen atoms in R ¹ , R ² , and R ³ may be substituted with at least one atom selected from the group consisting of a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Often,
Y and Y ′ may be the same or different and are any one selected from the group consisting of a hydrogen atom, a methyl group, and a CH ₂ Cl group,
Z and Z ′ may be the same or different and are any selected from the group consisting of an oxygen atom, a sulfur atom, and a CH ₂ group,
n and n ′ may be the same or different,
n is an integer of 0 to 15 when Z is an oxygen atom, and is 0 when Z is a sulfur atom or a CH2 group,
n ′ is an integer of 0 to 15 when Z ′ is an oxygen atom, and 0 when Z ′ is a sulfur atom or a CH 2 group. )

(Where
R ⁴ is an alkylene group having 2 to 4 carbon atoms in total,
R ⁵ is a hydrocarbon group having 1 to 21 carbon atoms,
R ⁶ and R ⁷ may be the same or different and each is a hydrocarbon group having 4 to 21 carbon atoms;
Here, at least part of the hydrogen atoms in R ⁴ , R ⁵ , R ⁶ and R ⁷ may be substituted with a fluorine atom, a chlorine atom, a bromine atom or an iodine atom,
S, S ′, and S ″ may be the same or different and are any one selected from the group consisting of a hydrogen atom, a methyl group, and a CH ₂ Cl group,
T and T ′ may be the same or different and are any one selected from the group consisting of an oxygen atom, a sulfur atom, and a CH ₂ group,
P and P ′ may be the same or different,
P is an integer of 0 to 15 when T is an oxygen atom, and 0 when T is a sulfur atom or a CH ₂ group,
P ′ is an integer of 0 to 15 when T ′ is an oxygen atom, and is 0 when T ′ is a sulfur atom or a CH ₂ group,
Q is an integer from 0 to 15. )
(3) The additive for drilling mud according to any one of (1) to (2), wherein the viscosity of a 2% aqueous solution at 20 ° C. is 10 to 100,000 mPa · s.
(4) A drilling mud composition comprising the drilling mud additive according to any one of (1) to (3), an inorganic mud and water.
(5) A ground excavation method characterized by excavating the ground in the presence of the drilling mud composition according to (4).
(6) The ground excavation method as described in (5) including the process of carrying out excavation waste to the ground using the said drilling mud composition.
(7) The ground excavation method according to (5) or (6), wherein a well is excavated.
(8) The ground excavation method according to any one of (5) to (7), wherein the ground of the seabed is excavated.

According to the drilling mud additive of the present invention, even when seawater, cement, etc. are mixed in the mud, it is possible to prevent a decrease in the fluidity of the drilling mud composition with a small amount of addition, and to stabilize it. A drilling mud composition having excellent properties can be provided.

<Additive for drilling mud>
The additive for drilling mud according to the present invention comprises a water-soluble polyurethane having the following structure.

[Water-soluble polyurethane]
The water-soluble polyurethane used in the present invention comprises a repeating unit (a) represented by the following general formula (I) and a repeating unit (b) represented by the following general formula (II) as essential constituent units. is there. As long as the repeating unit (a) and the repeating unit (b) are included, a small amount of any other repeating unit may be included.

(Where
A represents a divalent linking group containing a poly (oxyalkylene) group,
B represents a divalent linking group. )

(Where
D represents a divalent linking group having two or more monovalent hydrocarbon groups having 4 to 21 carbon atoms in the molecule;
B represents a divalent linking group. )

The ratio of the number of moles of the repeating unit (a) to the total number of moles of the repeating unit (a) and the repeating unit (b) is usually 0.5 or more and 0.99 or less, preferably 0.70 or more. It is 0.99 or less, More preferably, it is 0.80 or more and 0.90 or less.
Other optional repeating units (c) may or may not be included, but when included, the ratio of the number of moles of the repeating unit (c) to the total number of moles of the repeating unit (a) and the repeating unit (b). For example, it can be 0.1 or less.

In the general formula (I), the divalent linking group containing the poly (oxyalkylene) group of A is — (C _k H _2k O) ₁ —C _k H _2k — (wherein k is an integer of 2 to 8, l represents an integer of 1 or more, and C _k H _2k may include a branched chain, and k in l may be the same or different.) be able to. More preferred are poly (oxyalkylene) residues having an alkylene group having 2 to 6 carbon atoms, such as poly (oxyethylene) residues and poly (oxypropylene) residues.
The divalent linking group represented by B in the general formulas (I) and (II) is a divalent hydrocarbon group, for example, a divalent chain aliphatic hydrocarbon group or a divalent cyclic aliphatic hydrocarbon. A group, a divalent aromatic hydrocarbon group, and a group obtained by combining two or more of these. B preferably has 1 to 16 carbon atoms.

The divalent linking group represented by D in the general formula (II) has two or more monovalent hydrocarbon groups having 4 to 21 carbon atoms.
Since monovalent hydrocarbon groups having 4 to 21 carbon atoms have low polarity, the interaction between the hydrocarbon groups in water causes a hydrophobic interaction between the polymer chains of the water-soluble polyurethane. For this reason, even a polyurethane having a relatively low molecular weight can exhibit sufficient water retention.
Examples of D include the above-described general formula (III) and general formula (IV).

By using an additive for drilling mud composed of a water-soluble polyurethane having a structure of the general formula (III) or (IV), sufficient water retention can be expressed by kneading in a shorter time.
A, B, and D will be described in detail in the item of the method for producing a water-soluble polyurethane.

[Method for producing water-soluble polyurethane]
The water-soluble polyurethane of the present invention includes, for example, a polyoxyalkylene polyol represented by HO—A—OH, a diisocyanate represented by OCN—B—NCO, and a diol represented by HO—D—OH. It can be produced by reacting. HO-D-OH may be referred to as “comb diol”.

[Polyoxyalkylene polyol: HO-A-OH]
The polyoxyalkylene polyol HO—A—OH having a hydroxyl group at both ends as a constituent material of the repeating unit (a) represented by the general formula (I) is not particularly limited, A polyoxyalkylene polyol having 2 to 6 alkylene groups can be preferably used.

More specifically, polyethylene glycol (PEG), polypropylene glycol (PPG), a copolymer of polyethylene oxide and polypropylene oxide, polytetramethylene ether glycol (PTMEG), polyhexamethylene ether glycol and the like can be preferably used. . Polyethylene glycol (PEG) is particularly preferably used because polyurethane is water-soluble.

The number average molecular weight (Mn) of the polyoxyalkylene polyol HO—A—OH having a hydroxyl group at both ends, which is a constituent material of the repeating unit (a), is preferably 400 or more and 100,000 or less, more preferably 400 or more and 20 or more. , 000 or less, more preferably in the range of 900 or more and 9,000 or less. If the number average molecular weight is 400 or more, a water-soluble polyurethane having sufficient water retention can be obtained. On the other hand, if the number average molecular weight is 100,000 or less, a sufficient polymerization reaction can be performed.

The polyoxyalkylene polyol HO-A-OH having a hydroxyl group at both ends, which is a constituent material of the repeating unit (a), can be used not only alone but in combination of two or more polyoxyalkylene polyols. May be used. For example, polyethylene glycol and polypropylene glycol or polytetramethylene ether glycol can be used in combination. Since polyurethane is water-soluble, it is more preferable to use 70% by mass or more of polyethylene glycol (PEG).

Moreover, if it is up to 20% by mass of the total polyols, low molecular weight glycols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, tetramethylene glycol, hexamethylene glycol and the like are used in combination with the above polyoxyalkylene polyols. May be.

[Diisocyanate: OCN-B-NCO]
The diisocyanate OCN-B-NCO, which is a constituent material of the repeating units (a) and (b) represented by the general formula (I) and the general formula (II), is not particularly limited. Examples thereof include a diisocyanate compound selected from the group consisting of chain aliphatic diisocyanates, cycloaliphatic diisocyanates, and aromatic diisocyanates. Among these, it is preferable to use diisocyanates having 3 to 18 carbon atoms (including carbon atoms of the NCO group).

Chain aliphatic diisocyanates are polyisocyanate compounds having a structure in which NCO groups are connected by a linear or branched alkylene group. Specific examples include methylene diisocyanate, ethylene diisocyanate, trimethylene diisocyanate, 1-methylethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, 2-methylbutane-1,4-di- Isocyanate, hexamethylene diisocyanate (HMDI), heptamethylene diisocyanate, 2,2′-dimethylpentane-1,5-diisocyanate, lysine diisocyanate methyl ester (LDI), octamethylene diisocyanate, 2,5-dimethylhexane-1,6-diisocyanate, 2,2,4-trimethylpentane-1,5-diisocyanate, nonamethylene diisocyanate, 2,4,4-trimethylhexane-1,6 -Diisocyanate, decamethylene dii Cyanate, undecamethylene diisocyanate, dodecamethylene diisocyanate, tridecamethylene diisocyanate, tetradecamethylene diisocyanate, pentadecamethylene diisocyanate include diisocyanates such as hexamethylene decamethylene diisocyanate.

Cycloaliphatic diisocyanates are polyisocyanate compounds having a structure in which NCO groups are connected by an alkylene group having a cyclic structure. Specific examples include cyclohexane-1,2-diisocyanate, cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate, 1-methylcyclohexane-2,4-diisocyanate, 1- Methylcyclohexane-2,6-diisocyanate, 1-ethylcyclohexane-2,4-diisocyanate, 4,5-dimethylcyclohexane-1,3-diisocyanate, 1,2-dimethylcyclohexane-ω, ω ′ -Diisocyanate, 1,4-dimethylcyclohexane-ω, ω'-diisocyanate, isophorone diisocyanate (IPDI), dicyclohexylmethylmethane-4,4'-diisocyanate, 2,2'-dimethyldicyclohexylmethane -4,4'-diisocyanate, 3,3'-dimethyldisic Hexylmethane-4,4′-diisocyanate, isopropylidenebis (4-cyclohexylisocyanate) (IPCI), 1,3-bis (isocyanatomethyl) cyclohexane, hydrogenated tolylene diisocyanate (H-TDI), Examples thereof include diisocyanates such as hydrogenated 4,4′-diphenylmethane diisocyanate (H-MDI), hydrogenated xylylene diisocyanate (H-XDI), norbornane diisocyanate methyl (NBDI), and the like.

Aromatic diisocyanates are polyisocyanates having a structure in which NCO groups are connected by aromatic groups such as phenylene groups, alkyl-substituted phenylene groups, and aralkylene groups, or hydrocarbon groups containing aromatic groups. It is a nate compound. Specific examples include 1,3- and 1,4-phenylene diisocyanate, 1-methyl-2,4-phenylene diisocyanate (2,4-TDI), 1-methyl-2,6-phenylene diisocyanate. Nert (2,6-TDI), 1-methyl-2,5-phenylene diisocyanate, 1-methyl-3,5-phenylene diisocyanate, 1-ethyl-2,4-phenylene diisocyanate, 1- Isopropyl-2,4-phenylene diisocyanate, 1,3-dimethyl-2,4-phenylene diisocyanate, 1,3-dimethyl-4,6-phenylene diisocyanate, 1,4-dimethyl-2,5 -Phenylene diisocyanate, m-xylylene diisocyanate, diethylbenzene diisocyanate, diisopropylbenzene diisocyanate, 1- Til-3,5-diethylbenzene-2,4-diisocyanate, 3-methyl-1,5-diethylbenzene-2,4-diisocyanate, 1,3,5-triethylbenzene-2,4-diisocyanate , Naphthalene-1,4-diisocyanate, naphthalene-1,5-diisocyanate, 1-methylnaphthalene-1,5-diisocyanate, naphthalene-2,6-diisocyanate, naphthalene-2,7- Diisocyanate, 1,1-dinaphthyl-2,2′-diisocyanate, biphenyl-2,4′-diisocyanate, biphenyl-4,4′-diisocyanate, 1,3-bis (1-isocyanate -1-methylethyl) benzene, 3,3′-dimethylbiphenyl-4,4′-diisocyanate, diphenylmethane-4,4′-diisocyanate Over preparative (MDI), diphenylmethane-2,2'-diisocyanate, diphenylmethane-2,4'-diisocyanate, include diisocyanates such as p- xylylene diisocyanate (XDI).

[Comb diol: HO-D-OH]
The comb diol HO-D-OH, which is a constituent material of the repeating unit (b) represented by the general formula (II), has at least two monovalent hydrocarbon groups having 4 to 21 carbon atoms in the molecule. It is a diol having. Here, a plurality of monovalent hydrocarbon groups are grafted as side chains on the molecular skeleton of diols, and from this shape, they are called “comb diols”. The monovalent hydrocarbon group having 4 to 21 carbon atoms is not particularly limited, and examples thereof include an alkyl group, an alkenyl group, an aralkyl group, and an aryl group.

Further, in the comb diol HO-D-OH, the graft position of the monovalent hydrocarbon group having 4 to 21 carbon atoms may be directly grafted to the molecular skeleton of the diol, or may be a methylene group or an ether group. In addition, it may be bonded to the molecular skeleton via a thioether group, a polyether group or the like.

The molecular skeleton of the comb-shaped diol HO-D-OH may be composed only of hydrocarbons, but an ether group (—O—), a polyether group, a tertiary amino group (—N (R) —), etc. A diol having the polar group in the molecular skeleton is also preferably used in the present invention. The method for producing such a comb diol is not particularly limited, and can be obtained by a known method. Known methods include, for example, methods described in JP-A-11-343328 and JP-A-2000-297133, and methods described in JP-A-2004-169011.

Examples of the comb diol HO-D-OH preferably used in the present invention include comb diols represented by the following general formula (IIIa) and the following general formula (IVa). The comb diols represented by the following general formula (IIIa) and general formula (IVa) may be used alone or in combination of two or more. For example, when using a plurality of kinds of comb-shaped diols represented by the general formula (IIIa), when using a plurality of kinds of comb-shaped diols represented by the general formula (IVa), it is represented by the general formula (IIIa). The comb-type diol may be mixed with the comb-type diol represented by the general formula (IVa).

(Where
R ¹ is a hydrocarbon group or nitrogen-containing hydrocarbon group having 1 to 20 carbon atoms, more preferably 4 to 12 carbon atoms,
R ² and R ³ may be the same or different and are hydrocarbon groups having 4 to 21 carbon atoms, more preferably 4 to 12 carbon atoms,
Here, at least part of the hydrogen atoms in R ¹ , R ² , and R ³ may be substituted with at least one atom selected from the group consisting of a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Often,
Y and Y ′ may be the same or different and are any one selected from the group consisting of a hydrogen atom, a methyl group, and a CH ₂ Cl group,
Z and Z ′ may be the same or different and are any selected from the group consisting of an oxygen atom, a sulfur atom, and a CH ₂ group,
n and n ′ may be the same or different,
n is an integer of 0 to 15 when Z is an oxygen atom, and 0 when Z is a sulfur atom or a CH ₂ group,
n ′ is an integer of 0 to 15 when Z ′ is an oxygen atom, and 0 when Z ′ is a sulfur atom or a CH ₂ group. )

(Where
R ⁴ is an alkylene group having 2 to 4 carbon atoms in total,
R ⁵ is a hydrocarbon group having 1 to 21 carbon atoms, preferably 1 to 20 carbon atoms, more preferably 4 to 12 carbon atoms,
R ⁶ and R ⁷ may be the same or different and are hydrocarbon groups having 4 to 21 carbon atoms, more preferably 4 to 12 carbon atoms,
Here, at least part of the hydrogen atoms in R ⁴ , R ⁵ and R ⁶ may be substituted with a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom,
At least a part of the hydrogen atoms in R ⁷ may be substituted with a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom,
S, S ′, and S ″ may be the same or different and are any one selected from the group consisting of a hydrogen atom, a methyl group, and a CH ₂ Cl group,
T and T ′ may be the same or different and are any one selected from the group consisting of an oxygen atom, a sulfur atom, and a CH ₂ group,
P and P ′ may be the same or different,
P is an integer of 0 to 15 when T is an oxygen atom, and 0 when T is a sulfur atom or a CH ₂ group,
P ′ is an integer of 0 to 15 when T ′ is an oxygen atom, and is 0 when T ′ is a sulfur atom or a CH ₂ group,
Q is an integer from 0 to 15. )

The method for producing the water-soluble polyurethane used in the present invention is not particularly limited, and any known method can be employed. As a method for producing a water-soluble polyurethane, for example, the method described in JP-A-11-343328 and JP-A-2000-297133 or the method described in JP-A-2004-169011 is used. be able to. Among them, the method described in JP-A No. 2004-169011 is particularly excellent in that the particle diameters of the obtained polyurethane are uniform and the average particle diameter can be easily reduced to 200 μm or less.

[Physical properties of water-soluble polyurethane]
The viscosity of the water-soluble polyurethane used in the present invention was measured with a B-type viscometer (up to 100,000 mPa · s using a BL-type viscometer at 6 rpm, and higher viscosity using a BH-type viscometer 4 rpm) 20 The viscosity of the 2% aqueous solution at 0 ° C. is preferably in the range of 1 mPa · s to 500,000 mPa · s, more preferably 10 mPa · s to 100,000 mPa · s.

In particular, when the water-soluble polyurethane according to the present invention is used for a drilling mud composition containing an inorganic mud and water as an additive for drilling mud, the viscosity of a 2% aqueous solution is 100 mPa · s or more and 80,000 mPa · s or less. The range is preferable, and a range of 1,000 mPa · s to 50,000 mPa · s is optimal. If the viscosity of the 2% aqueous solution is 1,000 mPa · s or more, the water retention can be sufficiently increased with a small addition amount of 0.01%, while if it is 50,000 mPa · s or less, the dissolution time is shortened. can do. The viscosity of the 2% aqueous solution can be adjusted as appropriate by changing the type and ratio of the raw materials used in the production of the water-soluble polyurethane.

Also, the water-soluble polyurethane used in the present invention can be dried after production and stored in a powder state. The particle diameter of the powder is preferably finer from the viewpoint of easy stirring and dissolution. However, since it is difficult to handle if it is too fine, the average particle diameter is preferably 10 μm or more and 300 μm or less, more preferably about 50 μm or more and 200 μm or less.

[Drilling mud composition]
The drilling mud composition of the present invention contains the drilling mud additive made of the water-soluble polyurethane, an inorganic mud, and water.

In general, polymer-based drilling mud additives have a large molecular weight, and by increasing the viscosity, the mud is thickened to reduce the amount of dehydration and to give thixotropy. Since the additive for drilling mud of the present invention uses the water-soluble polyurethane having the above-mentioned specific structure, even a polyurethane having a relatively low molecular weight exhibits sufficient water retention, but its molecular weight or addition to the composition By appropriately setting the amount, it can be suitably used as an additive for drilling mud.

The amount of water-soluble polyurethane added cannot be unconditionally because the viscosity of the mud varies greatly depending on the type and proportion of the inorganic mud to be blended, the presence or absence of the cement, and the blending proportion. The water-soluble polyurethane is preferably 0.01 to 2.0 parts by weight, more preferably 0.02 to 1.0 parts by weight with respect to 100 parts by weight. However, other amounts may be used as long as the viscosity can be adjusted to a desired value and a stable mud composition can be obtained without coagulating and sedimenting inorganic mud.

Examples of the inorganic mud include bentonite, attapulgite, and hydrous magnesium silicate. Bentonite is preferable from the viewpoint of effects. In addition, a large amount of cement used in the soil cement method may be blended, and barite, chalk, iron oxide, or the like may be added to increase the density.

The mixing ratio of the inorganic mud in the drilling mud composition of the present invention is preferably 1.0 to 30 parts by mass, more preferably 2.0 to 20 parts per 100 parts by mass of water. Part by mass.
The water may be fresh water or sea water, and fresh water and sea water may be mixed.

When the water is fresh water, a fresh water drilling mud composition that maintains the characteristics of the drilling mud composition can be obtained even when the additive amount of the drilling mud additive of the present invention is less than that of seawater.
The salt concentration of seawater is not particularly limited, but may be, for example, 10,000 ppm or more.

[Other ingredients]
The drilling mud composition of the present invention can contain other additives as optional components. Other additives are not particularly limited. For example, carboxymethyl cellulose; poly (meth) acrylic acid polymer or copolymer; zeolites; dispersants; inorganic salts; electrolytes; lignin sulfonates, tannins And various organic salt substances of lignite; water-soluble polymers such as polyvinyl alcohol, polyethylene glycol (PEG), polyethylene oxide (PEO), rhamsan gum, guar gum, xanthan gum, and welan gum.

Further, the drilling mud composition of the present invention includes a lubricant, an anti-sludge agent, an emulsion resin, a surfactant, an air entraining agent (AE agent), an antifoaming agent, and a shrinkage within a range not impairing the object of the present invention. Known additives such as a reducing agent, curing accelerator, curing retarder, and various fibers (rock wool, glass fiber, carbon fiber, cellulose fiber, pulp fiber, various synthetic resin fibers) and the like are appropriately blended depending on the application. May be.

In the method for preparing a drilling mud composition of the present invention, the method for using the drilling mud additive, the method for adding the drilling mud additive and other components, the order of addition, etc. are not particularly limited. If the agent is present in the drilling mud composition, it will be effective. For example, (1) A method in which the additive of the present invention and other additives as required are added to a mixture of inorganic mud and water and mixed together (wherein the additives are added at the same time or sequentially) (2) A product obtained by kneading an inorganic mud and water by an appropriate method (a), and an aqueous phase (b) in which the additive of the present invention and other additives are dissolved in water as required. ), And a method of mixing (a) and (b) during preparation of the drilling mud composition, (3) inorganic mud, water, additives of the present invention, and other additions as required A method in which the agent is uniformly kneaded by an appropriate method, pulverized, and suspended in water can be employed.

When using the additive for drilling mud according to the present invention, it can be easily suspended, swollen, thickened by simply stirring with a stirrer normally used at a drilling site, and is suitable for well conditions. A drilling mud composition having the following characteristics can be obtained. Moreover, the characteristics of the drilling mud composition can be easily selected and adjusted according to the state of the well.

Further, according to the present invention, a drilling mud composition having a viscosity of 15 mPa · s or more can be easily prepared even when seawater having a salt concentration of 10,000 ppm or more is used. The drilling mud composition obtained here can be adjusted by adjusting the viscosity of the drilling mud composition by splitting with seawater or adding the additive for drilling mud of the present invention, and other characteristics as a drilling mud composition. Therefore, the work can be facilitated from the management aspect.

The present invention also relates to a ground excavation method characterized by excavating the ground in the presence of the drilling mud composition according to the present invention. The construction method includes a step of carrying out drilling waste to the ground using the drilling mud composition according to the present invention, and includes drilling of an ore deposit that can be used as a resource, such as oil and natural gas. In particular, this method is suitable for excavating the seabed ground where a large amount of seawater is mixed.

Hereinafter, although an example and a comparative example are shown and the present invention is explained concretely, the present invention is not limited to these examples.

<Synthesis of water-soluble polyurethane PU-1>
[Synthesis of Comb Diol-1]
A magnetic stirrer, a thermometer, and a dropping funnel were placed in a 500 mL round bottom flask, 83.0 g of laurylamine (manufactured by Kanto Chemical Co., Inc.) was charged, and the inside of the flask was replaced with nitrogen. Subsequently, 317.0 g of lauryl glycidyl ether (manufactured by Kanto Chemical Co., Inc.) was dropped over 40 minutes using a dropping funnel while the flask was heated to 90 ° C. in an oil bath and stirred. After completion of dropping, the temperature of the oil bath was raised to 120 ° C., and the flask was heated for 10 hours. Subsequently, the temperature of the oil bath was raised to 150 ° C., and a small amount of unreacted material was distilled off under reduced pressure using a vacuum pump at a degree of vacuum of 3 mmHg. As a result, comb-shaped diol-1 (average molecular weight from OH value: 797) in which lauryl glycidyl ether was added at a ratio of 2 moles to 1 mole of laurylamine was obtained in a yield of 95%.

[Synthesis of Prepolymer-1]
To the 100 mL glass flask, 33.0 g of the comb-shaped diol-1 obtained above and 67.0 g of hexamethylene diisocyanate (HDI) were added. The flask was heated to 80 ° C. for 8 hours to obtain Prepolymer-1.

[Synthesis of water-soluble polyurethane PU-1]
The compound was synthesized according to the method described in Example 8 of JP-A No. 2004-169011.
Into a 2,000 mL separable flask made of glass, 500 g of commercially available polyethylene glycol (manufactured by Sanyo Kasei Co., Ltd., trade name: PEG # 6000, number average molecular weight: 8,630) was charged and melted at 150 ° C. under a nitrogen seal. . While stirring this, it was dried under reduced pressure (3 mmHg) for 3 hours. After drying, the temperature was lowered to 70 ° C., and the flask was filled with 1 atm of nitrogen. Subsequently, 15.15 g of the prepolymer-1 obtained above, 0.18 g of hexamethylene diisocyanate (HDI), 1,000 ppm of BHT (di-ter-butylhydroxytoluene) as an antioxidant were added and stirred, 350 g of isooctane (manufactured by Wako Pure Chemical Industries, Ltd.) as a solvent and 1.5 g of a dispersant were added and dispersed with a disper. Here, the ratio of the repeating unit (a) to the repeating unit (b) was 0.85 and 0.15. While stirring the flask, 0.05 g of dibutyltin dilaurate (DBTDL) was added as a catalyst and reacted at 90 ° C. for 6 hours. Subsequently, the temperature was lowered to 40 ° C., the product was taken out from the flask, and filtered and dried to obtain a water-soluble polyurethane (PU-1). The average particle diameter of the obtained resin powder was 100 μm, and the viscosity of a 2% aqueous solution at 20 ° C. was 27,000 mPa · s (BL viscometer, 6 rpm).

<Synthesis of water-soluble polyurethane PU-2>
[Synthesis of Prepolymer-2]
To a 100 mL glass flask, 32.5 g of the comb-shaped diol-1 obtained above and 67.5 g of hexamethylene diisocyanate (HDI) were added. The flask was heated to 80 ° C. for 8 hours to obtain Prepolymer-2.

[Synthesis of water-soluble polyurethane PU-2]
The compound was synthesized according to the method described in Example 8 of JP-A No. 2004-169011.
Into a 2,000 mL separable flask made of glass, 500 g of commercially available polyethylene glycol (manufactured by Sanyo Kasei Co., Ltd., trade name: PEG # 6000, number average molecular weight: 8,630) was charged and melted at 150 ° C. under a nitrogen seal. . While stirring this, it was dried under reduced pressure (3 mmHg) for 3 hours. After drying, the temperature was lowered to 70 ° C., and the flask was filled with 1 atm of nitrogen. Subsequently, 15.38 g of the prepolymer-2 obtained above, 0.16 g of hexamethylene diisocyanate (HDI), 1,000 ppm of BHT (di-ter-butylhydroxytoluene) as an antioxidant were added and stirred, 350 g of isooctane (manufactured by Wako Pure Chemical Industries, Ltd.) as a solvent and 1.5 g of a dispersant were added and dispersed with a disper. Here, the ratio of the repeating unit (a) to the repeating unit (b) was 0.85 and 0.15. While stirring the flask, 0.05 g of dibutyltin dilaurate (DBTDL) was added as a catalyst and reacted at 90 ° C. for 6 hours. Subsequently, the temperature was lowered to 40 ° C., the product was taken out from the flask, filtered and dried to obtain a water-soluble polyurethane (PU-2). The average particle diameter of the obtained resin powder was 100 μm, and the viscosity of a 2% aqueous solution at 20 ° C. was 48,000 mPa · s (BL viscometer, 6 rpm).

<Synthesis of water-soluble polyurethane PU-3>
[Synthesis of Comb Diol-2]
A magnetic stirrer, a thermometer, and a dropping funnel were placed in a 500 mL round bottom flask, charged with 65.0 g of octylamine (manufactured by Kanto Chemical Co., Inc.), and the inside of the flask was replaced with nitrogen. Subsequently, 248.0 g of lauryl glycidyl ether (manufactured by Kanto Chemical Co., Inc.) was dropped over 40 minutes using a dropping funnel while the flask was heated to 90 ° C. in an oil bath and stirred. After completion of dropping, the temperature of the oil bath was raised to 120 ° C., and the flask was heated for 10 hours. Subsequently, the temperature of the oil bath was raised to 150 ° C., and a small amount of unreacted material was distilled off under reduced pressure using a vacuum pump at a degree of vacuum of 3 mmHg. As a result, comb-shaped diol-2 (average molecular weight from OH value: 613) in which lauryl glycidyl ether was added at a ratio of 2 mol to 1 mol of octylamine was obtained in a yield of 95%.

[Synthesis of Prepolymer-3]
To a 100 mL glass flask, 32.0 g of the comb-shaped diol-2 obtained above and 67.0 g of hexamethylene diisocyanate (HDI) were added. The flask was heated to 80 ° C. for 8 hours to obtain Prepolymer-3.

[Synthesis of water-soluble polyurethane PU-3]
The compound was synthesized according to the method described in Example 8 of JP-A No. 2004-169011.
Into a 2,000 mL separable flask made of glass, 500 g of commercially available polyethylene glycol (manufactured by Sanyo Kasei Co., Ltd., trade name: PEG # 6000, number average molecular weight: 8,630) was charged and melted at 150 ° C. under a nitrogen seal. . While stirring this, it was dried under reduced pressure (3 mmHg) for 3 hours. After drying, the temperature was lowered to 70 ° C., and the flask was filled with 1 atm of nitrogen. Subsequently, 15.4 g of the prepolymer-3 obtained above, 0.17 g of hexamethylene diisocyanate (HDI) and 1,000 ppm of BHT (di-ter-butylhydroxytoluene) as an antioxidant were added and stirred. 350 g of isooctane (manufactured by Wako Pure Chemical Industries, Ltd.) as a solvent and 1.5 g of a dispersant were added and dispersed with a disper. Here, the ratio of the repeating unit (a) to the repeating unit (b) was 0.85 and 0.15. While stirring the flask, 0.05 g of dibutyltin dilaurate (DBTDL) was added as a catalyst and reacted at 90 ° C. for 6 hours. Subsequently, the temperature was lowered to 40 ° C., the product was taken out from the flask, filtered and dried to obtain a water-soluble polyurethane (PU-3). The average particle diameter of the obtained resin powder was 100 μm, and the viscosity of a 2% aqueous solution at 20 ° C. was 22,000 mPa · s (BL viscometer, 6 rpm).

<Synthesis of water-soluble polyurethane PU-4>
[Synthesis of Prepolymer-4]
31.8 g of the comb-shaped diol-2 obtained above and 68.2 g of hexamethylene diisocyanate (HDI) were added to a 100 mL glass flask. The flask was heated to 80 ° C. for 8 hours to obtain Prepolymer-4.

[Synthesis of water-soluble polyurethane PU-4]
The compound was synthesized according to the method described in Example 8 of JP-A No. 2004-169011.
Into a 2,000 mL separable flask made of glass, 500 g of commercially available polyethylene glycol (manufactured by Sanyo Kasei Co., Ltd., trade name: PEG # 6000, number average molecular weight: 8,630) was charged and melted at 150 ° C. under a nitrogen seal. . While stirring this, it was dried under reduced pressure (3 mmHg) for 3 hours. After drying, the temperature was lowered to 70 ° C., and the flask was filled with 1 atm of nitrogen. Subsequently, 16.7 g of the prepolymer-4 obtained above, 0.13 g of hexamethylene diisocyanate (HDI), 1,000 ppm of BHT (di-ter-butylhydroxytoluene) as an antioxidant were added and stirred, 350 g of isooctane (manufactured by Wako Pure Chemical Industries, Ltd.) as a solvent and 1.5 g of a dispersant were added and dispersed with a disper. Here, the ratio of the repeating unit (a) to the repeating unit (b) was 0.85 and 0.15. While stirring the flask, 0.05 g of dibutyltin dilaurate (DBTDL) was added as a catalyst and reacted at 90 ° C. for 6 hours. Subsequently, the temperature was lowered to 40 ° C., the product was taken out from the flask, filtered and dried to obtain a water-soluble polyurethane (PU-4). The average particle diameter of the obtained resin powder was 100 μm, and the viscosity of a 2% aqueous solution at 20 ° C. was 40,000 mPa · s (BL viscometer, 6 rpm).

<Synthesis of water-soluble polyurethane PU-5>
[Synthesis of comb-shaped diol-3]
A magnetic stirrer, thermometer, and dropping funnel were placed in a 500 mL round bottom flask, charged with 64.6 g of 2-ethylhexylamine (manufactured by Kanto Chemical Co., Inc.), and the inside of the flask was replaced with nitrogen. Subsequently, 190.0 g of 2-ethylhexyl glycidyl ether (manufactured by Kanto Chemical Co., Inc.) was dropped over 40 minutes using a dropping funnel while the flask was heated to 90 ° C. in an oil bath and stirred. After completion of dropping, the temperature of the oil bath was raised to 120 ° C., and the flask was heated for 10 hours. Subsequently, the temperature of the oil bath was raised to 150 ° C., and a small amount of unreacted material was distilled off under reduced pressure using a vacuum pump at a degree of vacuum of 3 mmHg. As a result, comb-shaped diol-3 (average molecular weight from OH value: 510) in which 2-ethylhexyl glycidyl ether was added at a ratio of 2 mol to 1 mol of 2-ethylhexylamine was obtained in a yield of 95%.

[Synthesis of Prepolymer-5]
20 g of the comb-shaped diol-3 obtained above and 45.5 g of hexamethylene diisocyanate (HDI) were added to a 100 mL glass flask. The flask was heated to 80 ° C. for 8 hours to obtain Prepolymer-5.

[Synthesis of water-soluble polyurethane PU-5]
The compound was synthesized according to the method described in Example 8 of JP-A No. 2004-169011.
Into a 2,000 mL separable flask made of glass, 500 g of commercially available polyethylene glycol (manufactured by Sanyo Kasei Co., Ltd., trade name: PEG # 6000, number average molecular weight: 8,630) was charged and melted at 150 ° C. under a nitrogen seal. . While stirring this, it was dried under reduced pressure (3 mmHg) for 3 hours. After drying, the temperature was lowered to 70 ° C., and the flask was filled with 1 atm of nitrogen. Subsequently, 16.4 g of the prepolymer-5 obtained above, 0.10 g of hexamethylene diisocyanate (HDI), 1,000 ppm of BHT (di-ter-butylhydroxytoluene) as an antioxidant were added and stirred, 350 g of isooctane (manufactured by Wako Pure Chemical Industries, Ltd.) as a solvent and 1.5 g of a dispersant were added and dispersed with a disper. Here, the ratio of the repeating unit (a) to the repeating unit (b) was 0.85 and 0.15. While stirring the flask, 0.05 g of dibutyltin dilaurate (DBTDL) was added as a catalyst and reacted at 90 ° C. for 6 hours. Subsequently, the temperature was lowered to 40 ° C., the product was taken out from the flask, filtered and dried to obtain a water-soluble polyurethane (PU-5). The average particle size of the obtained resin powder was 100 μm, and the viscosity of a 2% aqueous solution at 20 ° C. was 42,000 mPa · s (BL viscometer, 6 rpm).

<Synthesis of water-soluble polyurethane PU-6>
[Synthesis of Comb Diol-4]
A magnetic stirrer, thermometer, and dropping funnel were placed in a 500 mL round bottom flask, charged with 64.6 g of 3-lauryloxypropylamine (manufactured by Kanto Chemical Co., Inc.), and the inside of the flask was replaced with nitrogen. Subsequently, 100.7 g of 2-ethylhexyl glycidyl ether (manufactured by Kanto Chemical Co., Inc.) was added dropwise over 40 minutes using a dropping funnel while the flask was heated to 90 ° C. in an oil bath and stirred. After completion of dropping, the temperature of the oil bath was raised to 120 ° C., and the flask was heated for 10 hours. Subsequently, the temperature of the oil bath was raised to 150 ° C., and a small amount of unreacted material was distilled off under reduced pressure using a vacuum pump at a degree of vacuum of 3 mmHg. As a result, comb-shaped diol-4 (average molecular weight from OH number: 630) in which 2-ethylhexyl glycidyl ether was added at a ratio of 2 moles to 1 mole of 3-lauryloxypropylamine was obtained in a yield of 95%.

[Synthesis of Prepolymer-6]
20 g of the comb-shaped diol-4 obtained above and 44 g of hexamethylene diisocyanate (HDI) were added to a 100 mL glass flask. The flask was heated to 80 ° C. for 6 hours to obtain Prepolymer-6.

[Synthesis of water-soluble polyurethane PU-6]
The compound was synthesized according to the method described in Example 8 of JP-A No. 2004-169011.
Into a 2,000 mL separable flask made of glass, 500 g of commercially available polyethylene glycol (manufactured by Sanyo Kasei Co., Ltd., trade name: PEG # 6000, number average molecular weight: 8,630) was charged and melted at 150 ° C. under a nitrogen seal. . While stirring this, it was dried under reduced pressure (3 mmHg) for 3 hours. After drying, the temperature was lowered to 70 ° C., and the flask was filled with 1 atm of nitrogen. Subsequently, 16.0 g of the prepolymer-6 obtained above and 1,000 ppm of di-ter-butylhydroxytoluene (BHT) as an antioxidant were added and stirred, and then isooctane as a solvent (manufactured by Wako Pure Chemical Industries, Ltd.) 350 g and a dispersant 1.5 g were added and dispersed with a disper. Here, the ratio of the repeating unit (a) to the repeating unit (b) was 0.88 and 0.12. While stirring the flask, 0.05 g of dibutyltin dilaurate (DBTDL) was added as a catalyst and reacted at 90 ° C. for 6 hours. Subsequently, the temperature was lowered to 40 ° C., the product was taken out from the flask, filtered and dried to obtain a water-soluble polyurethane (PU-6). The average particle diameter of the obtained resin powder was 120 μm, and the viscosity of a 2% aqueous solution at 20 ° C. was 200,000 mPa · s (BH viscometer, 4 rpm).

Hereinafter, specific embodiments of the present invention will be described with reference to Examples and Comparative Examples.
Examples 1 to 17 and Comparative Examples 1 to 7
1) Tap water 2) Seawater: Artificial seawater (trade name “Aquamarine S” manufactured by Hachishu Pharmaceutical Co., Ltd.)
3) Clay: Bentonite, Gunma Prefecture, 200 mesh 4) Cement: Ordinary Portland cement (manufactured by Nippon Cement)
5) Water-soluble polysaccharide: Welan gum (Merck Kelco Division)
6) Nonionic cellulose ether: hydroxypropyl methylcellulose (hereinafter abbreviated as HPMC) Degree of substitution: 0.7
7) Degree of substitution with carboxymethylcellulose (hereinafter abbreviated as CMC): 0.7
8) Salt-resistant carboxymethylcellulose (hereinafter abbreviated as salt-resistant CMC) Degree of substitution: 1.5
9) Commercially available sodium polyacrylate (weight average molecular weight 10,000-14,000) aqueous solution (non-volatile content concentration 41.0%) (trade name “SuperSlurry B” manufactured by Sanyo Kasei))
And each component of the water-soluble polyurethane (PU-1 to PU6) was blended in the proportions shown in Table 1 to obtain a drilling mud composition.

<Manufacturing method>
Using a Hobart mixer with a rotation speed of 383 rpm, the kneaded water and clay were stirred for 10 minutes, then water and additives were added and stirred for 1 minute to obtain a drilling mud composition.
In Examples 2, 4, 8, 10, 12, 15, 17, and Comparative Examples 6 and 7, a cement was further added and stirred for 5 minutes to obtain a drilling mud composition.

About the obtained drilling mud composition, the property was measured with the following method and the result was written together in Table 1.
1) Specific gravity: 1000 ml of muddy water was put into a 1000 ml graduated cylinder, and its weight was measured.
2) Foaming rate: The foaming rate was calculated by the following formula.
Foaming rate = {(initial specific gravity−specific gravity after stirring) / initial specific gravity} × 100
In Examples 2, 4, 8, 10, 12, 15, 17 and Comparative Examples 6 and 7, the specific gravity after 5 minutes of cement addition was the initial specific gravity, and then the specific gravity after stirring for 25 minutes was the specific gravity after stirring. .
In other examples and comparative examples, the specific gravity before and after stirring for 25 minutes was set as the initial specific gravity and the specific gravity after stirring, respectively.
3) Funnel viscosity: 500 ml of muddy water was added to the funnel cone, and the time required for flow down was measured.
4) Dewatering amount: 500 ml of muddy water was put into a container of an API filtration tester, pressurized with carbon dioxide gas (0.3 MPa (3 kgf / cm ² )), and the amount of filtered water (dehydrated amount) after 30 minutes was measured. .

Comparative Examples 1 and 2 are examples in which CMC is used as an additive, but a normal CMC with a substitution degree of 0.7 cannot be used because of a large amount of dehydration due to seawater contamination.
The salt-resistant CMC having a substitution degree of 1.5 in Comparative Example 3 is less deteriorated than that having a substitution degree of 0.7, but the amount of dewatering is large and the mud wall performance in the implementation process is inferior.

Comparative Example 4 is an example in which HPMC, which is a nonionic water-soluble cellulose ether, is used as an additive. However, due to the foaming property of HPMC, muddy water is foamed and cannot be used practically.
As additives, Comparative Examples 5 and 6 are welan gum, which is a kind of water-soluble polysaccharide, and Comparative Example 7 is an example using sodium polyacrylate as a water-soluble polymer. Although there is little, there is deterioration due to cement mixing, exceeding the target value of normal dehydration amount of 50 ml or less, and more addition is necessary.

Examples 1 to 17 are examples in which the water-soluble polyurethane of the present invention is used as an additive, but it does not agglomerate even when mixed with seawater and cement, and the amount of dewatering is small and the mud wall performance is excellent. In addition, it is easy to use in construction without foaming even with long-time stirring.

<Summary>
From the above results, it can be seen that the drilling mud composition of the present invention has low viscosity and high drainage in basic performance and is excellent in dispersibility. In addition, regarding seawater resistance and cement resistance, it can be seen that the effect of reducing the tendency to breathing and gelation and suppressing the increase in the amount of filtered water (high drainage) can be seen and excellent effects can be exhibited.

The additive for drilling mud of the present invention can be suitably used for stabilizing a drilling mud composition used for ground excavation in drilling methods such as petroleum, natural gas, civil engineering, and mining.

Claims

A repeating unit (a) represented by the following general formula (I) and a repeating unit (b) represented by the following general formula (II):
Drilling mud additive comprising water-soluble polyurethane, wherein the ratio of the number of moles of the repeating unit (a) to the total number of moles of the repeating unit (a) and the repeating unit (b) is 0.5 or more and 0.99 or less. .

(Where
A represents a divalent linking group containing a poly (oxyalkylene) group, and B represents a divalent linking group. )

(Where
D represents a divalent linking group having two or more monovalent hydrocarbon groups having 4 to 21 carbon atoms in the molecule;
B represents a divalent linking group. )
The additive for drilling mud according to claim 1, wherein D is a group represented by the following general formula (III) and / or the following general formula (IV).

(Where
R 1 is a hydrocarbon group having 1 to 20 carbon atoms or a nitrogen-containing hydrocarbon group,
R 2 and R 3 may be the same or different and are hydrocarbon groups having 4 to 21 carbon atoms,
Here, at least part of the hydrogen atoms in R 1 , R 2 , and R 3 may be substituted with at least one atom selected from the group consisting of a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Often,
Y and Y ′ may be the same or different and are any one selected from the group consisting of a hydrogen atom, a methyl group, and a CH 2 Cl group,
Z and Z ′ may be the same or different and are any selected from the group consisting of an oxygen atom, a sulfur atom, and a CH 2 group,
n and n ′ may be the same or different,
n is an integer of 0 to 15 when Z is an oxygen atom, and 0 when Z is a sulfur atom or a CH 2 group,
n ′ is an integer of 0 to 15 when Z ′ is an oxygen atom, and 0 when Z ′ is a sulfur atom or a CH 2 group. )

(Where
R 4 is an alkylene group having 2 to 4 carbon atoms in total,
R 5 is a hydrocarbon group having 1 to 21 carbon atoms,
R 6 and R 7 may be the same or different and each is a hydrocarbon group having 4 to 21 carbon atoms;
Here, at least part of the hydrogen atoms in R 4 , R 5 , R 6 and R 7 may be substituted with a fluorine atom, a chlorine atom, a bromine atom or an iodine atom,
S, S ′, and S ″ may be the same or different and are any one selected from the group consisting of a hydrogen atom, a methyl group, and a CH 2 Cl group,
T and T ′ may be the same or different and are any one selected from the group consisting of an oxygen atom, a sulfur atom, and a CH 2 group,
P and P ′ may be the same or different,
P is an integer of 0 to 15 when T is an oxygen atom, and 0 when T is a sulfur atom or a CH 2 group,
P ′ is an integer of 0 to 15 when T ′ is an oxygen atom, and is 0 when T ′ is a sulfur atom or a CH 2 group,
Q is an integer from 0 to 15. )
The additive for drilling mud according to any one of claims 1 to 2, wherein the viscosity of a 2% aqueous solution at 20 ° C is 10 to 100,000 mPa · s.
Drilling mud composition comprising the drilling mud additive according to any one of claims 1 to 3, an inorganic mud and water.
A ground excavation method characterized by excavating the ground in the presence of the drilling mud composition according to claim 4.
The ground excavation method according to claim 5, including a step of carrying out excavation waste to the ground using the excavation mud composition.
The ground excavation method according to claim 5 or 6, wherein a well is excavated.
The ground excavation method according to any one of claims 5 to 7, wherein the ground on the seabed is excavated.