Lubricant compositions

Abstract

Lubricant compositions for water-based drilling fluids with improved stability and environmental compatibility. The lubricant compositions comprise: the compound obtained by reacting certain hydroxyalkyl amine with a saturated or unsaturated aliphatic monocarboxylic acid and ethylene oxide; a lubricant chosen among: fatty acids, esters and amides thereof, estolides, sulfurized fatty compounds and natural oils; and a solvent.

Description

[0001] LUBRICANT COMPOSITIONS

[0002] TECHNICAL FIELD

[0003] The present invention relates to lubricant compositions for water-based drilling fluids with improved stability and environmental compatibility. The lubricant compositions comprise: the compound obtained by reacting certain hydroxyalkyl amines with a saturated or unsaturated aliphatic monocarboxylic acid and ethylene oxide; a lubricant chosen among: fatty acids, esters and amides thereof, estolides, sulfurized fatty compounds and natural oils; and a solvent.

[0004] BACKGROUND OF THE ART

[0005] Various types of drilling fluids are used in operations related to the development and production of natural hydrocarbon reservoirs.

[0006] These fluids may be classified according to their fluid base into two main categories: water-based drilling fluids, also known as water-based drilling muds (WBMs), in which the carrier is an aqueous medium; and oil-based drilling fluids, also known as oil-based muds (OBMs), in which the carrier is oil.

[0007] Drilling fluids have many functions, such as removing drill cuttings from the drill area and carrying them to the surface where they can be separated. They also form a filter cake to seal the wellbore walls and prevent fluid losses. Drilling fluids additionally provide mud weights to balance the differentialpressure, cool the drill bits and impart lubricity. Different kinds of additives are used to provide these properties to drilling fluids.

[0008] Lubricants are added to drilling fluids to reduce the torque and drag caused by the friction between the drill string, the drill bit and the formation. Many types of lubricants, both in solid or liquid form, have been developed and utilized in drilling fluids.

[0009] Examples of liquid lubricants are hydrocarbons, fatty acid esters, fatty acids, surfactants, sulfur containing compounds, such as sulfurized fatty derivatives, natural oils and many other organic compounds.

[0010] Examples of solid lubricants are graphite, hollow glass beads, spherical solid particulates and polymers.

[0011] However, solid lubricants have many limitations, such as low stability under pressure of hollow glass beads and problems in dispersing the graphite in the fluids due to its high surface area. In addition, large amounts of solid lubricants are usually required to impart suitable lubricity to drilling fluids, thereby increasing the cost of production.

[0012] Liquid lubricants based on fatty acids, natural oils or derivatives thereof in the presence of monovalent or, in particular, of multivalent cation form insoluble soap which separate from the drilling fluid (“greasing out” or “cheesing”). The greasing out of the alkali metal ion soap causes severe impediments to the control of the fluid. If such greasing out occurs in drilling fluids containing weighing agents, the greasing out causes accumulation of the particles ofweighting agent, which then sink to the bottom of the mud pit, and are lost from the fluid system. The resulting loss of fluid density may cause blow out of the well. When the drilling fluid containing monovalent or multivalent cations is free of weighting agents, the resulting insoluble soap floats on the surface of the fluid in the mud pit. These insoluble soaps interfere with the separation of the cuttings from the drilling fluid, which results in the lubricant additive not being drawn up by the mud pumps and incorporated in the drilling fluid for recirculation in the wellbore for lubrication. These problems are especially pronounced in water-based drilling fluids containing salts and little or no oil phase, which would help make the lubricant and the aqueous phase more compatible.

[0013] In addition, liquid lubricants can have other drawbacks, such as difficult handling in cold weather and logistic and environmental impacts.

[0014] Despite many liquid lubricants and lubricant compositions suitable for waterbased drilling fluids have been described, a need still exists in the art for liquid lubricants that do not show the drawbacks described above.

[0015] Now, we have surprisingly found that lubricant compositions comprising: a) the compound obtained by reacting certain hydroxyalkyl amines with a saturated or unsaturated C6-C30 aliphatic monocarboxylic acid and ethylene oxide, b) a lubricant chosen in the group consisting of fatty acids, esters and amides thereof, estolides, sulfurized fatty compounds and natural oils and c) a solvent do not grease or cheese out in the presence of mono-, or multi-valent cations in water-based drilling fluids, and even in those which are substantially free of oil phase, such as in brine water-based drilling fluids free of oil phase. These compositions improve the lubricating properties of the drilling fluids resulting in greatly increased life of the rotary drilling bits and marked reduction in torque required to rotate the bit. Moreover, they greatly reduce transportation costs, simplify the logistics and environmental concerns associated with shipping large volumes of liquids and overcome the pour point issues associated with the liquid lubricants of the prior art.

[0016] As far as the Applicant knows, the lubricant compositions of the invention and their remarkable properties have never been described before.

[0017] WO 2022 / 090283 relates to a water-based subterranean treatment fluid, comprising: a continuous aqueous phase, at least 5 wt% of an internal oil phase and an emulsifying composition comprising a high HLB surfactant and a second surfactant obtained by reacting a saturated or unsaturated aliphatic monocarboxylic acid, ethylene oxide and a hydroxyalkyl amine. The technical problem of WO 2022 / 090283 concerns the stabilization of the fluid emulsion. WO 2022 / 090283 is silent about the need of avoiding the cheesing or greasing of lubricants based on fatty acids and / or natural oils or derivatives thereof within water-based subterranean treatment fluids, and particularly within drilling fluid substantially free of oil phase, such as in brine water-based drilling fluids that are substantially free of oil phase or even free of oils phase.With the expression “drilling fluid substantially free of oil phase”, we mean a drilling fluid that contains less than 5 % by volume of oil phase.

[0018] With the expression “drilling fluid free of oils phase” we mean a drilling fluid that contains a negligible amount (typically less than 3% by volume) of oil phase or does not contain any oil phase.

[0019] The expression “essentially consist of’ mean that less than 5.0 wt% of components other than those listed are added to a composition or formulation. The definition “fatty acids” indicates saturated and unsaturated aliphatic carboxylic acids from natural sources containing from 6 to 30 carbon atoms. The definition “sulfurized fatty compounds” indicates sulfurized fatty acids and esters thereof, sulfurized natural oils or sulfurized C6-C30 olefins, and mixtures thereof.

[0020] The definition “natural oils” indicates animal and vegetable fats and oils.

[0021] In the present text, unless otherwise specified, the weight / volume ratio is expressed in gram / 100 ml, equivalent to 3.5 pound / barrel (ppb).

[0022] DESCRIPTION OF THE INVENTION

[0023] It is therefore an object of the present invention a lubricant composition comprising, based on the weight of the composition:

[0024] a) from 2.0 to 30 % by weight (wt%), preferably from 2.5 to 20 wt%, more preferably from 3.0 to 15 wt%, even more preferably from 3.0 to 10.0 wt%, of a compound A obtained by reacting from 0.8 to 1.2 moles of a hydroxyalkyl amine of Formula (I):wherein:

[0025] R is C2-C4 alkylene,

[0026] X and Y are selected among H, C1-C10 alkyl, (C2-C4 alkylene)-OH or (C2-C4 alkylene)-NH2;

[0027] with from 0.8 to 1.2 moles of a saturated or unsaturated C6-C30 aliphatic monocarboxylic acid and from 5 to 30 moles of ethylene oxide;

[0028] b) from 36 to 80 wt%, preferably from 40 to 75 wt%, more preferably from 45 to 75 wt%, of a lubricant B chosen in the group consisting of fatty acids, esters and amides thereof different from compound A, estolides, sulfurized fatty compounds, natural oils, and mixtures thereof;

[0029] c) from 15 to 60 wt%, preferably from 20 to 55 wt%, of a solvent C chosen among mutual solvents, mineral oils, synthetic hydrocarbon solvents, and mixtures thereof.

[0030] It is further object of the present invention a water-based drilling fluid, which is a drilling fluid substantially free of oil phase, or free of oil phase and preferably which is a brine water-based drilling fluid substantially free of oil phase, more preferably free of oil phase, comprising:

[0031] A) a continuous aqueous phase;B) from 0.1 to 9.0 g / 100 ml of said lubricant composition, based on the total fluid volume.

[0032] A further object of the present invention is a method for drilling a subterranean formation comprising:

[0033] I) providing said water-based drilling fluid;

[0034] II) drilling the subterranean formation in the presence of said water-based drilling fluid, wherein the drilling fluid has improved lubricity.

[0035] DETAILED DESCRIPTION OF THE INVENTION

[0036] In a preferred embodiment, the sum of the compounds A, B and C represents at least 80% by weight, preferably at least 90% by weight, of the lubricating composition of the invention. Most preferably, the lubricating composition consists of the compounds A, B and C.

[0037] The compounds A of the lubricant composition of the invention are obtained by reacting a hydroxyalkyl amine of Formula (I) with from 0.8 to 1.2 moles, preferably from 0.9 to 1.1 moles of saturated or unsaturated C6-C30, preferably C10-C24, aliphatic monocarboxylic acids and from 5 to 30 moles, from 10 to 25 moles, of ethylene oxide.

[0038] According to one embodiment of the invention, the hydroxyalkyl amine of Formula (I) is first reacted with ethylene oxide and subsequently with the saturated or unsaturated C6-C30, preferably C10-C24, aliphatic monocarboxylic acid.According to another embodiment, the hydroxyalkyl amine of Formula (I) is first reacted with the saturated or unsaturated C6-C30, preferably C10-C24, aliphatic monocarboxylic acid and subsequently the ester or amidoester obtained in the first step is reacted with ethylene oxide.

[0039] Preferably, in Formula (I), R is C2 alkylene, X is H and Y is (C2 alkylene)-NH2 or R is C2 alkylene and X and Y are both (C2 alkylene)-OH.

[0040] Examples of hydroxy alkyl amines of Formula (I) are aminoethyl-ethanol amine, triethanol amine, N-methyl-diethanol amine, N-ethyl-diethanol amine, N-propyl-diethanol amine, N-butyl-diethanol amine, N,N-dimethyl-ethanol amine, N,N-diethyl-ethanol amine, N,N-diisopropyl-ethanol amine, N,N-dibutyl-ethanol amine N,N-dimethyl-isopropanol amine, and mixtures thereof Preferably, the hydroxyalkyl amine of Formula (I) is triethanolamine or aminoethyl ethanol amine, triethanolamine being the most preferred.

[0041] Examples of C6-C30 aliphatic unsaturated monocarboxylic acids suitable for the present invention include both unsaturated and polyunsaturated aliphatic carboxylic acids with from 6 to 30 carbon atoms. Examples of these acids are palmitoleic acid, oleic acid, linoleic acid, linolenic acid, arachidonic acid, and the like.

[0042] Examples of C6-C30 aliphatic saturated monocarboxylic acids include decanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, and the like.In a preferred embodiment, the C6-C30 monocarboxylic acid is a C10-C24 saturated or unsaturated aliphatic monocarboxylic acid.

[0043] In another preferred embodiment, the C6-C30 monocarboxylic acid is a mixture of C6-C30 saturated and / or unsaturated aliphatic monocarboxylic acids.

[0044] Mixtures of C6-C30 monocarboxylic acids derived from natural oils, such as coconut oil, mustard seed oil, palm oil, palm olein, soybean oil, rapeseed oil, canola oil, tall oil, sunflower oil, and mixtures thereof, are preferred. Mixtures of C6-C30 monocarboxylic acids derived from coconut oil and tailoil are particularly preferred.

[0045] Mixtures of saturated and unsaturated aliphatic C6-C30 monocarboxylic acids obtained as by-product in the process of the biodiesel production are also suitable and preferred. Acid oils and fatty acid distillates, which are by-products from the production / refining / recycling of edible oils and fats, are also suitable for the realization of the present invention.

[0046] The preparation process of the compounds A comprises two reactions: ethoxylation and esterification or concomitant esterification and amidation. Both reactions can be conducted according to procedures well known in the art. Additional information about the preparation of these compounds can be found in WO 2022 / 090283.

[0047] Lubricant B is a lubricant chosen in the group consisting of fatty acids, esters and amides thereof, estolides, sulfurized fatty compounds, natural oils and mixtures thereof. These lubricants are well known in the art.Fatty acids useful as lubricant B are those described above for the preparation of the compound A, i.e. saturated or unsaturated C6-C30 aliphatic monocarboxylic acid. Mixtures of fatty acids derived from tailoil are preferred. Suitable fatty esters are obtained by reaction of the fatty acids mentioned as lubricant B and C1-C10 alcohols, such as methanol, ethanol, propanol, butanol and 2-ethyhexyl alcohol, or polyols, such as propylene glycol, neopentyl glycol, glycerol, trimethylol propane and pentaerythritol. Specific examples of suitable fatty esters are methyl oleate, ethyl oleate, 2-ethylhexyl oleate, castor oil methyl ester, propylene glycol dicaprylate / caprate, neopentyl glycol dioleate, trimethylolpropane tricaprylate / caprate, glycerol monostearate and the like. Biodiesel is another suitable fatty ester lubricant.

[0048] Suitable fatty amides comprise a reaction product of the fatty acids mentioned as lubricant B and a primary or secondary amine.

[0049] Suitable amines have one or two alkyl or substituted alkyl groups, preferably C1-C10 alkyl, more preferably C1-C4 alkyl. Thus, suitable amines include ethylamine, isopropylamine, N,N-dimethylamine, N,N-diethylamine, N,N-diisopropylamine and the like.

[0050] In one preferred group of suitable amines, a nitrogen or oxygen atom is bonded to a carbon that is beta or gamma to the nitrogen atom of the primary or seconday amine group. In preferred primary or secondary amines, the nitrogen is attached to one C1-C10 alkyl group, preferably to one C1-C4 alkyl group, and one hydroxyalkyl group having from 2 to 6 carbons. In other preferred primaryor secondary amines, the nitrogen is attached to a hydrogen and two hydroxyalkyl groups having from 2 to 6 carbons each. Alkanolamines, which have an oxygen atom beta to the amine nitrogen, are particularly preferred. Examples of these alkanolamines include ethanolamine, isopropanol amine, diethanol amine, diisopropanol amine, N-methylethanol amine, N-methylisopropanol amine, N-ethylethanol amine, and the like, and mixtures thereof. Particularly preferred alkanolamines are diethanol amine, diisopropanol amine and N-methylethanol amine, which are economical and readily available. It is also preferred that the alkanol amines have a nitrogen functionality in addition to the one primary or secondary amino group and to the hydroxy group required by the generic name "alkanol amine;" for example, amino-alkanolamines. Examples of these alkanol amines are aminoalkylamino alkanol, such as 2-(2- aminoethylamino) ethanol.

[0051] Estolides are other ingredients useful as lubricant B. Estolides are a class of unique bio-based compounds having an oligomeric structure containing fatty acid repeat units, with secondary ester linkages on the alkyl backbone. Estolides can be free acids, esters or found within a triglyceride structure. They can be prepared, for example, by reaction a hydroxy fatty acids or unsaturated fatty acid with at least one molecule either of the same or of different acids. Examples of hydroxy fatty acid suitable for the preparation of the estolides of the invention are ricinoleic acid, lesquerolic acid, 14-hydroxy tetradecanoic acid, 10-hydroxy stearic acid, 12-hydroxy stearic acid, or dihydroxy carboxylic acids, such as9,10-dihydroxy stearic acid. Oleic acid is a suitable unsaturated fatty acid. Triglyceride estolides have been synthesized from castor and lesquerella oils. Polyricinoleic acid is the preferred estolide.

[0052] Sulfurized fatty compounds suitable as lubricant B are well known in the art. They can be prepared by reacting elemental sulfur with a fatty acid, a fatty acid ester, a natural oil or a C6-C30 olefin, or mixtures thereof. The sulfurized fatty compounds are prepared by heating these fatty raw materials with elemental sulfur at temperatures ranging from 65 to about 200 °C. In addition to the above-described reagent, the reaction mixture may also include sulfurization promoters.

[0053] Sulfurized unsaturated fatty acids, such as sulfurized oleic acid, linoleic acid, elaidic acid, erucic acid, brassidic acid, tall oil fatty acids and the like and mixture thereof, are preferred for the preparation of the lubricant composition of the invention. Sulfurized oleic acid is the most preferred.

[0054] Another well-known class of sulfurized fatty derivatives are the sulfurized mono-esters of fatty acids with a C1-C10 alcohol, such as methanol, ethanol and isooctanol. A specific example of sulfurized fatty ester is sulfurized methyl oleate.

[0055] Examples of suitable sulfurized natural oils are sulfurized soybean, sunflower, cottonseed, high erucic rapeseed, canola and lard oils.Examples of suitable sulfurized C6-C30 olefins are sulfurized alpha-olefins, such as sulfurized 1 -octadecene, 1 -hexadecene, 1 -tetradecene, 1 -dodecene and mixtures thereof.

[0056] The lubricant B of the composition of the present invention can be a natural oil. Any natural oil commonly used as lubricant can be utilized for the realization of the present invention. Suitable natural oils are, for example, vegetable oils such as sunflower oil, safflower oil, com oil, soybean oil, rapeseed oil, castor oil, coconut oil, palm oil, palm kernel oil, canola oil, linseed oil, rice oil, peanut oil, cottonseed oil, olive oil, and mixture thereof. Soybean oil and coconut oil are preferred.

[0057] In a preferred embodiment, the lubricant B is chosen in the group consisting of fatty acids and amides thereof, sulfurized fatty compounds or mixtures thereof. In a more preferred embodiments, the lubricant B comprises, or essentially consists of, or consists of, a mixture of fatty acids, and sulfurized fatty compounds.

[0058] In another more preferred embodiments, the lubricant B comprises, or essentially consists of, or consists of, a mixture of fatty acids, amides thereof and sulfurized fatty compounds.

[0059] In one particularly preferred embodiment, the lubricant B comprises, or essentially consists of, or consists of, a mixture of 15 to 25 wt% of sulfurized fatty compounds, from 75 to 85 wt% of fatty acids.In another particularly preferred embodiment, the lubricant B comprises, or essentially consists of, or consists of a mixture of from 35 to 45 wt% of fatty acids, 30 to 40 wt% of fatty acid amides and 20 to 30% sulfurized fatty compounds.

[0060] The lubricant composition of the invention also comprises a solvent C chosen among mutual solvents, mineral oils, synthetic hydrocarbon solvents and mixture thereof

[0061] With the expression "mutual solvent", we mean an amphiphilic solvent having a polar, water- soluble group attached to a nonpolar hydrocarbon chain. Mutual solvents are additives, used in oil field and well applications that are soluble in oil, water and aqueous acid-based subterranean treatment fluids, wherein they are routinely used for removing heavy hydrocarbon deposits, controlling the wettability of the contact surfaces before, during or after a treatment, and preventing or breaking emulsions. In some embodiments, the mutual solvent may be substantially completely soluble in each phase, while in other embodiments, a partial degree of solubilization may be preferable.

[0062] Illustrative examples of mutual solvents include Ci-Ce alcohols, linear or branched such as 2-propanol, methanol, n-butanol; glycols and polyglycols, such as monoethylene glycol, monopropylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, and higher; glycol ethers such as 2-methoxy ethanol, 2-propoxy ethanol, 2-ethoxy ethanol, ethylene glycol monobutyl ether, propylene glycol monobutyl ether,diethyleneglycol monomethyl ether dipropylene glycol monomethyl ether, diethylene glycol monoethyl ether, dipropylene glycol monoethyl ether, diethylene glycol monobutyl ether, dipropylene glycol monobutyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, tripropylene glycol monobutyl ether, and the like; various esters, such as ethyl lactate, propylene carbonate, butylene carbonate; water / oil-soluble ketones, acetals, ketals, pyrrolidones, and mixtures thereof.

[0063] The mutual solvent is preferably selected from the group which consists of Ci-Ce alcohols, glycols, polyglycols, glycol ethers and mixtures thereof More preferred mutual solvents are polyglycols, glycols ethers and mixtures thereof Glycol ethers, and especially triethylene glycol monobutyl ether (BTG), and mixtures thereof are the most preferred mutual solvents.

[0064] Also suitable for the realization of the present invention are polyglycol and glycol ether bottoms, which are mixtures of polyglycols and glycol ethers obtained as by-product or co-product of the production processes of polyglycols and glycol ethers. Specific examples polyglycols and glycol ether bottoms are tripropylene glycol bottoms, which are mixtures of di-, tri-, tetra- and higher propylene glycols, triethylene glycol monomethyl ether bottoms, which are mixtures of di-, tri-, tetra- and higher ethylene glycols methyl ethers, triethylene glycol monoethyl ether bottoms and tri ethylene glycol monobutyl ether bottoms (BTG-Bottoms). BTG bottoms and BTG are the most preferred mutual solvents.Mineral oils are a mixture of higher alkanes from a mineral source which are a by-product in the distillation of petroleum to produce gasoline. They chemically inert transparent colourless oils composed mainly of linear, branched, and cyclic alkanes (paraffins) of various molecular weights. Mineral oils are produced in very large quantities and are thus relatively inexpensive. Mineral oil products are typically highly refined, through distillation, hydrogenation, hydrotreating, and other refining processes or comprise additives, to have improved properties, such as viscosity, flash point, and gel point. Because of the relatively low content of aromatic compounds, mineral oils have a better environmental profile than other oils. Other names for mineral oil include, but are not limited to white oil, paraffin oil, liquid paraffin (typically a highly refined medical grade), paraffmum liquidum, and liquid petroleum.

[0065] Specific examples of suitable mineral oils include, but are not necessarily limited to, ESCAID®, and EXXSOL®, mineral oils available from ExxonMobil Chemical, SPIRE) ANE®, or KETRUL® available from Total Energies, and similar products from other mineral oil manufacturers. Specific examples of suitable mineral oils are Exxsol DUO, Escaid 110, Exxsol D60, Spirdane D 60 HL or KETRUL D100.

[0066] Examples of synthetic hydrocarbon solvents are synthetic isoparaffins, such as ISOPAR® solvents available from ExxonMobil Chemical.

[0067] In one preferred embodiment of the invention, the solvent C is a mineral oil or a synthetic hydrocarbon solvent or a mixture thereof.In another preferred embodiment of the invention, the solvent C is a mixture of a mutual solvent and of a mineral oil and / or a synthetic hydrocarbon solvent. In the preferred embodiment where the lubricant B comprise, essentially consists of, or consists of, a mixture of sulfurized fatty compounds and fatty acids, the solvent C is more preferably a mineral oil and / or a synthetic hydrocarbon solvent.

[0068] In the preferred embodiments where the lubricant B comprises, or essentially consists of, or consists of, a mixture of fatty acids, amides thereof and sulfurized fatty compounds, the solvent C is more preferably a mixture of a mutual solvent and of a mineral oil and / or a synthetic hydrocarbon solvent. This solution is particularly appreciated because the lubricant compositions so obtained can be easily diluted by the user both with water or with an organic solvent, according to its applications.

[0069] Optionally, the lubricant composition of the invention can further comprise from 0.2 to 25 wt%, preferably from 1 to 20 wt%, more preferably from 1 to 15 wt%, of a surfactant chosen among non-ionic, anionic or cationic surfactants. According to a preferred embodiment, the surfactant is a non-ionic surfactant. Suitable non-ionic surfactants include:

[0070] • polyalkoxylated, preferably polyethoxylated, saturated and unsaturated aliphatic alcohols and amines, having 8 to 24 carbon atoms in the alkyl radical, and having 1 to 100, preferably 4 to 40, alkylene oxide units;• polyalkoxylated, preferably polyethoxylated, arylalkylphenols, such as, for example, tristyrylphenol having an average degree of alkoxylation of between 8 and 80, preferably from 15 to 40;

[0071] • polyalkoxylated, preferably polyethoxylated, alkylphenols having one or more alkyl groups, such as, for example, nonylphenol or tri-sec- butylphenol, and a degree of alkoxylation of between 2 and 40, preferably from 4 to 20;

[0072] • polyalkoxylated, preferably polyethoxylated, hydroxyl-fatty acids or glycerides containing hydroxyl-fatty acids, such as, for example, castor oil, having a degree of alkoxylation of between 10 and 80;

[0073] • polyol, such as sorbitol and (poly)glycerol, esters with fatty acids or polyalkoxylated, preferably polyethoxylated, polyol esters;

[0074] • di- and tri-block copolymers, for example from alkylene oxides, for example from ethylene oxide and propylene oxide, having average molar weight between 200 and 8000 g / mol, preferably between 1000 and 4000;

[0075] • alkylpoyglycosides or polyalkoxylated, preferably polyethoxylated, alkylpolyglycoside s .

[0076] In a preferred embodiment of the invention, the lubricant composition comprises less than 4.0 wt%, preferably less than 2.0 wt%, more preferably less than 1.0 wt%, of sorbitan esters of saturated or unsaturated C6-C30 aliphatic monocarboxylic acids and ethoxylated derivatives thereof.The definition “sorbitan esters of a saturated or unsaturated C6-C30 aliphatic monocarboxylic acids” includes all the reaction products of sorbitan and saturated or unsaturated C6-C30 aliphatic monocarboxylic acids. The sorbitan esters can be a sorbitan mono-, di- or tri-esters.

[0077] Specific examples of these sorbitan esters include sorbitan monolaurate, sorbitan monomyristate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate, sorbitan dilaurate, sorbitan distearate, sorbitan dioleate, sorbitan tristearate, sorbitan trioleate and the like.

[0078] According to the invention, the ethoxylated sorbitan esters of a saturated or unsaturated C6-C30 aliphatic monocarboxylic acid are also excluded from the composition of the present invention. Specific examples of ethoxylated sorbitan ester include ethoxylated sorbitan monolaurate, ethoxylated sorbitan monopalmitate, ethoxylated sorbitan monostearate, ethoxylated sorbitan monooleate, ethoxylated sorbitan tristearate and ethoxylated sorbitan trioleate. The lubricant composition of the invention can be prepared by simply mixing under stirring the ingredients a)-c).

[0079] The inventive lubricant compositions can be used to prepare water-based drilling fluids with improved lubricity and environmental compatibility.

[0080] It is a further particular object of the invention a water-based drilling fluid substantially free of oil phase, comprising:

[0081] A’) a continuous aqueous phase;B’) from 0.1 to 9.0 g / 100 ml, preferably from 0.3 to 7.0 g / 100 ml, more preferably from 0.5 to 6.0 g / 100 ml, most preferably from 0.5 to 4.5 g / 100 ml, based on the total fluid volume, of said lubricant composition.

[0082] The aqueous phase used in the water-based drilling fluids of the present invention can be selected among fresh water, salt water, brine, municipal water, formation water, produced water, filtered water, distilled water, seawater (brine of natural origin), or combinations thereof. Brines that are substantially free of oil phase or even free of oil phase are the particularly preferred water-based drilling fluids.

[0083] The lubricant compositions here disclosed are especially useful to avoid cheesing and greasing of brines and especially of heavy brines.

[0084] Consequently, suitable brines may advantageously be heavy brines. Heavy brines, for the purposes of this application, include brines with various salts at variable concentrations that may be used to weight up a fluid,. A heavy brine is a brine having a density ranging between 1.0 and 2.7 kg / 1, preferably between 1.1 and 2.6 kg / 1. Brines generally comprise water soluble salts. Suitable water-soluble salts are sodium chloride, calcium chloride, calcium bromide, zinc bromide, sodium formate, potassium formate, sodium acetate, potassium acetate, calcium acetate, ammonium acetate, ammonium chloride, ammonium bromide, sodium nitrate, potassium nitrate, ammonium nitrate, calcium nitrate, sodium carbonate, potassium carbonate, and mixtures thereof. Theconcentration of salt in the brine of the invention usually ranges between 3.5% (typical concentration of seawater) and 28%.

[0085] The aqueous phase is chosen considering several factors including cost, environmental and health safety profile, density and availability.

[0086] The water-based drilling fluid can further comprise one or more suitable additives.

[0087] The one or more additives include rheology modifiers, weighting agents, bridging agents, shale inhibitors, fluid loss control agents, dispersing agents, corrosion inhibitors, defoaming agents, surfactants and combination thereof. The rheology modifiers increase the viscosity of the water -based drilling fluid and possibly create a flat rheology profile. This may facilitate the lifting of cuttings from the bottom of the subterranean formation to the surface during drilling of the subterranean well. Examples of suitable rheology modifiers include polysaccharides and modified polysaccharides, such as carboxymethyl cellulose or guar gum and derivatives thereof, xanthan gum, bentonites, synthetic polymers, such as polyacrylamides, and combinations thereof.

[0088] Weighting agents include finely divided solid particles that may increase the density of the water-based drilling fluid to support the sidewalls of the wellbore. Weighting agents may also increase the hydrostatic pressure of the water-based drilling fluid to reduce or prevent fluids present in the subterranean formation from flowing into the wellbore. Weighting agents can be selected from: barite,hematite, ilmenite, iron oxide, calcium carbonate, magnesium carbonate, and combinations thereof.

[0089] Bridging agents are solids that bridge across the pore throats or fractures present in the subterranean formation and reduce or prevent the leakage of the liquid phase of the drilling fluid into the subterranean formation. In embodiments, the bridging agent may include calcium carbonate, suspended salts, oil-soluble-resins, or combinations thereof.

[0090] Shale inhibitors prevent the swelling and hydration of water-sensitive subterranean formation, such as shale formations. Any shale hydration inhibitors commonly used in the field can be added to the drilling fluid of the present invention. Examples of suitable shale inhibitors are potassium salts; inorganic and organic phosphates; silicates; polyalkoxy diamines and their salts, for example those sold with the commercial name of Jeffamine®; choline derivatives; diamines, triamines, polyamines and their salts; high boiling byproducts of hexamethylenediamine purification and their salts; partially hydrolyzed (meth)acrylamide copolymers (PHP A) and their cationic derivatives; dialkyl aminoalkyl (meth)acrylate / (meth)acrylamide copolymers; quaternary ammonium compounds; cationic polyvinyl alcohols; and mixtures thereof.

[0091] To better illustrate the invention, the following examples are reported to show the effect of the lubricating composition of the invention in water-based drilling fluids.EXAMPLES

[0092] The following ingredients were used for the preparation of the lubricant compositions:

[0093] • TOFA-TEA = compound obtained by reacting 1 mole of Triethanol Amine with 1 mole of Tall Oil Fatty Acids and 20 moles of Ethylene Oxide;

[0094] Torq-Trim II Plus = N,N-bis(Hy dr oxy ethyl) Soya Amides, (Halliburton); STO-EO = Ethoxylated (20 EO) Sorbitan Trioleate;

[0095] SOA = Sulfurized Oleic Acid;

[0096] SCTO = Synthetic Crude Tall Oil;

[0097] TOP = Tall Oil Pitch;

[0098] TD-10 = Ethoxylated (10 EO) Tallow Amine

[0099] NP-9 = Ethoxylated (9 EO) Nonyl Phenol;

[0100] KETRUL D100 = Kerosene Hydrocarbon Solvent (TotalEnergies) Escaid 110 = Hydrocarbon Fluid (ExxonMobil Chemical)

[0101] BTG = Triethylene Glycol Monobutyl Ether;

[0102] Examples 1-10

[0103] The lubricant compositions of Examples 1-10 were prepared according to the recipes listed in Tables 1 and 2. The amounts are reported as wt%.Table 1

[0104]

[0105] * Comparative

[0106] Table 2

[0107]

[0108] * Comparative

[0109] The lubricant composition according to the invention are stable for 2 weeks both at low temperature (2 °C) and high temperature (75 °C).Compatibility and Lubricant Performances

[0110] The compatibility with brines and the lubricant performances of Examples 1-10 were determined on formulations prepared adding 7.5 g of lubricant compositions into 250 g of a 25 wt% CaCb brine and a 15 wt% NaCl brine. The formulations were homogenized by means of a Hamilton Beach Mixer.

[0111] The appearance of the brine formulations is reported in Tables 3 and 4. The separation and the cheesy and greasy appearance represent a negative rating. Table 3

[0112]

[0113] * Comparative

[0114] Table 4

[0115]

[0116] * Comparative

[0117] The lubricant performances of the compositions of the Examples 1-10, were evaluated at 20 °C by means of a Lubricity Tester from Ofite on the formulations described above. The motor speed was set to 60 rpm and torque to 150, 200 and 300 impounds (1 inch*pounds = 0.113 Newtommeters). The following Tables report the readings of the tester on the brine formulations ofthe Examples 1-10 in CaCE brine (Tables 5 and 7) and in NaCl brine (Table 6 and 8).

[0118] Table 5

[0119]

[0120] * Comparative

[0121] Table 6

[0122]

[0123] * Comparative

[0124] Table 7

[0125]

[0126] * Comparative

[0127] Table 8

[0128]

[0129] * ComparativeThe lubricant compositions of the invention show good compatibility with brines and good lubricant performances. These results demonstrate that these lubricant compositions can be advantageously used in different brine waterbased drilling fluids.

Claims

1.CLAIMS1) Lubricant composition comprising, based on the weight of the composition:A) from 2.0 to 30 % by weight (wt%) of a compound A obtained by reacting from 0.8 to 1.2 moles of a hydroxyalkyl amine of Formula (I):wherein:R is C2-C4 alkylene,X and Y are selected among H, C1-C10 alkyl, (C2-C4 alkylene)-OH or (C2- C4 alkylene)-NH2;with from 0.8 to 1.2 moles of a saturated or unsaturated C6-C30 aliphatic monocarboxylic acid and from 5 to 30 moles of ethylene oxide;B) from 36 to 80 wt% of a lubricant B chosen in the group consisting of fatty acids, esters and amides thereof different from compound A, estolides, sulfurized fatty compounds, natural oils and mixture thereof; C) from 15 to 60 wt% of a solvent C chosen among mutual solvents, mineral oils, synthetic hydrocarbon solvents and mixtures thereof.2) The lubricant composition of claim 1, comprising, based on the weight of the composition:A) from 2.5 to 20 wt% of said compound A;B) from 40 to 75 wt% of said lubricant B;C) from 20 to 55 wt% of said solvent C.3) The lubricant composition of claim 1, wherein compound A is obtained by reacting from 0.8 to 1.2 moles of a hydroxy alkyl amine of Formula (I) with from 0.8 to 1.2 moles of a saturated or unsaturated C10-C24 aliphatic monocarboxylic acid and from 10 to 25 moles of ethylene oxide.4) The lubricant composition of claim 1, wherein, in Formula (I), R is C2 alkylene, X is H and Y is (C2 alkylene)-NH2 or R is C2 alkylene and X and Y are both (C2 alkylene)-OH.5) The lubricant composition of claim 1, wherein the lubricant B is chosen in the group consisting of fatty acids and amides thereof, sulfurized fatty compounds, and mixture thereof.6) The lubricant composition of claim 5, wherein the solvent C is a mixture of a mutual solvent and a mineral oil or a synthetic hydrocarbon solvent.7) The lubricant composition of claim 5, wherein the solvent C is a mineral oil or a synthetic hydrocarbon solvent or a mixture thereof.8) The lubricant composition of claim 1, further comprising from 0.2 to 25 wt% of a surfactant chosen among non-ionic, anionic or cationic surfactants.9) Water-based drilling fluid substantially free of oil phase, comprising:A) a continuous aqueous phase;B) from 0.1 to 9.0 g / 100 ml, based on the total fluid volume, of the lubricant composition of claim 1.10) The water-based drilling fluid of Claim 9, comprising,A) a continuous aqueous phase;B) from 0.3 to 7.0 g / 100 ml, based on the total fluid volume, of the lubricant composition of claim 1.

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