Lubricant compositions

Abstract

Lubricant compositions for water-based drilling fluids with improved stability and environmental compatibility comprise a product obtained by reacting a hydroxyalkyl amine with a saturated or unsaturated aliphatic monocarboxylic acid and ethylene oxide; a lubricant chosen among fatty acids and ester thereof, estolides, sulfurized fatty derivatives and natural oils; a sorbitan ester of a saturated or unsaturated aliphatic monocarboxylic acid 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 of the invention comprise: a product obtained by reacting a hydroxyalkyl amine with a saturated or unsaturated aliphatic monocarboxylic acid and ethylene oxide; a lubricant chosen among fatty acids and esters thereof, estolides, sulfurized fatty derivatives and natural oils; a sorbitan ester of a saturated or unsaturated aliphatic monocarboxylic acid 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 differential pressure, 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 stability under pressure of hollow glass beads and problems in disperse 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 weighting agent, which then sinks to the bottom of the mud pit, and is lost from the fluid system. The resulting loss of fluid density may cause blow out of the well. When 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 water-based 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 concentrated lubricant compositions comprising a product obtained by reacting a hydroxyalkyl amine with a saturated or unsaturated C6- C30 aliphatic monocarboxylic acid and ethylene oxide; a lubricant chosen in the group consisting of fatty acids, estolides, sulfurized fatty derivatives and natural oils; a sorbitan ester of a saturated or unsaturated C6-C30 aliphatic monocarboxylic acid and a solvent do not grease or cheese out in the presence of mono, or multivalent cations in waterbased 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 5wt% 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 hydroxyalkylamine. 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 composition 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 waterbased drilling fluids that are substantially free of oil phase, or even free of oils.

[0018] With the expression "drilling fluid substantially free of oil phase", we mean a drilling fluid that does not contain any oil phase or contains a limited amount (typically less than 4% by volume) of oils deriving from the additives commonly used in the field.

[0019] With the expression "drilling fluid free of oils" we mean a drilling fluid that does not contain any oil phase or contains a negligible amount (typically less than 2% by volume) of oils deriving from the additives commonly used in the field.

[0020] In the present text, unless otherwise specified, the weight / volume ratio is expressed in gram / 100 ml, equivalent to 3.5 pound / barrel (ppb).

[0021] DESCRIPTION OF THE INVENTION

[0022] It is therefore an object of the present invention a lubricant composition comprising, based on the weight of the composition: a) from 15 to 40 % by weight (wt%), preferably from 20 to 35 wt%, of a product A obtained by reacting from 0.8 to 1.2 moles of a hydroxyalkyl amine of Formula (I): wherein:

[0023] R is C2-C4 alkylene,

[0024] 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 8 to 35 wt%, preferably from 10 to 30 wt%, more preferably from 10 to 25 wt%, of a lubricant B chosen in the group consisting of fatty acids and esters thereof, estolides, sulfurized fatty derivatives, natural oils and mixtures thereof; c) from 5 to 30 wt%, preferably from 8 to 25 wt%, more preferably from 8 to 20 wt%, of a sorbitan ester C, optionally ethoxylated, of a saturated or unsaturated C6-C30 aliphatic monocarboxylic acid; d) from 30 to 70 wt%, preferably from 35 to 60 wt%, of a solvent D chosen among mutual solvents, mineral oils, synthetic hydrocarbon solvents and mixtures thereof.

[0025] It is further object of the present invention a water-based drilling fluid, which is preferably a drilling fluid substantiallyfree of oil phase, orfree of oils, and more preferably which is a brine water-based drilling fluid substantially free of oil phase, or free of oils, comprising:

[0026] A) a continuous aqueous phase;

[0027] B) from 0.1 to 10 g / 100 ml, preferably from 0.3 to 5.0 g / 100 ml, of said lubricant composition, based on the total fluid volume.

[0028] A further object of the present invention is a method for drilling a subterranean formation comprising

[0029] I) providing said water-based drilling fluid;

[0030] II) drilling the subterranean formations in the presence of said water-based drilling fluid, wherein the drilling fluid has improved lubricity. DETAILED DESCRIPTION OF THE INVENTION

[0031] The product A of the lubricant composition of the invention is obtained by reacting a hydroxyalkyl amine of Formula (I) with a saturated or unsaturated C6-C30 aliphatic monocarboxylic acid, preferably C10-C24, and ethylene oxide.

[0032] 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 $- C30, preferably C10-C24, aliphatic monocarboxylic acid.

[0033] 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 amidation / esterfication product obtained in the first step is reacted with ethylene oxide.

[0034] 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.

[0035] Examples of hydroxyalkyl 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.

[0036] Preferably, the hydroxyalkyl amine of Formula (I) is triethanolamine or aminoethyl ethanol amine.

[0037] 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.

[0038] Examples of C6-C30 aliphatic saturated monocarboxylic acids include decanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, and the like.

[0039] In a preferred embodiment, the C6-C30 monocarboxylic acid is a C10-C24 saturated or unsaturated aliphatic monocarboxylic acid.

[0040] In another preferred embodiment, the C6-C30 monocarboxylic acid is a mixture of C6- C30 saturated and / or unsaturated aliphatic monocarboxylic acids. Mixtures of 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.

[0041] Mixtures of saturated and unsaturated aliphatic C6-C30 monocarboxylic acids obtained as by-product in the process of the biodiesel production are also suitable.

[0042] The preparation process of the product A comprises two reactions: ethoxylation and amidation and / or esterification. Both reactions can be conducted according to procedures well known in the art. Additional information about the preparation of these products can be found in WO 2022 / 090283.

[0043] Lubricant B is a lubricant chosen in the group consisting of fatty acids, estolides, sulfurized fatty derivatives, natural oils and mixtures thereof. These lubricants are well known in the art.

[0044] Fatty acid useful as lubricant B are those described above for the preparation of the product A. Oleic acid and lauric acid are preferred. Acid oils and fatty acid distillates, which are by-products from the production / refining of edible oils and fats, are also suitable for the realization of the present invention.

[0045] Suitable fatty esters are obtained by reaction of the fatty acids mentioned above and C C10 alcohols, such as methanol, ethanol, propanol, butanol and 2-ethyhexyl alcohol or polyols such as propylene glycol, neopentyl glycol, glycerol, trimethylol propane, 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.

[0046] Estolides are a class of long-chain esters formed by hydroxy fatty acids by reaction of at least two molecules 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 as 9,10-di hydroxy stearic acid. Polyricinoleic acid is the preferred estolide.

[0047] Sulfurized fatty derivatives 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 or a fatty oil or mixtures thereof. The sulfurized fatty derivatives are prepared by heating fatty raw materials with elemental sulfur at temperatures ranging from 65°C to about 200°C. In addition to the above-described reagent, the reaction mixture may also include sulfurization promoters such as phosphorous-containing reagents.

[0048] Unsaturated fatty acids are preferred for the preparation of sulfurized fatty acid derivatives, such as oleic acid, linoleic acid, elaidic acid, erucic acid, brassidic acid, tall oil fatty acids and the like. Sulfurized oleic acid is preferred.

[0049] Another well-known class of sulfurized fatty derivatives are the sulfurized unsaturated mono-esters of fatty acids, such as sulfurized methyl oleate.

[0050] Examples of suitable sulfurized fatty oils are sulfurized soybean, sunflower, cottonseed, high erucic rapeseed, canola and lard oils.

[0051] 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 selected from sunflower oil, safflower oil, corn 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.

[0052] Any sorbitan ester of a saturated or unsaturated C6-C30 aliphatic monocarboxylic acid commonly used in the field is suitable for as sorbitan ester C in the lubricant composition of the invention.

[0053] The saturated or unsaturated C6-C30 aliphatic monocarboxylic acid suitable for the preparation of the sorbitan ester of the invention can be chosen among those described above. Preferably, the saturated or unsaturated C6-C30 aliphatic monocarboxylic acid is a saturated or unsaturated C10-C24 aliphatic monocarboxylic acid.

[0054] The sorbitan ester C can be a sorbitan mono-, di- or tri-ester of a saturated or unsaturated C6-C30 aliphatic monocarboxylic acid or a mixture thereof.

[0055] Specific exam pies of sorbitan esters that can be employed in these compositions include sorbitan monolaurate, sorbitan monomyristate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate, sorbitan dilaurate, sorbitan distearate, sorbitan dioleate, sorbitan tristearate, sorbitan trioleate and the like. Preferred sorbitan esters are sorbitan monostearate, sorbitan monooleate, sorbitan dioleate and sorbitan trioleate. According to the invention, the sorbitan ester C can be ethoxylated. The average number of ethylene oxide units present in each sorbitan ester molecule may be in the range of from 5 to 40, preferably in the range from 10 to 30, more preferably in the range from 15 to 25. Specific examples of ethoxylated sorbitan ester of a saturated or unsaturated C6-C30 aliphatic monocarboxylic acid include ethoxylated sorbitan monolaurate, ethoxylated sorbitan monopalmitate, ethoxylated sorbitan monostearate, ethoxylated sorbitan monooleate, ethoxylated sorbitan tristearate and ethoxylated sorbitan trioleate. Preferred ethoxylated sorbitan esters are ethoxylated sorbitan monooleate and ethoxylated sorbitan trioleate.

[0056] Preferably, the sorbitan ester C is ethoxylated.

[0057] The lubricant composition of the invention also comprises a solvent D chosen among mutual solvents, mineral oils, synthetic hydrocarbon solvents and mixture thereof.

[0058] With the expression "mutual solvent", we mean a 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 acid-based 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 low degree of solubilization may be preferable.

[0059] Illustrative examples of mutual solvents include C1-C6 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-methoxyethanol, 2- propoxyethanol, 2-ethoxyethanol, 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.

[0060] The mutual solvent is preferably selected from the group which consists of C1-C6 alcohols, glycols, polyglycols, glycol ethers and mixtures thereof. More preferred mutual solvents are polyglycols, glycols ethers and mixtures thereof. Glycol ethers and mixtures thereof are the most preferred.

[0061] Particularly suitable for the realization of the present inventions are polyglycol and glycol ether bottoms, which are mixtures of polyglycols and glycol ethers obtained as byproduct 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 triethylene glycol monobutyl ether bottoms (BTG-Bottoms).

[0062] 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), paraffinum liquidum, and liquid petroleum.

[0063] Specific examples of suitable mineral oils include, but are not necessarily limited to, ESCAID®, and EXXSOL®, mineral oils available from ExxonMobil Chemical, SPI RDANE®, mineral oils available from TotalEnergies, and similar products from other mineral oil manufacturers. Specific examples of suitable mineral oils are Exxsol D110, Escaid 110, Exxsol D60 and Spirdane D 60 HL. Examples of synthetic hydrocarbon solvents are synthetic isoparaffins, such as ISOPAR® solvents available from ExxonMobil Chemical.

[0064] In one embodiment of the invention, the solvent D is a mixture of a mutual solvent and a mineral oil or a synthetic hydrocarbon solvent.

[0065] In another embodiment the solvent D is a mutual solvent or a mixture of mutual solvents. 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.

[0066] It is a particular object of the present invention a diluted lubricant composition obtained by diluting with water a lubricant composition comprising: a) from 15 to 40 wt%, preferably from 20 to 35 wt%, of a product A obtained by reacting from 0.8 to 1.2 moles of a hydroxyalkyl amine of Formula (I): wherein:

[0067] R is C2-C4 alkylene,

[0068] 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 8 to 35 wt%, preferably from 10 to 30 wt%, more preferably from 10 to 25 wt%, of a lubricant B chosen in the group consisting of fatty acids and esters thereof, estolides, sulfurized fatty derivatives, natural oils and mixtures thereof; c) from 5 to 30 wt%, preferably from 8 to 25 wt%, more preferably from 8 to 20 wt%, of a sorbitan ester C, optionally ethoxylated, of a saturated or unsaturated C6-C30 aliphatic monocarboxylic acid; d) from 30 to 70 wt%, preferably from 35 to 60 wt%, of a solvent D which is a mutual solvent selected from the group which consists of C1-C6 alcohols, glycols, polyglycols, glycol ethers and mixtures thereof; in a ratio by weight composition / water ranging between 4:1 and 1:2, preferably between 3:1 and 1:1.5.

[0069] The concentrated lubricant composition of the invention can be prepared by simply mixing under stirring the ingredients a)-d).

[0070] The inventive lubricant compositions can be used to prepare water-based drilling fluids with improved stability and environmental compatibility.

[0071] It is a further particular object of the invention a water-based drilling fluid, comprising: A') a continuous aqueous phase;

[0072] B') from 0.1 to 10 g / 100 ml, based on the total fluid volume, of said diluted lubricant composition.

[0073] In a preferred embodiment, the water-based drilling fluid contain less than 5 % by volume of oil phase. In a more preferred embodiment, the water-based drilling fluid is substantially free of oil phase, or even free of oils.

[0074] 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 oils are the particularly preferred water-based drilling fluids.

[0075] The lubricant compositions here disclosed are especially useful to avoid cheesing and greasing of brines and especially of heavy brines.

[0076] 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 f I uid5. A heavy brine is a brine having a density ranging between 1.0 and 2.7 kg / l, preferably between 1.1 and 2.6 kg / l. 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. The concentration of salt in the brine of the invention usually ranges between 3.5% (typical concentration of seawater) and 28%. The aqueous phase is chosen considering several factors including cost, environmental and health safety profile, density and availability.

[0077] The water-based drilling fluid can further comprise one or more suitable additives.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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 water-based drilling fluid into the subterranean formation. In embodiments, the bridging agent may include calcium carbonate, suspended salts, oil-soluble-resins, or combinations thereof.

[0082] 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 by-products of hexamethylenediamine purification and their salts; partially hydrolyzed (meth)acrylamide copolymers (PHPA) and their cationic derivatives; dialkyl aminoalkyl (meth)acrylate / (meth)acrylamide copolymers; quaternary ammonium compounds; cationic polyvinyl alcohols; and mixtures thereof.

[0083] 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.

[0084] EXAMPLES

[0085] The following ingredients were used for the preparation of the lubricant compositions:

[0086] • TOFA-TEA = product obtained by reacting 1 mole of Triethanol Amine with 1 mole of Tall Oil Fatty Acids and 20 moles of Ethylene Oxide;

[0087] • COCO-TEA = product obtained by reacting 1 mole of Triethanol Amine with 1 mole of Coconut Oil Fatty Acids and 20 moles of Ethylene Oxide;

[0088] • SMO-EO = Ethoxylated (20 EC) Sorbitan Monooleate;

[0089] • STO-EO = Ethoxylated (20 EC) Sorbitan Trioleate;

[0090] • SOA = Sulfurized Oleic Acid;

[0091] • TO FA = Tall Oil Fatty Acid;

[0092] • Cg-Cio FA = Cg-Cio Fatty Acids;

[0093] • PRA = Polyricinoleic Acid;

[0094] • SBC = Soybean Oil;

[0095] • NP-9 = Ethoxylated (9 EC) Nonyl Phenol;

[0096] • Texanol-Crude (Eastman Chemical Company)

[0097] • Escaid 110 (ExxonMobil Chemical)

[0098] • Exxsol D110 (ExxonMobil Chemical)

[0099] • BTG = Triethylene Glycol Monobutyl Ether;

[0100] • BEG = Ethylene Glycol Monobutyl Ether;

[0101] • BTG-B = Triethylene Glycol Monobutyl Ether Bottoms.

[0102] Examples 1-8

[0103] The lubricant compositions of Examples 1-8 were prepared according to the recipes listed in Table 1.

[0104] The amounts are reported as wt%. Table 1

[0105] *Comparative

[0106] 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 of Examples 1-7 in brine

[0107] The compatibility with brines and the lubricant performances of Examples 1-7 were determined on formulations prepared adding 9.0 g of lubricant compositions into 300 g of a 25 wt% CaCh brine. The formulations were homogenized by means of a Hamilton Beach Mixer. The compatibility with brines was evaluated before (BHR) and before and after (AHR) hot rolling for 16 hours at 121 °C (250 °F). The appearance of the formulations is showed in Table 2. The cheesy appearance represents a negative rating.

[0108] Table 2

[0109] Comparative The lubricant performances of the compositions of the Examples 1-7, were evaluated at 20 °C by means of a Lubricity Tester from Ofite. The motor speed was set to 60 rpm and torque to 150, 200 and 300 impounds (1 inch*pounds = 0.113 Newton*meters). The following Tables report the readings of the tester on the lubricant compositions of the Examples 1-7 before (Table 3) and after (Table 4) hot rolling.

[0110] The lubricant compositions of the Examples 1-7 show good compatibility with the brine and good lubricant performances, even after the thermal treatment. These results demonstrate that the lubricant compositions of the invention can be advantageously used in brine water-based drilling fluids.

[0111] Compatibility and lubricant performances of Example 8 in brine

[0112] The lubricant composition of Example 8 was diluted with water (Example 8a) or mineral oil (Example 8b) in a 2:1 ratio.

[0113] The compatibility with brines and the lubricant performances of Examples 8a and 8b were determined on formulations prepared adding 9.0 g of each lubricant composition into 300 g of a 25 wt% CaCh brine. The formulations were homogenized by means of a Hamilton Beach Mixer.

[0114] Table 5 reports the readings of the Lubricity Tester (setting described above) on the lubricant compositions of the Examples 8a and 8b before (BHR) and after (AHR) hot rolling at 121 °C (250 °F). Table 5

[0115] The results of Table 4 demonstrate that the lubricant composition of Example 8 may be diluted with either mineral oil or water providing in both cases homogeneous formulations having remarkable lubricant performances.

Claims

CLAIMS1) Lubricant composition comprising, based on the weight of the composition: a) from 15 to 40 by weight (wt%) of a product 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 of ethylene oxide; b) from 8 to 35 wt% of a lubricant B chosen in the group consisting of fatty acids and esters thereof, estolides, sulfurized fatty derivatives, natural oils and mixture thereof; c) from 5 to 30 wt% of a sorbitan ester C, optionally ethoxylated, of a saturated or unsaturated C6-C30 aliphatic monocarboxylic acid; d) from 30 to 70 wt% of a solvent D 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 20 to 35 wt% of said product A; b) from 10 to 30 wt% of said lubricant B; c) from 8 to 25 wt% of said sorbitan ester C, optionally ethoxylated; d) from 35 to 60 wt% of said solvent D.3) The lubricant composition of Claim 1, wherein product A is obtained by reacting from 0.8 to 1.2 moles of a hydroxyalkyl amine of Formula (I) with from 0.8 to 1.2 moles of a saturated or unsaturated C10-C24 aliphatic monocarboxylic acid and from 5 to 30 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 sorbitan ester C is an ethoxylated sorbitan ester containing an average number of ethylene oxide units of from 5 to 40 in each sorbitan ester molecule.6) The lubricant composition of Claim 1, wherein the solvent D is a mutual solvent, selected from the group which consists of C1-C6 alcohols, glycols, polyglycols, glycol ethers and mixtures thereof.7) Diluted lubricant composition, obtained by diluting with water the lubricant composition of claim 6 in a ratio by weight composition / water ranging between 4:1 and 1:2.8) Water-based drilling fluid, comprising:A) a continuous aqueous phase;B) from 0.1 to 10 g / 100 ml, based on the total fluid volume, of the lubricant composition of claim 1.9) The water-based drilling fluid of Claim 8, comprising: a) a continuous aqueous phase; b) from 0.3 to 5.0 g / 100 ml, based on the total fluid volume, of said lubricant composition.10) Water-based drilling fluid, comprising:A') a continuous aqueous phase;B') from 0.1 to 10 g / 100 ml, based on the total fluid volume, of the diluted lubricant composition of claim 7.

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