RU2803818C2 - Lubricant composition and its use as lubricant for pipe - Google Patents

Abstract

FIELD: lubricants.

SUBSTANCE: lubricant composition containing: (i) base oil in an amount in the range from 45 to 70% of the mass in relation to the total mass of the lubricant composition; (ii) in the range from 5 to 15% of the mass of a clay-based organophilic thickener relative to the total weight of the lubricating composition, wherein the said clay-based organophilic thickener is a bentonite-based thickener that is surface treated with quaternary ammonium compounds with aliphatic hydrocarbon chains ranging from C₁₀ to C₂₄; and (iii) a solid lubricant that does not contain any heavy metals, and the specified solid lubricant is present in an amount in the range from 5 to 30% of the mass. based on the total weight of the lubricating composition and selected from natural and synthetic graphite; while the lubricating composition also contains in the range from 4 to 20% of the mass of one or more inorganic compounds based on metals of the 2nd group in relation to the total mass of the lubricant composition. Also proposed is the use of a lubricating composition as a lubricant for pipes and a threaded connection of high pressure pipes containing a seal formed from the lubricating composition.

EFFECT: lubricant composition with sufficient extreme pressure and sealing characteristics for HPHT wells.

6 cl, 3 dwg, 10 ex

Description

Field of technology

The present invention relates to a lubricating composition and the use of the lubricating composition as a pipe lubricant. The present invention also relates to a threaded connection of high pressure pipes containing a lubricant composition.

State of the art

Pipe lubricant is a term used to describe a lubricating composition (sometimes the term "grease" is used) used to make a pipe joint tight and pressure-tight. Pipe lubricant plays an important role in the casing connection system. During assembly, it must be lubricated and protected from excessive wear in the environment. Once installed in a well, the sealing surfaces must be protected from minor sliding movements due to loading and unloading or thermal effects under operating conditions. In addition, the pipe lubricant helps to plug the channels in the metal seal, improving the tightness of the casing joint. In addition to helping to seal pipe joints, pipe lubricant also acts as a lubricant, helping to prevent the pipe parts being joined from seizing and making disassembly easier.

As traditional sources of oil and gas dwindle, operators are increasingly turning their attention to unexplored or underdeveloped areas. Fields with pressures and temperatures that were thought to be higher than what was considered typical in the past are now frequently targeted for exploration and development. These fields and their associated wells are classified as high-pressure/high-temperature or HPHT.

According to the Society of Petroleum Engineers' Exploration and Production Glossary, high pressure/high temperature (HPHT) is when the undisturbed bottomhole temperature (at the expected reservoir depth or total depth) exceeds 300°F or 150°C and when the maximum expected pore pressure the pressure of the porous formation to be drilled exceeds a hydrostatic gradient of 0.8 psi (18 kPa/m), or the well requiring pressure control equipment has a rated operating pressure greater than 10,000 psi or 69 MPa .

Such conditions require special knowledge and technologies for the safe operation of fields. Known pipe lubricant, such as API HP Modified Pipe Lubricant, suitable for use in such conditions typically contains sulfur and heavy metals such as lead, zinc and/or copper.

Chemicals, such as those used in marine pipe lubricants, are classified according to a number of factors depending on local regulatory systems and requirements. Compositions containing such factors will then be classified according to the chemicals they contain. For example, the Oslo-Paris Convention (OSPAR) is a mechanism through which 15 governments along Europe's west coasts and watersheds collaborate to protect the marine environment of the Northeast Atlantic. OSPAR considers the use and discharge of hazardous substances in the offshore oil and gas industry to be a matter of serious concern. To reduce the overall impact of marine chemicals on the marine environment, OSPAR has adopted a harmonized mandatory control system (HMCS) for the use and reduction of emissions of marine chemicals. This system promotes the transition to the use of less hazardous or preferably non-hazardous substances in offshore oil and gas operations. To achieve these goals, different OSPAR member states (mainly the UK, the Netherlands, Denmark and Norway) use slightly different schemes to classify the environmental hazards and risks associated with the use and discharge of chemicals at sea.

According to the UK and Netherlands Classification of Marine Chemicals (OCNS), established by the Center for Environment, Fisheries and Aquaculture Science (CEFAS) in collaboration with the Dutch Mines Authority, products used at sea are assessed in one of two ways:

i) a risk-based approach using the CHARM Chemical Hazard and Risk Management Model (if applicable), which compares the predicted concentration of a substance in the environment with its toxic effects on organisms in the environment, resulting in a color classification result (gold, silver, white, blue, orange, purple; in order from low environmental risk to high environmental risk), or;

ii) an assessment of the inherent environmental hazard and transformation properties (potential for toxicity, biodegradation and bioaccumulation) of a substance, resulting in grouping of letter categories from A to E (with A being the most environmentally hazardous and E being the least environmentally hazardous).

In Norway and Denmark, chemicals are classified based on their inherent environmental hazard properties (potential for biodegradation, toxicity and bioaccumulation) using a color classification system (green, yellow, red and black; green chemicals are considered to pose little or no risk no risk (PLONOR) to the environment, and ferrous chemicals are considered the most dangerous to the environment).

Heavy metals such as lead, zinc and/or copper are in the most hazardous category (ferrous or category A) and therefore the use of such pipe lubricants should be kept to a minimum and preferably eliminated entirely through chemical substitution or technology " without lubricants." In addition, lead is included on the OSPAR list of priority chemicals and is subject to monitoring to ensure progress is made towards eliminating its use and possible release into the marine environment.

In light of the desire to protect both human health and the environment, as well as increasing regulatory requirements in this area, much effort has been focused on developing pipe lubricants capable of long-term effective use in HPHT conditions that have less impact on health and the environment compared to known lubricants.

For lower temperature applications, more environmentally friendly alternatives (known as "yellow" grease or "OCNS E-C" grease) are commercially available. However, OCNS Category E-C pipe lubricants generally fail at temperatures above 150°C. Compounds tend to fail due to evaporation or thermal decomposition of the base oil and/or additives. As a result, lubricity is lost and the surface becomes damaged during load cycles, resulting in leakage. To date, despite all efforts to address this issue, no alternative lubricants have been found for HPHT and super duplex drilling wells above 5,000 psi. Such a problem is discussed in Inose K, Sugino M, Goto K. Influence of Grease on High-Pressure Gas Tightness by Metal-to-Metal Seals of Premium Threaded Connections, Tribol Online 2016;11:227–34; and Nowinka J, Dall'Acqua D, New Standard for Evaluating Casing Connections for Thermal-Well Applications. SPE Drill Complet 2011;26:419–31.

Thus, there is a global need for improved, more environmentally friendly lubricant compositions suitable for use as pipe lubricants with sufficient extreme pressure and sealing properties for HPHT wells. Such formulations should be free of heavy metals and preferably have a low sulfur content.

The essence of the invention

Accordingly, the present invention provides a lubricant composition comprising:

(i) base oil

(ii) an organophilic clay-based thickener;

And

(iii) a solid lubricant, wherein said solid lubricant does not contain any heavy metals.

The present invention also provides for the use of a lubricating composition comprising: a base oil; clay-based organophilic thickener; and a solid lubricant, wherein said solid lubricant does not contain any heavy metals, as a pipe lubricant.

The present invention also provides a threaded connection of high pressure pipes containing two mating threaded elements, between which is located a high pressure seal formed from the specified lubricant composition.

Brief description of graphic materials

In fig. 1-3 show the results of the Examples provided herein.

Detailed Description of the Invention

The inventors of the present invention have unexpectedly discovered that a lubricant composition containing: a base oil; clay-based organophilic thickener; and solid lubricant, which does not contain heavy metals, effectively acts as a pipe lubricant under high pressure and high temperature conditions. This lubricant composition does not contain heavy metals and can be low or no sulfur, which greatly reduces the potential environmental impact of using such a pipe lubricant in HPHT well drilling.

As used herein, the term “heavy metals” refers to metals typically present in API HP modified pipe lubricant, particularly lead, zinc and/or copper, more specifically lead and/or copper. Preferably, the definition of “heavy metals” includes metals that fall in periods 4 to 6 and groups 9 to 12 of the Periodic Table of the Elements, as well as molybdenum, chromium, manganese, iron, indium, thallium, tin, lead, bismuth and polonium .

There are no particular restrictions on the composition of the base oil used in the present invention, and various conventional mineral oils and synthetic oils can be conveniently used. The base oil composition used in the present invention may include mixtures of one or more mineral oils and/or one or more synthetic oils.

Mineral oils for use in the lubricating composition of the present invention include any of Group I, Group II and Group III base oils. "Group I" base oil, "Group II" base oil and "Group III" base oil are defined as lube oil base oils as defined by the American Petroleum Institute (API) Category I, II and III. These API categories are defined in API Publication 1509, 15th Edition, Appendix E, April 2002.

Particularly suitable mineral oils for use in the present invention include liquid petroleum oils and solvent-treated or acid-treated mineral lubricating oils of the paraffinic, naphthenic or mixed paraffinic/naphthenic type, which can be further refined by hydrotreating and/or dewaxing processes.

Other suitable mineral oils which may conveniently be used as a base oil or a component thereof in the lubricating composition of the present invention include Fischer-Tropsch base oils such as those described, for example, in EP 0 776 959, EP 0 668 342 , Wo 97/21788, Wo 00/15736, Wo 00/14188, Wo 00/14187, Wo 00/14183, Wo 00/14179, Wo 00/08115, Wo 99/41332, EP 1 029 029, Wo 01/18156 and WO 01/57166. Such Fischer-Tropsch base oils can be obtained from any source, for example, gas in liquid, coal in liquid, biomass in liquid.

Synthetic oils that can be used in the lubricating compositions of the present invention include Group IV base oils, particularly hydrocarbon oils such as olefin oligomers (PAO), and Group V base oils such as diesters, polyol esters, dewaxed paraffin raffinate and polybutenes. Synthetic hydrocarbon base oils from the Shell Group under the designation "XHVI" (trade mark) can be conveniently used.

In a particularly preferred embodiment of the invention, the base oil is selected from oils that are biodegradable in a water-enriched environment to further enhance the favorable environmental characteristics of alternative HPHT pipe lubricants that do not contain heavy metals. “Biodegradable” in the context of this document refers to a substance in which the base lubricant of the formulation degrades by at least 60% in 28 days in the OECD301B standard test (or OECD306 test). Examples of base oils that are known to be biodegradable in a water-enriched environment include esters such as esters and polyol esters.

If a biodegradable base oil, in particular an ester base oil, is used in the lubricating composition of the present invention, it is preferred that it be used in combination with a small amount of additional solubilizing oil, preferably mineral oil, poly-alpha-olefin (PAO) or hexadecane . The minor amount of additional solubilizing oil is preferably in the range of 2 to 20% by weight, more preferably 5 to 15% by weight. based on the entire lubricant composition.

This small amount of additional solubilizing oil in combination with the ester base oil improves sealing performance when the lubricant composition is used as a pipe lubricant in a high pressure pipe threaded joint.

The total amount of base oil included in the lubricant composition of the present invention is preferably in the range of 30 to 95 wt%, more preferably in the range of 45 to 90 wt%, and most preferably in the range of 45 to 70 wt%. wt. in relation to the total mass of the lubricant composition. All percentages stated herein are expressed relative to the total weight of the lubricant composition.

The viscosity of the base oil is preferably in the range from 22 to 1500 mm ² s ^-1 (cSt) at 40°C. More preferably, it may be in the range of 100 to 1000 mm ² s ^-1 (cSt) at 40°C, and most preferably in the range of 320 to 1000 mm ² s ^-1 (cSt) at 40°C.

The clay-based organophilic thickener is suitably selected from clays modified by treatment with surfactants. Said clays are preferably montmorillonites, and most preferably the clay-based organophilic thickener is a bentonite-based thickener.

The thickener is preferably surface treated so that it is dispersed in hydrocarbon or alternative base fluids. This treatment can be carried out with quaternary ammonium compounds with aliphatic hydrocarbon chains in the range from C ₁₀ to C ₂₄ , in particular in the range from C ₁₂ to C ₁₈ .

The thickener is also suitably activated during production of the lubricant. Water, methanol, ethanol, acetone, propylene carbonate, or mixtures of two or more of these can be used as activators to break the adhesion between layers of thickener particles, allowing them to then separate under shear, increasing the surface area of the thickener and its thickening ability.

The clay-based organophilic thickener is preferably present in an amount of at least 5% by weight, more preferably at least 7% by weight. based on the total mass of the lubricant composition. The clay-based organophilic thickener is preferably present in an amount of no more than 20% by weight, more preferably no more than 15% by weight. of the total mass of the lubricant composition.

The activator concentration can be in the range from 0.1 to 5 wt%. based on the total mass of the lubricant composition. In particular, it is possible to use an activator concentration in the range from 0.5 to 2% by weight.

The solid lubricant does not contain heavy metals and is preferably selected from the group of inorganic compounds that are crystalline at room temperature and have crystalline structures that allow slip under high shear conditions. Preferred solid lubricants that do not contain any heavy metals include graphite, in particular natural or synthetic graphite. Preferably, the solid lubricant, free of any heavy metals, used in the lubricating composition includes natural or synthetic graphite. Most preferably, the solid lubricant, which does not contain any heavy metals, is natural or synthetic graphite.

To enable such solid lubricants to be used for this application, they are preferably finely divided with an average particle size in the range of 0.1 to 100 microns.

Preferably, the solid lubricant is present in an amount ranging from 5 to 30% by weight. based on the total mass of the lubricant composition.

In a preferred embodiment, the lubricant composition also contains one or more inorganic compounds based on Group 2 metals.

For the one or more Group 2 metal-based inorganic compounds, the Group 2 metal is preferably selected from calcium and magnesium. Most preferably, the Group 2 metal is calcium.

Preferably, the one or more inorganic Group 2 metal compounds is selected from the group consisting of one or more of calcium carbonate, calcium sulfate, calcium hydroxide, calcium oxide and calcium phosphate. Most preferably, the one or more Group 2 mineral inorganic compounds is calcium phosphate.

Preferably, the one or more inorganic Group 2 metal compounds is a fine powder with an average particle size in the range of 0.1 to 100 microns.

If present, one or more inorganic Group 2 metal compounds are present in amounts ranging from 4 to 20% by weight. based on the total mass of the lubricant composition.

Optionally, regardless of whether the lubricant composition contains a Group 2 mineral inorganic compound, the lubricant composition may contain a melamine-based flame retardant powder.

Powdered melamine-based flame retardant can be based on melamine alone or in the form of a complex with an acid. Suitable acids include cyanuric acid, phosphoric acids to form, for example, melamine phosphate, pyrophosphate or polyphosphate, and boric acid to form melamine borate. A mixture of melamine-acid complexes can also be used. A particularly preferred melamine-based flame retardant powder is melamine cyanurate.

Melamine cyanurate is also known as melamine-cyanuric acid adduct or melamine-cyanuric acid complex and is a crystalline complex formed from a 1:1 mixture of melamine and cyanuric acid.

If present, the melamine-based flame retardant powder is suitably present in an amount of 4 to 15 wt%. based on the total mass of the lubricant composition.

Also optionally, and possibly in addition to any powdered melamine-based flame retardant and/or inorganic Group 2 metal compound, the lubricant composition may contain one or more polymers selected from those that are solid at room temperature and pressure.

If present, one or more polymers suitable for use in the lubricant composition are selected from those that are solid at room temperature and pressure. Preferred polymers are selected from the group consisting of polyalkenes (simple or copolymers), polyamides, polystyrene, polycarbonate and polyoxymethylene. More preferably, the one or more polymers are selected from one or more polyamides.

Polyamide is a polymer reaction product of a diamine and a dicarboxylic acid. Preferred polyamides are aliphatic polyamides. More preferably, the carbon chain lengths of the diamine and dicarboxylic acid used to form the polyamide may be selected from C ₂ to C ₁₂ . The total final molecular weight of the polyamide is preferably in the range from 20,000 to 50,000. Copolymers using more than one diamide or diacid are also possible.

Without wishing to be bound by theory, it is believed that suitable polymers are polymers that deform but do not melt at the temperatures and pressures found in HPHT wells.

If present, the polymers used in the lubricant composition are preferably finely divided, with an average particle size ranging from 0.1 to 100 microns.

If present, one or more polymers suitable for use in the lubricant composition are suitably present in an amount of from 4 to 15% by weight. based on the total mass of the lubricant composition.

The present invention is further described below with reference to the following examples, which are not intended to limit the scope of the present invention in any way.

Examples

We tested lubricants for pipes using the following recipes. All % given in the Examples are % by weight. based on the total mass of the lubricant composition.

Example 1 (comparative). Existing black grease or OCNS Category A grease (modified API)

Aluminum complex soap 6% Paraffinic base oil ISO VG100 (SN500) 31% Lead powder thirty% Graphite powder 18% Zinc powder 12% Copper powder 3%

This is an existing high pressure/high temperature pipe lubricant. It is classified as Category A by OCNS and has a replacement warning by UK OCNS (according to the Center for Environment, Fisheries and Aquaculture Science (CEFAS) Definitive Ranked Lists of Registered Products) and is classified as "black" for potential applications in the Norwegian marine area .

Example 2A (comparative)

Example 2A used Jet-Lube HPHT Pipe Lubricant, a commercially available yellow OCNS Category E pipe lubricant. According to the material safety data sheet and other available information, this lubricant contains:

Calcium fluoride 25 – 35% Calcium sulfate 5 – 10% Graphite 13% Calcium carbonate 13% Base oil (synthetic PAO/ester) remainder

Example 2B (comparative)

Example 2B used Best-o-life 4010 NM pipe lubricant, a commercially available OCNS Category E pipe lubricant/yellow pipe lubricant. According to the material safety data sheet and other available information, this lubricant contains:

Light naphthenic base oil 30 - 50% Graphite 10 – 20% Talc 5 – 10% Calcium carbonate 5 – 10% Calcium acetate 5 – 10% Calcium fluoride 5 – 10% Dolomite 15% Titanium dioxide 15% Calcium oxide 15% Quartz 0.1 – 1%

Example 2C (comparative)

Example 2C used SOCO Enviro1 pipe lubricant, a commercially available OCNS Category E pipe lubricant/yellow pipe lubricant. According to the material safety data sheet and other available information, this lubricant contains:

Synthetic ester

Mineral fillers

The greases used in Examples 2A, 2B and 2C are existing commercial greases that have been registered and classified as OCNS Category E/Yellow under the UK and Norwegian OSPAR schemes, respectively.

The following examples (according to the invention) with the compositions set out below were also compiled. Graphite powder is an example of a solid lubricant that does not contain any heavy metals. 10 micron polyamide is an example of a polymer that is solid at room temperature. Calcium phosphate powder is an example of an inorganic compound based on a Group 2 metal. Treated bentonite is an organophilic clay-based thickener.

Example 3A (according to the invention)

Processed bentonite 10% Mineral base oil ISO VG460 60% Graphite powder 15% Powdered Melamine Cyanurate 15%

Example 3B (according to the invention)

Processed bentonite 10% Mineral base oil ISO VG460 60% Calcium Phosphate Powder 10% Graphite powder 10% Powdered Melamine Cyanurate 10%

Example 3C (according to the invention)

Processed bentonite 10% Mineral base oil ISO VG460 60% Calcium Phosphate Powder 15% Graphite powder 15%

Example 3D (according to the invention)

Processed bentonite 10% Mineral base oil ISO VG460 60% Calcium Phosphate Powder 10% Graphite powder 10% Polyamide 10 micron 10%

Example 3E (according to the invention)

Processed bentonite 10% Mineral base oil ISO VG460 60% Calcium Phosphate Powder 10% Graphite powder 10% Polyamide 5 micron 10%

Example 3F (according to the invention)

Processed bentonite 10% Ester base oil (e.g. Radialube 7257) 50% Graphite 15% Mineral oil 15% Calcium phosphate 10%

The lubricants have passed a number of industry recognized tests. The rationale for the tests used is that loss of lubricity due to base oil evaporation and failure to form a lubricating film results in surface damage and subsequent leakage of metal-to-metal seals.

A) The evaporation tendency was tested by thermogravimetric analysis (TGA). The protocol involves ramping the temperature from ambient temperature (25°C) to 250°C at a temperature increase rate of 1°C/min, followed by a waiting period of 30 minutes at 250°C. At the end of the waiting time, another temperature change was made from 250°C back to room temperature.

The relative mass loss results of TGA are shown in FIG. 1. A wide range of mass losses is observed. Weight loss occurs primarily due to evaporation of the base oil. Phase transitions and/or oxidation were then observed using differential scanning calorimetry (DSC). In general, all OCNS E-C greases (a classification assigned based on preliminary analysis of available environmental performance data) show early onset of evaporation due to the relatively light oils used compared to modified APIs. It is clear that the Examples according to the invention show the lowest evaporation losses.

The pin-on-disk test is designed to investigate the slip during make-up parallel to the cutting direction. In addition, the relatively short stroke length provides insight into the behavior of the lubricant during microshear. The applied contact stresses are equivalent to the stresses in a metal-to-metal seal of a superior quality joint. The tests were carried out using a steel ball (AISI52100) with R = 5 mm against a hardened and tempered steel disc (AISI4130). The ball is polished and has a surface roughness S _a = 0.01 µm and a surface hardness of 700 HV. The disk is made by polishing and has a surface roughness S _a = 0.01 μm and a surface hardness of 320 HV.

Pin-to-disc tests were performed at a maximum Hertzian contact stress of 1 GPa with a normal load of 10 N applied. The contact patch diameter at this voltage is approximately 140 μm. The specified reciprocating sliding length is 500 μm at a frequency of 0.5 Hz. At 1500 cycles the equivalent sliding length is 1500 mm. Every 250 cycles, the cyclicity was stopped, the ball was slightly raised above the surface, after which the temperature was increased stepwise. After reaching the new set temperature, the test was continued for another 250 cycles. The temperature sequence was repeated for steps 30-70-100-150-200-250°C. Before each experiment, the lubricant was applied once with a cotton swab to the surface of the disk and pin.

The additives of the invention (3A, 3B, 3C, 3D, 3E and 3F) were compared with comparative examples 1, 2A, 2B and 2C. The results of tribological stability tests at high temperatures are shown in FIG. 2. In FIG. 2, the bars indicate the average coefficient of friction (CoF), the error bars indicate the 1-sigma change in CoF (denoted as StDev) during the test, and the dots indicate the maximum observed CoF (denoted as CoF _max ). Low and stable CoF directly correlates with low or no surface damage and overall good performance. It is clear that the lubricants of the invention exhibit more consistent friction characteristics compared to the comparative OCNS Category E/yellow lubricants (Examples 2A, 2B and 2C). The greases of the invention also show lower and more stable CoF compared to the HPHT grease (Example 1).

Without wishing to be bound by theory, it is postulated that the success of the lubricants of the present invention may be due to the formation of a durable film. The film will protect the metal-to-metal seal surface long after the lubricant has lost its base oil. This does not occur for the other (comparative) OCNS Category E greases in the comparison and is consistent with the results from Example 1.

Finally, a strip test was used for contact stresses and sliding velocities equivalent to those in a metal-to-metal seal. Strip tests were carried out using a steel (P110) support against a steel (P110) strip. The support was machined and had a surface roughness S _a = 1.6 μm and a surface hardness of 320 HV. The strip had a relief caused by cutting with a cutting element in the sliding direction, and had a surface roughness S _a = 1.6 μm and a surface hardness of 320 HV. These surface properties are common for casing joints.

The tests were carried out at a maximum Hertzian contact stress of 1.4 GPa when a normal load of 20 kN was applied. During the first 5 strokes, a linear load change was applied. The contact patch was elliptical and approximately 5.7 mm × 1.1 mm. The sliding speed was 25 mm/s. Up to 50 strokes were made with a sliding length of 31 mm.

The results are shown in Fig. 3. In FIG. 3 summary statistics cover 50 moves. The bars indicate the average coefficient of friction (CoF), the error bars indicate the 1-sigma change in CoF (denoted as StDev) during the test, and the dots indicate the maximum observed CoF (denoted as CoF _max ). Abrasion was observed in both Example 1 and Example 2C. For Example 3B, no abrasion was observed. Compared to Example 2C, Example 3B of the invention exhibited superior machined surface to machined surface P110 friction performance under make-up conditions. Similar performance is demonstrated when compared to Comparative Example 1.

Examples of the invention demonstrate excellent lubrication characteristics and good thermal stability even under HPHT conditions without the presence of heavy metals previously required for pipe lubricants for this application. It is believed, without wishing to be bound by theory, that even when the base oil present in the formulations evaporates, the remaining components form a film with good sliding characteristics.

Claims (10)

1. Lubricant composition containing: (i) base oil in an amount ranging from 45 to 70% by weight. in relation to the total mass of the lubricant composition; (ii) in the range from 5 to 15 wt%. of an organophilic clay-based thickener relative to the total weight of the lubricant composition, wherein said organophilic clay-based thickener is a bentonite-based thickener that is surface treated with quaternary ammonium compounds with aliphatic hydrocarbon chains ranging from C ₁₀ to C ₂₄ ; And (iii) a solid lubricant, wherein said solid lubricant does not contain any heavy metals, wherein said solid lubricant is present in an amount ranging from 5 to 30% by weight. based on the total mass of the lubricant composition and selected from natural and synthetic graphite; Moreover, the lubricant composition also contains in the range from 4 to 20 wt.%. one or more inorganic compounds based on group 2 metals relative to the total mass of the lubricant composition. 2. The lubricant composition according to claim 1, characterized in that one or more inorganic compounds based on group 2 metals includes calcium phosphate. 3. The lubricating composition according to claim 1 or 2, characterized in that the lubricating composition also contains a powdered melamine-based fire retardant. 4. Lubricant composition according to any one of paragraphs. 1-3, characterized in that the lubricant composition also contains one or more polymers selected from those that are solid at room temperature and pressure. 5. Use of a lubricant composition according to any one of paragraphs. 1-4 as a pipe lubricant. 6. A threaded connection of high-pressure pipes containing two mating threaded elements, between which there is a high-pressure seal formed from a lubricant composition according to any one of claims. 1-4.

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