Synthesis and mechanism of environmentally friendly high temperature and high salt resistant lubricants

With the exploration and development of deep and ultra-deep oil and gas,high torque and high friction during the drilling of deep and ultra-deep wells become one of the key issues affecting drilling safety and drilling speed.Meanwhile,the high temperature and high salt problem in deep formations is prominent,which poses a major challenge to the lubricity of drilling fluids under high temperature and high salt.This paper reports an organic borate ester SOP as an environmentally friendly drilling fluid lubricant.The performance evaluation results show that when 1%lubricant SOP is added to the fresh water-based mud,the lubrication coefficient decreases from 0.631 to 0.046,and the reduction rate of lubrication coefficient is 92.7%.Under the conditions of 210℃ and 30%NaCl,the reduction rate of lubricating coefficient of the base slurry with 1%SOP was still remain 81.5%.After adding 1%SOP,the wear volume decreased by 94.11%compared with the base slurry.The contact resistance experiment during the friction process shows that SOP can form a thick adsorption film on the friction surface under high temperature and high salt conditions,thus effectively reducing the friction resistance.Molecular dynamics simulation shows that lubricant SOP can be physically adsorbed on the surface of drilling tool and borehole wall through hydrogen bond and van der Waals force.XPS analysis further shows that SOP adsorbs on the friction surface and reacts with metal atoms on the friction surface to form a chemically reactive film.Therefore,under high temperature and high salt conditions,the synergistic effect of physical adsorption film and chemical reaction film effectively reduces the frictional resistance and wear of the friction surface.In addition,SOP is non-toxic and easy to degrade.Therefore,SOP is a highly effective and environmentally friendly lubricant in high temperature and high salt drilling fluid.

Plastic-elastic Model for Water-based Lubrication Considering Surface Force

Water-based lubrication is an effective method to achieve superlubricity,which implies a friction coefficient in the order of 10−3 or lower.Recent numerical,analytical,and experimental studies confirm that the surface force effect is crucial for realizing water-based superlubricity.To enhance the contribution of the surface force,soft and plastic materials can be utilized as friction pair materials because of their effect in increasing the contact area.A new numerical model of water-based lubrication that considers the surface force between plastic and elastic materials is developed in this study to investigate the effect of plastic flow in water-based lubrication.Considering the complexity of residual stress accumulation in lubrication problems,a simplified plastic model is proposed,which merely calculates the result of the dry contact solution and avoids repeated calculations of the plastic flow.The results of the two models show good agreement.Plastic deformation reduces the local contact pressure and enhances the function of the surface force,thus resulting in a lower friction coefficient.

Tribological behaviors of graphene oxide partly substituted with nano-SiO_(2) as lubricant additives in water for magnesium alloy/steel interfaces

Although graphene oxide(GO)has emerged as an excellent lubricant additive in water,there remain great challenges in their practical application due to high production costs.By taking into account the low cost and also its excellent tribological properties,it is likely that nano-SiO_(2)can be used as a lubricant additive to partially replace GO.Hence,this paper aims to explore the tribological properties of nano-SiO_(2)incorporated in GO nanofluids for partial GO replacement by investigating the friction coefficient and wear volume of the prepared SiO_(2)/GO hybrid nanofluids for magnesium alloy/steel sliding pairs.The experiments reveal that the SiO_(2)/GO hybrids retain low friction coefficients as compared to individual GO or SiO_(2)at all test conditions in this study.However,as for the bearing capacity test,all samples can provide a low wear volume under the loads of 1 and 3 N.With the increase of the normal load,there is considerable differences in the anti-wear behavior.Compared with that of individual GO nanofluids,the wear volume of the GO/SiO_(2)(mass ratio of 0.3:0.2)hybrid nanofluids was reduced by50.5%at 5 N and by 49.2%at 8 N.Furthermore,the wear volume of the GO/SiO_(2)(mass ratio of 0.3:0.2)hybrid nanofluids was reduced by46.3%under the rigorous conditions,as compared to individual GO nanofluids.The findings provide new insights into developing carbon nanomaterial-based hybrid nanofluids for magnesium alloy formation.

Tribological performance of various metal-doped carbon dots as water-based lubricant additives and their potential application as additives of poly(ethylene glycol)

Advances in nano-lubricant additives are vital to the pursuit of energy efficiency and sustainable development.Carbon dots(CDs)have been widely investigated in the domain of lubricant additives owing to their extraordinary tribological properties,in particular,their friction-reducing and anti-wear properties.Metal-doped CDs are a new type of CDs,and their friction-reducing and anti-wear properties are attracting increasing attention.Therefore,a series of CDs doped with various divalent metal ions have been successfully synthesized via one-pot pyrolysis.The tribological properties of the synthesized CDs as water-based lubricant additives are in the following order:Zn-CDs>Cu-CDs>>Mg-CDs>Fe-CDs>U-CDs.Specifically,adding 1.0 wt%of Zn-CDs into water-based lubricant results in 62.5%friction and 81.8%wear reduction.Meanwhile,the load-carrying capacity of the water-based lubricant increases from 120 N to at least 500 N.Zn-CDs as an additive have long service life.Additionally,anion-tuned Zn-CDs fabricated via anion exchange exhibit promise as lubricant additives for poly(ethylene glycol).Based on the results of wear scar surface analyses,it is discovered that tribochemical films,primarily composed of iron oxides,nitrides,metal carbonates,zinc oxides,zinc carbonates,organic compounds,and embedded carbon cores,formed on the rubbing surfaces with a thickness of approximately 270 nm when Zn-CDs are used as additives.This film combined with the“ball-bearing”and third-particle effects of Zn-CDs contributed to excellent lubrication performance.

Liquid superlubricity of lubricants containing hydroxyl groups and their aqueous solution under rolling/sliding conditions

Macroscale rolling/sliding conditions are in the superlubricity,a little-studied topic so far.The purpose of this paper is to examine the formation of elastohydrodynamic lubrication(EHL)films by water-based lubricants(glycerol and polyethylene glycol(PEG)),providing superlubricous friction.Experiments were carried out on an optical ball-on-disc tribometer under rolling/sliding conditions.The film thickness was measured by the thin film colorimetric interferometry,and the viscosity of liquids was measured by rotational and high-pressure falling body viscometers.The results show that tribochemical reactions are not the mandatory reason for friction to reach the superlubricity level when using the water-based lubricants.The studied liquids themselves are almost Newtonian.With the addition of water,the signs of shear thinning behavior disappear even more.Suitable conditions for this type of lubricant can be predicted using the known Hamrock–Dowson equations.An anomaly in the thickness of the lubricants was observed as an abrupt change at certain conditions.The more PEG there is in the lubricant,the higher the thickness at the beginning of the jump.

Experimental Study on Friction Reducing and Anti Wear Property of a Water-Based Lubricant with Polyether Added

The wear behaviors of steel-steel pair on condition of a water-based lubricant with copolymer of acylamino polyoxyethylene polyoxypropylene ether(KE-1)included as additives are investigated with the help of the universal micro-tribotester.Tests on friction and wear are carried out.As a reference,some tests with pure water are also performed for comparison.The results show that the prepared water-based lubricant has a good effect on the characteristics associated with friction reducing and anti-wear processes,which lay some credence to its utilization in practical industrial tribo-systems.

Black phosphorus quantum dots: A new-type of water-based high-efficiency lubricant additive

Black phosphorus quantum dots(BPQDs),obtained via a typical solution-based top-down method,were used as water-based lubricant additives.BPQDs exhibited remarkable friction reduction and anti-wear properties even at the ultra-low concentration of 0.005 wt%,which reduced the friction coefficient and wear volume of the base liquid by 32.3%and 56.4%,respectively.In addition,the load-supporting capacity of the base liquid increased from 120 N to over 300 N.BPQDs-based additives exhibited a relatively long lifetime at a relatively high load of 80 N.The performance of BPQDs considerably exceeded that of the BP;this may be attributed to their small and uniform particle size,good dispersion stability in water,and high reactivity at the frictional surfaces.The results of the surface wear resistance analysis demonstrated that a robust tribochemical film with a thickness of approximately 90 nm was formed on the rubbing surface lubricated with 0.005 wt%of BPQDs dispersion.Moreover,the film served as a direct evidence of the excellent tribological performance of BPQDs.

A high-temperature resistant and high-density polymeric saturated brine-based drilling fluid

Three high-temperature resistant polymeric additives for water-based drilling fluids are designed and developed:weakly cross-linked zwitterionic polymer fluid loss reducer(WCZ),flexible polymer microsphere nano-plugging agent(FPM)and comb-structure polymeric lubricant(CSP).A high-temperature resistant and high-density polymeric saturated brine-based drilling fluid was developed for deep drilling.The WCZ has a good anti-polyelectrolyte effect and exhibits the API fluid loss less than 8 mL after aging in saturated salt environment at 200°C.The FPM can reduce the fluid loss by improving the quality of the mud cake and has a good plugging effect on nano-scale pores/fractures.The CSP,with a weight average molecular weight of 4804,has multiple polar adsorption sites and exhibits excellent lubricating performance under high temperature and high salt conditions.The developed drilling fluid system with a density of 2.0 g/cm^(3)has good rheological properties.It shows a fluid loss less than 15 mL at 200°C and high pressure,a sedimentation factor(SF)smaller than 0.52 after standing at high temperature for 5 d,and a rolling recovery of hydratable drill cuttings similar to oil-based drilling fluid.Besides,it has good plugging and lubricating performance.

Water-based lubrication of niobium nitride

Water-based lubrication has attracted wide attention as an oil-free lubrication method owing to its greener and cleaner lubrication means.However,due to operating in the water environment,most moving parts would inevitably suffer from abrasion,rusting,and aging problems.Developing a novel solid-water composite system with ultra-low friction and wear will open new possibilities for innovative lubrication material research and development.Here,we first revealed the water-based lubrication behavior of a high-hardness niobium nitride coating(NbN).In a three-phase contact environment(water,air,and NbN),oxidation and hydrolytic reactions of NbN result in the formation of"colloidal solutions",containing Nb_(2)O_(5)colloidal particles between the tribo-pairs.Utilizing the double electric layer repulsion and weak shear action of the"colloidal solution",NbN achieves ultra-low friction and wear;the corresponding values are as low as 0.058 and 1.79×10^(-10)mm^(3)·N^(-1)·m^(-1),respectively.In addition,other VB transition metal nitrides(VB TMNs)exhibit the same low friction feature as NbN in the three-phase contact environment;the friction coefficients are even lower than those in an oil-based environment.The water-based lubrication of VB TMNs provides a new reliable scheme for optimizing solid-water composite lubrication systems without additives and is expected to be applied in environments with high humidity or insufficient water coverage.

适用于页岩气水平井的低摩阻硅酸钾钻井液体系

当前环保形势日趋严峻,亟待广大钻井液从业者开发出一套可替代油基的水基钻井液体系,来解决页岩气水平钻进过程中存在的摩阻、井壁稳定以及井眼清洁等一系列难题。本次研究在硅酸钾钻井液强抑制、强封堵、易成膜的基础上,开发引入了一种具备协同封堵能力的强效水基润滑剂,并通过系列筛选和评价实验,构建了一套低摩阻硅酸钾钻井液体系。其润滑系数在0.08左右,抗磨砝码质量达到10 kg,具备媲美油基钻井液的润滑和抗磨性能;同时具有较低滤失量(FLHTHP小于6 mL);此外该体系还有较强的抑制和抗污染能力,流变易于控制,完全能满足页岩油气藏的开发需要。

Superlubricity achieved with two-dimensional nano-additives to liquid lubricants

The topic of superlubricity is attracting considerable interest around the world while humanity is facing an energy crisis.Since various liquid superlubricity systems can be commonly achieved on the macroscale in ambient conditions,it is considered an effective solution to reduce unnecessary energy and material losses.However,certain practical problems such as low load-bearing pressure,dependence on hydrogen ions,and relatively long running-in processes still limit its widespread application.Two-dimensional(2D)nano-additives with ultrathin longitudinal dimensions can lower the shear resistance between sliding solid surfaces,and thus further optimize the applied conditions.In this review,the latest studies on 2D nano-additives with a combination of various water-based lubricants in the state of superlubricity are reported,typically including black phosphorus(BP),graphene oxide(GO),and layered double hydroxide.During the sliding process,composite lubricants effectively improved the load capacity(up to 600 MPa),reduced wear,and accelerated the running-in period(within 1,000 s)of the liquid superlubricity system.Both macromechanical experiments and microscopic tests are conducted to precisely analyze various interactions at the interfaces of the nano-additives and solid surfaces.These interactions can be described as tribochemical reactions,physical protection,and adsorption enhancement,and improved wear resistance.This review provides better guidance for applying 2D nanomaterials in liquid superlubricity systems.

Preparation of an environmentally friendly emulsion-type lubricant based on crude rice bran wax

In this study,crude rice bran wax oil-in-water emulsion(named CRBWE)was prepared by agent-in-water method.The critical factors influencing the sample preparation process were optimized.For instance,the optimum hydrophile-lipophile balance value of compound emulsifier was 12.33–13.40,the content of compound emulsifier was 10 wt%,the emulsification temperature was 70°C–80°C,the agitation speed was 200 rpm,and the emulsification time was 30–45 min.The performances as a lubricant of drilling fluid were also evaluated with respect to lubricity,rheology and filtration loss of CRBWE.The results showed that CRBWE had good lubricity and didn't affect the rheological properties of drilling fluid.For example,when it was added into bentonite dispersion at room temperature with the fraction of 1 wt%,the coefficient of friction of bentonite dispersion dramatically decreased to 0.077,and the coefficient of friction reduced rate was greater than 80%.Overall,these findings indicated that CRBWE would have promising applications as environmental friendly lubricant of drilling fluids to reduce torque and drag in petroleum and natural gas drilling.

Analysis of surface and sub-surface of cold-rolled Al plate lubricated with water-or oil-based lubricants

For environmental protection, energy conservation, and other reasons, water-based lubricants are increasingly chosen to replace oil lubricants. Water-based lubricants are divided into emulsified and solution types. Solution type water-based lubricants have attracted significant attention for the good stability, easy biodegradability, and safety for workers. However, some problems exist with current solution type water-based lubricants, such as poor lubricity and corrosion resistance. During the cold-rolling process, A1 plate rolled using oil-based lubricant lubrication shows metallic luster, but that rolled using water-based lubricant shows corrosion spots, black strips, and no metallic luster. Therefore, this study mainly analyzed the reasons for the darkness of A1 plate cold-rolled with water solution lubricants. The differences in plate surfaces lubricated by water solution and oil were investigated by scanning electron microscopy, auger electron spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. The analysis results showed that the surface of the oil-lubricated sample is smooth, the oxygen content is low, and the oxide layer is thin, while the surface of the water solution-lubricated sample is rough, the oxygen content is high, the chemical composition is more complex, and the oxide layer is not uniform and thick.

A natural dye in water-based drilling fluids: Swelling inhibitive characteristic and side effects

The development of eco-friendly shale inhibitors is still an area which has attracted a lot of attention in the drilling industry.Henna extract is a natural dye which has recently shown considerable inhibition and weak deflocculation properties in clay-water system.This study aims to investigate swelling inhibitive feature and side effects of Henna extract in water-based drilling fluids(WBDFs).It was carried out through extensive experiments including adsorption measurements on shale by batch equilibrium,inhibition evaluation by dynamic linear swelling and cuttings dispersion,wettability alteration via contact angle measurements,compatibility by rheological properties determinations and fluid loss measurements,and lubricity.Both in natural pH and adjusted pH to 9,Linear adsorption model was more suitable for anticipating the adsorption behavior of Henna extract on the given shale sample.The results of the linear swelling and cuttings dispersion tests demonstrated that Henna extract in drilling fluid formulations diminished the swelling and dispersion characteristics of the addressed shale sample.Moreover,contact angle measurements showed that Henna extract expanded the hydrophobicity of shale formations,preventing and promoting water adsorption and shale stability respectively.This issue definitely introduces wettability alteration as a mechanism for shale stability by Henna extract.Compatibility determinations additionally uncovered that Henna extract is compatible with common WBDFs additives.As indicated by the lubricity tests,Henna extract enhanced the lubricity of WBDFs,a finding which can be of an incredible significance in directional drilling.Among others,advantages such as environmental friendliness,low cost,accessibility,and the counter corrosion property make the applicability of Henna extract in WBDFs profoundly suitable.

Comparative study on boundary lubrication of Ti_(3)C_(2)T_(x) MXene and graphene oxide in water

The emerging use of two-dimensional(2D)nanomaterials as boundary lubricants in water offers numerous benefits over oil-based lubricants;whereas the friction reduction varies significantly with nanomaterial type,size,loading,morphology,etc.Graphene oxide(GO)and Ti_(3)C_(2)T_(x)MXene,a relatively new 2D material,are investigated as boundary lubricants in water in this study.The contact pair mainly includes Si3N4 balls and Si wafer.The results found(1)monodispersed GO offers better lubricity than monodispersed MXene under identical concentration and testing conditions;and(2)the mixed dispersion of GO and MXene(0.1 mg/ml:0.1 mg/ml)produced the lowest friction coefficient of~0.021,a value 4×and 10×lower than that produced by comparable mono-dispersions of GO or MXene,respectively.Wear track analysis,focused ion beam microscopy,in-situ contact observation,and atomic force microscopy(AFM)characterization suggest(1)GO nanoflakes have higher adhesion than MXene and are more easily adsorbed on the tribopairs’surfaces,and(2)GO/MXene tribofilm has a layered nanostructure constituting GO,MXene,amorphous carbon,and TiO_(2).We further hypothesized that the high lubricity of GO/MXene results from the synergy of GO’s high adhesiveness,MXene’s load support ability,and the low shear strength of both constituents.The present study highlights the key role of tribofilm stability in water-based boundary lubrication using state-of-the-art 2D nanomaterials.

Modification on the tribological properties of ceramics lubricated by water using fullerenol as a lubricating additive

It is necessary to modify the running-in process for the application of ceramics using water as a lubricant in real conditions because ceramics sliding in water are characterized by a running-in period with severe friction and wear.Fullerenol,a kind of highly water-soluble nanoparticle,was synthesized and then used to ameliorate the tribological properties of Si 3 N 4 sliding against Al 2 O 3 in pure water.With the addition of fullerenol,the running-in period was shortened from 30 min to 100 s at a speed of 250 mm/s.The speed threshold above which ultralow friction can be obtained in a short time was expanded from 450 mm/s to 80 mm/s.Meanwhile,the load-carrying ability of water film was increased.The role of fullerenol was discussed based on observation of the wear scar by an optical interferometer and XPS characterization of the tribo-film on the wear track.

Lubricating properties of oil-in-water emulsion with low oil concentration:Competitive wetting effect

Oil-in-water （O/W） emulsions are widely used in metal working such as hot rolling and cutting. Three kinds of O/W emulsions with low oil concentration were prepared which include conventional emulsion （CE）, miniemulsion （MNE） and microemulsion （ME）. The lubricating properties of O/W emulsions with low oil concentration were investigated using the tribological testers and the thin film interferometry based on the relative optical interference intensity method. The tribological test results under boundary lubrication show that the friction coefficient and the total losing weight can be clearly seen： CE 〈 MNE 〈 ME. The lubricating film thicknesses under elastohydrodynarnic lubrication and thin film lubrication show that a relationship of the film formation abilities： CE 〉 MNE 〉 ME. Competitive wetting behavior of water and oil on solid surface was confirmed to play an important role in the film formation and tribological behaviors of O/W emulsion.

Applications of sum-frequency generation vibrational spectroscopy in friction interface

Sum-frequency generation(SFG)vibrational spectroscopy is a second-order nonlinear optical spectroscopy technique.Owing to its interfacial selectivity,SFG vibrational spectroscopy can provide interfacial molecular information,such as molecular orientations and order,which can be obtained directly,or molecular density,which can be acquired indirectly.Interfacial molecular behaviors are considered the basic factors for determining the tribological properties of surfaces.Therefore,owing to its ability to detect the molecular behavior in buried interfaces in situ and in real time,SFG vibrational spectroscopy has become one of the most appealing technologies for characterizing mechanisms at friction interfaces.This paper briefly introduces the development of SFG vibrational spectroscopy and the essential theoretical background,focusing on its application in friction and lubrication interfaces,including film-based,complex oil-based,and water-based lubricating systems.Real-time detection using SFG promotes the nondestructive investigation of molecular structures of friction interfaces in situ with submonolayer interface sensitivity,enabling the investigation of friction mechanisms.This review provides guidance on using SFG to conduct friction analysis,thereby widening the applicability of SFG vibrational spectroscopy.