Fluid Lubrication Research Articles

Deep eutectic solvent modified graphene as a lubricant for water-based drilling fluid

ABSTRACT Deep and ultra-deep drilling technology development is critical to the exploitation of ultra-deep oil and gas deposits. As the number of ultra-deep wells increases, the bottom hole temperature of certain ultra-deep wells approaches 250°C. The high-temperature and high-pressure environment can influence the stability and longevity of drilling instruments, as well as the density, rheology, and stability of drilling fluid, making wellbore stability difficult to maintain. Problems such as high torque and high friction affect the safety of downhole drilling and drilling efficiency. Adding lubricant to drilling fluid is an effective way. In this study, choline chloride (ChCl) and polyethylene glycol (PEG) were used to synthesize a deep eutectic solvent (DES), and an environmentally friendly water-based drilling fluid lubricant DES/G was prepared by compounding the DES with graphene (G). Infrared spectrum, particle size analysis, and electron microscope tests were used to characterize the structure of the lubricant. At the same time, the effect of lubricant was evaluated by extreme pressure lubricity tester and friction and wear tester, and the adhesion coefficient of filter cake was tested. At temperatures below 200°C, DES/G demonstrated a significant enhancement in the lubricating properties of drilling fluids and filter cakes. The adhesion coefficient was controlled within 0.1, and the reduction rate was exceeding 30%. With increasing dosage of the lubricant, DES/G consistently maintained a low adhesion coefficient value of 0.03803 to 0.06253 (at 180°C) and 0.0414 to 0.07337 (at 200°C). Furthermore, it exhibited higher values of reduction rate, reaching a maximum of 64%. The lubricant can increase lubricating performance by adsorbing on the metal surface to generate a strong lubricating coating and converting the sliding friction between drilling tools to rolling friction.

The Friction Performance Analysis of Textured Gear under Starved MHD Lubrication

In this paper, the lubrication model of involute spur gear lubricated by MHD is established by considering different oil supply conditions and adding non Newtonian, thermal and surface texture. Using the multigrid method, the elastohydrodynamic numerical solutions of the meshing points, nodes, and exit points under different operating conditions during the meshing process are obtained. The results show that when the gear runs out of oil, using magnetic fluid lubrication can improve the lubrication condition. Compared to non textured gear meshing, the oil film thickness of textured gears participating in meshing is larger, which is beneficial for lubrication. The texture has the greatest impact on the node. By analyzing the influence of texture parameters at nodes, it can be seen that there is an optimal value for texture width, while a smaller depth is advantageous. It can be seen that the gear texture improves the pressure and film thickness distribution in the meshing area, which is beneficial for lubrication conditions and provides a reference for optimizing the tribological design of gears.

Modified locally derived graphene nanoplatelets for enhanced rheological, filtration and lubricity characteristics of water-based drilling fluids

Drilling fluid rheology, filtration, and lubricity are fundamental parameters that influence the efficiency and ease of drilling operations. The drilling industry is constantly exploring different research areas for stabilizing and improving these parameters at high temperatures. The use of drilling fluid additives, especially synthetic polymers, poses a threat to the environment. Herein, rice husk char (RHC) was used to synthesize graphene Nanoplatelets (GNP) whose surface is modified with triton-X100 nonionic surfactant. Field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR), Particle size distribution (PSD), Energy Dispersive X-Ray Analysis (EDX), and Zeta potential analysis are performed on the synthesized nanomaterials to verify their morphology, functional groups, particle size, elemental composition, and material stability. Synthesized GNP from RHC (GNP-RHC) along with surface-modified GNP-RHC (GNP-TXT) were examined critically and their properties compared using a water-based mud (WBM) formulation. The rheological and lubricity characteristics of all the mud samples were determined before and after hot rolling (AHR), and the filtration properties were determined under API and high pressure high temperature (HPHT) conditions. The TGA results indicate that GNP-TXT nanomaterial resists thermal degradation with 10% weight loss at 300 °C, while the zeta potential analysis indicates the materials are stable. Since the GNP-TXT particles are so well dispersed, the GNP-TXT-based muds worked better than the GNP-RHC-based muds and was more stable at controlling filtration and improving rheological properties. For example, at 1.5 g AHR, the plastic viscosity of GNP-TXT-based mud decreased by 22.2% from 9 to 7 cP, while that of GNP-RHC-based mud decreased from 17 to 7 cP by 59%. Also, the API and HPHT FL of WBM of 11 and 24.8 mL, respectively, were reduced by GNP-TXT-based muds to the range of 8.6 and 9.8 mL for API and 18.6 and 22.3 mL for HPHT. However, GNP-RHC-based drilling muds showed a lower fluid loss control of the WBM between 9.6 and 10.2 mL for API and between 19.6 and 23.6 mL for HPHT. Furthermore, the coefficient of friction of the WBM of 0.45 was decreased with GNP-RHC concentrations between 0.47 and 0.32, while GNP-TXT demonstrated a higher decrease between 0.26 and 0.20.

The tribocorrosion behavior of Monel 400 alloy in seawater at different temperatures

Temperature is one of the important factors affecting metal corrosion in marine environment. The effect of temperature on tribocorrosion behavior of Monel 400 alloy is studied in this paper. The results show that compared with the mechanical wear condition, the corrosion product layer with anti-wear effect is formed on the surface of the alloy during tribocorrosion condition, which reduces the wear rate by nearly one third. As the temperature increases, the covering area of corrosion product layer increases. However, the wear rate and friction coefficient of the alloy at higher temperature are not reduced. It is attributed to the decrease of seawater viscosity at higher temperature, resulting in poor fluid lubrication performance of seawater.

Frequency-Dependent Dewetting of Thin Liquid Films Using External ac Electric Field.

The stability of thin liquid films on a surface can be controlled by using external stimuli, such as an electric field, temperature, or light, by manipulating the total excess free energy of the system. It has been previously shown that thin lubricating films on slippery surfaces can be destabilized via the spinodal mechanism using an external electric field, which returns to the original stable configuration upon the electric field. However, the role of the frequency of the applied ac electric field is not clear, which is the main topic of study in this report. When an ac electric field of fixed voltage and varying frequency is applied across thin lubricating films of slippery surfaces, a different dewetting behavior is observed. Characteristic length and time scales of dewetting depend strongly on the frequency of the applied voltage, which is primarily due to the change in the dielectric behavior of the lubricating fluid. In addition, the interplay of various time scales involved in the dewetting process also depends on the frequency.

An arbitrary Lagrangian–Eulerian formulation for the Reynolds equation considering the JFO boundary condition

AbstractIn the realm of lubrication theory, the hydrodynamics of the fluid lubricant are commonly elucidated through the Reynolds equation. Its establishment stems from using the Eulerian description method, restricting the fluid domain to a fixed spatial configuration. However, certain scenarios necessitate coupling the Reynolds equation with solid deformation, wherein the fluid boundary undergoes alterations concurrent with the displacement or deformation of the solid. In such cases, the employment of a movable fluid domain becomes imperative. To address this requirement, this contribution introduces the arbitrary Lagrangian–Eulerian method, which effectively transforms the reference system of the Reynolds equation into a fluid domain amenable to arbitrary movement. Subsequently, the weak formulation associated with the movable fluid domain is derived and synergistically combined with a preexisting cavitation formulation. This integration facilitates an efficient solution of the Reynolds equation utilizing the finite element method while duly accounting for the mass‐conserving cavitation effects. Ultimately, a transient hydrodynamic lubrication example is presented to demonstrate the feasibility of the newly developed formulations.

Mathematical Model to Study the Squeeze Film Characteristics of Diseased Human Synovial Knee Joint

Synovial fluid functions as a biological lubricant and lubricates articular cartilage to reduce friction and wear. Lubricin and hyaluronic acid are the primary components of synovial fluid responsible for its lubricating properties. The loss of properties in synovial fluid and articular cartilage due to aging and activities can restrict mobility in synovial joints, resulting in the degradation of articular cartilage and ultimately leading to pathological synovial joints, which is a major cause of disability. Thus, research on synovial joints remains crucial, and despite previous investigations on synovial joint lubrication, there are several issues related to squeeze film lubrication that require further attention. The Newtonian model of squeeze film lubrication in synovial joints needs to be extensively studied. In this study, lubrication and other related properties of synovial fluid are studied theoretically. In this paper, we have studied the flow of synovial fluid in the diseased synovial joint. Further, we have studied the effect of the viscosity of the synovial fluid, the permeability of articular cartilage, thickness of articular cartilage, and fluid film thickness on the characteristic of the squeeze film formed between the articular cartilages of the diseased human knee joint. The flow of synovial fluid is modeled by considering it as a viscous, incompressible and Newtonian fluid. We have derived the modified Reynolds equation using the principle of hydrodynamic lubrication and continuum mechanics theory and solved it by applying the suitable boundary conditions according to the physical considerations. Subsequently, we obtained the expression for pressure distribution in fluid film, load-bearing capacity, and squeeze time and have done the theoretical analysis on these properties for different parameters. Pressure increases with squeeze velocity and viscosity of the synovial fluid and decreases with permeability and fluid film thickness. Human knee joint becomes diseased due to excessive pressure, and the mobility of the knee joint decreases. The load capacity increases with viscosity and squeeze velocity and decreases with permeability resulting in the reduction of the load-carrying capacity of the knee joint in diseased conditions. Moreover, the squeeze time also increased in the diseased state of the joint.

Study on the friction reduction characteristics of surface micro-pit weave under fluid lubrication conditions

As for the improvement and improvement of tribology, numerous literature studies have shown that certain surface roughness is conducive to enhancing the dynamic pressure lubrication effect and reducing the frictional wear between frictional pairs. The design of a micro-loom with a reasonable characteristic size significantly brings out its friction reduction performance. The CFD software ANSYS Fluent was used to numerically analyze the hydrodynamic pressure on the surface of the micro-loom to obtain the oil film load-bearing force generated by the relative sliding on the surface of the friction pair and to analyze the effect of the depth of the micro-crater on the tribological performance. The results show that the coefficient of friction rises first and then decreases with the increase of the depth of the micro-pit within the given weaving parameters, the maximum bearing capacity is 0.088 N when the depth of the micro-pit is 4 μm, and only 0.086 N when the depth is 10 μm.

Optimized selection of fluid lubricant for cylindrical roller bearings under elastohydrodynamic lubrication

Roller bearings are widely used in machinery. Keeping the contact surfaces of bearings properly lubricated strongly mitigates wear effects, improving bearing fatigue life. Therefore, systematically selecting the lubricant fluid that satisfies bearing operation conditions allows the lubricating layer to be able to carry the applied load, the operating temperature, and the roughness on contact. The nonlinear constrained optimization method is used for lubricant selection, seeking to find the fluid that best fits the bearing operation conditions. Roller bearing lubrication is characteristically elastohydrodynamic (EHL); namely, the Hertz theory describes the load applied on the contacts of a cylindrical roller bearing, and the Stribeck condition classifies the tribological condition of the surfaces in contact. This work concludes that roughness and speed are the most important parameters to consider when choosing a fluid lubricant.

Vibration characteristics of turbocharger rotor system considering internal thread texture parameters of semi-floating ring bearing

The internal thread texture causes changes in the dynamic characteristics of the oil film of the semi-floating ring bearing, which affects the amplitude of vibration and operating life of the turbocharger rotor system. Based on the fluid lubrication theory, the oil film governing equation of a semi-floating ring bearing with surface texture parameters is derived. The effects of the texture depth, position, and number of turns of the internal thread on the dynamic characteristics of the bearing oil film, such as the maximum pressure, load-carrying capacity and stiffness damping, are analyzed. Taking a type of turbocharger as an example, a hydrodynamic model is established to analyze the oil film lubrication in the semi-floating ring bearings, and the dynamic characteristic of the oil film is analyzed by computational fluid dynamics method. The results show that the maximum pressure, bearing capacity, and stiffness damping coefficient of oil film increase firstly and then decrease with the increase of texture depth and the number of thread turns in the range of journal rotation speed from 1000 to 20,0000 r/min. Compared with the non-texture bearings, the dynamic characteristics coefficients of the oil film such as bearing capacity and stiffness damping increase the most, when the depth of texture is 0.006 mm and the number of thread turns is 9. Secondly, the dynamic characteristic coefficient of oil film is improved when the texture is distributed in the middle than on both sides. The thread texture with appropriate parameters can suppress the rotor system vibration amplitude. The conclusion can provide a reference for the design of textual parameters of semi-floating ring bearings.

AI‐Enabled Metal‐Polymer Plain Bearing Based on the Triboelectric Principle

AbstractWith the rapid development of the Internet of Things and artificial intelligence (AI), the requirement for sensing technologies for smart bearings has increased dramatically. The general bearing sensors can only recognize the basic information from temperature or vibration, far from satisfying the self‐diagnosis and self‐maintenance. Recently, self‐powered sensing technologies based on triboelectric nanogenerators have paved a new route for fabricating smart bearings. In this study, the triboelectric principle is applied to a commercial metal‐polymer plain bearing (MPPB) bearing, which can achieve self‐sensing, self‐diagnosis, and self‐maintenance. The geometrical structure of the triboelectric MPPB (T‐MPPB) is designed to balance the output efficiency and external load, and the super durability and load capability are verified. Besides, the mechanism behind the output change trend under boundary and hydrostatic fluid lubrication is revealed for the first time. Furthermore, the deep learning algorithm can classify the lubrication states with highly accurate performance. The proposed T‐MPPB has the potential to achieve self‐maintenance with the lubricating pump according to the lubrication condition classified by the AI. This research not only establishes the feasibility of designing self‐powered smart MPPB but also demonstrates a way for identifying lubrication states, thus achieving self‐diagnosis and self‐maintenance ability by self‐powered sensors.

Molecular dynamics simulation of the Stribeck curve: Boundary lubrication, mixed lubrication, and hydrodynamic lubrication on the atomistic level

Lubricated contact processes are studied using classical molecular dynamics simulations for determining the entire range of the Stribeck curve. Therefore, the lateral movement of two solid bodies at different gap height are studied. In each simulation, a rigid asperity is moved at constant height above a flat iron surface in a lubricating fluid. Both methane and decane are considered as lubricants. The three main lubrication regimes of the Stribeck curve and their transition regions are covered by the study: Boundary lubrication (significant elastic and plastic deformation of the substrate), mixed lubrication (adsorbed fluid layer dominates the process), and hydrodynamic lubrication (shear flow is set up between the surface and the asperity). We find the formation of a tribofilm in which lubricant molecules are immersed into the metal surface—not only in the case of scratching, but also for boundary lubrication and mixed lubrication. The formation of a tribofilm is found to have important consequences for the contact process. Moreover, the two fluids are found to show distinctly different behavior in the three lubrication regimes: For hydrodynamic lubrication (large gap height), decane yields a better tribological performance; for boundary lubrication (small gap height), decane shows a larger friction coefficient than methane, which is due to the different mechanisms observed for the formation of the tribofilm; the mixed lubrication regime can be considered as a transition regime between the two other regimes. Moreover, it is found that the nature of the tribofilm depends on the lubricant: While methane particles substitute substrate atoms sustaining mostly the crystalline structure, the decane molecules distort the substrate surface and an amorphous tribofilm is formed.

The Null technique as a novel, potential first-line method of device delivery for complicated lesions during percutaneous coronary intervention

AimDuring percutaneous coronary intervention (PCI), complicated lesions in the target coronary artery often hinder device delivery. Fluid lubricants have commonly been used to reduce friction between adjacent solid materials in manufacturing, thus achieving smoother action. This ex vivo experimental study examined whether a contrast medium could function as a fluid lubricant during PCI. Methods and resultsWe used two different coronary artery lesion models with distinct complexities made from silicon. Each model was fit into the ex vivo PCI-simulation system. This ex vivo laboratory equipment consisted of ordinary PCI instruments and an aorta model from the Valsalva sinus to the descending aorta. A Wolverine™ cutting balloon catheter was advanced through each lesion model via a guide catheter set into the system. The maximum force required to push the catheter through the lesion models was measured while the vessel system was filled with either normal saline or contrast medium. The maximum force required was significantly lower with the contrast medium (1.38 ± 0.21 N in the normal-saline condition vs. 0.92 ± 0.05 N in the contrast-medium condition in the lesion model A, p < 0.001; 1.30 ± 0.07 N in the normal-saline condition vs. 1.14 ± 0.04 N in the contrast-medium condition in the lesion model B, p < 0.001). ConclusionsThe contrast medium for vessel system filling reduced the force required to push the devices through the lesion models. This contrast medium represents a potential candidate for a liquid lubricant to facilitate device delivery for complicated coronary lesions.

Tribological aspects of nano-particle fluid based cooling and lubrication in milling process

The introduction of different additives into the cooling and lubrication systems in the metal cutting process, contributed to improving the machining process sustainability. Different types of additives can help to reduce friction, reduce wear of contact surfaces, improve heat dissipation from the cutting zone, etc. With the development of nanotechnology, great focus has been placed on the investigation and using of nano-particles, nano-additives and nanofluids in industry. In this paper, the effects of using the nano-particle based cooling and lubrication fluid are investigated. There are performed comparison effects of standard cooling and lubrication fluids versus nanofluids based cooling and lubrication on cutting process performance. Molybdenum disulphide particles are used as nano-particles, which dispersed in a standard cooling and lubrication fluid. As workpiece was used alloyed tool steel. Milling process performance indicators was analysed based on Taguchi experimental plan, for different cooling and lubrication condition and process parameters. Cutting forces component in three perpendicular axes, and machined surface parameters were measured. Experimental analysis has shown that the use of nano-particles, which mixed in a standard cooling and lubrication fluid, significantly contributes to the reduction of cutting forces, friction coefficients, more efficient cutting and generation of machined surfaces.

A review on tribology, characterization and lubricants for water-based drilling fluids

The challenges associated with drilling large displacement horizontal wells are numerous, and their adverse effects can lead to severe damage or even shut down of the drilling operation. Frictional torque of the tubular column is one of the most common problems encountered when applying water-based drilling fluids to the drilling of extended reach wells. This is because during the drilling process, there is continuous friction between the drilling tool and the rock. When water-based drilling fluid cannot effectively reduce friction, it will cause difficulty in lifting or lowering the drilling tool, resulting in sticking, and thus affecting the drilling operation. Most petroleum engineers use different lubricants to reduce friction and wear during drilling.The purpose of this study is to present the friction and lubrication state during drilling, the mechanism of action of boundary lubrication, lubrication evaluation and analysis methods, and friction reduction and wear resistance related to water-based drilling fluid lubricants reported in literature for reducing friction.Based on the review, we recommend a broad evaluation of lubricants using different lubricity performance evaluation methods to determine the true lubricity performance in the coexistence of multiple frictions during drilling. In addition, we recommend that future researchers enhance the application of numerical simulations in the analysis of lubricant lubrication mechanisms to address the difficulty of direct experiments in boundary lubrication laboratories. Any experimental program requires at least five characterization techniques, including friction coefficient, wear resistance testing, scanning electron microscopy, energy dispersive X-ray spectroscopy, and electron spectroscopy, to provide a detailed understanding of the friction reduction mechanism of the lubricant used. Lubricants based on bionic technology with good water solubility, low biotoxicity, and easy biodegradability are highly encouraged because of their availability and good lubricating properties.

A sustained release lubrication method of agarose-sodium hyaluronate hydrogels for artificial joint.

The artificial joint prosthesis's surface is subjected to wear due to the destruction of the joint lubrication environment after surgery. In this study, an agarose-sodium hyaluronate hydrogel was used as lubricant additive in order to supply and preserve the lubricating fluid of artificial joint prostheses. A ball on disc experiment was conducted using this hydrogel to evaluate the lubrication efficiency and release rate under various frequencies. The results showed that this hydrogel could release lubricant under pressure and then absorb the released fluid after decompression. Furthermore, the agarose-sodium hyaluronate hydrogel acted as an effective transport mechanism to release sodium hyaluronate lubricant into the metal-on-polymer friction interface. Compared with pure water lubrication, the friction coefficient and wear volume were reduced by up to 62.9%, and 86.9% respectively. Moreover, the proposed lubrication method provided a long-term lubrication on artificial hip joints.

A Method for Mathematical Modeling of Hydrodynamic Friction of Plunger Pairs with Consideration of Microgeometry

The fuel injection system heavily relies on the high-pressure fuel pump, which plays a critical role in its overall performance. The fuel pump plunger is subjected to high levels of stress and experiences irregular lubrication during dynamic loads, causing premature wear. In the industrial sector, laser surface micro-texturing has been utilized to reduce friction and enhance anti-wear properties, and its positive impact has been supported by both theoretical and experimental evidence. This article presents a method for determining the hydromechanical characteristics of plunger pairs under conditions of hydrodynamic friction. The microgeometry of friction surfaces was taken into account through the cavitation effect of the lubricating fluid, described by the modified Reynolds equation. Software was developed according to the proposed method. The developed software can be used to analyze the contacting surfaces of plunger pairs and evaluate their tribotechnical characteristics based on the microgeometry parameters of the friction surfaces. The article also discusses the impact of the microgeometry parameters on the quality criteria of the hydromechanical characteristics of the plunger pairs. Computational examples are given for the analysis of contacting surfaces of plunger pairs separated by a lubrication layer. The technical characteristics are evaluated depending on the parameters of the microgeometry of the roughness of the friction surfaces. The influence of the microgeometry parameters on the quality criteria of the hydromechanical characteristics of the plunger pairs is presented.

Development of a novel reciprocating cryogenic tribometer through deformations of measurement structure.

In this study, a novel reciprocating tribometer, in which the frictional pairs were immersed in liquid nitrogen directly, was developed to simulate the cryogenic fluid lubrication. To eliminate the negative influence of extremely low temperature on force sensors, a transfer structure of force-deformation, consisting of cantilever beams and measurement beams, was designed specially. It can transfer the structural deformations caused by the loading force and the friction force from the cryogenic zone to the room-temperature zone. The corresponding measurement principle was discussed in detail, and the linear relationship between the structural deformation and the applied force was verified theoretically. Through static calibration experiments, the fitting relationship between the deformations and the loading/friction force was acquired for the developed tribometer. In final, a preliminary investigation of graphite materials was conducted on the tribometer to compare the room-temperature and cryogenic tribological behaviors.

Studying the Tribological Properties of Coffee Oil-Loaded Water-Based Green Lubricant

Lubrication is the primary solution to reduce friction and wear. However, conventional lubricants cause pollution when not properly disposed of or due to accidental leaks. Therefore, environmentally friendly lubricating fluids are welcome in any application where they can meet the performance requirements. This study suggests using coffee oil produced from spent coffee grounds to improve the lubricity of water-based lubricating fluid. Bis(2-hydroxyethyl)ammonium oleate protic ionic liquid facilitates the dispersion of coffee oil in water. Kinematic viscosity, wettability, corrosion prevention, and lubricity tests were performed to evaluate the tribological properties provided by these additives. It was observed that a higher amount of coffee oil could be dispersed with the introduction of a higher amount of protic ionic liquid. In this study, ten wt.% of coffee oil was successfully dispersed using one wt.% of protic ionic liquid. Introducing additives increased dispersions’ viscosity, improved wettability, provided protection against corrosion, and reduced wear and friction. It was proposed that polar molecules of protic ionic liquid were responsible for most of the improvement, while coffee oil contributed by increasing viscosity. Further studies could be directed toward determining rational concentration to meet each particular application’s requirements.

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 °C 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.