Applications of Diamond to Improve Tribological Performance in the Oil and Gas Industry

Abstract

The use of diamond in tribological applications in the oil and gas industry is reviewed. The high hardness, strength, and corrosion resistance of diamond make it an attractive option for components that are susceptible to degradation by abrasive, erosive, or adhesive wear; such components may also be prone to corrosion owing to the nature of the environments to which they are often exposed. Applications such as drill bits, bearings, and mechanical seals benefit from the use of diamond, while choke valves are the subject of research programs to assess the suitability of chemical vapor deposition (CVD) diamond for these components. Also discussed are some of the conditions experienced by the components and how the properties of diamond enhance their operating lives.

Interfacial Bonding Controls Friction in Diamond–Rock Contacts

“…The root-mean-square surface roughness of the pins was measured using white light interferometry ( R a = 2.86 μm, R q = 3.65 μm). , The tests were conducted in both aqueous and air environments (average relative humidity = 70%). The experimental sliding velocity was 0.1 m s –1 , which is somewhat lower than that used in operational PDC drills (2–4 m s –1 ) . The load was progressively increased (1–200 N) and held for 5 min at the same sliding velocity while the friction data were measured.…”

“…The Archard equation is the most popular empirical model to predict abrasive wear inside macroscale contacts where V is the wear volume, K b is the wear coefficient, F n is the load, d is the sliding distance, and H is the hardness. The Archard equation has frequently been used to model the abrasive wear of PDC bits. − The hardness of the polycrystalline diamond (PCD) used in PDC bits is at least 55 GPa . During the drilling process, the bits can often pass through greatly varying geologies.…”

“…Even within a single rock type, the properties can vary markedly and can be heterogeneous and scale-dependent. The mean hardness values have been measured for several rock types, for example, calcite-rich rocks (e.g., limestone) have a mean hardness of ∼2 GPa, while quartz-rich rocks (e.g., granite) have a mean hardness of 9–15 GPa. , Since these are both much softer than PCD under ambient or typical wellbore temperatures (<300 °C), low abrasive wear rates are expected from the Archard model for PDCs when drilling both granite and particularly, limestone rocks. However, the effective hardness of PCD can be reduced below that of quartz (but not calcite) when local cutting temperatures exceed ∼750 °C .…”

“…17 The ROP is reduced by high friction coefficients at the bit−rock interface, which are 3−5 times higher for PDCs compared to other (roller cone, tungsten carbide insert) drill bits. 18 High friction coefficients, coupled with high sliding velocities (>1 m s −1 ), 19 result in large temperature increase (hundreds of degrees) at the bit−rock interface, 19 which can promote deleterious structural transformations (graphitization) within the surfaces of PDC bits. 20,21 These transformations, coupled with increased abrasive wear due to the higher hardness of the counter surface, 22 are the principal causes of reduced bit life in hard rock formations.…”

Improving Pressure–Velocity Limit of Mechanical Seal with Polycrystalline Diamond Coating

“…However, there are few researches on the upper limit of mechanical seals with PCD coating application under conditions where the combination of high pressure and high surface speeds create high levels of pressure-velocity (PV). The PV limit, where P is the pressure drop across the seal and V is the mean sliding velocity [15], is a well-known parameter in designing mechanical seals, defining the operating envelope, and used as the most common approach to seal evaluation. Meanwhile, the comparison between the PV limits of diamond coating and uncoating mechanical seals has not been given much attention.…”