Field Trials of Chokes, Frac Pump Valve Seats and Top Drive Washpipe with Smart Abrasion Resistant Nano-Composites: Increasing Mean Time Between Failures to Reduce Red Money
Authors: Roy Ting , Naceur Kamel Ben , Meissner Siggi , Koyanagi Yoshihiko , Ring Russell , Singh Anil , Wilkinson Christian , Ardic Hifzi , Roy Indranil 
Published: October 2023

Short mean time between failures (MTBF), [in this study this is defined as average useful life + time to redress or replace components which equates to red money] components such as choke beans deployed in high pressure gas wells, frac pump valve seats and their corresponding valves, pump liners, top drive washpipe sleeves with hard coatings such as Chemical Vapor Deposition (CVD), High-Velocity Oxygen Fuel (HVOF), Diamond-Like Carbon (DLC), deployed in abrasive environments, results in additional costs in tens of million dollars, for both operating and service companies.

Evidence of catastrophic choke failure in a few hours, when deployed between well head and sand traps, constrains operators to place them in manifolds after the traps. This can lead to the exposure of personnel to high pressures and temperatures when dumping sand, and the frequent replacement of chokes due to high velocity sand erosion. HVOF tungsten carbide (WC) coated frac pump valve seats and the corresponding valves have a life of approximately 80 hours. Ceramic lined mud pump liners and fluids ends with WC coatings have to be changed every 1600 hours or sooner owing to erosion due to abrasive particulates in drilling mud or often unclassified sand being carried by frac fluids.

Investigation into the depth and effects of residual stress of machine hammer peened drill collar alloys on corrosion, corrosion fatigue and erosion has elucidated the rationale of these failures. With ultra-thin hard coatings on a softer metal matrix, dynamic surface force due to impinging hard particulates (sand), larger in dimension compared to coating-thickness, enveloped in a fluid (slick water), creates hydrodynamic forces acting on the particulates resulting in fracture of hard coatings at a microscopic length scale. Breach of the thin coating and subsequent entry of corrosive fluids between the coating and softer metal substrate causes crevice corrosion leading to catastrophic failures.

To increase MTBF of the components discussed above, a multi prong approach is warranted with intelligent design changes to made to overcome these frequent failures. Design reviews with operators and end customers, including root cause failure analysis, have helped resolve part of underlying problems. With the advent of bulk nano-materials, abrasion resistant nano-composites with tailored properties: strength, modulus thus apposite hardness, abrasion aka erosion resistance, and fracture toughness surpassing properties of commercial cemented carbides has been proposed as a key alternate to help bridge this challenging "Technology Gap".

Here we present the design of nano-composites wherein the base-material may be a combination of ultra-hard, heavy nano-particulates having multi nano-phase inclusions with grain size varying between 100 nm to sub-micron grains (800 nm), coated polycrystalline diamond and cubic boron nitride (to prevent graphitization) during consolidation abetted by high pressures and temperatures. Salient ASTM G65 tests on bulk solids have shown superior performance up to ten-fold (10X) improvement over HVOF WC coatings and overlays. The first embodiment, a choke bean for high pressure gas well, is going into field trials at the end of July 2023. The focus of our paper is presenting a solution for choke beans while outlining technology gaps to be bridged in engineering valve seats, wash pipes and pump liners and other embodiments using abrasion resistant nano-composites (ARn-C). This re-design will significantly increase the operating life, and MTBF, hence reducing the frequency of repair and corresponding red money. Salient field test data will be included in our presentation.