The role of materials engineering to mitigate corrosive wear in oil field pumping applications

This thesis was previously held under moratorium from 25/04/2018 to 01/05/2023Hydraulic fracturing is a technique used to stimulate the flow of oil/gas from tight formations of subterranean rock. The pumping equipment used operates under harsh environments; hence, has a short life expectancy. This research focuses on an investigation of corrosive wear issues associated with hydraulic fracturing pump components with a view of finding cost-effective solutions to combat these problems. A recirculating slurry impingement rig was used to test the materials under corrosive wear conditions. To comprehend the various wear mechanisms occurring during testing a recently-developed, in-house volumetric analysis technique was employed, which combined electrochemical monitoring tests and 3D surface profiling. A novel repetitive impact slurry rig was developed to mimic the repetitive impact metal-metal wear occurring on valves and seats used in the hydraulic fracturing pump. The enhanced volumetric analysis technique and information from segmented specimens provided a means of unravelling the complex deterioration processes that occur in the different regions of a submerged jet specimen. Post-test examinations of specimens using light-optical and scanning electron microscopy was also undertaken to yield information on mechanisms of degradation. As hydraulic fracturing equipment is likely to have to operate in a range of water salinities, the effect of salinity on the currently used fluid end (i.e. pump casing) material (UNS G43400) as well as alternative material options was investigated. Increasing salinity from 0.05%NaCl to 10%NaCl was found to have a marginal increase in material loss for the stainless steel alloys, whereas, there was a significant increase for the low alloy steel. Sacrificial anode cathodic protection was also observed to be beneficial in reducing the material loss for the low alloy steel in the corrosive wear conditions. The effect of nitriding Stellite 6 weld claddings was assessed as a hardfacing and/or repair option for hydraulic fracturing pump components. The nitriding process was found to be detrimental to the corrosion resistance of the Stellite 6 weld claddings; however, the volumetric analysis technique demonstrated that the nitriding process was capable of improving their mechanical erosion resistance. Additively manufactured alloys were also assessed as alternative materials and/or a repair technique for hydraulic fracturing pump components. The additive manufactured alloys were compared to equivalent alloys which were conventionally manufactured. The additively manufactured alloys were observed to have significantly better corrosion resistance than the wrought alloys in static and flowing conditions. Under solid-liquid erosion-corrosion testing, the additive manufactured alloys and equivalent wrought alloys performed similarly. A wide range of materials (soft/ductile to hard/brittle) were assessed under repetitive impact with slurry conditions. The results from the novel testing apparatus indicated that there was an optimum material hardness for repetitive impact wear resistance. Hence, suggesting that hardness is required to resist plastic deformation and toughness is required to resist brittle failures.Hydraulic fracturing is a technique used to stimulate the flow of oil/gas from tight formations of subterranean rock. The pumping equipment used operates under harsh environments; hence, has a short life expectancy. This research focuses on an investigation of corrosive wear issues associated with hydraulic fracturing pump components with a view of finding cost-effective solutions to combat these problems. A recirculating slurry impingement rig was used to test the materials under corrosive wear conditions. To comprehend the various wear mechanisms occurring during testing a recently-developed, in-house volumetric analysis technique was employed, which combined electrochemical monitoring tests and 3D surface profiling. A novel repetitive impact slurry rig was developed to mimic the repetitive impact metal-metal wear occurring on valves and seats used in the hydraulic fracturing pump. The enhanced volumetric analysis technique and information from segmented specimens provided a means of unravelling the complex deterioration processes that occur in the different regions of a submerged jet specimen. Post-test examinations of specimens using light-optical and scanning electron microscopy was also undertaken to yield information on mechanisms of degradation. As hydraulic fracturing equipment is likely to have to operate in a range of water salinities, the effect of salinity on the currently used fluid end (i.e. pump casing) material (UNS G43400) as well as alternative material options was investigated. Increasing salinity from 0.05%NaCl to 10%NaCl was found to have a marginal increase in material loss for the stainless steel alloys, whereas, there was a significant increase for the low alloy steel. Sacrificial anode cathodic protection was also observed to be beneficial in reducing the material loss for the low alloy steel in the corrosive wear conditions. The effect of nitriding Stellite 6 weld claddings was assessed as a hardfacing and/or repair option for hydraulic fracturing pump components. The nitriding process was found to be detrimental to the corrosion resistance of the Stellite 6 weld claddings; however, the volumetric analysis technique demonstrated that the nitriding process was capable of improving their mechanical erosion resistance. Additively manufactured alloys were also assessed as alternative materials and/or a repair technique for hydraulic fracturing pump components. The additive manufactured alloys were compared to equivalent alloys which were conventionally manufactured. The additively manufactured alloys were observed to have significantly better corrosion resistance than the wrought alloys in static and flowing conditions. Under solid-liquid erosion-corrosion testing, the additive manufactured alloys and equivalent wrought alloys performed similarly. A wide range of materials (soft/ductile to hard/brittle) were assessed under repetitive impact with slurry conditions. The results from the novel testing apparatus indicated that there was an optimum material hardness for repetitive impact wear resistance. Hence, suggesting that hardness is required to resist plastic deformation and toughness is required to resist brittle failures