Reducing the environmental impact of hydraulic fracturing pumps

Student thesis: Doctoral Thesis

Abstract

The current approach to hydraulic fracturing requires large amounts of industrial hard-ware to be transported, installed and operated in temporary locations. Typically 70% of the mass of this equipment is comprised of the fleet of truck-mounted pumps required to provide the high pressures and flows necessary for well stimulation. The established design of these pumps were developed for the shale gas extraction industry in North America, where the environmental, geological, regulatory and social constraints are very different from Europe. Consequently the engineering choices made in the current pump designs did not focus on minimising the physical and environmental footprint of the operation. These aspects are of paramount importance for the emerging hydraulic fracturing industry in Europe, so it is timely to address these factors when considering the design of future high-pressure pumps for European shale resources. This thesis develops and applies a methodology for environmental optimisation of the key mechanical design parameters for the high-pressure pumps that are central to hydraulic fracturing operations. Before describing the optimisation methodology the thesis provides an overview of the industrial plant required to carry out a hydraulic fracturing operation, and an estimate of the functional requirements (i.e. pressure and flow) of the equipment. The computational model, central to the optimisation process, is validated by using field data from a hydraulic fracturing site in North America and an experimental test rig. The optimisation analysis concludes that reducing the plunger diameter and running the pump at higher angular velocity, with lower forces, can increase pump efficiency by up to 4.6%. Furthermore the modification of the pump's parameters would result in several environmental benefits beyond the obvious economic gains of lower fuel con-sumption. Previous studies have shown that over 90% of the emissions of CO2 and other pollutants that occur during a hydraulic fracturing operation are associated with the pumps and their prime movers. Consequently, any increase in pumping efficiency will also reduce the greenhouse gas emissions and improve local air quality (CO2, NOx and other pollutants). Additionaly, the reduction in plunger diameter will reduce the amplitude of fatigue stresses and so increase the life of the units and allow their overall mass to be reduced. More reliable pumps could decrease the number of standby (i.e. backup) units necessary, and so reduce procurement costs and site traffic, including the overall site footprint. The concluding system optimisation study suggests that the highest level of direct on-site emission is due to the inefficient and asynchronous operation of multiple frac-truck assemblies. Reducing the number of frac-truck assemblies subsequently affects pump traffic lowering the nuisance effects to the local community such as noise, road damage and road traffic risk.
Date of Award30 Sep 2016
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsWeir Group plc (The) & University of Strathclyde
SupervisorJonathan Corney (Supervisor) & Xiu Yan (Supervisor)

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