Handling Uncertain Feedstock Compositions in Shale Gas Processing System Designs with Simulation-based Robust Equipment Capacities

Abstract

The international gas market has been revolutionized by the advent of shale gas. As the shale gas production rate from a shale well declines over time, the mixture composition of raw shale gas gathered from multiple shale wells can be uncertain. This paper addresses the robust design and synthesis of shale gas processing and natural gas liquids (NGLs) recovery processes under uncertain feedstock compositions. The process feedstock comes from 8 shale wells with different raw shale gas compositions and the processed pipeline gas is to satisfy the fuel demand of a real world power plant. We employ monoethanolamine absorption, triethylene glycol absorption, and turboexpander-based NGLs recovery in the process designs to remove acid gases, water, and NGLs, respectively. Based on detailed process simulation and techno-economic analysis for each raw shale gas composition, we develop a robust process design with the minimum total direct cost of each operation unit needed to satisfy the pipeline gas demand. The robust process design can handle feedstock from the 8 shale wells with varying production flowrates. We perform a life cycle analysis for the robust design according to the Eco-indicator 99 methodology. The unit annualized cost is $1.8/GJ. Raw shale gas production and cooling utility generation are the major contributors to the environmental impacts of shale gas processing and NGLs recovery.