Performance evaluation of shale gas processing and NGL recovery plant under uncertainty of the feed composition

Abstract

The dramatic increase in discovering reserves of unconventional oil and gas wells has led to significant production of shale gas. It is predicted that by 2035, shale gas will be nearly half of the U.S. production of natural gas. One of the key challenges in processing shale gas is its varied flow rate and uncertain composition. The continual decrease in shale gas flowrate from a well can be managed by integrating supply of other wells and optimizing plant capacity. On the other hand, the composition of shale gas that differs from one well to another depending on the age and geological formation of the well is a natural phenomenon and hard to mitigate. Furthermore, prediction of the anticipated composition before production is uncertain. The uncertain variation in composition provides a challenge in the efficient design of a shale gas processing and natural gas liquids (NGLs) recovery plants. In this work, a stochastic approach is used for shale gas characterization and its impact on the performance of shale gas processing and NGL recovery units is addressed. The corresponding performance outcomes provide the distribution profile that is probabilistically characterized and design and performance targets that meets sustainability criteria (e.g. economic as well as environmental) are identified. A case study with three design capacities is solved to illustrate the value of the proposed approach. The analysis shows that the plant performance meets the minimum profitability criteria (ROI, %/year) only under specific feed composition and for a given plat capacity. The economic benefit as obtained from stochastic analysis is found to differ from that using the median value of the uncertain variables by ≅ 9.79%, suggesting limitations of traditional design approaches that do not account for uncertainty. The environmental performance is found to be insensitive to uncertainty.