A Flexible NGL Recovery Process for Shale Gas Production

Shale gas characteristics and operation are different than conventional gas. A shale gas plant is typically smaller in capacity ranging from as low as 15 MMSCFD to the typical 200 MMSCFD cryogenic train size. The main challenges are the unpredictable gas compositions and flow rates during the development stage, which makes liquid recovery difficult. These uncertainties are challenges for a traditional cryogenic plant which is designed for a specific range of feed gas flow and compositions. Shale gas compositions are richer in hydrocarbon liquids with ethane plus content ranging from 6 to 10+ GPM. Ethane is a valuable feedstock for petrochemical production, but ethane prices are unattractive in today’s environment. Most gas plants are operating in ethane rejection, resulting in a loss of propane revenue. To maintain propane recovery during ethane rejection, the refrigerated reflux category of NGL recovery technologies (e.g. Fluor’s Deep Dewpointing Process, DDP) has been developed to fully reject ethane while recovering 95% plus propane. The typical refrigerated reflux process is a refrigerated, non-expander process that can be turned down to as low as 4:1. The process can be operated in ethane recovery with minimal changes to the process to recover up to 60% ethane. The DDP process can also be enhanced to recover 95% ethane with additional compression. This technology has been proven in successfully operation in several installations. Presently, Fluor and Joule Processing are leveraging the versatility of the refrigerated reflux process by productizing the proven and patented DDPSM version of this technology in the form of an "equipment kit". These equipment kits will offer a relatively small modular footprint to reduce installed cost and accelerated factory lead-time to shorten the overall EPC schedule. This paper discusses the design, costs and economics of the DDP process for a typical shale gas plant, and the methodology to switch from propane recovery to 60% ethane recovery during normal operation, and to high ethane recovery with the bolt-on design. Key design challenges from an operating DDP unit are also detailed.