FORT WORTH, Texas—It’s a riddle posed for any new industrial plant: Do you go with an off-the-shelf design that’s cheaper to build but potentially less efficient—or do you custom design a facility, making it more costly to construct, but that will be more efficient?

Which approach will be more profitable?

That question certainly applies for natural gas processing plants, a pair of processing plant engineers told attendees at the pre-conference midstream program of Hart Energy’s DUG Permian conference.

“The question is, which battles do you choose to fight when you choose one or the other?” asked Chuck Laughter, vice president of engineering and operations for Joule Processing. And someone needs to define what a standard design is, he asked.

“So what is a standard facility? It’s the same as last time, except.…” he added with a chuckle, his voice trailing off.

It’s important to remember that about one-third of any gas plant is standardized, Laughter said. The additional two-thirds of each design, however much it may or may not be customized, depends on a customer’s needs and wishes. Standardized designs can be applied to a plant’s major equipment kits, including incoming gas stabilization and treating. A plant may also have fairly standard processing and compression needs. Utility needs may be fairly standard too.

Customization typically applies to site preparation and civil engineering that addresses such issues as drainage and soil composition and details for construction staging. The most tweaking, however, will involve inlet volumes and pressures, the composition of the inlet gas stream and potential fluctuations in inlet composition over time as the producing field matures. Also, the customer’s desire or need to fine-tune recovery of each of the gas liquids can make big differences, Laughter said.

Standardization provides the advantages of well-defined and proven equipment virtues that are offset by potential de-rating of plant efficiency and product specification. Standardization allows the designer and customer to focus easily on integrating the multiple processing packages that make up a plant, creating a seamless, smooth-running operation, he said.

Customization can complicate a project because it requires engineering optimization for a specific situation. That may require different vendors and differing operating specifications. The aim of customization is to focus on potential operating expenditures, and the expense of construction and design, to provide a better return on investment for a build-to-suit facility, Laughter added.

“You’re probably going to have to work through some one-off issues” in a custom design, “a little different blend of issues,” he added.

John Mak, technical director-engineering and senior fellow for Fluor USA. Source: Hart Energy John Mak, technical director-engineering and senior fellow for Fluor USA, then gave the DUG Permian audience several examples and a case study of when and how a customized design makes economic sense. His examples compared a standardized cryogenic design to reflux (recirculating) or custom-cryogenic designs. He explained that customized designs may be worthwhile for plants built to treat rich-gas streams—where the plant’s fee gas stream can yield more than 6 gallons of gas liquids per thousand cubic feet—or there is a need for higher inlet stream pressures, greater than 1,000 psi.

Mak discussed the attributes of Fluor’s Advanced Deep Dewpointing Process, which can increase propane recovery using an ethane reflux process at lower feed-gas pressures without a turboexpander. Or, it can increase ethane recovery using a methane reflux.

He provided a case study that covered specifics of one Fluor customer’s “gas plant that has been operating quite well for 20 years” with a potential 95% ethane recovery, although Mak did not specify which plant due to confidentiality concerns.

Laughter closed by noting that design and approval timing varies with the amount of customization a customer requires—an important cost component. A standard, off-the-shelf design might take as little as nine to 10 months. But “it can take longer as you weave more and more preferences, or company standards and specifications, into the mix,” he added, and a fully customized plant might take 18 months to design due to additional review and approval steps.

Paul Hart can be reached at pdhart@hartenergy.com.