Underground Storage Goes Midstream

Midstream enterprises that store and consume natural gas and natural gas liquids have discovered the benefits of using underground caverns to hold their hydrocarbon supplies.

U.S. companies that handle midstream operations in the oil and gas industry—the stage that includes the reprocessing, storing and transporting of oil, natural gas and natural gas liquids—have a few options to consider when they go shopping to store energy.

Above-ground tanks are a popular choice and hard to miss. One only needs to drive over Houston’s Beltway 8 East bridge, north of the Houston Ship Channel, to get a bird’s-eye view of a huge tank farm. What is hidden from view is the extensive network of underground storage facilities—facilities that contain natural gas and natural gas liquids in underground chambers called caverns—that serve the midstream.

“Underground storage is a cost-effective, safe and long-term solution for storing industrial quantities of hydrocarbons,” said Nils Skaug, WSP USA senior vice president, engineering. “WSP has supported midstream clients for decades with its ‘one-stop-shopping’ storage solution, ranging from planning, engineering and permitting to cavern construction.”

A Storage Solution Case Study

WSP was selected by a major U.S. midstream company to manage the development of a cavern to store ethane, a natural-gas-liquid derivative.

Cavern permitting was completed early in the project, which enabled a quick turnaround on securing the drilling permit. WSP inspected the client’s existing leaching facility, including tanks, pumps, piping, valves and controls to ensure they were ready for operation.

Following inspection, WSP reconditioned and installed pumps, valves and meters. A 2,000-horsepower, triple-electric drilling rig was mobilized at the site to safely drill the massive well to the required depth in the natural salt-dome formation.

“Reusing existing assets was important to help keep costs as low as possible,” said Klaus Buschbom, WSP USA senior vice president, drilling and well interventions. “Drilling and completions wrapped up at about the same time that the overhaul of the leach plant was finished, which set the stage for leaching to begin.”

WSP provided the specialized operations staff and expertise to safely circulate water and produce brine, thus creating the underground cavern. As the cavern neared completion, the brine was pumped into several injection wells—which had been drilled by WSP and approved by the appropriate regulatory body—for safe disposal in underground formations. Leaching was expected to take more than a year to complete, at which time the well would be tested and put into service storing ethane.

img-underground-storage-three-rigs

©WSP USA

WSP conducts a drilling project using three rigs on a single Texas site.

Behind the Scenes

A team of procurement and project-control specialists hovered over every project detail to ensure that the right materials and subcontracts were available in the field when needed. The team also ensured that the client was always kept up to date on safety; drilling progress metrics; plant repair, tank restoration and procurement status; cost projections and other critical project-control activities.

“By the time the new cavern well was turned over for leaching, the client knew exactly how much it cost to drill and complete the well—as well as how much was spent preparing the pumps and other equipment—so that the well could be leached,” Skaug said. “WSP delivered on its commitment to provide the client with a ‘no surprises’ experience.”

Several factors contributed to the success of this project. Securing the cavern permitting early in the project phase allowed the drilling permit application to be processed routinely. And when an ethane well was required later in the project, WSP was in position to quickly move forward with plans to drill the well.

“Health, safety and environment (HSE) took top priority with this project, and WSP’s Zero-Harm safety policy governed this project,” Buschbom added. “This meant that it was not enough to work safely; teams proactively looked out for one another on every step of the job.”

WSP’s attention to managing HSE was in line with the client’s priorities, resulting in the completion of a well-thought-out and enduring storage cavern.

For more information about WSP’s work in underground storage and disposal, visit www.wsp.com/en-US/hubs/underground-storage.

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