Schlumberger has a ton of experience plumbing the depths of the earth to find, measure and manage oil and gas deposits. Why not take that expertise and apply it to underground water?

That's one of the focuses of the French oil and gas services giant's water services divisions, and it could be a growing alternative to the pressing question of how to store the limited amount of fresh water available for human endeavor.

Less than 1 percent of the world's fresh water is free flowing, said Jerry Rowe, vice president of operations for Schlumberger Water Services, speaking Tuesday at the AlwaysOn GoingGreen conference in Sausalito.

Of the remainder, about 75 percent is trapped in ice sheets, which aren't exactly available to be moved to where humans need it, he said. But about a quarter of the rest is underground – and humans have been tapping that source for centuries.

That, of course, has created its own set of problems, as observers of depleting aquifers in the American Midwest and California's Central Valley can attest.

"We've gotten the easy [underground water] in a lot of places, and we haven't gone after the more difficult supplies," said Rowe. "And subsurface can be used for storage. The key to it is to understand it... and let decision-makers have the tools to manage that as a long-term resource."

That's something Schlumberger is working on in projects in Saudi Arabia and Chile to store water from massive desalination plants, he said. When desalination plants need to be shut down – say, when a poisonous "red tide" comes along the shore where the plant's intake pipes are – desalination plants need a supply of stored water to keep the taps flowing, he said (see Desalination: Can the Technology Go Elsewhere?)

And drawing on the expertise of a company like Schlumberger is important, he added. Of the many aquifer storage projects underway around the world, roughly half have failed because of poor design and management, he said.

Pumping water into existing aquifers can have unforeseen consequences, he noted. Take the storage projects in Florida for example. In these projects, the clean water being pumped underground reacted with the clean water already there in an unforeseen way to raise the arsenic level beyond healthy levels, he said.

The result is that new technologies to identify such threats, as well as to better understand the flows of water in aquifers, still need to be proven out to expand the market for aquifer storage, he said.

Another market Schlumberger Water Services has under consideration is using the earth's natural filtering to clean salty or brackish water for desalination, he said. Filtering the intake for such plants can make up $30 million of a typical $500 million desalination plant, he said.

Then there's the tricky question of how to treat brackish water being pumped out of underground caverns or other formations to store carbon, he noted. Of course, that's not a new challenge for Schlumberger.

"In the oil and gas business, there are four barrels of water produced with every barrel of oil," he said. "If you can economically treat it, its available for use."

Schlumberger and fellow oil services giant Halliburton may have another reason to direct more technology toward water – both have come under scrutiny for the potential groundwater contamination that may come from the process of fracturing underground rock to boost oil and natural gas production.

Learn how to differentiate your company through greener product lines at Greening the Supply Chain on September 17 in Boston.