Federal trademark officials in Alexandria, Va., recently received an unusual package: a hand-delivered parcel containing vials of a clear liquid that smelled of oranges.

The sender wasn’t a crank. It was a corporate trademark lawyer representing Flotek Industries Inc., a Texas producer of hydraulic-fracturing fluids used to extract oil and gas from rocks deep in the earth.

The little bottles in the box were samples of a branding brainstorm that might be called eau de fracking: a specially developed scent that is supposed to make Flotek’s product smell like a glass of OJ. Flotek says its customers have come to associate the orange scent with its line of fracking chemicals and wants the U.S. Patent and Trademark Office to register it as a trademark.

Flotek lawyer Douglas Wolf said it was wiser to deliver the application by messenger than send it in the U.S. mail. “You can imagine the security concerns with three vials of liquid in a box,” he said.

Flotek is one of a small number of companies trying to trademark their efforts to grab customers by the nose. A U.S. ukulele company won trademark protection for a scent that—according to its application—lends its little stringed instruments a distinctive piña colada aroma.