Midland-based Gravity Oilfield Services said last week it shipped more than 1,000 storage tanks in recent weeks and has another 4,000 available to operators in Permian Basin, Eagle Ford and Haynesville. “As a result of the decline in their normal use for frac or mud tanks, we are making them available for crude oil storage,” Rob Rice, CEO and president, said. The tanks most often are used for temporary storage of liquids, but are being made available to customers for long-term use. “The highest demand to date has been in Oklahoma,” Rice said, “but we are seeing increasing demand in the Permian.”