Texas and other states allow separation of mineral interests from surface interests. Agreements that assign “oil, gas, and other minerals” provide the legal right to produce salt, sulfur, and other minerals in addition to oil and gas.

Caverns from Salt Mining
Salt mining creates empty caverns within the subsurface formation. Historically, assignments of minerals did not address ownership of the empty caverns because the caverns had no value.

Technological developments have created a market for the use of empty caverns to store oil and gas. A mineral interest owner, whose interest included salt, wanted to store oil and gas produced from other properties in caverns created by extracting the salt. It asserted its mineral interest in the salt also meant it owned the caverns.

Minerals, Not Empty Spaces
The Supreme Court of Texas (SCOTX) unanimously said no to the mineral interest owner. A grant of “minerals” does not imply a grant of empty spaces, even if the interest owner created the spaces by extracting its minerals. The caverns remained the property of the surface owner, even though they were far below ground.

Breadth of Surface Ownership
In Texas, “surface” ownership includes areas that are far below what many consider the “surface.” Specifically, the surface includes “the space under the property’s surface, including the space contained within hollowed-out salt formations.”

SCOTX acknowledged that mineral interest owners have certain rights to use the “surface” to produce minerals. To the extent a cavern might assist oil and gas production from the same property where the cavern is located, the decision might have been different. However, SCOTX held that ownership of salt does not give the right to use the caverns created by salt extraction to store oil and gas produced from other properties.

To see the opinion https://txcourts.gov/media/1460523/220878.pdf