Enhanced Oil Recovery (EOR)
Tertiary recovery methods — CO2 injection, chemical, or thermal techniques — used to recover oil left behind after primary and secondary production.
Enhanced oil recovery (EOR), also called tertiary recovery, is the third and most advanced stage of getting oil out of a reservoir. It uses techniques that change how the remaining oil behaves: injecting carbon dioxide or other gases to dissolve into and mobilize the oil, chemical floods that reduce surface tension, or thermal methods like steam that thin heavy oil so it can flow. The goal is the oil that primary pressure and a waterflood left stranded in the rock.
EOR follows secondary recovery and is capital- and technology-intensive, so it is reserved for fields where the prize justifies the spend. CO2 floods in particular have revived large mature oil fields for decades of added production.
For a mineral owner in a field targeted for EOR, the upside is a longer-lived royalty stream; like secondary recovery, it is typically run across a unitized field, which can affect how your decimal interest is calculated.