HYDROCARBON RESOURCE RECOVERY APPARATUS INCLUDING A TRANSMISSION LINE WITH FLUID TUNING CHAMBER AND RELATED METHODS

An apparatus for heating a hydrocarbon resource in a subterranean formation having a wellbore extending therein is provided. The apparatus includes a radio frequency (RF) antenna configured to be positioned within the wellbore, a transmission line configured to be positioned in the wellbore and coupled to the RF antenna, and an RF source configured to be coupled with the transmission line. The transmission line includes at least one transmission line tuning section including an inner conductor, an outer conductor surrounding the inner conductor, and a liquid-blocking plug between the inner and outer conductors to define a tuning chamber configured to receive a dielectric liquid with a gas headspace thereabove.