Frac flow-back control and/or monitoring system and methods

According to one aspect, a system is adapted to actively control one or more operating parameters associated with: a wellbore extending in a subterranean formation, and/or wellbore fluid flowing out of the wellbore via a wellhead. The system includes one or more sensors; an electronic controller adapted to receive from the one or more sensors measurement data; and a valve through which the wellbore fluid is adapted to flow. The valve is adapted to be in communication with the electronic controller. The active control of the at least one of the one or more operating parameters is adapted to facilitate: maintenance of the integrity of the wellbore, and/or enhancement of oil and/or gas production out of the wellbore. In one embodiment, the wellbore fluid flow is frac flow-back. In another aspect, a system is adapted to monitor vent gas separated from wellbore fluid flowing out a wellhead.