This is a protection frame. Made from scaffolding. Usually we are using protection frame from beam. Since well configuration on wellhead platform is various, and high risk installation method, we start using scaffolding.
Protection frame is used to protect running well from falling object, crane boom failure or any unwanted activity that could shutting down well. Since wellservice activity is on unprotected well, this protection frame is essential to ensure gas/oil production not significantly decrease due to risk exposure during welllservice activities.