The two companies have also formed a joint venture through a joint operating agreement to explore the area.
Beach will pay 3D Oil the $3 million in cash. 3D Oil will remain operator.
Plans include a 755 sq km seismic acquisition program in the next 12 months.
T/49P is about 20 km west of King Island at the western entrance to Bass Strait and close to Geographe and Thylacine gas fields in the adjacent permit. It has an area of 4,960 sq km in 100 m of water.