Material object or set of objects intended to prevent the transmission of pressure and fluid flow from one side of the barrier to the other side. NOTE 1 The barrier is designed to withstand all anticipated pressures at its relative position in the wellbore. It may be verified by testing to its full-anticipated load or verified by alternative evaluation (refer to 5.3.2). NOTE 2 Includes mechanical barriers, cement barriers, and hydrostatic barriers. NOTE 3 Does not include operational barriers.
Source: API RP 96, Deepwater Well Design and Construction, First Edition, March 2013. Global Standards
A physical barrier means a function that can prevent or limit harm in the event of an unwanted incident. Other acute situations may, inter alia, constitute hazard and accident situations that have occurred, weather conditions that reduce the possibility of transporting personnel from the facility etc.
Source: Guidelines Regarding the Activities Regulations, Norway, updated December 2012. Regulatory Guidance