A large number of wells will have to be abandoned at the NCS and around the world. NORSOK D-010 states that a well that is permanently abandoned shall be abandoned with an eternal perspective and with zero leakage [1]. This is a challenge. It can be hard to predict downhole properties after a well is abandoned. One of the biggest challenges is to ensure that the barriers will keep their integrity for hundred or even thousands of years. To understand how the reservoir and well acts after it is plugged and abandoned, several mechanisms must be known. Barriers is affected by parameters like temperature, pressure and different fluids and gasses that are in contact. This thesis will review regulations and requirements for permanent well barriers, verification of permanent well barriers, barrier degradation models and degradation of cement and corrosion of casing steel due to CO2. Use of carbon capture and storage is a very popular topic, which is discussed in this thesis. This method is based on pumping CO2 into reservoirs to store it instead of releasing it to the air. Carbon dioxide is a large contributor for barrier degradation. This thesis will also look at well barrier leakage and statistics around this. It will be discussed how to cope with the leakage in permanent well barriers after a well is abandoned.

Master's thesis in Petroleum engineering