Managing previously abandoned xxxxx Sample Clauses

Managing previously abandoned xxxxx. ‌ Previously abandoned - and therefore practically inaccessible - xxxxx have been considered to be the major concern regarding long term safety and integrity of CO2 storage in depleted hydrocarbon fields (e.g. IEA-GHG, 2009 and references therein). In such cases, drilling, completion and plugging were performed at a certain time in the past and not from the viewpoint of long-term storage of CO2. It is uncertain whether the current state of the wellbore materials is still of adequate quality (along the caprock level). Chemical degradation of wellbore materials, pressure and temperature cycles during (xxxx-and-puff) production and depletion of the reservoirs could have induced mechanical defects on the primary cement sheath (and its interfaces) of former production xxxxx. Extensive risk assessment, including an accurate evaluation of the actual state of the wellbore materials, has to be performed in order to ensure that the quality of the well barriers matches the safety requirements for geological CO2 storage. In case of lacking data and/or if the current state of the wellbore materials do not fulfil the requirements for CO2 storage, the well would require remediation in order to match safety standards that are sufficient for long- term geological storage of CO2. This would involve locating, re-entering and re-abandoning the previously abandoned well. Although technically challenging, this may be feasible, but would introduce high costs. If an abandoned well was found to be of inadequate integrity for CO2 storage, the same standard state-of the art abandonment practices as for accessible xxxxx have to be implemented after the re-entry is carried out successfully. Often, previously abandoned xxxxx do not match safety standards for CO2 storage. If (adequate) regulations were in place at the time of abandonment, a proper evaluation of the actual state of the well barrier materials is challenging. Consequently, the integrity of old xxxxx, particularly if critical data is missing, is difficult to predict. Well integrity management systems (XXXX) have been applied for many years in the industry and are currently being further developed in order to provide a risk-based methodology to assess the integrity of (abandoned) xxxxx with respect to CO2 storage requirements (e.g. Le Guen et al.,2009, 2011). These tools present a promising solution for a quantitative evaluation of wellbore materials, but still have to be improved, particularly in terms of accuracy, uncertai...