| dc.description.abstract | Well integrity is a crucial phase of well design and construction, as such multiple barriers are usually installed in wells to prevent any migration of formation fluids. One of these barriers include the elastomeric sealing system or seal assembly. Limited knowledge is available on elastomer behavior in harsh downhole conditions. Lack of adequate knowledge makes elastomer selection during well design a problematic phase. This thesis reviews literature on elastomer performance under various conditions and expounds on the chemical reactions involved in the failure mechanisms of elastomers. Experiments have also been conducted on three popular elastomers: Nitrile butadiene rubber (NBR), Ethylene propylene diene monomer (EPDM), and Fluoroelastomers (FKM) in the presence of hydrogen sulfide (H2S), methane (CH4), carbon dioxide (CO2) and brine. The performance of these elastomers is also discussed. Experiments conducted help us make an informed decision thus classifying the elastomers based on the degree of degradation under these harsh downhole conditions.
The second barrier is the set cement. In Oil and Gas drilling operations, cement is used to maintain wellbore integrity by preventing the movement of formation fluids through the annular space outside the casing. However, in gas migration prone regions, cement sealability may be inadequate. The reduced sealability also makes such regions prone to well instability. This thesis reviews gas mitigation approaches according to published literature. Some slurry designs published in literature are used in the experiments and the results are reported herein. A novel gas tight cement slurry is designed to prevent gas migration. This cement slurry has been tested in different pipe sizes and has proven to mitigate gas migration of any sort. | en_US |
