Over recent years the scaling challenges facing many HP/HT gas condensate fields, has been highlighted and detailed works describing the challenges presented in previous SPE publications. Given the severity of the scaling regime and the extremely fast reaction kinetics, several such fields have already experienced downhole carbonate scaling and therefore remediation methods are required. Moreover, the application of acid based scale dissolvers commonly used in more conventional applications represents a significant challenge with potential for enhanced corrosion or formation damage when using these potentially aggressive fluids.
This paper describes chemical selection requirements for one such field system and presents results from a range of conventional (90°C, 1 bar) scale dissolution and corrosion tests together with those from more sophisticated HP/HT (190°C; 300 bar) autoclave techniques, designed specifically to examine chemical dissolution and corrosion rates associated with the application of these fluids under severe HP/HT downhole conditions. The tests examined several different organic acid formulations including control "un-inhibited" acetic acids and various organic acids specifically formulated with corrosion inhibitors to prevent corrosion of the downhole tubulars. Results from an extensive test programme directly compare dissolution and corrosion performance measurements at both ambient and HP/HT conditions. They also serve to identify the key parameters required for the selection of such dissolution treatments, highlighting significant relative differences between different products when tested at more conventional conditions vs. HP/HT conditions. In summary the work led to the deselection of more effective dissolvers due to enhanced corrosion at HP/HT conditions. The paper therefore describes more sophisticated test methodologies for assessing scale dissolution and corrosion inhibition with these fluids under HP/HT conditions and then describes the conclusions from this work and recommendations for other similar HP/HT environments.