The control of inorganic scale (carbonate/sulphate) has been a challenge to the production of hydrocarbon and associated water for over 50 years. The current trend in the industry to develop satellite fields with longer tie backs and in deeper water has resulted in new challenges to control such scale deposits during hydrocarbon production. The lower fluid temperatures that are present in these subsea developments during fluid production increases the sulphate scaling tendency and makes scale control very difficult over the long residence time now experienced due to the tie back lengths. The introduction of methanol, mono ethylene glycol (MEG) or tri ethylene glycol (TEG) to control hydrate risk presents new challenges in terms of increased scale tendency (dehydration of brine) and interactions of the hydrate control chemicals with scale inhibitor performance.
For these challenging environments a full understanding of the evolution of the brine chemistry through the field life cycle is essential (types of scale, supersaturation changes). This paper will outline the process by which this risk assessment of scale formation in the presence of hydrate control chemicals is made and how the scale control measures for effective scale management of subsea developments is carried out. Development of new and improved scale inhibitors for these types of applications within both methanol and MEG hydrate control chemicals will be outlined. Field case studies from the North Sea and Southern Africa will be used to illustrate the scale control challenges and how they have been overcome with engineering and production chemical solutions.