This document discusses chemical injection in offshore production systems. It explains that chemicals are used to address various threats to production like emulsions, foaming, blockages, and corrosion. For subsea and topside processing, chemicals like demulsifiers, anti-foams, corrosion inhibitors, asphaltene/wax inhibitors, scale inhibitors, and methanol are injected to prevent issues. For water injection, chemicals like hypochlorite, poly-electrolytes, oxygen scavengers, biocides, and scale inhibitors are used to address biofouling, filtration problems, oxygen, bacteria, and scale formation. The document provides details on the functions of these various chemicals.