Fluid injection system and related methods

A method of removing obstructing fluid plugs from a base section of a riser, which base section extends between a receiving end connected to an upright section of the riser and an emitting end of the riser connected to a subsea template located on a seabed, which subsea template is further connected to a wellhead for a drill hole to a subterranean void into which fluid received via the riser is to be injected from the subsea template, the method comprising:

• (A) heating at least one assisting liquid to a predetermined temperature, the heating being effected in a vessel,
• (B) forwarding at least one transport container holding the at least one heated assisting liquid from the vessel to a storage container in the subsea template,
• (C) injecting the at least one heated assisting liquid from the storage container into at least one injection point in the base section,
• (D) injecting, from the vessel at least one heated assisting liquid in the upright section of the riser, and
• (E) repeat steps (A) through (D) until any plugs in the riser have melted away.