Piping system having an insulated annulus

An offshore oil well installation comprising:

• a production string extending in the ocean from a subsea well to a rig for flow of hot well fluid therethrough;
• a riser extending about the production string for isolating the production string from cold ocean water;
• an annulus between the production string and the riser;
• at least one temperature sensitive operating device in the annulus;
• insulation in the annulus between the production string and the riser to insulate the temperature sensitive operating device from the heat generated by flow of hot well fluid in the production string and keeping the temperature sensitive operating device exposed to cooling generated by cold ocean water surrounding the riser.

A subsea control module for an offshore oil well installation, the subsea control module comprising:

• an inner mandrel;
• an outer riser in which the inner mandrel is received and for being surrounded by ocean water;
• operating devices mounted to be disposed about and to extend along the inner mandrel;
• and
• insulation secured to extend about and along the inner mandrel adjacent to the operating devices.