Systems and methods for heating oil stored in an offshore vessel or production platform

A method for heating and circulating oil stored in an offshore structure, the method comprising:

• (a) pumping oil stored in an inner cavity of a storage compartment disposed in the offshore structure to a heater disposed on the offshore structure, wherein water is disposed with the oil in the inner cavity of the storage compartment;
• (b) heating the oil with the heater during (a);
• (c) returning the oil from the heater to the inner cavity of the storage compartment after (b), wherein the oil is returned to the inner cavity of the storage compartment at a location positioned vertically below a location where the oil is pumped from the inner cavity of the storage compartment;
• (d) determining a vertical position of an oil-water interface between the oil in the inner cavity of the storage compartment and the water in the inner cavity of the storage compartment;
• (e) selecting the location where the oil is returned to the inner cavity of the storage compartment during (c) in response to the vertical position of the oil-water interface in the inner cavity of the storage compartment.

A system for heating and circulating oil stored in an offshore structure, the system comprising:

• a buoyancy compartment disposed in a floating hull;
• an oil storage compartment disposed in the floating hull below the buoyancy compartment, wherein the oil storage compartment has an inner cavity configured to store oil;
• an oil suction line having an inlet disposed in the inner cavity, wherein the oil suction line is configured to draw oil from the inner cavity through the inlet;
• an oil heater coupled to the oil suction line and configured to heat oil passing through the oil suction line;
• and
• a return line coupled to the oil heater and including an outlet disposed in the inner cavity of the oil storage compartment, wherein the outlet is vertically positioned below the inlet of the oil suction line, wherein the return line is configured to transport oil from the oil heater to the inner cavity of the oil storage compartment.