Oilfield heat exchanger

2) A fluid heating system comprising:

• a) a primary heat exchanger;
• b) a primary heat source;
• c) a secondary heat exchanger;
• d) a secondary fluid that contains petroleum products;
• e) a closed coolant loop connected to the primary heat exchanger and to the secondary heat exchanger;
• f) a liquid coolant contained within the closed coolant loop, such that when the system is in operation, the coolant is heated by the primary heat source and the secondary fluid is heated by the coolant.

3) A fluid heating system, comprising:

• a) a liquid-to-liquid, plate-type primary heat exchanger;
• b) a primary liquid heated by a diesel engine, the primary liquid passing through the primary heat exchanger when the system is in operation;
• c) a closed coolant loop connected to the primary heat exchanger and containing a coolant, wherein the coolant passes through the primary heat exchanger and is heated by the primary liquid when the system is in operation;
• d) a secondary heat exchanger connected to the closed coolant loop, wherein the coolant passes through the secondary heat exchanger when the system is in operation;
• and,
• e) a secondary fluid that passes through the secondary heat exchanger and is heated by the coolant when the system is in operation, and wherein the secondary fluid contains petroleum products recovered from an operating well.

20) A method of heating a fluid comprising:

• a) operating a diesel engine;
• b) removing heat from the diesel engine by transferring thermal energy from the engine to a primary liquid;
• c) flowing the primary liquid through a first primary heat exchanger, where the primary liquid transfers thermal energy to a closed loop coolant flowing through the first primary heat exchanger;
• d) flowing hot hydraulic fluid through a second primary heat exchanger, where the hot hydraulic fluid transfers thermal energy to a closed loop coolant flowing through the second primary heat exchanger;
• e) flowing the closed loop coolant through a secondary heat exchanger, where the closed loop coolant transfers thermal energy to a secondary fluid flowing through the secondary heat exchanger, and wherein the secondary fluid is a mixture of petroleum products recovered from an operating well.