Non-intrusive rheometer for use in well operations

A method of determining a viscosity of a fluid in real time as the fluid flows in a subterranean well, the method comprising:

• connecting a main flow passage between a pump and a tubular string extending into the well, so that the fluid flows from the pump to the tubular string through the main flow passage;
• connecting a flow restrictor in the main flow passage;
• connecting a bypass flow passage in parallel with the main flow passage, so that an inlet of the bypass flow passage is in communication with a first section of the main flow passage and an outlet of the bypass flow passage is in communication with a second section of the main flow passage downstream of the first section;
• connecting a mass flowmeter and a variable flow restrictor in the bypass flow passage, so that the fluid flows through the mass flowmeter and the variable flow restrictor;
• and
• connecting at least one viscometer to the bypass flow passage.