The assurance came after Total said it had warned Shell its Shearwater field may be at risk from the same corrosive drilling fluids which sparked the North Sea's worst gas leak in 20 years.
The fluids implicated in the leak at Total's Elgin field last March, such as calcium bromide, are commonly used in such deep-sea wells.
The Elgin platform leaked gas for more than seven weeks and cost Total around £1.6 million a day in relief operations and lost income.
Experts fear another leak, as operators turn to deeper, hotter and higher pressure fields to boost production. The North Sea is host to the highest number of high-pressure, high-temperature (HPHT) reservoirs of any mature oil and gas producing basin.
Like Elgin, Shell's Shearwater field is fed by a HPHT reservoir where temperatures can reach 140C.
However, a spokeswoman for Shell said the company did not use bromide-based fluids at the Shearwater oil and gas platform.
She added: "Shell is redeveloping the Fulmar reservoir from the Shearwater platform in line with UK regulatory requirements. We participate actively in industry knowledge-sharing fora and are confident in the safety of our well designs and operations."
Shell began a redevelopment programme for Shearwater in 2011. The redevelopment involves the abandonment of the original production wells and a drilling programme for the redevelopment of the Fulmar reservoir. It is expected to take several years to complete. Redevelopment was initiated, as part of normal field development, to access the remaining resources in the ground and maximise recovery.