"The placement was heavily oversubscribed. The initial offering was for $US200 million," said Santos's managing director, John Ellice-Flint.

"As a result, Santos has been able to refinance its maturing debt on very favourable terms taking advantage of the lowest interest rates in 30 years."

Santos said proceeds from the issue would be used to repay short-term debt and some medium and long-term debt maturing within the next two months.