The 21-year-old has represented Ulster at all levels and made his senior debut for the province in a pre-season friendly away to Harlequins in August 2010.
He was a member of the Ireland Under-20 squad that won the 2010 U-20 Six Nations title and also competed in the IRB Junior World Championship later that year.
Commenting on his new deal, Heaney said: "I am delighted to be extending my contract with Ulster. It was a great opportunity to have been given the initial four-month contract and I am pleased that I will be able to stay and to continue to represent my province."