PetroChina will complete the expansion of its unit Daqing by June 2012, doubling the plant's ethylene capacity to 1.2 million tonnes per year, about a year later than an earlier plan, an industry official said on Tuesday.

It took an additional year for PetroChina Co Ltd to develop the technology needed for the new ethylene unit, delaying construction, said the official with direct knowledge of project. PetroChina began expansion at Daqing in northeast China in September 2009, and now aims to complete the work by June 30, 2012, versus an earlier schedule of 2011.

At least two new major ethylene facilities have started in this year, one in eastern Ningbo and the other in northern Tianjin, both operated by top refiner China Petroleum & Chemical Corp (Sinopec), part of a long-term building boom in the petrochemical sector.