(Adds Sechin quotes, details, background)
MOSCOW, June 27 (Reuters) - Russia's Rosneft ROSN.MM aims to become the world's third largest gas producer and as cost-effective as Saudi Aramco, the chief executive of the world's top listed oil producer by volume wrote in an article published on Tuesday.
"We must find the tools which will allow us to increase the efficiency of the company at all stages of the production chain - from oil and gas exploration to retail sales of oil products," CEO Igor Sechin wrote in the Izvestia daily newspaper.
Rosneft last year became Russia's largest independent gas producer and ranked sixth among global, listed gas producers, Sechin said.
"Our task is to become the world's third largest (listed gas producing) company by the start of the next decade, to raise gas output to 100 billion cubic metres by 2020 and our share on the Russian market to 20 percent," he said.
The company will work to achieve production costs in line with those of Saudi Aramco in the long term, he wrote.
If oil prices stay at $40 per barrel for a prolonged period, half of global oil production would become loss-making, including in Brazil and Canada, with shale oil producers also likely to face "difficulties", Sechin wrote.
"Only producers from Russia, Saudi Arabia, as well as a number of efficient projects in the United States, Iran and in some other countries with relatively low production costs are able to remain steady at low oil prices," he wrote. "All other producers will have to go."
Rosneft plans to open a trading office in Singapore, Sechin added.
Sechin, a close ally of Russian President Vladimir Putin, said last week that Rosneft was working on a new strategy which it would present by the end of this year.
By applying new technologies, Rosneft aims to increase oil output by a total of 500 million tonnes in the next 20 years, Sechin said.