Feb 5 (Reuters) – South African petrochemical firm Sasol forecast a fall of up to 36% in half-yearly earnings on Wednesday, mainly due to a decline in oil prices and lower sales volumes.

Sasol said in a trading update that it expects its headline earnings per share (HEPS), a profit measure widely used in South Africa, to come in between 13 rand and 15 rand ($0.6955-$0.8025), down from 20.37 rand in the same period last year.

The company, which produces chemicals and liquid fuels from coal and gas, said the decline was primarily because of a 13% fall in the average rand Brent crude oil price per barrel, as well as a significant drop in refining margins and fuel price differentials.

A 5% decrease in sales volumes due to lower production and market demand also hurt income, Sasol said.

The company will release its half-yearly results on Feb. 24.

($1 = 18.6923 rand)

(Reporting by Nelson Banya; Editing by Subhranshu Sahu)