(Adds refinery margins and shares)
June 22 (Reuters) - Australian fuel supplier Caltex Australia CTX.AX said on Thursday it expects underlying half-yearly net profit to rise as much as 22 percent as it benefited from higher refiner margins and bigger volumes of premium diesel sales.
Net profit "on a replacement cost" basis was expected between A$290 million ($218.81 million) and A$310 million for the six months to June 30, 2017, up from A$254 million in the same period a year earlier, the company said in a statement.
Caltex, which owns one of Australia's four remaining oil refineries, says net profit on a replacement cost basis is a better measure of its performance because it excludes changes in the oil price. The forecast also excluded significant items for the six-month period.
The company said it expects its Brisbane-based Lytton refinery to contribute earnings before interest and tax of about A$150 million in the half-year period, up from A$92 million in the prior period, reflecting higher refiner margins.
Total transport fuels sales volumes would be 7.7 billion litres, marginally higher than the comparable period in 2016. Growth in sales volume from premium diesel would offset a forecast decline in overall premium petrol volumes.
Analysts have warned that Caltex may lose about a fifth of its full-year earnings if BP Plc BP.L buys petrol stations from supermarket chain Woolworths Ltd WOW.AX , for which Caltex is currently the supplier.
Although that deal still needs regulatory approval, Caltex has said it expects to fill the gap by the end of 2017. of the Sydney-based company rose as much as 3 percent in early trade on Thursday.
($1 = 1.3254 Australian dollars)