London-listed Premier Oil saw profits rise during the first half of 2013 as revenues rose and exploration expenses shrank.

The company posted a net profit of $161.1 million for the first six months of the year, compared to a profit of $145.8 million during the first half of 2012.

Helping lift profits was a rise in sales revenues in the first half of 2013 to $757.8 million, up from the $744.3 million generated during the same period a year earlier.

Also boosting profits was a reduction in exploration expenses, from $77.9 million to $7.7 million, which helped offset a 19.9% rise in the cost of sales to $472.2 million.

Premier said the lower exploration costs reflected a a successful exploration track record in the first half of the year, while adding the increased sales costs reflected unplanned maintenance costs in the Balmoral area and start-up cost on the Huntington field, off the UK.

Output was steady year-on-year, rising from 58,400 barrels of oil equivalent per day in the first half of 2012 to 58,600 boepd this year, with Premier noting strong reservoir performance across its portfolio had been offset by the slow ramp up of production from the Huntington field in the UK and lower gas production rates from Chim Sao in Vietnam.

Premier said its full year production target of 63,000 boepd was now dependent on the performance of the Huntington field during the second half of the year.

The field was shut-in earlier this month due to safety issues relating to the cargo tank venting system on the floating production, storage and offloading vessel.

Gas venting from the cargo tanks is being picked up by the gas detection system at deck level resulting in production being shutdown whenever the wind speed falls to below five knots.

Premier said in its financial results on Thursday that it expected the issue to be resolved once the primary hydrocarbon blanketing system, which recycles gas from cargo tanks, is commissioned later this month.