ISLAMABAD, Sept 15: The Oil and Gas Regulatory Authority (Ogra) on Friday announced that prices of petroleum products would remain unchanged for the next fortnight. The price determination is carried out by Ogra in accordance with the formula prescribed by the government. It requires that the price be based on average Gulf prices for the last fortnight for naphtha, diesel, kerosene and HSFO, to which inland freight equalisation margin is added, which reflects estimated transpiration cost of the products to the 29 depots in the country.