President Ford and oil prices?

In 1975 Ford asked for tariffs on imported oil, an end of price controls on domestic oil, and a new tax on domestic oil. Ford wanted to stimulate domestic oil production and he believed the price would drop in the long term as the supply of oil increased. I understand why he would do the first two to stimulate the domestic oil production, but not the tax. Why would he put a tax on domestic oil if he wanted production to increase?