Oil and gas producer Unocal ( UCL) lowered its fourth-quarter earnings estimate, citing a lower estimate of crude oil prices and additional costs related to its purchase of former unit Pure Resources.

The company dropped its estimate for fourth-quarter "adjusted" earnings to 30 cents to 40 cents a share. Consensus estimates had been calling for a fourth quarter profit of 52 cents according to First Call.

Unocal shares were trading down 83 cents at $30.82 in pre-market action.

The earnings forecast excludes expenses of $22 million to $25 million, or 9 cents to 10 cents a share, reflecting additions the company must make to its environmental-remediation reserves.

Despite the recent runup in crude, Unocal lowered its estimate of the average fourth-quarter price to $28.10 a barrel, down $1.65 from its previous forecast. The company's earnings fall about 4 cents a share for every dollar it shaves from the crude estimate.

The company's earnings will also be reduced because of the revaluing of options it must exchange for options in Pure Resources, the former unit it bought out in October. Unocal's common shares have gained about 15% since the acquisition.