FAIRFAX, Va., May 11— The Mobil Corporation has made what it calls a "significant discovery" of liquid petroleum off Nigeria near the state of Akwa Ibom.

Mobil, the second-biggest United States oil company, did not specify whether its initial well in the Kpono area produced oil or condensate, a light petroleum substance rich in highly valued products useful to chemical and gasoline makers.

Its Kpono West No. 1 well produced 17,000 barrels of liquid petroleum a day during tests. Mobil said the liquid had a specific gravity between 45 and 49 on an American Petroleum Institute scale. That's lighter than West Texas Intermediate crude and Bonny Light, Nigeria's benchmark crude.

Mobil made smaller discoveries off the Nigeria coast and off Equatorial Guinea -- both within miles of the Kpono well -- earlier this year.

Mobil is part of a joint venture controlling the prospect. The Nigerian National Petroleum Corporation, the state-owned oil company, owns the rest.