Exhibit 99.1.

           MARATHON SAKHALIN LIMITED AND SHELL SAKHALIN HOLDINGS B.V.
                           COMPLETE EXCHANGE AGREEMENT

HOUSTON, DECEMBER 6, 2000 -- Marathon Sakhalin Limited ('Marathon') and Shell
Sakhalin Holdings B.V. ('Shell') today announced completion of the exchange
agreement that was signed in October 2000, relating to the transfer of
Marathon's 37.5 per cent interest in Sakhalin Energy Investment Company Ltd.
('Sakhalin Energy') to Shell.

In exchange for this, Marathon has acquired:

- - Shell UK Limited's 28 per cent interest in the BP-operated Foinaven field,
  located in the Atlantic Margin west of the Shetland Islands in the UK
- - all of Shell UK Limited's interests in discoveries and prospects on license
  areas adjacent to the Foinaven field
- - a 3.5 per cent overriding royalty, payable from Shell's working interest,
  on 100 percent of the production from an eight block area in the Gulf of
  Mexico, which includes the producing Ursa field and the recently announced
  Princess discovery

In addition, Marathon has been reimbursed for its expenditures on the Sakhalin
project for the year 2000.

The remaining shareholders in Sakhalin Energy have entered into a revised
Shareholder Agreement that will govern the future operations of Sakhalin Energy.
Under the new Shareholder Agreement, Sakhalin Energy will act as an integrated
operator, with Shell providing both upstream and LNG services to the venture.

Dave Golder, Marathon's senior vice president for Commercialization and
Development said: "Sakhalin is without doubt a world-class project. For Marathon
it was the right project, but at the wrong time. High levels of capital
investment for several more years without significant near to mid-term returns,
simply didn't fit our strategic needs.  However, the experience we take with us
from the Sakhalin project will be important for Marathon's future international
success, an area that we see providing much of our long-term growth.  As we move
ahead, we're certainly not averse to doing business in Russia and, with the
right opportunity, we would be happy to return."

Marathon Sakhalin Limited is a subsidiary of Marathon Oil Company, which is part
of the USX-Marathon Group (NYSE:MRO), a unit of USX.

Notes for Editors:

- - Sakhalin Energy Investment Company Ltd. was established in April 1994 to
  carry out the implementation and development of the Sakhalin II Project -
  Russia's first project to be realised under the terms of a Production Sharing
  Agreement (PSA).
- - The project covers two fields, Piltun-Astokhskoye, primarily an oil field,
  and Lunskoye which is primarily a gas field.
- - Under the Agreement, entered into by the Sakhalin Oblast, the Russian
  Federation and Sakhalin Energy in 1994, direct investment in the Project will
  amount to about $10 billion.
- - First oil was produced in July 1999, from the Piltun-Astokhskoye (PA)
  field, with the first export of crude in September 1999.
- - The project will now move to gas field development and LNG plant
  construction phase, once gas sales agreements are in place.