SECURITIES AND EXCHANGE COMMISSION
                              Washington, DC 20549



                                    FORM 8-K



                             Current Report Pursuant
                          to Section 13 or 15(d) of the
                         Securities Exchange Act of 1934



    Date of report (Date of earliest event reported)        September 20, 2004
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                               UNOCAL CORPORATION
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             (Exact name of registrant as specified in its charter)



                                    Delaware
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                 (State or Other Jurisdiction of Incorporation)



    1-8483                                   95-3825062
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(Commission File Number)                (I.R.S. Employer Identification No.)



2141 Rosecrans Avenue, Suite 4000, El Segundo, California         90245
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(Address of Principal Executive Offices)                       (Zip Code)



                                 (310) 726-7600
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              (Registrant's Telephone Number, Including Area Code)

Check the appropriate box below if the Form 8-K filing is intended to
simultaneously satisfy the filing obligation of the registrant under any of the
following provisions:

|_| Written communications pursuant to Rule 425 under the Securities Act
|_| Soliciting material pursuant to Rule 14a-12 under the Exchange Act
|_| Pre-commencement communications pursuant to Rule 14d-2(b) under the
    Exchange Act
|_| Pre-commencement communications pursuant to Rule 13e-4(c) under the
    Exchange Act



Item 8.01.  Other Events.

       On September 20, 2004, Unocal Corporation ("Unocal") announced by press
release that it had joined with representatives from other participating
companies on September 20, 2004 in signing a resolution sanctioning the Phase 3
development of the Azeri-Chirag-Deepwater Gunashli ("ACG") field in the
Azerbaijan sector of the Caspian Sea. The Phase 3 project represents the next
significant development phase of the ACG production-sharing agreement ("PSA"),
which is operated by Azerbaijan International Operating Company ("AIOC"). Phase
3 offshore facilities will comprise of a 48-slot drilling, utilities and
quarters platform that is bridge-linked to a production, compression, water
injection and utilities platform in Deepwater Gunashli. The start of oil
production from Phase 3 is currently planned for mid-2008. All associated gas,
except for fuel requirements, will be delivered to the State Oil Company of
Azerbaijan ("SOCAR").

       Unocal Khazar Ltd., a wholly owned Unocal subsidiary, has a 10.3 percent
working interest in the ACG PSA and AIOC. Ownership in the AGC PSA and AIOC also
includes SOCAR (10% working interest) and eight other foreign oil companies: BP
(operator, 34.1%), INPEX (10.0%), Statoil (8.6%), ExxonMobil (8%), TPAO (6.8%),
Devon (5.6%), Itochu (3.9%), and Amerada Hess (2.7%).

       The development of the ACG field has been divided into four parts: Early
Oil and Phases 1, 2 and 3. The Early Oil project is currently producing about
148,000 barrels of oil per day (gross). Phase 1 is expected to come on line in
2005; Phase 2 in 2006. Total production from the ACG field is expected to peak
at more than 1.1 million barrels of oil per day in 2009 after Phase 3 comes on
line.

This filing contains forward-looking statements about matters such as drilling
and development plans, and production rates, timing and growth. Although these
statements are based upon Unocal's current expectations and beliefs, they are
subject to known and unknown risks and uncertainties that could cause actual
results and outcomes to differ materially from those described in, or implied
by, the forward-looking statements, including volatility in commodity prices and
the effectiveness of Unocal's hedging program; the accuracy of estimates and
judgments regarding hydrocarbon resources and formations; decline rates of
producing properties; adverse geological and other operational factors; the
extent of Unocal's operating cash flow and other capital resources available to
fund its capital expenditures; international and domestic regulatory, political,
and economic factors; performance by foreign government entities, joint venture
partners, independent contractors, equipment suppliers and other third parties;
competition within Unocal's highly competitive industry; and other risks and
uncertainties discussed in Unocal's 2003 Annual Report on Form 10-K, as amended,
and subsequent reports filed by Unocal with the Securities and Exchange
Commission (SEC File No. 1-8483). Copies of Unocal's SEC filings are available
from Unocal by calling 800-252-2233 or from the SEC by calling 800-SEC-0330. The
reports are also available on the Unocal web site. Unocal undertakes no
obligation to update the forward-looking statements in this filing to reflect
future events or circumstances. All such statements are expressly qualified by
this cautionary statement.


                                    Signature

Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned, thereunto duly authorized.


                                                  UNOCAL CORPORATION
                                                     (Registrant)





Date: September 21, 2004                       By: /s/ JOE D. CECIL
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                                                  Joe D. Cecil
                                                  Vice President and Comptroller