SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                  Schedule 13D

                    Under the Securities Exchange Act of 1934

                                 Amendment No. 1


                                  Premcor Inc.
          ------------------------------------------------------------
                                (Name of Issuer)


                                  Common Stock
          ------------------------------------------------------------
                         (Title of Class of Securities)


                                   74045Q 10 4
          ------------------------------------------------------------
                                 (CUSIP Number)


                            Donald P. de Brier, Esq.
                        Occidental Petroleum Corporation
                            10889 Wilshire Boulevard
                          Los Angeles, California 90024
                                 (310) 208-8800
          ------------------------------------------------------------
            (Name, Address and Telephone Number of Person Authorized
                     to Receive Notices and Communications)


                                January 29, 2003
          ------------------------------------------------------------
             (Date of Event Which Requires Filing of this Statement)


If the filing person has previously filed a statement on Schedule 13G to report
the acquisition which is the subject of this Schedule 13D, and is filing this
schedule because of Rule 13d-l(e), 13d-1(f) or 13d-1(g), check the following box
[ ]


                               Page 1 of 18 Pages



                              CUSIP No. 74045Q 10 4
                                        -----------


                                                                   
(1)  Names of reporting persons.                                      Occidental Petroleum Corporation
     I.R.S. Identification Nos. of above persons (entities only).     95-4035997

(2)  Check the appropriate box if a member of a group                 (a)

     (see instructions)                                               (b)

(3)  SEC use only.

(4)  Source of funds (see instructions).                              OO

(5)  Check if disclosure of legal proceedings is required pursuant
     to Items 2(d) or 2(e).

(6)  Citizenship or place of organization.                            Delaware

Number of shares beneficially owned by each reporting person with:

     (7)  Sole voting power.                                          1,908,209

     (8)  Shared voting power.                                        7,126,437

     (9)  Sole dispositive power.                                     1,908,209

     (10) Shared dispositive power.                                   7,126,437

(11) Aggregate amount beneficially owned by each reporting person     9,034,646

(12) Check if the aggregate amount in Row (11) excludes certain
     shares (see instructions).

(13) Percent of class represented by amount in Row (11).              12.31%

(14) Type of reporting person (see instructions).                     CO



                               Page 2 of 18 Pages



                              CUSIP No. 74045Q 10 4
                                        -----------


                                                                   
(1)  Names of reporting persons.                                      Occidental C.O.B. Partners
     I.R.S. Identification Nos. of above persons (entities only).     73-1484588

(2)  Check the appropriate box if a member of a group                 (a)

     (see instructions)                                               (b)

(3)  SEC use only.

(4)  Source of funds (see instructions).                              OO

(5)  Check if disclosure of legal proceedings is required pursuant
     to Items 2(d) or 2(e).

(6)  Citizenship or place of organization.                            Delaware

Number of shares beneficially owned by each reporting person with:

     (7)  Sole voting power.

     (8)  Shared voting power.                                        7,126,437

     (9)  Sole dispositive power.

     (10) Shared dispositive power.                                   7,126,437

(11) Aggregate amount beneficially owned by each reporting person     7,126,437

(12) Check if the aggregate amount in Row (11) excludes certain
     shares (see instructions).

(13) Percent of class represented by amount in Row (11).              9.71%

(14) Type of reporting person (see instructions).                     PN



                               Page 3 of 18 Pages



                              CUSIP No. 74045Q 10 4
                                        -----------


                                                                   
(1)  Names of reporting persons.                                      Placid Oil Company
     I.R.S. Identification Nos. of above persons (entities only).     72-0395174

(2)  Check the appropriate box if a member of a group                 (a)

     (see instructions)                                               (b)

(3)  SEC use only.

(4)  Source of funds (see instructions).                              OO

(5)  Check if disclosure of legal proceedings is required pursuant
     to Items 2(d) or 2(e).

(6)  Citizenship or place of organization.                            Delaware

Number of shares beneficially owned by each reporting person with:

     (7)  Sole voting power.

     (8)  Shared voting power.                                        7,126,437

     (9)  Sole dispositive power.

     (10) Shared dispositive power.                                   7,126,437

(11) Aggregate amount beneficially owned by each reporting person     7,126,437

(12) Check if the aggregate amount in Row (11) excludes certain
     shares (see instructions).

(13) Percent of class represented by amount in Row (11).              9.71%

(14) Type of reporting person (see instructions).                     CO



                               Page 4 of 18 Pages



                              CUSIP No. 74045Q 10 4
                                        -----------


                                                                   
(1)  Names of reporting persons.                                      OXY USA Inc.
     I.R.S. Identification Nos. of above persons (entities only).     73-1166880

(2)  Check the appropriate box if a member of a group                 (a)

     (see instructions)                                               (b)

(3)  SEC use only.

(4)  Source of funds (see instructions).                              OO

(5)  Check if disclosure of legal proceedings is required pursuant
     to Items 2(d) or 2(e).

(6)  Citizenship or place of organization.                            Delaware

Number of shares beneficially owned by each reporting person with:

     (7)  Sole voting power.

     (8)  Shared voting power.                                        7,126,437

     (9)  Sole dispositive power.

     (10) Shared dispositive power.                                   7,126,437

(11) Aggregate amount beneficially owned by each reporting person     7,126,437

(12) Check if the aggregate amount in Row (11) excludes certain
     shares (see instructions).

(13) Percent of class represented by amount in Row (11).              9.71%

(14) Type of reporting person (see instructions).                     CO



                               Page 5 of 18 Pages



                              CUSIP No. 74045Q 10 4
                                        -----------


                                                                   
(1)  Names of reporting persons.                                      Occidental Oil and Gas Holding Corporation
     I.R.S. Identification Nos. of above persons (entities only).     95-2864974

(2)  Check the appropriate box if a member of a group                 (a)

     (see instructions)                                               (b)

(3)  SEC use only.

(4)  Source of funds (see instructions).                              OO

(5)  Check if disclosure of legal proceedings is required pursuant
     to Items 2(d) or 2(e).

(6)  Citizenship or place of organization.                            California

Number of shares beneficially owned by each reporting person with:

     (7)  Sole voting power.

     (8)  Shared voting power.                                        7,126,437

     (9)  Sole dispositive power.

     (10) Shared dispositive power.                                   7,126,437

(11) Aggregate amount beneficially owned by each reporting person     7,126,437

(12) Check if the aggregate amount in Row (11) excludes certain
     shares (see instructions).

(13) Percent of class represented by amount in Row (11).              9.71%

(14) Type of reporting person (see instructions).                     CO



                               Page 6 of 18 Pages



                              CUSIP No. 74045Q 10 4
                                        -----------


                                                                   
(1)  Names of reporting persons.                                      Occidental Petroleum Investment Co.
     I.R.S. Identification Nos. of above persons (entities only).     95-2584267

(2)  Check the appropriate box if a member of a group                 (a)

     (see instructions)                                               (b)

(3)  SEC use only.

(4)  Source of funds (see instructions).                              OO

(5)  Check if disclosure of legal proceedings is required pursuant
     to Items 2(d) or 2(e).

(6)  Citizenship or place of organization.                            California

Number of shares beneficially owned by each reporting person with:

     (7)  Sole voting power.

     (8)  Shared voting power.                                        7,126,437

     (9)  Sole dispositive power.

     (10) Shared dispositive power.                                   7,126,437

(11) Aggregate amount beneficially owned by each reporting person     7,126,437

(12) Check if the aggregate amount in Row (11) excludes certain
     shares (see instructions).

(13) Percent of class represented by amount in Row (11).              9.71%

(14) Type of reporting person (see instructions).                     CO


                               Page 7 of 18 Pages



ITEM 1.  SECURITY AND ISSUER.

Title of class of equity security:           Common Stock

Issuer:                                      Premcor Inc.

Address of principal executive offices:      1700 East Putnam Street, Suite 500
                                             Old Greenwich, Connecticut 06870


ITEM 2.  IDENTITY AND BACKGROUND.

Occidental Petroleum Corporation ("Occidental"):
------------------------------------------------

     state of organization:        Delaware

     principal business:           engaged, through its subsidiaries and
                                   affiliates, in the production, development
                                   and marketing of natural resources and
                                   chemicals

     principal business address:   10889 Wilshire Boulevard
                                   Los Angeles, California 90024

Occidental C.O.B. Partners ("OXY Partners"):
--------------------------------------------

     state of organization:        Delaware

     principal business:           general partnership, formed to engage in
                                   buying, selling, delivering and dealing in
                                   crude oil, and in any and all lawful
                                   activities directly or indirectly related or
                                   incidental to that business

     principal business address:   110 West 7th Street
                                   P.O. Box 300
                                   Tulsa, Oklahoma 74102

Placid Oil Company ("Placid"):
------------------------------

     state of organization:        Delaware

     principal business:           oil and gas exploration and production in the
                                   United States Gulf Coast, Canada and the
                                   Netherlands

     principal business address:   10889 Wilshire Boulevard
                                   Los Angeles, California 90024


                               Page 8 of 18 Pages



OXY USA Inc. ("OXY USA"):
-------------------------

     state of organization:        Delaware

     principal business:           domestic oil and gas exploration and
                                   production

     principal business address:   5 Greenway Plaza
                                   Houston, Texas 77046

Occidental Oil and Gas Holding Corporation ("OOGHC"):
-----------------------------------------------------

     state of organization:        California

     principal business:           holding company for oil and gas entities

     principal business address:   10889 Wilshire Boulevard
                                   Los Angeles, California 90024

Occidental Petroleum Investment Co. ("OPIC"):
---------------------------------------------

     state of organization:        California

     principal business:           holding company

     principal business address:   10889 Wilshire Boulevard
                                   Los Angeles, California 90024


     The name, business address and current principal occupation or employment
of each of the executive officers and directors of Occidental, Placid, OXY USA,
OOGHC, and OPIC (collectively, the "Companies") are set forth below. Unless
otherwise indicated, the business address of each such person is 10889 Wilshire
Boulevard, Los Angeles, California 90024. All such persons listed below are
citizens of the United States except Mr. Syriani, who is a citizen of Lebanon;
Dr. Segovia, who is a citizen of Colombia; and Mr. Feick, who is a citizen of
Canada. Unless otherwise indicated, each occupation set forth opposite an
individual's name refers to employment with Occidental. Directors of Occidental
are identified by an asterisk (*).

Name and Business Address             Present Principal Occupation or Employment
-------------------------             ------------------------------------------

Ray R. Irani*                         Chairman of the Board and Chief Executive
                                      Officer of Occidental

Dale R. Laurance*(3)                  President of Occidental; Chairman of the
                                      Board, President and Chief Executive
                                      Officer of OOGHC

Ronald W. Burkle*                     Managing Partner and majority owner of The
9130 West Sunset Boulevard            Yucaipa Companies
Los Angeles, California 90069


                               Page 9 of 18 Pages



Name and Business Address             Present Principal Occupation or Employment
-------------------------             ------------------------------------------

John S. Chalsty*                      Senior Advisor, Credit Suisse First Boston
11 Madison Avenue
New York, New York 10010

Edward P. Djerejian*                  Director, James A. Baker III Institute for
Rice University, MS-40                Public Policy
6100 Main Street
Houston, Texas 77005-1892

R. Chad Dreier*                       President and Chief Executive Officer, The
24025 Park Sorrento, Suite 400        Ryland Group
Calabasas, California 91302

John E. Feick*                        President and Chief Executive Officer of
230, 319-2nd Avenue, SW               Matrix Solutions, Inc.
Calgary, Alberta, Canada T2P OC5

Irvin W. Maloney*                     Retired Chairman and Chief Executive
                                      Officer, Dataproducts Corporation

Rodolfo Segovia*                      Member of Executive Committee of
Carrera 9A No. 99-02 OF. 1001         Inversiones Sanford
Santafe de Bogota, D.C. Colombia

Aziz D. Syriani*                      President and Chief Operating Officer of
505 Park Avenue - 11th Floor          The Olayan Group
New York, New York 10022

Rosemary Tomich*                      Owner of the Hope Cattle Company and the
                                      A.S. Tomich Construction Company; Chairman
                                      of the Board of Directors and Chief
                                      Executive Officer, Livestock Clearing,
                                      Inc.

Walter L. Weisman*                    Past Chairman and Chief Executive Officer
P. O. Box 18017                       of American Medical International, Inc.
Beverly Hills, California 90209

Stephen I. Chazen                     Chief Financial Officer and Executive Vice
                                      President - Corporate Development of
                                      Occidental; Executive Vice President of
                                      Placid; Executive Vice President of OXY
                                      USA; Executive Vice President of OOGHC

Donald P. de Brier                    Executive Vice President, Secretary and
                                      General Counsel of Occidental


                               Page 10 of 18 Pages



Name and Business Address             Present Principal Occupation or Employment
-------------------------             ------------------------------------------

Richard W. Hallock                    Executive Vice President - Human Resources
                                      of Occidental

J. Roger Hirl                         Executive Vice President of Occidental
5005 LBJ Freeway
Dallas, Texas 75244

John W. Morgan (1)(2)                 Executive Vice President of Occidental;
                                      President of Placid; President of OXY USA;
                                      Executive Vice President - Worldwide
                                      Production of OOGHC

S. P. Dominick, Jr. (4)               Vice President and Controller of
                                      Occidental; President of OPIC

J. R. Havert (4)                      Vice President and Treasurer of
                                      Occidental; Vice President and Treasurer
                                      of Placid; Vice President and Treasurer of
                                      OXY USA; Vice President and Treasurer of
                                      OOGHC; Vice President and Treasurer of
                                      OPIC

Kenneth J. Huffman                    Vice President - Investor Relations of
                                      Occidental

Anthony R. Leach                      Vice President - Finance of Occidental

Robert M. McGee                       Vice President of Occidental

Lawrence P. Meriage                   Vice President - Communications and Public
                                      Affairs of Occidental; Executive Vice
                                      President - Communications and Public
                                      Affairs of OOGHC

Donald L. Moore                       Vice President and Chief Information
5 East Greenway Plaza                 Officer of Occidental
Houston, Texas 77046-0504

R. Casey Olson                        Vice President of Occidental; Executive
5 East Greenway Plaza                 Vice President of OXY USA; Executive Vice
Houston, Texas 77046-0504             President of OOGHC

Richard A. Swan                       Vice President - Health, Environment and
                                      Safety of Occidental

Aurmond A. Watkins, Jr.               Vice President - Tax of Occidental; Vice
                                      President of OXY USA


                               Page 11 of 18 Pages



Name and Business Address             Present Principal Occupation or Employment
-------------------------             ------------------------------------------

Jim A. Leonard (1)(2)(3)              Senior Assistant Controller of Occidental;
                                      Senior Vice President - Finance of Placid;
                                      Senior Vice President - Finance of OXY
                                      USA; Senior Vice President - Finance of
                                      OOGHC

Michael L. Preston (1)(2)(3)          Vice President and General Counsel of
                                      OOGHC; Vice President and General Counsel
                                      of Placid; Vice President and General
                                      Counsel of OXY USA

John M. Winterman                     Executive Vice President - Worldwide
5 East Greenway Plaza                 Exploration and Business Development of
Houston, Texas 77046-0504             OOGHC; Executive Vice President -
                                      Exploration of Placid; Executive Vice
                                      President - Worldwide Exploration of OXY
                                      USA

James S. Lyerly                       Executive Vice President - Business
                                      Development and Financial Planning &
                                      Analysis of OOGHC; Executive Vice
                                      President - Business Development and Legal
                                      of Placid; Senior Vice President -
                                      Business Development and Financial
                                      Planning & Analysis of OXY USA

Jo Ellen Drisko                       Vice President - Asset Management of OXY
2480 Fortune Drive, Suite 300         USA; Vice President - Asset Management of
Lexington, Kentucky 40509             Placid

Ben Langston                          Vice President - Business Development of
5 East Greenway Plaza                 OOGHC; Vice President - Business
Houston, Texas 77046-0504             Development of Placid; Vice President -
                                      Business Development of OXY USA

Patrick Oenbring                      Vice President, Permian Basin of OXY USA;
580 Westlake Park Boulevard           Vice President - Permian Basin of Placid
Houston, Texas 77079

Paul A. Parsons                       Vice President - Finance of Placid
580 Westlake Park Boulevard
Houston, Texas 77079

Linda S. Peterson (4)                 Assistant Secretary of Occidental; Vice
                                      President and Secretary of Placid; Vice
                                      President and Secretary of OXY USA; Vice
                                      President and Secretary of OOGHC; Vice
                                      President and Secretary of OPIC

Stephen J. Pettit                     Vice President, Legal and Assistant
580 Westlake Park Boulevard           Secretary of OXY USA; Vice President,
Houston, Texas 77079                  Legal and Assistant Secretary of Placid


                               Page 12 of 18 Pages



Name and Business Address             Present Principal Occupation or Employment
-------------------------             ------------------------------------------

Damir Vrcek                           Vice President of OXY USA; Vice President
5 East Greenway Plaza                 of Placid
Houston, Texas 77046-0504



-----------

(1)  Director of Placid
(2)  Director of OXY USA
(3)  Director of OOGHC
(4)  Director of OPIC


     During the last five years none of the Companies or the natural persons
named above (a) has been convicted in a criminal proceeding (excluding traffic
violations or similar misdemeanors) (b) was a party to a civil proceeding of a
judicial or administrative body of competent jurisdiction and as a result of
such proceeding was or is subject to a judgment, decree or final order enjoining
future violations of, or prohibiting or mandating activities subject to, federal
or state securities laws or finding any violation with respect to such laws.


ITEM 3.  SOURCE AND AMOUNT OF FUNDS OR OTHER CONSIDERATION.

     On January 29, 2003, pursuant to a commitment letter, dated November 25,
2002, between Occidental C.O.B. Partners, a Delaware general partnership ("Oxy
Partners") and Premcor Inc., Oxy Partners and Occidental Petroleum Corporation
("Occidental") purchased 1,025,427 shares and 274,573 shares, respectively, of
Premcor Common Stock for $19.20 per share, for an aggregate purchase price of
$19,688,198.40 and $5,271,801.60, respectively. The funds for the purchase by
Oxy Partners came from an inter-company loan from Occidental. The funds for the
purchase by Occidental and the loan to Oxy Partners came from working capital.

     On June 6, 2002, pursuant to a Warrant Exercise and Share Exchange
Agreement, dated as of April 26, 2002 (the "Exercise and Exchange Agreement"),
by and among Occidental, Oxy Partners, Blackstone Capital Partners III Merchant
Banking Fund L.P., a Delaware limited partnership, Blackstone Offshore Capital
Partners III L.P., a Delaware limited partnership, Blackstone Family Investment
Partnership III L.P., a Delaware limited partnership, Premcor and Sabine River
Holding Corp., a Delaware corporation ("Sabine") and a majority-owned subsidiary
of Premcor, Occidental exchanged 681,818 shares of the Common Stock of Sabine
for 1,363,636 shares of Premcor Common Stock.

     The remaining 6,371,010 shares of Premor Common Stock held by Occidental
and its affiliate, Oxy Partners, were acquired from Premcor in a series of
transactions beginning in 1995 prior to Premcor becoming a publicly traded
company.


                               Page 13 of 18 Pages



ITEM 4.  PURPOSE OF THE TRANSACTION.

     Directly and through Oxy Partners, Occidental currently holds its Premcor
Shares for investment purposes only with a view toward maximizing long-term
shareholder value for Occidental's shareholders and not for the purpose of
controlling Premcor.

     The purchase of additional shares in January 2003 was made to provide a
portion of the funds necessary for Premcor to acquire certain refining assets
from The Williams Companies. In addition, the purchase maintained Occidental's
and Oxy Partner's ownership percentages in Premcor at a level sufficient to
avoid a deemed change in Premcor's ownership that would limit Premcor's use of
its net operating losses.

     Other than as set forth in Item 6 of this Amendment 1 to Schedule 13D,
Occidental currently has no plans which relate to or would result in or any of
the actions listed in clauses (a) through (j) of Item 4 of Schedule 13D..
However, Occidental reviews and analyzes on a continuing basis its investments
in each of its subsidiaries and other operations, including the Premcor Shares,
in order to determine whether shareholder value for Occidental's shareholders is
better served by holding those investments, increasing or disposing of or
monetizing those investments or recapitalizing or otherwise restructuring those
investments. With respect to the Premcor Shares, these reviews and analyses are
based upon a variety of factors, including without limitation, the price of, and
other market conditions relating to, the Premcor Shares, the investment return
on the Premcor Shares, Premcor's business and prospects, other investment and
business opportunities available to Occidental, general stock market and
economic conditions, tax considerations and other factors deemed relevant.


ITEM 5.  INTEREST IN SECURITIES OF THE ISSUER.


                                                                          
(a)  Occidental:         aggregate number of shares held:                       9,034,646
     -----------         percentage of class:                                      12.31%

     Oxy Partners:       aggregate number of shares held:                       7,126,437
     -------------       percentage of class:                                       9.71%

     Placid:             aggregate number of shares held:                       7,126,437
     -------             percentage of class:                                       9.71%

     OXY USA:            aggregate number of shares held:                       7,126,437
     --------            percentage of class:                                       9.71%

     OOGHC:              aggregate number of shares held:                       7,126,437
     ------              percentage of class:                                       9.71%

     OPIC:               aggregate number of shares held:                       7,126,437
     -----               percentage of class:                                       9.71%



                               Page 14 of 18 Pages




                                                                          
(b)  Occidental:         sole power to vote or direct the vote:                 1,908,209
     -----------         shared power to vote or direct the vote:               7,126,437
                         sole power to dispose or direct the disposition:       1,908,209
                         shared power to dispose or direct the disposition:     7,126,437

     Oxy Partners:       sole power to vote or direct the vote:                         0
     -------------       shared power to vote or direct the vote:               7,126,437
                         sole power to dispose or direct the disposition:               0
                         shared power to dispose or direct the disposition:     7,126,437

     Placid:             sole power to vote or direct the vote:                         0
     -------             shared power to vote or direct the vote:               7,126,437
                         sole power to dispose or direct the disposition:               0
                         shared power to dispose or direct the disposition:     7,126,437

     OXY USA:            sole power to vote or direct the vote:                         0
     --------            shared power to vote or direct the vote:               7,126,437
                         sole power to dispose or direct the disposition:               0
                         shared power to dispose or direct the disposition:     7,126,437

     OOGHC:              sole power to vote or direct the vote:                         0
     ------              shared power to vote or direct the vote:               7,126,437
                         sole power to dispose or direct the disposition:               0
                         shared power to dispose or direct the disposition:     7,126,437

     OPIC:               sole power to vote or direct the vote:                         0
     -----               shared power to vote or direct the vote:               7,126,437
                         sole power to dispose or direct the disposition:               0
                         shared power to dispose or direct the disposition:     7,126,437


(c)  On January 29, 2003, pursuant to a commitment letter, dated November 25,
2002, between Occidental C.O.B. Partners, a Delaware general partnership ("Oxy
Partners") and Premcor Inc., Oxy Partners and Occidental Petroleum Corporation
("Occidental") purchased, in connection with Premcor's public offering of 12.5
million shares, 1,025,427 shares and 274,573 shares, respectively, of Premcor
Common Stock for $19.20 per share.


ITEM 6.  CONTRACTS, ARRANGEMENTS, UNDERSTANDINGS OR RELATIONSHIPS WITH RESPECT
TO SECURITIES OF THE ISSUER.

     Pursuant to the Second Amended and Restated Stockholders' Agreement, dated
as of November 3, 1997 (the "Amended Stockholders' Agreement"), between Oxy
Partners and Premcor, which by the terms of Exercise and Exchange Agreement
became applicable to the Premcor Shares acquired by Occidental upon Exchange of
its Sabine Shares, the Premcor Shares held by Occidental and its affiliates are
not transferable except in compliance with the Amended Stockholders' Agreement.
In addition, the Amended Stockholders' Agreement (i) provides that, so long as
Occidental and its affiliates own at least 10% of the fully diluted shares of
Premcor, Occidental has the right to designate one director for election to the
board, (ii) gives Premcor a


                               Page 15 of 18 Pages



right of first refusal to acquire the shares in the event Occidental receives an
offer from a third party to purchase the shares for cash or cash equivalents,
and (iii) grants registration rights to Occidental if Premcor is a public
company.

     Except for the Stockholders' Agreement, there are currently no other
effective contracts, arrangements, understandings or relationships (legal or
otherwise) among the persons named in Item 2 and between such person and any
other person with respect to any securities of Premcor.


ITEM 7.  MATERIAL TO BE FILED AS EXHIBITS.

     Exhibit 1      Agreement Pursuant to Rule 13d-1(k)

     Exhibit 2      Second Amended and Restated Stockholders' Agreement, dated
                    as of November 3, 1997, between Oxy Partners and Premcor,
                    Inc.*

     Exhibit 3      Form of Warrant Exercise and Share Exchange Agreement, dated
                    as of April 26, 2002 (the "Exercise and Exchange
                    Agreement"), by and among Occidental Oxy Partners,
                    Blackstone Capital Partners III Merchant Banking Fund L.P.,
                    a Delaware limited partnership, Blackstone Offshore Capital
                    Partners III L.P., a Delaware limited partnership,
                    Blackstone Family Investment Partnership III L.P., a
                    Delaware limited partnership, Premcor and Sabine*

     Exhibit 4      Commitment Letter, dated November 25, 2002


----------
*Previously filed.


                               Page 16 of 18 Pages



                                    SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify
that the information set forth in this statement is true, complete and correct.


February 5, 2003              OCCIDENTAL PETROLEUM CORPORATION


                              By: /s/ STEPHEN I. CHAZEN
                                 -----------------------------------------------
                                 Name:  Stephen I. Chazen
                                 Title: Chief Financial Officer and Executive
                                        Vice President - Corporate Development


                              OCCIDENTAL C.O.B. PARTNERS
                              by OXY USA Inc., its managing partner


                              By: /s/ STEPHEN I. CHAZEN
                                 -----------------------------------------------
                                 Name:  Stephen I. Chazen
                                 Title: Executive Vice President


                              PLACID OIL COMPANY


                              By: /s/ STEPHEN I. CHAZEN
                                 -----------------------------------------------
                                 Name:  Stephen I. Chazen
                                 Title: Executive Vice President


                              OXY USA INC.


                              By: /s/ STEPHEN I. CHAZEN
                                 -----------------------------------------------
                                 Name:  Stephen I. Chazen
                                 Title: Executive Vice President


                              OCCIDENTAL OIL AND GAS HOLDING CORPORATION


                              By: /s/ STEPHEN I. CHAZEN
                                 -----------------------------------------------
                                 Name:  Stephen I. Chazen
                                 Title: Executive Vice President


                               Page 17 of 18 Pages



                              OCCIDENTAL PETROLEUM INVESTMENT CO.


                              By: /s/ J. R. HAVERT
                                 -----------------------------------------------
                                 Name:  J. R. Havert
                                 Title: Vice President and Treasurer


                               Page 18 of 18 Pages