Filed by Unocal Corporation Pursuant to Rule 425 under the Securities Act of 1933 Subject Company: Pure Resources, Inc. Commission File No. 001-15899 The following slides were presented during Unocal's Q3 2002 Earnings Conference Call on Thursday, October 24, 2002: UNOCAL ADJUSTED EARNINGS -------------------------------------------------- $ MILLION $ PER SHARE --------- ----------- Third Quarter 2002 126 .52 Second Quarter 2002 134 .55 Decrease 8 .03 -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- Factors: Lower non E&P results (16) (.07) Lower N. American gas prices (9) (.04) $2.74 vs. $2.97 Lower production volumes (7) (.03) 466 MBOE/D vs. 486 MBOE/D Lower effective International Income tax rate 15.06 Higher Worldwide oil/liquids prices 12.05 $24.19 vs. $22.63 Other (1) -- UNOCAL E&P LOWER 48 RESULTS 3Q 2002 vs. 2Q 2002 -------------------------------------------------- $ MILLION --------- Lower earnings 19 -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- Lower natural gas prices (6) $2.97 vs. $3.12 Lower production volumes (6) Higher dry hole expense (8) Pure Put & transaction costs (8) Lower operating/exploration/D & D costs 8 Higher oil & liquids prices 4 $24.74 vs. $23.47 Other factors (3) UNOCAL E&P ALASKA RESULTS 3Q 2002 VS. 2Q 2002 -------------------------------------------------- $ MILLION --------- Higher results 15 -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- Timing of impairment in 2Q 12 Higher oil & liquids prices 2 $22.17 vs. $20.86 Lower operating expense 2 Higher Dry Holes (1) UNOCAL E&P CANADA RESULTS 3Q 2002 VS. 2Q 2002 $ MILLION --------- Higher results 1 --------------------------------------------------------------------------- --------------------------------------------------------------------------- Lower Dry Holes & Operating Expense 3 Higher oil & liquids prices 1 $22.70 vs. $21.92 Lower natural gas prices (3) $2.08 vs. $3.03 UNOCAL E&P INTERNATIONAL RESULTS 3Q 2002 VS. 2Q 2002 $ MILLION --------- Higher earnings 11 --------------------------------------------------------------------------- --------------------------------------------------------------------------- Lower effective income tax rate 15 37% vs. 43% Higher liquids prices 5 $24.80 vs. $22.84 Higher natural gas prices 2 $2.69 vs. $2.64 Timing of liftings 5 Higher dry hole expense (5) Higher operating expense (5) Higher Thailand D&D (5) UNOCAL NON E&P BUSINESS RESULTS 2Q 2002 VS. 1Q 2002 -------------------------------------------------- $ MILLION --------- Lower earnings 17 -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- Geothermal & power (9) Lower generation & Foreign Exchange Midstream (6) Timing of pipeline accruals Lower oil & gas marketing margins (2)