supplementary information on oil and gas producing activities ( unaudited ) c o n t i n u e d summary of changes in standardized measure of discounted future net cash flows relating to proved oil and gas reserves ( in millions ) 2004 2003 2002 sales and transfers of oil and gas produced , net of production , transportation , and administrative costs $ ( 2715 ) $ ( 2487 ) $ ( 1983 ) net changes in prices and production , transportation and administrative costs related to future production 950 1178 2795 .