Except KBR's contract was awarded competitively:
The LOGCAP contract, which is re-competed periodically, had been competitively awarded by the United States Materiel Command to Kellogg, Brown, & Root (KBR) in December 2001.
http://www.house.gov/reform/min/pdfs/pdf_inves/pdf_admin_halliburton_contract_army_may_2_let.pdf