Field_DevelopmentConcerns over future output at Rokan field where Chevron prepares to hand over reinsState-owned Pertamina has yet to secure access to all EOR chemicals at giant oil and gas asset from outgoing operator ChevronMature asset: Chevron's Minas field, a main producing field at RokanPhoto: CALTEX PACIFIC INDONESIAAmanda BattersbySingapore