The Coalinga field is one of the oldest oil fields in California. The Temblor sands comprise the major reservoir at 500 to 2,000 ft, with 33% porosity and 12 to 14degrees API oil. Each Temblor sand is at a different stage of drainage and thermal maturity. Steam production represents the single largest operating expenditure, and managing this expense is critical to Coalinga's success. Starting in 2002, ChevronTexaco has followed an aggressive plan in Coalinga to manage and optimize steam injection by use of monitoring tools and maintenance and growth heat-calculation tools. Heat management is used to optimize thermal-recovery economic performance in Coalinga.