The Sacha oil field was discovered in early 1969 about 112 mi (180 km) east-southeast of Quito, Ecuador. It lies in the present-day axial region of the sub-Andean basin which in Ecuador is filled with Upper Silurian to Holocene sediments.
Sacha field is on a low-relief, faulted anticline about 17.5 mi (28 km) long. At the principal reservoir there are approximately 41,000 acres (16,400 ha.) under a vertical closure of 200 ft (61 m).
Principal reservoirs are sandstones of the Lower Cretaceous Hollin formation and the middle to Upper Cretaceous Napp formation. The Hollin sands, the main reservoir, are marine-fluvial, whereas the Napo sandstones are largely continental deposits. The basal sandstone of the Upper Cretaceous-Paleocene Tena formation is a secondary reservoir.
Production from the field commenced in July 1972 and, at the end of September 1979, over 164,000,000 bbl of oil had been produced. Gross recoverable reserves in the field are estimated at 633,784,000 bbl. Through September 1979, 89 wells had been drilled in the field, two of which were dry holes.