Production and geologic implications of the Natih 9-C, 3-D seismic survey

Abstract

In the northern part of the Sultanate of Oman, oil is produced chiefly from carbonate reservoirs of Cretaceous age. Major fields such as Fahud and Natih (Figure 1) were discovered in the 1960s and rapidly brought on stream by Petroleum Development Oman (PDO). The oil-bearing reservoirs occur in the Natih and the Shu'aiba carbonate formations (Figure 2). The main reservoir in both fields is the Natih Formation. Natih Field was brought on stream in 1967 and, like Fahud Field, production was initially by a depletion drive. As a result of falling reservoir pressure, water injection was installed and this was later supplemented by gas injection. When the petroleum engineers of PDO recognized the importance of fractures to development of these fields, the developments were changed to gas/oil gravity drainage (GOGD). The full-field GOGD involves lowering the fracture oil rim by 70 m through crestal gas injection and down-dip water production.