Abstract
The Great Mabruk field is made up of four oil accumulations located in the Sirt Basin. West Mabruk, where the best reservoir characteristics were encountered, is the only one currently developed. The reservoir, located at a depth of 3500 feet, is made up of carbonates of Palaeocene age. The geological studies highlight steep variations of facies together with a complex compartmentalization, resulting in the definition of numerous rock types and more than ten oil water contact (OWC).
Owing to the small thickness (45’) and owing to permeability, the transmissibility is low and the performance of vertical wells is generally very poor.
Since the late fifties several companies have followed one another as operator but the real start-up of the field took place in 1995 with CPTL as operator. The development included a two-year “pilot” phase prior to finalizing the depletion scheme. To date almost 16 million stb have been recovered and the current rate is around 15000 bopd from 35 producers. Reservoir pressure is maintained by 23 water injectors.
Sophisticated techniques concerning drilling (multi-drains) and pumping (PCP, ESP) were pioneered to cope with the low productivity and the high heterogeneity. Reservoir simulation was initiated to predict the areas to be poorly swept. Fine simulation grids are used to represent geological features in a way that captures their impact on reservoir performance.