SEREPT, Société de Recherches et d'Exploitation des Pétroles en Tunisie, Tunisian Company for Oil Research and Exploitation

Ashtart

SEREPT is operating the offshore oil field named Ashtart, located at 34° 22’N, 11°53’ E in the Gulf of Gabès offshore TUNISIA. The water depth is approximately 66 meters LAT.

Ashtart field was discovered in 1971, and has been in operation since 1974. The field was originally developed by Elf-Aquitaine Oil Company.
The Ashtart field consists of a single reservoir about 70 meters in thickness. The reservoir is heavily faulted; hence the production wells are practically non-interacting. The hydrocarbons are under-saturated, with downhole pressures in the range of 200 bars (eastern part of the reservoir) to 250 bars (western part of the reservoir), and temperatures of 140ºC. Most of the wells are at a substantial depth of ~3000 meters, and the Tubing Head Pressures (THP) are consequently low at ranging from 8 -10 bars.

Oil production is water-driven. The field is circled by water injection wells, using seawater.
The Ashtart field production recovery mechanism has been continually developed since operation commenced in 1974.

► The following major developments were implemented:

   • Water injection was introduced in 1976;
   • Gas lift was tested in 1982, and fully installed and completed during the DCA project in 1988;
   • ESP pumps were installed in two wells for testing in 2005.

The Ashtart field was initially designed for a production level of 60,000 BFPD and extended to 100,000 BFPD (60,000 BOPD). The current production is of the order of 60,000 BFPD and 12,000 BOPD. Very little gas is produced (190,000 Sm3/day), most of it is used as fuel gas, gas of gas lift and the remainder is flared. GOR is usually in the range 80-90 Sm3/m3. Water cut average is 70-80 % for the majority of the wells, however, in some wells the water cut is 30 %. .

► The field production facilities consist of 5 platforms.
Most of the wells are gas-lifted with a wide range in specific gas liquid ratio.