Songo Songo Gas Fields

The field is located on and offshore Songo Songo Island (Figure 7), about 15 km from the mainland and 200 km south of Dar es Salaam.The discovery well, Songo Songo-1, was drilled in l974 by AGIP. Songo Songo is a large N-S trending structure containing one to two TCF of gas reserves. The gas is contained in Lower Cretaceous inner shelf sand reservoirs with porosities averaging greater than 20%, and net porous intervals up to 155 m thick. The structure was uplifted during the Early Cretaceous and the reservoir modified by the Mid Cretaceous regional unconformity. The trap consists of two faulted highs separated by a saddle. A series of N-S and NW-SE trending faults step down to the east. This faulting, regional eastward tilting, and rapid Tertiary sedimentation created more growth faults which mostly sole out in the sealing shales of the Upper Cretaceous Ruaruke Formation. The Lower Cretaceous reservoirs are not affected by this later episode of faulting. Continued activity along these faults resulted in the development of broad, low relief anticlines. The gas appears to have been sourced from post mature organic material of Jurassic or Early Cretaceous age. The associated liquids are probably sourced from mature organic matter of Early Cretaceous and Middle Cretaceous age and seem to have migrated from a nearby basin.