CHARACTERISTICS AND EXPLORATION POTENTIAL OF LACUSTRINE TURBIDITIC SANDSTONE IN LOWER CONGO BASIN OF WEST AFRICA

Substantial oil and gas have been discovered in the Tertiary submarine fan in the Lower Congo Basin. However, large lacustrine turbiditic sandstones have been discovered by oil exploration wells in the pre-salt Lower Cretaceous Djeno Formation of the Lower Congo-Congo Basin in the past few years. The lacustrine turbiditic complex is quite thick, ranging from 370 to 1289 meters. The Djeno Formation was deposited in a deep lake as ostracod assemblages and lithology demonstrate. It varies from lithic greywacke to feldspar lithic greywacke dominated by the former. Both grain size probability curve and C-M plot suggest that the Djeno lithic greywacke-feldspar lithic greywacke is a kind of gravity flow deposited in a deep-water lake. The deposition model of the Djeno lacustrine turbiditic sandstone is discribed in the paper. Both complete and incomplete Bouma Sequences are identified from the core data of the Upper Djeno. High quality reservoir sandstones are well developed in the A and B and C members of the Bouma Sequence. They are favorable targets and focuses in the future exploration and development.