SIZE DISTRIBUTION AND CONTROL ON BITUMEN SATURATION OF SOME TAR SAND DEPOSITS IN PARTS OF SOUTH-WESTERN NIGERIA

Sedimentological analysis of some Afowo oil sands was carried out with the aim of characterising the reservoirs vis-à-vis their bitumen saturation and recovery efficiencies. Fourty-four samples of tar sands of the Afowo formation (collected at three different localities namely; Idiobilayo, Idiopopo and Igbotako) were subjected to granulometric and petrological analyses to determine the particle size distribution as well as other textural characteristics. The bitumen saturation analysis was carried out with the use of toluene. The result of sedimentological and particle size distribution studies showed that the sands are medium grained, moderately sorted and mesokurtic. The grain morphology can be described as having low to high sphericity, with shapes generally sub-angular to subrounded indicating a fairly long period of transportation. The result of bitumen saturation analysis showed that both Idiobilayo and Idiopopo oil sands have an average oil saturation of 17.2% and 16.9% respectively, while Igbotako sands have an average oil saturation of 12.3%. Consequently, Idiobilayo and Idiopopo oil sands deposits are therefore expected to have better reservoir quantities and possibly good oil recovery efficiencies.