| الوصف: |
The oil shale potentials of carbonaceous shales in the Tertiary Ogwashi – Asaba Formation, Anambra basin (SE Nigeria) have been evaluated in this study. Samples were collected from three localities of Azagba Ogwashi (AZ), Oba (OB) and Ihioma (IH), where the Ogwashi Asaba Formation lithostratigraphic units are well exposed. Fieldwork studies reveal that the general lithologies in the studied localities consist of cyclic successions of lignite, carbonaceous shales, silty shales, mudstones, siltstones and sandstones, interpreted as deltaic deposits. Laboratory analyses include total organic carbon (TOC) determination and Rock – Eval pyrolysis studies of collected samples. TOC results indicate average values for AZ, OB and IH samples, to be respectively 12. 10wt.%, 5.01wt.% and 8.16wt.%. Rock – Eval pyrolysis studies include, Tmax, S2 and S2/TOC, calculated for Hydrogen Index (HI). Tmax average for AZ, OB and IH are 427°C, 418°C and 420°C respectively. Average S2 yields for AZ, OB and IH are respectively 24.42mgHC/g rock, 4.13mgHC/g rock and 8.53mgHC/g rock. Graphs of S2 vs TOC and Tmax vs HI show that the AZ samples plot within the fields of prolific, primary source rock, with the capability of yielding mixed oil and gas. The OB and IH samples plot within the fields of good, secondary and very good, primary source rocks respectively, with the capabilities of yielding gas only. Based on the obtained results, it is concluded that only the carbonaceous shale from the Azagba Ogwashi study locality has the potential for oil shale. |