Graphic correlation: A powerful tool for biostratigraphic correlation of petroleum exploration and production in the Cenozoic deep offshore Niger Delta, Nigeria

The graphic correlation method provides better and higher resolution to the stratigraphic problems than zonation biostratigraphy. The measured total stratigraphic ranges of 44 palynomorphs present in five wells from the Niger Delta Basin have been assembled by graphic correlation method into a chronostratigraphic framework. The analysis by graphic correlation reveals that for a meter of sediment accumulation in Well E, correspondingly amounted to only 0.8794 m, 0.7586 m, 0.8677 m and 0.8686 m of sediments that were deposited in wells A, B, C and D, respectively. These relative rates of sediment accumulation indicate that either there was less erosion taking place and/or more accommodation space in Well E than Wells A, B, C and D. A graphic correlation horizontal terrace was recorded in each of the Wells A, C and D, which are interpreted as condensation of sediments that had truncated the sediments accumulation profile in these wells. These condensed sections are interpreted as sediment starvation and very slow rates of sedimentation during the Early Pliocene, Late Pliocene and Late Pleistocene due to marine transgression(s) at these stages in the Niger Delta Basin. The generated correlation equations, slopes and intercept values from graphic correlation plots allow the correlation of six biostratigraphic and sedimentological events in Wells A, B, C, D and E. The resulting chronostratigraphic framework in this study is essential for sequence stratigraphic interpretations and basin analysis, and in particular, to correlate widely separated wells.