Application of Superheated Water Extraction in Geochemical Evaluation of Source Rocks

Application of superheated water was investigated for the extraction of organic compounds of petroleum exploration importance. Using Niger Delta samples as a case study, the geochemical ratios and parameters were calculated from n-alkane and isoprenoid hydrocarbon data. The pristane/phytane, pristane/nC(17), Ph/nC(18) ratios and carbon preference index (CPI) ranged from 0.90 to 1.29, 0.61 to 2.30, 0.86 to 1.44, and 0.88 to 1.88 for the western Niger Delta samples, respectively, and from 0.35 to 3.49, 1.01 to 3.03, 0.87 to 1.98, and 1.00 to 2.15 for the eastern Niger Delta samples, respectively. The geochemical plots revealed that a preponderance of the samples from both western and eastern Niger Delta had mixed organic matter input and a good number of the samples also had contributions from terrestrial organic matter, while few samples had strong contributions from marine organic matter. The plots also indicated that the samples were sourced by organic matter deposited in more reducing environments than oxidizing environments. There was no significant difference in geochemical characteristics between western Niger Delta samples and eastern Niger Delta samples. Biomarker data also confirmed that the samples are mainly of terrestrial and mixed organic matter origin. The results of this study agreed with the results of previous studies based on Soxhlet extraction sample preparation. The results obtained from Soxhlet extraction of the same set of samples were comparable to those of superheated water extraction. The study showed that superheated water extraction provides a better alternative to Soxhlet extraction as the sample preparation procedure ill geochemical evaluation of petroleum source rocks because of its environmentally friendly nature.