STUDY OF OIL MIGRATION AND INJECTION DIRECTIONS BY NITROGEN COMPOUNDS

Based on the composition and concentration changes of nitrogen compounds in the study oil samples as well as the maturity indexes of saturated and aromatic biomarkers,this paper investigated the oil migration and injection direction of Caofeidian and nearby areas in the offshore part of the Bohai Bay Basin.The results showed that the distribution and composition characteristics can indicate oil fractionation effects.With the increasing of oil migration effects,the concentration of nitrogen compounds decreased whereas the ratios of shielded nitrogen compounds to exposed or semi-shielded ones increased.The oil migration and injection direction of the Shaleitian Uplift was from east to west,with the main charging point in the east.Two oil migration and injection directions (i.e.,eastnorth and southwest) were found in the Shadongnan tectonic zone.Oil in the Shijiutuo Uplift and the inclined end migrated from northwest.This is consistent with oil migration directions deduced from the gradient changes of hydrocarbon biomarkers.All these conclusions are also accorded with the regional oil occurrences and exploration facts.