关键词: 尼日尔三角洲, 深水区, 泥底辟, 成藏模式, 汇烃面积

Abstract: Deep water areas on both sides of the Atlantic Ocean are ‘hotspots’ for oil and gas exploration, with most of the discovered large medium oil and gas fields in these areas being salt-related structures. In the Niger Delta Basin, there are no salt deposits – only mud diapirs, mud volcanoes and other mud-related structures. In this study, comprehensive geological analysis is applied to clarify the rules of hydrocarbon accumulation in the compressed deep water zone in the basin. The oil and gas accumulation model is determined on the basis of seismic, well drilling, logging, crude oil physical properties, and other data, beginning with the tectonic and sedimentary evolution of the deep water area of the Niger Delta Basin. It is concluded that the deep water area of the Niger Delta Basin has been in a deep to semi-deep marine sedimentary environment since the Late Cretaceous. The principal source rocks are marine source rocks, deposited from the Upper Cretaceous to the Paleocene, that entered the peak stage of hydrocarbon generation and expulsion in the Late Miocene. As the Niger Delta continued to prograde towards the sea, the Middle and Lower Miocene were dominated by lobe deposits, while the Upper Miocene was dominated by channel complex deposits. Faults and fractures are the main pathways for vertical migration of oil and gas. On this basis, a “tree-shaped” near-source hydrocarbon accumulation model for the deep-water area of the Niger Delta Basin is proposed, which indicates that the fetch area is the main controlling factor of hydrocarbon enrichment in the area. The mud diapir structural zone in the northern part of the deep-water area has good hydrocarbon accumulation conditions, with a large number of undrilled structural traps, offering promising exploration potential.