The Role of the Aogula Fault in the Migration of Hydrocarbon Along the Sartu, Putaohua, and Gaotaizi Reservoirs and Its Relationship with Accumulation in the Songliao Basin

To elucidate hydrocarbon enrichment characteristics within the Sartu (S), Putaohua (P), and Gaotaizi (G) reservoirs near the Aogula Fault in the northern Songliao Basin, this study systematically analyzes the fault’s influence on hydrocarbon migration and accumulation, based on an investigation of migration pathways along fault zones and sandstone bodies. The results demonstrate that, except at its northern terminus, the Aogula Fault terminates hydrocarbon migration within the S reservoir sandstones, thereby promoting hydrocarbon accumulation near the fault zone. This is a primary reason for the prevalence of productive drilling targets in this region. Six vertical diversion zones are identified along the fault trace, uniformly spaced from southwest to northeast. These zones facilitate vertical migration of hydrocarbons from the G and P reservoirs into the overlying S reservoir, accounting for the significantly greater hydrocarbon enrichment observed in the S reservoir compared to the underlying formations. Furthermore, excluding the eastern and western extremities, lateral diversion zones characterize the remainder of the fault. These zones enhance lateral hydrocarbon migration from the southwestern segment towards the northeastern segment, resulting in significantly higher accumulation in the northeastern section relative to the southwestern section.