Accumulation condition and model of buried hill in the central uplift, Songliao Basin, China

The Central Uplift in the Songliao Basin is a large consequent buried-hill structural belt between the east and west faulted zones. Some hydrocarbon-rich sags (e.g. Xujiaweizi and Changling), occur at both sides of the uplifted zone. The Central Uplift, which indicates richness in hydrocarbon resources, is a long-term hydrocarbon migration destination with favorable conditions for hydrocarbon accumulation. Drilling two risk-taking exploratory wells, LT2 and LP1, have been demonstrated by the recent breakthrough in hydrocarbon discoveries. In conformity with uplift-sag contacts and migration pathways, the researchers establish six accumulation models, namely dual consequent faults, dual antithetic faults, consequent-antithetic faults, consequent fault-consequent overlap, antithetic fault-consequent overlap, and dual consequent overlaps, and five carrier systems which include the fault-fracture network, sandy conglomerate-fault-fracture network, fault-unconformity-fracture network, sandy conglomerate-unconformity-fracture network, and sandy conglomerate-fault-fracture network-unconformity. The team divides the Central Uplift accumulation process into four stages, including fold basement denudation and leveling off, coupled weathering, and leaching in the faulted and uplifted zones, hydrocarbon accumulation with sealed overburden, and sustained hydrocarbon preservation in the Central Uplift. Based on an analogous study of hydrocarbon accumulation in the Central Uplift, they conclude that the salients between hydrocarbon-rich sags occurring in the fault subsidence period are similar in accumulation conditions to the Central Uplift. The buried hills and their internal configuration at the salients should be the focus of exploration since they are the strategic successors of hydrocarbon exploration in the Songliao Basin due to their excellent exploration potential.