Distribution of petroleum enriched areas, Changling Sag, Southern Songliao Basin

Changling Sag of the southern Songliao Basin is a terrestrial hydrocarbon-rich depression, and according to the “sag-wide oil-bearing theory”, oil and gas can be found in its whole effective source rock area. But prolific oil and gas areas that are usually called “sweet spots” are still controlled by several main factors in distribution. Fault belts above low uplifts and basement faults not only are the pathways allowing for hydrocarbon migration, but can form the lateral barriers of reservoirs, they are the main boundaries of oil and gas enriched areas. On the other hand, the fracture zone developed in the vicinity of the faults has improved the reservoir connectivity and increased the chances to obtain high production. These make the fault-developed zone itself become a “sweet spots” belt rich in oil and gas that should be paid more attention in exploration.