Abstract: In recent years, China has gained major breakthroughs in deep and ultra deep field drilling where deep oil and gas exploration is becoming increasingly important. The deep exploration in the Junggar Basin is at a preliminary stage and systematic study of formation conditions for deep oil and gas is much needed. Here, based on previous investigations and combined with new drilling data, we have analyzed the key geological conditions for hydrocarbon generation, reservoir formation and accumulation to reach the following conclusions: (1) The deep strata contains several hydrocarbon source rocks of average to high maturity. The hydrocarbon generation processes are complex and were affected by external environments such as multistage tectonic movements and abnormal high pressure. Nevertheless the source rocks have high hydrocarbon potential to provide abundant oil and gas. (2) High quality reservoirs occur even under deep buried condition, helped by fracture-making, weathering-leaching, corrosion of organic acids produced by hydrocarbon generation and early hydrocarbon filling, and abnormal pressure. (3) Oil and gas formation is controlled by hydrocarbon generation and reservoir formation, characterized by multi-period oil and gas filling; enrichment types depend on source rock types and burial depth. (4) Favorable reservoir-formation conditions in the Junggar Basin—including deep structures and stratigraphic and lithologic targets in the inner and slope areas of hydrocarbon rich sag, and Permian strata with tight oil and gas resources in deep basin and Jurassic coal-measures strata with tight sandstone gas in the central part of the basin—make it a promising target for deep oil and gas exploration.

Key words: Junggar Basin, deep oil and gas, hydrocarbon accumulation condition, source rock, effective reservoir, exploration potential