FORMATION AND DISTRIBUTION FEATURES OF THE ABIOGENIC GAS POOLS AND THEIR EXPLORATION STRATEGIES IN THE SONGLIAO BASIN

Abundant abiogentic gas pools were developed in Songliao Basin due to its unique deep lithosphere,crustal structure and regional structure background of rear arc strike-slip pull-apart basin.The abiogenic gas pools are mainly located around the NNE and NWW trend major faults in deep crust,where there is plenty of abiogenic natural gas supply because of intense volcanic activities.Abiogentic hydrocarbon gas pools are mainly located in low-oxygen-fugacity and hydrogen abundant zones in deep crust.Organic and abiogentic pools are mutually accelerated and effected.They share similar migration pathways and their accumulation belts are both located in strike-slip pull-apart related NNE slope breaks and horsts as well as central fault uplifts,strike-slip thrusting related uplifts between sags,big structures connected to NEE-EW nose uplifts,and structure-lithology-layer combined traps.Deep abiogentic hydatogenesis causes corrosion reservoir beds.In the meanwhile,the strong corrosion of CO₂ fluid helps the extraction of organic substance,generating oil and gas combined flow,and there's a good chance of the coexistence of organic and abiogentic hydrocarbon pools.Work for the next phase is to go on exploring the abiogentic gas and combined generated gas in deep fault depressions,and to find the abiogentic gas both in Mesozoic-Paleozoic carbonate sequences in the base of fault depression and in shallow fault depression with intense volcanic activities.