The vertical structure of the crustal block of the Songliao Basin can
be divided into upper, middle and low Earth's crust according to densi
ty. There is an about 3-km-thick low density interval between the uppe
r crust and the middle crust. This interval may be a magma chamber acc
umulated in crust by ''fluid phase'' which is precipitated and separat
ed from upper mantle meltmass. The abiogenetic natural gas, other gase
ous mass and hydrothermal fluids are provided to the Songliao rifted b
asin through crustal faults and natural earthquakes. This is a basic c
ondition to form an abiogenetic gas reservoir in the Songliao Basin. O
n both flanks of the upper crust (or named basin basement) fault there
are structural traps in and above the basement and unconformity surfa
ce or lateral extended sand, which contains communicated pores, as mig
ration pathway and natural gas reservoir; up to gas reservoirs there i
s shale as enclosed cap rock, and the suitable arrangement of these co
nditions is the basic features of abiogenetic gas reservoir.