Among all the structural traps discovered in the north of the Songliao Basin

anticline structures occupy 16.5%

faulted-noze structures 61.9%

faulted-block structures 21.6%. The explored hydrocarbon reserve at present is mainly distributed in the anticline structures. Based on data of seismic exploration

hydrocarbon detection

geochemical exploration anomaly and well-test result

the authors divided the traps of different sequences into three types and four grades so as to increase the rate of success.