Abstract:

YaojiaNenjiang Formation in Songliao Basin is an integrated set of deposit stratum cycle with base level rising and falling. The oil shale distributed steadily in the whole basin were formed during the maximum flooding surface period at the bottom of K2n2. The oil shale is not only the standard interface of sequence and stratigraphic correlation, but also the important source rock and cap rock. Sediments of K2y and K2n1 are largescale lacustrine and retrograded delta deposition formed in the lacustrine transgressive period. Sediments from K2n2 to K2n5 are largescale lacustrine and progradation delta deposition formed in the forced lacustrine regressive period. Largescale turbidite channel and tail turbidite fan were developed in the long axis direction of the material source during the progressive lacustrine period of K2n1. Largescale slump fan deposition were developed on the top of the progradation delta during the forced lacustrine regressive period of K2n2. The reservoir layer is a complex largescale delta formed during the transgressive and regressive period, which has the characteristic of the sandbody in distributary channel, mouth bar and sheet sand. The sandbodies extended to the lacustrine center and went into the mudstone and mature source rock, thus formed a good sourcereserviorcap relationship. The favorable places for oil pools are mainly developed in the largescale complex delta in the long axis direction of the material source. It is an important geological condition for mega petroliferous basin with continental facies. The gravity current channel and slump fan are also good conditions for forming the lithological pool, which are very important exploration fields.

Key words: YaojiaNenjiang Formation (K2y, K2n), depositional evolution, oil and gas distribution, Songliao Basin