Sequence-stratigraphic Framework on Paleogene of the Liaohe Western Depression

With the development in depth of the oil and gas exploration, the exploration of the Liaohe western depression becomes more and more difficult, and serves as a complex challenge in view of petroleum geology.In order to undertake the fine and three-dimensional exploration of the oil and gas in the western depression and to increase the success rate of exploration, it is necessary to learn the successful exploration experience from Jidong oilfield, Jilin oilfield and Shengli oilfield, and to carry out detailed exploration of oil and gas in the western depression.The establishment of a sequence-stratigraphic framework is essential for the fine exploration of the oil, and of great theoretical and practical significance.Guided with the theory of sequence stratigraphy and based on well drilling, well logging, seismic and palaeophyte data in the interested districts, the paleogene can be divided into 4 second-order sequences and 11 third-order sequences on the basis of the identification of the sequence boundary which is made through unconformity surface recognition in the seismic section, isochronal formation comparison of the palaeontology fossil and mutation surface recognition of the well logging curves.According to the sequence boundary and the division of layer cells, and by using the synthetic seismogram, the sequence-stratigraphic framework of the west depression is established.Sedimentary sequence distribution law in the sequence-stratigraphic framework includes 5 aspects:migrated southward depocenter;thin slope sedimentary;large sedimentary thickness in the south and small sedimentary thickness in the north, a complete formation in the low-lying;and a not completed formation in the heave part.