Abstract:

Based on the relationship between sedimentary sequences and reservoir formation，the author puts for-ward a new approach to exploration of lithologic-stratigraphic reservoirs in the fluvial-delta sedimentary systems-“to look for intervals with low net-to-gross ratio outside a facies zone with high net-to-gross ratio，and to look for reservoirs with relatively high net-to-gross ratio within intervals with low net-to-gross ratio”.In combination with sequence stratigraphic theories and relevant target-evaluation techniques，this new approach is used to identify reservoirs in the1stmember of the Triassic Karamay Formation in the HongˉChefaultbelt in JunggarBasin. It is believed that the middle cycle-MSC2is the favorable“low net-to-gross ratio interval”，in which the channel sands with high curvature index are the favorable“exploration targets with relatively high net-to-gross ratio”.The exploration well（Hongshan-4）targeting at these channel sands was drilled and flowed commercial oil. Mean while，for the delta deposits in the Neogene Shawan Formation，it is believed that the transgressive system tracts in the third-order sequence-NSQ2-are the favorable“low net-to-gross ratio interval”，in which the underwater distributary channel sands at delta front are considered to be the“exploration targets with relatively high net-to-gross ratio”.The exploration well（Che-89）targeting at these sand stones was drilled and obtained discoveries. This indicates that，intervals with low net-to-gross ratio also can have well-developed lithologic-stratigraphic reservoirs. This new approach is of significance to exploration of lithologic-stratigraphic reservoirs in the terrestrial strata in China.

Key words: river, delta, sequence stratigraphy, lithologic-stratigraphic reservoir, Hong-Che fault belt, Junggar Basin