STUDY OF SEQUENCE STRATIGRAPHY AND SUBTLE RESERVOIRS IN THE BIYANG SAG OF THE NANXIANG BASIN

Based on T-R cycle theory,combined with seismic profile reflection characteristics and sequence stratigraphic analysis as well as local well profile sequence stratigraphic analysis,it is discussed in this paper the 3-grade sequence stratigraphic frameworks in the Lower Tertiary,the Biyang Sag,the Nanxiang Basin.The Hetaoyuan and Liaozhuang Formations of the Lower Tertiary in the Biyang Sag are divided into 1 Ⅰ-grade T-R cycle and 4 Ⅱ-grade T-R cycles.The Hetaoyuan Formation is subdivided into 9 Ⅲ-grade T-R cycles.Sedimentary system and sedimentary sequence patterns in T-R cycles in the Biyang Sag are analyzed.Studies of the distribution pattern of subtle reservoirs in the Biyang Sag indicate that,subtle reservoirs are zoned controlled by geologic structure and sedimentary characteristics.Taking into consideration of oil generation,accumulation and overlying formation in the region,the favorable exploration targets in the sag are predicted.