A Sequence Stratigraphy Study Of The Region Shen 84-An 12

The Region Shen 84-An 12 have complex geologic condition with growing faults and now in the intermediary and later stage of high water holdup. based on the data of drilling coring, well logging, seismic and develop of production and exploration, we make a approach to the matching of sequence for this region, by applying the theory of the high-resolution sequence stratigraphy to the sequence analysis of the Region Shen 84-An 12 Sha 3 section. in the process of comparison,we adopt these methods: log and seismic combined, static comparison and dynamic verification combined, correlation of profile and fault-block comparison combined, and enhance the accuracy of the sequence and strata comparison. Finally, Sha 3 section is classified into 5 long-term base level cycles, and several middle time, and short time base-level cycles are also divided. According to the requirement of production and development, the short time base-level cycles are divided into 146 time-stratigraphy units, and the high-resolution sequence stratigraphic frame for the region is built. Based on change rule of different spots'A/S in base level cycles and research about deposition and reservoir, we receive the relation between the evolution of the sequence stratigraphy & deposition and reservoir's change in different base-level cycles, also we make s discussion about the relation between base-level cycle and surplus oil, and acquire some points below:At the early stage of base-level cycle ascension, the value of A/S is less than 1. in the region of interest, distributary channel microfacies developes and distributes concentratedly; and the distribution range of pre-fan delta mud microfacies is relatively less, and sand body grows comparatively, and the physical property of reservoir is satisfactory.At the middle period of base-level cycle ascension, the figure of A/S is 1 approximately. distributary channel distributes centrally, and the distribution range of distributary bar microfacies and pre-fan delta mud microfacies both broaden. sand body grows generally, the physical property of reservoir is moderate.At the last stage of base-level cycle ascension, the figure of A/S is larger than 1.the distribution range of distributary channel is relatively small, and distributary bar microfacies relatively develops, and the distribution range of pre-fan delta mud microfacies is the largest of all. sand body grows poorly, the physical property of reservoir is bad.The decline hemicycle of base-level cycle is contrary to its ascend half cycle, and the value of A/S is larger than 1 firstly, and then reaches 1 approximately, and at last is less than 1. The evolution of micro-precipitation facie, and the character of the change of reservoir and sand body is much similar.The distribution of the remaining oil in the reservoir is controlled by the base-level cycle. In the hydrocarbon bearing section, the inhomogeneity at the end of the long time base-level cycle descent and at the early stage of the long time base-level cycle ascension is poor, and is easy to developed, but the reserve volume is great, with the result that the remaining oil is enrichment; the inhomogeneity at the early stage of the long time base-level cycle descent and at the last stage of it's ascension is strong, and is hard to developed, but the reserve volume is small, with the result that the remaining oil is distribute dispersely.