Abstract:

After more than 30 years of exploration and development,the Biyang depression has been highly mature in exploration and development,with most of the fields entering the late stage of development with high water cut.Analysis of the geological conditions for the formation of subtle reservoirs indicates that they share the same source and happened in the same period with larger-scale reservoirs.Three methods for identifying subtle reservoirs are presented here based on the abundant dynamic and static data available.They are fine correlation of subzone,trap assessment,and micro-structure analysis.Proper use of these methods can effectively identify subtle light oil reservoirs in the matured areas in Nanxiang basin.The results show a success rate of identification over 90% and increamental geologic reserves of more than 5 million tons and annual crude production growth of more than 10000 tons.

Key words: subtle reservoir, identification technology, matured oilfield, Biyang Depression, Nanxiang Basin