Application of Sequence Stratigraphy to Improving Mature Oil Field Recovery

Key words: 
• base level /
• framework architecture /
• heterogeneities /
• OO IP, remaining oil /
• mature oilfield /

Abstract: Pucheng oil field is located in the Dongpu dep ress, Henan p rovince. Four scales of sequence cycles are distinguished in study area, including very short term cycle, short term one, medium term one and long term cycle. The heterogeneities study indicates that base level controlled sand distribution and the reservoir heterogeneities. In the rising semi-cycle of short cycle , the p roperty are better at the bottom of the sands and becoming poorer to top, while with a totally differentway in the falling semi-cycle. At the lower position of medium and long term cycles, braided channel are well developed with a widesp read area and good property, while at the high position of the cycles, the braided channel are small and the sand sp read area are limited with poor property. In the rising semi-cycle of long-and medium-cycles, the reservoir become poorer from bottom to top, while it becomes better in the falling semi-cycle.From the bank to lacustrine center, the braided channel becomes weaker and smaller, and the reservoir architecture turns to be mainly of sheet-like sands near the front ofmiddle fan from mainly of channel sands near the middle fan,and finally of lacustrine mud at the lake center. The distribution of OO IP (original oil in place) and the residual oil are also controlled by the baselevel framework. OO IP is high at the low baselevel p lace in the framework, and high while the baselevel is at the high p lace. Sandbody at the low baselevel p lace is alwayswith good p roperty and easy to be dip loid, so it is often p laced on the important p lace in the development, and with large output. Butwith high OO IP, its remaining amount is always in large quantities. Sandbody at the high baselevel is alwayswith poor p roperty and difficult to dep loid, and be put in the secondary place in the development, so its output is little. Butwith low OO IP, its ratio of remaining oil in the reservoir is not important.