Abstract: Es3 2+3 complex reservoir in Liuzan Oilfield of Nanpu Sag has been under rolling exploration and development for more than 20 years. However, the output of development of the reservoir has not increased for many years according to preliminary evaluation. Analysis shows that the main causes of low-efficiency development are the fractured structures and the complicated relationship between oil and water. New second-time 3d seismic exploration techniques and new geological theories of sequence stratigraphy, i.e., new technical methods of strata research were applied during the Tenth Five-Year Plan period, which led to some new understandings on reservoir geology. Firstly, dramatic change of thickness near oil layers was caused by the local unconformity of basin-margin fault. Secondly, there were no so many breakpoints as mentioned in interpretation of the first-time poor-quality 3d seismic data. It was shown that Es3 2+3 reservoir was a complete fault nose and bulk anticline. Electrical characteristics and distribution law of oil-water layers of the reservoir were recognized as well. Alot of leakage oil-water layers were newly discovered. New geological understandings lead to remarkable change of reserves and output. During the Tenth Five-Year Plan period, more than 22 million tons of reserves were discovered in Es3 2+3 reservoir. The reservoir was finely described and waterflooding development was conducted on mini-layer series with scientific approaches. Annual oil output of the reservoir increased by 2.7 times than before. Some old oilfields turned into main reservoirs for increasing oil reserves and output in the area.

Key words: Nanpu Sag, Liuzan Oilfield, complex reservoir, correlation technique of sequence strata, deepening reservoir geology study, fine development; reserve and output increment