Recognition and Definition of Oscillating Base Level Subcycle: An Example from S Reservoir in Bozhong Depression, Bohai Bay Basin, East China

Fan, Tingen; Hu, Guangyi; Song, Laiming; Yu, Lianyong

When the S reservoir on the top of Guantao formation, Bozhong depression, Bohai Bay basin, East china, is studied, the formation developed during the stage of oscillating base level subcycle is firstly recognized. There are still 2 kinds of models on the S reservoir. One is a large-scale structural one. Another is that it is composed of the lower structural basal water reservoir and the upper lithologic reservoir. The reserve of the former is as twice as the latter. Aiming at solving the problem, S reservoir is restudied. Then the concept of oscillating subcycle is firstly put forward, and the S reservoir model is successfully reexplained with the concept. Then the base level cycle theory is discussed introducing the concept. The result shows that the present base level change including of ascending and descending can't fully characterize the total dynamic process of base level. The reasonable characterization on base level should include 3 courses, i.e. base level ascending, base level descending and base level keeping steady. And the base level can descend, incline to ascend, ascend and incline to descend during a total course. During the process of base level inclining to ascend and inclining to descend, the oscillating base level inclining to ascend and inclining to descend are accordingly formed, both of which comprise the so-called oscillating base level subcycle. It is debated that the concept of oscillating base level subcycle helps to build the isochronous framework of complex reservoirs and decrease the ambiguity of high resolution sequence stratigraphy.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013