SEISMIC STRATIGRAPHIC FEATURES AND RECOGNITION OF THE PERMIAN IN THE SOUTH YELLOW SEA BASIN

Only four wells have been drilled up to the Permian so far in the South Yellow Sea Basin, and the understanding is diverse concerning its stratigraphic features in the huge area without wells, e.g. the Laoshan Uplift. This article is supposed to be a starting point from lithology and land-sea correlation to drilled strata of the Permian for further study of seismic wave groups and velocity characteristics of its internal, Upper and Lower Permian strata in the South Yellow Sea Basin. Studies suggest that:the Permian is divided into upper and lower groups. The upper group includes the Dalong and Longtan Formations and is a coal-bearing clastic deposit. The coal seams are thin and distributed unstably, showing characteristics of phase transition, so the strata's regularity is deteriorated in seismic reflections. The seismic is slight continuous with middle-high frequency and low interval velocity; the lower section is the Qixia Formation containing limestone intercalating shale. The seismic is slightly continuous with middle-low frequency and high interval velocity. In the area in absence of wells, the Permian may be identified with the strong reflections of strata interface polarity of "2-negative and 1-positive" characteristics. The Lower Permian, Middle and Upper Carboniferous show similar seismic patterns, which consist of 4-5 seismic events, with rather stable thickness (about 200ms time thickness), and seismic wave polarity in "up-positive and down-negative" interface reflection characteristics. It can be used as the standard for regional correlation.