Application of seismic sedimentology in reservoir prediction in fluvial to shallow water delta facies: A case study in Guantao Formation from the Penglai A structure area in Bohai Bay

Abstract

The Penglai A structure area in the Miaoxinan uplift had good drilling show of oil and gas in the Guantao formation, but reservoir sands with the thickness less than 5 meters could not be resolved and interpreted precisely.Recognition that the source direction in the sedimentary period of Guantao formation is northeast, fluvial to shallow water delta facies were developed which was made by comprehensive utilization of drilling cores, the data of sporopollen and algae, logging and 3-D seismic data.90°phasing adjusted seismic wavelet phase to -90°to tie seismic events to lithology.Frequency division was used to interpret, treat and judge phase axis following relative geologic time surfaces to establish high-frequency, sequence stratigraphic framework and optimized 60 Hz dominant frequency seismic data for stratal slicing.Stratal slicing made from the 3-D seismic volume revealed better facies information on the relative geologic time surfaces.With the interpretation of sand body depositional features displayed on each sequence stratal slice, it could be found that sedimentary evolution process in the study area was divided into four stages: fluvial facies stage, sheet-like shallow water delta stage, lobate shallow water delta stage and distributary channel shallow water delta stage.And it also could be found that the sand body mainly developed horizontally in the north of the study area, and the position of fluvial channels and shallow water delta front provided good areas for oil and gas exploration.This study case proved that the method of seismic sedimentology is suitable for thin sandstone reservoir prediction in Bohai basin.

Keywords

• seismic sedimentology
• bohai basin
• fluvial to shallow water delta facies
• reservoir prediction
• guantao formation