The Control Function of Synsedimentary Faulting on the Tertiary Stratum in Liaozhong Depression, East China
Liaozhong Depression is principal exploration and production formation in Bohai Bay. Lots of structural traps have been found in recent years. The effective prediction of subtle traps has become an urgent issue in hydrocarbon exploration and development. Numerous drilling results indicate that single geophysical characteristics can not identify effectively sand content in the depositional systems. In this paper based on the theories of sequence stratigraphy, sedimentology and tectonic geology, we try to predict sand body enrichment trends by combination of basin tectonism especially synsedimentary faulting activities during basin filling and reforming, which then was used to provide the most favorable references to subtle reservoir exploration.
In this study we employ the latest sequence stratigraphy theory to divide the Tertiary formation into ten third-order sequences. According to the high-resolution seismic data and well logs in Dongying Formation, we divide it into six fouth-order sequences through sub-regression interface boundary and establish high-resolution sequence stratigraphic division scheme. It is the key for the stratigraphic framework precision improvement and theoretical significance to identify sand body enrichment systems. Through comprehensive analysis by combination of well logs, core data and seismic facies, we characterize the fan delta, meandering-braided river delta and turbidite fan in isochronal sequence stratigraphic framework. By the characteristics of synsedimentary faulting distribution and its activities, basin tectonic subsidence and evolution processes, there is obvious control on the provenance, water drainage system and accommodation space, it also affects the positions and patterns of depositional systems filling and reforming. The analysis results show that gentle slope fault adjusting belt, slope break zones, reverse fault combination belt are under control of synsedimentary activities. All of these are favorable sand body enrichment positions and subtle reservoirs.
At last, based on the comprehensive analysis, we find that the fault adjustment belt and reverse fault zone are the favorable target zones. we demonstrate the possibility of using the results of synsedimentary faulting features to foster an understanding of its control on the development and distribution of depositional systems. It leads us a new understanding of making deep decisions of hydrocarbon exploration and development.
AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013