Cenozoic Tectonic Evolution of Liaodong Dome, Northeast Liaodong Bay, Bohai, Offshore China, Constraints From Seismic Stratigraphy, Vitrinite Reflectance and Apatite Fission Track Data
The Liaodong dome is a region of localized uplift and deformation within the Liaodong Bay, Bohai, offshore China, between two branches of the Tan-Lu fault zone (TLFZ). It is to the Liaozhong sag in the west and Liaodong sag in the east. This dome was indicated as a promising exploration area after several oil fields have been found since 1990s. However, compared to the other domes in the Liaodong Bay, like the Liaoxi dome, only a few highly productive oil and gas wells are located within the Liaodong dome. As we known, uplifting and erosion across domes would cause a decrease in the confining pressure on subsurface fluids, resulting in degassing of oil in reservoirs, expansion of free gas in reservoirs, and degassing of formation water. These are believed to be the result of this uplift-induced processes. However, the Cenozoic tectonic evolution of Liaodong dome remains poorly understood which restricts the oil and gas exploration in this region. A regional study of the Liaodong dome, involving 3-D seismic dataset, vitrinite reflectance(VR) and apatite fission track(AFT) data, has been undertaken in order to document the evolution of the Liaodong dome. The stratigraphic framework, cross sections, structural and isopach maps are based on the 3500 km2 3-D seismic survey covering the Liaodong dome, Liaozhong and Liaodong sag. The 3-D seismic data demonstrates that the dome formed before the deposition stage of EsM sequence (40 Ma), and it uplifted again during or after the depositional stage of Ed sequence (32-24 Ma). The thermal history dataset consists of 40 well temperature samples, 19 VR samples and 9 AFT samples, which are taken from borehole cores in Liaodong dome. Apatite fission track and vitrinite reflectance data indicate that the dome experienced two stages of cooling episodes, Paleocene to Early/Middle Eocene (65–40 Ma) and Late Oligocene to Late Miocene (30–11.5 Ma), usually indicating uplifting. Both the seismic stratigraphy and thermal history analysis show that: 1) the Liaodong dome is part of the Jiaoliao terrane; 2) regional continental rifting climaxed during 65–40 Ma, as it did the rift-shoulder uplift of the dome; 3) the reactivation of the TLFZ caused a second uplift processes of the Liaodong dome during 30–11.5 Ma; 4) the Liaodong dome uplifted independently and separated from the Jiaoliao terrane. Our results also suggest that it is important to take uplifting evolution into consideration to target a potential petroleum reservoir.
AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016