Trace of Hydrocarbon Migration Interpreted on Seismic Data: A Case Study from the Offshore Bohai Sea, China
Wang, Yingbin; Huang, Lei
The hydrocarbon's migration can leave some traces on its pathways; through the study on many successful exploration cases offshore the Bohai Sea (China), we identify several manifestations of this kind of traces on seismic data. (1) The "gas chimney" is present around the fault by which the hydrocarbon migrate. The exploration in the areas with "gas chimney" revealed that, the drilling wells have active hydrocarbon show and thicker hydrocarbon layer in these and adjacent areas; for example, a vertical distance with up to 1000 meters long hydrocarbon reservoir is present in some wells. And thus, we suggest that the "gas chimney" on seismic image is the direct evidence for the hydrocarbon's vertical migration along the fault, and is the mark of favorable zone for hydrocarbon prospecting. (2) At the uppermost of the seismic image (i.e., the seafloor) where the fault extend upward to the seafloor, it shows a characteristic of low frequency and bright amplitude, and at the top of the fault it shows a characteristic of pockmark. This phenomenon is also caused by the hydrocarbon leakage along the fault. The statistical analysis of the exploration results shows that the hydrocarbon reservoir is easy to find in the trap with the above phenomenon. (3) The bright amplitude or anomalous amplitude occurs on the seismic data of the petroliferous structures. The detailed study shows that the petroliferous structures usually have the following anomalies on seismic data: lateral variations along reflections as local increases or reductions in amplitude strength, continuity, frequency.
We had a good harvest through the application of the above experiences to the further hydrocarbon exploration practices; so we suggest these experiences and rules have a property of universality, and are valuable to be popularized and applied in hydrocarbon exploration of the other similar rifting basins.
AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013