Geological controls on focused fluid flow in the Song Hong Basin, offshore Vietnam

Abstract

This study uses 2D seismic lines located in the central Song Hong Basin, covering an area of c. 3900 m2, in the water depth of c. 100 m. Focused fluid flows are developed intensively and can be classified into two types: blow - out pipe and seepage pipe. They have similar seismic characteristics as a vertical zone of disturbed seismic reflections. The significant difference between them is the blow - out pipes associated with seafloor pockmarks and paleo - pockmarks which are absent in the seepage pipe. Besides, the scale of the blow - out pipe is larger, compared with the seepage pipe. The blow - out pipe is c. 500 m wide and 450÷3500 ms TWT; the seepage pipe is smaller scale, c. 200 m wide and 500 ms TWT. Blow - out pipe is rooting from the sequence just above the diapir or deformation unit or deep lacustrine mudstones from the Late Eocene to Oligocene, and marine mudstones from the Early to Middle Miocene. The seepage pipe is rooting from the sequence above the diapir. The focused fluid flow is supposed to be controlled by the overpressured deep source layers and passive diapirism. The occurrence of focused fluid flow is an indicator for the active petroleum system in the study area. Intensive development of focused fluid flow proves a great hydrocarbon potential in the Song Hong basin.