Abstract:
Pockmarks, intriguing seafloor geological and geomorphological features, are
commonly observed in marginal basins with hydrocarbon potential. As a Cenozoic
marginal sea, the Andaman Sea is known for its significant petroleum reserves, and
exploring its back-arc continental margin has revealed favourable conditions for
petroleum occurrences. This study focuses on the Tanintharyi passive continental
margin in the Andaman Sea, employing extensive stratigraphic and morphological
analyses based on 2D and 3D seismic data interpretation techniques. Specifically, sub
seafloor characteristics of the Tanintharyi shelf region were investigated, focusing on
comprehensively understanding pockmark morphologies, including their
generation, evolution, migration, preservation, and the complete process leading to
seabed leakage. This study revealed the potential of the Oligocene/Early Miocene
carbonate platform in the Tanintharyi shelf region as a significant hydrocarbon reservoir for the upwelling buoyant fluids from the deep East Andaman Basin.
Besides reservoir function, this carbonate platform serves as a passageway for the
migration of fluids from the deep-sea area to the shallow-sea area, thereby playing a
pivotal role in supporting fluid expulsion mechanisms in shaping a pockmark train
adjacent to truncated sedimentary formations surrounding a geomorphological high
on the contemporary seafloor. Additionally, the study examines the influence of
changes in sedimentary facies and the tectonic setting of the Andaman Sea on
pockmark evolutions, with a specific emphasis on the role of the uppermost shallow
marine shale beds in developing sub-seafloor overpressure systems due to their
impermeable seal rock properties. The article presents substantial evidence for the
initiation of pockmark fields during the Middle Miocene period, followed by their
transformation into pockmark trains on the present-day seafloor, attributed to the
triggering effect of sub-seafloor overpressure systems due to changes in sedimentary
dynamics in the Andaman Sea.
