CONTROL OF MASS TRANSPORT DEPOSITS OVER THE OCCURRENCE OF GAS HYDRATE IN QIONGDONGNAN BASIN

Tectonic movement has become inactive since the Miocene in the Qiongdongnan Basin.The thickness of sediments from the Miocene to present comes to 5000~9000 m.The well of Ya35-1-2 reveals that the Pleistocene are dominated by fine-grained sediments characterized by interbedded mudstone and silt.There is lack of vertical pathways for fluid migration.The interpretation of high resolution 2D and 3 D seismic data reveals that there are gas chimneys and mass transport deposits occurred in the Pliocene.The gas chimneys may provide vertical pathways for fluid migration from the deeper sediments to the shallower part.Sediments would be remolded during the transport.The MTD layer usually has higher resistivity,higher density and lower permeability than the bounding sediments due to compaction.It may act as a seal for hydrocarbon accumulation and favor the formation of gas hydrate.