Features of Gas Chimney and Hydrocarbon Accumulation in Rakhine,Myanmar

High resolution seismic data,combined with geophysical techniques including seismic attributes,inversion,time slice of coherence,can be used to identify the typical gas chimney in the deep sea area.The gas chimney consists of root,crossing area and spire,and with corresponding seismic anomalies.In Rakhine sea area the gas chimneys generally are distributed in two modes.(1) Accompanied by the fault and located in the footwall with low stress areas;(2) Associated with abnormally high pressure in the lower part of the formation and located in the structure with easily broken layer.Both of these two types of chimneys are associated with the overpressure and the fracture of stratum and belong to the overpressure-fault-seepage.There are two hydrocarbon accumulation modes related with the gas chimney in Rakhine,Myanmar.The first is that the oil/gas migrated vertically or laterally along the fault and accumulated in the shallow reservoirs,the other is that the oil/gas in the source rocks spired the overburden layer when its pressure broken the formation fracture pressure of the overburden layer and migrated vertically along the split channel until sealed by the mud-filled canyon and accumulated in the reservoirs of gas chimney’s wing where the thick mudstone on the top of the reservoir acts as the main seal and the mud-filled canyon as the lateral seal.