Influence of Turbidity Sedimentary Environment on Gas Accumulation in the Deep-water Fan of the Bay of Bengal
Abstract
In order to further determine the influence of turbidite flow on gas accumulation in the Bay of Bengal, the paper applies 2D/3D seismic data and well data to study the Miocene-Pleistocene depositional architecture, evolution and reservoir quality of deep water fan in Bay of Bengal. Local sequence stratigraphic framework and sedimentary environment and accumulation model of deep-water fan are established in the Bay of Bengal. By using cyclical variation of fine and coarse granular sizes of deep-water sediments in study area, combined with cyclical variation of the amplitude in corresponding seismic profiles, five sequence interfaces of deep-water fan in Bay of Bengal on seismic profile can be identified. Results show that the TOC/TN ratios of continental and marine organic matter in the Bay of Bengal are 11.2 and 4, respectively, and the organic matter comes from mixed sources. Continental and marine facies account for 60% and 40% respectively. Six different types of deep-water architectural elements are recognized. Miocene channel complexes and Pliocene confined slope channel complexes and Pliocene channels and frontal splays in seismic facies show the best reservoir property. Key factors of hydrocarbon accumulation of the deep-water fan in the Bengal Basin include effective source rocks, deep-water fans at low water level and their overlying high-level-stage mudstones, which form favorable reservoir-cap combinations. Meanwhile faults, unconformities and wide-spreading sand bodies compose of favorable petroleum system. The amount of discovered natural gas in the Bay of Bengal is 101.52×108 ft3. The reservoir mainly located in the aggradation constrained channel complex in the middle-upper fan belts, as well natural levee sand bodies of tidal channel near “bottomless channel” in middle-lower fan belts. The formation mechanism of turbidity sedimentary indicates the direction of natural gas exploration and development in the same environment around the world.
