Abstract:

Based on the review of deepwater depositional elements’ research in the world, combined with the exploration practice of Baiyun deepwater area, the deepwater depositional elements in Baiyun deepwater area are studied. The deepwater depositional elements include channel, levee-overbank, sheet sand and mass-transport deposit. The channel is one of the main components of deepwater deposits and the important reservoir in Baiyun deepwater area. The channel fills have been classified into three broad categories: erosional, erosional/aggradational and aggradational channel genetically. The nature of channel-fill deposits varies greatly. Deposits can include gravel, sand, mud, and mixed fill. Levee-overbanks are dominated by muddy and silty deposits, and its trends roughly parallel to the channel, spreaded laterally away from channel, good lateral continuity and poor vertical communication. Sheet sands are deposited at the terminus of channels and are characterized by their lobate external form. Sheet sands can be divided into layered and amalgamated types. Layered sheets are characterized by relatively low net gross with interbedded shale and sandstone beds. Amalgamated sheets are characterized by high net gross, comprising stacked sandstone beds with fewer interbedded shales. Masstransport deposit includes what is commonly termed slumps,s lides, mass flows, debris flows, slope failure complexes and mass-transport complexes,etc. It can erode the underlying strata and widely distributed, and it can also serve as a good seal for oil and gas.

Key words: Baiyun deepwater area, deepwater deposit, depositional elements, channel, levee-overbank, South China Sea, reservoirs