Deposition Modes of Shallow Braided River Delta in Sangonghe Formation of Jurassic in Baolang Oilfield

Braided river deltas,formed during progradation from braided rivers to lakes,are extensively developed in the Sangonghe Formation of Jurassic in Yanqi basin.This type of delta is markedly different with other types and its prin-ciple parts are braided distributary channel and under wa-ter distributary channel.The main oil-bearing intervals in Baolang oilfield are braided distributary channel sand with highly-developed river islands as its leading features,and are typical shallow ramp coarse deposits in braided river delta environment.