Sand Body Structure and Genesis in the Braided River Delta Front

The sedimentary types were identified for different sedimentary system tracts of Liu-3 member based on core data, logging and seismic. Four profile sand body stacking patterns and four plane sand body stacking patterns were built for the front of the braided river delta. The profile sand body stacking patterns include upward-protruding progradation with lateral offset stacking pattern, symmetrical accretion with isolated stacking pattern, downward protruding retrogradation with lateral offset stacking pattern and downward protruding progradation with multistorey stacking pattern. The plane sand body stacking patterns include lobe shape, branched shape, bird-foot shape and finger shape. The sedimentary evolution of Liu-3 member has the characteristics of progradation-retrogradation-accretion-progradation. The main controlling factors of sediment source and datum change were analyzed for the different sand body structure patterns.