The forming process and development pattern of shallow water delta in fault depression lacustrian basin: a case study of AG Formation in the Jake area in Fula sag, Muglad Basin, Sudan

Taking the Jake area in Fula Depression, Muglad Basin, Sudan as an example, the sedimentology characteristics of shallow water delta in lacustrian basins were studied using core, logging and 3D seismic data in combination with flume simulation experiment, so as to summarize the formation process and development pattern of shallow water delta. Shallow water deltas are developed in the upper part of the Cretaceous Abu Gabra Formation in the Jake area, where the scale of single lobe and sediment thickness gradually decrease with decreasing water depth. In the vertical direction, there are small imbricate, wavy, flaky and divergent progradational reflection patterns; the length-width ratio of single event increases successively. On the horizontal level, frequent bifurcation and divagation of channels in lobes result in the scale-like distribution of distributary channels. The development period of shallow water delta is greatly influenced by seasonal fluctuation of water level and sediment supply. A cycle of sedimentation can be divided into flood period, interflood period and drought period. In the flood period, sediment supply is adequate. In the early-middle stage, water level is high and channels are destroyed under water; lobes move forward quickly, showing blanket deposit. In the late stage, water level decreases and lobes break the surface of water. Thus, new channels are formed. During the interflood period, water level is relatively high and sediment supply is adequate; the mainstream line frequently changes and channels are wide and shallow; lobes expand significantly. In the drought period, sediment supply is deficient and water level is low; channels are narrow and deep, undercutting lobes; the construction effect of lobe is weak. © 2016, Editorial Office of ACTA PETROLEI SINICA. All right reserved.