Sedimentary Characteristics and Models of the Beach-bar Reservoirs in Faulted down Lacustrine Basins

There are many kinds of depositional systems developed in Tertiary faulted-down lacustrine basins of East China, of which beach-bar reservoir has been stressed in recent years because of its close relation with hydrocarbon occurrence. The characteristics of the lithology,grain size,sedimentary structure and sequence, logging and seismic reflection, and distribution for both sandy beach-bar and biological grain beach-bar reservoirs have been demonstrated in faulted-down lacustrine basins of East China through comprehensive use of geological, logging and seismic reflection data. According to their location and sedimentary features, the beach-bar in Tertiary faulted-down lacustrine basins may be divided into four types,i. e. the beach-bar in lake shoreline corner,the beach-bar on subaqueous ancient uplift, the beach-bar by the short-axis delta,and open shallow lake beach-bar. ALso,their sedimentary models have been developed.These beach-bars distribute regularly at the gentle slope of a lacustrine basin through the basin evolution. The practice for oil-gas exploration has indicated the beach-bar on subaqueous ancient uplift and open shallow lake beach-bar possess the ability to accumulate oil-gas,and have become importants target for hydrocarbon exploration.