Main controls on the distribution of the 3rd member of Liushagang Formation in eastern Wushi Sag, Beibu Gulf Basin

Fan delta reservoirs in the 3rd member of Liushagang Formation in the eastern Wushi Sag, Beibu Gulf Basin are characterized by large thickness of sand bodies, complicated lithology, rapid change of physical properties, and unclear distribution of good-quality reservoirs, which restricts further development. The controls of the sedimentary environment, diagenesis and structure on reservoir physical properties were studied using drilling, logging and testing data. Shale content, sorting and psephicity have a huge influence on physical properties. Compaction and dissolution controlled later reservoir porosity evolution. Paleotectonics and fracture systems controlled acid fluid migration direction and path. Underwater distributary channels of the proximal outer fan delta front near the large fault which exhibited low matrix content, good sorting and psephicity, good physical properties, high productivity and were good-quality reservoirs in the study area.