Evolution on sedimentary system of the Quaternary Ledong Formation,Qiongdongnan Basin
It is proved that as the sustained advancement of petroleum exploration and gas hydrate research,the shallow Quaternary Ledong Formation of Qiongdongnan Basin is not only developed with gas hydrate,but also an active target of shallow oil and gas.Therefore,based on sea-level fluctuation nature,the sequence stratigraphic framework with high precision was established via 3D seismic and drilling data.Furthermore,both evolution and extension were made clear for sedimentary system,which might help theo-retically select exploration targets on shallow gas or gas hydrate in this area.Results show that:(i)there are five third-order sequences in this formation.And the S14 interface as the transitional surface from the progradational continental slope to the aggradational one controls the strata developed with submarine fan;(ii)the sedimentary system in Ledong Formation underwent three evolutionary stag-es.Among which the S20-S14 is mainly from the channel submarine fan of central canyon system supplied by the western provenance,the S14-S12 from the fan given by the northern provenance and mass flow,and the S12-present from compound deposits of both mass flow and sheet-like sand;and(iii)the channel submarine fan where the western provenance originates from the Lower Ledong Forma-tion is featured by wide extension and large depositional thickness,especially sandstone reservoirs with large thickness and coarser grain size.While the other fan where the northern provenance out of the canyon system comes from the Upper Ledong Formation features smaller extension,in which sandstone reservoirs are characterized by thin thickness and fine grain size.In conclusion,there exists a big outlook in petroleum resources in the Lower Ledong Formation in the uplift area of south slope of Lingshui sag,which is also available for shallow gas or gas hydrate exploration.
万方数据
维普
