叠置河道砂体侧向沉积期次刻画及对油气勘探的指示:以川中资阳地区须家河组五段为例OA

The Xujiahe Formation is the main natural gas-producing layer in the terrestrial strata of the Sichuan Basin,characterized by a widely distributed deltaic sedimentary system with thick reservoirs and prominent vertical and lateral stacking patterns.However,the lack of effective methods for fine-scale characterization and dissection of sand bodies within the formation has long hindered exploration efficiency.This study focuses on the extensively distributed channel sand bodies in the 5th Member of the Xujiahe Formation in the central Sichuan Basin.Through detailed core observations and single-well analyses,the sedimentary and seismic response characteristics were clarified,enabling an integrated geological-seismic fine-scale characterization of channel depositional stages.The results indicate that large-scale channel sand bodies were formed by multi-cycle vertical deposition and multi-stage lateral migration and stacking.Seismic waveforms effectively represent channel stacking patterns:sand bodies from multi-cycle channel deposits exhibit chaotic seismic waveforms,while stable channel sand bodies show continuous seismic waveforms.Areas with large-scale lateral migration and stacking of channel sub-sand bodies display composite wave characteristics.Based on seismic response characteristics,four distinct phases of lateral migration have been identified.Through detailed analysis and fine tracing of seismic waveform features across multiple regions,the planar distribution range of channel sand bodies for each phase has been predicted.The early-stage channel sand bodies exhibit poor stability and high clay mineral content in the reservoir.In contrast,the middle-to-late-stage channel sand bodies demonstrate good stability,low clay mineral content,and favorable reservoir physical properties,making them the primary targets for exploration.