Diagenesis and Its Effect on Reserveroir Quality in Chang6 Reservoir of GanGuyi Oil Field

Sedimentary during stage of Chang 6 was controlled by a lacustrine delta plain distribution channel,delta front underwater distribution channel and mouth bar sandstone in GanGuyi Oil Field in Ordos basin.Sandstone is consist of fine-middle grained arkoses.The main diagenetic mineral of the sandstones include: chlorite grain rim,calcite cement,quartz and feldspar overgrowth,illite,illite-montomorillonite mixed layer,albite and kaolin.During the diagenetic process,the mechanical compaction and cementation which result in primary porosity loss almost are the main factor causing the lowest permeability in the early diagenetic phase;the dissolution that calcite and laumontite were dissolved improved the porosity and permeability.It makes Chang 6 for a sweat reservoir and advantaged facies belt in Ordos.