Characteristics of Chang 6 Reservoir of the Huaqing Area in the Ordos Basin

Based on the analysis of thin sections and physical property of Chang 6 reservoir in Huaqing area, the paper studied the petrology feature, pore styles, the microscopic reservoir structure, characteristics of porosity and permeability as well as the diagenesis. The results suggest that delta sediments and turbidite fan of deep water are the main deposits in the Chang 6 reservoir. Delta front underwater distributary channel and turbidite fan are the main facies belt forming reservoirs of Chang 6. Lithic arkose sandstones, and feldspathic sandstone are major rock developed in this area; the granular pore and secondary feldspar-dissolution pore are the main pore types. Pore throat presents fine pore and fine throat with high micro-heterogeneity. The average porosity is less than 9.5%, and the permeability is below 0.38×10^-3μm². So Chang 6 reservoir belongs to low porosity and low permeability reservoir. The low-permeability sandstone had undergone complicated diagenesis, especially compaction, cementation and dissolution. The compaction and cementation that lead to porosity loss are the main factors causing low porosity and permeability. But the dissolution, especially dissolving pores in the feldspar and authigenic laumontite largely improves the reservoir property.