The reservoir micro-characteristics of Chang 6 in Chuan 72 well block of the Chuankou Oilfield,Ordos Basin

The reservoir micro-characteristics of Group Chang6in Chuan72well block of the Chuankou Oilfield,Ordos Basin has been studied in detail from the aspects of petrology,digenesis and pore structure,based on the observation results from the conventional and casting thin sections and SEM as well as the analysis of the mercury-injection data.On this basis,the reservoir evaluation is carried out.The research reveals that the reservoir in this area mainly consist of feldspar and feldspathic lithic siltstone-to-fine sandstone.The most common digenesis process generally includes compaction,siliceous and carbonate cementation,secondary dissolution and metasomatism and the transformation of clay mineral is also common.There are mainly four pore types in the reservoir,including primary intergranular pore,intergranular dissolution pore and dissolution pore both in lomontite and fedspar.The average porosity of the reservoir is 8.53% and the average permeability is 1.48×10-3 μm2.Thus the reservoir in this area has low and extra-low permeability with small pores and medium-fine throats.Therefore,according to the reservoir evaluation results,the Chang61 layer is better than Chang62 layer.