Characteristics of tight sandstone reservoir in Chang 6 of Yanchang Formation in Ansai area
In order to clarify the characteristics and controlling factors of Chang 6 tight sandstone reser-voir in Ansai area of the central part of the Ordos Basin,a comprehensive study was conducted using methods such as core description,microscopic identification,scanning electron microscopy,and mercury injection experiments to investigate the petrology,physical properties,and pore structure of Chang 6 reservoir.The results show that Chang 6 reservoir in Ansai area is mainly composed of feldspathic sand-stone and lithic feldspathic sandstone,with residual intergranular pores and feldspar dissolution pores as the main pore types,and type Ⅱ(medium-high displacement pressure-micropores)as the main pore structure.The average porosity of the reservoir is 9.97％,and the average permeability is 1.37 × 10-3μm2.The main controlling factors of reservoir properties are sedimentary environment and diagenesis,and the different sedimentary structures under different microfacies result in differences in reservoir properties.Intense diagenesis leads to differences in pore-throat structure,with compaction and pressure dissolution causing a 16.7％loss in porosity.Influenced by the northeast provenance direction,the dis-tribution of different cementation materials results in strong reservoir heterogeneity,and later dissolution improves reservoir properties,mainly through feldspar dissolution,as well as regional zeolite dissolution in the northeast.Based on the diagenetic evolution,the diagenetic stages of Chang 6 tight sandstone res-ervoir in Ansai area are divided into the middle diagenesis A stage.
Yanchang Formationreservoir characteristicsdiagenesissedimentationmain control fac-tors
万方数据
维普
