Deep Buried Dissolution of Ordovician Carbonates in Tazhong Area of Tarim Basin

Abstract

Based on the observation of cores and rock sections,a deep buried dissolution,the types of buried dissolutions,development features,genesis and factors of reservoir formation in Tazhong Area of Tarim Basin were comprehensively analysed.The study shows that buried dissolutions of Ordovician carbonate in Tazhong Area are developed at multi-stages and various scales,including organic acid dissolution and thermal dissolution.The organic acid dissolution is characterized by fabric non-selective dissolution,and most of dissolution pores are filled with hydrocarbon.Organic acid dissolution constitutes the first high-porosity zone in the deep area.The thermal dissolution is characterized by fabric selective dissolution,and the dissolution developed mainly along faults and fractures,and fluorite,chlorite,sphalerite,high-temperature quartz,barite and other hydrothermal minerals are developed.The hydrothermal fluid mostly comes from the deep crust,and has a relationship with the magmatic activity.The thermal dissolution constitutes the second high-porosity in this area.