Dissolution Kinetic Characteristics and Morphology Evolution of Oolitic Limestone

Key words: 
• oolitic limestone

Abstract: Oolitic limestone is an crucial oil reservoir. Through dissolution kinetics experiment under normal temperature and pressure, this paper discussed dissolution kinetics characteristics and morphology evolution of oolitic limestone. The result indicates that oolitic limestone dissolution is main controlled by petrotextural features and chemical composition. Petrotextural feature control is characterized by selective dissolving textural weakness, such as tectonic microfracture, crack in ooid especially oolitic radiate crack, binding domain between grains and crystals and so on. Chemical composition control is characterized by prior dissolution of dolomitized particles and inhabitations of clay mineral and quartz. To dolomitized particles, they not only dissolve easer itself, but also could accelerate rock dissolution. However, to clay mineral and quartz, their inhabitations are more harmful to ooids and dolomitized particles' dissolution than to substrate. During oolitic limestone dissolution, firstly, it brought dissolved crack, intergranular pore, intercrystalliine pore after tectonic microfracture and crack in ooid. Secondly, it led to interpartide pore and intercrystalliine pore with dolomitized particles and calcite around them dissolved. Then, along with further dissolution, annular channel could be formed around ooids. Finally, it would form oolitic moldic pore in surface after ooids fell off substrate.