222 / 2019-06-26 17:48:12

Study on carbonate karst erosion characteristics and microcosmic characteristics- a case study of ordovician carbonate rocks in the western margin of ordos basin

corrosion mechanism,Microscopic characteristics of dissolution,Carbonate rocks,The ordos basin

The corrosion characteristics and microscopic characteristics of Ordovician carbonate rocks in Ordos Basin were studied by simulating the dissolution environment of different fluids (0.2% acetic acid and CO2 with partial pressure of 2MPa) and carbonate rocks under buried conditions. The results show that the dissolution rate of dolomite in different fluids is higher than that of limestone. In deep burial environment, the difference between the two increases is larger. Dolomite is more likely to dissolve than limestone to form dissolved pores; The dissolution rate of limestone and dolomite in acetic acid increases with the increase of temperature and pressure, and the dissolution rate of rock in CO2 increases first and then decreases. At the same temperature and pressure, the dissolution rate of rock in acetic acid is higher than that in CO2; After the dissolution of CO2 and acetic acid solution, the microscopic characteristics of the rock are similar, and the overall dissolution of micritic limestone decreases, forming corrosion pits; The formation of corrosion pits in granular limestone in the inner part of the grains with more developed pores; Intergranular dissolved pores are often formed after dissolution of dolomite; The dissolution of the dolomite is reduced by the dissolution of the dolomitic limestone; Anhydrite dolomites often form paste mold holes. Experiments show that the difference of fluid medium under burial conditions has an important influence on the development of rock dissolution pores. The dissolution ability of dolomite is greater than that of limestone, and the pores are developed after dissolution. It is a reservoir space worthy of attention under the Majiagou Formation.