In this study,we used core flooding techniques to mimic the uniform dissolution in carbonate rocks. Tests sequentially induced mineral dissolution and characterized the impact on multiphase flow properties. Temperature retarded acid was used to uniformly dissolve calcite in Ketton and Estaillades carbonate rock cores. A single dissolution stage removed approximately 0.5% of the mass of the rocks and measurements of relative permeability and residual trapping were made after each stage along with mercury injection capillary pressure(MICP)measurements to quantify the variation of pore throat size distribution. Multiple Stages were performed on each of carbonates rocks. Images from xray micro-CT and medical CT were used to describe the porosity variation and observe the changes in pore structure and multiphase flow properties at scales from the μm to the cm. The pore throat size distribution of the rocks was observed to both increase and become less uniform with progressive dissolution. For Ketton,the micro-pores,with size range from 0.01μm to 0.1μm,have less been involved in the reaction than the macro-pores(10μm to 100μm). A larger spread in capillary trapping was seen around a characteristic initialresidual curve.
展开▼
