Study on Prediction Model for Mineral Dissolution Rate in Unconsolidated Sandstone during Steam Flooding

Heavy oil reservoirs are predominantly composed of unconsolidated sandstone formations. During the conversion to steam flooding development, the temperature of the steam chamber in the reservoir typically ranges from 200 to 300 °C, and the steam quality is generally 0 to 0.6. High-temperature steam (hot water) can dissolve minerals, causing changes in the formation permeability. In this study, sand-packed tube experiments were conducted to simulate high-intensity steam flooding in unconsolidated sandstones. Through the analysis of dissolved minerals in produced water and sand samples before and after dissolution, the reaction characteristics of mineral dissolution under different influencing factors were obtained. Considering the effects of the steam injection temperature, steam quality, and injected pore volume (PV) number on the mineral dissolution rate, a prediction model for the mineral dissolution rate in unconsolidated sandstones was established by using the Boltzmann distribution function and density model. The results show that the steam injection temperature, steam quality, and injected PV number all affect the mineral dissolution rate to varying degrees. Among them, the steam injection temperature has a significant impact on the maximum mineral dissolution rate, serving as the main factor determining the degree of mineral dissolution. The model calculations show good agreement with the experimental results, providing theoretical support for steam flooding reservoir engineering research and development scheme design.