Research on the mechanism of acidizing the carbonate Gaoyuzhuang Reservoir, North China: Insights from field experiments and numerical simulations

• Novel framework for predicting geothermal reservoir acidizing is proposed. • Pressure variations in the field wellbore and permeability variations in the reservoir are incorporated. • Acidizing is not viable for reservoirs with natural permeabilities of less than 5mD. • The acidization of the Gaoyuzhuang reservoirs to enhance production cannot be achieved through the utilization of SCO 2 . • Supercritical CO2 has little effect on acidification of the Gaoyuzhuang reservoir. The reservoir in the Gaoyuzhuang Formation in the Xiong’an New Area is characterized by high temperatures and favorable water quality, indicating that it has a significant potential for development. However, the reservoir is highly heterogeneous, and acid modification is required in the low porosity–permeability regions to achieve large-scale development. The objective of this study was to address the issue of the unclear acid–rock reaction mechanism and kinetic processes in the carbonate reservoirs in the Gaoyuzhuang Formation. Considering the findings of preliminary geological condition studies and laboratory acid–rock reaction experimental studies, on-site reservoir acidizing was initiated. Subsequently, a numerical model of the reservoir acidification was constructed to ascertain the relationship between the porosity and permeability. Ultimately, the characteristics of the Gaoyuzhuang reservoir, including the porosity and permeability conditions, initial temperature, mineral composition, and supercritical carbon dioxide acidifier, were analyzed to evaluate the acidizing effect. The results indicate that the dissolution of dolomite and calcite in the vicinity of the wells is the primary acidification mechanism in the reservoir. The modification effect increases with increasing permeability. Acidizing is not a viable solution for reservoirs with natural permeabilities of less than 5 × 10 –15 m 2 . As the temperature increases, the efficacy of the acidizing near the well improves. The acidification of reservoirs with high clay contents is less effective than that of reservoirs with high calcite contents. The acidization of the Gaoyuzhuang reservoirs to enhance production cannot be achieved through the utilization of SCO 2 . The results of this research not only provide evidence to support the exploitation and utilization of geothermal resources in North China but also improve our knowledge of the mechanisms of water–rock interactions.