Due to the strong heterogeneity of carbonate reservoirs, significant differences in reservoir utilization often occur during waterflooding development. Conventional methods for evaluating the degree of waterflooding reserves utilization mainly rely on Production Logging Tool data, which can only reflect the thickness utilization and cannot quantitatively describe the dynamic changes in waterflooding development efficiency. To address this issue, this paper proposes a method that utilizes continuous production test data from the same well location and applies the Lorenz curve to calculate the coefficient of variation of thickness utilization. This approach quantitatively characterizes the heterogeneity of fluid production and water absorption profiles within the reservoir. By systematically analyzing historical production test data and calculating the coefficient of variation of thickness utilization at different production stages, the evolution of waterflooding heterogeneity was revealed. The results indicate that this method effectively quantifies spatial variations in waterflooding performance, identifies dominant flow channels and low-efficiency zones during injection development, and provides a scientific basis for adjusting reservoir development strategies.Based on the findings, this paper further proposes optimization strategies for the Kazakhstan X carbonate reservoir, including adjustments to the injection-production structure, modifications to the injection method, and optimization of water injection rates. These measures aim to enhance waterflooding efficiency, improve reserve utilization balance, and provide technical support for the efficient development of carbonate reservoirs..