Abstract: Against the backdrop of the global energy structure transition and the advancement of "dual-carbon" goals, the CO₂ plume geothermal system (CPGS), as an innovative technology that synergizes geothermal development with carbon sequestration, has attracted widespread attention due to its dual value in clean energy supply and greenhouse gas emission reduction. To clarify the influence of different reservoir physical properties and operating conditions on the heat extraction performance of the CPGS, this study focuses on the deep thermal reservoir in the Yulou section of the Liaohe Oilfield. Using COMSOL Multiphysics software, a three-dimensional numerical model coupling thermal, hydraulic, and mechanical (THM) fields was developed, and the effects of reservoir physical properties (initial porosity, rock specific heat capacity, and thermal conductivity) and operating conditions (injection-production rate and well spacing) on the heat extraction performance of the system over 50 years of operation were systematically investigated. The results show that the reservoir physical properties, in decreasing order of their influence on the heat extraction performance, are specific heat capacity, initial porosity, and thermal conductivity. Regarding operating conditions, the injection-production rate has a significantly larger impact than that of well spacing. An increase in the rock specific heat capacity effectively delays the temperature decline of the reservoir, extending the time for the production temperature to drop to 373.15 K from 37.80 years to over 50 years, with the minimum long-term temperature decay rate being only 0.130 K/year. However, the heat extraction ratio at 50 years is reduced by up to 18.37%, while the long-term flow impedance decreases slightly. An increase in the initial porosity improves reservoir permeability conditions, increasing the heat extraction ratio at 50 years by up to 32.65%, but simultaneously accelerates reservoir cooling, advancing the time for the production temperature to fall to 373.15 K to as early as 27.60 years and correspondingly increasing long-term flow impedance. An increase in the rock thermal conductivity has a slight delaying effect on the temperature decline, but its overall impact on heat extraction performance is the weakest, with a maximum variation of only 6.12% in the heat extraction ratio at 50 years. Furthermore, its influence on flow impedance exhibits non-monotonic behavior with an inflection point at 17.36 years. Increasing the injection-production rate significantly enhances the heat extraction ratio of the system, with a maximum increase of 55.10% at 50 years and a reduction of 16.37% in long-term flow impedance, but advances the CO₂ breakthrough time to 0.39 years, accelerating the reservoir temperature decline. Increasing the well spacing improves the long-term thermal stability of the system, extending the time for the production temperature to drop to 373.15 K from 26.60 years to 37.80 years, but increases the flow impedance at 50 years by up to 35.56%, increasing the energy consumption of the injection-production cycle. This study reveals the influence mechanisms of multiple parameters on the heat extraction performance of the CPGS and identifies core parameter thresholds for this region based on simulation results, providing theoretical support for the design optimization, parameter selection, and long-term stable operation of CPGS projects in the Liaohe Oilfield, as well as a valuable reference for geothermal development in other regions of China.