The 2TI reservoir in Lunnan Oilfield exhibits characteristics of deep burial, high temperature, and high salinity. After 32 years of water injection development, the reservoir has entered the ultra-high water cut phase, achieving a water flooding recovery rate of 42%. Despite geological constraints limiting the success of chemical flooding methods such as surfactants and polymers, experimental analysis involving minimum miscible pressure and the comparative assessment of various carbon injection techniques have yielded promising results. The findings indicate that alternating injections of carbon dioxide and water effectively mitigate the rise in gas-oil ratio. This approach also reduces surface tension, facilitating crude oil flow within the small pores under current formation pressures. Field tests conducted on vertical well LN24J2 and horizontal well LN23H1 demonstrate superior gas injectivity capacity in medium and high permeability reservoirs compared to water injectivity capacity. Moreover, it is observed that greater wellbore-reservoir contact area correlates with enhanced gas injectivity capacity. Furthermore, controlling injection rates during gas injection proves effective in preventing gas tonguing. This comprehension significantly informs the transformation and adjustment of development strategies for ultra-deep, high-temperature, and high-pressure medium to high permeability reservoirs.