Abstract: The challenge of wide brine source and its additional problems come from the economy (energy consumption and other costs), security (re-dissolution of surrounding salt rocks), and environment (groundwater pollution by brine) of salt cavern oil storage are worth examining to improve the efficiency of oil storage. Against this background, this work presented an operating mode of salt cavern oil and gas co-storage and using natural gas displacement for petroleum recovery. A gas–oil two-phase flow model with gas dissolution and exsolution was proposed to evaluate the application prospects of the new method precisely. Numerical studies indicated that the gas void fraction at the wellhead under quasi-steady state conditions is approximately 0.153, which belongs to bubbly flow, and the pressure at the wellhead of the central tube increased from 5.54 to 6.12 MPa during the entire transient flow stage, with an increase of 10.47%. Compared to the traditional method of using brine as the working fluid, the pump pressure rises from 2.92 to 14.01 MPa. However, if the new mode can be linked with the salt cavern gas storage and when the initial wellhead gas pressure exceeds 13 MPa, the energy consumption of the new method will be lower than that of the traditional brine-based operational mode. A new empirical formula is proposed to determine the two-phase flow pattern under different operating parameters. A special focus was given to energy consumption for oil recovery, which grows roughly in accordance with the operating pressure and oil recovery rate. However, the energy cost per volume of crude oil remains almost unchanged. This work provided a new solution for the serious brine problem and is expected to achieve petroleum recovery through natural gas displacement.