Abstract: Gas injection technology enhances oil recovery by maintaining reservoir pressure and improving displacement efficiency. In deepwater turbidite sandstone reservoirs (characterized by high porosity, permeability, and pore pressure), fluid injection alters the elastic properties through gas dissolution in formation fluids, thereby affecting the accuracy of time-lapse seismic monitoring. This study established a rock physics model linking reservoir parameters (porosity and saturation), fluid mixing effects, and elastic moduli (P/S-wave velocities) in turbidite systems, providing a theoretical foundation for seismic response analysis and fluid identification in offshore exploration, particularly in North Sea and Guyana oilfields.