Experimental Multiple-Contact miscibility and PVT properties with equation of state modeling for High-Pressure nitrogen injection into deep reservoirs with Tahe heavy and light crudes

•The results of both experimental and theoretical research conducted to study the forward and backward multiple-contact miscibility, as well as the PVT and viscosity changes of two Tahe crude oils through high-pressure N2 (or lean CO2 in N2) injection, are presented.•The experimental pressures and temperatures reach up to 69 MPa and 148 °C. The experimental data on equilibrium phase compositions, densities, and viscosities during the multiple-contact processes under high-pressure and high-temperature conditions are included.•The PR-EOS is utilized to calculate the pseudo-ternary phase diagram for the forward/backward multiple-contact processes. The simulation results agree well with the experimentally measured composition data. The pseudo-ternary diagram indicates that both N2 and the N2/CO2 mixture can develop a miscible drive process for the light oil under the corresponding reservoir pressure and temperature.•New parameters for the volume shift and viscosity models are introduced, and improved density and viscosity calculation results from the PR-EOS are obtained for the reservoir fluids of the Tahe oilfield, particularly for the heavy oil. To evaluate the potential miscibility, as well as the PVT (pressure–volume-temperature) properties and viscosity changes of N2 and N2/CO2 mixtures with light and heavy crude oil in the Tahe oilfield, multiple contact experiments were designed and conducted. The results of both experimental and theoretical research conducted to study the forward and backward multiple-contact miscibility, as well as the PVT and viscosity changes of two Tahe crude oils through high-pressure N2 (or lean CO2 in N2) injection, are presented. The experimental pressures and temperatures reach up to 69 MPa and 148 °C. The experimental data on equilibrium phase compositions, densities, and viscosities during the multiple-contact processes under high-pressure and high-temperature conditions are reported. The PR-EOS is used to calculate the pseudo-ternary phase diagram for the forward/backward multiple-contact processes. The simulation results agree well with the experimentally measured composition data. The multiple-contact experimental data, along with the equation of state modeling results shown in the pseudo-ternary diagram, indicate that both N2 and the N2/CO2 mixture can develop a miscible drive process for the light oil under the corresponding reservoir pressure and temperature. New parameters for the volume shift and viscosity models are