A Heated-Radius Calculation Model for Multicomponent Thermal Fluid Huff-and-Puff in Heavy Oil Reservoirs

Abstract Multicomponent thermal fluid consists of several gaseous components, and the actual temperature distribution within the heated zone is nonisothermal, rendering the Marx–Langenheim isothermal heating model inapplicable. In this study, based on the energy release behavior of multicomponent thermal fluid during the heating of the oil reservoir, the heated zone is partitioned into a latent-heat zone and a sensible-heat zone, and a heated-radius calculation model is developed in accordance with the energy conservation principle. The results indicate that the predictions from the proposed model match well with the CMG simulation results, with relative errors ranging from 0.23% to 3.32%. In the process of multicomponent thermal fluid huff-and-puff development, increasing steam quality and injection amount while decreasing noncondensable gas (NCG) content can effectively expand the heated radius. Moreover, the heated radius increases with an increasing number of huff-and-puff cycles, with residual formation heat being the primary driver of this continuous enlargement. Among the reservoir parameters examined, the equivalent volumetric heat capacity and thickness of the reservoir were found to have the most pronounced influence on the heated radius. This study provides a theoretical foundation for predicting the heating radius and optimizing parameters in multicomponent thermal fluid huff-and-puff operations.