Study of the effect of the permeability of the interwell space on the efficiency of steam gravity drainage

The paper presents a study of the influence of permeability of interwell space on the efficiency of vapour-gravity drainage under different modes of injection well operation on the basis of numerical modeling. The study was carried out on the model of a reservoir containing highly viscous oil, the dynamic viscosity of which at a reservoir temperature of 8 degrees Celsius is about 25 Pa?•?s. Modeling of non-isothermal multiphase filtration processes is performed using an approach based on implicit pressure calculation by the finite element method and recalculation of saturations of phases after their transfer in accordance with the flow values obtained from the calculated pressure gradients. The temperature field is calculated in two stages: a convective heat transfer is taken into account during phase transfers, and heat propagation due to thermal conductivity of the medium is calculated by solving the boundary value problem for the heat conduction equation. The modeling method takes into account the dependences of phase viscosities on temperature and their densities on temperature and pressure, energy release or absorption during vaporization and condensation, as well as the inhomogeneity of the geological model. Numerical experiments to investigate the influence of permeability of interwell space on the efficiency of steam-gravity drainage were carried out for a heterogeneous reservoir in which a layer with different permeability from the rest of the reservoir is located between horizontal wells. The results demonstrated the difference in oil production and change in steam chamber shape depending on the permeability contrast between the layer and the rest of the reservoir. The model with a permeability layer twenty times lower than the rest of the reservoir showed the highest volume of accumulated produced oil when the wells were operated in the same mode. The possibility of steam or condensed water breaking through to the production well was investigated. At variation of volumes of steam injection, the situations when an increase in steam injection leads to a decrease in the oil share in the withdrawn mixture were obtained. It is shown that for effective application of steam methods of oil recovery enhancement it is important to perform a preliminary reservoir analysis and modelling of expected well operation modes.