Horizontal producers deliverability in SAGD and solvent aided-SAGD processes: Pure and partial solvent injection

•A new concept of sandface subcool is defined and formulated.•Solvent mole fraction and chamber pressure control flashing at the sandface.•After flashing, the liquid mobility is reduced and emulsion rate drops.•Increase of pressure drawdown may have a negative effect on oil production. The subcool or thermodynamic trapping for solvent applications is inefficient since solvent viscosity is only a weak function of temperature. Another factor that affects the efficiency of the thermodynamic trapping is that the pure solvent injection recovery processes are operated at low pressure, which does not provide a large temperature window for operators to apply large subcools. Such challenges make the pure solvent injection recovery process a perfect case for the deployment of Flow-Control-Devices (FCDs). FCDs have shown great potential for enhancing recovery in SAGD production wells. The application of FCD in SAGD has been primarily positive, and the performance of most producers improved with FCDs. Application of FCDs is even more crucial in pure solvent injection recovery processes due to the large amount of solvent in the liquid pool and the small latent heat of solvent in comparison to water. With FCDs, the drawdown pressure is typically higher, resulting in flashing near the wellbore, and it is correlated to latent heat of the main fluid in the liquid pool. The flashing creates either steam or vapor breakthrough, reducing the relative permeability of the liquid phase. That creates a new equilibrium that stabilizes at lower rates. Such a new equilibrium analysis is conducted by forcing a new temperature gradient to the model. This, in turn, creates an environment leading to extensive solvent-breakthrough, called solvent-coning in this study. The main output of such analysis is the produced solvent gas fraction produced at the sand-face, which is an important input for FCDs analysis.