Tee-SVX: Enhanced Oil Flow Rate in Solvent Vapor Extraction Process

Abstract

The production rate in classical vapor extraction (VAPEX) is far too low for the process to be considered commercially viable. This is largely because the classical process utilizes forces of buoyancy and mass transfer by diffusion and dispersion to distribute the solvent and gravity to drain the diluted oil to the producer. This article presents a new well pattern Tee-SVX which may enhance the oil-flow rate by two to ten times over that of the classical approach. In the new well pattern, additional horizontal injectors, perpendicular to the injector and the producer in Classical VAPEX, are placed in the topmost region of a reservoir. The oil-rate-enhancement mechanism for this new well pattern involves two features. First, the operation pressure of the top injectors is set slightly higher than the bottom injector pressure. This facilitates a downward driving force to assist gravity drainage of diluted oil to the producer. Second, the supplementary injectors generate an additional diluted oil profile perpendicular to the diluted oil profile of the Classical VAPEX process. Therefore, in the new well pattern, the heavy oil is solvent contacted and diluted in both vertical planes (one plane perpendicular to and the other parallel to the horizontal producer), whereas in Classical VAPEX, the heavy oil is diluted in only one. A series of numerical simulations were conducted to evaluate this process. In order to obtain reliable evaluation results, the numerical dispersion was eliminated through extrapolating the simulation results at different grid sizes to an infinitesimal grid size (Δy → 0). The simulation results suggest that the oil-flow rate can be enhanced two to ten times greater than that with Classical VAPEX, depending on the well spacing of the top injectors. For example, for a well spacing of the top horizontal injectors of 120 m, the oil-flow rate from the original producers will be 5.5 times higher than that of Classical VAPEX. For thinner reservoirs, the Tee-SVX can enhance the oil-production rate higher compared with Classical VAPEX. For reservoirs with a small gas cap, Lateral-SVX with vertical injector is quite effective.