Incorporation of Heat in the VAPEX Process: Warm VAPEX

Abstract Warm VAPEX, as one of the variations of vapor extraction process, is investigated in the current research which incorporates heat in a VAPEX process. The idea behind it is to heat the solvent above the dew point temperature of solvent vapors at reservoir conditions and inject it to the reservoir. The superheated vapors carry some sensible heat to the solvent- heavy oil interface and also cause an additional driving force due to mixing, when the solvent vapor condenses at the pore scale. The experiments have been conducted in a rectangular packed glass-bead model. Superheated n-pentane was injected to the model at elevated temperatures, above the model temperature. The model was insulated to lower the potential for heat loss to surrounding and a so-called dummy experiment was conducted to find out the rate of pentane condensation in the system due to heat losses. The preliminary results show the promising feature of warm VAPEX process in terms of enhanced oil production rates. Introduction The vapor extraction (VAPEX) process has recently drawn lots of attention for the recovery of heavy oil. The increasing trend in the energy costs along with great concerns regarding the environmental aspects, global warming, specifically, have provided the opportunity for applying this process for heavy oil recovery, greater than ever. However, the process suffers from an inherent drawback; it is slow in production rate. Creative efforts have resulted in developing several variations of VAPEX with higher production rates than the conventional process, one of which to incorporate heat in the VAPEX process. The idea of using solvent vapors for the recovery of heavy oil was introduced in 1974 [1]. However, unattractive production rates prevented the idea to be tested in the field. A decade after, VAPEX, was introduced as a variation of steam assisted gravity drainage (SAGD), which utilized the horizontal well technology [2]. However, the process was still slow in terms of oil production rate. Several researchers investigated the incorporation of heat in a VAPEX process in order to improve the diffusion-controlled process. Co-injection of solvent and steam/hot water, so-called hybrid VAPEX process, was investigated by several researchers, as a novel approach to VAPEX [3–8]. The steam alternating solvent (SAS) was also studied as a variation of "huff n puff" process, utilizing solvent in cycles along with steam [1, 9]. Near the well bore, electrical heating is also utilized to create a limited hot temperature region during VAPEX process, to recycle the solvent in-situ [10]. Overall, the effect of heat in VAPEX process was found to be promising in terms of comparable oil production rates and decreased energy requirements when compared to thermal oil recovery methods. Warm VAPEX Experiment The experiments for the investigation of warm VAPEX process were conducted in a rectangular packed model. Fig. 1 shows a schematic of the experimental setup used. Liquid n-pentane was pumped at constant flow rate and passed through a tube, wrapped by heating tape. The power of heating tape was adjusted to obtain the desire temperature of injecting solvent vapor at the injection point.

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