Investigation of the Vapex Process in High-Pressure Fractured Heavy-Oil Reservoirs

摘要

In this work, the vapour extraction (VAPEX) process wasrnstudied in a multiple block, dual porosity fractured system.rnThe performance of this process is compared with arnconventional, non-fractured system under similar rock andrnfluid properties, bulk volume, pore volume, hydrocarbonrnvolume, and injected pore volume of solvent and solventrninjection rate. At early stages of the VAPEX process inrnfractured system, the solvent-oil interfaces form and developrnfrom all sides of the matrix, and the oil chamber, rather thanrnsolvent chamber forms and shrinks in the center of each block.rnAlso, at later stages of the process, the solvent zones from allrnneighboring blocks combine and form an integrated solventrnzone, which is similar to that in the conventional systems.rnThe results showed that in low-permeability carbonaternreservoirs, the fracture network provides communications forrnsolvent flow through which the solvent can flow faster andrnform solvent fingers at early stages, which can reach thernblocks located at farther distances from injection well. It wasrnfound that the solvent breakthrough starts at he same time inrnboth low-permeability non-fractured system and fracturedrnsystem. This is because the solvent flows directly throughrndrained areas towards producer in both systems.rnFurther, effect of solvent injection rate on heavy oil recoveryrnin the fractured system was studied in two cases: differentrninjection rate at the same injection time, and different injectionrnrate with the same injected pore volume. It was found that thernsolvent injection rate should be optimized for a specificrnsystem in order to control the solvent breakthrough and tornavoid extra operation time and cost.