Canadian International Petroleum Conference · 2006 · 25 citations · 0 references
Abstract SAGD and CSS are the main commercial technologies used for in-situ recovery of bitumen in Alberta. Due to the increasing costs for energy (natural gas) and the increasing restrictions on fresh water usage, VAPEX and other technologies have been proposed as alternative technologies for heavy oil production. VAPEX uses a pair of horizontal wells, similar to SAGD, but uses a gaseous solvent, typically propane, to mobilize the oil. The Thermal Solvent process uses a light hydrocarbon solvent, injected into the upper will of a horizontal well pair. The action of the solvent is augmented by heating the wellbores, possibly by a steam loop. The Hybrid Solvent process injects light hydrocarbon solvent (propane) plus a modest amount of steam, sufficient to vaporize the solvent. Several scaled laboratory model experiments were designed to evaluate VAPEX and other solvent-based processes for recovery of heavy oil or bitumen. One experiment evaluated the VAPEX process in Athabasca UTF bitumen. Two experiments were completed to evaluate the Thermal Solvent Process. Two experiments were completed to evaluate a Hybrid Solvent process. All experiments were compared using a common set of economic assumptions. The economic results indicated that a hybrid process could be cost-competitive with SAGD for a 30 m thick Athabasca formation, and that the Thermal Solvent process could be competitive in certain thick heavy oil situations. Introduction Heavy oil and bitumen reservoirs may be immobile at reservoir temperature, or they may have some initial oil mobility and some reservoir drive energy. These reservoirs may contain dead oil, as in the case of Athabasca bitumen, or they may have some dissolved gas, as in the case of Cold Lake or Burnt Lake reservoirs. SAGD is the main commercial technology used for in-situ recovery for Athabasca reservoirs. Due to the increasing costs for energy and the increasing restrictions on fresh water usage, VAPEX has been proposed as an alternative technology for bitumen production. VAPEX uses a pair of horizontal wells, similar to SAGD, but uses a gaseous solvent, typically propane, to recover the oil. Experimental evaluation of VAPEX and related processes for mobile heavy oil recovery was assessed by Alberta Research Council in Reference 1. The VAPEX process may be augmented by adding heat. Heating of a horizontal wellbore will reduce viscosity sufficiently to produce a large increase in oil rate. The heat will also serve to initiate communication between the injector and the producer. The heat will serve to speed the diffusion of solvent into the oil. The combination of heated wellbores and VAPEX is known as the Thermal Solvent process. Again, a pair of horizontal wells is used, but the wells contain heating strings. This heat vaporizes the injected solvent. Solvent vapour moves to the oil interface at the edge of the vapour chamber and dissolves in the oil. The diluted oil is reduced in viscosity and flows down the edge of the vapour chamber to the production well. The vaporized solvent is driven out of the oil by the heat as it enters the production well.