VAPEX, Warm VAPEX and Hybrid VAPEX - The State of Enhanced Oil Recovery for In Situ Heavy Oils in Canada

Abstract

Abstract VAPEX, warm VAPEX and hybrid VAPEX rely on a combination of mass and heat transfer to reduce the heavy oil's viscosity sufficiently for it to flow via gravity drainage to the production well. In the last couple of years, many combinations of vapour extraction and steam-assisted gravity drainage have been proposed for the in situ recovery of heavy oil and bitumen. The question still remains; which technique (VAPEX, warm VAPEX, hybrid VAPEX and/or SAGD) produces more oil with better sweep efficiencies? This paper attempts to define and compare the various enhanced heavy oil recovery techniques, including different solvent choices. The pore-scale mechanisms are identified, key advantages and disadvantages given and the results from simple laboratory experiments are compared to better direct he investigation into the in situ recovery of heavy oil and bitumen. The solvents and solvent mixtures (in combination with non-condensable gases and/or steam) are analyzed based on their physical properties at laboratory and reservoir conditions and the role they play at the pore-scale. Introduction Canada's heavy oil reserves are found in western Canada, mainly in Alberta and Saskatchewan. The geographic location of the reserve is indicative of the quality of the oil based on geology. The oil deposit is generally shallower and the oil's viscosity higher (with a lower ºAPI density) the further east and north it is found. The oil found at the surface and below, is in thin shallow sandstone and unconsolidated sand. The porosity ranges from 26 – 32% and the permeability from 1,200 – 7,500 mD(1). The current producing fields are found at the surface to a maximum depth of 800 – 1,000 m, have a reservoir temperature from 4 to 40 ºC and the oil's viscosity is from 500 cP to greater than one million. Cold production of heavy oil is possible, but production rates are low. Sand is often produced with the oil (not necessarily a disadvantage), water cuts are generally high and recovery factors marginal. Cold production is still a logical choice for fields with lower viscosity oil. Otherwise, in situ heavy oil and bitumen can be produced using enhanced oil recovery techniques (EOR). Canada is the world leader in developing EOR techniques for heavy oil production. New techniques and a combination of techniques are constantly being investigated and compared where the ultimate goal is to maximize oil recovery. Steam-assisted gravity drainage (SAGD), cyclic steam stimulation (CSS), in situ combustion and vapour extraction (VAPEX) are all EOR possibilities. Combinations of VAPEX and SAGD are also being explored and reexamined. This paper strives to give the history of VAPEX, warm VAPEX and hybrid VAPEX, and then focuses on comparing and analyzing the different methods, highlighting advantages and disadvantages, as well as pore-scale mechanisms in VAPEX. The History of VAPEX, Warm VAPEX and Hybrid VAPEX VAPEX or vapour extraction is the process of injecting a solvent into a heavy oil reservoir (through an upper horizontal well) to reduce the viscosity of the heavy oil via mass transfer.