EXTRACTION OF HEAVY OIL AND BITUMEN USING VAPORIZED HYDROCARBON SOLVENTS

The huge natural resources present in the form of heavy oil and bitumen may be the principal source of fuel for human civilization in the coming century. However, due to very high viscosities of these crudes the use of conventional recovery techniques is not feasible. The viscosity decreases drastically with increase in temperature; this principle is utilized in thermal recovery processes like SAGD. Using long horizontal wells, very high production rates can be achieved in this process. However, steam processes suffer from energy inefficiency largely due to heat losses to the cap and base rock. This can be avoided if instead of steam, solvent is used to reduce viscosity. In the proposed process, "Vapex", vaporized hydrocarbon solvents are used to extract heavy oil and bitumen using the concept of gravity drainage. Hydrocarbon solvents, when present in sufficient concentration, causes deasphalting of these crudes. Although deasphalting improves the quality of the produced crude, the possibility of reservoir plugging due to asphaltene deposition is an important concern for using this process Experiments carried out in Hele-Shaw cells indicated higher extraction rates with deasphalting compared to that without deasphalting leading to the conclusion that asphaltene deposition may not be a constraint for the process. This was confirmed in experiments carried out in scaled packed model. The experimental results showed that the flow rates achieved in the porous media are higher than those obtained by scaling up the results of Hele-Shaw cell experiments carried.out under identical conditions of temperature and pressure. This is due to the extended interfacial contact, capillary imbibition, surface renewal and transient mass transfer at the interface. Production rates predicted from these experimental results are attractive for field operations