Pentane-hexane solvent in situ recovery of heavy oil
An integrated thermal recovery process using a solvent of a pentane or hexane or both as an additive to, or sole component of, a gravity-dominated process for recovering bitumen or heavy oil from a reservoir. A pentane-hexane specific solvent fraction is extracted at surface from a diluent stream. That pentane-hexane solvent fraction is then injected into the reservoir as part of a gravity-dominated recovery process within the reservoir, and when that solvent fraction is subsequently produced as part of the oil or bitumen blend, it is allowed to remain within the blend to enhance the subsequent blend treating and transportation steps. Meanwhile, the remainder of the diluent from which the solvent stream had been extracted is utilized at surface as a blending stream to serve as an aid in treating of produced fluids and also to serve as a means of rendering the bitumen or heavy oil stream pipelineable.
1. A method of recovering heavy oil or bitumen from a reservoir under a gravity-dominated recovery process comprising:
fractionating a diluent comprising pentane and hexane into fractions comprising a pentane-hexane fraction and an abridged diluent fraction;
preparing a pentane-hexane solvent comprising the pentane-hexane fraction;
injecting the pentane-hexane solvent into the reservoir as part of the gravity-dominated recovery process;
producing heavy oil or bitumen and recovered pentane-hexane solvent from the reservoir, said heavy oil or bitumen and said recovered pentane-hexane solvent together comprising a produced heavy oil or bitumen blend; and
combining the abridged diluent fraction and the produced heavy oil or bitumen blend to provide a blended oil.
2. The method of claim 1 , wherein the fractionating additionally provides a light ends fraction.
3. The method of claim 2 , wherein the light ends fraction and the pentane-hexane fraction are combined to provide the pentane-hexane solvent.
4. The method of claim 1 , further comprising collecting hydrocarbons containing pentanes and hexanes from the heavy oil or bitumen to provide the pentane-hexane solvent.
5. The method of claim 4 , wherein the hydrocarbons are collected from a blended oil tank, containing heavy oil or bitumen.
6. The method of claim 4 , wherein the hydrocarbons are collected from an emulsion treater.
7. The method of claim 1 , wherein the pentane-hexane solvent is injected with steam.
8. The method of claim 7 , wherein the pentane-hexane solvent is between 2 wt % and 20 wt % of the steam.
9. The method of claim 7 , wherein the pentane-hexane solvent is greater than 50 percent pentane or hexane or mixtures thereof.
10. The method of claim 9 , wherein at least 50 percent of the injected pentane or hexane or mixtures thereof is recovered in the heavy oil or bitumen and said recovered pentane-hexane solvent.
11. The method of claim 9 , wherein the pentane-hexane solvent is greater than 80 percent pentane or hexane or mixtures thereof.
12. The method of claim 11 , wherein at least 80 percent of the injected pentane or hexane or mixtures thereof is recovered in the heavy oil or bitumen and said recovered pentane-hexane solvent.