Steam Flooding with Oxygen Injection, and Cyclic Steam Stimulation with Oxygen Injection
A process to recover heavy oil from a hydrocarbon reservoir, said process comprising injecting oxygen-containing gas and steam separately injected via separate wells into the reservoir to cause heated hydrocarbon fluids to flow more readily to a production well, wherein: (i) the hydrocarbon is heavy oil (API from 10 to 20; with some initial gas injectivity (ii) the ratio of oxygen/steam injectant gas is controlled in the range from 0.05 to 1.00 (v/v) (iii) the process uses Cyclic Steam Stimulation or Steam Flooding techniques and well geometry, with extra well(s) or a segregated zone to inject oxygen gas wherein the oxygen contact zone within the reservoir is less than substantially 50 metres long.
1 . A process to recover heavy oil from a hydrocarbon reservoir, said process comprising injecting oxygen-containing gas and steam separately injected via separate wells into the reservoir to cause heated hydrocarbon fluids to flow more readily to a production well, wherein:
(i) the hydrocarbon is heavy oil (API from about 10 to 20; with some initial gas injectivity
(ii) the ratio of oxygen/steam injectant gas is controlled substantially in the range from 0.05 to 1.00 (v/v)
(iii) the process uses Cyclic Steam Stimulation or Steam Flooding techniques and well geometry, with extra well(s) or a segregated zone to inject oxygen gas
wherein the oxygen contact zone within the reservoir is less than substantially 50 metres long.
2 . The process of claim 1 wherein a separate well or segregation is used for non-condensable gas produced by combustion.
3 . The process of claim 1 wherein the oxygen-containing gas has an oxygen content of 95 to 99.9% (v/v).
4 . The process of claim 3 wherein the oxygen-containing gas has an oxygen content of 95 to 97% (v/v).
5 . The process of claim 1 wherein the oxygen-containing gas is air.
6 . The process of claim 5 wherein the oxygen-containing gas is enriched air with an oxygen content of substantially 20 to 95% (v/v).
7 . The process of claim 1 wherein the oxygen injection well within the reservoir is less than substantially 50 metres long proximate a steam swept zone.
8 . The process of claim 1 whereby the oxygen-containing gas injection step is started only after a steam-swept zone is formed around the injection point.
9 . The process of claim 8 controlled by:
(i) adjusting steam and oxygen flow ratios to attain a target.
(ii) adjusting steam +oxygen flows to attain an energy rate target.
10 . The process of claim 2 or 9 wherein a separate produced gas removal well is used to minimize steam override to production wells.
11 . The process of claim 1 wherein oxygen/steam (v/v) ratios start at about 0.05 and ramp up to about 1.00 as the process matures.
12 . The process of claim 1 or 2 where the oxygen/steam (v/v) ratio is held between 0.4 and 0.7 and most preferably 0.35.
13 . The process of claim 1 wherein:
(i) the ratio of oxygen/steam (v/v) is between 0.4 and 0.7
(ii) the oxygen purity in the oxygen-containing gas is between 95 and 97% (v/v).
14 . The process of claim 1 or 7 further comprising an injector well (either a separate vertical well or the segregated portion of a well) having a maximum perforated zone (or zone with slotted liners) of less than substantially 50 m so that oxygen flux rates can be maximized.
15 . The process of claim 14 wherein Oxygen is injected proximate a steam-swept zone, whereby combustion of residual fuel in the reservoir is the source of energy for said combustion, said zone being preheated, at start-up, so spontaneous High Temperature Oxidation can occur.
16 . An improved Cyclic Steam Stimulation Enhanced Oil Recovery process to recover heavy oil comprising adding oxygen gas during a typical steam-injection cycle (the “huff”), the “soak” and “puff” cycles being similar to conventional CSS, wherein the injection of Oxygen provides extra energy from combustion of residual oil, for heavy oil recovery while creating CO 2 in the reservoir and removing produced CO 2 separately to better control the process.
17 . The process of claim 16 wherein an extra oxygen injection well is utilized.
18 . The process of claim 16 further comprising segregating oxygen injection within steam injection wells using separate tubing and a packer.
19 . The process of claim 16 wherein steam and oxygen are injected at separate times, as long as oxygen injection follows steam, so the reservoir is preheated for auto-ignition of High Temperature Oxidation combustion.
20 . The process of claim 16 wherein;
oxygen injection is segregated near the top of the injector well or
using a separate O 2 well, during the “huff” cycle, by injecting steam and oxygen;
and during the “puff” cycle removing produced gases (mainly CO 2 ) separately to better control the process.
21 . The process of claim 16 wherein the CSSOX process is the startup process for a SFOX process.
22 . An improved Steam Flooding (SFOX EOR) Enhanced Oil Recovery process to recover heavy oil, basically similar to a conventional SF process, the improvement comprising injection of oxygen gas continuously injected near (or at) the steam injector to provide an added source of energy from in situ combustion of residual fuels, said Steam and oxygen being injected in a vertical-well geometry, with producer/injector wells arranged in regular patterns.
23 . The process of claim 22 wherein separated wells are provided to remove non-condensable combustion gases.
24 . The process of claim 22 or 23 further comprising use of horizontal wells, especially for the more viscous heavy oils.
25 . The process of claim 1 , 16 or 22 wherein the pipe sizes for CSSOX or SFOX wells can be much smaller than for steam-only processes because oxygen carries about ten times the heat content, per unit volume.