CARBON DIOXIDE GAS MIXTURE PROCESSING WITH STEAM ASSISTED OIL RECOVERY

Abstract

Methods and apparatus relate to processing flue gas from oxy-fuel combustion. Steam generated without contact of the steam with the flue gas combines with the flue gas for injection into a formation to facilitate oil recovery from the formation. Fluids produced include the oil and carbon dioxide with a lower concentration of oxygen than present in the flue gas that is injected.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

None

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

None

FIELD OF THE INVENTION

Embodiments of the invention relate to methods and systems for processing carbon dioxide in flue gas from oxy-fuel combustion utilizing steam assisted oil recovery.

BACKGROUND OF THE INVENTION

Oxy-fuel combustion refers to burning of fuel in oxygen (e.g., 95% pure oxygen) instead of air to reduce amount of nitrogen in resulting flue gas. The flue gas from the oxy-fuel combustion thus contains carbon dioxide and water vapor, which can be removed if condensed through cooling. The oxy-fuel combustion facilitates carbon dioxide capture since the flue gas is almost pure carbon dioxide with trace amounts of impurities, such as oxygen (e.g., about 0.1-2 volume percent) remaining due to equilibrium constraints as well as local mixing conditions during combustion.

The oxygen in the carbon dioxide makes transportation of the carbon dioxide to a sequestration site problematic since the oxygen causes corrosion. Common carbon dioxide quality specifications for pipeline transport require oxygen content to be below 0.001 by volume. Cryogenic distillation provides one option for removing the oxygen but requires additional expense and results in loss of 7-10 percent of the carbon dioxide.

Alternate approaches utilize the flue gas from the oxy-fuel combustion. For example, injecting the flue gas into reservoirs of natural gas helps displace the natural gas. However, gas phase interactions of the flue gas in the reservoirs and the interactions not occurring at where the reservoir is being heated limits any possible oxygen removal from the carbon dioxide.

Therefore, a need exists for improved methods and systems for processing carbon dioxide for capture.

SUMMARY OF THE INVENTION

In one embodiment, a method includes forming a mixture of flue gas from oxy-fuel combustion and steam generated prior to being mixed with the flue gas. The flue gas contains carbon dioxide with an initial concentration of oxygen that is at least 0.1 volume percent. Injecting the mixture into a subterranean formation heats oil in the formation and reacts with the oil at least some of the oxygen that is from the flue gas and is dissolved in liquid condensate of the steam. The method further includes recovering fluids including the oil that is heated and carbon dioxide from the flue gas and separating the fluids recovered to isolate from a liquid phase the carbon dioxide containing less than the initial concentration of oxygen for transporting the carbon dioxide to a sequestration site.

According to one embodiment, a method includes producing flue gas from oxy-fuel combustion, generating steam without contact of the steam with the flue gas, and introducing the steam into the flue gas to form a mixture. The flue gas contains carbon dioxide with quantities of oxygen greater than a transport specification. In addition, the method includes injecting the mixture into a subterranean formation for heating oil in the formation, recovering fluids including the oil that is heated and the carbon dioxide from the flue gas, and separating the fluids into liquids and vapors. The vapors formed of the carbon dioxide meet the transport specification due to removal of at least some of the oxygen by oxidation of the oil upon the oxygen being dissolved in condensate of the steam for liquid phase reactions at temperatures elevated by the steam. The method further includes transporting to a sequestration site the carbon dioxide obtained by the separating.

For one embodiment, a system includes a supply of flue gas from an oxy-fuel combustion chamber, a source of steam generated without contact of the steam with the flue gas, and an injection well disposed in a subterranean formation containing oil. The injection well couples in fluid communication with the supply of the flue gas and the source of the steam. A vapor-liquid separator of the system receives produced fluids heated by the steam. The vapor-liquid separator also outputs carbon dioxide that is in the produced fluids from the flue gas and is processed by liquid phase reactions between the oil heated by the steam and at least some oxygen that is from the flue gas and is dissolved in condensate of the steam.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with further advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings.

FIG. 1 is a schematic of a production system for both purification of carbon dioxide in flue gas and steam assisted oil recovery, according to one embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the invention relate to methods and systems for processing flue gas from oxy-fuel combustion. Steam generated without contact of the steam with the flue gas combines with the flue gas for injection into a formation to facilitate oil recovery from the formation. Fluids produced include the oil and carbon dioxide with a lower concentration of oxygen than present in the flue gas that is injected.

FIG. 1 illustrates a system with an injection well 101 and a production well 102 that traverse through an earth formation 103 containing petroleum products, such as heavy oil or bitumen. The system further includes a steam generator 104 to supply a flow of steam 105 to the injection well 101. The steam generator 104 and/or a separate heating unit 106 produce flue gas 107 from oxy-fuel combustion.

The oxy-fuel combustion produces the flue gas 107 containing carbon dioxide with at least 0.1 volume percent oxygen as a result of burning fuel in oxygen, such as at least about 95% by volume pure oxygen separated from air. The carbon dioxide may make up by volume at least about 85%, at least about 90%, or at least about 95% of the flue gas 107. Sources for the fuel include coal, petroleum coke, asphaltenes, methane, natural gas and hydrogen. To limit resulting flame temperatures to levels common during conventional combustion and within thermal thresholds, some cooled combustion gases may circulate back and be injected into a combustion chamber used for the oxy-fuel combustion.

For some embodiments, a burner heats a boiler within the steam generator 104 for making the steam 105 without initial contact of the flue gas 107 with the steam 105 in the steam generator 104 since an inside of the boiler is sealed from the burner, which may define the chamber for the oxy-fuel combustion. The flue gas 107 combines with the steam 105 to form a mixture after the steam 105 is generated. The mixture passes into the injection well 101 upon introducing the flue gas 107 into the steam 105 between the steam generator 104 and the injection well 101. The mixture may in some embodiments further contain a solvent for the products added to help mobilize the products, which are more viscous than the solvent. Examples of the solvent introduced into the mixture include hydrocarbons, such as at least one of propane, butane, pentane, hexane, heptane, naphtha, natural gas liquids and natural gas condensate.

In operation, the mixture makes the petroleum products mobile enough to enable or facilitate recovery with, for example, the production well 102. For some embodiments, the injection well 101 includes a horizontal borehole portion that is disposed above (e.g., 0 to 6 meters above) and parallel to a horizontal borehole portion of the production well 102. While shown in an exemplary steam assisted gravity drainage (SAGD) well pair orientation, some embodiments utilize other configurations of the injection well 101 and the production well 102, which may be combined with the injection well 101 or arranged crosswise relative to the injection well 101, for example.

A vapor chamber develops in the formation 103 and grows as the products are recovered. Walls of the vapor chamber form an interface with the products where the steam 105 condenses transferring heat to the products that then drain to the production well 102. Since the flue gas 107 containing the oxygen is injected into the vapor chamber during development of the chamber, the oxygen contacts this condensate of the steam 105 and is dissolved in the condensate enabling both the condensate to carry oxygen into the products and liquid phase reaction of the oxygen with the products. For some embodiments, effective removal of the oxygen from the carbon dioxide in the flue gas 107 relies on the reactions being in liquid phase compared to inefficient gas contact of the oxygen with the products.

In some embodiments, this oxidation of the products further depends on temperature at which the oxygen contacts the products since oxygen uptake by the products increases with rising temperature. The reactions for some embodiments occur at temperatures that are elevated by the steam 105 and may be above about 100° C., above about 150° C. or above about 200° C. Injection of the flue gas 107 through a separate well and outside of the vapor chamber formed by the steam 105 heating the products tends to keep the oxygen in gas phase and insulated from thermal heating by the steam 105 due to physical separation of the oxygen from the condensate. Likewise, injection of the flue gas 107 after stopping injection of the steam 105 prevents ability of the oxygen to be dissolved in the condensate and carried into the products at as high a temperature as possible. While helpful for processing the carbon dioxide in the flue gas 107, the oxidation of the products lacks influence on recovery due to only trace amounts of the oxygen in the flue gas 107.

As a benefit to recovery, the carbon dioxide from the flue gas 107 also dissolves into the products reducing viscosity of the products to facility production. The formation 103 retains some amount of the carbon dioxide from the flue gas 107. Pore space opened from one barrel of produced oil stores about 8 kilograms of the carbon dioxide. Unlike loss of carbon dioxide associated with cleaning of the flue gas 107 above ground to remove oxygen, the carbon dioxide being held in the formation 103 remains sequestered without requiring any additional treatment to be captured.

Fluid recovered from the production well 102 enters into a separator 110 for separation of a liquid phase 111 from a vapor phase 112. The liquid phase 111 includes the petroleum products and water, which may be separated from the products and recycled along with any solvent removed from the products. The carbon dioxide from the flue gas 107 forms the vapor phase 112 and may make up by volume at least about 90%, or at least about 95% of the vapor phase 112. Lack of substantial quantities of nitrogen in the flue gas 107 due to the oxy-fuel combustion limits nitrogen amounts in the vapor phase 112 ensuring that the carbon dioxide therein remains concentrated for desired capture and sequestration.

Due to the oxidation reactions discussed herein, the vapor phase 112 contains a lower concentration of the oxygen than is present in the flue gas 107 prior to introduction into the injection well 101. In some embodiments, the flue gas 107 with the at least 0.1 volume percent oxygen before being introduced into the injection well 101 prevents the flue gas 107 from meeting transport specifications. For example, oxygen content of above 0.001% by volume in the flue gas 107 as produced from the oxy-fuel combustion may reduce to below 0.001% by volume in the vapor phase 112 and thereby be below the transport specifications.

This reduction in oxygen content processes the carbon dioxide to enable transporting the carbon dioxide without further oxygen removal from the vapor phase 112. For some embodiments, transport of the carbon dioxide includes compressing the vapor phase 112 that is then passed through a pipeline. The pipeline may carry the carbon dioxide to a sequestration facility such as a geologic reservoir distant from the formation 103 in which the products are recovered.

In some embodiments, injection of the flue gas 107 from the oxy-fuel combustion into a depleted hydrocarbon reservoir passes the flue gas 107 into contact with unrecovered petroleum products that react with the oxygen from the flue gas 107. Such oxidation scrubs oxygen from the flue gas 107 leaving the carbon dioxide that may be subsequently recovered for transporting even though no hydrocarbons are also produced while recovering the carbon dioxide. If only such scrubbing of the flue gas 107 and not recovering of the petroleum products is desired, some embodiments may inject the flue gas 107 without mixing the flue gas 107 with the steam 105.

The preferred embodiment of the present invention has been disclosed and illustrated. However, the invention is intended to be as broad as defined in the claims below. Those skilled in the art may be able to study the preferred embodiments and identify other ways to practice the invention that are not exactly as described herein. It is the intent of the inventors that variations and equivalents of the invention are within the scope of the claims below and the description, abstract and drawings are not to be used to limit the scope of the invention.

Claims

1. A method, comprising:

forming a mixture of flue gas from oxy-fuel combustion and steam generated prior to being mixed with the flue gas, wherein the flue gas contains carbon dioxide with an initial concentration of oxygen that is at least 0.1 volume percent;

injecting the mixture into a subterranean formation for heating oil in the formation and reacting with the oil at least some of the oxygen that is from the flue gas and is dissolved in liquid condensate of the steam;

recovering fluids including the oil that is heated and the carbon dioxide from the flue gas;

separating the fluids recovered to isolate from a liquid phase the carbon dioxide containing less than the initial concentration of oxygen; and

transporting to a sequestration site the carbon dioxide that is separated from the liquid phase.

2. The method according to claim 1, further comprising heating a boiler for generating the steam using the oxy-fuel combustion.

3. The method according to claim 1, wherein the oxy-fuel combustion is part of a heating unit separate from a steam generator that makes the steam.

4. The method according to claim 1, wherein the separating the fluids removes the liquid phase from a vapor phase that is at least 95% carbon dioxide by volume.

5. The method according to claim 1, wherein the separating the fluids removes the liquid phase from a vapor phase that is at least 95% carbon dioxide by volume with oxygen content of less than 0.001% by volume.

6. The method according to claim 1, wherein the reacting of the oil with at least some of the oxygen is at a temperature of at least 100° C.

7. The method according to claim 1, wherein the reacting of the oil with at least some of the oxygen is at a temperature of at least 200° C.

8. The method according to claim 1, wherein at least 90% by volume of the flue gas is the carbon dioxide.

9. The method according to claim 1, further comprising adding to the mixture a hydrocarbon-containing solvent for the oil being produced and having a lower viscosity than the oil being produced.

10. The method according to claim 1, wherein the transporting includes passing the carbon dioxide through a pipeline.

11. The method according to claim 1, wherein the injecting is through a first wellbore spaced from a second wellbore located deeper in the formation than the first wellbore and through which the recovering occurs.

12. A method, comprising:

producing flue gas from oxy-fuel combustion, wherein the flue gas contains carbon dioxide with quantities of oxygen greater than a transport specification;

generating steam without contact of the steam with the flue gas;

introducing the steam into the flue gas to form a mixture;

injecting the mixture into a formation for heating oil in the formation;

recovering fluids including the oil that is heated and the carbon dioxide from the flue gas;

separating the fluids into liquids and vapors, which are formed of the carbon dioxide and meet the transport specification due to removal of at least some of the oxygen by oxidation of the oil upon the oxygen being dissolved in condensate of the steam for liquid phase reactions at temperatures elevated by the steam; and

transporting to a sequestration site the carbon dioxide obtained by the separating.

13. The method according to claim 12, wherein the transportation specification is oxygen content of less than 0.001% by volume.

14. The method according to claim 12, wherein the separating the fluids removes the liquids from the vapors that are at least 95% carbon dioxide by volume.

15. The method according to claim 12, wherein the oxy-fuel combustion is used to heat a boiler for the generating of the steam.

16. The method according to claim 12, wherein at least 90% by volume of the flue gas is the carbon dioxide and at least 0.1% by volume of the flue gas is the oxygen.

17. The method according to claim 12, wherein the transporting includes passing the carbon dioxide through a pipeline.

18. The method according to claim 12, wherein the elevated temperatures are above 150° C.

19. A system, comprising:

a supply of flue gas from an oxy-fuel combustion chamber;

a source of steam generated without contact of the steam with the flue gas;

an injection well disposed in a subterranean formation containing oil, wherein the injection well is coupled in fluid communication with the supply of the flue gas and the source of the steam; and

a vapor-liquid separator coupled to receive produced fluids heated by the steam and output carbon dioxide from the flue gas, wherein the carbon dioxide in the produced fluids is processed by liquid phase reactions between the oil heated by the steam and at least some oxygen that is from the flue gas and is dissolved in condensate of the steam.

20. The system according to claim 19, wherein the oxy-fuel combustion chamber is coupled to heat a boiler for generating the steam.