Method of storing CO2

Abstract

The present invention relates to a method of storing CO.sub.2 in a geological formation, said method comprising (i) injecting a first composition comprising CO.sub.2 into said formation; and (ii) injecting a second composition comprising CO.sub.2 and at least one CO.sub.2 soluble polymer into said formation, wherein steps (i) and (ii) are performed separately and in any order and wherein said first and second compositions are different.

Claims

1. A method of storing CO.sub.2 in a geological formation, said method comprising: (i) injecting a first composition comprising CO.sub.2 into said formation; and (ii) injecting a second composition comprising CO.sub.2 and at least one CO.sub.2 soluble polymer having a weight average molecular weight of at least 10,000 g/mol into said formation, wherein steps (i) and (ii) are performed separately and in any order, and wherein said first and second compositions are different.

2. The method as claimed in claim 1, wherein the first composition and/or the second composition are injected at or near supercritical conditions, wherein “near supercritical conditions” means that the first and/or the second composition is at a pressure up to 10 bar less than its critical pressure and a temperature of up to 5° C. less that its critical temperature.

3. The method as claimed in claim 2, wherein the first composition is injected in a gas-like supercritical phase and the second composition is injected in a liquid-like supercritical phase.

4. The method as claimed in claim 1, wherein the first composition is injected in a gas-like supercritical phase and the second composition is injected in a liquid-like supercritical phase.

5. The method as claimed in claim 1, wherein the method comprises cycling alternately between step (i) and step (ii).

6. The method as claimed in claim 5, wherein the method comprises at least 2 cycles.

7. The method as claimed in claim 1, wherein each of steps (i) and (ii) is carried out for a time period of between one month and one year.

8. The method as claimed in claim 1, wherein step (i) is carried out for a time period of two months, and step (ii) is carried out for a time period of one month.

9. The method as claimed in claim 1, wherein the at least one CO.sub.2 soluble polymer is selected from the group consisting of polyolefins, polyurethanes, polyvinyl esters, polyvinyl ethers, silicon-containing polymers, fluoropolymers, perfluorocarbons, and polyalkylene glycols.

10. The method as claimed in claim 9, wherein the polyolefins are selected from the group consisting of polyethylene, polypropylene, polybutene, polydecene-1, and polyisobutylene, wherein the silicon-containing polymers are selected from the group consisting of polysiloxanes, wherein the fluoropolymers are selected from the group consisting of fluoroalkyl polymers, fluoroethers, polyperfluoroether and fluoroacrylates, and wherein the polyalkylene glycols are selected from the group consisting of polyethylene glycol and polypropylene glycol.

11. The method as claimed in claim 10, wherein the polysiloxanes are polydimethyl siloxane.

12. The method as claimed in claim 1, wherein the second composition comprises 0.1 to 50 wt % of the at least one CO.sub.2 soluble polymer.

13. The method as claimed in claim 1, wherein the second composition comprises 50-99.9 wt % of CO.sub.2.

14. The method as claimed in claim 1, wherein the first composition consists of CO.sub.2 and any unavoidable impurities.

15. The method as claimed in claim 1, wherein the viscosity of the second composition is 2-200 fold greater than that of the first composition.

16. The method of monitoring CO.sub.2 storage in a geological formation, said method comprising: (i) injecting a first composition comprising CO.sub.2 into said formation; (ii) injecting a second composition comprising CO.sub.2 and at least one CO.sub.2 soluble polymer having a weight average molecular weight of at least 10,000 g/mol into said formation; wherein steps (i) and (ii) are performed separately and in any order, and wherein said first and second compositions are different; and (iii) monitoring the stored CO.sub.2.

17. The method for at least one of the following: optimising storage, controlling of CO.sub.2, and monitoring CO.sub.2 storage in geological formations, said method comprising mixing a CO.sub.2 containing composition with at least one CO.sub.2 soluble polymer containing composition prior to injecting the composition into the formation, wherein the at least one CO.sub.2 soluble polymer has a weight average molecular weight of at least 10,000 g/mol.

Description

SUMMARY OF THE DRAWING

(1) The invention will be described in detail with reference to the attached FIGURE. It is to be understood that the drawing is designed solely for the purpose of illustration and is not intended as a definition of the limit of the invention for which reference should be made to the appended claims. It should be understood that the drawing is not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to schematically illustrate the structures and procedures described herein.

(2) FIG. 1 shows a schematic representation of an injection front formed according to the present invention. FIG. 1 shows a simulation of the injection of a composition comprising at least one CO.sub.2 soluble polymer and CO.sub.2 at or near supercritical conditions in a geological formation (1). The characteristics of injection parameters are cycled between at least two sets of injection parameters prior to injection of said composition, resulting in among others density and/or viscosity of said composition being varied during injection. The composition is injected via an injection well (5) and a conduit (6) into the geological formation (1). The geological formation can also be understood as the storage reservoir. The composition is injected under two different sets of injection conditions, gas-like and liquid-like, resulting in two different phases, one comprising at least one CO.sub.2 soluble polymer and one without (e.g. the first and second compositions according to the methods of the invention) When the injection parameters are cycled to give a higher viscosity and/or higher density said composition behaves more like a liquid. During injection of the liquid-like composition, the injected stream tends to occupy the lower areas (2) of the geological storage formation (2). Gas-like composition tends to occupy the upper areas (3) of the geological storage formation (2). The stabilised Compositional Swing Injection (CSI) front (4) is more uniform, and the storage capacity of the geological formation (1) increased. An observation well (7) can be used to observe changes in flow conditions in geological storage formation (2) over a period. Further a wellhead or down-hole monitoring of the composition (8) can be used in order to among others monitor and characterise the stabilized CSI front (4). Measuring the injection parameters such as temperature, pressure, and concentration of CO.sub.2 soluble polymer composition, will ensure the accuracy of injection operation and thus a stabilized CSI front.

(3) Having described preferred embodiments of the invention it will be apparent to those skilled in the art that other embodiments incorporating the concepts may be used. These and other examples of the invention illustrated above are intended by way of example only and the actual scope of the invention is to be determined from the following claims.