System and method for disinfecting and removing biological material from water to be injected in an underwater injection well

Abstract

A system for disinfecting and removing biological material from water to be injected into an injection well in a water body is described; the system includes: at least one apparatus for the gravitational precipitation of particles from water, which is connected, in terms of fluid, to a source of untreated water and to the injection well; and an apparatus for the addition of an oxidant for the disinfection of water, which is connected in terms of fluid to the apparatus for the gravitational precipitation of particles, a source of untreated water and to the injection well such that the apparatus for the gravitational precipitation of particles is positioned downstream relative to the apparatus for the addition of an oxidant for disinfection. The disclosure also relates to a method for disinfecting and removal of biological material from injection water.

Claims

1. A system for removing biological material from untreated water for subsequent injection into an injection well under a body of water, the system comprising: a first apparatus configured to add an oxidant to the untreated water to form a treated water, wherein the oxidant is an oxidizing biocide selected from chlorine, dioxygen, ozone, hydrogen peroxide, hypochlorite, chlorine dioxide, or a combination thereof; and a second apparatus configured to gravitationally precipitate the biological material from the treated water, wherein the second apparatus is configured to gravitationally precipitate the biological material by flowing the treated water within a closed space from a lower height to a higher height at a climbing speed that is less than a rate of precipitation of the biological material from the treated water, wherein the second apparatus is fluidly connected to and positioned downstream relative to the first apparatus, wherein the first apparatus is fluidly connected to a source of the untreated water for subsequent injection into the injection well, and wherein the second apparatus is fluidly connected to the injection well under the body of water.

2. The system of claim 1, wherein the oxidant comprises chlorine.

3. The system of claim 2, wherein the first apparatus is configured to add the chlorine in a solid or semisolid state.

4. The system of claim 2 or 3, wherein the first apparatus includes an electrolytic cell that electrolytically produces the chlorine from sea water.

5. The system of claim 2, wherein the first apparatus is configured to add the chlorine from a liquid state.

6. The system of claim 2, wherein the system further comprises a hydroxyl cell that electrolytically produces free hydroxyl radicals, wherein the hydroxyl cell is fluidly connected to the second apparatus, the first apparatus, and to the injection well.

7. The system of claim 2, wherein the system further comprises a mixed oxidant cell that electrolytically produces mixed oxidants, wherein the mixed oxidant cell is fluidly connected to the second apparatus, to the first apparatus and to the injection well.

8. A method of removing biological material from untreated water to be injected into an injection well located under a body of water, the method comprising: (a) adding an oxidant to the untreated water comprising said biological material to form a treated water comprising a treated biological material, wherein the oxidant is an oxidizing biocide selected from chlorine, dioxygen, ozone, hydrogen peroxide, hypochlorite, chlorine dioxide, or a combination thereof to decompose a cell structure of the biological material and thus increase a specific gravity thereof, such that the treated biological material has the increased specific gravity relative to the specific gravity of the biological material in the untreated water; (b) after (a), gravitationally precipitating the treated biological material with the increased specific gravity in the treated water by flowing the treated water within a closed space from a lower height to a higher height at a climbing speed less than a rate precipitation of the treated biological material; and (c) after (b), injecting said clean water into an injection well located under the body of water.

9. The method of claim 8, wherein adding said oxidant comprises adding chlorine.

10. The method of claim 9, wherein adding chlorine, includes adding chlorine from a solid or semisolid state.

11. The method of claim 9 or 10, wherein adding chlorine comprises producing chlorine by means of an electrolytic cell.

12. The method of claim 9, wherein adding chlorine comprises adding chlorine from a liquid state.

13. The method of claim 8, further comprising providing the system with a hydroxyl cell that electrolytically produces free hydroxyl radicals, and fluidly connecting the hydroxyl cell to the first apparatus to the second apparatus, to a source of the untreated water, and to the injection well.

14. The method of claim 8, wherein the method further includes providing the system with a mixed oxidant cell that electrolytically produces mixed oxidants and fluidly connecting the mixed oxidant cell to the first apparatus, the second apparatus, a source of the untreated water, and the injection well.

15. A system for removing biological material from untreated water for subsequent injection into an injection well under a body of water, the system comprising: an oxidant injection device fluidly connected to a source of the untreated water, wherein the oxidant injection device is configured to add an oxidant to the untreated water to form a treated water, wherein the oxidant is an oxidizing biocide selected from chlorine, dioxygen, ozone, hydrogen peroxide, hypochlorite, chlorine dioxide, or a combination thereof, wherein the oxidant injection device comprises (i) a container holding the oxidant in a liquid, solid, or semisolid state, or (ii) an electrolytic cell; and a precipitation container configured to gravitationally precipitate the biological material from the treated water, wherein the container includes an enclosed space and an inlet to the enclosed space proximal a lower end of the enclosed space, wherein an outlet is disposed within the enclosed space vertically above the inlet, wherein the container is configured to gravitationally precipitate the biological material by flowing the treated water through the inlet and upward within the enclosed space to the outlet at a climbing speed that is less than a rate of precipitation of the biological material from the treated water; wherein the container is fluidly connected to and positioned downstream of the oxidant injection device, and wherein the container is fluidly connected to the injection well under the body of water.

16. The system of claim 15, further comprising a hydroxyl cell configured to electrolytically produce free hydroxyl radicals, wherein the hydroxyl cell is fluidly connected to the precipitation container, the oxidant injection device, and to the injection well.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In what follows, exemplary embodiments are described with reference to the accompanying drawings, in which:

(2) FIG. 1 shows a first embodiment of the present disclosure, viewed from above; FIG. 1 shows schematically and in section a closed space with arrows indicating the flow of the water;

(3) FIG. 2 shows a second embodiment of the present disclosure, viewed from above;

(4) FIG. 3 shows a third embodiment of the present disclosure, viewed from above; and

(5) FIG. 4 shows a fourth embodiment of the present disclosure, viewed from above;

(6) The figures are shown in a schematic and simplified manner and elements which are not central to the disclosure and/or elements that, to a person skilled in the art, will be known parts of the system may have been omitted from the figures for clarity and conciseness. In the figures, the direction of the water flow is indicated by straight arrows.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

(7) FIG. 1 shows schematically and in section a closed space with arrows indicating the flow of the water. In FIG. 1, the reference numeral 1 identifies a pipe connection extending from the seabed 2 down to a petroleum reservoir, not shown, in the ground. A wellhead 4 is placed on the seabed 2 and is connected to the pipe connection 1. Surrounding the wellhead 4, and above it, are arranged at least one water treatment apparatus 6, a pump module 8 and an energy and control module 10. Other necessary equipment packages, not shown, in accordance with the prior art known per se are also placed at the wellhead 4. Said apparatuses and modules 4 to 10 and also equipment packages, not shown, are surrounded by plate-shaped covers 12 forming together with the seabed 2 a closed space 14. The covers 12 may include hatches, not shown, for access to the space 14. At the lower portion of the space 14 are arranged openings 16 where untreated water from the surroundings may enter. The water then flows upwards in the space 14 at a flow rate, which, because of the cross-sectional area of the space, is lower than the rate of precipitation of the smallest particle which is desirably to be precipitated from the water. The particles in the water are not shown in the figure. The precipitated particles, not shown, settle on the seabed 2 and on apparatus parts 4, 8, 10, from which, if necessary, they may be flushed away whenever necessary. After the water has flown upwards to the upper portion of the space 14 and has become essentially free of undesired particles, the water enters the inlet opening of a pump pipe 18, from where the water flows via the pump module 8 and water treatment apparatus 6 through the pipe connection 1 to the petroleum reservoir, not shown. In the space 14 there is placed copper 20 or other organism repellent or toxic material, for example in the form, of a copper-containing material which is in contact with at least part of the water flowing through the space 14. The purpose of the copper 20 is to make the space less attractive to living organisms. In a further exemplary embodiment, not shown, a channel for the inflow of water into the space 14 may open into the lower portion of the space 14.

(8) In what follows, the reference numeral 1 indicates a system in accordance with the present disclosure.

(9) FIG. 1 shows a first embodiment of the present disclosure, viewed from above. The system 1 is placed on a sea floor in a water body 2 in the vicinity of a platform 5. Untreated sea water is guided into a water-intake device 14, the water-intake device 14 being connected to a coupling device 51 on the platform 5 via a control cable 52. The control cable 52 delivers electric power and/or communication signals to and/or from the water-intake device 14. Various valves and pumps for controlling the intake and outlet of water into and from the water-intake device 14 are not shown. Said intake and outlet can be controlled by means of a control unit, not shown, placed on the platform 5 and/or at the water-intake device 14 on the sea floor.

(10) In the water-intake device 14, the untreated sea water is further supplied with chlorous water from a container 13, which adds chlorine from a liquid state to the injection water. In the exemplary embodiment shown, the container 13 is arranged as a refillable, volumetric, flexible storage tank as described in the Norwegian patent NO 331478. The container 13 is connected to the coupling device 51 of the platform 5 via a control cable 54. Valves and pumps, not shown, for dosing liquid chlorine into the sea water in the water-intake device 14 may thereby be controlled by means of a control unit not shown. The control unit, not shown, may be on the platform 5 and/or on the sea floor together with the container 13. The container 13 is further provided with a valve, not shown, for refilling chlorine from an external source not shown, as described in said Norwegian patent NO 331478. Said valves of the container 13 may further have been placed in signal communication with a sensor, not shown, for measuring the chlorine content of the water, so that a desired amount of chlorine may be maintained in the water.

(11) The chlorinated water is further carried through a supply line 18 into an apparatus 12 for the gravitational precipitation of particles. The apparatus 12 is shown in the form of a container which is known from the patent publication WO 2007/035106 A1. The chlorinated sea water is carried into the container 12 via an inlet, not shown, and is allowed to flow slowly towards an outlet, not shown, of the container 12. The flow rate in the container 12 is sufficiently low for particles of a greater specific weight than water to settle onto the bottom of the container 12. According to the prior art, it has been difficult to precipitate biological material in such a container 12 because of the biological material basically having a specific gravity which is of the same order as that of the sea water which is to be cleaned. According to the present disclosure, the sea water is chlorinated upstream of the container 12, whereby the cell structure of the biological material in the water collapses and the specific gravity of the biological material increases. Thereby the gravitational precipitation of biological material becomes far more effective. The time it takes from when the water is carried into said inlet of the container 12 until it leaves the container 12 from said outlet may generally be in the order of 30 minutes and up to one hour and, in some embodiments, up to several hours. The container 12 for the gravitational precipitation of particles is connected to the platform 5 via a control cable 55. Electric power and communication signals transferred via the control cable 55 may be used for controlling valves and pumps, not shown, connected to the container 12 for the gravitational precipitation of particles by means of a control unit not shown. The control unit may be the same as that mentioned above, or it may be a separate control unit.

(12) From the container 12 for the gravitational precipitation of particles, the water is carried through the supply line 18 to a high-pressure injection pump 31 and further into an injection well 3. The injection pump 31 is connected to the coupling device 51 of the platform 5 via a control cable 57, and the injection pump 31 may be controlled by means of a control unit not shown.

(13) FIG. 2 shows an alternative embodiment of the present disclosure. An apparatus 13 for the addition of chlorine to the injection water is provided as an electrolytic cell, hereinafter referred to as a chlorine cell 13. The chlorine cell 13 is connected to the coupling device 51 of the platform 5 via the control cable 54. The amount of sea water carried into and out of the chlorine cell 13 can thereby be controlled by means of valves and pumps, not shown. Chlorous water is carried from the chlorine cell 13 via a dosage line 19 into the water-intake device 14 in the same way as that mentioned above.

(14) Downstream of the apparatus 12 for the gravitational precipitation of particles, the system 1 in the embodiment shown in FIG. 2 is further provided with an apparatus 15 for the electrolytic production of free hydroxyl radicals, referred to, in what follows, as the hydroxyl cell 15. The hydroxyl cell 15 is connected to the coupling device 51 of the platform 5 via a control cable 56, whereby the amount of water entering and exiting the hydroxyl cell 15 via the supply line 18 may be controlled by means of valves and pumps, not shown, connected to a control unit not shown. The cleaned water is carried onwards to the injection pump 31 and into the injection well 3.

(15) In FIG. 3, yet another alternative embodiment of the present disclosure is shown. Here, an apparatus 13 for the addition of chlorine to the injection water is provided as a container 13 for dosing chlorine from a solid or semisolid state. Untreated sea water is carried into the container 13 so that the sea water gets into contact with chlorine in a solid or semisolid state, whereby chlorine is dosed gradually into the injection water. The apparatus 13 for dosing chlorine from a solid or semisolid state into the injection water is connected to the coupling device 51 of the platform 5 via the control cable 54 in the same way as that mentioned above. Pumps and valves, not shown, may be controlled by a control unit not shown.

(16) Downstream of the apparatus 12 for the gravitational precipitation of particles from the injection water, the system 1 in the embodiment shown in FIG. 3 is provided with an apparatus 17 for the electrolytic production of mixed oxidants, referred to, in what follows, as the oxidant cell 17. The oxidant cell 17 is connected to the coupling device 51 of the platform 5 via the control cable 56, and the amount of water entering and exiting the oxidant cell 17 may thereby be controlled in a manner corresponding to that described above.

(17) FIG. 4 shows a further embodiment of the present disclosure. The entire stream of injection water is carried directly into a chlorine cell 13. The chlorinated water is carried onwards to the apparatus 12 for the gravitational precipitation of particles. By means of sensors not shown, it will be possible to keep control of the chlorine content of the water at both the inlet and the outlet of the apparatus 12 for the gravitational precipitation of particles. The amount of chlorine that is dosed into the injection water may thus be small enough for all the chlorine to have time to react completely. The injection water downstream of the apparatus 12 for the gravitational precipitation of particles will thereby be free of chlorine. The hydroxyl cell 15 will be able to eliminate what might be left of biological material in the injection water flow in case the amount of added chlorine should be too small. In the embodiment shown, the system is further provided with apparatus 16 provided with a filtering membrane for removing any remaining particles of different salts and minerals in the injection water flow. The filtering membrane, which would have been damaged by chlorous water, may be of a type as described in the Norwegian patent application NO 20101192.

(18) It will be understood that apparatuses included in the various embodiments may be combined into further embodiments not shown.

(19) The different control cables 52, 54, 55, 56, 57, 58 are arranged to transfer electric power and/or communication signals to the above-mentioned different apparatuses connected to the system 1. Control units, not shown, for controlling said valves and pumps, not shown, connected to the different apparatuses may be placed on the platform and/or on the sea floor at the different apparatuses. The control cables 52, 54, 55, 56, 57, 58 may be arranged for two-way communication, so that information on the state of the system 1 may also be fed back to the platform 5.

(20) The system 1 may be provided with a great number of couplings, valves, pumps, sensors and so on, which will be known to a person skilled in the art, therefore variations of the above embodiments will be apparent to the skilled person. Embodiments of the present disclosure have been described with particular reference to the examples illustrated. While specific examples are shown in the drawings and are herein described in detail, it should be understood, however, that the drawings and detailed description are not intended to limit the disclosure to the particular form disclosed. It will be appreciated that variations and modifications may be made to the examples described within the scope of the present disclosure.