COMBINED AERATION AND NANOBUBBLE DELIVERY SYSTEM FOR WATER TREATMENT AND CARBON CAPTURE

Abstract

A combined aeration system supplemented with a nanobubble delivery system to capture and store carbon, typically in the form of carbon dioxide (CO.sub.2) (i.e., “carbon capture”). Produced water is generated as a byproduct of oil and gas extraction. Carbon dioxide is introduced to produced water in the form of nanobubbles. Aeration is used as a pre-treatment to oxidation and to preserve disinfection in produced water, and also reduces the higher temperature of produced water from the wellhead This reduction in temperature allows more carbon dioxide to be absorbed by the produced water, and the absorption process is accelerated by adding carbon dioxide to the airstream used in the aeration process.

Claims

1. A method for storage of carbon, comprising: infusing a fluid stream with carbon dioxide in the form of nanobubbles; and storing the infused fluid stream in one or more of the following: a storage tank, a fluid treatment pit, or an underground formation or formations.

2. The method of claim 1, wherein the infused fluid stream is stored in an underground formation or formations by a well completion process.

3. The method of claim 1, wherein the carbon dioxide is obtained from flaring of hydrocarbon gas in oilfield operations.

4. The method of claim 1, wherein the fluid stream is produced water from oilfield operations.

5. A fluid treatment system for treating a fluid stream and storing carbon, comprising: a fluid injection or disposal well; one or more fluid treatment tanks, wherein the one or more fluid treatment tanks comprise at least one separator; one or more downstream pipes connecting the one or more fluid treatment tanks with the fluid injection or disposal well; upstream pipes in fluid connection with the one or more fluid treatment tanks; an ozone injection system configured to inject ozone gas or an ozone-oxygen mixture gas into the fluid stream prior to the fluid reaching the fluid injection or disposal well; an oxygen de-gasser or de-aerator, configured to remove gaseous oxygen from the fluid stream; a carbon dioxide nanobubble generator, configured to introduce carbon dioxide into the fluid stream.

6. The system of claim 5, wherein the ozone injection system injects the ozone gas or ozone-oxygen mixture gas upstream of the one or more fluid treatment tanks.

7. The system of claim 5, wherein the ozone injection system is a slipstream injection system configured to draw off a portion of the fluid stream for ozone gas or ozone-oxygen mixture gas injection.

8. The system of claim 5, wherein the ozone injection system injects a dose rate of ozone gas or ozone-oxygen mixture gas that varies over time.

9. The system of claim 8, wherein the dose rate varies dynamically as the quality of the fluid stream changes based upon continuous monitoring of the fluid stream quality.

10. The system of claim 5, wherein the ozone gas or an ozone-oxygen mixture gas is injected as nano-bubbles or micro-bubbles.

11. The system of claim 5, wherein the ozone injection system produces oxygen-depleted reject gas in the process of producing oxygen and/or ozone.

12. The system of claim 5, wherein the reject gas is directed to the at least one separator as blanket gas.

13. The system of claim 5, wherein the ozone injection system is contained in whole or in part in a moveable container.

14. The system of claim 5, wherein the ozone injection system is contained in whole or in part in two or more moveable containers or trailers.

15. The system of claim 5, wherein the fluid stream is produced water from oil or gas wells.

16. The system of claim 5, wherein the fluid stream is fracturing fluid for a hydrocarbon fracturing operation.

17. The system of claim 5, further comprising a nitrogen nano-bubble delivery system, configured to inject nitrogen or nitrogen-rich gas into the fluid stream.

18. The system of claim 5, wherein nitrogen or nitrogen-rich gas is injected downstream of the one or more fluid treatment tanks.

19. The system of claim 17, wherein said nitrogen nano-bubble delivery system comprises a manifold with one or more strainers and a mixer.

20. The system of claim 5, further comprising an oxygen gas injector configured to reinject said gaseous oxygen in nano-bubble or micro-bubble form into the fluid stream at different points from the point of removal.

Description

DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 shows a diagram of an exemplary embodiment of the present invention.

[0014] FIG. 2 shows a diagram of another exemplary embodiment of the present invention.

[0015] FIG. 3 shows a diagram of an embodiment with reject gas injection.

[0016] FIGS. 4-10 show exterior and interior views of single and dual unit embodiments of the present invention.

[0017] FIG. 11 shows an example of a system status display screen.

[0018] FIG. 12 shows a top view of a single unit embodiment of the present system.

[0019] FIGS. 13-15 show top views of a dual unit embodiment of the present system.

[0020] FIGS. 16-19 show examples of combined systems with friction reduction.

[0021] FIGS. 20-21 show examples of an oxygen de-aeration or de-gassing system in combination with one or more of the above systems.

[0022] FIGS. 22-24 show diagrams of exemplary embodiments of the present invention with carbon dioxide.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0023] Produced water originates at the wellhead, and then typically travels via pipeline 10 to tank batteries, where held for a gathering system for processing and treatment. In general, oil or other hydrocarbons are separated and collected, and the remaining wastewater is directed to an injection or disposal well 30. One of the most common oil/water separation systems use one or more “gun barrel” separation tanks 20, as seen in FIG. 1.

[0024] As the produced water travels from the wellhead and through the gathering system, it is subjected to various treatments or processes. For example, the produced water receives injections of chemicals at or near the well head, either in batch or continuous treatments. As the produced water slows down in the gun barrel separators 20, bacteria can accumulate and hydrogen sulfide can form. To counter this, biocidal agents typically are added upstream of the gun barrel separators. Chemical biocides generally are added at a predetermined, constant dose rate, but as produced water quality changes, this constant dose rate becomes ineffective.

[0025] In several embodiments, the present invention comprises an automated treatment system 2 that injects ozone or an ozone-oxygen mixture 40 upstream of the separators, with the dose rate changing dynamically as the produced water quality changes (as determined by continuous monitoring of the produced water quality). While ozone-oxygen may be added directly, in a preferred embodiment, as seen in FIG. 1, the system may operate as a “slipstream” injection system 40, that draws a portion of produced water from the produced water pipeline and injects ozone or an ozone-oxygen mixture into this drawn-off portion, which is then introduced back into the main produced water pipeline without disrupting or slowing normal operations. Disinfectants or other additives may also be injected into the drawn-off portion (or directly into the main produced water pipeline).

[0026] The ozone is consumed rapidly by bacteria, iron, sulfides and other reducers in the produced water stream, while the oxygen bubbles in the produced water provides an Induced Gas Flotation (IGF) effect in the downstream separators. The IGF effect clarifies the water by removing suspended matter in the produced water, such as oil or solids. The oxygen bubbles adhere to suspended matter, provide lift, floats lighter solids to the surface of the water, and improves the oil/water separation process.

[0027] In the ozone generation process, oxygen is separated from ambient air, with the remaining “reject gas” (i.e., the oxygen-depleted ambient air left after separation) typically vented to the atmosphere in prior art operations. In several embodiments of the present process, this reject gas instead is directed to the separation tank 20, where it is used as a blanket gas 50 in the tanks, as seen in FIG. 2. This reject gas comprises mostly nitrogen and thus is inert, and is used as a gas phase maintained above the liquid (i.e., the produced water being treated) in the separation tanks or other vessels to protect the liquid from air contamination and to reduce the hazard of explosion or fire.

[0028] In yet a further embodiment, as seen in FIG. 3, some or all of the reject gas (i.e., in conjunction with, or as an alternative to, the use of the reject gas as a blanket gas 50) may also be injected 60 into the produced water or fluid stream using a nano-bubble diffuser prior to disposal in the injection well 30. The nano-bubble diffuser introduces the inert gas (mostly nitrogen) into the produced water in the form of micro- or nano-bubbles, which provide friction reduction in the fluid being injected into the injection/disposal well, and reduces the injection/disposal well pump pressure.

[0029] While the system may be a permanently installed component of a produced water treatment facility, in various alternative embodiments, as seen in FIGS. 4-10, the system is contained in one or more portable, movable containers or trailers 110 with ventilation 112, such as a modified shipping container or wheeled trailer. One or more doors 120 allow user access to the interior, which contains the components of the system.

[0030] The container/trailer is moved to a desired location next to a section of the produced water pipeline, and fluid connection is made. The present system can thus be easily retro-fitted to existing produced water treatment facilities, removed when operations are terminated, or moved from location to location as needed. The system is fully automatic once installed, monitoring water quality and adjusting disinfectant and oxidation dosages automatically as water quality changes, and can be monitored and operated remotely, using a remote computer or mobile computing device (e.g., cell phone, tablet) (an example of a system monitoring display 122 is shown in FIG. 11).

[0031] FIG. 12 shows a top view of a schematic diagram of an exemplary insulated container 110 30 feet long and 7.5 feet wide with double doors 110 at one or both ends. The air/water handling system (e.g., air compressor, chiller, CDA) and water processing systems (O2 concentrator, O2 tank, ozone tank, injection system) are both contained in the same unit, and may be separated by an insulated panel 130 which also may have a door. The system in this configuration has a processing capacity of 15,000 BPD (barrels per day). The interior comprises power supply connections, programmable logic controller (PLC), air compressor, compressed/clean dry air package, oxygen concentrator, oxygen gas tank, chilling unit, ozone generator, air conditioning unit, transformer, quality testing unit, and fluid connections and pumps (as also seen in FIGS. 8-10). On one side of the unit is the injection and water quality “slipstream” piping 160 with pump(s) 162, which may be contained in or suspended above a spill containment tank, pool, or pit. Some of the slipstream piping may or may not enter the interior of the unit, although as shown, the slipsteam piping is outside and adjacent thereto.

[0032] FIGS. 13-15 shows a top view of dual container units 110a, 110b (FIG. 13 shows a view of both units, FIG. 14 shows a close-up view of the “remote” air/water handling system unit not directly connected to the slipstream piping, and FIG. 15 shows a close-up view of the water processing unit with the slipstream piping), each 20 feet long, with a processing capacity of 30,000 BPD. Several system components are doubled (e.g., two chillers, two air compressors, two ozone tanks, two O2 concentrators, and so on) for greater capacity, and the air/water handling system and water processing system are separately installed in respective container units as shown. Piping and conduits 114 extend between the units (e.g., A/C power conduits/cables, PLC communication conduits/cables, cooling water pipes, compressed air pipes).

[0033] While the figures show a side-by-side dual configuration, other configurations with two or more container units are possible, and are within the scope of this invention. The container units may be of various sizes, and the components therein may vary in placement and size from the figures.

[0034] In several embodiments, combined systems may be used to introduce ozone/oxygen (as described above) prior to or just prior to injection for “on-the-fly” disinfection and treatment, while also providing friction reduction benefits, in combination with a secondary nitrogen nano-bubble system that introduces nitrogen or nitrogen-rich gas in the form of micro- and/or nano-bubbles (through nano-bubble diffusers) to increase or optimize friction reduction. The nitrogen nano-bubble delivery system may be contained in a container(s) or trailer(s) in the same manner as described above for oxygen/ozone systems. The nitrogen nano-bubble delivery system 200 also may be used independently (i.e., without the ozone/oxygen system) as an “on-the-fly” stand-alone friction reduction system. A nitrogen concentrator also may be used to add nitrogen or increase the nitrogen concentration in a gas prior to forming the bubbles.

[0035] FIG. 16 shows two examples of optional placement for a nitrogen nano-bubble delivery system 200a, b at an oil/gas produced water (e.g., salt water) disposal facility. As seen, the system may be located just prior to 200a injection in the disposal well, or further upstream, such as prior to 200b treatment in a desander tank and gun barrel tanks (as described above). FIGS. 17 and 19 show similar options for fracking water treatment (e.g., typically prior to 200c or after 200d storage in the frac water tanks).

[0036] FIG. 18 shows a schematic of a nitrogen nano-bubble delivery manifold 220. A portion of produced water is drawn off, passed through strainers 222, and injected with nitrogen nano-bubbles 224, then mixed 226 back with the produced water. The treated water 230 then flows downstream for further treatment (if any) and injection. Flow meters are used to monitor fluid flow and control the introduction rates of nitrogen nano-bubbles.

[0037] In further additional embodiments, as seen in FIG. 19-21, during the ozone/oxygen injection step described above, the ozone reacts almost immediately, but some of the oxygen in larger bubbles will phase separate and create gas pockets within the pipeline. This gas typically off-gasses at the first release point. By use of a de-aerator or de-gasser 300 (e.g., a riser under a vacuum), as seen in FIGS. 19-21, separated oxygen may be recovered and re-injected using a nano/micro-bubble type injection system. This will allow the oxygen to stay in suspension and provide additional treatment/oxidation from the reinjected oxygen. This oxygen gas stream may be reinjected as a pre-aeration step upstream 310 (either into water source storage or otherwise prior to the oxygen/ozone injection point) of the treatment by the main system to provide pre-treatment. Alternatively, such as in addition to pre-treatment or when pre-treatment is not necessary, the injected oxygen gas can be added into the water post-treatment 320 as a pre-aeration step or post-aeration step for produced water going into a storage system. Produced water going into a storage system is typically aerated to preserve the water. This posttreatment option will reduce and possibly eliminate the need for aeration during the storage phase. FIG. 20 shows a salt-water or saline-water disposal operation, with both upstream 310 and downstream 320 injection of oxygen gas.

[0038] In various exemplary embodiments, the present invention comprises a combined aeration system supplemented with a nanobubble delivery system to capture and store carbon, typically in the form of carbon dioxide (CO.sub.2) (i.e., “carbon capture”). As described in detail below, produced water is generated as a byproduct of oil and gas extraction. Carbon dioxide is highly soluble in water, but is reduced at higher temperatures (see addendum below for details). Produced water at the wellhead often is in excess of 100 degrees F. In the present invention, carbon dioxide is introduced to produced water in the form of nanobubbles.

[0039] Gases introduced into water form bubbles. Depending on the size of the bubbles and the solubility and stability of the gases, the bubbles may rise to the surface and produce “off gas,” or may go into solution or be dissolved in the water. This process is dependent on the pressure and temperature of the water. Very small bubbles, called “nanobubbles,” generally stay in suspension in the fluid, do not rise to the surface, and rely more on Brownian Motion for movement. Nanobubbles are also very stable and will remain in the water (or other fluid) for long periods of time (the stability of the particular gas being a factor). Nanobubbles also allow for much higher concentrations of gases to be introduced well beyond the saturation point, thereby allowing for super-saturated concentrations of the gas.

[0040] In water, carbon dioxide often will convert to carbonates, bicarbonates and, to a lesser degree, carbonic acid. This converted carbon dioxide does not enter the atmosphere as carbon dioxide gas. This process can be accelerated catalytically to form compounds such as calcium carbonate. In water storage systems, the formation of carbonates often increases the likelihood of “scaling” (although the use of scale inhibitors in oilfield water management can mitigate this). However, this concern is further mitigated as carbon dioxide in nanobubble form will itself help prevent scaling.

[0041] Aeration is a process of introducing oxygen into water to help control bacteria and improve the overall quality of the water. In the management of produced water, aeration is used as a pre-treatment to oxidation and to preserve disinfection. The higher temperature of produced water from the wellhead can be reduced through the process of aeration. This reduction in temperature allows more carbon dioxide to be absorbed by the produced water. This absorption process can be accelerated by adding carbon dioxide to the airstream used in the aeration process. Aeration in accordance with the present invention allows for additional carbon capture by decreasing the temperature of the produced water, and increasing the concentration of carbon dioxide introduced to the produced water.

[0042] Exemplary applications of the present invention are described below.

[0043] 1. Produced Water Recycling/Re-use.

[0044] In produced water reuse/recycle applications, as seen in FIGS. 22-24, the produced water is stored in large pits and tanks (e.g., aboveground storage tank, or AST 500, or a treatment pit 600. Aeration is employed in these storage devices to preserve the water and provide ongoing bacterial control; in the embodiment show, produced water is removed from the AST 500 by pipe 502 and pump 504 (flow is controlled by various valves 506 and monitored by various meters 508). The produced water is then directed to a manifold 510 and reinjected back into the tank 500 through a plurality of pipes (with control valves and meters) with Venturi mixers 512 to agitate and promote mixing of the produced fluid in the tank.

[0045] The introduction of carbon dioxide in nanobubble form allow these storage devices to become carbon capture systems. Carbon dioxide from a source 520 is mixed with inflowing produced water 522 in a nanobubble generator 530. The water becomes super-saturated with carbon dioxide through the creation and utilization of nanobubbles. The nanobubbles also will reduce the friction of the produced water while in storage (e.g., in the storage tank).

[0046] When the produced water is reused/recycled, as seen in FIG. 23, this reduced friction will reduce pump pressures and increase the efficiency of the pumps, thereby reducing emissions. In the well completion process, using water infused with carbon dioxide nanobubbles 540 also benefits from the lower friction water by reducing the need for chemical friction reducers to be added to the completion fluid. The well completion process also becomes an additional carbon capture system when the completion fluid remains underground.

[0047] 2. Waterfloods/EOR.

[0048] In waterflood applications, water and produced water are used in conventional oil well development by being injected through a plurality of injection well into underground hydrocarbon reservoir/formations to add pressure, thereby enhancing the recovery of oil from the formation (resulting in increased production from production wells in that formation). Adding carbon dioxide in the form of nanobubbles to the injection water improves the hydraulic characteristics of the injection water (e.g., through reduced friction). This also results in a better storage process for the carbon dioxide, as carbon dioxide in the present invention remains in nanobubble form. This is an advantage over the simple introduction of carbon dioxide gas to underground formations as a carbon capture technology, as the gas in that form will often migrate upwards to the surface and re-enter the atmosphere, thereby reducing its effectiveness for carbon capture. In addition, as mentioned above, the present invention avoids the conversion (and thus removal or elimination) of carbon dioxide.

[0049] 3. Emissions Flaring.

[0050] Patton, U.S. patent application Ser. No. 16/653,864, filed Oct. 15, 2019, which is incorporated herein in its entirety by specific reference for all purposes, describes a system and apparatus for flaring hydrocarbon gas from oilfield operations using produced water (referred to as the “hydroflare process”). Emissions from flaring are scrubbed. Ozone may be added. In the flaring combustion process, carbon dioxide is formed, which can be captured through a variety of processes (e.g., amine systems). Carbon dioxide from the hydroflare process can be used for the applications and processes described above. A unique benefit from this use is combining the reduction of emissions from the treatment of oilfield gas with the increased carbon capture through new uses for the captured carbon dioxide in nanobubble form. Introducing carbon dioxide in the form of nanobubbles provides a unique way of storing carbon dioxide in a stable form by injecting it underground, particularly where produced water is already being used as an injection fluid.

[0051] Thus, it should be understood that the embodiments and examples described herein have been chosen and described in order to best illustrate the principles of the invention and its practical applications to thereby enable one of ordinary skill in the art to best utilize the invention in various embodiments and with various modifications as are suited for particular uses contemplated. Even though specific embodiments of this invention have been described, they are not to be taken as exhaustive. There are several variations that will be apparent to those skilled in the art.