Dynamic produced water treatment apparatus and system

An automated produced water treatment system that injects ozone or an ozone-oxygen mixture upstream of produced water separators, with the dose rate changing dynamically as the produced water quality changes, as determined by continuous monitoring of the produced water quality by a plurality of sensors that detect water quality parameters in real time. The system may operate as a “slipstream” injection system, that draws a portion of produced water from the produced water pipeline and injects ozone or an ozone-oxygen mixture back into the pipeline with disrupting or slowing normal operations. Disinfectants or other additives may also be injected. The treatment system may be wholly or partially contained in mobile containers or trailers, for on-the-fly use in existing produced water treatment facilities.

FIELD OF INVENTION

This invention relates to an apparatus and system for automatically and dynamically treated produced water from oil and gas production operations.

BACKGROUND OF THE INVENTION

A variety of oil and gas operations generate large volumes of water mixed with hydrocarbons and various contaminants, generally referred to in the industry as “produced water.” Most produced water is contaminated with inorganic salts, metals, organic compounds, and other materials, such as emulsifiers or other agents that may be injected for various types of enhanced recovery operations. Typical hydrocarbons in produced water include semivolatile organic compounds (“SVOCs”) and volatile organic compounds (“VOCs”). In most operations, produced water is treated by a variety of means to separate hydrocarbons from the fluid stream, and and remove or treat contaminants before ultimate disposal. Examples of systems and methods for treating produced water are described in Sullivan, et al., US 2009/0101572, Ikebe, et al., US 2010/0264068, and Folkvang, US 2014/0346118, all of which are incorporated herein in their entireties by specific reference for all purposes.

SUMMARY OF THE INVENTION

In various exemplary embodiments, the present invention comprises an automated treatment system that injects ozone or an ozone-oxygen mixture 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 by a plurality of sensors that detect water quality parameters in real time). In several embodiments, the system may operate as a “slipstream” injection system, that draws a portion of produced water from the produced water pipeline and injects ozone or an ozone-oxygen mixture back into the pipeline with disrupting or slowing normal operations. Disinfectants or other additives may also be injected. 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 provide lift, floats lighter solids, and improves the oil/water separation process.

In the ozone generation process, oxygen is separated from ambient air, with the remaining “reject gas” typically vented to the atmosphere in prior art operations. In the present process, the reject gas instead is directed to the separation tanks, where it is used as a blanket gas in the tanks. The reject gas comprises mostly nitrogen and thus is inert, and is used as a gas phase maintained above the liquid (i.e., produced water) in the separation tanks or other vessels to protect the liquid from air contamination and to reduce the hazard of explosion or fire.

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) may also be injected into the produced water or fluid stream using a nano-bubble diffuser prior to disposal in an injection well. 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, and reduces the injection/disposal well pump pressure.

Various combined systems may introduce ozone/oxygen just prior to injection for “on-the-fly” disinfection and treatment, while also providing friction reduction benefits, in combination with a secondary 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 also may be used independently 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.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Produced water originates at the wellhead, and then typically travels via pipeline10to 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 well30. One of the most common oil/water separation systems use one or more “gun barrel” separation tanks20, as seen inFIG. 1.

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 separators20, 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.

In several embodiments, the present invention comprises an automated treatment system2that injects ozone or an ozone-oxygen mixture40upstream 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 inFIG. 1, the system may operate as a “slipstream” injection system40, 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).

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.

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 tank20, where it is used as a blanket gas50in the tanks, as seen inFIG. 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.

In yet a further embodiment, as seen inFIG. 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 gas50) may also be injected60into the produced water or fluid stream using a nano-bubble diffuser prior to disposal in the injection well30. 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.

While the system may be a permanently installed component of a produced water treatment facility, in various alternative embodiments, as seen inFIGS. 4-10, the system is contained in one or more portable, movable containers or trailers110with ventilation112, such as a modified shipping container or wheeled trailer. One or more doors120allow user access to the interior, which contains the components of the system.

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 is shown inFIG. 11).

FIG. 12shows a top view of a schematic diagram of an exemplary insulated container11030 feet long and 7.5 feet wide with double doors110at 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 panel130which 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. On one side of the unit is the injection and water quality “slipstream” piping160with 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.

FIGS. 13-15shows a top view of dual container units (FIG. 13shows a view of both units,FIG. 14shows a close-up view of the “remote” air/water handling system unit not directly connected to the slipstream piping, andFIG. 15shows 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 extend between the units (e.g., A/C power conduits/cables, PLC communication conduits/cables, cooling water pipes, compressed air pipes).

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 inveniton. The container units may be of various sizes, and the components therein may vary in placement and size from the figures.

In several embodiment, 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 system200that 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 deliver 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 system200also 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.

FIG. 16shows two examples of optional placement for a nitrogen nano-bubble delivery system200at an oil/gas produced water (e.g., salt water) disposal facility. As seen, the system may be located just prior to200ainjection in the disposal well, or further upstream, such as prior to200btreatment in a desander tank and gun barrel tanks (as described above).FIG. 17shows similar options for fracking water treatment (e.g., typically prior to or after storage in the frac water tanks).

FIG. 18shows an schematic of a nitrogen nano-bubble delivery manifold220. A portion of produced water is drawn off, passed through strainers222, and injected with nitrogen nano-bubbles224, then mixed226back with the produced water. The treated water230then 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.