BR112017022344B1 - Method of producing at least one stream of ultrafiltrate product - Google Patents

Abstract

METHOD OF PRODUCTION OF AT LEAST ONE Stream OF ULTRAFILTRATE PRODUCT, USE OF A BACKWASH UNIT AND METHOD FOR EXPULTING PARTICULATES ACCUMULATED ON MEMBRANE SURFACES. A method of producing purified water in an underground environment is provided, wherein ambient ground source water is introduced into and through one or more ultrafiltration membrane units of a groundwater treatment system and thereby producing , an ultrafiltrate substantially free of solid particulates with a major dimension greater than 0.1 micron. An electrochemical unit in fluid communication with at least one ultrafiltration membrane unit provides an antifouling solution. An ultrafiltrate-rich backwash fluid and at least a portion of the antifouling solution are supplied to at least one non-productive ultrafiltration membrane unit during a backwash cycle. A flow of source fluid through each of the ultrafiltration membrane units of less than thirty gallons per square foot per day limits the need for backwash cycles. Reducing the number of backwash cycles increases the autonomy and useful life of the system and limits the need for intervention for maintenance (...).

Description

FIELD OF THE INVENTION

[001] The present invention relates to methods for producing purified water from ambient water present in underground environments. In particular, the invention relates to the purification of ambient water in an underground environment, using ultrafiltration devices.

BACKGROUND OF THE INVENTION

[002] Enhanced oil recovery (EOR) water injection has been used for over 75 years and accounts for a substantial portion of current US oil production. Water injection is used to extract immobile oil present in the reservoir that would not otherwise flow naturally from the reservoir. Typically, this is a secondary recovery technique, however, it is also being considered in primary and tertiary production to increase final recovery.

[003] In conventional water injection processes, injection water can be drawn from the nearest available sources, with little regard for its chemical composition. Onshore injection water sources include rivers and aquifers, while seawater is used offshore. Water is usually filtered to remove particulates to prevent formation clogging. Certain reservoirs require sulphate removal from the water for use in the injection process in order to reduce the formation of a thin layer of barium sulphate and strontium sulphate within the reservoir. In a typical water injection EOR protocol, water is injected at a pressure approximately 500 psi (3.45 MPa) greater than the reservoir pressure. Single-phase water injection pumps are typically used in subsea applications.

[004] Low salinity water flooding (LSF) is a process of injecting the oil reservoir with water of known and suitable salinity to economically extract additional oil from sandstone and carbonate reservoirs. Since the pioneering work of Tang and Morrow (see, for example, Guoqing Tang and Norman R. Morrow, Oil Recovery by Waterflooding and Imbibition - Invading Brine Cation Valence and Salinity, SCA-9911, 1999), the benefits of low salinity injections have been demonstrated in both laboratory and field studies. LSF has been shown to produce 2% to 12% additional oil than could otherwise have been produced using conventional injection techniques.

[005] The use of LSF in an oil field can make other chemical and polymer EOR injection techniques more efficient and can provide cost savings by reducing chemical consumption while increasing hydrocarbon yields. Interestingly, there seems to be an ideal range of salinity for a specific oil reservoir. Ideal salinity is believed to depend on reservoir characteristics such as mineralogy, formation water chemistry, petroleum composition, surface chemistry, formation temperature and pressure. The ideal salinity level is typically in the range of 1,000 to 10,000 ppm total dissolved solids (TDS).

[006] In subsea oil field operations, options currently available to produce low salinity water for use in EOR injection protocols include (1) installation of a water treatment system on a topside platform and low salinity water piping. salinity product to a seafloor injection wellhead and (2) installation of an underground water treatment system adjacent to the seafloor injection well. The first option is made unattractive by the high cost of piping and the limited space available on topside platforms. The second option, although attractive in that it avoids the need for expensive piping and limited space on the platform, is made unattractive by the underground environment itself, which often has a high concentration of particulate matter that can severely limit the range of time during which a groundwater treatment system can be operated without maintenance.

[007] Therefore, there is a need for more robust methods for producing purified water in underground environments.

DESCRIPTION OF THE INVENTION

[008] In one embodiment, the present invention provides a method of producing purified water in an underground environment, the method comprising: (a) introducing ambient underground source water into and through one or more ultrafiltration membrane units and thereby producing an ultrafiltrate substantially free of solid particulates having a major dimension greater than 0.1 micron; (b) preparing in an electrochemical unit in fluid communication with at least one ultrafiltration membrane unit, an aqueous solution comprising one or more species of hypohalous acid; and (c) supplying an ultrafiltrate-rich backwash fluid and at least a portion of the aqueous solution comprising one or more hypohalous acid species to at least one non-productive ultrafiltration membrane unit during a backwash cycle; wherein a source fluid flow through each of the ultrafiltration membrane units is less than 51.0 L/m 2 hr (thirty gallons per square foot per day).

[009] In another embodiment, the present invention provides a method of producing purified water in an underground environment, the method comprising: (a) introducing ambient underground source water into and through one or more ultrafiltration membrane units and thereby producing an ultrafiltrate substantially free of solid particulates having a major dimension greater than 0.1 micron; (b) preparing in an electrochemical unit in fluid communication with at least one ultrafiltration membrane unit, an aqueous solution comprising one or more species of hypohalous acid; (c) supplying an ultrafiltrate-rich backwash fluid and at least a portion of the aqueous solution comprising one or more hypohalous acid species to at least one non-productive ultrafiltration membrane unit during a backwash cycle; (d) subjecting a portion of the ultrafiltrate to a nanofiltration separation step in a nanofiltration unit and thereby producing a nanofiltrate and a retentate rejected by the nanofiltration unit; and (e) subjecting a portion of the ultrafiltrate to a reverse osmosis separation step in a reverse osmosis membrane unit and thereby producing a permeate and a retentate rejected by the reverse osmosis membrane unit; wherein a source fluid flow through each of the ultrafiltration membrane units is less than 51.0 L/m 2 hr (thirty gallons per square foot per day).

[010] In yet another embodiment, the present invention provides a method of producing a hydrocarbon comprising: (a) injecting purified water derived from an ambient underground source fluid into a hydrocarbon reservoir to stimulate the flow of a hydrocarbon fluid. reservoir hydrocarbon; (b) receiving the hydrocarbon fluid in a hydrocarbon production well; and (c) transporting the hydrocarbon fluid from the production well to a storage facility; wherein the purified water is produced in a groundwater treatment system comprising: (i) one or more ultrafiltration membrane units configured to produce from the source fluid an ultrafiltrate substantially free of solid particulates having a larger top dimension at 0.1 micron; (ii) an electrochemical unit in fluid communication with at least one ultrafiltration membrane unit and configured to provide an aqueous solution comprising one or more hypohalous acid species; (iii) a backwash unit configured to supply an ultrafiltrate-rich backwash fluid and at least a portion of the aqueous solution comprising one or more hypohalous acid species to at least one non-productive ultrafiltration membrane unit during a cycle of backwash; (iv) a nanofiltration membrane unit configured to receive the ultrafiltrate and produce therefrom a nanofiltrate containing less than 100 parts per million sulfate species; and (v) a reverse osmosis membrane unit configured to receive the ultrafiltrate and produce therefrom a reverse osmosis membrane permeate and a reverse osmosis membrane retentate; wherein a source fluid flow through an ultrafiltration membrane unit is less than 51.0 l/m2h (30 gallons per square foot per day), and wherein the reverse osmosis membrane retentate is used as a fluid from source to electrochemical unit.

BRIEF DESCRIPTION OF THE DRAWINGS

[011] Various features, embodiments and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying figures, where like signs may represent like parts throughout the figures. Unless otherwise indicated, the figures provided herein are intended to illustrate the main inventive features of the invention. These principal inventive features are believed to be applicable to a wide variety of systems comprising one or more embodiments of the invention. As such, the figures should not include all conventional features known to one skilled in the art to be necessary for the practice of the invention.

[012] Figure 1 illustrates a groundwater treatment system.

[013] Figure 2 illustrates a groundwater treatment system.

[014] Figure 3 illustrates a groundwater treatment system.

[015] Figure 4 illustrates a groundwater treatment system.

[016] Figure 5 illustrates a groundwater treatment system.

[017] Figure 6 illustrates a groundwater treatment system.

[018] Figure 7 illustrates a component of the groundwater treatment system.

[019] Figure 8 illustrates a component of a groundwater treatment system.

[020] Figure 9 illustrates an application and a method that employ a groundwater treatment system.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[021] In the following specification and claims below, reference will be made to a number of terms, which shall be defined to have the following meanings.

[022] The singular forms “a”, “a”, “the” and “a” include the plural referents, unless the context clearly dictates otherwise.

[023] “Optional” or “optionally” means that the event or circumstance subsequently described may or may not occur, and that the description includes cases where the event occurs and cases where it does not.

[024] The approximation language, as used herein, throughout the specification and claims, can be applied to modify any quantitative representation that may vary, in an admissible way, without resulting in a change in the basic function to which it is related . Consequently, a value modified by a term or terms such as “about” and “substantially” is not limited to the precise value specified. In at least some cases, the approximation language can match the precision of an instrument to measure the value. Here and throughout the specification and claims, range limitations may be combined and/or interchanged, such ranges are identified and include all sub-ranges contained therein, unless the context or language indicates otherwise.

[025] As noted, in one or more embodiments, the present invention provides a groundwater treatment system comprising one or more ultrafiltration membrane units configured to produce an ultrafiltrate from ambient water present in an underground environment. . This ambient water is sometimes referred to herein as “fountain fluid” and/or “fountain water”. The subterranean environment is typically a zone within a body of water, such as a river, lake, or ocean. In one or more embodiments, the source fluid can be fresh water, brackish water or sea water. The present invention is intended to have a range of useful applications, for example, underground production of potable water in regions characterized by very cold winter temperatures. In addition, the present invention is expected to be especially useful in conjunction with advanced oil recovery operations from subsea hydrocarbon deposits, such as the deepwater oil fields discovered under the Gulf of Mexico. In operation, the groundwater treatment system can be supported by the soil of the body of water, such as the seabed, it can be suspended from surface ice, a supporting structure, such as a ship or other platform offshore, or the groundwater treatment system can be designed to float within the water column between the surface and the bottom.

[026] Regardless of the source water used, the groundwater treatment system provided by the present invention is configured to produce at least one product stream, an ultrafiltrate, that is substantially free of solid particulates that fall within a certain category. of size.

[027] As will be appreciated by those skilled in the art, the ultrafiltrate is produced by an ultrafiltration membrane unit component of the groundwater treatment system. This ultrafiltration membrane unit serves to reduce the level of particulates in the source water being processed by the groundwater treatment system and provides the ultrafiltrate substantially free of solid particulates with a larger dimension greater than 0.1 microns. For purposes of this invention, the term substantially free of solid particulates means that solid particulates in the ultrafiltrate with a larger dimension greater than 0.1 microns are not present in an amount greater than 100 parts per million. In one or more embodiments, the ultrafiltrate contains less than 50 parts per million solid particulates with a major dimension greater than 0.1 microns. In an alternate set of embodiments, the ultrafiltrate contains less than 10 parts per million solid particulates with a major dimension greater than 0.1 microns.

[028] Suitable ultrafiltration membrane units are commercially available and include those supplied by GE Power and Water (e.g. G-series spiral wound and ZEE WEED hollow fiber ultrafiltration membrane units), Atech innovations GmbH (for (e.g. ceramic hollow fiber ultrafiltration membrane units) Qua Group (e.g. Q-SEP hollow fiber ultrafiltration membrane units), Koch Membrane Systems (e.g. PURON hollow fiber ultrafiltration membrane units), DOW (e.g. PDVF hollow fiber ultrafiltration membrane units) and TRISEP (e.g. SPIRASEP spiral wound ultrafiltration membrane units). As those skilled in the art will appreciate, hollow fiber membranes can be single-hole or poly-hole, and can be operated in various modes, such as internal and external flow patterns, in dead-end filtration modes. ) and cross-flow, and in submerged or otherwise pressurized system configurations.

[029] In one or more embodiments, the present invention provides a groundwater treatment system comprising a single ultrafiltration membrane unit. In an alternative set of embodiments, the present invention provides a groundwater treatment system comprising a plurality of ultrafiltration membrane units. In one or more embodiments, the ultrafiltration membrane unit may comprise hollow fiber membranes. In an alternative set of embodiments, the ultrafiltration membrane unit may comprise one or more membrane sheets. In yet another set of embodiments, the ultrafiltration membrane unit may comprise one or more membrane sheets configured in a spiral wound membrane structure.

[030] During operation, the source fluid to be purified is introduced into an ultrafiltration membrane unit optionally disposed within a suitably constructed housing of metal or plastic or some combination thereof. In one or more embodiments, the housing is configured as a cylinder. The housing is typically equipped with one or more screen filters that prevent larger particulates present in the source fluid from encountering the membrane surfaces of the ultrafiltration membrane unit. Other types of filters that can be used to effect particulate removal from raw source fluid include disc filters and filter media. In one or more embodiments, the ultrafiltration membrane unit is arranged within a housing defining at least one settling chamber (see numbered elements (75a), (75b) and (75b) of Figures 7 and 8, for example). Such features, filters and settling chambers are considered to be particularly advantageous in subsea environments where substantial amounts of solid particulate material may be present. Source fluid may be introduced into the ultrafiltration membrane unit by the action of one or more downstream pumps which draw ambient water into and through the ultrafiltration membrane unit. Alternatively, one or more upstream pumps can be used to drive ambient water through the ultrafiltration membrane unit to produce the ultrafiltrate.

[031] In various embodiments, the underground water treatment system provided by the present invention comprises an electrochemical unit configured to convert water comprising halide ions into an aqueous solution comprising one or more hypohalous acid species. This solution can be used to treat the ultrafiltration membrane unit and prevent its clogging by living organisms and/or non-living fouling present in the underground environment. Typically, hypohalous acid species are presented on the ultrafiltration membrane during a backwash cycle at a concentration in the range of about 3 to about 200 parts of hypohalous acid species per million parts of backwash fluid. . In one or more embodiments, the concentration of hypohalous acid species present in the ultrafiltration membrane unit in a chemical backwash cycle is 200 ppm or less, alternatively 100 ppm or less, alternatively 50 ppm or less or , alternatively, 30 ppm or less. Since hypohalous acid species can damage other system components, such as nanofiltration membrane units and reverse osmosis membrane units, the groundwater treatment system is properly valved or otherwise configured to avoid contact of sensitive components with hypohalous species. See, for example, Figure 5, in which the valve (32) and the location of the electrochemical unit (18) prevent the hypohalous acid species from coming into contact with the nanofiltration membrane unit (50). In one or more embodiments, the system is configured to avoid contacting sensitive components with residual hypohalous species by neutralization and/or reduction. Thus, in one or more embodiments, a reductant, such as a cysteine or sodium sulfite solution, can be measured for an ultrafiltrate stream upstream of the sensitive system component, for example, upstream of a nanofiltration unit. of the system. In one or more embodiments, the system may be suitably equipped with a carbon filter configured to remove hypohalous acid species upstream from a downstream sensitive system component. In one or more embodiments, the system is configured to use either a chemical reducing stream or a carbon bed filter.

[032] When the groundwater treatment system is configured for operation in a saltwater environment, the ambient water will contain ample amounts of halide ions to generate neutral diatomic species such as chlorine (Cl2), bromine (Br2) and chloride. of bromine (BrCl) that hydrolyze rapidly in water to hypohalorous acid species, such as hypochlorous acid (ClHO), hypobromous acid (BrOH) and the conjugate bases ClO- and BrO-. The electrochemical unit may use raw seawater or one or more fluid streams produced by the groundwater treatment system, filtered seawater, an ultrafiltrate, a nanofiltrate, a retentate stream rejected by a nanofiltration membrane unit, a retentate stream rejected by a reverse osmosis membrane unit or a combination of two or more of the foregoing streams as a source of water comprising halide ions. Suitable electrochemical cells are known to those skilled in the art and can be advantageously incorporated into the electrochemical unit. The electrochemical unit, as with all system components, can be configured so that all components are constructively isobaric with the environment, which means that any pressure differences between the component and the underground environment will not compromise system operability.

[033] The electrochemical unit typically comprises an electrochemical cell powered using the electrical energy distribution and supply network used to provide energy to other components of the groundwater treatment system, for example, the system's pumps. During operation, power can be supplied to the groundwater treatment system through an umbilical connection from the system to a surface power source. In one or more embodiments, the electrochemical unit is configured to use ambient water as a source of water comprising halide ions. Under such circumstances, the electrochemical unit may comprise internal water purification components that allow the electrochemical unit to remove undesirable species capable of clogging the electrochemical cell or other component of the electrochemical unit. Thus, in one or more embodiments, the electrochemical unit may comprise one or more filters, one or more ultrafiltration membranes, one or more nanofiltration membranes, one or more reverse osmosis membranes, one or more electrodialysis membranes, a or more electrodialysis membranes configured for reverse electrodialysis or a combination of two or more of the above filters and water purification membranes. The electrochemical unit may also comprise one or more fluid pumps configured to introduce water comprising halide ions as needed into the unit, for example into an electrochemical cell of the unit.

[034] When the groundwater treatment system is configured for operation in a freshwater environment, the electrochemical unit may be equipped with a halide concentration membrane such as is known to those skilled in the art, which can be used to provide halide ions extracted from ambient water to an electrode component used to prepare aqueous solution comprising one or more species of hypohalous acid.

[035] In various embodiments, the groundwater treatment system provided by the present invention comprises a backwash unit configured to supply an ultrafiltrate-rich backwash fluid and at least a portion of the aqueous solution comprising one or more acid species. hypohalos to at least one non-productive ultrafiltration membrane unit. An ultrafiltrate-rich backwash fluid is composed primarily of ultrafiltrate, but may include other fluids and/or chemicals produced or otherwise made available to a groundwater treatment system. Thus, the ultrafiltrate-rich backwash fluid may comprise ambient water from the underground environment, or one or more fluid streams produced by a groundwater treatment system, a stream of ambient filtered water, a stream of nanofiltrate, a stream rejected by a nanofiltration membrane unit, a flow rejected by a reverse osmosis membrane unit, or a combination of two or more of the above flows. In one or more embodiments, the backwash unit comprises at least one pump, at least one valve or system component, such as a pump that can effectively function as a valve, and fluid lines that provide reverse flow of backwash fluid through the ultrafiltration membrane unit. In a backwash cycle, sometimes referred to simply as a “backwash”, the direct flow through the ultrafiltration membrane unit undergoing the backwash treatment is stopped and a reverse flow of backwash fluid is made to flow through the backwash unit. ultrafiltration membrane. The backwash cycles serve to expel particulates accumulated on the membrane surfaces of the ultrafiltration membrane unit. A backwash cycle may include continuous exposure of the ultrafiltration membrane unit to hypohalorous acid species produced in the electrochemical unit along with a reverse flow of ultrafiltrate-rich backwash fluid. Alternatively, the backwash unit may force at least a portion of the aqueous solution comprising one or more hypohalous acid species and then allow the membrane surfaces to be exposed to the hypohalous acid species under static conditions under which there is effectively no flow in either direction through the ultrafiltration membrane unit. Under certain backwash protocols, the backwash fluid may contain only ultrafiltrates.

[036] In one or more embodiments, the groundwater treatment system is equipped with turbulence-generating components that can be used to clean one or more surfaces of the system. Suitable turbulence generating components include cavitation devices, sonication probes and fluid jets (sometimes referred to herein as spray jets). In one embodiment, the system is equipped with spray jets that can be directed at surfaces of the system on which particulates can accumulate. The jets can be powered by system pumps and can use any available fluid as the cleaning fluid. For example, the cleaning fluid may comprise a stream of ambient water from the underground environment, or one or more streams of fluid produced by an underground water treatment system.

[037] During operation, the fluid flow through the system must be adequately limited in order to minimize the number of backwash cycles required to maintain optimal performance. Thus, the flux through individual ultrafiltration membrane units can advantageously be limited to less than 102.0 l/m 2 h (60 gfd - gallons per square foot of membrane surface per day), preferably less than 51.0 l/m 2 m2h (30 gfd), more preferably less than 25.5 l/m2h (15 gfd) and even more preferably less than 20.4 l/m2h (12 gfd). For comparable volumes of treated source fluid, lower flow rates tend to reduce particulate buildup on the membrane surfaces of the ultrafiltration membrane unit relative to higher flow rates.

[038] A reduction in the number of backwash cycles increases system autonomy and service life, and limits the need for intervention for maintenance and component replacement. Depending on the application and the distance from the environment in which the system is placed (e.g. a deep water environment versus a shallow water environment), the frequency of backwash cycles of the ultrafiltration membrane unit can be advantageously limited to less than 70 times a day, preferably less than 30 times a day, more preferably less than 10 times a day, and even more preferably less than 5 times a day. Typically, the duration of a backwash cycle is on the order of a few minutes. In one or more embodiments, the duration of a backwash cycle is preferably less than 20 minutes. In an alternative set of embodiments, the duration of a backwash cycle is preferably less than 10 minutes. In yet another alternative set of embodiments, the duration of a backwash cycle is preferably less than 5 minutes.

[039] Similarly, the number of chemical backwash cycles, backwash cycles in which the backwash fluid contains an effective concentration of hypohalous acid species, can be appropriately limited due to the relatively low fluid flow through the unit. of ultrafiltration membrane used in underground environments. Again, depending on the application and the distance from the environment in which the system is placed (eg, a deep water environment versus a shallow water environment), the frequency of chemical backwash cycles can be advantageously limited. In one or more embodiments, the duration of a chemical backwash cycle is preferably less than 20 minutes. In an alternative set of embodiments, the duration of a chemical backwash cycle is preferably less than 10 minutes. In yet another alternative set of embodiments, the duration of a chemical backwash cycle is preferably less than 5 minutes. The number of chemical backwash cycles can equal the total number of backwash cycles, or it can be a significant fraction of the total number of backwash cycles, or it can be just a small fraction of the total number of backwash cycles, depending on the need. of chemical treatment of the ultrafiltration membrane unit.

[040] In one or more embodiments, the groundwater treatment system provided by the present invention comprises at least one nanofiltration membrane unit, sometimes referred to herein as a nanofiltration unit. As those skilled in the art will appreciate, nanofiltration units can be employed to remove sulfate ions and other divalent ions such as calcium and magnesium from the fluid being processed. Suitable nanofiltration units include those supplied by GE Power and Water (e.g. D and SWSR series spiral wound nanofiltration membrane units), DOW (e.g. NF series spiral wound nanofiltration membrane units), Hydranautics-Nitto (e.g. ESNA series spiral wound nanofiltration membrane units) and Koch Membrane Systems (e.g. SPIRAPRO series spiral wound nanofiltration membrane units).

[041] In one or more embodiments, the nanofiltration unit is configured to receive the ultrafiltrate and produce from it a nanofiltrate containing less than 100 parts per million sulfate species (eg, CaSO4). In an alternative set of embodiments, the nanofiltration unit is configured to receive the ultrafiltrate and produce from it a nanofiltrate containing less than 50 parts per million sulfate ions (SO4-2). In one or more embodiments, the nanofiltrate is depleted in calcium and magnesium ions.

[042] In one or more embodiments, the groundwater treatment system provided by the present invention comprises at least one reverse osmosis membrane unit. As those skilled in the art will appreciate, reverse osmosis membrane units can be used to substantially reduce the concentration of dissolved solids, such as salts, in the fluid being processed. Suitable reverse osmosis membrane units include those supplied by GE Power and Water (e.g. spiral wound reverse osmosis membrane units from the A series), DOW (e.g. spiral wound reverse osmosis membrane units from the A series SW and BW), Hydranautics-Nitto (e.g. SWC series spiral wound reverse osmosis membrane units) and Koch Membrane Systems (e.g. Fluid System TFC series spiral wound reverse osmosis membrane units).

[043] In one or more embodiments, the reverse osmosis membrane unit is configured to receive the nanofiltrate and produce therefrom a permeate substantially free of dissolved solids. In one or more alternative embodiments, the reverse osmosis membrane unit is configured to receive said at least a portion of the ultrafiltrate and produce therefrom a permeate substantially free of dissolved solids. As used herein, the term substantially free of dissolved solids means that the permeate contains less than 2 weight percent dissolved solids. In one or more embodiments, the permeate contains less than 1 weight percent dissolved solids. In an alternate set of embodiments, the permeate contains less than 0.5 weight percent dissolved solids. In yet another set of embodiments, the permeate contains less than 0.1 weight percent dissolved solids.

[044] Turning now to the figures, Figure 1 illustrates a groundwater treatment system (10) comprising a single ultrafiltration membrane unit (12). The system is shown as configured to use ambient seawater (14) as a source fluid. During direct operation, seawater enters and is processed by the ultrafiltration membrane unit (12) to provide the ultrafiltrate (16) which passes through the valve (32a) and along the ultrafiltrate production line (15), motivated by the fluid pump (21a). During direct operation, valves (32e) and (32g) may be open to fill the ultrafiltrate storage tank (22) while supplying a stream of ultrafiltrate product (16) through the valve (32e). Alternatively, one of the valves (32e) and (32g) can be closed during direct operation, as when, for example, the ultrafiltrate storage tank (22) has been filled and the system can be operated in direct mode with the valve ( 32g) closed and the valve (32e) open. As will be appreciated by those skilled in the art, during direct operations, valves (32b) and (32f) will be normally closed, but need not be in all situations.

[045] Still referring to Figure 1, the system comprises a backwash unit (20) configured to supply at least a portion of the ultrafiltrate (16) and at least a portion of the aqueous solution (19) comprising one or more acid species hypohalorous to at least one ultrafiltration membrane unit (12). The backwash unit comprises the system components needed to perform backwash cycles and chemical backwash cycles. In the embodiment shown, the backwash unit (20) includes the pump (21a), the ultrafiltrate storage tank (22), the valves (32g), (32f) and (32b), the backwash line (17). ) and the electrochemical unit (18).

[046] During a backwash cycle, valves (32a), (32e) are typically closed and valves (32b), (32g) and (32f) are typically open. To start the backwash cycle, the flow through the pump (21a), which is a bidirectional pump capable of pumping a fluid in opposite directions, is changed from forward flow to reverse flow. In reverse flow mode, the pump (21a) draws the ultrafiltrate (16) from the ultrafiltrate storage tank (22) through the open valve (32g). The pump drives the ultrafiltrate (16) through the open valve (32f) and into the backwash line (17) and into the ultrafiltration membrane unit (12). The reverse flow of ultrafiltrate (16) through the ultrafiltration membrane unit (12) expels particulates adhering to the membrane surfaces of the unit and is discharged to the underground environment as a discharge stream (25) which includes the ultrafiltrate (16) enriched in particulates, but which on the other hand has the same composition as sea water. The discharge stream may also include a portion of aqueous solution (19).

[047] During a chemical backwash cycle, the electrochemical unit (18) supplies an aqueous solution (19) comprising one or more species of hypohalous acid to the backwash line (17) through which the aqueous solution (19) passes through and is supplied to the ultrafiltration membrane unit (12). In one or more embodiments, the aqueous solution (19) is supplied essentially as produced by the electrochemical unit to the ultrafiltration membrane unit. In an alternative set of embodiments, the aqueous solution is supplied to the ultrafiltration membrane unit after it has been mixed with the ultrafiltrate (16) from the ultrafiltrate storage tank (22). As will be appreciated by those skilled in the art, the solution (19) may be supplied as produced (undiluted) to the ultrafiltration membrane unit by an electrochemical unit suitably equipped with a pump configured to drive the aqueous solution (19) from the electrochemical unit to the ultrafiltration membrane unit with valves (32a) and (32f) in closed positions and the pump (21a) in a non-pumping mode. In the presented embodiment, ambient seawater provides the source of water comprising halide ions which is converted in the electrochemical unit (18) into an aqueous solution (19) comprising one or more species of hypohalous acid. As noted, the electrochemical unit (18) may comprise one or more filters, one or more ultrafiltration membranes, one or more nanofiltration membranes, one or more reverse osmosis membranes, or a combination of two or more of the above filters and water purification to enable efficient use of ambient groundwater as a source fluid from which an antifouling solution can be prepared (19).

[048] Referring to Figure 2, said figure represents a groundwater treatment system (10) comprising a pair of ultrafiltration membrane units (12) that can simultaneously provide a single stream of ultrafiltrate (16). Alternatively, a first ultrafiltration membrane unit (12) may be used to provide a stream of ultrafiltrate (16) during a backwash cycle being applied to a second ultrafiltration membrane unit. This second ultrafiltration membrane unit is not operated in direct mode during the backwash cycle and is said to be non-productive.

[049] During a direct operating cycle where both the first and second ultrafiltration membrane units are producing the ultrafiltrate (16), seawater (14) is drawn into and through each of the membrane units. of ultrafiltration by the action of the system pump (21a). During this direct operation, valves (32a), (32c) and (32e) are open and valves (32b), (32d) and (32f) are closed. As will be appreciated by those skilled in the art, when valves (32b) and (32d) are one-way valves (i.e., check valves), they will effectively be closed to the opposite flow. In the embodiment shown, the valves (32b) and (32d) may be check valves that allow flow towards their respective ultrafiltration membrane units (12) and prevent flow in the opposite direction.

[050] Still referring to Figure 2, the system can be operated during a backwash cycle as follows. For illustrative purposes, we will consider a first backwash cycle, in which the highest ultrafiltration membrane unit (12) serves as the source of an ultrafiltrate stream being supplied to the lowest non-productive ultrafiltration membrane unit (12). To effect such a backwash cycle, valves (32b) and (32c) are closed while valves (32a), (32d) and (32f) are open. The valve (32e) can be open or closed. If open, the valve (32e) and/or one or more of the other valves in the system can be suitably throttled to accommodate the simultaneous production of ultrafiltrate (16) in the valve (32e) while driving an effective amount of a backwash fluid rich in ultrafiltrate to a non-productive ultrafiltration membrane unit. The pump (21a) draws ambient seawater (14) into and through the uppermost ultrafiltration membrane unit. The ultrafiltrate produced passes through the valve (32a) and through the ultrafiltrate production line (15). With valve (32e) closed or properly throttled, and valves (32f) and (32d) open, the ultrafiltrate (16) is moved by the pump past the electrochemical unit (18) and through the backwash lines (17) and ( 17b) to the lowest ultrafiltration membrane unit (12). One skilled in the art will understand that valves (32b) and (32d) may advantageously be non-return valves which may be further closed with respect to flow in either direction. For example, in the backwash cycle just described, the flow of ultrafiltrate (16) through the valve (32b) must be avoided so that the pump (21a) can efficiently drive the ultrafiltrate (16) produced in the ultrafiltration membrane unit further down. high (12) through the lowest ultrafiltration membrane unit. During such a backwash cycle, the particulate-enriched discharge stream (25) exits the lower ultrafiltration membrane unit.

[051] With reference to Figure 3, said figure represents a groundwater treatment system that comprises a controller (30) configured to drive various system components, pumps (21a) and (21b), valve (32) and electrochemical unit (18). During direct operation, the pump (21a) draws ambient groundwater (14) into and through the ultrafiltration membrane unit (12) to produce the ultrafiltrate (16) which is directed to the ultrafiltrate storage tank (22). ). As the storage tank (22) fills with the ultrafiltrate (16), the movable wall (24) is displaced to accommodate the ultrafiltrate. In one or more embodiments, the ultrafiltrate storage tank (22) is an expandable balloon-type tank. Once the storage tank (22) has been filled, the controller (30) opens the valve (32) to provide a stream of ultrafiltrate product (16). One skilled in the art will understand the steady-state nature of the production of the ultrafiltrate stream exiting valve (32). Thus, once the storage tank has been filled, the amount of ultrafiltrate present in the storage tank does not need to change during a direct operating cycle.

[052] In the embodiment presented, the system comprises a backwash unit (20) comprising the pump (21b), the backwash line (17), the electrochemical unit (18) and the storage tank (22). For the transition from a direct operating mode, in which ultrafiltrate is being produced, to a backwash cycle mode, in which at least a portion of the produced ultrafiltrate is consumed as backwash fluid, the controller (30) in response to an established backwash cycle schedule, or in response to a signal from a sensor within the ultrafiltration membrane unit or elsewhere within the system, shuts off the pump (21a) and closes the valve (32). The controller can then direct the pump (21b) to be started so as to pump a mixture of antifouling solution (19) and stored ultrafiltrate (16) through the ultrafiltration membrane unit (12). In the presented embodiment, the controller communication connections, as illustrated by, but not limited to, the numbered elements (34), allow the controller to detect the operating parameters of the system and control the operation of the system components.

[053] With reference to Figure 4, the figure represents a groundwater treatment system (10). In the illustrated embodiment, the system comprises a plurality of ultrafiltration membrane units (12). The controller (30) monitors system parameters and controls various system components. In one or more embodiments, the controller (30) is configured to be located away from system components placed in an underground environment. In an alternative embodiment, the controller (30) is configured to be located within the underground environment. In yet another embodiment, the controller (30) is configured to be placed in an underground environment and to function as a relay for a main controller located outside the underground environment.

[054] During a first direct operating mode, each of the ultrafiltration membrane units (12) produces ultrafiltrate (16) under the influence of a single pump (21a). The combined ultrafiltrate output from the ultrafiltration membrane units enters and is passed through the ultrafiltrate collector (40) and electrochemical unit (18). In practice, a slip stream of ultrafiltrate (16) only passes through the electrochemical cell of the electrochemical unit (18). During a direct operating mode, the electrochemical unit can advantageously be turned off in such a way that antifouling solution (19) is not produced. The combined outlet (16) from the ultrafiltration membrane units (12) passes through the manifold (42) and out through the valve (32g). As will be appreciated by those skilled in the art, during the direct operating mode just described, each of the valves (32a), (32b), (32c) and (32g) will be open, while each of the valves (32d), ( 32e) and (32f) will be closed.

[055] During a backwash cycle, the production of at least one of the ultrafiltration membrane units is used to generate a reverse flow of backwash fluid through at least one ultrafiltration membrane unit that is not producing ultrafiltrate. For illustrative purposes, we will consider a backwash cycle in which the two highest ultrafiltration membrane units (12) continue to operate while the lowest ultrafiltration membrane unit (12) is not producing ultrafiltrate. Under such circumstances, valves (32a) and (32b) remain open while valve (32c) is closed. The valve (32g) can be closed or remain open or partially open, depending on the circumstances. For example, in an oil reservoir injection operation, it may be desirable not to interrupt the flow of water being produced by the system to the reservoir. Thus, under various conditions, the valve (32g) may remain open during a backwash cycle. Under the influence of the pump (21) the ultrafiltrate (16) is drawn from the two uppermost ultrafiltration membrane units to the ultrafiltrate collector (40) and from there to the electrochemical unit (18) which can be on or off. off, depending on whether the backwash cycle includes feeding the antifouling solution (19) back to the ultrafiltration membrane unit being washed back. For illustrative purposes, we will assume a chemical backwash cycle in which the electrochemical unit is directed by the controller (30) to start generating the antifouling solution (19). In the presented embodiment, the ultrafiltrate stream (16) serves as the source fluid for the electrochemical unit where it is converted to antifouling stream (19). The pump (21a) drives the antifouling stream (19) through the collector (42) and through the open backwash unit valve (32f) to the lower ultrafiltration membrane unit (12), from which it emerges. as discharge current (25). Valves (32d) and (32e), although configured to be capable of serving as components of the backwash unit (20), remain closed in this illustrative example.

[056] Referring to Figure 5, said figure represents a groundwater treatment system (10), with a single ultrafiltration membrane unit (12) configured as in the embodiment shown in Figure 3 with the main exception of that the system further comprises a nanofiltration unit (50) which provides a nanofiltrate (56) as a source fluid for the electrochemical unit (18). In the embodiment, the system is shown operating in a backwash cycle which may be a chemical backwash cycle wherein the backwash fluid comprises an effective amount of one or more hypohalous acid species, or, alternatively, the ultrafiltrate. (16) alone. Sometimes an ultrafiltrate-rich backwash fluid containing hypohalous acid species will be designated here by element number (19/16). During the backwash cycle illustrated in Figure 5, the pump (21a) is in a non-pumping mode while the pump (21b) of the backwash unit draws a first stream of ultrafiltrate (16) from the storage tank (22). through the nanofiltration unit (50). The resulting nanofiltrate (56) is then drawn through the open valve (32a) and into the electrochemical unit (18) where it is converted into an antifouling solution (19). Simultaneously, the pump (21b) draws a second stream of ultrafiltrate from the storage tank through the valve (32c). Valves (32a) and (32c) are subject to the controller (30) and act to limit the relative flow rates of the first and second streams of ultrafiltrate. In the example of the backwash cycle shown here, valve 32b remains closed. In the embodiment shown, a designated backwash fluid (19/16) is supplied to the non-productive ultrafiltration membrane unit (12) (Figure 3).

[057] Referring to Figure 6, said figure represents a groundwater treatment system (10) having a plurality of ultrafiltration membrane units (12) configured as in the embodiment illustrated in Figure 4. In the embodiment shown, the system further comprises a nanofiltration unit (50) and a reverse osmosis membrane unit (60). During direct operation, the combined output of the ultrafiltration membrane units passes through the ultrafiltrate collector (40) (Figure 4). Driven by the pump (21a), the combined stream of ultrafiltrate bypasses the backwash manifold (42) and can exit the system through the valve (32g), or be split and directed to one or more of the outlet valves (32g), unit nanofiltration unit (50), reverse osmosis membrane unit (60) or a combination of two or more of the foregoing system components. Thus, during direct operation, the groundwater treatment system may produce only the ultrafiltrate (16), only the nanofiltrate (56), only the reverse osmosis membrane permeate (66), or a combination of two or more of the currents. of previous products. The system can produce as a by-product stream, a retentate stream (58) rejected by the nanofiltration unit (50) and a retentate stream (68) rejected by the reverse osmosis membrane unit (60). In one or more embodiments, valves (32d), (32e), (32f) and (32h) are closed during direct operation and at least one of valves (32g), (32i) and (32j) are open. .

[058] Still referring to Figure 6, during a backwash cycle, one or more of the valves (32a), (32b) and (32c) (Figure 4) are closed while keeping at least one of the aforementioned valves open. For purposes of illustration, we will consider the case where valve (32c) has been closed and valves (32a) and (32b) remain open (Figure 4). Under such circumstances, the lowest ultrafiltration membrane unit is non-productive, while the higher ultrafiltration membrane units continue to produce ultrafiltrate. With at least one of the ultrafiltration membrane units in a non-productive mode, the combined output of the direct operating ultrafiltration membrane units is moved from the ultrafiltrate manifold (40) (Figure 4) by the pump (21a). Bypassing the backwash manifold (42), the ultrafiltrate can be directed through the valve (32h) to the backwash manifold (42) and from there through the valve (32f) and the backwash line (17c) to the lower ultrafiltration membrane (12). Simultaneously, the system can deliver one or more useful product streams despite the continuous backwash cycle. Thus, during the backwash cycle, the system may continue to produce an ultrafiltrate stream (16) in the valve (32g), a nanofiltrate stream (56), a reverse osmosis membrane permeate stream (66), or a combination of two or more of the previous streams.

[059] In the presented embodiment, the electrochemical unit (18) is configured to receive a retentate current (68) rejected by the reverse osmosis membrane unit (60) and convert it into the antifouling solution (19). The retentate stream (68) can be advantageously employed in the preparation of an aqueous solution (19) comprising one or more species of hypohalous acid, as it will be rich in halide species (e.g., NaCl, NaBr) necessary for the production of hypohalous acid species, in relation to seawater (14), ultrafiltrate (16) and nanofiltrate (56). In one embodiment, the nanofiltrate (56) is used as the source fluid fed to the reverse osmosis membrane unit (60). The nanofiltrate (56) is relatively free of divalent ions such as Ca++ and Mg++, species known to clog electrochemical cells. As a result, retentate (68) will be relatively free of Ca++ and Mg++ while being rich in salts of useful halides such as sodium chloride. In an alternative embodiment, the ultrafiltrate (16) may be used as the source fluid for the reverse osmosis membrane unit (60).

[060] During a backwash cycle, the antifouling solution (19) enters the backwash collector (42) where it mixes with the ultrafiltrate (16) that enters the collector through the open valve (32h). A mixture of antifouling solution (19) and ultrafiltrate (16) (designated (19/16) in Figure 6) is led through the open valve (32f) and backwash line (17c) to the membrane unit. lower non-productive ultrafiltration (12) through which it flows in a direction indicated by the dashed arrow marked (25) (Figure 4). As noted, (25) represents a particulate-rich discharge stream expelled from membrane surfaces within the ultrafiltration membrane unit by the reverse flow of backwash fluid.

[061] The system configuration illustrated by Figure 6 can be especially useful in applications that require water with a low concentration of bivalent species such as calcium ions, magnesium ions, sulfate ions and moderate salinity, for example certain advanced recovery techniques of petroleum involving water injection or water/gas injection from an underground hydrocarbon deposit. Under such circumstances, it may be advantageous to simultaneously produce a stream of nanofiltrate (56) and a stream of reverse osmosis membrane permeate (66) and subsequently mix the two streams at one or more stages of the injection process.

[062] With reference to Figure 7, said figure represents a portion of a groundwater treatment system (10). In the embodiment shown, an ultrafiltration membrane unit (12) is arranged inside the housing (70), the interior of which is in fluid communication with the underground environment through fine and coarse screen filters (71) and (72) , respectively, and optionally through housing discharge outlets (78a) and (78b), shown here as closed. In the presented embodiment, the housing is supported by support structures (79) which, in turn, can be supported on the ground of the underground environment. Housing (70) can enclose the entire groundwater treatment system and include, in addition to the components illustrated in Figure 7, valves, flow lines, pumps, manifolds, nanofiltration units, reverse osmosis membrane units, electrochemical units, sensors, controllers, storage tanks, spray jets and other system components. During direct operation, ambient groundwater (14) enters the housing (70) through filters (71) and (72). Particulates entrained by groundwater can settle at various points within the housing which is equipped with one or more coarse particulate outlets (73) and fine particulate outlets (74) which act to remove particulates not excluded by screen filters (71) and (72) and susceptible to sedimentation. Once ambient groundwater (14) enters the housing and advances towards the ultrafiltration membrane unit (12), ambient water (14) is first transformed into the source fluid (14a) from which larger particulates were removed by coarse filter (71) and in the source fluid (14b) from which additional particulates were removed by fine filter (72). Finally, a dam structure (76) can act to further segregate particulates from the source fluid (14b) and supply the source fluid (14c). The interior compartments (75a), (75b) and (75c) can act as sedimentation chambers. Sloped interior surfaces (77) and particulate outlets (73) and (74) can assist in removing particulates susceptible to sedimentation during direct operation. However, not all particulates will settle at useful rates and, as a result, differences in particulate content of source fluids (14b) and (14c) may be minimal. The particulate outlets (73) and (74) are shown as open and the particulate outlets (78a) and (78b) are shown as closed in Figure 7, but can be opened and closed independently as determined by one or more sensors. and system controllers. During direct operation, source fluid (14c) is drawn into and through the ultrafiltration membrane unit (12), is transformed into ultrafiltrate (16), and supplied to other system components through the ultrafiltrate production line ( 15).

[063] Still referring to Figure 7, during a backwash cycle, the backwash fluid (e.g. (19/16)) is introduced through the backwash line (17) and forced to flow through the backwash membrane unit. ultrafiltration in an opposite flow direction during direct operation. As detailed herein, this reverse flow of backwash fluid expels particulates adhering to membrane surfaces of the ultrafiltration membrane unit (12) and produces a particulate-laden discharge stream (25) that can exit the housing through one or more from the particulate outlets (78a) and (78b). A backwash cycle can also include a filter backwash protocol. For example, following a stage of the backwash cycle in which the interior of the housing has been purged by backwash fluid with the particulate outlets (78a) and (78b) open, these can be closed and all the flow of backwash fluid directed back through filters (72) and (71), thereby expelling particulates accumulated on filter surfaces.

[064] Referring to Figure 8, said figure represents a portion of a groundwater treatment system (10) comprising one or more turbulence generating devices configured to clean one or more surfaces of the system on which particulates accumulate. In the embodiment shown, the spray jets (80) may be located in close proximity to the surfaces of the system on which particulates accumulate, the surfaces of the system including coarse screen filter (71), fine screen filter (72) surfaces. ) and the outer membrane surfaces of the ultrafiltration membrane unit (12). In the embodiment shown, the surfaces of the system are being cleaned with the ultrafiltrate (16) during a backwash cycle in which the discharge stream (25) and the particulates expelled by the cleaning action of the spray jets leave the housing through one or more of the particulate outlets (78a) and (78b) of the housing. The particulate laden stream exiting the housing through particulate outlets (78a) is marked as (16a) since, in the embodiment illustrated in Figure 8, it uses ultrafiltrate (16) as a cleaning fluid. As noted, other suitable fluids can be used as the cleaning fluid. For example, in one or more embodiments, filtered spring water (14b) (Figure 7) can be used as the cleaning fluid.

[065] In one or more embodiments, the present invention provides a method for producing purified water from an ambient groundwater source, sometimes referred to herein as an ambient groundwater source fluid. Furthermore, in one or more embodiments, the present invention provides a method for producing a hydrocarbon that employs purified water derived from an ambient underground source fluid.

[066] Figures 1 to 8 and accompanying descriptions provide detailed guidance for using the groundwater treatment system to produce purified water from ambient groundwater. As noted, a first step of the method comprises introducing ambient ground source water into and through one or more ultrafiltration membrane units and thereby producing an ultrafiltrate substantially free of solid particulates having a larger dimension greater than 0.1 microns. As detailed here, ambient groundwater can be introduced into and through an ultrafiltration membrane unit of the system by the action of a system pump. In a second step of the method, an aqueous solution comprising one or more hypohalous acid species is prepared in an electrochemical unit of the system in fluid communication with at least one ultrafiltration membrane unit of the system. In a third step of the method, an ultrafiltrate-rich backwash fluid and at least a portion of the aqueous solution comprising one or more hypohalous acid species are supplied to at least one non-productive ultrafiltration membrane unit during a backwash cycle. . In one or more embodiments, the total ambient groundwater flux through individual ultrafiltration membrane units is less than 51.0 L/m 2 hr (thirty gallons per square foot per day). As noted, running the system at relatively low flow tends to reduce the frequency of backwash cycles required to maintain optimal system performance.

[067] In one or more embodiments, the present invention provides a method of producing a hydrocarbon. In a first step, the method comprises injecting purified water derived from an ambient underground source fluid into a hydrocarbon reservoir to stimulate the flow of a hydrocarbon fluid from the reservoir. In a second and third step, the method comprises receiving the hydrocarbon fluid in a hydrocarbon production well and transporting the hydrocarbon fluid from the production well to a storage facility. Purified water is prepared using ambient groundwater as the source fluid for a groundwater treatment system provided by the present invention.

[068] Referring to Figure 9, said figure illustrates a method (100) of producing a hydrocarbon, the method representing one or more embodiments of the present invention. As illustrated in Figure 9, ambient groundwater (14) serves as a source fluid for a groundwater treatment system (10) disposed within an underground environment (114). The groundwater treatment system (10) produces at least one stream of purified water (116) which is pumped through the injection well (118) and into the hydrocarbon reservoir (120). The purified water stream (116) may comprise one or more of the product streams produced by the groundwater treatment system (10), including an ultrafiltrate stream (16), a nanofiltrate stream (56) or a permeate stream. of reverse osmosis membrane (66). In one or more embodiments, the purified water stream (116) is a mixture prepared from a stream of nanofiltrate (56) and a stream of reverse osmosis membrane permeate (66). In one or more embodiments, the groundwater treatment system (10) may be configured to add one or more agents intended to enhance the recovery of hydrocarbon fluids from the reservoir, for example, lignin sulfonates and hydrolyzed polyacrylamides. In one or more embodiments, the purified water (116) may be alternately injected with carbon dioxide in an alternating water and gas reservoir injection protocol.

[069] Purified water entering the reservoir through the injection well (118) stimulates the flow of hydrocarbon fluids (126) towards and into the production well (132). Production fluids containing hydrocarbons entering the well are transported through the wellhead (134) and production lift system (136) to the storage facility (140). The production well (132) may be equipped with one or more electric submersible pumps that drive the production fluids (126) towards the wellhead (134) and production lift system (136). The wellhead installation may include equipment such as booster pumps, production fluid separators, Christmas trees and similar equipment known to those skilled in the art to be necessary and useful in managing the production of a hydrocarbon production well. underground.

[070] The previous examples are merely illustrative, serving to illustrate only some of the features of the invention. The appended claims are intended to claim the invention as broadly as it is conceived and the examples presented herein are illustrative of embodiments selected from a copy of all possible embodiments. Accordingly, it is the intent of the applicant that the appended claims not be limited by the choice of examples used to illustrate features of the present invention. As used in the claims, the word "comprises" and its grammatical variants logically also subtend and include phrases of various and different lengths, for example, but not limited to, "consisting essentially of" and "consisting of". Where necessary, ranges have been provided, these ranges are inclusive of all sub-ranges in between. It is to be expected that variations in these ranges can be suggested to one skilled in the art and are not already dedicated to the public, such variations should, whenever possible, be interpreted as covered by the appended claims. It is also anticipated that advances in science and technology will make equivalents and substitutions possible, which are not now contemplated due to imprecision of language, and these variations should also be interpreted, whenever possible, to be covered by the appended claims.

Claims (11)

1. METHOD (10) OF PRODUCING AT LEAST ONE ULTRAFILTRATED PRODUCT Stream (16) from source water in a subsea environment, characterized by method (10) comprising the steps of: (a) introducing underground source water environment (14) in and through two or more ultrafiltration membrane units (12) and thereby producing an ultrafiltrate (16) free of solid particulates having a larger dimension greater than 0.1 microns; (b) preparing in an electrochemical unit (18) in fluid communication with at least one of the ultrafiltration membrane units (12), an aqueous solution (19) comprising one or more species of hypohalous acid; and (c) supplying to at least one non-productive ultrafiltration membrane unit (12) during a backwash cycle a backwash fluid rich in ultrafiltrate (16) with ultrafiltrate (16) from at least one other ultrafiltration membrane unit (12) productive and at least a portion of the aqueous solution (19) comprising one or more hypohalous acid species; wherein a source fluid flow through each of the ultrafiltration membrane units (12) is less than 51.0 l/m 2 h. METHOD (10) according to claim 1, characterized in that the backwash cycle occurs at a frequency of less than five backwash cycles per day. 3. METHOD (10), according to claim 2, characterized in that each backwash cycle has a duration of less than twenty minutes. METHOD (10) according to claim 1, characterized in that a chemical backwash cycle lasts for less than twenty minutes. METHOD (10) according to claim 1, characterized in that ambient underwater source water (14) is seawater. 6. METHOD (10), according to any one of claims 1 to 5, characterized in that the method additionally comprises the steps of: (d) subjecting a first portion of the ultrafiltrate (16) to a nanofiltration separation step in a unit of nanofiltration (50) and thereby producing a nanofiltrate (56) and a retentate (58) rejected by the nanofiltration unit (50); and (e) subjecting a second portion of the ultrafiltrate (16) to a reverse osmosis separation step in a reverse osmosis membrane unit (60) and thereby producing a permeate (66) and a retentate (68). rejected by the reverse osmosis membrane unit (60). METHOD (10) according to claim 6, characterized in that the purified water comprises at least a portion of the nanofiltrate (56) and at least a portion of the permeate (66) of the reverse osmosis membrane. METHOD (10) according to claim 6, characterized in that the purified water contains less than two percent of dissolved solids. METHOD (10) according to claim 6, characterized in that the electrochemical unit (18) is configured to receive the retentate (68) of the reverse osmosis membrane unit (60) as a source fluid and produce, from furthermore, an aqueous solution comprising one or more hypohalous acid species. METHOD (10) according to claim 6, characterized in that a groundwater treatment system (10) is configured to produce at least one product stream (16) not supplied to the ultrafiltration membrane unit (12) non-productive during a backwash cycle. METHOD (10) according to claim 6, characterized in that a groundwater treatment system (10) comprises at least one ultrafiltration membrane unit (12) comprising hollow fiber membrane structures.

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