CA2848442A1

CA2848442A1 - Polymer flood water treatment

Info

Publication number: CA2848442A1
Application number: CA2848442A
Authority: CA
Inventors: Melonie Myszczyszyn
Original assignee: Canadian Natural Resources Ltd
Current assignee: Canadian Natural Resources Ltd
Priority date: 2014-04-08
Filing date: 2014-04-08
Publication date: 2015-10-08
Also published as: CA2939963A1; WO2015154167A1

Abstract

There is provided for a process for the treatment of sour saline water, produced water from oil industry operations, and mixtures with other waters for subsequent reuse for polymer flood water thereof, said process comprising subjecting the water to a mechanical separation step; a fluid degassing step;
optionally, a second oil removal step; a pH adjustment step, if necessary; an electrocoagulation step; a solids removal step through the addition of chemicals; a third mechanical separation step and oil removal step; a multimedia filtration step; and optionally, a bag filtration step.

Description

POLYMER FLOOD WATER TREATMENT
FIELD OF THE INVENTION
The invention relates to a method for treating polymer flood waters and flood waters used in oil industry operations for the subsequent reuse thereof and, more specifically, to the removal of compounds that impact the efficiency of polymers used in these types of applications.
BACKGROUND OF THE INVENTION
In the oil industry, extraction of oil from oil wells will typically yield in the range of 30% of the actual content in the reservoir being exploited. The process of water flooding refers to the method of injecting water into a reservoir resulting in an increase in pressure and subsequent increase in oil extraction. The flood water is injected into a reservoir and allows to maintain or increase the pressure inside the reservoir and replaced the extracted oil. It also allows to displace oil within the reservoir and push it towards a well.
The use of flood water allows for more production from a well and therefore increased savings by the extending the production expectancy of a well.
US2012/0152546A1 describes a process for water treatment specifically for SAGD
operations. There is described a process which uses chemical oxidation (CO) or electromagnetic treatment (ET) to destroy or degrade organics in the produced water. It is stated a primary purpose of the produced water treatment steps described above is to provide water of suitable quality to the steam generator.
US 7694736B2 generally describes a method and system for producing steam for extraction of heavy bitumen including the steps of mixing carbon or hydrocarbon fuel. It is stated that with its simple direct contact, above ground adiabatic nature, and its high pressure and temperature solid removal, the invention will minimize the amount of energy used to produce the mixture of steam and gas injected into the underground formation to recover heavy oil. It is stated that the present invention adds the adiabatic direct contact steam and carbon dioxide generation unit to reduce the disadvantages of the prior art and to allow for expansion with use of a low quality water supply, reject water from existing facilities and the use of low quality fuel supplies. Also, there is no need for high quality separation of the oil from the produced water and water purification processes with this invention. It is stated that the mixture produced at the EOR production well 65 is separated into gas (mainly carbon dioxide and natural gas), oil and water. The produced water contains heavy oil remains, dissolve minerals, sand and clay.
The separated low quality produced water 64 is used for steam generation 61 without any additional treatment.

SUMMARY OF THE INVENTION
Given the prior art, there is a need for an efficient and low cost process for the treatment of polymer flood and water flood waters. Accordingly, one object of the present invention provides for a process for the treatment of polymer flood water for subsequent reuse thereof, said process comprising subjecting the water to:
1) a mechanical separation step;

2) a fluid degassing step;

3) optionally, a second oil removal step;

4) a pH adjustment step, if necessary;

5) an electrocoagulation step;

6) an addition of chemical step for solids removal;

7) a third mechanical separation and oil removal step;

8) a multimedia filtration step; and

9) optionally, a bag filtration step.
According to another object of the present invention, there is provided a process for the treatment of polymer flood water for subsequent reuse for SAGD or CSS thermal water systems thereof, said process comprising subjecting the water to:
1) a mechanical separation step;
2) a fluid degassing step;
3) optionally, a second oil removal step;
4) a pH adjustment step, if necessary;
5) an electrocoagulation step;
6) an addition of chemical step for solids removal;
7) a third mechanical separation and oil removal step;
8) a multimedia filtration step;
9) optionally, a bag filtration step;

10) an addition of chemical for additional hardness removal;

11) a reverse osmosis step; and

12) optionally, an evaporation step to reduce waste volumes.

According to yet another aspect of the present invention, there is provided a process for the treatment of polymer flood water for use in alkaline surfactant polymer (ASP) alkaline surfactant brine polymer (ASBP) flood water, said process comprising subjecting the water to:
1) a mechanical separation step;
2) a fluid degassing step;
3) a second oil removal step;.
4) a multimedia filtration step comprising the addition of chemicals for fluid viscosity reduction, and coagulation of particles present;
5) a step of chemical addition for solids removal;
6) optionally, a fluid shearing step;
7) optionally, a water softening step by pumping the water through ion exchangers;
8) optionally, a bag filtration step; and 9) optionally, a chemical addition step to adjust the conductivity with brine.
According to yet another aspect of the present invention, there is provided a process for the treatment of polymer flood water, said process comprising subjecting the water to:
1) a blending step with at least another water from a different source;
2) a mechanical separation step;
3) a fluid degassing step;
4) optionally, a second oil removal step;
5) a pH adjustment step, if necessary;
6) an electrocoagulation step;
7) an addition of chemical step for solids removal;
8) a third mechanical separation step and oil removal step;
9) a multimedia filtration step; and 10) optionally, a bag filtration step.
Preferably, the fluid degassing step is performed by using a double loop gas bubbler. More preferably, the double loop gas bubbler comprises apertures facing downward at an angle of 45 .
Preferably, the multimedia filtration step is performed by using a ceramic media such as Macrolite .

Preferably, the mechanical separation steps are performed through the use of a cone bottomed tank or any other mechanical separation equipment such that is equipped with an oil skimmer at the top of the tank or overflow or standpipe.
Preferably, the solids removal step through the addition of chemicals such as coagulant or flocculant.
Preferably, the second oil removal step comprises the use of a single or two stage polymer packing vessel for oil adsorption such as Mycelx .
Preferably, according to the process of the present invention, the treated polymer flood water for reuse in polymer flood water has the following specification:
Element Water Spec ' . , pH 8.5¨ 10.5 Calcium <20 ppm Magnesium 100 ¨ 220 ppm Total Hardness as CaCO3 400 ¨ 800 ppm TDS 15000 - 25000 ppm H2S <50 ppm 02 < 50 ppb Sulphide <60 ppm Sodium 6000 - 9000 ppm Total alkalinity 1500¨ 2500 ppm Turbidity <100 NTU
TSS <250 ppm Iron <1 ppm =
Preferably, according to the process of the present invention, the treated polymer flood water specification shown above for reuse in polymer flood water can be recycled and retreated until the TDS reaches the desired spec target then one can add additional equipment to create the following SAGD or CSS thermal water specification for steam flooding:

Element Wafer spec PH 8.5 ¨ 10.5 Calcium <0.1 ppm Magnesium <0.1 ppm Total Hardness as CaCO3 <0.5 ppm TDS < 12000 ppm H2S Oppm 02 < 10 ppb Sulphide n/a = Sodium <9000 ppm Total alkalinity <700 ppm Turbidity <2 NTU
TSS <1 ppm Iron <0.5 ppm Preferably, according to the process of the present invention, the treated polymer flood water for reuse in alkaline surfactant polymer (ASP) or alkaline surfactant brine polymer (ASBP) has the following specification:

Elpmenr. , - Water Spec PH 7.5 ¨ 13.0 Calcium <10 ppm Magnesium <10 ppm Total Hardness as CaCO3 30 - 70 ppm TDS 8000 - 25000 ppm H2 S 0 ppm 02 < 50 ppb Sodium <8500 ppm Total alkalinity <5000 ppm Turbidity <10 NTU
TSS <20 ppm Iron <1 ppm Preferably, the process further comprises a step of polymer mixing and aging.
More preferably, the process further comprises the use of a nitrogen blanket during the step of polymer mixing and aging.
More preferably, the process comprises a step of addition of water to hydrate the polymer, said water is selected from the group consisting of: fresh water, treated saline water, treated produced water and treated blends of the waters.
Preferably, the process further comprises a step of tank gas bubbler, electrocoagulation, and multimedia filtration of the produced water, and fresh water hydration of the polymer mixing solution.
Preferably, the treated water has the following specification: pH >8.5 and <10.5 9.0; H2S <50 ppm and 02 < 50 ppb; TSS (total suspended solids) <250 ppm; and calcium ion <20 ppm.
Preferably, dependent on the water or polymer flood fluid characteristics, the alkaline surfactant polymer '15 (ASP) may be converted to an alkaline surfactant brine polymer where brine is used instead of some of the alkaline chemical to raise the fluid stream conductivity thus reducing the chemical costs for the mixture.

BRIEF DESCRIPTION OF THE FIGURES
Figure 1 is a schematic representation of the process according to a preferred embodiment of the present invention where the produced water is treated to be reused as polymer flood water.
Figure 2 is a schematic representation of the process according to a preferred embodiment of the present invention where the produced water is treated to be reused in steam assisted gravity drainage operations.
Figure 3 is a schematic representation of the process according to a preferred embodiment of the present invention where the produced water is treated to be reused in alkaline surfactant brine polymer flood water.
DETAILED DESCRIPTION OF THE INVENTION
The process according to the present invention is intended for use in treating various used waters reclaimed from operations in the oil industry, more specifically, polymer flood, SAGD and CSS thermal flood, alkaline surfactant polymer flood, and alkaline surfactant brine polymer flood waters, for their subsequent reuse.
Polymer Flood Water Treatment The polymer flood water treatment unit according to an embodiment of the present invention, may comprise an inlet mixing/solids tank with a gas bubbler; an elec.
trocoagulation unit; a solids removal/handling system; one or more multimedia filtration units; and one or more chemical injection systems.
The polymer flood water treatment unit according to another embodiment of the present invention, may comprise an inlet mixing/solids tank (with or without a gas bubbler); an electrocoagulation unit; a solids removal/handling system; one or more multimedia filtration units; and one or more chemical injection systems.
One advantage of the process according to the present invention is the removal of the residual recycled polymer from the produced water stream. Another advantage is that the pH of the water is adjusted to the optimal range for each polymer to become viscous. Yet another advantage is the removal of H2S from the polymer produced and makeup water streams. H2S and 02 have a substantial impact on polymer degradation. Moreover, there is improved safety and handling of the water system, i.e. safer for operations when there is no H2S venting from the, plant polymer injection equipment.
Another advantage of the process according to the present invention entails selective ion removal from water streams to reach the desired water specification. There is also bacteria removal from water, since bacteria consume polymer that is added to the flood water. The use of CDG gels require no bacteria if gels were to be used in the future instead of polymers. It is worthy of mention that the process according to the present invention allows for the removal of oil and grease residue from water as well as reducing the total dissolved solids (TDS) of the water each time it is processed. The intent is to have lower TDS
in the water stream for future SAGD or CSS thermal water requirements. An advantage according to one aspect of the present invention is that benign water is created which, in turn, leads to savings on materials for construction of pipelines and polymer hydration and injection facilities. Other advantages include the creation of a stable polymer created when using a treated water stream; solids removal from water streams - incoming solids from makeup waters i.e. grosmont solids handled at one location versus the multiple solids deposition locations; and ability to blend the polymer produced water and makeup water streams prior to treatment system ¨ optimized with mixing.
The H2S and 02 reaction consumes polymer very aggressively and we found that by reducing or removing the H2S from the fluid this reaction does not occur so rapidly, therefore one is capable of reducing the amount of polymer usage with lower H2S in the fluid.
Another advantage of the treatment process according to an embodiment of the present invention is the reduction ranging up to 850 to 1000 ppm of polymer required for flood water.
Another advantage of the treatment process is the removal or deactivation of the NORMS (naturally occurring radioactive materials) that are present in the sour saline grosmont water stream. The treatment process removes the norms from the water precipitating with the solids sludge stream that is created. This makes the effluent treated water stream safer for handling for operations and will decrease the norms contamination levels of the downstream equipment. This also makes the sludge disposal costs cheaper as it costs 6 times more to dispose of NORMS contaminated sludge.
Polymer Flood Water Specification The water specification for polymer hydration was determined through field pilot scale testing at a rate of 275 m3/day.

One of the benefits of having determined a polymer flood water specification is to optimize the polymer consumption to meet the desired viscosity targets with the least amount of polymer use. Another benefit is the determination of optimal pH range for the polymer to function most efficiently. It also allows the analysis of other water sources and the determination of the most appropriate water treatment process required to allow the water to be used in the polymer systems. Further, it allowed the determination of the factors having the greatest impact on polymer loading, such as calcium content, pH, H2S, 02, and solids content. An advantage of having determined a polymer flood water specification allowed reaching a reduction in polymer usage ranging from 850 to 1000 ppm for floodwater uses.
Polymer Flood Water Pilot in a pilot trial that was conducted, the five (5) main water streams were tested in multiple equipment configurations to achieve electrocoagulation and filtration/chemical treatment during the pilot were Grand Rapids, Quaternary, Sour Saline Grosmont, North Brintnell 7-27 produced water and a 50/50 blend of the sour saline grosmont and produced water streams. Polymer 'loading prior to the implementation of embodiments according to the present invention averaged 2200 ppm.
The pilot allowed to determine a water specification for polymer flooding activities and helped in finding a more economical water treatment process that provided lower polymer loading.
Elemental analytical results from the electrocoagulation testing were analyzed to determine the impact of each element on the polymer loading.
The following desired or preferred water specification for polymer floodwater was determined as a result of the pilot conducted:

' Element Water Spec pH 8.5 ¨ 10.5 Calcium <20 ppm Magnesium 100 ¨ 220 ppm Total Hardness as CaCO3 400 ¨ 800 ppm TDS 15000 - 25000 ppm 142S <50 ppm 02 < 50 ppb Sulphide <60 ppm Sodium 6000 - 9000 ppm Total alkalinity 1500 ¨2500 ppm Turbidity <100 NTU
TSS <250 ppm Iron < 1 PPm For the Brintnell waters tested, it was determined that the following parameters impacted the polymer loading the most:
- pH 5_ 9.0 or pH > 10.5, had an impact of about 200 - 300 ppm polymer loading increase H2S and 02 reaction, - H2S > 50 ppm and 02> 50 ppb, had an impact of about 400 -800 ppm polymer loading increase - solids - TSS (total suspended solids) > 250 ppm, had an impact of up to 500 ppm in polymer loading increase - calcium ion > 20 ppm, had an impact of up to 400 - 500 ppm in polymer loading increase.
- Total hardness level of 0 ppm (no calcium or magnesium present) ¨ increased the polymer loading by 200¨ 300 ppm.
From the trial results, it was determined that tank gas bubbler followed by electrocoagulation (EC) water treatment process then followed by multimedia filtration (MMF) provided optimal efficiency with respect to polymer loading in comparison to all other configurations. The combination of tank gas bubbler/EC,/MMF decreased polymer loading up to 1050 ppm range on all waters tested, when all fluids were adjusted to a pH range of 9.0 - 9.5.
Three other process steps resulted in improved polymer loading. The savings noted for each individual process enhancement cannot be necessarily combined for cumulative savings.
These three other processes involved a gas bubbler, a nitrogen blanket, and fresh water for mother solution hydration. The utilization of a gas bubbler in the water inlet tank to degas out the gases H2S and CO2 from the water resulted in polymer loading savings of up to 400 ppm. The use of a nitrogen gas blanket on the polymer mixing and aging tank in polymer injection skid resulted in polymer loading savings of up to 300 ppm. The use of fresh water to hydrate the polymer mother solution resulted in an additional polymer loading savings of up to 300 ppm.
Cumulatively, when creating the overall required polymer water specification mixture for injection, the testing found that one could also use treated water blended with some fresh water (with tank gas bubbler/EC/MMF treated water being used for the blend water and fresh water being used for polymer mother solution hydration) resulted in an additional 175 ppm in polymer savings - from 1050 ppm down to 875 ppm polymer loading A separate system containing only filtration and chemicals was also tested for comparison to the tank gas bubbler/electrocoagulation/multimedia filtration unit. Filtration and chemicals provided polymer reduction but this reduction was lower at around 400 ppm. Although this alternate system was very effective as the filtration and chemical treatment utilizing ceramic Macroute media with chlorine and sulphite added were able to break up and remove the oil and grease, polymer, and solids from the waters effectively and reduced turbidity of the waters.
Additionally, for direct comparison to the electrocoagulation unit, the use of Dow RSC resin was tested to see if could remove NORMS with the resin product in a filter vessel. The Dow resin tested allowed for the reduction of radium levels in the waters by 36 to 59 % removal of inlet to outlet stream.
The process according to the present is described with reference to specific embodiments illustrated in Figures 1 ¨3.

Example 1 - Polymer Flood Water Treatment Process A preferred embodiment of the present invention relates to the treatment of polymer flood water used in oilfields. It will be better understood by referring to Figure 1. There is provided a process where:
1) Polymer flood water flows (5) into a cone bottomed storage tank (10) (or other mechanical separation equipment which may be equipped with an oil skimmer at the top of the tank or overflow or oil removal standpipe) where the solids (16) are removed from fluid as needed; and the oil (17) is skimmed off of the storage tank (10) as needed.
2) When the resulting fluid (15) shows signs of being sour (H2S is present), it flows into a tank which is equipped with a double loop square gas bubbler inside (20) and gas (23) (like natural gas) is bubbled into the storage tank fluid reservoir as the fluid flows in/out of the tank (20). This permits the stripping out of H2S and other gases (27) present in the fluid.
Natural gas volume is added at a 1 to 1 ratio to the fluid offgas volume.
3) If the resulting fluid (25) requires additional oil removal prior to water treatment then a single or two stage polymer packing vessel (30) for oil adsorption (37) are used (like Mycelxe).
= 4) If the resulting fluid's (35) oil and grease level is sufficient, then the fluid (35) is pumped and undergoes a pH adjustment (40)(if necessary) where the pH is raised in the fluid by adding a chemical (like caustic - sodium hydroxide (43)).
5) The fluid (45) is then sent through an electrocoagulation unit (50) ¨ a closed cell design (like Waveionics ) this prevents gases from being released into the atmosphere during the step. The electrocoagulation step consists of metal plates with electrodes that are electrified as the fluid passes through the cell. During the step of electrocoagulation, the metal plates are consumed and the metal precipitates with the water solids (57).
6) Subsequently, there is another step of chemical addition (60) where additional chemicals (63) like caustic and coagulant, are added to the fluid (55) to assist with solids removal (67) by further raising the pH and promoting precipitation or agglomerating the particles 7) If necessary, the fluid (65) undergoes another step of bulk solids removal stage (70Xwith a cone bottomed tank and/or solids clarifier) is performed with oil recapture (77) if applicable.
8) The resulting fluid (75) is sent to a cone bottomed tank (80) for surge volume and additional solids removal (86) and oil capture (87), if applicable.
9) The resulting fluid (85) is then pumped through multimedia filtration (90)(like ceramic media such as Macrolite ) in single or double filtration stages removing solids, oil and polymer (97).

10) If fine micron particle size is required then the fluid (95) is sent through bag filtration units (100) in single or double follows the multimedia filtration with filtration bags (such as 3M DuoFLO
followed by absolute 3M pillow bags) 11) The resulting fluid (105) is then sent into storage tanks (110) for further use.
12) From the storage tank the treated fluid may be pumped and sent to a main blend line and may also be sent to the polymer mixing system.

13) A polymer mixing system is typically used to create a thick mother solution and utilizes a softened fresh, raw fresh or treated produced water supply for the hydration of the polymer prior to being blended into the main blend fluid stream.

14) The combined polymer water and blend water is then mixed to the desired viscosity and is injected into the wellbore.
It is preferable to use solids capture and separation system (such as, but not limited to, cone bottom tanks) so that solids can be removed from the water during the process.
The treated water to be used from storage tanks to send backwash water to the filtration units and water treatment as required must preferably meet the desired backwashing and water properties for treatment.
Preferably, gas blanketing is desired on the process tanks and vessels to ensure that there is no oxygen ingress into the fluid.
A tank vapour recovery system is preferred to capture the offgases from the process.
A tank gas bubbler as used in step 2) of the treatment process above (and in examples 2 and 3) was used in the inlet tank to degas the gases from the water requiring treatment.
The tank square double loop gas bubbler used in the treatment of polymer flood water was made of linear tubing the loops overlapping each other and positioned in an horizontal plane, comprising holes positioned to be at a 450 downward angle towards the walls of a tank in which it is inserted. It has been determined by the inventor that the above specification would allow for the optimal removal, from the waters to be treated, of H2S present and other gases which have deleterious effects on polymers used in polymer flood waters.

The tank gas bubbler used in the treatment of polymer flood waters allows to effectively remove the 112S
from the grosmont and produced waters which, in turn, improves the polymer loading for subsequent polymer flood treatment. This leads to savings in polymer usage to meet viscosity target.
The tank gas bubbler can be used for any water fluid requiring H2S removal from system ¨ and it greatly improves the downstream safety of fluid handling with reduced H2S levels.
Another advantage of the tank gas bubbler is that the installation is simple and cost efficient and can be adapted to accommodate wide ranges of water : gas rates. The piping sizes can vary when used in this design to meet the rigorous process conditions and be adapted for any tank size. It is worth noting that the process controls based on water flow to gas flow rates ratio control program.
The use of a tank gas bubbler can lead to reductions in polymer usage for subsequent polymer flooding activities ranging from 100 to 400 ppm when conducting polymer flood water operations.
The spacing between apertures on the tubing and the size of the apertures is dependent on the tank size (i.e. total volume) as well as the type of liquid being treated (i.e. the content of gas to be extracted) and the flow rate of the gas being used in the operation. =
Example 2 ¨ Steam Assisted Gravity Drainage (SAGD) or Cyclic Stimulation Steam (CSS) Thermal Water from Polymer Flood Water Treatment If the TDS of the polymer flood returns water has reduced to the desired levels after treating the fluids with the process discussed in Example 1 then additional equipment can be added downstream of the process to make the water acceptable for thermal steam flood usage. The desired or preferred water specification for thermal steam flood usage is set out below:
Element ' - Water Spec ' pH 8.5 ¨ 10.5 Calcium <0.1 ppm Magnesium <0.1 ppm Total Hardness as CaCO3 <0.5 ppm TDS < 12000 ppm H2S 0 ppm 02 < 10 ppb Sulphide n/a Sodium <9000 ppm Total alkalinity <700 ppm Turbidity <2 NTU
TSS <1 ppm Iron <0.5 ppm According to a preferred embodiment of the process of the invention, there is provided a process to prepare Steam Assisted Gravity Drainage (SAGD) or Cyclic Steam Stimulation (CSS) thermal water from polymer flood water treatment. It will be better understood by referring to Figure 3. The process comprises the following steps where:
1) Process fluid (5) recovered from polymer flood activities flows into a cone bottomed storage tank (10) (or other mechanical separation equipment equipped with an oil skimmer at the top of the tank) where the solids (16) are removed from fluid as needed; and oil (17) is skimmed off from the storage tank as needed.
2) When the resulting fluid (15) shows signs of being sour (H2S is present), the tank is equipped with a double loop square gas bubbler inside (20) and gas (23Xlike natural gas) is bubbled into the storage tank fluid reservoir as the fluid flows in/out of the tank. This permits the stripping out the H2S and other gases (27) present in the fluid. Natural gas volume is added at a 1 to 1 ratio to the fluid offgas volume.
3) Then, follows a step of oil removal (30) prior to water treatment ¨ fluid (25) flows through a single or two stage polymer packing vessel(s) for oil adsorption/coalescence (37) if such step is necessary required (like Myceix ) there is recovery of an oil stream.
4) If the resulting fluid's (35) oil and grease level is sufficient, then the fluid (35) is then pumped and the pH is raised in the fluid by adding a chemical (like caustic - sodium hydroxide (43)) if pH
adjustment (40) is needed.
5) The fluid (45) is then sent through an electrocoagulation unit (50) ¨ a closed cell design (like Waveionics ) this prevents gases from being released into the atmosphere during the step. The electrocoagulation step consists of metal plates with electrodes that are electrified as the fluid passes through the cell. The metal plates are consumed and the metal precipitates with the water solids (57).
6) Then, what follows is another step of chemical addition (60) where additional chemicals (63) like caustic and coagulant, are added to the fluid (55) to assist with solids removal (67) by further raising the pH and promoting precipitation or agglomerating the particles 7) Then, a chemical addition step is performed (370) where a chemical (like phosphate or lime)(373) is added to the fluid (65) to remove additional hardness (calcium and magnesium) (377) not removed by the electrocoagulation step above.
8) The fluid (375) then undergoes a bulk solids removal stage (380)(through the use of a tank like a cone bottomed tank and/or solids clarifier) where solids (386) are removed and oil (387) is recaptured, if applicable.
9) If necessary, the fluid (385) undergoes another bulk solids removal stage (390Xthrough the use of a tank like a cone bottomed tank and/or solids clarifier) where solids (396) are removed and oil (397) is recaptured.
10) The resulting fluid (395) is then pumped through multimedia filtration step (400)(like ceramic media Macrolite ) in single or double filtration stages 11) If fine micron particle size desired is not attained, then the fluid (405) is sent through bag filtration units (410) in single or double with filtration bags (like the nominal 3M DuoFLO
followed by absolute 3M pillow bags).
12) After filtration, the resulting fluid (415) will undergo a double pass reverse osmosis (420) which is performed with membranes in series. The waste stream, concentrated RO
reject, from the RO
system then needs to go to an evaporator to remove the contaminants, like alkalinity and silica, and reduce the overall waste volume. The resulting fluid (425) then flows into storage tanks (430) for future usage such as to make steam.
Alkaline Surfactant Polymer (ASP) or Alkaline Surfactant Brine Polymer (ASBP) Flood Water Treatment The following desired or preferred water specification for alkaline surfactant polymer (ASP) or alkaline surfactant brine polymer (ASBP) flood water was determined from laboratory small scale fluid testing and was further implemented onsite:

Element . Water Spec':
pH 7.5 ¨ 13.0 Calcium <10 ppm Magnesium <10 ppm Total Hardness as CaCO3 30 - 70 ppm TDS 8000 - 25000 ppm 112S Oppm 02 < 50 ppb Sodium <8500 ppm Total alkalinity <5000 ppm Turbidity <10 NTU
TSS <20 ppm Iron <1 ppm The site produced water was treated with oil removal system and water treatment system as listed below in Example 3.
The goal was to confirm the water specification for alkaline surfactant polymer (ASP) or alkaline surfactant brine polymer (ASBP) flooding activities determined in laboratory and help in finding a more economical water treatment process. It is estimated that the use of a process of treating ASP or ASBP
polymer flood produced water prior to its reuse in for the same purpose can yield reductions ranging from 200 to 400 ppm in the polymer usage on large scale projects.
Alkaline Surfactant Polymer (ASP) or Alkaline Surfactant Brine Polymer (ASBP) Flood Water Spec The alkaline surfactant polymer (ASP) or alkaline surfactant brine polymer (ASBP) water specification for polymers for hydration was determined through field pilot scale testing at a rate of 450 m3/day.
According to an embodiment of the present invention, the alkaline surfactant polymer (ASP) or alkaline surfactant brine polymer (ASBP) flood water treatment unit comprises: a tank gas bubbler, a Mycelx oil water separator; a Mycelx backwash vessel; at least one multimedia filtration unit (more preferably, in double train of dual multimedia filter vessels in series); a double train primary/polisher strong acid cation ion exchange vessels with brine and caustic reagent step, and one or more of chemical injection systems.
Some advantages of using the process according to the present invention for the preparation of an alkaline surfactant polymer (ASP) or alkaline surfactant brine polymer (ASBP) flood water include; the removal of H2S and other gases like CO2 by the tank gas bubbler (optional);
the removal and recovery of oil from the ASP or ASBP polymer produced water stream and the creation of a sales oil stream with the MyceIxe green polymer packing technology vessels (OWS and BW) - revenue from sales oil stream; the removal of the solid particles from the water stream with filtration; the removal of the hardness from the water with strong acid cation resin exchangers down to 5 ¨ 10 ppm leakage (designed for some hardness leakage); the removal of the polymer, silicates, and oil and grease from the strong acid cation resin and multimedia filters with the addition of a caustic regeneration cycle step ¨ to remove key foulants of other ASP polymer flood systems resins and medias; the savings on polymer loading, facilities and downhole scaling of lines and injection wells which translates into less downtime and less wellbore workover costs;
and the reduced cost of softening ¨ i.e. SAC/SAC regeneration with caustic step added to the brine step is cheaper than currently used WAC (weak acid cation) regeneration chemicals of acid and caustic; and the creation of a liquid waste to be disposed of from strong acid cation ion exchange softeners versus other technologies that may create a solids waste and liquid waste to deal with.
It is estimated that the use of a process of polymer flood water according to the present invention can yield reduction in 200 to 400 ppm of polymer usage which is substantial given the cost of polymer and the amounts of water treated. These savings can amount to several million dollars yearly on a large scale project.
By having an optional chemical addition step at the end of the water treatment process one can adjust the conductivity of the fluid with brine to reduce amount of alkaline required for best surfactant activity.
The way to pretreat ASP or ASBP polymer flood water according to an embodiment of the present invention, allows one to utilize produced water for polymer mixing and reinjection versus disposal and using makeup waters.
Example 3 ¨ Alkaline Surfactant Polymer (ASP) or Alkaline Surfactant Brine Polymer (ASBP) Flood Water Treatment According to another preferred embodiment of the process of the invention, there is provided a process to prepare an alkaline surfactant polymer (ASP) or an alkaline surfactant brine polymer (ASBP) flood water.
It will be better understood by referring to Figure 2. The process comprises the following steps where:
1) Process fluid (5) recovered from polymer flood activities flows into a cone bottomed storage tank (10) (or other mechanical separation equipment equipped with an oil skimmer at the top of the tank) where the solids (16) are removed from fluid as needed; and oil (17) is skimmed off from the storage tank as needed.
2) When the resulting fluid (15) shows signs of being sour (H2S is present), the tank is equipped with a double loop square gas bubbler inside (20) and gas (23Xlike natural gas) is bubbled into the storage tank fluid reservoir as the fluid flows in/out of the tank. This permits the stripping out the I-12S and other gases (27) present in the fluid. Natural gas volume is added at a 1 to 1 ratio to the fluid offgas volume.
3) Then, follows a step of oil removal (30) prior to water treatment ¨ fluid (25) flows through a single or two stage polymer packing vessel(s) for oil adsorption/coalescence (37) if such step is necessary (like Mycelx ) ¨ there is recovery of an oil stream.
4) The fluid (35) is then pumped through multimedia filtration (90)(like ceramic media Macroute ) in single or double filtration stages:
a. Oxidant Chemical (91)(like bleach) is added upfront of filters to reduce fluid viscosity (destroy the remaining polymer) and to kill bacteria;
b. Coagulating Chemical (92Xlike polyaluminum chloride PAC) is added upfront of filters to coagulate particles ¨ which aids in the filtration; and c. Reducing Chemical (93)(like sulphite) is added in downstream of first filter (upfront of second filter) to remove the oxidant chemical residuals (i.e. consume the bleach, if present);
d. There is a filter backwash step to include an additional step of addition of alkaline chemical (94)(like caustic) for polymer, silica, and oil removal from the filtration media;
5) Then, the fluid (115) passes through a shearing stage (120) of a inline static mixer followed by a inline jet nozzle and into a storage tank;
6) Then, the fluid (125) is pumped through anion exchangers (130), two strong acid cation resin vessels in series called SAC/SAC, a. Due to the higher fluid total dissolved solids, the SAC/SAC is designed to leak from 5 ppm to 10 ppm hardness (calcium and magnesium) in effluent - to not achieve normal 0 ppm hardness leakage.

b. Optionally, it has an additional alkaline chemical injection step (like caustic) as part of the regeneration cycle ¨ the alkaline chemicals are being utilized to remove polymer, silica, and oil from the strong acid cation resin beads.
7) In the event that fine micron particle size is desired, then the fluid (135) flows through bag filtration units (100) in single or double will follow the anion exchangers (130) with filtration bags (like the nominal 3M DuoFLOe followed by absolute 3M pillow bags) 8) The resulting fluid 145 is then sent into a storage tank (140).
9) From the storage tank (140), the fluid (145) is pumped and chemicals 143 (like caustic, surfactant, brine, and polymer) are added to create the required alkaline surfactant polymer (ASP) or alkaline surfactant brine polymer (ASBP) mixture (155) to be injected downhole. In alkaline surfactant brine polymer (ASBP), the brine is added to increase the conductivity and reduce the alkaline volume required for the overall alkaline surfactant brine polymer mixture.
10) A polymer mixing system (150) is used to create a thick mother solution and utilizes a softened fresh (175), raw fresh or treated produced water supply (5) for the hydration of the polymer (165) prior to being blended into the main chemical fluid stream (155).

Claims

1. A process for the treatment of polymer flood water for subsequent reuse thereof, said process comprising subjecting the water to:
2) a mechanical separation step;
3) a fluid degassing step;
4) optionally, a second oil removal step;
5) a pH adjustment step, if necessary;
6) an electrocoagulation step;
7) an addition of chemical step for solids removal;
8) a third mechanical separation and oil removal step;
9) a multimedia filtration step; and 10) optionally, a bag filtration step.

2. A process for the treatment of polymer flood water for subsequent reuse in thermal water systems thereof, said process comprising subjecting the water to:
1) a mechanical separation step;
2) a fluid degassing step;
3) optionally, a second oil removal step;
4) a pH adjustment step, if necessary;
5) an electrocoagulation step;
6) an addition of chemical step for solids removal;
7) a third mechanical separation and oil removal step;
8) a multimedia filtration step;
9) optionally, a bag filtration step;
10) an addition of chemical for additional hardness removal;
11) a reverse osmosis step; and 12) optionally, an evaporation step to reduce waste volumes.

3. A process for the treatment of polymer flood water for subsequent reuse in alkaline surfactant brine polymer flood water, said process comprising subjecting the water to:
1) a mechanical separation step;
2) a fluid degassing step;
3) a second oil removal step;

4) a multimedia filtration step comprising the addition of chemicals for fluid viscosity reduction, and coagulation of particles present;
5) a step of chemical addition for solids removal;
6) optionally, a fluid shearing step;
7) optionally, a water softening step by pumping the water through ion exchangers;
8) optionally, a bag filtration step; and 9) optionally, a chemical addition step to adjust the conductivity with brine.

4. A process for the treatment of polymer flood water for subsequent reuse thereof, said process comprising subjecting the water to:
1) a blending step with at least another water from a different source;
2) a mechanical separation step;
3) a fluid degassing step;
4) optionally, a second oil removal step;
5) a pH adjustment step, if necessary;
6) an electrocoagulation step;
7) an addition of chemical step for solids removal;
8) a third mechanical separation step and oil removal step;
9) a multimedia filtration step; and 10) optionally, a bag filtration step.

5. The process according to any one of claims 1 to 2, wherein the fluid degassing step is performed by using a double loop gas bubbler.

6. The process according to claim 5, wherein the double loop gas bubbler comprises apertures facing downward at an angle of 45°.

7. The process according to any one of claims I to 4, wherein the multimedia filtration step is performed by using a ceramic media such as Macroute®.

8. The process according to any one of claims 1 to 4, wherein the mechanical separation steps are performed through the use of a cone bottomed tank or another mechanical separation equipment such that is equipped with an oil skimmer at the top of the tank or overflow.

9. The process according to any one of claims 1 to 4, wherein the solids removal step through the addition of chemicals such as coagulant or flocculant.

10. The process according to any one of claims 1 to 4, wherein the second oil removal step comprises the use of a single or two stage polymer packing vessel for oil adsorption such as Mycelx®.

11. The process according to claim 1 or 2, wherein the treated polymer flood water has the following specification:
Element Water Spec pH 8.5 ¨ 10.5 Calcium <20 ppm Magnesium 100 ¨ 220 ppm Total Hardness as CaCO3 400 ¨ 800 ppm TDS 15000 - 25000 ppm H2S <50 ppm O2 < 50 ppb Sulphide < 60 ppm Sodium 6000 - 9000 ppm Total alkalinity 1500 ¨ 2500 ppm Turbidity <100 NTU
TSS <250 ppm Iron < 1 ppm

12. The process according to claim 1 or 2, wherein the treated polymer flood water has the following specification:
Element Water Spee pH 8.5 ¨ 10.5 Calcium <0.1 ppm Magnesium <0.1 ppm Total Hardness as CaCO3 <0.5 ppm TDS < 12000 ppm H2S 0 ppm O2 < 10 ppb Sulphide n/a Sodium < 9000 ppm Total alkalinity < 700 ppm Turbidity <2 NTU
TSS <1 ppm Iron < 0.5 ppm

13. The process according to claim 3, wherein the treated polymer flood water has the following specification:
Element Water-Spec PH 12.6 ¨ 13.0 Calcium <10 ppm Magnesium <10 ppm Total Hardness as CaCO3 30 - 70 ppm TDS 8000 - 25000 ppm H2S 0 ppm O2 < 50 ppb Sodium < 8500 ppm Total alkalinity < 5000 ppm Turbidity < 10 NTU
TSS <20 ppm Iron < 1 ppm

14. The process according to claim 1, further comprising a step of polymer mixing and aging.

15. The process according to claim 14, further comprising the use of a nitrogen blanket during the step of polymer mixing and aging.

16. The process according to claim 14 or 15, further comprising a step of addition of water to hydrate the polymer, said water is selected from the group consisting of: fresh water, treated saline water, treated produced water and treated blends of the waters.

17. The process according to claim 14, further comprising electrocoagulation, microfiltration of the produced water, and fresh water hydration of the polymer mixing solution.

18. The process according 1 and < 10.5; H2S < 50 ppm and 20 ppm.