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Polymer assisted water flooding – Environmental challenges for

Technical report

Polymer assisted water flooding – Environmental challenges_______________________

Project title Polymer assisted water flooding – Environmental challenges Client Petoro Date Status Project Manager Approved 01.06.11 Final Geir Husdal Andreas Østebrøt Keywords HPAM, chemical flooding Summary

1. Discharge of HPAM to sea is in conflict with the zero discharge target. No conflict exists if all produced water is re-injected in a sub surface reservoir .

2. The regulators may be open for a dialogue with the operator if the discharged amounts of HPAM are small.

3. A HPAM detection systems should should be in place having a low detection level and enable analyses done offshore. Gel Permeation Chromatography (GPC) seems to have the preferred properties.

4. More work will be required to qualify a detection system for the application. Early warning systems comprising tracer technology should be investigated and evaluated for this application.

Table of Content 1 Introduction .................................................................................................... 1 2 Regulatory requirements .................................................................................. 2 3 HPAM used in assisted water flooding................................................................. 4 4 Conceptual HPAM injection cases ....................................................................... 6

4.1 Technical arrangements ............................................................................. 6 4.2 Evaluated cases ........................................................................................ 6 4.3 Case A – Seawater as HPAM medium, produced water reinjected .................... 7 4.4 Case B – HPAM injected with seawater , produced water to sea ........................ 8 4.5 Case C – HPAM injected with produced water , excess water reinjected ............10 4.6 Case D – HPAM injected with produced water , excess water to sea .................11 4.7 Comparison of evaluated cases ..................................................................12

5 HPAM detection in produced water ....................................................................14 5.1 Analytical methods ...................................................................................14 5.2 Comparison of the analytical methods .........................................................17 5.3 Tracers ...................................................................................................17 5.4 Applicable methods and detection limits ......................................................18

6 A holistic approach to achieve zero discharges ...................................................23 6.1 General approach .....................................................................................23 6.2 Case A – HPAM injected with seawater , all water reinjected ...........................23 6.3 Case B – HPAM injected with seawater , water discharged to sea ....................23 6.4 Case C – HPAM injected with produced water , excess water reinjected ............24 6.5 Case D – HPAM injected with produced water , excess water discharged to sea .24

7 Conclusions ...................................................................................................25 References...........................................................................................................26


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1 Introduction

Use of HPAM (Hydrolyzed Polyacrylamid) in injected water increases the viscosity and so forth changes the flow pattern in the reservoir resulting in increased oil production. HPAM is not readily biological degradable and is categorized as a red chemical according to KLIF’s criteria. Discharge of red chemicals is in conflict with the zero discharge requirements in Norwegian oil and gas production. The use of HPAM as an injection chemical may therefore come in conflict with the regulatory requirements. The purpose of this study is to evaluate ways and means to prevent the HPAM polymer from being discharged to sea and thereby meeting the zero discharge requirements. The study is generic in nature. A field on the Norwegian Continental Shelf is currently evaluating such IOR methodology. The operator of the field has provided add novatech with some confidential project information. Data related to HPAM concentrations and water volumes from this information have been used as reference for calculations shown in this report. HPAM has the possibility for being discharged to sea either as a result of accidental discharges or as a part of the normal operations depending upon the conceptual arrangements selected for HPAM injection. The possibilities for operational discharges have been addressed in this report. Unplanned discharges of back produced HPAM in the produced water is also covered. Accidental discharges of HPAM during transport to and handling on the installations are not covered and assumed to be handled according to normal practices for such incidents. The following issues are raised in the study:

• Regulatory requirements

• Conceptual HPAM injection cases or scenarios

• Detection of HPAM pollution in the produced water and methods to

prevent/minimize HPAM discharges to sea


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2 Regulatory requirements

According to the HSE regulation (the Activities regulations § 62) substances shall be tested for biodegradability according to method OECD 306 Biodegradability in Seawater . Under the test conditions HPAM obtains a BOD less than 20 % and is therefore categorized as a red chemical. Red chemicals shall, according to § 65 of the Activities regulations, only be selected if they are necessary for technical and safety reasons.

The OECD test method uses seawater with its natural content of bacteria and the obtained low degradation is not unpredictable as the bacteria level is low and the bacteria are not adapted to HPAM back bone degradation. However , adaption of bacteria to HPAM degradation by production of extracellular enzymes has shown that HPAM is to a certain degree biodegradable. Aerobic degradation test of HPAM with pure strains (Plesiomonas) (ref. 6) isolated from oilfield sediments showed a degradation of 45,5 % after 5 days at 20 C o. The degradation rate decreased with increased chain length indicating that HPAM with longer chains degrades slower due to fewer attach sites per unit of weight than shorter chains (such degradation will normally occur from the two terminal sites on the carbon chain). Limitations in amounts of available enzymes were also indicated as an explanation of reduced degradation of long chains compared to shorter chains. Test with certain bacillus type bacteria has shown that they utilize HPAM as their sole carbon source in anaerobic degradation of HPAM (ref.7) Certain Bacillus cerius and other Bacillus types are found to transform amide groups to carboxylic acid utilizing nitrogen and to partly degrade the HPAM backbone. The degradation of the HPAM backbone did not give any liberation of acrylamide (ref. 8). An anaerobic degradation of 52,5 % was reported. Sulphate reducing bacteria (SRB) are also found to reduce sulphate to H2S with HPAM as their sole carbon source (ref. 10). Chemical analysis after the biological degradation showed that the amide groups were hydrolyzed to carboxylic acid groups with a following fall in the viscosity. Low molecular degradation products were found using GC-MS and shown to be fragments of the HPAM chain with duplets bonds, epoxy as well as carbonyl groups. An anaerobic degradation of 30 % was reported. Both aerobic and anaerobic degradation of HPAM, as shown, has no significant impact with respect to the environmental categorization of HPAM as it is the test results from the OECD method that gives the conclusion. However , bacterial degradation of HPAM is a significant property that needs to be addressed as it may reduce the effect during flooding due to reduced viscosity. This effect comes in addition to possible changes in HPAM due to mechanical/thermal degradation and hydrolysis of amide groups. KLIF has in its comments to the report “ Increased production from the Norwegian Continental Shelf” (”Økt utvinning på norsk sokkel”) (ref.1) expressed the following (unofficial English translation):“One of the measures mentioned in the report is chemical flooding that could result in use of large amounts of chemicals in the red category. Discharge of such chemicals will be in conflict with the zero discharge target. We will underline, however, that use of chemicals does will not come into conflict with the zero discharge target. Chemical flooding is therefore not necessarily in conflict with zero discharge if the water stream is re-injected. This will require a high injection regularity and a good well integrity. We notice that the industry consider the zero discharge target to


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prohibit chemical flooding. We are of the opinion that there could be a need for a more holistic evaluation of the use and control of certain groups of chemicals and are open for a dialogue leading to environmentally good solutions. (Original Norwegian text: ”Et av tiltakene som nevnes i rapporten, er kjemisk flømming som vil kunne medføre forbruk av store mengder kjemikalier i rød kategori. Utslipp av slike kjemikalier vil være i konflikt med nullutslippsmålet. Imidlertid vil vi understreke at forbruk av kjemikalier ikke vil komme i konflikt med nullutslippsmålet. Kjemisk flømming er derfor ikke nødvendigvis i strid med nullutslipp, dersom vannstrømmen reinjiseres. Dette forutsetter høy injeksjonsregularitet og god brønnintegritet. Vi registrerer at bransjen oppfatter at nullutslippsmålet er et hinder for kjemisk flømming. Vi mener at det kan være behov for å gjøre en mer helhetlig vurdering av bruken og reguleringen av enkelte grupper kjemikalier, og er åpen for en dialog for å komme fram til miljømessige gode løsninger”). The leads expressed above by KLIF have been the criteria used in this evaluation.


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3 HPAM used in assisted water flooding

This section gives a brief description of HPAM, its structure and how it behaves in the reservoir with respect to mechanical and chemical degradation. Effects from microbiological activity are also addressed. The changes affect the viscosity and the structure of HPAM. Changes in the HPAM structure makes is more challenging to detect HPAM in produced water .

HPAM (Hydrolyzed Poly-Acrylamide) is a polymer made of acrylamide :

acrylamide Acrylamide units form polyacrylamide:

Polyacrylamide Hydrolysis of the amide groups gives carboxylic acid groups with the liberation of ammonia, NH4

+. Hydrolyzed PAM (HPAM) contains both amide groups (-CONH2) and carboxylic groups (-COOH).

Commercial HPAM used for chemical flooding will normally have a mole weight from 5 million to 20 million and a degree of hydrolysis in the area of 20 – 30 % (percentage of amide groups hydrolyzed of all amide groups). If the degree of hydrolysis is 100 % then all amide groups have been hydrolyzed and we have a polyacrylic acid (PAA 1), if the degree is 0 then we have a true polyacrylamide (PAM). HPAM disperses in water and swells giving a viscous fluid and it is this property that makes HPAM a favorable flooding agent. In the reservoir the HPAM solution will be exposed to high temperatures, high pressure, shear-stress, dissolved salts, H2S, bacterial activity, oxygen and added chemicals and it will gradually degrade over time with a reduction in viscosity as a consequence. The degradation will follow two different paths (ref. 4, 5)

1 PAA is produced from acrylic acid, the example given is only for illustration


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• Degradation of the carbon back-bone giving shorter chains due to thermal oxidation, mechanical stress during injection and bacterial activity in the reservoir .

• Laboratory data shows that hydrolysis of amide groups are mainly dependant on temperature and pH and independent of the ionic composition and oxygen content.

The degradation as a whole will depend on the reservoir conditions and the flow regime. A reduction up to 10 times in mole weight and an increased degree of hydrolysis in the range of 2 – 3 times has been reported for HPAM in produced water (ref. 5).

Shortening of the HPAM chain will give reduced viscosity. Increased degree of hydrolysis may initially increase the viscosity but will, as the hydrolysis increases further , give a reduction in the viscosity. HPAM will also be affected by divalente ions. Concentrations over 200 mg/l of Ca2+ and Mg2+ can precipitate HPAM from the solution as lower levels may block the carboxylic acid groups giving a reduced viscosity. HPAM that follows the produced water separated out in the production facilities will consequently not necessarily be identical with the product injected. In addition to the original polymer one should expect shorter chains of the polymer , original chains and shorter chains with increased number of carboxylic groups, smaller molecules with changes in structure compared to the backbone. In addition to this is it feasible that the various molecules arising from the degradation of HPAM may separate during wandering due to different adsorbtion effects in the formation and reach a wellhead at different times (ref. 4). This implies that any HPAM found in the produced water cannot be expected to be identical with the product injected. Furthermore the composition of “returned HPAM” may change over time due to a chromatographic effect in the reservoir . This is challenging with respect to the detection of HPAM in produced water .


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4 Conceptual HPAM injection cases

4.1 Technical arrangements The amount of HPAM to be used is rather voluminous. A typical concentration is 1000 ppm which equals 1000 tonnes HPAM per million m 3 of injected water . The discharge of red chemicals on the NCS in 2009 was 21 tonnes, ref. 1, and the yearly average consumption of red chemicals the last four years is about 4 500 tonnes. Thus the introduction of HPAM on the NCS will result in a significant increase in the consumption of red chemicals, and one should consider taking severe measures to prevent HPAM discharge. The HPAM can be transported from shore to the offshore installation as a concentrated solution or as a powder to be mixed with water to a concentrated stock solution offshore. The stock solution is added to the large amounts of water prior to injection into the well. The mixing of water into the concentrated liquid will require space for storage and handling of the HPAM and the HPAM solution. If space is available on the production installation, HPAM storage, mixing and injection can take place there. If space is limited, HPAM storage and mixing can take place on a connected support vessel. This solution will require hose transfer of HPAM solution from the support vessel to the production installation. Pretreatment of the chosen injection medium for HPAM is considered to be outside of the scope of work, i.e. necessary seawater or produced water filtration arrangements to reach acceptable low hardness and low TDS (total dissolved solids) levels is considered not part of this study together with ordinary produced water treatment prior to discharge.

4.2 Evaluated cases The technical conditions and facilities on an oil production installation will vary. Several options may therefore be available for injecting and controlling the HPAM. For this reason four (4) conceptually different cases for injection and control of HPAM are identified and evaluated:

Case A: HPAM injected with sea water , all produced water is reinjected or disposed of in a subsurface reservoir

Case B: HPAM injected with sea water , all or parts of the produced water is discharged to sea

Case C: HPAM injected with produced water , all produced water reinjected or disposed of in a subsurface reservoir

Case D: HPAM injected with produced water , parts of the produced water is discharged to sea

It is believed that these cases to a large extent will cover most, if not all of the options open for an operator . Combination of these cases can be foreseen, but the challenges and possible solutions are well described with these four cases.


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4.3 Case A – Seawater as HPAM medium, produced water reinjected

a. Case definition and description

The HPAM solution can be injected either upstream or downstream of the sea water injection pump. Potential injection points are illustrated in the conceptual drawing in Figure 1.

Seawater li ft pump

Booster pump Water injectionpump

HPAM injectionpump

HPAM storagetank

Injection water w/HPAM

B

Sea water treatment pkg.

A

Produced oil

Produced water treatment package Produced water

injection pump

Produced water disposal

Figure 1 Case A – Seawater as HPAM medium. Injection of produced water. All produced water is treated according to standard produced water treatment procedures prior to being re-injected into the reservoir or disposed in a substructure recipient. The system would have to be set up such that no sea water containing HPAM is being discharged overboard in case of a pump failure. Such set up can easily be arranged with this concept using standard instrumentation. This arrangement will ensure that HPAM that potentially will reach a production well and be back produced will be reinjected into the reservoir or another safe substructure with no discharges to sea. Two injection schemes for the produced water handling are foreseen:

a. Disposing the produced water in a sealed formation with no effects on the producing reservoir . This scheme will not cause any accumulation of HPAM in the circulated water .

b. Injecting the produced water in the reservoir water phase to enhance oil production. This scheme may enable the HPAM together with reinjected water to repeat its recirculation and potentially accumulate in the loop.

b. Case evaluation In this case both seawater and produced water need to be pressurized before injection. This result in increased energy demand and resulting emissions to air compared with discharge of produced water to sea.


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Case A will function as a sealed system, with no operational discharges to sea. This solution provides the following barriers against discharges of HPAM:

1. The technical solution provides a solid barrier against discharges of water containing HPAM since all produced water that may contain HPAM is reinjected or disposed of into a subsurface structure. Only accidental discharges can occur .

2. A produced water HPAM warning and detection system can be implemented to enable well shutdown in case of pump failure and HPAM warning and detection.

3. Shut down of producing well(s) following detection of HPAM water in the produced water in case the produced water injection pump(s) fails to operate.

The following situations that could result in accidental discharges may occur: Table 1 Possibilities for accidental HPAM discharges and mitigation option

Situation Impact Mitigation measures Sea water injection pump stops

Seawater from lift pump discharged to sea

1. The outlet for sea water overboard to be located upstream of injection point.

2. HPAM injection pump to be automatically stopped if the seawater injection pump stops in order to avoid accidental discharge of seawater with 1000 ppm HPAM.

Produced water injection pump stops. No HPAM detected in produced water

Produced water accidentally discharged overboard upstream of injection pump Minor amounts of undetected HPAM in the produced water could be discharged to sea

1. The produced water treatment plant to have two parallel produced water injection trains.

2. Shut down of well(s). 3. Routing the most exposed production wells via the test

separator would reduce the cost of well shutdown and would improve the detection possibilities.

Produced water injection pump stops. HPAM detected in produced water

Produced water accidentally discharged overboard upstream of injection pump. Smaller amounts of HPAM in the produced water would be discharged to sea

1. The produced water treatment plant to have two parallel produced water injection trains.

2. Shut down of well(s) 3. Routing the most exposed production wells via the test

separator would reduce the cost of well shutdown and would improve the detection possibilities.

4.4 Case B – HPAM injected with seawater, produced water to sea


The injection of HPAM into the carrying sea water will be identical to Case A. It is the handling of the produced water that differs. The arrangement is illustrated in Figure 2.


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Seawater l i ft pump

Booster pump Water injectionpump

HPAM injectionpump

HP AM storagetank


B

Sea water treatment pkg.

A

Produced oi l

Produced water treatment package

Produced water to sea

Figure 2 Case B – Seawater as HPAM medium. Produced water to sea.

b. Case evaluation If injection water containing HPAM penetrates the reservoir and enters into the produced well stream, HPAM will follow the produced water through the produced water treatment system and thereafter be discharged to sea. The only barriers that could reduce and eventually stop the discharges of HPAM to sea in this case is a HPAM warning and detection system initiating the producing well(s) to be shut down in case of HPAM breakthrough. The discharges of HPAM to sea will violate the zero discharge principle as a consequence. The amounts of HPAM being discharged depends on the concentration in the produced water , the rate of HPAM concentration build-up and the ability and the time it takes to detect the HPAM in the produced water and to shut down the producing well(s). Routing the streams from the well(s) most exposed to HPAM breakthrough through the test ttseparator could reduce the amounts of HPAM being discharged prior well shut down as well as it might improve the possibility for early HPAM detection. Such an arrangement will require HPAM detection to be applied for the produced water from the test separator as well as from the production separator (depending upon field specific well arrangement). Good HPAM detection techniques enabling to detect low HPAM concentrations, having rapid analyzing time and suitable for offshore application is essential for this case. Compared with case A this solution is less energy demanding, since produced water injection is avoided. The possibilities for and mitigation measures applicable to prevent accidental discharges of HPAM are:


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Table 2 Possibilities for accidental HPAM discharges and mitigation option Situation Impact Mitigation measures Sea water injection pump stops

Seawater from lift pump discharged to sea

1. The outlet for water overboard to be located upstream of injection point.

2. HPAM injection pump to be automatically stopped if the seawater injection pump stops in order to avoid accidental discharge of seawater with 1000 ppm HPAM.

4.5 Case C – HPAM injected with produced water, excess water reinjected


This case is similar to case A, but with produced water used as the HPAM carrying medium. As in case A. all produced water is re-injected. If the available amounts of produced water are inadequate to meet the needs for HPAM injection, sea water is assumed to make the balance. If the amounts of produced water exceed the demand for HPAM injection, the surplus is assumed to be re-injected either in the producing formation or in a disposal formation. The set-up is shown in Figure 3.

Booster pumpW ater injectionpump

HPAM injectionpump

HP AM storagetank


B

Injection water treatment pkg.

A

Produced oi l

Produced water disposal

Excess produced water

Concentrate

Figure 3 Case C - Produced water as HPAM medium. Disposal of excess produced water.


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b. Case evaluation This case is equivalent to Case A with regards to prevention of HPAM discharges to sea. During normal production the zero discharge principle is met, with no HPAM being discharged to sea. However , using produced water as the carrying medium for HPAM may introduce operational challenges beyond those that will be experienced using sea water .

• The characteristic of the produced water will be dependent on the field and well. This might have an influence on the water treatment system, and could ultimately result in lower regularity than for Case A. This could lead to higher probability of produced water bypassing the filtration and pumping units and being discharged to sea, resulting in discharges of HPAM following a breakthrough into producing well(s).

• Since only produced water is injected in this case, the energy demand is less than

for Case A. However , since one might expect higher hardness and TDS levels in the produced water compared to seawater , the filtration process would most likely be more energy intensive.

• If breakthrough of HPAM, produced water will be contaminated with HPAM, and thus the feed stream to the injection water treatment package. This back produced HPAM will most likely end up in the concentrate solution in the membrane system. To assure that this HPAM is not discharge to sea, concentrate needs to be managed and most likely re-injected or brought to shore to comply with the zero discharge target.

• Conditioning of the produced water by filtration in order to reduce the hardness and salinity will produce a concentrate that eventually also may contain HPAM. It is not likely that this concentrate can be disposed by discharge to the sea, reinjection or injection into a sealed reservoir may be the only acceptable solution, since the volume may be too high to enable it to be collected and shipped ashore for treatment.

A consequence is that operational problems with the produced water treatment facilities and filters/membranes may be experienced, leading to increased risk for shorter period shut-downs compared to Case A. Such system shut-downs will require the water to by-pass the filter/membrane units and be discharged to sea. Since the feed water is produced water , it can not be shut down, making discharge to sea the only option. Except for the above, the possibilities for and mitigation measures applicable to prevent accidental discharges of HPAM are equivalent to those listed for Case A.

4.6 Case D – HPAM injected with produced water, excess water to sea


Case D applies if the total amounts of produced water exceed the amount used for injection of HPAM and surplus produced water is discharged to sea. HPAM will in this case be discharged to sea if the injected produced water containing HPAM penetrates the reservoir and enters the production wells equivalent to Case B. As for Case B, efficient HPAM warning and detection enabling the producing well(s) to be shut down quickly is essential to minimize the amounts of HPAM being discharged.


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As for Case C, the concentrate from the filter/membrane section will contain HPAM after HPAM breakthrough into producing wells and separated out with water in the inlet separator .

Booster pumpWater injectionpump

HP AM injectionpump

HP AM storagetank


B

Injection water treatment pkg.

A

Produced oi l

Excess produced water to sea

Produced water treatment pkg.

Concentrate

Figure 4 Case D – Produced water as HPAM medium. Excess produced water to sea.

b. Case evaluation The same evaluations of produced water as HPAM carrying medium in case C applies for case D. Evaluation of discharge of produced water is the same as for case B. This case will not meet the zero discharge requirement unless a HPAM warning and detection system enables the well(s) to be shut down prior to HPAM breakthrough into the production well(s). This will be a scenario that could be difficult to control and document. For the concentrate stream to meet the zero discharge criteria, it may have to be injected in a disposal well.

4.7 Comparison of evaluated cases The environmental performance of the four cases has been compared with each other . Table 3 gives an overview of the four evaluated cases. Case A is considered as base case, and the three other cases are compared with this case. The environmental performance of the four cases has been compared with each other on the following parameters:

- Operational discharges: Discharges of HPAM after breakthrough, back production in producing well(s) and separated out with produced water being discharged to sea (÷ in Table 3 indicates larger discharges).


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- Risk for unplanned discharges: Possibility for unplanned discharges of HPAM due to equipment shut-downs and other incidents (÷ in Table 3 indicates higher risks)

- HPAM detection system: Require an efficient HPAM detection system to minimize discharges of HPAM (÷ in Table 3 indicates dependency of an efficient HPAM detection system)

- Emissions to air (+ indicates lower emissions in Table 3) - Ability to meet zero discharges of HPAM to sea (narrative descriptions in Table 3)

Table 3 Comparison of the four cases

Operational discharges

Risk for unplanned discharges

HPAM detection system

Emissions to air

Ability to meet the zero discharge requirements

Case A 0 0 0 0 Yes

Case B ÷ ÷ ÷ + Doubtful

Case C 0 ÷ 0 + Yes

Case D ÷ ÷ ÷ + Doubtful The likelihood and risks for unplanned discharges are assumed to be higher for the cases with produced water as HPAM carrying medium. The reason for this assessment is that the irregular water quality may increase the risks for failures in the water treatment facilities, resulting in produced water bypassing these facilities and being discharged to sea. The produced water will contain HPAM after a breakthrough in the reservoir . How HPAM will affect the performance of the water treatment facility is uncertain. Since Case B and Case D discharge produced water to sea, HPAM will be discharged in the period from prior to first detection until the production or the individual well(s) have been shut down. HPAM in produced water at concentrations lower than the detection limits will be discharged to sea. The amounts discharged depend on the sensitivity of the applied detection method, the speed of the increase in HPAM concentrations and the time it takes to shout down the producing wells. Since case C and D are assumed to be more technical complicated than case A and B, the more likelihood of system failure increases the probability of unplanned discharges of HPAM due to equipment failure or non-performance for these cases. Since produced water is re injected in the cases A and C, the need of accurate and quick HPAM detection system is not considered to be of the same importance as for the cases with produced water discharges to sea. Since the total amount of water injected in case A (sea water as well as produced water) is higher than in the other cases, the increased energy demand due to pressurizing of water results in higher emissions to air for this case compared to the other ones. If sea water as well as produced water is being re-injected regardless of the use of HPAM flooding, the higher emissions cannot be attributed to the flooding project.


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5 HPAM detection in produced water

5.1 Analytical methods An analytical method for detection of HPAM in produced water must take into account that the “HPAM” substances in produced water may not be identical to the product injected. This means that analytical methods using the product as a reference will not give a true description of any content of HPAM components in produced water as only the non-degraded part is detected and expressed as content of the unaltered and injected HPAM. The chosen method should preferably be feasible to be performed offshore. Furthermore the method should be specific with respect to substances/groups etc detected and have a reasonable low detection limit in order to meet criteria’s established for acceptable operation with respect to the environment. In addition the method should not be too demanding with respect to analytical equipment, requirements for maintenance/ calibration and operators skill. Other aspects that need to be sustained are equipment’s need of space, external calibration need and cost connected to procurement and maintenance. Since injected HPAM change over time with respect to chain length and degree of hydrolysis, an optimal method should be able to quantify the sum of amide and carboxylic acid groups. Methods detecting the two groups separately have not been found. Nor methods where the amide groups are hydrolyzed to carboxylic acid for quantification of the total content of carboxylic acids (it is expected that it is difficult to hydrolyze all amide groups as at one point the carboxylic acid groups tends to protect the amide groups for further hydrolysis). Search on the internet gave astonishing little information concerning detection of HPAM in produced water especially and detection of HPAM in water/sewage in general. China seems to have a rather high focus on use of HPAM in IOR applications and a number of interesting articles concerning analytical methods have been found. However , most of these are in Chinese and for many of those we have to relate to available abstracts given in English. The various methods stated are based on the following principles: a. Starch-iodide spectroscopy b. Turbidimetri c. Viscosity d. Ionic selective electrode (determination of liberated NH 4) e. Gel Permeation Chromatography (GPC)/Size exclusion Chromatography (SEC) f. Ultra filtration with analysis of film formed g. Other methods These principles are given a short description in the following: a. Bromination-Starch spectroscopy Ref. 30,31,32,33 Comprises different methods of N-bromination of the amide groups and development of a starch complex (of iodide or cadmium) measured by spectrophotometer . Detection level in the range of 0-25 mg/l is reported. It is possible to use the method offshore as the need for instrumentation is limited to UV/VIS spectrophotometer in addition to standard laboratory equipment. It is anticipated that the method require fairly much manual work and it is so forth time consuming.


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Costs for both equipment procurement and maintenance are considered low. The operation requires a skilled chemist. The principle has been adapted to Flow Injection Analysis (FIA) giving a range of 2 – 1200 mg/l. Detection range in the area of 2-3 mg/l may prove satisfactorily and the use of FIA will reduce manual work and needed time for analysis. b. Turbidimetry Ref. 28, 29 Turbidimetric methods are based on light scattering of the HPAM particles in water after treatment with acetic acid or hypochlorite. The haziness developed can be used for determination of the HPAM content using standard water nephelometer and response measured in NTU (Nephelometric Turbidity Units). It is reported that the response depends on the degree of hydrolysis and time between treatment and measurement. The detection range is reported to be in the area of 100 – 900 mg/l. Determination of HPAM in water is anticipated to be easily performed using the turbidity method. Furthermore only a nephelometer is needed in addition to standard laboratory equipment. The operator will not need to be at a trained chemist level. However , a detection limit of approximately of 100 mg/l is considered to be high. Sample preparation, by different means may prove satisfactorily to improve the detection limit by a 100 fold. Such techniques can be ultra filtration and ultra centrifugation but needs to be exploited. Use of in-line/on-line instrumentation may prove satisfactorily in order to continuous monitor and detect a sudden breakthrough of HPAM at high concentrations. c. Viscosity Ref. 6, 34 Determination of viscosity is mentioned by several as a method for determination of HPAM in water . The measuring range seems to be in the area of 100 -1000 mg/l and the principle seems most suitable for measurement of HPAM in injection water . Even though the method is easy to perform, requires little resources with respect to procurement and maintenance, it is considered suitable only if a breakthrough of HPAM occurs more or less instantly and at a high concentration level. d. Ion selective electrode (determination of liberated NH4) Ref. 16 The method comprises digestion of produced water with sulfuric acid according to the Kjeldahl method, adjusting the pH with sodium hydroxide and measurement of NH 3

by ammonia selective electrode. The optimum range is the area of 6- 45 mg/l HPAM. Volatile amines are stated to give interferences together with amines/amides from other sources such as N-containing production chemicals and proteins from microbiological activity. Although the principle has a reasonable detection limit, is easy to perform and has no need for advanced equipment, it is not considered relevant. This is due to the sulfuric acid digestion, even though automated systems are available, the use of high temperature sulfuric acid digestion is considered inapplicable on offshore installations. e. Gel Permeation Chromatography (GPC) Ref. 18, 21


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Gel permeation Chromatography (GPC) is a separation technique (equivalent to size exclusion chromatography, SEC) used for polymers. Separation is performed in a column containing a porous media and smaller molecules are withheld in the pores as the bigger molecules pass trough. Detection of HPAM is done using an UV detector . A detection range of 0,1 - 100 mg/l for HPAM in produced water is reported Other reports the use of SEC for detection of PAA in soil waters with a detection range of 0,2- 80 mg/l. The UV detector was set to 195 nm. At that wavelength it is anticipated response from carboxylic groups as well, although the sensitivity should be highest for the amide groups. Specifically developed column material for PAA detection using SEC UV-Vis is reported giving analysis within a few minutes in the range of 0,1 to 75 mg/l. It is our opinion that detection levels this low may be difficult to obtain and that a detection level in the range of 5 – 10 mg/l may prove more likely. This can, however only be determined by testing and until done, a detection limit at about 1 mg/l is anticipated. UV detector , at 190-200 nm, gives response from both the carboxylic acids- and amide groups in the HPAM backbone. The sensitivity between the two groups is not known but depends on the eluent’s composition and background interference. The technique requires sophisticated and expensive instrumentation. Maintenance and calibration are considered to be at a sophisticated level and analysis should be performed by a skilled chemist. It is the opinion that the principle can be used offshore for detection of HPAM in produced water . However , a method needs to be established taking into account the overall produced water composition and the relative sensitivity of amide and carboxylic groups in the polymer . f. Ultra filtration with analysis of film formed Ref. 5, 36 A new technique using ultra filtration and films’ desaturation is reported. This technique is capable of determining the true HPAM content independently of the degree of hydrolysis. Details are not revealed but the sample preparation comprises the following steps; filtration with 0,45 micron filter in order to remove solids, washing the sample with pentane in order to remove dispersed and dissolved hydrocarbons and ultra filtration using 100K or 300K cutoff . Details on the quantification are not given but others indicate that the film is dried and it is anticipated that the quantity of HPAM is determined gravimetrically. The method requires little instrumentation although an analytical balance is needed. The detection limit is not stated, but examples given indicated levels at hundred of ppm’s. Operation with detection of levels down towards 1 mg/l will probable demand an unreasonable volume of water sample making the process time-consuming at best, it is highly probable that this method is not applicable for the detection limit required. g. Other methods Ref.37, 38 Advanced methods based on mass spectrometry (MS) for analysis of PAM in foods by LC-MS/MS and Reversed-Phase Liquid Chromatography–Electrospray–Tandem Mass Spectrometry gives detection limits in the area of 0,01 - 0,025 mg/kg. Little information is found using MS principles for quantification of HPAM in water. The techniques can of course be adapted to such quantification giving excellent detection limit. However , the necessary equipment is advanced, costly and requires dedicated and highly skilled operators. The


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use of such equipment offshore is not considered feasible. Analytical techniques like this may prove necessary for onshore verification of results obtained offshore. Another possibility is to introduce a colored monomer in the HPAM backbone, ref. 11. Doing this the detection of HPAM in produced water could be simplified. Test performed back in 1981 introduced N,2,4 dinitro-acryline-acrylamide monomer in one of each 3000 acrylamide monomer (ref. 11). The polymerization of the backbone was not interfered by the introduction of the dye and the content of HPAM could easily be detected down to 50 mg/l by visible spectroscopy. The detection limit seems rather high and it is uncertain if the method could be refined for better performance. A survey on the internet indicates little progress since 1981 and the principle may not be an encouraging solution.

5.2 Comparison of the analytical methods Table 4 shows a summary of the relevant analytical methods presented in this chapter . The method f and the different other methods presented in g are considered to be novelty methods, and not applicable for detecting HPAM today. Table 4 Summary of relevant analytical methods

Method Detection limits (mg/l) Cost

Method complexity

Personel demand

Analysis location Comments

a 0-25 Low High Skilled chemist Offshore Time consuming method

b 100-900 Low Low Unskilled Offshore Too high detection limit

c 100-1000 Low Low Unskilled Offshore Too high detection limit

d 6-45 Low Low Unskilled Onshore Inapplicable offshore

e 0,1-100 High High Skilled chemist Offshore Fast method The colour code used in Table 4 is very simple, mainly deviating between feasible (green) and less feasible (red). Low detection limit and the possibility to do the analyses on the installation offshore are considered the most crucial properties. Even though method e, Gel permeation Chromatography, is complicated and costly, it is considered to be the best method due to the low detection limits and the short analysis time. Method a is considered to be a cheaper method, but due to the time consuming operation, not as feasible as method e.

5.3 Tracers Use of tracers injected in front of the HPAM flooding régime may also be an option in lack of acceptable analytical methods or as a supplementary warning measure functioning as an integral part of an HPAM control system. Tracer techniques are highly specialized and the principle will only be addressed in a general manner . Use of tracers injected in front of the HPAM solution will require small amounts of tracer agents compared to a continuous injection with the flooding process. An applicable tracer needs to be specific with regards to detection, meaning that it should not be a natural part of the produced water or the process chemical regime, furthermore it should be easily detectable at very low concentrations and finally behave as inert substance not reacting with the formation/formation water and so forth follows the water front.


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Fluorobenzoic acids (FBA) are a group of substances meeting such criteria, ref. 24. Approximately 16 different isomers or derivatives can be used as water tracers. They have all a sufficient low pKa and will act protolyzed in the reservoir as anions. As anions they are very water soluble and not reactive towards the formation. However , many of these substances are not readily biological degradable and are categorized as red substances, thereby violating the zero discharge requirement themselves. Even though FBA’s, have been and are still used on the Norwegian Continental Shelf for tracing purposes. In the year 2009 the consumption and discharge of water soluble tracers on the NCS was approximately 12 and 9 tons respectively. The figures relate to the product and so forth includes water and the discharged values are often reported in the year of the operation even though it can take years before the tracer is fully back produced. Based on this it is approximated that the discharge of water tracers in 2009 was in the area of some hundred kg and FBA represents the bulk the discharge. Analytical methods for detection of FBA’s comprise liquid chromatography (LC) with different detection principles. Use of tandem mass spectrometry give detection limit down to 0,001 mg/l as atmospheric pressure chemical ionization detection has a limit of 0,02 mg/l, ref. 25. Analysis time is reported to be about 10 min. Complicated and expensive equipment makes this solution unsuited for offshore use. Other and more simplified instrumental techniques are high pressure liquid chromatography (HPLC) with UV detector and ion chromatography (IC), both relevant for offshore use. The detection limits are reported to 0,2 (ref. 26) and 0,02 (ref.27) for some relevant FBA’s. The principle and necessary equipment resembles GPC and it is regarded usable for offshore use with more or less the same requirements with respect to operator skill, costs etc. Radioactive tracers such as triated water , iodides etc are normally used for reservoir studies. It is uncertain if such tracers are applicable for this kind of well maintenance due to high losses in the reservoir . As for the water soluble chemical tracers, the use of radioactive tracers are highly specialized and further evaluations needs to be performed by specialists in this area. It is, however , relevant to point out that from 2010 any use and discharge of radioactive tracers are to be reported to the authorities (Norwegian Radiation Protection Authority) through the annual report to The Climate and Pollution Agency. This again may induce awareness and consequently a reduction in the use of radioactive tracers in general and prevent such use in new areas.

5.4 Applicable methods and detection limits Modern instrumental methods are based on detection of the amide groups in the HPAM backbone. As mentioned earlier the degree of hydrolysis will increases over time, due to temperature and pH in the reservoir , resulting in a decrease in number of amide groups. Consequently is it impossible to predict the composition of HPAM in produced water . As an example, an analysis is performed on basis of amide groups in the polymer , anticipating an original degree of hydrolysis of 25 %. If the degree of hydrolysis has increased to 75 % when the HPAM is detected in the produced water , and the analysis shows a result of 1 mg/l, the total concentration of the polymer will be 3 mg/l. If the degree of hydrolysis is even higher , the error will increase rapidly, as shown in Figure 5. The figure shows that if the detection limit is 1 mg/l, the actual concentration of the polymer at the detection limit could be much higher , depending upon the degree of hydrolysis.


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02468

10121416

25 45 65 85

HPA

M c

once

ntra

tion

[ mg/

l]

Degree of Hydrolysis, %

Figure 5 Actual HPAM concentration at different degrees of hydrolysis, if a degree of hydrolysis of 25 % is assumed and 1 mg/l is detected. A solution to this obstacle could be a worst case approach incorporating a safety margin stating that the determined content should be multiplied with a safety factor of 2 in order to reduce the uncertainty using amide groups as basis for interpretation. It is, however difficult to establish an acceptable detection limit for HPAM in produced water . Produced water may be discharged for a limited time with a content of HPAM when the concentration is below the detection limit. Having no information of the rate of increase in HPAM concentration in the produced water following a breakthrough into the production wells, we have made a simplified sensitivity analysis assuming a linear increase of 0,005, 0,01, 0,1, 1 and 10 mg HPAM per liter and hour from an imagined breakthrough of HPAM at a total water production of 10 million m3/year . The analysis is based on injection of 1000 mg/l of HPAM and a maximum concentration in the produced water of 333 mg/l, representing a 3 fold dilution of the HPAM in the reservoir .


20

Table 5 shows the calculated concentrations of HPAM in the produced water at given times after the breakthrough for the selected cases. For illustration purposes are the calculated HPAM concentrations below 1 mg/l colored green, concentrations between 1 and 10 colored yellow and concentrations over 10 mg/l colored red.


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Table 5 Calculation of HPAM concentrations for the different scenarios based on concentration increase rates

HPAM concentration in produced water, mg/l

Days Hours 0,005 mg/l,h

0,01 mg/l,h 0,1 mg/l,h 1 mg/l,h 10 mg/l,h

0,0 0,1 0,0 0,0 0,0 0,1 1,0

0,0 1,0 0,0 0,0 0,1 1,0 10

0,1 2,0 0,0 0,0 0,2 2,0 20

0,1 3,0 0,0 0,0 0,3 3,0 30

0,2 4,0 0,0 0,0 0,4 4,0 40

0,5 12,0 0,1 0,1 1,2 12 120

1,0 0,1 0,2 2,4 24 240

2,0 0,2 0,5 4,8 48 333

3,0 0,4 0,7 7,2 72 333

4,0 0,5 1,0 9,6 96 333

5,0 0,6 1,2 12,0 120 333

6,0 0,7 1,4 14,4 144 333

7,0 0,8 1,7 16,8 168 333

8,0 1,0 1,9 19,2 192 333

9,0 1,1 2,2 21,6 216 333

10,0 1,2 2,4 24,0 240 333

11,0 1,3 2,6 26,4 264 333

12,0 1,4 2,9 28,8 288 333

13,0 1,6 3,1 31,2 312 333

14,0 1,7 3,4 33,6 333 333

15,0 1,8 3,6 36,0 333 333

16,0 1,9 3,8 38,4 333 333

17,0 2,0 4,1 40,8 333 333

18,0 2,2 4,3 43,2 333 333

19,0 2,3 4,6 45,6 333 333

20,0 2,4 4,8 48,0 333 333

21,0 2,5 5,0 50,4 333 333

22,0 2,6 5,3 52,8 333 333

23,0 2,8 5,5 55,2 333 333

24,0 2,9 5,8 57,6 333 333

In a similar way, the aggregated amount of HPAM following the produced water is illustrated in Table 6. This will be equivalent to the amounts of HPAM being discharged until the discharge is stopped due to the HPAM concentration reaching a predefined limit level and the water flow consequently stopped by actions such as well shut down or water reinjection.


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Table 6 Calculation of discharged amounts of HPAM for the different scenarios based on HPAM concentration increase rates.

HPAM discharged with prooduced water, kg

Days Hours 0,005 mg/l,h 0,01 mg/l,h 0,1 mg/l,h 1 mg/l,h 10 mg/l,h

0,0 0,1 0 0 0 0,01 0,06

0,0 1,0 0 0,01 0,06 0,57 5,7

0,1 2,0 0,01 0,02 0,23 2,3 23

0,1 3,0 0,03 0,05 0,51 5,1 51

0,2 4,0 0,05 0,09 0,91 9,1 91

0,5 12,0 0,41 0,82 8,2 82 822

1,0 0,0 1,6 3,3 33 329 3 288

2,0 0,0 6,6 13 132 1 315 9 123

3,0 0,0 15 30 296 2 959 18 247

4,0 0,0 26 53 526 5 260 27 370

5,0 0,0 41 82 822 8 219 36 493

6,0 0,0 59 118 1 184 11 836 45 616

7,0 0,0 81 161 1 611 16 110 54 740

8,0 0,0 105 210 2 104 21 041 63 863

9,0 0,0 133 266 2 663 26 630 72 986

10,0 0,0 164 329 3 288 32 877 82 110

11,0 0,0 199 398 3 978 39 781 91 233

12,0 0,0 237 473 4 734 47 342 100 356

13,0 0,0 278 556 5 556 55 562 109 479

14,0 0,0 322 644 6 444 9 123 118 603

15,0 0,0 370 740 7 397 18 247 127 726

16,0 0,0 421 842 8 416 27 370 136 849

17,0 0,0 475 950 9 501 36 493 145 973

18,0 0,0 533 1 065 10 652 45 616 155 096

19,0 0,0 593 1 187 11 868 54 740 164 219

20,0 0,0 658 1 315 13 151 63 863 173 342

21,0 0,0 725 1 450 14 499 72 986 182 466

22,0 0,0 796 1 591 15 912 82 110 191 589

23,0 0,0 870 1 739 17 392 91 233 200 712

24,0 0,0 947 1 894 18 937 100 356 209 836

Regarding the calculated aggregated HPAM “discharges” are values less than 1 % of red discharges on NCS in 2009 (totally 21 tonnes, ref. 1) which equal 210 kg colored green, values between 210 and 2100 kg (equal between 1 and 10 % of red discharges) colored yellow and more than 2100 kg colored red. The calculations shown above are theoretical only, but show clearly that a HPAM detection system capable of detecting HPAM at low concentrations in combination with short time for implementing remedial actions after initial detection of HPAM are essential and will be key elements in the evaluation by KLIF .


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The low range increase scenario shows that the HPAM concentration reaches 1 mg/l after 4 – 8 days. Analyzing the produced water with a detection limit in that area implies that HPAM could be detected after 4-8 days from breakthrough. Giving a day or two in order to organize a well shut down or water reinjection the water discharge could be stopped after approximately 5-9 days totally and the amount HPAM discharged will be in the range 100 – 200 kg. The high end increase scenario shows that a level of 1 mg/l is reached after only a few hours and measurement using a detection limit of 1 mg/l will be able to detect the breakthrough almost immediately. However , analysis of produced water is normally performed on a day and night basis and taking the time for analysis into account and the time needed to arrange water shut off could it take a day or so until it is done. If so, the discharge will be in the unacceptable range of 3000 to 10000 kg. The sensitivity analysis shows some fundamental requirements that need to be taken into account:

• If the HPAM concentration in produced water is low and has a low increase over time, < 0,01 mg/l per hour , it is necessary to have a monitoring method being able to at least detect HPAM at the 1 mg/l level. Analysis performed on day/night basis seems acceptable giving only minor discharges of HPAM with a few days of discharge.

• If the HPAM concentration in produced water is high or has a high increase over time it is necessary to carry out more frequent measurements to detect the breakthrough. In this situation frequent measurements are more important than having a method with a low detection limit. Methods based on turbidity or viscosity adapted for continuous on line measurement will be of higher value than measurement having a low detection limit.

Based on these considerations is it obvious that the measuring principle must be fast and easy to perform and have a reasonable low detection limit. The evaluation of analytical methods shows that only the GPC based principles meet these requirements and should be the preferred solution. The sensitivity using UV detector will be somewhere in-between detection of all amide groups and a additional response from the carboxylic acids. Using a safety factor of 2, as discussed earlier , the GPC technique may detect HPAM from approximately from 0,5 mg/l even using a safety factor of 2. The method needs to be tested, safety factor if relevant established, and adapted for offshore use. Effects of salinity, divalent ions, fatty acids, production chemicals and so on are impossible to predict and needs to be established, as well as other possible interferences. However , a very rapid increase in the HPAM concentration in the produced water , as indicated in the high end scenarios, show that within only a few hours the discharged amount could be unacceptable high. If no indications are given in advance there will be no ways to prevent such discharges unless an online detection system is installed. At present, no applicable in-line/on-line monitoring equipment seems to be available. Devices for measurement of turbidity in wide ranges are available and should be capable to detect a breakthrough of HPAM when the concentration is sufficient high. It is unknown if the water stream need to be added acid/hypochlorite in order to improve the sensitivity. It is also unknown how the dispersed oil will contribute to the turbidity and it may prove necessary to adjust the HPAM response with a similar on-line monitoring of oil in water by online fluorescence techniques.


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6 A holistic approach to achieve zero discharges

6.1 General approach Compliance with the zero discharge requirements can be based on a three step approach: Step 1 Reinject all produced water . If reinjection is implemented, step 2 and 3 will be

less critical. If reinjection is not implemented, step 2 and 3 will be critical. Step 2 Establish an adequate HPAM warning and detection system. Step 3 Mitigate HPAM discharges in case it is detected in the produced water . Shut

down of producing well(s) is the only measure identified. The four cases described in section 4 are in this chapter evaluated from a holistic point of view.

6.2 Case A – HPAM injected with seawater, all water reinjected Case A will not have operational discharges to sea. The zero discharge requirements should therefore be met. Warning and detection of HPAM in produced water and subsequent well shutdowns should therefore not be a requirement from an environmental point of view. However , operational control may still require that a reliable, sufficiently sensitive and easy-to-operate detection system is in place. Systems should be in place to minimize/avoid accidental discharges of produced water to sea if the produced water treatment and injection system fails to operate. Such prevention measures represents well proven technology and do not need to deviate from similar systems applied for other produced water reinjection systems.

6.3 Case B – HPAM injected with seawater, water discharged to sea

For Case B, produced water will be discharged to sea. Discharge of HPAM to sea can only be fully prevented if the production is stopped before the HPAM solution in the reservoir reaches the producing wells and there is no guarantee that minor , undetected amounts of HPAM can have ended up in the discharged produced water already. The only way to control and prevent massive amounts of HPAM to be discharged to sea with the produced water is to install an acceptable HPAM warning and detection system and tie that to a system that enables rapid well shut downs. The study has shown that there are HPAM detection systems and methods available that should enable the operator to control and limit the discharges of HPAM after breakthrough to a level that might be discussable and maybe acceptable for KLIF (reference is made to the following statement in KLIF’s comments Ref.1.“Vi registrerer at bransjen oppfatter at nullutslippsmålet er et hinder for kjemisk flømming. Vi mener at det kan være behov for å gjøre en mer helhetlig vurdering av bruken og reguleringen av


25

enkelte grupper kjemikalier , og er åpen for en dialog for å komme fram til miljømessige gode løsninger”). These guides from KLIF do not automatically open up for acceptance to discharge smaller amounts of HPAM containing produced water , but it opens up for discussions. We believe that the operator will have to document that he has done his utmost to minimize the discharges. One measure could be to use a tracer in front of the HPAM injection. This will require onsite detection enabling quick response in case of breakthrough.

6.4 Case C – HPAM injected with produced water, excess water reinjected

This case is equivalent to case A and the conclusions should be the same as for Case A. Case C has, however , some operational challenges that are avoided in Case A:

1. The composition of produced water can complicate the processes for conditioning of the water to make it suitable as the base fluid for HPAM injection. The fact that produced water composition may vary across wells and over time enhances these challenges. In addition to the operational challenges, these water conditions may make the produced water injection system more vulnerable for shutdowns resulting in accidental discharges of produced water containing HPAM.

2. After breakthrough of HPAM into the produced water , shutdown of the produced water treatment and injection system will result in unavoidable discharges of HPAM to sea.

Consequently, the risk of unplanned discharges to sea will be higher than for Case A, and should be properly planned for .

6.5 Case D – HPAM injected with produced water, excess water discharged to sea

This case will be equivalent to case B, the differences being:

1. The total amounts of HPAM that could be discharged to sea will be smaller than for Case B, dependent upon the degree and amount of surplus produced water

2. The operational challenges of produced water handling and conditioning will be more of the same magnitude as for Case C with similar risks for unplanned discharges of HPAM containing produced water .

Case D will have the same requirements to HPAM warning and detection and well shutdown as Case B


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7 Conclusions

The following conclusions are made:

5. HPAM is categorized as a red chemical due to its poor biodegradation properties. Discharge of red chemicals to sea is in conflict with the zero discharge target. This requirement does not prevent the chemical to be used.

6. HPAM may appear in the produced water following a HPAM solution breakthrough in the reservoir . The concentration of HPAM in the produced water may increase with time until a peak concentration is met.

7. There should be no conflict with the zero discharge requirement if all produced water that may contain HPAM is re-injected in a sub surface reservoir

8. If all or parts of the produced water are discharged to sea, the zero discharge requirements will be violated.

9. The regulators may be open for a dialogue with the operator if the discharges of HPAM are small.

10. A system should be in place to detect HPAM in the produced water in case of HPAM breakthrough into production wells. The system should automatically shut down affected production well(s).

11. HPAM detection systems should have a low detection level and enable analyses done offshore. Several principles have been found, but Gel Permeation Chromatography (GPC) seems to have the preferred properties.

12. More work will be required to qualify a detection system for the application. Early warning systems comprising tracer technology should be investigated and evaluated for this application.


27

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