TO SCALE OR NOT TO SCALE IN 2500 PSIG ONCE THROUGH STEAM GENERATORS

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1 SPECIAL THANKS Thanks to Jim Bellows for nominating me, I am truly honored to accept this award on behalf of the Produced Water Consensus Document Task Group working under the ASME Water Subcommittee THERE ARE MANY GREAT PRODUCED WATER AND INDUSTRY EXPERTS THAT I HAVE HAD THE OPPORTUNITY TO SOLVE WATER TREATING AND/OR BOILER PROBLEMS WITH OVER THE PAST 10 YEARS THANKS TO EACH OF YOU, ESPECIALLY BOB HOLLOWAY, HOLLOWAY ASSOCIATES GUY MOMMAERTS, ION EXCHANGE SERVICES GORDON PAGE ED HOFFMAN, EDVENTURES DEBORAH BLOOM, NALCO UTILITY BOILER EXPERT MARTY GODFREY, NALCO CHEMIST And thanks to anyone that I have not mentioned

2 TO SCALE OR NOT TO SCALE IN 2500 PSIG ONCE THROUGH STEAM GENERATORS HELMHOLTZ AWARD LECTURE NIAGARA FALLS, ONTARIO JULY 21, 2010 By: Melonie Myszczyszyn,, P. Eng

3 NORTHERN ALBERTA, CANADA OILSANDS AREA Source: Wikipedia, Oilsands, internet site

4 LIFE CYCLE OF THERMAL STEAM

5 CSS CYCLIC STEAM STIMULATION

6 THERMAL STEAM WELLS ONE TYPE IS THE CSS (CYCLIC STEAM STIMULATION ) WELLS HIGH OR LOW PRESSURE 80 95% STEAM QUALITY IS INJECTED INTO CSS (CYCLIC STEAM STIMULATION) WELL 480 TO 520 M (1574 TO 1706 FT) DEEP STEAM IN CSS WELL IS ALLOWED TO SOAK FOR A PERIOD OF TIME BECOMING WATER AND THEN FLOWS BACK WITH THE OIL AT THE WELLS PRESSURE AND TEMPERATURE IS CYCLICAL PROCESS ALSO CALLED HUFF AND PUFF LOTS OF WATER VAPOUR WHEN WELL INITIALLY FLOWS BACK AND THEN ANNULUS GAS (SOLUTION) GAS FROM OIL RELEASING

7 SAGD STEAM ASSISTED GRAVITY DRAINAGE

8 THERMAL STEAM WELLS THE SECOND TYPE IS SAGD (STEAM ASSISTED GRAVITY DRAINAGE) WELLS LOW PRESSURE % STEAM QUALITY IS INJECTED INTO SAGD (STEAM ASSISTED GRAVITY DRAINAGE) WELL 480 TO 520 M (1574 TO 1706 FT) DEEP STEAM IN WELL RETURNS WITH EMULSION UP THE PRODUCING WELL IN THE SAGD PAIR IS CONTINUOUS RETURN OF PRODUCED WATER WITH OIL

9 OUTLINE What is produced water? Produced Water Consensus Document Debate: To scale or not to scale 2500 psig Once Through Steam Generators utilizing Produced Water

10 PRODUCED WATER

11 PRODUCED WATER Produced Water is separated from the heavy oil when it returns from the well in oil treating plant facilities Three phase (oil, water/sand, gas) separation vessels Slug Catcher, Separator, Treater

12 SEPARATION VESSELS source: US Environmental Protection Agency

13 PRODUCED WATER As each thermal reservoir is different the properties of produced water are unique for each thermal oil recovery site No two produced waters created are identical Thus, the produced water returns with many contaminants resulting in boiler feed water with ranges of components

14 TRADITIONAL PRODUCED WATER TREATING Main way used to treat the produced water to boiler feed water consists of Warm or Hot Lime Softener and Weak Acid Cation Exchange Units Such systems result in a boiler feed water with contaminants as listed in the following detailed produced water analysis A boiler feed water with high scaling tendencies when heated to boiler operating pressures and temperatures

15 WATER COMPARISONS Treated Produced Water, Contaminant Pure Water, BFW BFW ph 8.8 to to 9.8 Error in Field Testing Conductivity, umhos Specific 0.5 to to Cation exchanged 0.06 to 0.3 Total M Alkalinity (ppm as CaCO3) < to 1600 Chloride, ppm < to 5500 Total Hardness (ppm as < to 1.0 CaCO3) Total Boron, ppm 0 except nuclear 0 to 29.4 Total Iron, ppm to Lithium, ppm 0 0 to 7 Total Silica (as SiO2) ppm to 150 Total Organic Carbon, ppm <0.1 3 to 250 +/- 15 ppm +/ to 2.0 ppm +/ ppm +/- 5 ppm Oil & Grease, ppm < to 1.0 Total Dissolved Solids, ppm to 8000 Turbidity, NTU 0 0 to 2.2 Tannin & Lignin, ppm 0 0 to 35

16 CHALLENGES OF CREATING BOILER FEED WATER QUALITY FROM PRODUCED WATERS Field testing variance from detailed lab testing Alkalinity, Iron, Hardness and Silica Vary Process Excursions Treating Upsets release higher levels of silica, hardness, and/or organics into boiler feed water Contaminants cycling as produced water returns to facility over time Chlorides slowly increase with time

17 PRODUCED WATER CONSENSUS DOCUMENT - PWCD IN 2008, AN ASME WATER SUBCOMMITTEE TASK GROUP WAS FORMED TO DEVELOP A PRODUCED WATER CONSENSUS DOCUMENT THE GROUP HAS GROWN TO AROUND 55 VOLUNTEER MEMBERS FROM CANADA AND USA PARTICIPANTS ARE FROM ALL ASPECTS OF INDUSTRY : OPERATORS, CHEMISTS, BOILER MANUFACTURERS, CHEMICAL REPRESENTATIVES, AND WATER EXPERTS

18 PWCD GOAL GOAL IS TO CREATE A DOCUMENT THAT CAN BE USED BY INDUSTRY AS A REFERENCE OR STARTING POINT TO ASSIST OPERATORS TO ENSURE MINIMIZATION OF ONCE THROUGH STEAM GENERATOR TUBE CORROSION OR FAILURES

19 ULTIMATELY WANT TO MITIGATE TUBE FAILURES Scaling can result in tube failure or pipe damage Thin Lip Tube Failures Weld Erosion/Corrosion Failures Pipe Wall Loss

20 THIN LIP TUBE FAILURE

21 BOILER PIPING WELD CORROSION

22 TO BE SIMILAR TO EXISTING ASME CONSENSUS DOCUMENTS

23 PWCD INVITATION Open Invitation to anyone interested in participating next meeting is being held in person at the upcoming IWC 2010 in San Antonio, Texas scheduled for October 28 th, 2010 from 8 am to noon We also host webex meetings to work on each section of the document

24 LOCATIONS OF THERMAL INSITU OPERATIONS? Known Locations: Northeastern Alberta, Canada Bakersfield, California, USA Venezeula China Where else are there thermal in-situ locations?

25 SCALE PART OF OPERATING Part of operating Once Through Steam Generators Operate for around 10 months then shutdown and descale the boiler Mechanical pigs are used to clean boiler tubes Or acid washing if tubes require

26 SCALE

27 CRYSTALLINE / AMORPHOUS SCALE

28 TYPES OF SCALE CREATED 75 to 95% of the scale consists of forms of some or all of the following Acmite sodium iron silicate Iron silicates Magnesium silicates Calcium silicates Iron oxides 5 to 25% of the scale Is usually carbon

29 WHERE IS THE CARBON FROM? Is another debatable topic, Carbon could be from Organic or Inorganic Sources There are many organic sources as depicted in the following slide (Ed Hoffman, Edventures,, 2003) There are also many Inorganic sources

30 ORGANICS TYPES OF ORGANICS IN PRODUCED FLUIDS SEPARATION Produced Water ERH/2003 Free Oil Emulsified Oil (O/W) Water Soluble Hydrocarbo Other Water Soluble Organics Process Chemicals Paraffinic Hydrocarbon Oil some Aromatic Hydrocarbon & Some Cyclic Hydrocarbon Grease Napthenic Acids Asphaltene & Non-Hydrocarbon Organic Matter(solids) Process Chemicals - corrosion inhibitor, demulsifier?? depends Volatile hydrocarbon BTEX on Semi-volatile Phenols, carboxylic acids analytical Non-volatile hydrocarbon method TOC Non-volatile hydrocarbon Base soluble Humic Acids Acid / Base soluble Fulvic Acids Process Chemicals - * water soluble Reverse Emulsion Breaker * water soluble clarifier (polymer) SOURCE: Ed Hoffman, Edventures, Organics Charts, 2003

31 INORGANICS Many different inorganic carbon species could be source of carbon in scale Oxocarbons such as CO 3, C 2 O 4 Carbonyls such as (CN) 2, BrCN, Carbides such as Al 4 C 3, FeC 3, More testing and determination of the carbon source still needs to be done

32 OTHER TYPES OF SCALE SEEN At some facilities, the following other scales are created Lithium Silicate Scale Can be created when water treating WAC ion exchange units are not t leaking hardness (no calcium, magnesium, or iron leakage) lithium next ion to attach to silica and create silicate scale Ammonium Carbonate Scale As both the ammonia and carbon dioxide are volatile, when the elements ements liquefy in steam condensate can create scale inside the downstream piping and valves (Marty Godfrey, Nalco Research, IWC Conference IWC , 2009)

33 UPSETS CREATE SCALE LIKE TREE RINGS CAN SEE WHAT HAPPENED PROCESS WISE NOTE: PICTURE OF REGEN WASTE SCALE ILLUSTRATIVE PURPOSES ONLY

34 MECHANICAL PIGGING

35 TO SCALE OR NOT TO SCALE Debatable Whether or not to treat the water only to a manageable scaling state or to clean the water to not scale in boilers Ideal option is to selectively remove scaling ions from water Minimize amount of ions in water

36 SELECTIVE ION REMOVAL If can remove the key scaling ions and leave the rest in the water, then would not result in scale formation Due to contaminants such as organics, chlorides, silica, and alkalinity in the produced water is very costly to try to remove these ions from the water specifically Thus, adding downstream equipment to existing warm or hot lime softening/wac systems to purify the produced water like a reverse osmosis system is currently not feasible

37 SILICA REDUCTION EXAMPLE It has been attempted to lengthen the boiler runtime by reducing silica ppm in boiler feed water from a warm lime softening / Wac system Normal target for silica is from 30 to 50 ppm and reduced down to range of 12 to 15 ppm As is difficult to maintain an exact range - silica values ranged from 5 ppm to 15 ppm over the reduction period

38 LITHIUM SILICATE SCALE Running with lower silica levels and minimal hardness leakage out of the WAC s s (good water treating hardness wise) resulted in creation of Lithium Silicate Scale Very hard, tenacious scale Harder to remove by mechanical pigging Extra cost downtime and maintenance wise

39 LITHIUM SILICATE SCALE Theoretically you need a 4:1 molar ratio of Lithium to Silica (lithium battery research) to create lithium silicate scale Was able to recreate Lithium Silicate Scale in Laboratory with less than 4:1 molar ratio Recreated scaling in a Kettle type of boiler experiment (Presented by Marty Godfrey, Nalco Research, at Conrad Conference e 2006) Operationally as well seems when no calcium, magnesium, or iron present (good treating out of WAC ion exchange units) are able to t create lithium silicate scale with less than a 4:1 molar ratio

40 LITHIUM SILICATE SCALE

41 ALTERNATELY - EVAPORATION In some of the newer facilities, operators have chosen to treat the produced water to boiler feed water quality by installing Evaporators Results in an ideally cleaner boiler feed water (though the resultant water does get contaminants carryover) to once through steam generator but, a highly concentrated blowdown stream that an operator has to deal with

42 BLOWDOWN STREAM COMPONENTS Contaminants Evaporator Blowdown Water ph 13 sodium chloride, ppm 100,000 Silica, ppm organics, ppm

43 EVAPORATOR BLOWDOWN DISPOSAL WELL Deep well injection ph < 9 ERCB requirement and < 200 mg/l silica for deep well disposal. High ph evaporator blowdown wastewater is difficult to dispose and requires complex treatment process.

44 EVAPORATOR BLOWDOWN SALT CAVERN Site availability is the primary concern Can accept blowdown fluid with high values of ph, TDS, and silica

45 EVAPORATOR BLOWDOWN TO CRYSTALLIZER ZLD (ZERO LIQUID DISCHARGE) technology is both capital and energy intensive (~ kwh/1000 gal of distillate). Elevated levels of organic content in SAGD produced water prevents formation of dry solids from the crystallizers

46 SCALE FUNCTION OF WATER CONTAMINANTS So no matter which treating system you use Warm or Hot Lime / WAC or Evaporation - seems you can end up with some type of scale to handle somewhere in your system Either scaling in the once through steam generator tubes or scaling in blowdown or disposal system

47 STILL NEED TO FIGURE OUT What is the right contaminant mixture boiler feed water limits per ion to minimize scaling up to the 2500 psig operating condition and still provide protection to the boiler tubes from erosion, corrosion, or failure? What is the best testing method(s) ) for hardness, silica, organics, chlorides, alkalinity, etc for boiler feed waters created from a produced water source? Operators have been utilizing own methods modified to resemble laboratory detailed testing results Is the required ratio of total alkalinity versus silica still 3:1 at a 2500 psig operating condition to prevent silica polymerization?

48 STILL NEED TO FIGURE OUT What affect does the increasing contaminants in the steam condensate (20% of steam to field) have on the downhole reservoir scaling wise and ability to return emulsion fluid effectively flow wise? What are the geochemical limits in terms of max concentration per ion in steam condensate to reservoir Need to figure out an easy way to keep the evaporator blowdown water contaminants in solution? Or from emitting hazardous gases like H2S when ph adjustments are made for disposing or recycling blowdown stream

49 REFERENCES CNRL Wolf Lake Thermal Operation, near Bonnyville,, Alberta, Canada - photos Marty Godfrey and Paul Desch,, Nalco Research, Naperville, Illinois scale photos Produced Water Consensus Document, ASME Water Sub-committee, Boiler Feed Water Properties TIW Western, Boiler Manufacturer, OTSG photo from website