Eco-Tec Announces RecoPur Super Softening Technology a Produced-Water Treatment Breakthrough

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1 Technical Bulletin 0703 Eco-Tec Announces RecoPur Super Softening Technology a Produced-Water Treatment Breakthrough New treatment method to improve performance at a lower cost for heavy oil producers Treats produced water to less than 0.1 ppm hardness using only brine regeneration June 2012, Pickering, Ontario When treating very difficult water containing high total dissolved solids (TDS) and hardness, the patent-pending RecoPur Super Softening Technology is capable of producing very low hardness water (less than 0.1 ppm as CaCO3) using brine-only regeneration. Heavy oil production using thermal techniques (such as steam flooding, cyclic steam, SAGD, etc.) is growing in many parts of the world. Due to limitations or restrictions of using fresh water for steam generation, many operations must consider the use of produced water instead. When water contains high salinity, TDS, and/or hardness, the water treatment requirements for steam generation can become costly. This occurs because when the characteristics of the water are beyond the capabilities of conventional ion exchange softening technologies, and that current water treatment equipment have high capital and operating costs. RecoPur Eco-Tec has been using its RecoPur technology to expand the range of ion exchange in treating difficult waters economically by utilizing the following: 1. High-flow capacity using a small resin inventory and compact equipment. 2. Using salt-only regeneration eliminating the cost and hazards associated with acid and caustic regeneration of conventional WAC ion exchange systems. 3. Significantly reducing the amount of salt required for regeneration. RecoPur Super Softening Technology Until recently, RecoPur systems were capable of treating water down to less than 0.5 ppm as CaCO3. However, with RecoPur Super Softening Technology, systems can consistently treat water down to total hardness levels less than 0.1 ppm as CaCO3 using brine-only regeneration. An example of data from an automated pilot system operating with RecoPur SST technology, treating actual produced water. 1

2 Why RecoPur SST is a significant development In addition to high salinity and hardness, some produced waters also contain high concentrations of silica (greater than 200 ppm). This can cause concern for silica scale formation in steam generators. The most common form of silica scale has been identified as a form of magnesium silicate. Thus, with very little or no magnesium present, the silica scaling potential can be greatly reduced. This allows for much higher silica concentrations in a steam generator without the requirement for silica reduction. This can eliminate the use of lime softening to precipitate silica a process notorious for being costly and difficult to operate. The ability to achieve consistent and reliably low magnesium hardness with RecoPur Super Softening Technology can allow for the operation of steam generators with produced water without the requirement for silica reduction. Refer to the excerpt on the following page, taken from an SPE International technical paper published by Mike Bridle of Worley Parsons MEG in Calgary, Alberta (reprinted in UlTRAPURE Magazine, March 2008 issue) which speaks to the theory behind eliminating silica scale in the steam generator without the need for a silica reduction step in the water treatment process. Note that the references to 20 ppb of divalent cations corresponds to about ppm of hardness as CaCO3 (depending on the combination of cations). This is the range in which the new RecoPur SST process will provide the An Eco-Tec RecoPur Produced Water Treatment System for a heavy-oil operation in Maricopa, California. About Eco-Tec ( Eco-Tec designs, develops, and manufactures equipment for industrial water treatment and purification of chemicals and gases. Our products incorporate advanced, proprietary designs that provide clients with improved performance, economy, and reliability in their operations, while facilitating environmental responsibility. In business since 1970, we have supplied over 2,000 systems in 60 countries. Eco-Tec Inc Squires Beach Road, Pickering, Ontario, Canada L1W 3T9 Telephone: (1) Fax: (1) ecotec@eco-tec.com Eco-Tec Solutions India No 5B, City Center, 930 Synagogue Street, Pune, India Phone: (91) (020) Fax: (91) (020) eco-tec@eco-tecsolutions.com Eco-Tec Inc. Western Canadian Offi ce Suite 325, 400 5th Avenue SW, Calgary, Alberta, Canada T2P 0L6 Telephone: (1) Fax: (1) msurury@eco-tec.com 2 Prosep Technologies Limited Unit 6A, Zone 4, Burntwood Business Park, Staff ordshire, England WS7 3XD Phone: +44(0) Fax: +44(0) ptl@eco-tec.com

3 Technical Paper Excerpt Treatment of SAGD-Produced Waters Without Lime Softening By: Mike Bridle, WorleyParsons MEG Ltd. Orinally presented at the 2005 SPE / PS-CIM / CHOA Thermal Operations and Heavy Oil Symposium OTSG Operation at High Silica Concentration Operating experience in the heavy oil extraction industry has demonstrated that OTSG can generate steam: at 80% quality with <50 mg/l silica in the feed water. at 65% quality with 150 mg/l silica in the feedwater. The water content of the vapour phase, the concentrations of the cations within it and the associated ph are the major parameters that will dictate whether or not silica will precipitate out of solution and form scale in the boiler tubes. Silica is soluble at high ph and temperature, conditions that exist in an operating OTSG. The operating quality can be fixed at 80% which leaves the cation concentration to dictate the scaling tendencies. Cations, and in particular strontium, ferric iron, manganese and nickel readily precipitate as oxides, carbonates and silicates and form scale at the high temperature OTSG operating conditions. With the removal of all the divalent and trivalent cations down to the ppb concentration level, the silica will have nothing to react with and this scaling mechanism will be reduced significantly. Although the analyses of boiler scale have indicated that the divalent and trivalent cation compounds predominate, there is one reported occurrence where lithium silicate was a component of the scale. However, at the adjacent operating facility where the produced water lithium concentration and water treatment process was the same, no lithium silicate was 3 ever detected in the boiler scale samples. The schematic (Fig. 2) presents an alternate SAGD produced water treatment process that does not utilize lime softening. In produced waters with low TDS concentrations, SAC units operating in the sodium form are capable of removing the TH to <0.5 mg/l as CaCO3. However, WAC ion exchangers operating in the sodium form are recommended since the two stage acid/caustic regeneration prevents heavy metal accumulations on the resin and removes any oil. Chelating ion exchange resin then reduces the concentrations of the divalent and trivalent cations to ~20 ppb. The OTSG generates steam at 80% quality and a steam separator removes the 20% water phase from the steam which is then sent to the reservoir as 100% quality. The separated water phase will have a silica concentration that is about five times higher than the boiler feedwater and this minimizes the potential to recycle a portion of this stream to the inlet of the water treatment plant. An alkalinity removal step, although not shown, will also be required. Acidification followed by de-gassing using either vacuum or a suitable purge gas should be incorporated in the process. OTSG Scale Formation Predictions A computer program, capable of predicting the types and amounts of scale that will form at the OTSG temperature and pressure operating conditions was used to simulate the effects of using different quality

4 feed waters. A SAGD produced water with the chemical composition shown in Table 4 was used in the simulations to demonstrate how the scale formation tendency is reduced as the boiler feed water quality is improved. The analysis was for a sample taken during the early stage of plant production. The early production phase sample has a low silica concentration of 155 mg/l. The silica concentration typically increases with time and a more realistic value for a mature operating fi eld is 350 mg/l. scale analyses, precipitates out of solution in the amount of 21 mg/l when the 20% water phase is cooled to 25 C. The cooling step was incorporated to determine the correct ph (9.2 for simulations 1 and 2, and 9.3 for simulation 3). Acmite is not present at 300 C and this would indicate that acmite forms at some temperature as the water is being heated up to the 300 C operating temperature. The total amount of precipitate formed was 11 mg/l. Simulation #2. The concentrations of all the divalent and trivalent A series of three simulations were run and in each case the OTSG was operating at 1200 psi. Simulation #1. In the fi rst simulation, the analysis shown in table 4 with the TH reduced to <0.5 mg/ as CaCO3 was used to represent the boiler feed-water. Table 5 presents a summary of all the precipitates that theoretically form in the 20% water phase, which is the concentrated portion that would be removed in the steam separators. In practice of course, only a portion of this amount would be deposited as scale, but the higher this value, the greater the chance of scale deposition. Simulation results indicate that as the calcium and magnesium concentrations drop below 0.1 and 0.02 mg/l respectively in the boiler feed-water, the dominant precipitates are ferric and nickel oxides. Also, it is interesting to note that acmite (NaFeSi2O6), which regularly shows up in boiler 4

5 cations, including the calcium and magnesiumwere reduced to 0.02 mg/l (20 parts per billion) for the second simulation. The total amount of precipitate formed is now less than 1 mg/l. Simulation #3. The silica concentration in the untreated water is relatively low at 155 mg/l. In order to clearly demonstrate the premise that high silica operation is practical when all the divalent and trivalent cations are reduced to 20 ppb the silica concentration was increased to 350 mg/l for simulation #3. The only diff erence between simulations 3 and 4 was the increase in the silica concentration from 155 to 350 mg/l. The total amount of precipitate increases by only 2 mg/l. It should be noted that no silica precipitation occurs at the boiler operating conditions for any of the options. Author Michael Bridle s water-treatment career covers 40 years, with much devoted to the de-oiling and treatment of produced water in the heavy oil industry. Mr. Bridle s career includes 22 years with Esso Resources where he developed and improved processes for de-oiling and produced water treatment, and involved participation of the first produced water treatment pilot plant in Alberta capable of providing feed water for 2,000- psig once-through steam generators; this specifications established through this remain in use today. 5