Chemical precipitation out performs filtration in flowback and produced water recycling operations.

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1 Chemical precipitation out performs filtration in flowback and produced water recycling operations. Abstract The Shalewater Solutions water recycling approach harmonizes technology and simplicity. Treatment of flowback and produced waters by their proprietary process yields high quality, yet cost competitive brine in quantities that can accommodate the most aggressive frac schedules. Shalewater Solutions utilizes a proprietary blend of specialty additive chemicals to precipitate deleterious constituents from flowback and produced waters for recycling purposes. Iron and TSS removal are their chief targets when recycling water for slick water fracs. Results from field trials illustrate that filtration is ineffective at the removal of fine particulate and iron, both of which contribute to production losses. Shalewater s average effluent has a ph of 8.2 with TSS and iron removal rates of 98% and 99% respectively. Introduction This document provides data highlighting the advantages of Shalewater Solutions process compared to other approaches, specifically filtration and blending. In order to fracture a well large amounts of water are required, typically two to five million gallons per horizontal. This water has certain quality constraints that if exceeded will affect downhole performance. One operator in the Marcellus basin requires that TDS be < 100,000 ppm and TSS be < 50mg/L (Schmidt, 2014). Actual limits will vary with the operator and may be in many cases all together absent. What constitutes good water is often nebulous and outcomes based. If water quality alone was the deciding factor treatment approaches such as evaporation and distillation would be the preferred method. The reality is that the cost per barrel treated and throughput volumes balance, and often times discount, water quality drivers. So long as the water is being reused instead of discharged operators have an incentive to select treatment options that are less expensive and capable of handling the volumes associated with the frac schedule. They have neither the desire nor need to purchase drinking water. Table one discusses several treatment technologies as well as an associated range of costs per barrel. Dilution bypasses treatment entirely and can pose difficulties in using the water effectively for fracturing fluids (Lord, 2013). In addition it also results in the potential for well plugging while treatment reconditions the water at a moderate cost and has a decreased potential for well plugging (Boschee, 2014).

2 Table 1. Typical Cost/BBL by Treatment Of all of the treatment technologies illustrated in Table one only distillation addresses total dissolved solids (TDS). Other techniques like reverse osmosis also are capable of creating a low TDS water but the costs are similar to that of distillation due to significant capital and operational expense requirements, not to mention the huge volume of reject concentrate produced by RO. These types of solutions are necessary for discharge to surface waters. So long as new wells are being drilled there will be a demand for high quality brine. During this interval treatment approaches that produce effluents that are suitable for discharged to surface waters will not be cost competitive. Even during a slowdown recycling flowback and produced waters is still more cost effective than UIC disposal. Numerous studies have found that brines can successfully be used as a frac water makeup, and with improvements in produced water quality, the operators were able to increase the mix ratio of treated water to fresh water (Shipman, 2013). In some instances brines are preferred to fresh water. Previous concerns of high TDS interfering with friction reducers have largely been mitigated by the utilization of new tolerant blends. Case studies of wells in Canada s Montney and Horn River shale plays that were treated with brine-tolerant friction reducers demonstrated that their performance in brines was similar to that achieved with conventional friction reducers in fresh water (Paktinat, 2011). Results Shalewater Solutions routinely monitors the quaility of influent and effluent waters from all of their treatment facilites. They also aproach each new water as unique and subject it to a treatability study to identify the optimal treatment regimen. During these investigations various forms of treatment are trialed to select the preferred technique. This section presents data that has been collected from multiple monitoring and treatability projects in the Marcellus, Utica and Permian basins. The data presented discusses particle size distribution as well as chemistry results from various samples including flowback water, produced water and impoundment water. The impoundment water was selected because it was a mix of flowback and produced waters that had significant time to allow settling. The absence of mixing also lead to septic conditions. When impounded prior to treatment and reuse, microbial populations arise and their activity changes the composition of the organic fractions, solubility of metals, and may result in aesthetic issues associated with the odors from gaseous sulfur and nitrogen compounds from microbial metabolism (Mohan et al, 2011). l Page 2

3 Figure 1. Particle size distribution in produced, flowback and mixed impoundment (pit) waters Figure one demonstrates that the majority of the particles in flowback water are below 50um in size. The geometry of the particle size distribution curve of produced water is markedly different than either pit or flowback waters yet all three sources have significant particle counts smaller than 15um. A 10um filter would have to be used to have any significant impact on water clarity. This is smaller than what is generally used in field aplications. Filter socks with a weave tight enough to be effective would quickly blind resulting in transfer difficulty, increased maintenance and waste management costs. Field trials demonstrated that filtration of flowback tests for removing suspended solids commonly experienced filter plugging. Thus the requirement to filter the flowback created an obstacle to reuse (Minnich, 2011). Figure two illustrates that filtration is effective at removing particulate at and above the effective cut size of the filter. There is however an increase in particle counts at the smaller size range. This could be a function of sample heterogeneaity or the increase in small particles could have been created as a result of sheer stresses induced during filtration. In other words it is possible that filtration may actually worsen water quality since the data indicates that it creates the amount of coiliodal particles which will take an extremely long time to settle out. l Page 3

4 Figure 2. Particle size distribution in raw, filtered and chemical precipitated flowback water Chemical precipitation is specifically designed to conteract the repulsive forces keeping these extremely fine particles suspended in the water column. Once the charge is mitigated the particles are allowed to agglomerate growing in size until they naturally settle. The sludge is dewaterd and then this greatly reduced volume of waste is handled seperately. The difference between treated and filtered water is more apperent in Image one below. Image 1. Raw, filtered and chemical precipitated produced water Figures three and four graphically illustrate analytical data observing total suspended solids (TSS) and iron in various different samples. Recall that some operators place a threshold of 50mg/L on TSS meaning that of these samples only those treated by chemical precipitation would pass muster. Dilution is often used at the frac to get TSS to the desired level. l Page 4

5 The costs of acquiring more fresh water and acurately diluting filtered water to achieve a certain TSS value is an externality not reflected in the cost of filtration. With the exception of the impoundment filtration has virtually no affect on iron levels. This is a concern because the high level of dissolved iron commonly present in the water adversely affects the ability of the scale inhibitor to inhibit calcium carbonate scale (Shcolnik et al., 2011). The iron in these flowback and produced water samples completely passed through filtration unimpeded. Even when cut with fresh water the levels remain elevated enough to suppress scale inhibitors. Studies have found that the addition of as little as 10 ppm Fe2+ to test brine caused the observed minimum inhibitor concentrations (MIC) to increase more than one hundred fold when tested against calcite scale using the common phosphonate scale inhibitor - diethylenetriamine-penta (methylene phosphonic) acid (DTPMP) (Graham et al., 2006) Figure 3. Total suspended solids in various different waters l Page 5

6 Figure 4. Iron levels in various waters Figure 5. Bacteria colony forming units in various waters The data in Figure five indicates that surface waters currently being used for completions operations contain high populations of various bacteria. The data also indicates that brines treated by Shalewater Solutions contain significantly lower levels of all types of bacteria tested with the exception of IRB, which is the same, than either raw flowback or surface waters. The ubiquitous nature of IRB underscores the importance of iron removal l Page 6

7 Conclusion When applied correctly filtration can reduce TSS in flowback and produced water. The data in this report however indicates that a significant amount of suspended solids are finer than the effective filter size and remain in the effluent after treatment by conventional filtration. Chemical precipitation is specifically designed to address small suspended solids and results in an effluent free of TSS. The often cited Coulter and Wells statistic states that a 5% contribution in proppant fines corresponds to a 60% flow reduction. This is important to keep in mind when considering that the filtration and blending goal of 50ppm TSS translates into the introduction of nearly one ton of extremely fine particulate per well. Clogging or bridging of the pore space in the formation by these suspended solids can be rapid and severe if these particles are not removed before use (Tonmukayakul et al., 2013). Flow reduction is realized as the net result of plugging, sealing, restriction and bridging of pore spaces within the proppant pack in the fractured formation. In order to successfully meet client s needs water treatment service partners must provide large quantities of high quality brine at a market competitive price. The Shalewater Solutions approach to water treatment strikes a balance between these often times competing objectives. The market will not currently bear the costs of more aggressive types of treatment, nor is it desirable to introduce distilled water into a salt formation. In addition it is difficult and costly to scale these types of systems up to the size required to produce useful amounts of water. Shalewater on the other hand has delivered more than 3.5MM BBLS of treated brine to one operator in Many operators have chosen to filter and blend on site. Chemical precipitation has comparable costs to filtration without TSS burden, decreases in scale inhibitor effectiveness due to dissolved iron and the resulting reduction in flow. l Page 7

8 References Boschee, Pam. (2014, 02). Produced and Flowback Water Recycling and Reuse Economics, Limitations and Technology. Oil and Gas Facilities. Civan, Faruk (2000). Reservoir Formation Damage - Fundamentals, Modeling, Assessment, and Mitigation. Elsevier. Online version available at: Graham, A. L., Boak, L. S., Sorbie, K. S., & Neville, A. (2006, February 1). How Minimum Inhibitor Concentration (MIC) and Sub-MIC Concentrations Affect Bulk Precipitation and Surface Scaling Rates. Society of Petroleum Engineers. doi: /93311-pa Fink, Johannes Karl (2013). Hydraulic Fracturing Chemicals and Fluids Technology. Elsevier. Online version available at: Lord, P., Weston, M., Fontenelle, L. K., & Haggstrom, J. (2013, June 26). Recycling Water: Case Studies in Designing Fracturing Fluids Using Flowback, Produced, and Nontraditional Water Sources. Society of Petroleum Engineers. doi: / ms Minnich, Keith. (2011, 3). A Water Chemistry Perspective on Flowback Reuse with Several Case Studies. Water Sustainability Advisor. EPA Workshop 4, Theme 2, Session 3. Paktinat, J., O&apos;Neil, B. J., & Tulissi, M. G. (2011, January 1). Case Studies: Improved Performance of High Brine Friction Reducers in Fracturing Shale Reservoirs. Society of Petroleum Engineers. doi: / ms Schmidt, Jim (2014). Understanding The Ability Of On Site Treatment Facilities To Significantly Reduce Water Transportation Costs. Produced Water Disposal and Reuse Initiative 2014 Utica & Marcellus. March 26-27, Canonsburg, PA Shen, D., Shcolnik, D., Steiner, W. H., Horstmann, D. G., Taylor, G. N., & Brown, M. (2011, January 1). Evaluation of Scale Inhibitors in Marcellus Waters Containing High Levels of Dissolved Iron. Society of Petroleum Engineers. doi: / ms Shipman, S., McConnell, D., Mccutchan, M. P., & Seth, K. (2013, August 20). Maximizing Flowback Reuse and Reducing Freshwater Demand: Case Studies from the Challenging Marcellus Shale. Society of Petroleum Engineers. doi: / ms Ye, X., Tonmukayakul, N., Lord, P., & Lebas, R. (2013, June 5). Effects of Total Suspended Solids on Permeability of Proppant Pack. Society of Petroleum Engineers. doi: / ms l Page 8