Optimizing Fracturing Fluids From Flowback Water

Abstract

As mature fields produce larger quantities of water, operators and service companies find themselves challenged with disposing flowback and produced water to reduce costs, handling the logistics of getting enough water to hydraulically fracture the well, as well as complying with stricter governmental regulations. As produced water is recycled and used in fracturing applications, each cycle of re-used water returns with a more complex chemical make up than before. Therefore, the usable lifetime of the recycled water is shortened or requires expensive cleaning or dilution with fresh water to make it a viable solvent base for fracturing fluids. This paper describes the process to properly design fracturing fluids using flowback and produced water. The importance of flowback water analysis is highlighted for optimizing fluid performance downhole. Recent developments in proper selection of fluid additives and viscosifiers for slickwater and crosslinked fluids are discussed. We will describe in detail how the salinity, biological activity, and scaling tendency of these waters can impact fluid performance. Other factors, including organics and suspended solids will be included in the discussion. Laboratory examples will be shown to demonstrate the importance of following a systematic approach. Ultimately, this paper focuses on how to optimize well performance using recycled waters in stimulation applications. Introduction The exploration and production (E&P) industry in the United States generates approximately 210 bbls/day in produced water (Arnold et al., 2004). Other reports suggest that for every barrel of oil produced in the United States, 10 barrels (bbl) of produced water is generated (Khatib and Verbeek, 2002). Even though some of this material can be managed at the well site, many operators in the United States seek offsite management options for their waste. Offsite disposal companies must comply with state and federal laws including the Resource Conservation and Recovery Act (RCRA), the Environmental Protection Agency (EPA), the Clean Water Act (CWA), and the Safe Drinking Water Act. For instance, to discharge into surface water in Pennsylvania and Wyoming, the company must do so under a National Pollutant Discharge Elimination System (NPDES) permit or into a publicly owned treatment work (POTW). Typical costs associated with disposal range from $0.30 to $10/bbl for injection or cavern disposal to $15 to $22/bbl for solidification and burial in a landfill (Puder, 2007). Operators in the United States have reported that disposal and treatment costs for their produced water exceeded $400 MM/yr (Khatib and Verbeek, 2002). Finding alternative uses for flowback water in the E&P industry is both an economic as well as an environmental issue. In an effort to circumvent some of the extra costs, operators have reported the use of recycled produced waters in reservoir management processes (Khatib and Verbeek, 2002). Water treatment options have been discussed that include desalination, reverse osmosis, and 'floc 'n drop' methods but trucking costs associated with moving water to treatment facilities often make this an expensive option for operators (Kaufman et al., 2008, Horn, 2009). Literature has also been documented on the use of untreated recycled waters in high rate, low permeability shale reservoirs (Arthur et al., 2009). Water volumes for a typical slickwater hydraulic fracture treatment can average 715 m3 (6,000 bbl) per stage with 6 to 10 stages per horizontal well. Large treatment volumes for these applications offer a unique opportunity for cost savings if flowback water can be used in place of other fresh water sources. This approach saves on logistical problems as the water source is near the next treatment site.

Advances in Flowback Chemical Analysis of Gas Shales

“…Field data show that chemistry of flowback water is substantially different than that of the injected water (Rimassa et al, 2009;Haluszczaket al, 2012;Zolfaghari et al, 2015). For instance, in the Horn River Basin (HRB), slick water (which has similar salinity levels as fresh water) is injected into the reservoir to create fractures (Johnson and Jonson, 2012), while the recovered flowback water is highly saline (40,000 -70,000 ppm) (Bearinger, 2013;Zolfaghari et al, 2014, Engle andCapo et al, 2014).…”

Environmental Issues and Answers Related to Shale Gas Development

“…Typically, flowback water is collected, blended with fresh water, with or without prior treatment, and then re-used in another fracturing treatment. Reuse of the flowback water is feasible as long as concentrations of certain inorganic parameters (e.g., total dissolved solids, chlorides, sulfates, carbonates, calcium, magnesium, barium, and microbes) do not exceed levels that could interfere with the effectiveness of the fracturing fluid (Rimassa et al, 2009;URS, 2009;Burnett and Vavra, 2006). In addition, rather than competing for fresh water supplies, some hydraulic fracturing projects may be able to use alternative water supplies which are not suitable for use as drinking water, such as marginal groundwater resources containing elevated salinity, treated wastewater effluent, impounded stormwater, and once-through cooling water discharge (URS, 2009).…”

Study on Determination of Boron Content in Fracturing Flow-back Fluid by Titration

“…The guar gum, formaldehyde, petroleum and other additives are contained in flow-back fluid, which will cause pollution to the surrounding environment without disposing [3,4] . For arid areas, water resources can be saved effectively and the problem of environmental pollution can be controlled effectively by reusing of flow-back fluid [5] . In the case of reusing, especially in the preparation of fracturing fluid, the residual boron has an impact on the cross-linking.…”