... PW quality also differs Table 1 Estimates of water-to-oil ratios (WOR = m 3 of produced water/m 3 of oil produced), water-to-gas ratios (WGR = m 3 of produced water/1000 m 3 of gas produced), and total volumes of produced water (PW) by type of production and country or region located in drylands. (Burnett, 2004); 9 (Clark and Veil, 2015); 10 (Digital H2O, 2015); 11 (Sharr, 2014); 12 (Waterfind, 2016); 13 (Jacobs Consultancy, 2010); 14 (Commonwealth of Australia, 2014); 15 (IESC, 2014); 16 (Blackam, 2017); 17 (Robles, 2016); 18 (Waldron, 2005); 19 (Al-Haddabi et al., 2015); 20 (Keesom et al., 2009); 21 (Sorkhabi, 2010); 22 (Kuraimid, 2013); 23 (Breuer, 2011); 24 (Al-Mahrooqi et al., 2007); 25 (Alanezi, 2016); 26 (Ahan, 2014); 27 (Gulf Intelligence, 2016); 28 (Rice and Nuccio, 2000); 29 (NSW Government, 2013); 30 (Scanlon et al., 2014); 31 (Gordon, 2015); 32 (Kurz et al., 2016); 33 (Terrel, 2015); 34 (Vaz and Di Falco, 2011); 35 (Williams and Simmons et al., 2013); 36 (Miller, 2010). ...