Water. desalination + reuse

TECHNOLOGY Figure 2: Flowback Water Quality Variability THird STEp – FLuid CHaraCTErizaTiON Having identified the anticipated water requirements, flowback volumes, level of activity, and targeted water quality guidelines, the next step of the project focused on characterizing the fresh (frac water), flowback and produced waters from each of the respective Penn West Exploration tight-oil developments. Fresh water samples were collected from the frac water supply manifold, flowback samples were collected from the testers manifold and produced water samples were collected from either the treaters at various batteries or wellheads. Each sample was analyzed for common cations, anions, pH, TSS, TDS, and presence/absence for H2S as outlined in Table 5. As demonstrated by the data, the variability in fluid composition is most apparent with total hardness, sodium, chloride, strontium, and sulphates for the Carbonates resource play. In addition to the analytical data Figure 2 shows a set of samples from the Carbonates that were obtained during various phases of the hydraulic fracturing process in October of 2011. Sample A represents fresh water that has been filtered and disinfected with biocide prior to the addition of the hydraulic fracturing crosslinked chemistries. This sample provides a baseline representing the current quality of water typically being utilized for tightoil hydraulic fracturing across the WCSB. The wide range in flowback water quality is observed with samples B through F. Sample B is flowback water with very little residual oil content, however the Figure 3: Flowback & Produced Water Treatment Decision Tree residual gelling agent concentration is preventing the very fine suspended solids from settling out of the solution. Similar to sample B, sample C is observed to have an even greater concentration of oil coated solids remaining in solution that are also likely attributed to an excess concentration of residual gelling agent present within the flowback water. In contrast to samples B and C, the distinct stratification layers of sample D suggests very little residual gelling agent present within the flowback sample. The solids present in sample D readily settled out of solution and the free oil has accumulated as the top layer within the sample. The layer of oil and fine solids at the surface of sample E, combined with the distinct layer of oil-coated solids at the bottom of the sample, suggests a lesser concentration of residual gelling agent within this flowback sample compared to samples B and C. Lastly, the homogenous | 30 | Desalination & Water Reuse | August-September 2013 nature of sample F suggests a very stable reverse (oil-in-water) emulsion. The magnitude of fluid variability must be taken into consideration as fluctuations in residual gelling agent concentration, solids loading, particle size, oil content, oil droplet size, and general water quality will add further strain to downstream water treatment technologies. Processing a fluid of a known quality is far more manageable than treating a fluid that is in a constant state of flux. FOurTH STEp – TrEaTmENT mETHOdOLOGY With the data collected combined with the outlined water quality guidelines, six-stages of treatment were identified for addressing the maximum treatment necessary to condition flowback and produced waters for reuse in hydraulic fracturing for tight-oil developments. The six proposed treatment objectives include: de-oiling and solids removal, pre-treatment, solids and soluble Cont. 53

• Cover