| This dissertation focuses on a portfolio of water management practices in Colorado, USA, consisting of different water strategies that could result in the value of oil and gas operations in the face of consumption and environmental challenges while concurrently assuring communities and environmental activists that freshwater resources are secure. This water management portfolio for hydraulic fracturing is comprised of: (1) treatment of produced and flowback water, (2) optimization of treatment based on the solubility of target salts, reuse and recycling of produced and flowback water, and (3) developing a frac fluid which is more tolerable to brackish water containing organic matter content and dissolved salts. Treatment, recycling, and reuse of produced and flowback water is a smart water management strategy which substantially reduces the societal and environmental externalities of produced water disposal as well as reducing disposal costs and the transport logistics associated with obtaining freshwater and produced water disposal.;Chemical coagulation, physical solid-liquid separation, and filtration are among the current treatment methods applied in the oil and gas industry. Conventional treatment, in particular chemical coagulation, has been neither successful nor cost effective in treating flowback and produced water because of spatial and temporal variability in water quality and high organic matter content. The cost of primary treatment, including removal of suspended solids and oil emulsion is mainly derived by chemical consumption including coagulants, acid and bases. Physicochemical treatment process such as electrocoagulation and softening treatments are one of the common wastewater treatment processes used in USA. In Chapter 4.1 the influence of pH sequencing on electrocoagulation (EC) treatment of flowback and produced water to remove divalent cations, boron, total organic matter (TOC), total dissolved solids (TDS), and turbidity was evaluated. While the results show in most cases softening (raising pH) in front of EC was more effective, no difference in turbidity removal was observed between the two treatment sequences. Although both treatment sequences were more effective in treating produced water samples than flowback samples, the sequence of raising pH before EC was superior in removing the targeted constituents. Optimization of these treatment methods was studied in the following section (4.2) of Chapter 4. Softening before EC was also a better economic option due to the lower pH that reduces chemical consumption during this sequence of treatment. Modeling software (OLI systems) was used to simulate aqueous-based chemical systems and to determine the solubility constants for a variety of salts dissociated in water.;After examination of treatability of produced water and flowback water, the research was directed to assessing the feasibility of reuse of produced and flowback water in hydraulic fracturing. With the increased risks involved with deep well injection, this is an attractive alternative due to inherent reduction of transport of both freshwater and produced water therefore improving production economics and reducing environmental impacts. However, the high content of TOC and TDS associated with flowback and produced water and their impacts on frac fluid stability are largely unknown. A series of laboratory experiments were conducted on high pH zirconium crosslinked guar based polymer and low pH zirconium crosslinked carboxyl methyl cellulose (CMC) based polymer to determine the effects of salt species on the prepared polymer and the range of acceptable salts contents (Chapter 4.3). For this purpose, 80 frac fluid samples were analyzed and the maximum and minimum values of all the contents were determined to investigate the impact factor of each component. Among all the studied cations and ions, calcium, magnesium, sodium, potassium, iron, and phosphorous showed the strongest effect on the frac fluid stability. This effect becomes more pronounced as the ionic strength of the solution increases. Trivalent cations exhibit this behavior, possibly due to their increased ionic strength. They more easily compete with the typically quadrivalent crosslinker, resulting in less available crosslinking sites. A first of the kind water quality standard was developed based on the type of polymer in the frac fluid as a result of this study. Section 4 in Chapter 4 investigates the organic matter influence on the CMC and guar based frac fluids. The organic matter content of flowback water was linked to polymers and surfactants formulated in frac fluid. According to the results of this study, TOC has a negative impact on the stability of both frac fluids. The TOC impact suggests that the residual organic matter crosslinks with the available crosslinker ions and form unstable and weaker polymer chains that generate less viscous and unstable fracking fluids. The chemical composition of the CMC based fluid was optimized at two levels of high and low TDS values and are presented in the last two sections of Chapter 4. (Abstract shortened by UMI.). |
