Organic Chemical Characterization and Mass Balance of a Hydraulically Fractured Well: From Fracturing Fluid to Produced Water over 405 Days

Abstract

A long-term field study (405 days) of a hydraulically fractured well from the Niobrara Formation in the Denver-Julesburg Basin was completed. Characterization of organic chemicals used in hydraulic fracturing and their changes through time, from the preinjected fracturing fluid to the produced water, was conducted. The characterization consisted of a mass balance by dissolved organic carbon (DOC), volatile organic analysis by gas chromatography/mass spectrometry, and nonvolatile organic analysis by liquid chromatography/mass spectrometry. DOC decreased from 1500 mg/L in initial flowback to 200 mg/L in the final produced water. Only ∼11% of the injected DOC returned by the end of the study, with this 11% representing a maximum fraction returned since the formation itself contributes DOC. Furthermore, the majority of returning DOC was of the hydrophilic fraction (60-85%). Volatile organic compound analysis revealed substantial concentrations of individual BTEX compounds (0.1-11 mg/L) over the 405-day study. Nonvolatile organic compounds identified were polyethylene glycols (PEGs), polypropylene glycols (PPG), linear alkyl-ethoxylates, and triisopropanolamine (TIPA). The distribution of PEGs, PPGs, and TIPA and their ubiquitous presence in our samples and the literature illustrate their potential as organic tracers for treatment operations or in the event of an environmental spill.

Evaluation of a nanoporous lyotropic liquid crystal polymer membrane for the treatment of hydraulic fracturing produced water via cross-flow filtration

“…The quality of the raw PW, collected for this study from the Denver-Julesburg Basin in northeastern Colorado, was similar to that of other samples collected from the same basin [14,18,52,53]. The concentrations of ions and trace metals present in the raw PW are provided in Table D1 in the Data in Brief, while the general water quality of the raw PW is provided in Table 1.…”

A geospatially resolved database of hydraulic fracturing wells for chemical transformation assessment

“…To date, we are limited to a handful of observations that conrm the presence of halogenated chemicals, including THMs, in basins where their formation was anticipated by the model. 19,21,28,77 As of now, the two case studies investigated here offer just a limited vision for the scope of this evaluation tool to leverage known subsurface pathways and well parameters. While experimental capacities improve and the eld characterizes more subsurface transformation pathways and physicochemical interactions, this framework provides a critical rst step towards truly predictive modeling of owback composition and environmental risk.…”

“…Inputs included the appended pH, temperature, and bromide concentrations for each well location. When choosing a timescale to model, we opted to bridge the differing scales between expected reaction time from the model's source study (6-168 h) 47 and the wide-ranging, potentially monthslong, shut in times as owback uids return to the surface, as consistent with the temporal analyses by Rosenblum et al 13,21 and Stringfellow and Camarillo. 62 This factor is further complicated by the existence of "shut-in" times, where the well is closed and water is not allowed to return to the surface for some period of time that can be widely variable.…”

“…However, to date, only 238 owback and produced samples have been analyzed to identify specic organic compounds in the published literature. 2 This small number of analyses have included inorganic [11][12][13][14][15][16][17] and organic 2,18-25 components of owback water, but the vast well-to-well diversity (spatially and temporally 13,21 ) and comparably complex suites of disclosed additives 26,27 pose massive hurdles for complete characterization at the eld's current pace. In particular, a high degree of uncertainty remains regarding the nature of anthropogenic additives themselves and their capacities to persist or transform in the subsurface.…”

Mechanical degradation of polyacrylamide at ultra high deformation rates during hydraulic fracturing

“…The fate of hydraulic fracturing chemicals when injected into the deep subsurface is still poorly understood, yet they strongly impact the resulting wastewater quality and thus the possible environmental impact of accidental spills or storage pond leakages of wastewater. Chemical and biological transformations of these chemicals have been previously discussed; [1][2][3] mechanical degradation is an additional pathway that could be of significant importance to high molecular weight (MW) polymer chemicals. During HVHF operations, fluids containing ultrahigh MW polyacrylamide (PAM) (2 × 10 7 Da) are pumped at high flow rates down through the wellbore and into tight shale formations, creating highly permeable fractures under high hydraulic pressure (up to 10 000 psi (ref.…”