Qualifying classes of organic compounds within unprocessed produced water using ¹H-NMR analysis

Abstract

Produced water (PW) is defined as any ground- or flowback water recovered during the process of petroleum extraction. This water is highly heterogeneous, containing many different organic compounds associated with petroleum reservoirs. It is typically more saline than marine waters as well. Studies of produced water tend examine specific fractions of organic compounds present; in this study, we examined unprocessed samples of produced water using ¹H-NMR, to create a qualitative profile of organic molecular functional groups present. Thirty samples of produced water were analyzed using a PE-ES-WATERGATE water suppression NMR experiment using an 800MHz NMR. Resulting spectra were then divided into discrete regions, broadly representative of the types of functional groups present. The conclusions of this research support this methodology’s usage for produced water – while challenging, unprocessed PW can be successfully analyzed using NMR and meaningfully interpreted through spectral binning. Additionally, this methodology may be able to approximate the location of samples with unknown provenance, as Anadarko Basin PW samples with known and unknown origins displayed numerous similar spectral characteristics. However, certain classes of organic functional groups, namely those indicative of alkenes, were almost entirely absent from analysis. This absence must be fully investigated to determine whether there is a methodological bias against them or not.