Oil and gas produced water (PW) is a hyper-saline (100–250 g/L) industrial effluent containing a variety of organic compounds. Untreated PW discharge into the sea deteriorates water quality globally. The identification of a suitable treatment technology depends on detailed characterization. Understanding the structure of micro- and nano-organics in PW streams is crucial for elucidating their fouling or leaking potential in membrane processes. Both qualitative and quantitative analysis were performed to identify such organics. Cryo-transition electron microscopy (Cryo-TEM) confirmed the presence of micro-pollutants (>20 nm) in PW streams, which can cause partial pore wetting in the membrane distillation (MD) process. Oxygenated polar molecules dominate the organics, compared to nonpolar hydrocarbons. While some organics are derived directly from crude oil, the majority are chemical additives. Acetic acid was completely rejected (100%) and formic acid by 98% in the MD process, demonstrating its suitability for PW treatment.