Novel Osmotically Driven Membrane Processes for Treatment of Oil and Gas Exploration and Production Wastewater

The US currently experiences a rapid growth in unconventional oil and gas exploration and production (E&P). Consequently, there is an ever-increasing demand for water, for well exploration and stimulation (>5 million gallons/well). The wastewater generated during E&P contains chemicals that assist in drilling and hydraulic fracturing, minerals leached from formations, and organic and inorganic constituents. Ultimately, this water is permanently removed from the local fresh water cycle, as deep well injection is the current method of disposal; which can be perceived as an environmental threat to local groundwater supplies when conducted improperly. In order to be reused in further gas field explorations and minimize the environmental impacts on local water supplies, low cost treatment is necessary that is robust under harsh operating conditions and minimal field resources.

Forward osmosis (FO) is an emerging membrane treatment technology that can properly treat oil and gas E&P wastewater for reuse. In FO, a concentrated draw solution induces an osmotic pressure gradient across a semipermeable membrane to extract water from impaired streams. The use of FO has already shown many advantages in the treatment of E&P wastewater: low hydraulic pressure operation, reduced fouling propensity compared to pressure-driven processes (RO), and substantial rejection of known contaminants found in oil and gas produced wastewater. While field and pilot testing has proved promising, little is known about the fouling propensity and its effects on FO process efficiency when treating oil and gas saline E&P wastewater.

The current investigation evaluates the elemental composition of drilling mud, frac flowback, and produced water and the fouling properties it imparts on the FO membrane. The main objectives of the study include quantification of reduced water flux due to the effects of concentration polarization, identification of potential elemental surface interactions involved in irreversible fouling, and the optimization of FO operating conditions to maintain high process efficiency and sustainability. Results from ongoing experiments will be presented and the energy demand, chemical demand, and operating conditions will be discussed.