Oilfield brine is the largest volume of waste generated by the oil and gas industry; typical produced brine volumes may easily exceed the oil production by 10 times with total dissolved solids ranging from 1,000 to over 250,000 ppm. Handling costs of produced brine may lead to the premature abandonment of many oil and gas wells. At the same time that oil and gas operators are trying to cope with excess produced water, many states are critically short of freshwater resources.
This paper describes and validates a process to treat this brine to meet the standards for irrigation-quality water. Components of the proposed brine-conversion plant include both microfiltration and a pretreatment system for the removal of solid particles and oil using sorption pellets made of a modified clay material, and reverse osmosis (RO) units with a variety of interchangeable semipermeable membranes for the removal of dissolved salts.
We collected experimental data for oil/water separation of controlled mixtures using packed columns with modified clay particles. The average oil loading capacity of these particles is better than activated carbon (over 60%) and our experimental results indicate that packed beds can remove over 90% of the oil.
We screened a variety of RO membranes and selected one to conduct a series of experiments with brines with salinity up to 40,000 ppm, transmembrane pressures up to 1,000 psia, and various rates.Our experiments indicate salt rejections of 95 to 99% depending upon the initial salt concentration, transmembrane pressure, and rate.
Based upon these experiments, we modeled and coupled these two processes. Our model can scale up a process to any desired throughput rate and concentration specifications.Simulation results indicate that at proper integration and configuration of oil adsorption and RO units, depending upon initial total dissolved solids (TDS), up to 90% of the brine may be recovered as fresh water.
The general approach for produced water treatment is de-oiling and demineralizing before disposal or use. The removal of oil and grease from produced water has been discussed in the literature by using downhole separators; centrifuges; air floaters, emulsifiers, and hydrocyclones; membrane separators; and adsorbers.In comparison with the many oil-removal techniques, membrane technologies can be efficient, do not create additional waste product, but require large power, and membranes foul frequently and require periodic maintenance. Gravity-separation techniques lose oil-removal efficiency at lower oil concentrations. Oil adsorption is a cheaper and feasible technique although it requires disposal of the used adsorbent media. Produced oilfield brines typically contain oil ranging from 30 to 200 ppm, expressed as total organic carbon (TOC). For demineralization purposes, several methods such as microfiltration (MF), ultrafiltration (UF), ion exchange, and reverse osmosis (RO) are available.[6,7,8] Roberts6 showed considerable reduction in demineralization cost with RO operation. Evans et al. discussed several options for handling produced water including disposal, reinjection, and treatment. Disposal of produced water requires meeting stringent environmental regulations. Produced water reinjection requires skillful planning and treatment to meet the needed quality of reinjection water to avoid formation damage. Mackay et al. described risk involved in reinjection. Wan et al. showed that treatment of produced water before reinjection gives better performance. Alonzo et al. assessed the produced-water treatment and disposal practices and addressed the research needs in this area. Hughes et al., Tao et al. and Tsang et al. discussed conversion of produced water into irrigation or drinking-quality water in their work. None of these works provides sufficient information on modeling the separation processes for application of produced-water treatments. Here we provide a dynamic model integrating oil adsorption and salt removal using a specific type of organoclay (OC) packed beds and RO units.We based our model upon our experimental characterization of the performance of the organoclay and the RO membrane selected and a rigorous material-balance computation.