Comparison between oily and coal seam gas produced water with respet to quantity, characteritics amd treatment technologies: a review
Oil and gas are significant sources of energy worldwide, and their importance increases due to the ever increasing global demand for energy. The production of conventional oil, atural gas, and unconventional gas, for example, of coal seam gas (CSG) or coal bed methane, is usually accompanied with contaminated water. This article reviews the similarities and differences between the water produced during exploitation of conventional hydrocarbon and unconventional CSG resources in terms of quantity, characteristics, current treatment and a promising alternative treatment that can be used. The volume of produced water from conventional oil and gas exploitation increases during the operating life of a well. In contrast, in CSG exploitation, produced water is generated from an early stage in large volumes. Characteristics of oily and CSG produced water differ considerably from each other in terms of organic content (e.g. the occurrence of oil and grease and specific petroleum organic contaminants such as benzene, toluene, ethylbenzene, and xylene or BTEX), ionic composition and total dissolved solids. In general, methods for treating and disposing oily produced water are more established but somewhat less stringent given the long history of conventional oil and gas extraction. On the other hand, the treatment of CSG produced water requires a more comprehensive and stringent treatment train and almost always involves reverse osmosis filtration, particularly if the treated water is for beneficial reuse. Membrane filtration technologies have played and will continue to play a major role in the treatment of produced water. Several new membrane processes, particularly forward osmosis, have also emerged as notable candidate technologies for sustainable management of produced water from the oil and gas industry.