TECHNOLOGY STATUS ASSESSMENT
by James W. Castle and John H. Rodgers, Jr.
Clemson University, November 2008
1 Current State of Technology
1.1 Summary of Existing Industry/Sector
New technologies and advances in existing technologies are needed to minimize environmental impacts associated with hydrocarbon production from our nation’s conventional and unconventional resources. Unconventional resources currently account for 30% of U.S. gas production, and the importance of unconventional gas is expected to increase in the next 25 years (NPC, 2007). Production of both conventional and unconventional oil and gas generates large volumes of water. Handling of these large volumes of produced water and the associated costs have limited the development of both conventional and unconventional reservoirs (e.g. Anderson et al., 2003). Because development of oil and gas resources is becoming increasingly constrained due to environmental concerns and regulations, new methods are needed for the efficient handling of produced water using environmentally acceptable and economically viable technology.
1.2 Technologies/Tools Being Used
The most common mode of handling produced water is reinjection into designated geological formations (API, 2000). Cost can be high, and geological formations suitable for injection must be available. Although the cost may be affordable for larger exploration and production facilities, the expense of reinjecting produced water is commonly a significant economic burden for smaller or older facilities. Injection is becoming increasingly regulated, and requirements regarding quality and quantity of injected fluids are becoming more stringent
Thermal processes, including distillation, can be effective in reducing water volumes requiring reinjection, but cost can be high because of the large amount of energy required
(Fenton, 1983; Semiat, 2000). The solar-desalination still uses the sun’s radiation to evaporate saline water and produce a vapor. In the solar pond desalination method, water evaporates to form a highly concentrated salt solution that typically occurs at the bottom of the pond with an overlying layer of lower salinity, diluted water. Application of the solar pond technique to desalination is limited because of technical difficulties and low efficiency (Semiat, 2000). However, recent studies (e.g., Gilron et al., 2003; Arnal et al., 2005) have demonstrated that the use of wet porous materials on the surface of evaporation ponds can increase evaporation rates and promote crystallization of solids that may have commercial value. The freeze/thaw method of desalination, which involves production of salt-free ice, holds some promise in colder climates where natural freezing can be coupled with evaporative processes (Boysen et al., 1996, 2002).
The reverse osmosis (RO) membrane technique is the most promising and fastest-growing desalination method and is the most commonly used process for reducing ionic concentration in seawater. Quality of water after treatment by RO depends on membrane rejection properties, degree of water recovery, and proper system design (Semiat, 2000; Humphries and Wood, 2004). Membranes are sensitive to changes in pH, temperature, small concentrations of oxidized substances such as chlorine oxides, a wide range of organic materials, and the presence of algae and bacteria. The permeate from RO may require additional treatment before discharge or reuse because certain compounds, particularly small molecules such as
