Using Geothermal Solutions to Desalinate Oil Field Water

Clean water — it’s a precious resource in hot demand right now, for more than taking a shower or watering our crops. The United Nations projects the world’s population will grow by another billion people, to 8.4 Billion, by 2030. More people means more need for food, water, electricity, and other necessities. Beyond the obvious demands for water, our increasing appetite for electricity also requires water — and plenty of it. Most of the electricity generated in the U.S. uses water in some capacity.

When the Sierra Nevada snowpack is at 65 year low, there will be serious water shortages in California  that can affect us all.  Droughts can be powerful motivators for innovative water efficiency and conservation measures, and have led to the development of innovative technologies, such as desalination of brackish ground water, produced oil field water, or seawater.  Certainly these technologies hold tremendous promise, particularly in places where high salinity waters outweigh the freshwater supply significantly — places like Texas, where brackish water is produced from oil and gas wells.

Texas also happens to be a large agricultural user of fresh water, especially in the southernmost part of the state, in the Rio Grande Valley where cotton, ‘Ruby Red Grapefruits’, ‘Texas 1015 onions’,  grain sorghum, melons, sugar cane, and other crops are plentiful — but not without the help of irrigation systems.   In fact, according to the US Geological Survey (USGS), irrigation accounts for the largest use of fresh water throughout the U.S.  Because the Valley is experiencing rapid population growth, the demands for water will only increase.  The International Boundary & Water Commission projects the area’s municipal water needs to increase by a whopping 100 percent in the next 50 years and industrial use to increase by 40 percent.  The current source for nearly all of the Valley’s water?  The Rio Grande River: subject to extreme weather fluctuations, beginning to experience higher salinity conditions, and an international boundary. 

What if one of the most derided users of fresh water — the oil and gas extraction process — could actually contribute to the solution?  While plenty of water is recovered from oil and gas well operations, it actually takes a significant amount of power to desalinate brackish ground water or produced oil/gas field water to the point that it is suitable for humans, livestock or irrigation use. However, utilizing the thermal energy of the fluids produced from wells to power the desalination of the water could provide clean water with little to no grid-supplied electricity.  Instead of trucking the produced water to a disposal well, at both considerable environmental and dollar expense, much of this unsuitable water could become a source of potable water.  In sufficient quantity, water could evolve from an expense into a revenue stream for oil field operators.

The SMU Geothermal Laboratory, the National Renewable Energy Laboratory (NREL), the Bureau of Economic Geology at the University of Texas and others have analyzed the geothermal resource potential of Texas, and it holds tremendous promise.  Capturing even just 14 percent of the heat beneath Texas could provide nearly 300,000 MegaWatts of electrical generation capacity for years and years — that’s almost three times Texas’ total electrical generation capacity from all sources (GRC Trans. Vol 25, Blackwell et al, 2011).  Distinctly different from the very high temperature steam fields of California and Nevada, the geopressure-geothermal resource along most of the Gulf Coast is lower temperature and fairly deep, with temperatures in the area averaging ~200°F at 12,000 feet, transitioning to  ~400°F by 21,000 feet.  Although in areas of South Texas, the heat is significantly closer to the surface.

While years ago, drilling to such depths may have been cost prohibitive, it is now fairly routine in Texas.  In fact, of the 4,803 drilling permits approved in South Texas’ Railroad Commission District 4 since 1/1/2011, 30 percent were for depths exceeding 12,000 feet, with 6 percent exceeding 17,000 feet (data query on 4/6/2015).

Some communities in the Rio Grande Valley are devoting serious study to the viability of utilizing geothermal energy to power desalination of water — either brackish groundwater or produced water from the oil and gas extraction process.  One of the Valley’s largest municipalities, the City of McAllen’s Public Utility Board, is considering this option as it looks to provide a sustainable source for the forecasted demand for added potable water.  Relevant issues will include the water chemistry, flow rates, temperatures at depth, land use access considerations, and more.

The SMU Geothermal Laboratory, based at Southern Methodist University’s campus in Dallas, Texas, has been a world leader in geothermal mapping and resource assessment for the last 45 years. Those interested in learning more about desalination and other innovative uses of geothermal energy in oil and gas fields are invited to register to attend the upcoming conference and workshop, Power Plays: Geothermal Energy in Oil and Gas Fields which will be held on the SMU Campus in Dallas on May 18-20, 2015. 

We can’t live without clean water, and going forward we are going to need to utilize existing and innovative solutions for obtaining clean, safe and sustainable water.   

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