Mitigating the prospect of mercury in hydrocarbons in exploratory drilling by Erica Knear, King & Spalding LLP, September 3 2013, Lexology
Today’s oil and gas exploration increasingly involves drilling deeper, increasing the likelihood of encountering elevated levels of naturally-occurring mercury in hydrocarbons found at these advanced depths. Hydrocarbons with elevated mercury levels traditionally have been associated with a limited number of regions around the world. The deep drilling now occurring is producing elevated mercury in hydrocarbons in regions that have not previously experienced the phenomenon. This can lead to damage downstream from the wells in processing equipment. Of particular concern is mercury corrosion, commonly known as liquid metal embrittlement or LME, of equipment that has not been “hardened.” The presence of elevated levels of mercury in oil and gas feed stocks also can require additional environmental and health and safety controls that are well known throughout the industry but have traditionally been implemented only in regions known to experience elevated mercury. For these reasons, elevated mercury hydrocarbons frequently carry a significant price discount in world markets.
E&P companies now frequently drill very close to the basement rock in highly volcanic areas. Basement rock underlays the deepest layers commonly drilled to previously and overlays the magma that is constantly working its way up to the earth’s mantle. Put another way, it is about as deep as one can drill without hitting molten rock. Deeper drilling means higher temperatures, which create more opportunities to encounter mercury trying to escape radiating geothermal energy and push toward the surface. As a result, companies drilling into the basement rock layer may encounter elevated levels of mercury in the produced hydrocarbons. Produced water can also contain elevated mercury levels, which creates additional handling and disposal issues. [Emphasis added]