Land treatment of oily saline drilling wastes is problematic in low pH, high iron and aluminum activity soils commonly found in China, Southeast Asia, South America and North America. Problems stem from the addition of salts promoting hydrolysis of iron and aluminum acidity and exacerbates an often extreme (pH < 4.0) acid reaction. Most drilling wastes are strongly alkaline and offer a beneficial neutralization reaction when mixed with native acid soils. However, land treating of oily saline drilling wastes generally is ‘limited’ by either the petroleum hydrocarbon content or salinity before sufficient base is added to neutralize excess acid in the receiving native soil.
The paper offers a practical and economical means of managing potentially problematic reactions by the prophylactic treatment of oily saline drilling wastes with agricultural grade, hydrated lime (calcium hydroxide) prior to land application.
The results presented show hydrated lime reacts with the oil-base drill cuttings:acid soil mixture in a manner promoting the biological degradation of the oil. Lime also functions to sequester free oil fractions making it easier to land apply oily wastes and control application rates. Free lime neutralizes excess soil acidity. The high pH associated with hydrated lime is ameliorated in the lime:drilling waste:receiving soil blend by fixation of atmospheric carbon dioxide to a pH < 8.3 s.u. The data suggests the optimum lime application is equivalent to the total petroleum hydrocarbon (TPH) content as measured on a dry weight basis.