Halotolerant Life in Feast or Famine: Organic Sources of Hydrocarbons and Fixers of Metals

Abstract

A hydrocarbon source rock s generally considered to be a finegrained rock that, during its burial and heating, generates and releases enough fluids to form commercial accumulations of oil or gas (Fig. 9.1a). Back in 1981, Kirkland and Evans made the observation that some 50 % of the world’s oil sequestered in carbonate reservoirs may be associated with mesohaline micritic source rocks. Heresy or not, the notion that much of the oil in carbonate reservoirs, sealed by evaporite salts, may have been sourced in earlier less saline, but still related, evaporitic (mesohaline) conditions, is worthy of consideration. The association between mesohaline waters, the accumulation of organic-rich sediments and the evolution of the resulting evaporitic carbonates into source rocks has been noted by many, including: Woolnough (1937), Sloss (1953), Moody (1959), Dembicki et al. (1976), Oehler et al. (1979), Malek-Aslani (1980), Kirkland and Evans (1981), Jones (1984), Hite et al. (1984), Eugster (1985), Sonnenfeld (1985), Ten Haven et al. (1985), Warren (1986), Evans and Kirkland (1988), Busson (1991), Edgell (1991), Beydoun (1993), Benali et al. (1995), Billo (1996), Aizenshtat et al. (1998), Carroll (1998), Schreiber et al. (2001), Love et al. (2007), Schnyder et al. (2009), Warren (2011), Comer (2012).