Thermal Decomposition of Hydrocarbons in the Cerro Prieto, Mexico, Geothermal Reservoir

Abstract

The distribution of low molecular weight hydrocarbons in geothermal systems depends on hydrocarbon sources and temperature/time regime. In the Cerro Prieto, Mexico, geothermal reservoir, thermal decomposition of coal to form methane is extensive at temperatures near 340°C. In high temperature wells, only methane, ethane, propane, and benzene are present. At temperatures near 290°C, thermal decomposition is extensive, as evidenced by such intermediate products as N-butane, N-pentane and C4 and C5 branched hydrocarbons. The wide variety of hydrocarbons and low concentrations of methane relative to other hydrocarbons in surface samples indicate only moderate thermal decomposition of the source carbon and intermediate hydrocarbons.