Advances in sampling and analytical instruments permit the isotopic analysis of very small amounts of hydrocarbons that are collected from the circulating mud stream during drilling. This new technique provides detailed isotope logging and is called mud gas isotope logging (MGIL;Ellis et al., 2003). MGIL provides useful information on petroleum exploration and production, such as origin of gas, thermal maturity, assessment of seal effectiveness, and identification of hydrocarbon-charged intervals.
