An in-hole oil-drilling probe is mountable in a drill string to measure hydrocarbon concentrations in drilling fluid flowing around the drill string. The probe consists of a drill collar which is mountable in the drill string. A solvent, in which hydrocarbons are soluble, circulates within the drill...http://www.google.com/patents/US5351532?utm_source=gb-gplus-sharePatent US5351532 - Methods and apparatus for making chemical concentration measurements in a sub-surface exploration probe
