Abstract: A method for evaluating the API gravity of a sample of underground formation includes steps of:Solvating a known volume of an underground formation sample in a known volume of a solvent which will solvate hydrocarbons;Quantitatively measuring with a changeable filter portable fluorometer the emission fluorescence of the solvated sample at a fixed excitation wavelength with measurements of emission intensities at two points;characterizing the oil by the ratio of two emission intensities obtained at a fixed excitation wavelength;determining the yield;applying regression analysis to a data base of oils to obtain an equation which results in an algorithm value; andinterpreting the value of the algorithm to give a value for API gravity and estimate in-situ oil concentration.

Abstract: Methods are disclosed for evaluating wet cutting from a well borehole to determine the hydrocarbon content of the earth formations penetrated by the well borehole. The wet cuttings to be measured are mixed with a polar hydrocarbon solvent which has both hydrophilic and hydrophilic properties. The solution of the solvent and cutting is filtered and then its emission (fluorescence) spectrum is measured by irradiating it with ultraviolet radiation excitation at wavelengths at which most petroleum compounds fluoresce. The hydrocarbon content of the sample wet cuttings is then determined by comparing its fluorescence emission to the emission fluorescence of known samples.