A method for detecting crude oil or gas in a drilling sample includes introducing a drilling sample into a sample solution containing nano particles, illuminating the sample solution comprising the drilling sample and the nano particles by a laser beam, collecting light scattered by the drilling sample and the nano particles in the sample solution, obtaining a Raman spectrum from the light scattered by the drilling sample and the nano particles in the sample solution, identifying, in the Raman spectrum, a spectral signature associated with a substance around a predetermined Raman shift, and detecting targeted chemicals correlated with crude oil or gas existence underground from where the drilling sample, based on the spectral signature of the substance in the Raman spectrum.