Wellsite kerogen maturity determination utilizing raman spectroscopy

A method for determining the maturity of a formation sample, comprising:

• obtaining cuttings of the formation sample from drilling fluid at a wellbore;
• at the wellbore, cleaning the cuttings to remove residues of drilling fluid and reservoir fluid to obtain a cleaned sample;
• at the wellbore, performing Raman spectroscopic measurements on the cleaned sample to obtain a Raman spectrum for the sample;
• fitting at least a G (graphite) peak and a D1 (defect) peak to the Raman spectrum to obtain Raman shift values for the G peak and the D1 peak and a Raman band separation (RBS) value;
• using the RBS to generate a vitrinite reflectance equivalent (VRe) value using a relationship correlating RBS to VRe;
• and
• displaying the VRe as an indicator of formation sample maturity for a depth in the formation from which the sample was obtained.

A method for providing indications of the maturity of a formation traversed by a wellbore as a function of formation depth, comprising:

• at the wellbore, obtaining separate cutting samples of the formation from wellbore drilling fluid respectively representing the formation at multiple formation depths;
• at the wellbore, cleaning the cutting samples to remove residues of drilling fluid and reservoir fluid to obtain cleaned samples respectively representing the multiple formation depths;
• at the wellbore, for each of the cleaned samples, performing Raman spectroscopic measurements to obtain Raman spectra for the samples respectively representing the multiple formation depths;
• for each formation depth, fitting at least a G (graphite) peak and a D1 (defect) peak to each Raman spectrum to obtain Raman shift values for the G peak and the D1 peak and a Raman band separation (RBS) value for that formation depth;
• for each formation depth, using the RBS to generate a vitrinite reflectance equivalent (VRe) value for that formation depth using a relationship correlating RBS to VRe;
• and
• for each formation depth, displaying in log format the VRe as an indicator of formation sample maturity for that depth in the formation.