oa DEMIXING OIL-BASED DRILLING MUD AND RESERVOIR OILS FROM DRILLING CUTTINGS USING ULTRAHIGH RESOLUTION MASS SPECTROMETRY

This study uses ultrahigh resolution mass spectrometry techniques, namely Fourier transform ion cyclotron resonance mass spectrometry (FTICR–MS) to deconvolve and characterize reservoir oils encountered by drilling cuttings that are contaminated by oil-based drilling mud. The hydrocarbon species are ineffective to separate the drilling fluids and the reservoir oils in the cuttings. However, in the non-hydrocarbon fraction, the disappearance of the N1 class monitored in the electrospray negative ion mode and great abundances of the NxOy classes in the DM and the cuttings alike suggest severe contamination of these cuttings by the drilling fluids. In contrast, the N1 class containing cuttings indicate presence of authentic reservoir oils. The triangle plot of the relative proportions of the DBE 9, 12, and 15 groups of the N1 class suggests a PM level range of 1–5 of authentic reservoir oils as well as non-biodegraded reservoir oils contained in the cuttings.