Abstract: ICA and SPD: New Methods for Determining Thermal Maturity

K. W. Schwab, M. A. Smith, P. Van Gijzel

Problems associated with the vitrinite reflectance (%Ro) technique, including suppression, anisotropy, and particle identification, make it increasingly clear that alternative methods are needed that can accurately define thermal maturation levels throughout a basin.

Two new methods for measuring thermal maturity, based on examination of spores, pollen, and plant tissue fragments in transmitted illumination, have been developed. Integrated Color Analysis (ICA) uses an advanced imaging system and a microscope with high-resolution optics. In Spectral Power Distribution (SPD) analysis, a spectral photometer is used in conjunction with a high-resolution microscope in a manner somewhat analogous to that of van Gijzel (1990). Both methods are calibrated with known standards and provide hue and intensity values. These values are calculated from percentages of red, green, and blue components of the transmitted light spectrum and plotted in a histogram format.

Hue and intensity values have been calculated for thermal maturity scales including Staplin (1969), GeoChem Laboratories (1976), Batten (1976), Robertson Research (SCI), and Geo-Strat (1976). Estimated percent reflectivity (%Ro) can also be predicted.

ICA and SPD measurements have been found to be considerably more accurate than estimated TAI based on spore coloration. The quality of the analytical data is comparable to that derived from the vitrinite reflectance technique but, in our opinion, is also less subjective. In-house studies of well samples show that both new methods provide the explorationist with reliable and accurate results that are highly reproducible. These two systems allow the analyst to produce detailed thermal maturity profiles in numerical and graphical formats for strata with geological ages ranging from Precambrian to the Recent.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994