Maturation Studies
Measurement of the reflectance of the maceral vitrinite is a commonly performed analysis that is used to establish the rank of coals or the thermal maturity of petroleum source rocks. A well-established correlation exists between vitrinite reflectance and rank due to increases in the refractive and adsorption indices of vitrinite with increasing aromatization. Coal or source rocks samples are prepared in polished briquettes which are then compared to the reflectance of calibrated glass standards on a reflected light microscope. The USGS is currently involved in maturation studies of coals and rock in support of coalbed methane exploration in Louisiana, Arkansas, and Texas.
Photomicrograph of a carbonaceous shale sample containing small dispersed vitrinite particles. The reflectance of the vitrinite particles can be measured and used to predict the thermal maturity of the host rock.
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U.S. Department of the Interior |
U.S. Geological Survey
