Study on the Suppression of Vitrinite Reflectance: A Thermal Simulation Experiment

Area of Science:

• Geochemistry
• Organic Petrology
• Sedimentary Basin Analysis

Background:

• Vitrinite reflectance (R0) is crucial for reconstructing thermal history and assessing source rock maturation.
• Reported suppression of R0 can compromise the accuracy of thermal evolution evaluations.

Purpose of the Study:

• To investigate the impact of hydrocarbon generation on vitrinite reflectance during thermal evolution.
• To elucidate the mechanisms behind R0 suppression in a closed system.

Main Methods:

• Controlled thermal simulation experiments in a closed system.
• Analysis of vitrinite reflectance under varying thermal conditions and kerogen types.

Main Results:

• Hydrocarbon absorption and overpressure were identified as key factors suppressing vitrinite reflectance.
• For R0 values between 0.6% and 2.1%, hydrocarbon impregnation of telocollinite texture by type I kerogen was the primary cause.
• Above 2.1% R0, overpressure emerged as the dominant factor for anomalous reflectance.

Conclusions:

• Hydrocarbon generation significantly influences vitrinite reflectance, leading to suppression.
• The mechanisms of suppression vary with R0 values, involving hydrocarbon impregnation and overpressure.
• Closed-system conditions, retaining volatile products, hinder vitrinite structural reorganization and cause reflectance suppression.