Changes in Microstructure and Elastic Properties of Mancos Shale after Pyrolysis

Abstract

We have studied changes of static and dynamic elastic properties of the organic-rich Mancos shale caused by heating to the temperature within the range 380 deg.C-550 deg.C. An increase of ultrasonic velocities and static Young’s moduli has been observed in the samples that experienced temperatures up to ~400 deg. C. Further heating to temperatures up to 550 deg.C has led to the decrease of elastic moduli. The samples subjected to temperatures above 430 deg.C show an increase in stress sensitivity, which implies microcrack generation. Micro-CT images of small samples have been obtained to inspect the microstructural changes caused by this dry pyrolysis. Comparison of the registered micro-CT images of Mancos shale samples subjected to temperatures up to 470 deg.C shows significant shrinkage of the kerogen that fills pore spaces resulted from bitumen expulsion into the pores.