To examine the role of water in the interaction of organic matter with smectite in argillaceous source rocks with situ DRIFTS

we make a study of clays with grainsize less than 2μm extracted from hydrocarbon source rocks with high clay content in the Neocene

Jiyang Depression

eastern China. The DRIFT spectra show that the evolution of the adsorption water is accompanied by significant changes in the location and shape of the carboxyl above 250°C and both of them almost disappear at 400℃. An attempt for semiquantitative measurement of vibration peaks is also carried out. Result shows that the loss of adsorption water and carboxyl are in proportion above 250°C

suggesting most carboxylic acids interact with interlayer hydrated cations of smectite through hydrogen bond

and water molecules are bridges between carboxylic acids and smectite

a most important mechanism for organosmectite interaction. Due to the effect of water bridge

dehydrate temperature of water and carboxylic acids are higher than that of pure smectite and carboxylic acids. As water bridge breakdown at higher temperature

water molecules and carboxylic acids were expelled from interlayer of smectite simultaneously. The water bridge mechanism of organosmectite interaction and dehydration lagging of water bridge and carboxylic acids have a great influence on hydrocarbon generation

expulsion and primary migration. 