The Influence of Pressure on the Thermal Cracking of Oil

Abstract

The influence of pressure on gas, liquid, and solid products of thermal cracking of a C9+ fraction of a saturate-rich Devonian oil from the Western Canada Basin has been investigated. Confined pyrolysis was performed in sealed gold tubes at 350, 380, and 400 °C and pressures ranging from 90 to 2000 bar for 72 h. At the temperatures investigated, the effect of pressure on oil cracking and product generation is small. Rates of early hydrocarbon gas generation (350 and 380 °C, 72 h) decrease with increasing pressure by 9−15% in the 90−210 bar range and by 7% for gas generation (400 °C, 72 h) in the 90−345 bar range. Gas generation rates then steadily increase 10−15% to a maximum at 690 bar for all temperatures. From 690 to 2000 bar, the rates of gas generation steadily decrease by 5−17%. Activation volume values were estimated to be ΔV⧧ = 47 cm3/mol in the 90−210 bar range, ΔV⧧ = −14 cm3/mol in the 345−690 bar range and ΔV⧧ = 5 cm3/mol in the 690−2000 bar range. Extrapolation of results to geologic condition...