Characteristics of hydrocarbon and gas generation process from pyrolyzed crude oils in Tarim basinCharacteristics of hydrocarbon and gas generation process from pyrolyzed crude oils in Tarim basin

Abstract：In order to reveal the generation process of gas during cracking of crude oil, the char- acteristics of hydrocarbon and pyrolysis evolution laws for different crude oils were studied u- sing thermal simulation experiment. Using pyrolysis experiment to crack crude oils in a closed gold tube system under 50 MPa pressure, and combined with quantitative analyses of pyroly-sate gases using gas chromatography and gas chromatograph-isotopic ratio mass spectrometer, the hydrocarbon characteristics of yields, carbon isotope ratios and pyrolysate gas generation process during cracking of Yaha and Hade crude oils in Tarim Basin were studied. It was proposed that cracking of crude oil has a high gas generation potential and yields more gases in the high evolution stage. It was founded out that the gas generation during cracking of crude oil is a two staged evolution process. The results show that the total gas yields from Yaha and Hade crude oils were high, with C1-5 yields of 738. 87 mL/g and 598. 98 mL/g, respectively. The yields of methane and bitumen generated from the Yaha and Hade crude oils increased with increase of pyrolysis temperature. The yields of C2-5 and C6-14 firstly increased and then decrease, while those of C14＋ decreased with increasing pyrolysis temperature. The δ^13 C1 value was light at first, but gradually became heavier with the increasing pyrolysis temperature. However, the δ^13 C2 and δ^13 C3 values became heavier with increasing pyrolysis temperature. The gas generation process during cracking of crude oil is classified into two stages. The first stage is mainly the pyrolysis of liquid hydrocarbons to produce wet gas, while the second stage is the methane and bitumen production through cracking of C2-5 gases. Analyzing the characteristics of hydrocarbons and the process of gas generation during cracking of different crude oils are very important for studying the hydrocarbon generation mechanism from crude oil pyrolysis.