塔里木盆地原油裂解生烃特征与生气过程研究

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

为了揭示原油裂解生气过程,用热模拟实验方法研究了不同原油裂解生烃特征与演化规律.采用50MPa压力下封闭体系黄金管原油热解实验,使用气相色谱定量、色谱-同位素质谱分析,研究了塔里木盆地牙哈和哈得原油样品热解生烃产率、碳同位素特征及其生气过程.提出原油裂解生气潜力大,在高演化阶段仍有较大的生气产率,发现了原油裂解生气的"二段式"演化过程.结果表明:牙哈、哈得原油样品具有很高的总气产率,C1-5产率分别达738.87mL/g,598.98mL/g;随热解温度升高,牙哈、哈得原油样品热解生成的甲烷和沥青产率不断增加,C2-5和C6-14产率先增加后减少,C14+产率不断降低,δ13C1值先变轻后变重,δ13 C2,δ13 C3值逐渐变重;原油裂解生气过程划分为两个阶段,第1阶段以液态烃裂解成湿气为主,第2阶段为C2-5烃气裂解成甲烷和沥青.分析不同原油样品裂解生烃特征与生气过程,有助于研究原油裂解生烃机理.

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.