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为探讨原油裂解成气过程中正构烷烃、甾烷和萜烷等生物标志物地球化学的演化规律及压力的影响,对东营凹陷古近系的低熟原油样品在高压釜中进行了原油裂解成气模拟实验,实验设计了2种不同的实验压力条件下(常压开放体系和20 MPa压力封闭体系),以升温速率30℃/h升温到650℃.从300℃开始,每隔50℃对实验产物进行特征检测,加压实验通过注水加压实现.样品来源于中国东部东营凹陷古近系的低熟原油.实验结果显示,常压和20MPa下,原油在达到450℃后进入原油裂解成气阶段.在原油裂解成气之前的一定温度范围内,原油已经开始不同层次地裂解,包括高分子正构烷烃向低分子正构烷烃的演变.原油裂解成气过程存在重烃气二次裂解生成甲烷气的过程,主要发生在550~650℃,表现为Ln(C1/C2),Ln(C1/C3)和干燥系数显示升高的特征.压力(20 MPa)对原油裂解总体是一个抑制的过程:相对常压开放性体系,20 MPa下原油转化率降低,原油主裂解成气门限温度升高和原油裂解主成气温阶时间延迟,高温下较高碳数的正构烷烃或其他化合物得到保留,∑C21/∑C22+,Ln(C1/C2),Ln(C1/C3)和Ln(C2/iC4)和干燥系数等参数值在主原油裂解成气温阶内降低,Ph/nC18,Pr/nC17在二次裂解阶段(550~600℃)下降.压力不同程度地影响了Ts,Tm,C31升藿烷和C29甾烷等生物标志物及其成熟度参数在原油裂解高温阶段的演化,并且在不同的温阶这种影响表现出差异性.
In order to investigate the geochemical evolution and pressure of biomarkers such as n-alkanes, steranes and terpanes in the process of crude oil cracking into gas, crude oil was cracked in autoclave samples Gas simulation experiments were designed experimentally under two different experimental conditions (atmospheric pressure open system and 20 MPa pressure closed system), with a heating rate of 30 ° C / h heating to 650 ° C starting from 300 ° C, every 50 ° C The results of the experiment were verified by water pressure.The samples were from low-mature crude oil of Paleogene in Dongying Sag, eastern China.The results showed that crude oil cracking into crude oil at 450 ℃ after atmospheric pressure and 20MPa Gas phase. Crude oil has begun to crack at different levels, including the conversion of high molecular weight n-alkanes to low molecular weight n-alkanes, within a certain temperature range prior to the cracking of crude oil into gas. The process of generating methane gas mainly occurs at 550-650 ℃, which shows the characteristics of Ln (C1 / C2), Ln (C1 / C3) and drying coefficient show an increase.The pressure (20 MPa) the process of: For the atmospheric open system, the conversion of crude oil at 20 MPa is reduced, the main cracked crude oil is increased to the gas-limit temperature and the main crack temperature of the crude oil is delayed. The higher carbon number n-alkanes or other compounds are retained at high temperature, The parameter values of ΣC21 / ΣC22 +, Ln (C1 / C2), Ln (C1 / C3) and Ln (C2 / iC4) and the drying coefficient decrease when the main crude oil is pyrolyzed into gas temperature. Ph / nC18 and Pr / (550-600 ℃) decreased.The pressure affected the biomarkers such as Ts, Tm, C31, hopane and C29 sterane to varying degrees and their maturity parameters evolved in the high temperature phase of crude oil cracking, The effect of temperature is different.