压力对塔里木原油四组分热解性能的影响

压力对深层油藏原油热化学过程的影响尚存在较大争议,为研究其在油藏原油热解成气过程中的作用机理,我们在450℃、5~40 MPa压力下对塔里木原油四组分(饱和分、芳香分、胶质和沥青质)进行了封闭体系的热解实验,通过气相色谱(GC)和气相色谱/质谱(GC/MS)分别对原油四组分热解反应的气体产物及饱和分热解过程的液态产物进行了分析。结果表明,在450℃、24 h及不同压力下,沥青质热解产气率高于胶质、芳香分和饱和分;四组分的气相热解产物中,C1的产率明显高于C2~C5组分。增大压力抑制沥青质、胶质及芳香分的热解产气过程而促进饱和分的热解产气过程。随压力的增大,饱和分热解的液态产物的主峰组分碳数先减小,再增大。压力低于20 MPa时,饱和分热解过程中以裂解反应为主;高于30 MPa时,增大压力有利于缩合反应。研究结果可为认识深层油藏原油的稳定程度及天然气的成因提供一定的理论参考。

Effect of Pressure on Pyrolysis Characteristics of Four-Components of Tarim Crude Oil

There are debates on the influence of pressures on chemical processes of crude oil in reservoirs. To investigate the effect of pressure on the pyrolysis of crude oil into gas in the reservoir, the compositions and contents of the gas products produced by pyrolysis reactions of four components separated from the Tarim crude oil and that of liquid products from saturates of Tarim crude oil under 450 ℃ and 5~40 MPa were analyzed by gas chromatography(GC) and GC mass spectrometry GC/MS, respectively. The results show that more gas is obtained in pyrolysis of asphaltene than resins, aromatics and saturates. The amount of C₁ in hydrocarbon gases generated by pyrolysis of the four-components is significantly higher than that of C₂~C₅ components. Increasing pressure decreases the yield of hydrocarbon gas generation in the pyrolysis process of asphaltene, resin and aromatics, but promotes the production of hydrocarbon gas in saturates pyrolysis. The liquid pyrolysis products transform to hydrocarbon compounds of low carbon numbers then to high carbon numbers with the pressure increase. The pyrolysis process is dominated by thermal cracking of the components in saturates under pressures less than 20 MPa. The study provides the theoretical reference for the crude oil stability and the natural gas formation in deep reservoirs.