超稠油低温氧化和裂解成焦实验

针对辽河油田锦91区块超稠油火驱过程所形成的氧化炭和裂解炭的基本性质和火驱燃烧特征认识不清的问题,利用高温高压反应釜装置开展超稠油低温氧化和裂解实验,并采用气相色谱仪、场发射扫描电镜、能量色散X-射线光谱仪和热重分析仪分析产出气组成、焦炭的微观形貌、元素含量和热重损失,并运用等转化率法(Friedman和OFW)求解焦炭燃烧活化能。结果表明:经历250 ℃低温氧化后,超稠油部分转化为氧化炭;经历400 ℃裂解后,超稠油转化为裂解炭和改质油。氧化炭中氧和硫元素的相对含量明显高于裂解炭。氧化炭表面呈粒度大小不一的焦炭微粒相互融并的微观形貌,且随着温度升高,氧化炭的多孔结构愈发明显;裂解炭呈不规则的块状微观形貌,且随着温度升高,裂解炭表面出现很多凸起状颗粒。氧化炭的生成有助于建立燃烧前缘;裂解炭的燃烧活化能更低,有助于维持燃烧前缘稳定推进。该研究对超稠油火驱开发具有一定的理论指导意义。

Experiments on Low-temperature Oxidation,Pyrolysis and Coking of Super-heavy Oil

Abstract: In response to the problem that the basic properties of oxidized carbon and pyrolysis carbon generated in the in situ combustion of super heavy oil in Block Jin 91, Liaohe Oilfield and the in-situ combustion characteristics were not well understood, experiments on low temperature oxidation and pyrolysis of super heavy oil were conducted with reaction still, the composition of produced gas and the micro morphology, element content and thermogravimetric loss of coke were analyzed by gas chromatograph, field emission scanning electron microscope, energy dispersive X-ray spectrometer and thermogravimetric analyzer, and the activation energy of coke combustion was solved by iso-conversional methods (Friedman and OFW). The results showed that, after low temperature oxidation at250 ℃, the super heavy oil was partially converted into oxidized carbon; after pyrolysis at 400 ℃, the super heavy oil was converted into pyrolysis carbon and modified oil. The relative contents of oxygen and sulfur elements in oxidized carbon were significantly higher than those in pyrolysis carbon. The surface of oxidized carbon was characterized by the inter-melted of coke particles with different particle sizes, and the porous structure of oxidized carbon became more obvious with the increase of temperature. The surface pyrolysis carbon became irregular micro blocks, and many raised particles appeared on the pyrolysis carbon surface with the increase of temperature. The formation of oxidized carbon was helpful to establish combustion front; the combustion activation energy of pyrolysis carbon was lower, conducive to maintaining the stable propagation of the combustion front. The study provides a theoretical guidance for the in-situ combustion in super heavy oil development.