原油厌氧微生物降解特征分析

为了研究原油厌氧微生物降解形成的原油组分和伴生气特征,在亨盖特厌氧微生物操作平台上,利用厌氧降解菌群对胜利油田两种稀油进行模拟降解研究。结果表明:稀油经过微生物厌氧降解具有稠化的趋势,伴随降解产生CH_4和少量CO_2,降解248 d每克原油能够产3.0 mmol CH_4,补充矿物质营养后每克原油(滨76)产CH_4达到6.4 mmol。不同原油降解产生的气体碳同位素存在显著差异,义141原油所产气体CH_4中13C同位素比值偏差(δ(13C))分布为-4.636%^-4.527%,CO_2的δ(13C)分布为0.424%~0.850%;而滨76原油降解所产气体CH_4的δ(13C)分布为-4.983%^-4.853%,CO_2的δ(13C)分布为0.254%~0.465%,碳同位素相对值差异性是由原油自身碳同位素组成差异性所导致。两种原油的饱和烃组分均被显著降解,最高由初始的72.77%下降到44.0%,但两种原油的胆甾烷等生物标志物在降解前后无显著变化,表明原油仍处于轻度生物降解阶段。室内模拟研究揭示的原油厌氧微生物降解过程的油气特征可为生物成因的稠油及伴生气的勘探开发提供重要理论指导。

Causes Leading to Formation of Shot Cokes and Measures for Its Prevention in Super Viscous Oil Delayed Coking Unit

Shot cokes are frequently formed in the delayed coking unit treating the super viscous oil at PetroChina＇s Liaohe Petrochemical Company. Considerable work has been carded out to avoid the formation of shot cokes. The test results obtained have shown that the property of super viscous oil has played a key role in the formation of shot cokes. After adjusting and optimizing the process indices the operating regime of the delayed coking unit at a throughput of 118t/h of the super viscous oil is specified as follows： a reaction temperature of 498-502℃, a reaction pressure of 0.17-0.25 MPa, a recycle ratio of 0.5-0.6 and a fractionation tower bottom temperature of 355-365 ℃. In the meantime, the delayed coking process has adopted measures to enhance pre-fractionation of the feedstock to rationally remove light fractions and maintain a steady gas velocity in order to avoid the formation of shot cokes.