注空气开采过程中稠油结焦量影响因素

Influence factors of coking amount during recovery of heavy oil by air injection

通过建立油藏高温、高压反应模拟实验装置,物理模拟了稠油注空气开采过程中焦炭的生成过程,研究了反应气氛、温度、压力以及空气通风强度对稠油生焦量的影响。研究表明:在空气气氛下,原油低温氧化显著促进了焦炭生成,5 MPa反应压力下,每克稠油最高焦炭生成量为0.375g,是氮气气氛下最高生焦量的2.5倍,焦炭初始生成温度受低温氧化影响比氮气条件降低了近200℃。随压力升高,加剧的低温氧化反应提高了焦炭生成量,但是5 MPa后压力影响不再显著。随空气通风强度增加,生焦量并非持续增加,而是在33.4 N·m3/(m2·h)附近存在极值。进一步对比分析了焦炭的高温氧化消耗与原油组分蒸馏失重对焦炭生成量的影响。其结果表明,焦炭氧化是空气气氛下温度自225℃升高至300℃过程中焦炭净生成量减少的主要原因。在氮气气氛下,随温度升高至450℃,加剧的原油热解缩聚反应增加了生焦量,但温度进一步升高引起焦炭自身热解失重,生焦量降低。另外,实验还发现,当温度超过200℃时,反应管内油砂中心温度超过外壁面加热控制温度。分析表明,超温现象由原油组分的低温氧化和部分活性较强的焦炭高温氧化引起,因此该稠油存在油层自燃点火的应用潜力。

Through building the experimental apparatus for reservoir HTHP reaction simulation and physically simulating the coke generation process during recovery of heavy oil by air injection,a study was conducted on the influences of reaction atmosphere,temperature,pressure and air ventilation intensity on the coking amount with certain Xinjiang heavy oil.The research indicated that in the air atmosphere,the low temperature oxidization（LTO）of crude oil can significantly promoted coke generation.with the reaction pressure 5MPa,each gram of heavy oil can generate the maximum coking amount of 0.375 g,2.5 times over that in N2 atmosphere.Influenced by LTO,the initial coke generation temperature is lower than that in N2 atmosphere by nearly200℃.With the pressure rising,the aggravated LTO can increase the coking amount;when the pressure exceeds 5 MPa,its effect is not significant.With the increase of air ventilation intensity,the coking amount is not continuously increased,and a peak will appear at around 33.4 N·m3/（m2·h）.A comparative analysis was carried out on the influences of coke high-temperature oxidization consumption as well as crude-oil component distillation and weightloss on coking amount.The results indicated that coke oxidization was the major cause of the reduction in net coking amount with the temperature ranging from225℃to 300℃in air atmosphere.When the temperature reaches 450℃in N2 atmosphere,the aggregated crude-oil pyrolysis condensation reaction can increase the coking amount,but the further rising of temperature will lead to coke pyrolysis and weightloss,resulting in a decline in coking amount.Additionally,the experiments revealed that when the temperature exceeds 200℃,the oil sand center temperature in the reaction tube was higher than the outer-wall heating control temperature.The analysis results showed that the temperature exceeding phenomenon was caused by the LTO of crude oil component and the high temperature oxidation of certain coke with high activity;This heavy oil has the spontaneous ignition potential.