原油沥青质沉积影响因素

Influencing Factors of Asphaltene Deposition in Crude Oil

针对西北某油田沥青质井筒沉积问题,选取四种黏度相差较大的原油,采用黏度法和微观形态观察研究原油中沥青质的析出过程。结合原油的物化性质及各项参数,分析沥青质沉积的主要影响因素。实验结果表明,沥青质沉积不是仅仅出现在沥青质含量较高的稠油中,稀油也可能产生较严重的沥青质沉积现象。沥青质含量、原油黏度、杂原子含量不是沥青质沉积的主导因素。不稳定系数、氢碳原子比、胶质/沥青质比值是影响沥青质沉积的主要内在因素。温度降低,会加剧沥青质沉积现象。π—π键和氢键是沥青质分子形成缔合物的主要作用力。高碳数化合物含量较高会导致较高的黏度,可以在一定程度上阻止沥青质聚集体的进一步聚集,降低沉积速率;原油黏度较低,当胶体处于不稳定状态时,沥青质聚集体通过扩散作用更容易碰撞、聚集及沉积。油样中加入十二烷基苯磺酸、水杨酸促使沥青质聚集体大量聚并、沉积。加入0.5%YZB-7酚醛低聚物可以明显抑制沥青质沉积,抑制率可达81%。

In order to solve the problem of asphaltene wellbore deposition in an oilfield in Northwest China,four kinds of crude oils with different viscosities were selected.The precipitation process of asphaltene in crude oil was studied by viscosity method and microscopic morphology observation.Combined with the physicochemical properties and parameters of crude oil,the main factors affecting the precipitation of asphaltene were analyzed.The experimental results show that asphaltene deposition is not only in heavy oil with high asphaltene content,but also in light oil.High viscosity of crude oil and high content of asphaltene are not the direct causes of asphaltene deposition.Asphaltene content,crude oil viscosity and heteroatom content are not the main factors of asphaltene deposition.Coefficient of instability,atomic ratio of hydrogen to carbon and the ratio of resin to asphaltene are the main factors affecting the initial precipitation point of asphaltene.The decrease of temperature would aggravate the asphaltene deposition.Andπ—πbond and hydrogen bond are the main forces for the formation of association compounds of asphaltene molecules.Crude oil with high viscosity can prevent the further accumulation of asphaltene aggregates and reduce the deposition rate.For crude oil with low viscosity,asphaltene aggregates are more likely to collide,accumulate and deposit through diffusion.The addition of Dodecylbenzene sulfonic acid and salicylic acid in the oil sample promotes the aggregation and deposition of asphaltene aggregates.Adding 0.5%YZB-7 phenolic oligomer could obviously inhibit asphaltene deposition,and the inhibition rate can reach 81%.