基于分子动力学模拟的重油稳定预测研究

Research on prediction of heavy oil stability based on molecular dynamics simulation

针对现有重油稳定性预测指数存在的精确性不足以及高相对分子质量物质的极性溶解度参数难以获得的问题,使用分子动力学模拟方法计算12组比例的径向分布函数,并结合S_(SARA)函数提出新的重油稳定性预测指数计算方法。由径向分布函数图像峰值与原点构成的正比例函数的斜率倒数表征重油稳定性大小,计算出S_(SARA)函数中a、b、c常数数值,得到a、b、c数值分别为0.4487、0.0093、-0.5012。设置6组检验数据进行径向分布函数、CⅡ指数以及S_(SARA)值计算。结合径向分布函数图像以及CⅡ指数数值,对比新S_(SARA)指数发现新S_(SARA)指数预测结果与径向分布函数计算结果以及CⅡ指数数值表征的重油稳定性大小趋势一致,证明此式在进行重油稳定性预测理论上可行。

In view of the insufficient accuracy of the existing heavy oil stability prediction index and the difficulty of obtaining the polar solubility parameters of high molecular weight substances,molecular dynamics simulation methods were used to calculate the radial distribution function of twelve sets of proportions.A new calculation method of heavy oil stability prediction index was proposed by combining with S_(SARA) function.The reciprocal slope of a direct proportional function composed of the peak of the radial distribution function image and the origin reflected the stability of the oil product.The constant a,b and c in the S_(SARA) function were calculated,and the values of a,b and c are 0.4487,0.0093 and-0.5012,respectively.Six sets of test data were set up for radial distribution function,index and the S_(SARA) value calculation.Combined with radial distribution function images and CⅡindex values and compared with the new S_(SARA) index values,it is found that the prediction result of the new S_(SARA) index is consistent with the calculation result of the radial distribution function and the trend of the stability of heavy oil represented by the value of the CⅡindex.It proves that this formula is theoretically feasible in predicting the stability of heavy oil.