Fractal analysis of asphaltene aggregation phenomena in live oils at elevated pressure and temperature
Fractal analysis of asphaltene aggregation phenomena in live oils at elevated pressure and temperature
复制标题
DOI：
10.1080/02726351.2016.1158218
复制
发表时间：
2020-05
影响因子：
2.5
通讯作者：
S. Mohammadi;F. Rashidi;S. A. Mousavi-Dehghani;M. Ghazanfari
中科院分区：
文献类型：
--
作者：
S. Mohammadi;F. Rashidi;S. A. Mousavi-Dehghani;M. Ghazanfari
摘要 在这项工作中，采用高压显微镜技术测量了在高压和高温下不同现场油样中形成的沥青质聚集体的尺寸和分形维数。研究发现，现场油样中的沥青质聚集体是不规则的分形结构，其分形维数依赖于压力-温度。通过监测沥青质聚集体的分形维数和尺寸随压力和温度的变化，可以很好地预测在升高的压力和温度下沥青质聚集过程的机制。新鲜油中沥青质聚集体的分形维数范围与在经典胶体系统中观察到的相似。在轻质油样品中，最低温度（319 K）的减压过程导致形成大而松散的聚集体，即分形维数在1.63至1.72范围内的低分形维数的多孔聚集体。随着温度的升高，形成更致密、更致密的结构，最高温度为408 K时，分形维数在1.90~2.01的窄范围内变化。稠油样品中，分形维数在不同温度下变化范围较大（368 K时为1.56~1.90，333 K时为1.68~1.89）。从实践的角度来看，本研究提供了关于压力、温度和石油类型对形状/结构的重要性的定性和定量信息，从而提供了油藏压力和温度条件下新鲜油中沥青质聚集体的密度/致密性。
Abstract In this work, high-pressure microscopy technique was used to measure the size and fractal dimension of asphaltene aggregates formed in different live oil samples at elevated pressures and temperatures. It was found that the asphaltene aggregates in live oil samples are irregular fractal-like structures with pressure−temperature-dependent fractal dimensions. By monitoring the variation of the fractal dimension and size of the asphaltene aggregates with pressure and temperature, the mechanisms responsible for asphaltene aggregation process at elevated pressures and temperatures can be well predicted. The range of fractal dimension of asphaltene aggregates in live oils is similar to that observed in classical colloidal systems. In light oil sample, depressurization process at lowest temperature (319 K) leads to the formation of large and loose aggregates, that is, porous aggregates with low fractal dimensions in the range from 1.63 to 1.72. With temperature rise, denser and more compact structures are formed with fractal dimensions varied in a narrow range of 1.90–2.01 at highest temperature of 408 K. In heavy oil sample, the fractal dimensions change in a wide range at different temperatures (1.56–1.90 at 368 K, and 1.68–1.89 at 333 K). From a practical viewpoint, the present study provides qualitative and quantitative information on the significance of pressure, temperature, and oil type on the shape/structure, and consequently density/compactness of asphaltene aggregates in live oils at pressure and temperature conditions of oil reservoirs.