Evaluation of Asphaltene Stability of a Wide Range of Mexican Crude Oils

Abstract

Appropriate prediction of asphaltene stability can anticipate operational problems such as plugging of lines and process equipment (pumps, heat exchangers, separation tanks, among others), thus assuring the production, processing, transportation, and storage of petroleum. In the present study, the physical and chemical properties of a series of Mexican crude oils with American Petroleum Institute (API) gravity ranging from 10 to 52 were determined. Based on saturate, aromatic, resin and asphaltene (SARA) analysis, the following indexes were calculated: colloidal instability index, colloidal stability index, Stankiewicz stability criterion, stability cross plot, and oil compatibility model. The stability of crude oils was also evaluated by means of experimental techniques such as spot test, S-value, and static stability test column. No uniform results were obtained when determining the stability of crude oils with different methodologies. Due to the discrepancies disclosed, it is recommended to evaluate stability by various methodologies to adequately predict the stability of asphaltenes in crude oils. Hence, the stability of asphaltenes in a given crude oil may be ascribed based on the average result. However, from a practical point of view, pertinent cautions on the handling of samples must be observed if at least one of the methods classifies the sample as unstable or metastable.

Compatibility of Crude Oil Blends─Processing Issues Related to Asphaltene Precipitation, Methods of Instability Prediction─A Review

“…Both Comparisons reveal that CII is better suited for indicating crude oil incompatibility. Also a Mexican region crude comparison revealed that CII and CSI, has much better accuracy of prediction . The methods based on the comparison of several parameters, such as QAA and SCP, show the greatest number of correct predictions.…”

“…Also a Mexican region crude comparison revealed that CII and CSI, has much better accuracy of prediction. 70 The methods based on the comparison of several parameters, such as QAA and SCP, show the greatest number of correct predictions. Predictive methods based on the SARA analysis are characterized by simplicity, but as experience shows, each of them individually does not guarantee satisfactory results of compatibility prediction.…”

“…71 The approach suggested in the literature is to analyze all parameters simultaneously to obtain the dominant result. 13,18,20,70 The QQA, SCP, or K model based on this approach gives better results, which are still subject to uncertainty and must be further correlated with the behavior of the tested raw material to select the models that best fit the actual conditions of processing. 18 Experimental methods present a wide spectrum of complexity, from a simple spot test, through a heptane dilution test or TE, to those requiring specialized equipment: S-value, P-value, or Turbiscan.…”

Review of Asphaltenes in an Electric Field

“…It is believed that resins have the greatest impact on the stability of asphaltene molecules in crude oil as they contribute to smaller aggregate formation and thereby prevent separation of the asphaltene molecules. ,, Resins are also polar components of crude oil and are soluble in pentane and heptane but insoluble in propane. Structurally, resins are akin to asphaltenes, but they have a higher H/C ratio (1.2–1.7), lower aromaticity, and lower molecular weight compared to asphaltenes. ,, Relatively longer aliphatic side chains and smaller chromophores contribute to higher solubility of resins in aliphatic solvents .…”

Review on Application of Nanotechnology for Asphaltene Adsorption, Crude Oil Demulsification, and Produced Water Treatment

“…Resins are also another type of polar crude oil component having a profound influence on the stability behavior of asphaltenes in crude oils as they can prevent the separation of the asphaltene molecules. In terms of structure, resins are very similar to asphaltenes; however, they have a lower molecular weight (MW) (<1000 g/mol) and higher hydrogen/carbon (H/C) ratio (1.2–1.7). , Moreover, as compared to asphaltenes, resins have smaller chromophores and relatively longer aliphatic side chains, which increase their solubility in aliphatic solvents . The molecular interaction between asphaltenes and resins and their ratio with respect to other components in crude oils are vital for the stabilization of crude oil emulsions.…”