Direct Visualization of Ultrasonication Induced Asphaltenes Removal in Carbonate Rock Using Confocal Imaging

Abstract

Asphaltenes deposition is a major issue in the petroleum industry as it can have a detrimental impact on hydrocarbon recovery efficiency. Therefore, it is imperative to study the fundamental mechanisms controlling the asphaltenes flocculation and deposition in reservoirs allowing us to prevent and possibly eliminate such problem. Hitherto many studies have highlighted ultrasonication as a potential remediation technique but no investigation has been able to provide direct visual evidence of the phenomena. The primary objective of this study is to visualize the deposition of asphaltenes and their subsequent removal by ultrasonication in Indiana Limestone using state of the art confocal microscopy. To do so, we performed a comprehensive series of experiments by flooding Indiana Limestone core samples with crude oil and later passing ultrasonic waves through the flooded sample. Four core samples of Indiana Limestone each displaying different permeability were used, these are referred to as A2, B2, C4, and D4. At each stage of experiment series of images were captured by confocal microscopy depicting asphaltenes deposition and it’s post-sonication distribution. The images were further segmented allowing us to compute changes in the asphaltenes content before and after sonication. The comparison of confocal scans reveals that the ultrasonic irradiation is highly efficient in removing asphaltenes from the low permeability core samples, whereas in the case of highly permeable cores, rather than preventing it promoted the asphaltenes flocculation. Surprisingly, an increase in asphaltenes content was observed after ultrasonication in high permeability core samples.