A new insight into the modeling of Asphaltene precipitation in crude oils using pc-SAFT

Abstract

Asphaltene precipitation occurs when the pressure of a crude oil system falls below the asphaltene onset pressure (AOP) which may lead to subsequent deposition and plugging of the production tubing. The AOP curve is usually obtained experimentally and serves as an input to Equation of State (EoS) models. In this work, we highlight the importance of defining asphaltene precipitation by both the AOP curve and the amount of asphaltene precipitated. This is because experiments performed on wellhead samples are most likely missing the heaviest asphaltene fractions that have already deposited in the wellbore. Although the absence of this fraction can significantly shift the AOP curve, it will not have a notable effect on the amount precipitated since it only accounts for a small fraction of the total precipitated asphaltenes. Additionally, using the AOP curve along with the amount of asphaltene precipitated, we have shown that modeling asphaltenes as a monodisperse fraction gives a lower onset pressure and magnifies the amount of asphaltene precipitated as compared to the actual polydisperse case. Providing a more accurate prediction gives a better understanding of the system. This allows the use of general strategies, such as simple pressure and temperature control to prevent asphaltene deposition problem.

AAPG Datapages/Search and Discovery Article #90329©2018 AAPG/SEG/EAGE/SPE Middle East Region RDPETRO, Abu Dhabi, UAE, May 9-10, 2018