Page 273 - Formation Damage during Improved Oil Recovery Fundamentals and Applications

244 Rouzbeh G. Moghanloo et al.

6.1 INTRODUCTION, DEFINITION, EXISTENCE STATE OF
ASPHALTENE IN CRUDE OIL, MOLECULAR STRUCTURE
OF ASPHALTENE, MONITORING, AND REMEDIATION

6.1.1 Introduction
The issue of asphaltene deposition has plagued the oil and gas industry
for decades since J.B. Boussinggault first identified the problem in 1837
and referred to this group of compounds as “asphaltenes” (Creek, 2005).
It is therefore extremely important to understand the issue of asphaltene
deposition and the factors affecting it, due to the huge costs associated
with remediation (Gonzales et al., 2016). Crude oil has several fractions,
and asphaltenes essentially tend to be its heaviest, polarizable fractions.
They are known as the “cholesterol of petroleum” (Boek et al., 2010)
due to their ability to precipitate as solids and subsequently deposit with
changing pressure, temperature, and oil composition. This may affect
both surface properties and crude oil rheology. In both upstream and
downstream operations asphaltene deposition may cause severe problems.
Asphaltenes precipitate and deposit on the pipeline surfaces, the bottom
of distillation columns and heat exchangers as well, affecting efficiency
and creating added economic costs to remediate (Davudov et al., 2017).
Deposition can lead to fouling and/or damage during oil production or
refining. During crude oil production, they can deposit in reservoir rock
pores, thus leading to possible blocking of flow, particularly in the near
well bore region. The asphaltene problem is the most challenging one in
petroleum production, processing and transportation facilities. Asphaltene
precipitation refers to the process when asphaltenes become a separate
phase from the crude oil. They remain suspended in the liquid phase
where the quantity and the size of the asphaltenes are relatively small.
The precipitated asphaltenes clump together (aggregation) and form larger
particles, also called flocs. The asphaltene aggregates are initially sus-
pended in the crude oil. Subsequently, the flocs may attach to and accu-
mulate on various surfaces, a process referred to as asphaltene deposition.
(Seifried, 2016; Yuan et al., 2016).
Nonetheless, the properties of asphaltenes still remain to be properly
understood. In the literature review section, a discussion of asphaltenes
is provided, detailing its definition, it’s existence state in crude oil,
molecular structure, and composition. Issues and remediations are
also addressed together with its formation in respect of its precipitation,
aggregation, and deposition. Current models are described and some