1. business and industrial
2. energy
3. oil

04.2010
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UDC 52.47.23
Remediation of Asphaltene and other Heavy
Organic Deposits in Oil Wells and in Pipelines
Reservoir and petroleum engineering
G.Ali Mansoori
(University of Illinois)
In this report the methodologies and analysis for in situ remediation of heavy organics in petroleum
production, transportation and processing industries is presented. First the heavy organics which deposit
from petroleum fluids are indentified and it is pointed out that the more difficult member of these
compounds to deal with are asphaltenes. Six different in situ remediation methods are introduced which
include: (i) production scheme alteration techniques; (ii) chemical treatment techniques; (iii) external force
filed techniques; (iv) mechanical treatment techniques; (v) thermal treatment techniques; (vi) biological
methods. Also eight steps that appear to be necessary and effective in prevention and moderating the
severity of the deposition and remediation are introduced which include: (a) Predictive modeling and
analysis; (b) dual completion of oil wells; (c) compatibility tests of injection fluids before applications; (d)
consideration of the compositional gradient of heavy organics in reservoir in production scheme design;
(e) application of mechanical removal technologies for deposits; (f) application of solvent for dissolution
of deposits; (g) hot oil treatment of the in situ deposits; and (h) use of dispersant to stabilize the heavy
organics, specially asphaltenes from deposition. Overall, a proper route to combat arterial blockage in the
oil and gas industry is to consider a combination of prediction modeling, experimentation and remediation.
Keywords: asphaltene, organic deposits, oil treatment, steric colloid
Adress: [email protected]
INTRODUCTION
Arterial blockage in the petroleum industry is mostly
due to the deposition of heavy organic molecules from
petroleum fluids. Heavy organic molecules such as
asphaltenes, asphaltogenic acids, diamondoids and
derivatives, mercaptans, organometallics, paraffin /wax
and resins exist in crude oils (fig.1) in various quantities
and forms [1, 2].
Such compounds could separate out of the crude oil
solution due to various mechanisms and deposit, causing
fouling in the oil reservoir, in the well, in the pipelines
and in the oil production and processing facilities [1-6].
Solid particles suspended in the crude oil may stick to the
walls of the conduits and reservoirs (fig.2). The toughness
of the deposits has a lot to do whether there is asphaltene
present in the crude oil even in minute quantities.
Asphaltene, which is a highly polar compound, generally
act as a glue and mortar in hardening the deposits and, as
a result, causing barrier to the flow of oil [7-14].
Depositions of the heavy organics present in crude
oil happen due to various causes depending on their
molecular nature. Mercaptans and organometallics
depositions are due to dissociation, solubility effects, or
attachment to surfaces. Diamondoids and paraffin/wax
deposit and form solid crystals due, mostly, to lowering
of temperature [15-17]. Resins are not known to deposit
on their own, but they deposit together with asphaltenes
[18]. The reasons for the asphaltenes and asphaltogenic
acids deposition can be many factors including variations
of temperature, pressure, pH, composition, flow regime,
wall effect and electrokinetic phenomena. When several
different heavy organic compounds are present in a
Fig.1. Heavy organic molecules that deposit
from petroleum fluids
Fig.2. Asphaltene molecules are highly sticky and
they act as mortar which also cause other suspended
particles stick to deposit cause fouling in petroleum
fluid arteries
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Fig.3. The role of coagulants and flocculants in
deposition of a suspended particles
model for the prefouling behavior of suspended particles
corresponding to petroleum fluids production conditions
[5, 6]. We predicted the rate of particle deposition during
various turbulent flow regimes. The turbulent boundary
layer theory and the concepts of mass transfer were
utilized to model and calculate the particle deposition
rates on the walls of flowing conduits. The proposed
model accounted for the eddy and Brownian diffusivities
as well as for inertial effects. The analysis presented
showed that rates of particle deposition during petroleum
production on the walls of the flowing channel due solely
to diffusion effects are negligible. It was also shown that
deposition rates decrease with increasing particle size.
However, when the process is momentum controlled
(large particle sizes) higher deposition rates are expected.
Considering that the major barrier in a profitable
deposition-free oil production scheme is the presence of
asphaltenes in the crude the in situ remediation methods
of asphaltenes in the petroleum fluids is discussed in the
following sections.
In Situ Field Remediation Methods
In petroleum production initially it is necessary to
take any number of steps necessary to prevent the
fouling problems. Heavy organics deposition could be
eliminated by modification of the production practices,
rather than by chemical, mechanical, thermal or other
external means. This may reduce the cost of production
operation appreciably. This may be achieved by the
optimum design of the oil production and transportation
systems based on proper laboratory tests and implication
of deposition prediction models [22-25].
Heavy organic deposits re- sulting from the presence
of asphaltenes in crude oils are quite hard to deal with.
Asphaltenes may be destabilized in any area of the oil
production and processing facilities from as far back as
the near wellbore area to as far down the system as in the
petroleum refinery (fig.4,5).
Asphaltenes, in addition to their highly sticky
characteristics which attach to solid surfaces, change
their wettability [26], they could also act as nucleation
sites for paraffin/wax and diamondoids crystallization
which are often found within the same deposits.
Heavy organics deposition due to asphaltene
flocculation could be controlled through the better
knowledge of the mechanisms that cause their deposition
in the first place [9, 27]. Processes can be altered to
minimize the deposition and chemicals can be used
Reservoir and petroleum engineering
petroleum fluid their interactive effects must be also
considered in order to understand the mechanisms of
their collective deposition or lack of it. This is especially
important when one of the interacting heavy organic
compounds is asphaltene. For example a regular waxy
crude containing minute amounts of asphaltene will
behave differently at low temperatures (below the cloud
point) compared with: (i) a clean waxy crude with no
other heavy organics present in it; (ii) an asphaltenic
crude containing some paraffin/wax or; (iii) a purely
asphaltenic crude containing no paraffin/wax [19, 16].
Deposition of heavy organics in petroleum fluids
may cause formation of suspended particles. In general,
suspended particles in a crude oil fall into two classes:
«basic sediment» and «filterable solids». Presence of
suspended particles in petroleum fluids could have a
severe economic impact on petroleum industry [5, 6].
Carried along in the oil, they may cause fouling, foaming,
erosion, and/or corrosion. Depending on the case,
coagulants (molecular weight < 10000) or flocculants
(molecular weight > 10000), may provide an indirect aid
in suspended particles removal (fig.3).
Coagulants are molecules with strong polar charge
which act to disrupt charges on the surface of droplets
of an opposite phase or suspended solid particles that
would otherwise prevent it from coalescence. Flocculents,
act to coalesce colloidal particles, because they attach to
colloids and they increase their size beyond the Brownian
law of suspension [20, 21].
The production and transportation of petroleum fluids
will be severely affected by deposition of suspended
particles (i.e. asphaltenes, diamondoids, paraffin/wax,
sand, etc.) in production wells and/or transfer pipelines xx
some of my older papers. In certain instances the amount
of precipitation is rather high causing complete fouling of
these conduits. Therefore, it is important to understand
the behavior of suspended particles during petroleum
flow conditions. We recently introduced an analytical
04.2010
Fig.4. Locations (circled in green) where heavy organics deposition could occur most likely in the petroleum fluids
production and transportation systems
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Reservoir and petroleum engineering
04.2010
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Fig.5. Locations where heavy organics deposition could most likely occur
in the petroleum refining/processing systems [14]
[28] to possibly control the deposition when process
alterations are not effective. Heavy organics depositions
and their remediation in petroleum fluid systems may
be controlled using various techniques which include
the following six categories: production scheme
alterations, chemical treatment methods, external force
fields exertion, mechanical treatment methods, thermal
treatment techniques and biological methods [3, 4]. In
what follows we briefly present the various categories of
treatment methods.
I. Production scheme alterations techniques: They
are used to control asphaltene and other heavy organics
deposition and they include: (i) reduction of shear
(fig.6); (ii) elimination of incompatible materials from
asphaltenic crude oil streams (fig.7); (iii) minimization of
pressure-drops in the production facility (fig.8); and, (iv)
minimization of mixing of lean feed stock liquids into
asphaltenic crude streams (fig.7), (v) neutralization of
electrostatic forces (fig.9).
II. Chemical treatment techniques: They include:
Addition of dispersants, antifoulants, coagulants,
flocculants and polar co-solvents which may be used to
control asphaltene deposition in its various stages.
II.1. Dispersants work by surrounding the asphaltene
molecules forming steric colloids, similar to the natural
resin materials (fig.10).
II.2. To inhibit the attachment and growth of deposits
on surfaces and walls they can be coated with antifoulant
chemical compounds (fig.11, 12). Teflon (fig.11) which
Fig.8. Minimization of pressure-drops in the petroleum
production facility causing separation of phases from
a miscible phase to oil, gas and heavy organics phase
Fig.6. Pipe flow with Shear
Fig.7. Incompatible miscible fluids flow and separation
of heavy ends in the form of colloids, flocs and
attachment to the walls of conduits
14
Fig.9. Lack of neutralization of electrostatic forces may
cause break up of asphaltene steric colloids, release
of sticky asphaltene particles and attachment to walls
causing fouling in petroleum fluid flow lines
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04.2010
Fig.13. Flocculation of asphaltene due to increase in
paraffin (nonpolar) content of petroleum [25, 32, 1]
is polytetrafluoroethylene (C2F4)n is one well-known
antifoulant material used for coating surfaces to prevent
organic and inorganic materials from attachment to
surfaces [29].
Organotin compounds particularly tributyltin
oxide (fig.12), are very effective as antifoulants and
have been the antifoulant of choice for many years
in marine, agricultural, wood and plastics industries. The effectiveness of TBTO is a result of the fact that
it gradually leaches from the hull killing the fouling
[31-34]:
Organic material deposited into the production
installations of petroleum crude may cause operational
problems. One may initially try to dissolve such deposits
by various means like steam wash, diesel oil wash and
heavy aromatics wash, etc. One may also consider using
Fig.11. A non-bio antifoulant:
Teflon=polytetrafluoroethylene
organisms in the surrounding area. However, it is found
to cause health and environmental problems [30].
II.3. Coagulants, which are mostly polymers, have
a role similar to resins which form steric colloids and
then flocculation of colloids in the form of flocs and
precipitation (fig.13, 14).
II.4. Polar co-solvents (such as aromatic hydrocarbons)
could re-dissolve the asphaltene deposits and need to
have a high level polarity (aromaticity) to be effective
(fig.15, 16).
When the concentration of polar solvents exceeds
a certain level then asphaltene micelles will be formed
Fig. 12. A bio-antifoulant:
Tributyltin oxide – An organotin Reservoir and petroleum engineering
Fig.10. Steric colloids of asphaltene (asphaltene floc core)
and resins (red aromatic head with black paraffin tails)
Fig.14. Steric-colloid formation of asphaltene flocs
(random aggregates) in the presence of excess amounts
of resins and paraffin hydrocarbons [25, 32, 1]
a system of specifically designed additives to stimulate
the wells. Such additives are best to be a mixture of
an inhibitor of asphaltene precipitation, an asphaltene
dispersant and an antifoaming agent [35].
III. External force field techniques: They include: (i)
electrostatic force field; (ii) electrodynamic force field;
and (iii) magnetic field; (iv) ultrasound techniques;
Fig.15. Aromatic hydrocarbons that could re-dissolve
asphaltene deposits
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04.2010
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Fig.16. Asphaltene miclellization in the presence
of excess amounts of aromatic hydrocarbons [31-33]
Reservoir and petroleum engineering
Fig.17. Pipeline pigs
[www.pipingguide.net/2007/11/pipeline-pigging.html]
(v) microwave techniques. All these techniques are
presently applicable for petroleum/laboratory operations
and mostly for small scales.
IV. Mechanical treatment techniques: They include:
(i) manual stripping, pigging, mechanical vibrations, etc.
Mechanical/manual stripping is probably the oldest
method known for the removal of heavy hydrocarbon
deposits. It is done by mechanically scraping the tubing.
Pigging technology is well established, but it is most
suitable for foams, waxy crude arteries and wax deposit
removal (fig.17).
Pigging technology success for asphaltenic crude
arteries is questionable. Soluble or insoluble pigs are
injected into the oil arteries. The pigs would remove a
portion of the deposit buildup as they travel through
the lines. Although this method may be effective for
cleaning the tubing and lines, it is not effective in
removing the heavy organic deposits at the formation.
There have been some advances in smart pigs which may
take advantage of remote visualization, control, local
heating, etc. Mechanical removal of deposits may be a
cumbersome operation. In addition, the disposal of the
deposits sometimes causes difficulties.
Fig.18. In situ combustion
16
Fig.19. Steam injection [fossil.energy.gov]
V. Thermal treatment techniques: They include: (i) in
situ combustion (fig.18); (ii) steam injection (fig.19); (iii)
hot water injection (fig.20); (iv) hot gas injection (fig.21);
(v) hot chemicals injection; (vi) microwave technique
of heating which is volumetric, sample-based (not the
whole region), and center of sample heated the most
versus the regular heating which heats the surface; (vii)
use of exothermic chemical reactions.
Removal of deposits by hot fluid is performed by
circulating it into the well, conduits, or by injection into
the formation to open up plugged areas. This method
works by melting the organic deposits. Therefore, it is
important to insure that the melted organics are not
re-deposited in another part of the formation. This
happens when the hot fluid introduced to the formation
becomes saturated with melted paraffins, and when the
formation temperature is lower than the cloud point of
Fig.20. Hot water injection [afcee.af.mil]
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Fig.22. Static (PX) heavy organics deposition envelope
(HODE) of a crude oil mixed with a miscible injectant
(MI) at 60 oF but at various proportions and pressures.
In this figure L stands for liquid phase, L-V is the
liquid-vapor two-phase region, L-S is the liquid-solid
two-phase region, and L-V-S is the liquid-vapor-solid
three-phase region
hundred to several hundred thousands. As a result
distribution-function curves are used to report their
molecular weight distribution [42-44]. Some of the
heavy organics present in the oil deposit due to phase
transitions from liquid to solid state. However, this
is not generally the case for asphaltene particles. The
high affinity of asphaltene particles to association with
one another, their tendency to adsorb resins, and their
extensively wide range of size distribution suggest that
asphaltenes are partly dissolved and partly in colloidal
state (in suspension) in oil peptized (or stabilized)
primarily by resin molecules that are adsorbed on
asphaltene surface [38].
Reservoir and petroleum engineering
the hot fluid. Under these circumstances precipitation
will occur and consequently cause permeability reduction
and damage to the formation.
VI. Biological methods: These may include in situ
application of (i) anaerobic bacteria; (ii) aerobic bacteria;
(iii) other microorganisms including fungus, etc. Such
bio-processes that may reduce asphaltenes into lighter
molecules is named biodegradation. Biodegredation
mechanism of asphaltenes is perhaps the least
known reaction mechanism for the biodegradation
of a petroleum fraction. It appears that asphaltenic
compounds are relatively inert to microorganisms
attack, since they consist of complex structures of sheets
of aromatic and alicyclic ring structures with very short
alkyl side chains [36].
Various types of microorganisms that are capable
of oxidizing asphaltenic compounds are widespread
in nature. However, they need to be identified,
isolated and grown in the lab to make them capable of
biodegradation of large amounts of asphaltenic deposits.
Biodegradation, if made practical, is an important
04.2010
Fig.21. In situ hot gas injection [sanleonenergy.com]
mechanism for removing these non-volatile components.
It is a relatively slow process and may require months
to years for microorganisms to degrade a significant
amount of asphaltenes. During such biodegradation, the
proper species of bacteria, fungi, etc. would metabolize
asphaltenes as a source of carbon and energy. Under
aerobic conditions, asphaltene would decompose step
by step into water, carbon dioxide, nitrogen oxides, and
sulfur oxides.
DISCUSSION AND Recommendations
The steps that appear to be necessary and effective
in prevention, moderating the severity of the deposition
and remediation are the following:
(A). PREDICTIVE MODELLING AND ANALYSIS
- Resolution of the heavy organic deposition problem
calls for detailed analyses of heavy organic containing
oils from the microscopic standpoint and development
of molecular models which could describe the behavior
of heavy organics in hydrocarbon mixtures [37-41].
From the available laboratory, field, and refinery
data it is proven that the heavy organics which
exist in petroleum generally consist of very many
particles having molecular weights ranging from a few
Figure 23. Dynamic (QX) heavy organics deposition
envelope (HODE) of a crude oil mixed with a miscible
injectant (MI) at 60 oF but at various proportions and
pressures. In this figure Q=Uavg1.75d0.75/k, where Uavg (m/s)
stands for crude average velocity in a cylindrical
conduit, d (m) is the conduit diameter and k (ohm-1/m)
is the crude electrical conductivity. The area above each
curve represents the deposition region and under the
curve is the flow region with no deposition
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Reservoir and petroleum engineering
Figure 26. Compositional gradient scheme
Fig.24. A well with a dual completion
As a result, a realistic molecular model for the
interaction of asphaltene and oil should take into
account both the solubility in oil of one segment and
suspension characteristic (due to resins) of another
segment of the molecular weight distribution curve of
asphaltene [38, 23, 24, 1, 2].
Initially laboratory work may be necessary to quantify
and characterize the various families of heavy organics
present in a crude and in general shed light on the reasons
for such depositions [45-47]. Laboratory work joined
with statistical mechanical plus kinetics modeling may
result in the construction of heavy organics deposition
envelop (HODE) such as the graph shown in figures 22
and 23 which would indicate the ranges of temperature
and pressure where the crude oil deposits out heavy
organic compounds at various temperatures, pressures,
compositions/blending, electrokinetic effects, and flow
Fig.25. Phase envelops defining the composition
regions of the heavy organics separation at a given
temperature and pressure
18
conditions [41].
(B). Dual Completion - It is reported [48] that the use
of standard well completion techniques when heavy
organics deposition is likely has often resulted in costly
workovers for deposit removal in those wells. To combat
the heavy organics deposit formation the completing
wells with a dual completion is necessary (fig.24).
This is with the purpose of: i) using the inner tubing
strings for solvent or dispersant injection or circulation,
ii) access for lowering production testing devices.
Sometimes an inner tubing string is used for production
to meet production quotas when the main string is shutin for maintenance or heavy organics cleaning.
(C). COMPATIBILITY TESTS - It is suggested
that all well stimulation, injection and enhanced oil
recovery fluids should be tested for static and dynamic
compatibility with the reservoir fluids prior to operations,
Figure 27. Wirelining
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04.2010
Table for shedding light on the problem
The API gravity, resin wt %, asphaltene wt % and asphaltene to resin ratio of by constructing heavy organics
deposition envelopes (HODE) as
various crude oils from around the world [various sources]
shown by figures 22 and 23.
(D). composition gradient - It
is generally understood that there
is a composition gradient of heavy
o
Crude
API
organics in petroleum reservoirs
with deeper zones having higher
fractions of the heavy organics
(fig.26). The decision to produce
Canada, Atabasca
8.3
14.0
15.0
1.07
first the top zone of the reservoir,
which is generally less prone to
Venezuela, Boscan
10.2
29.4
17.2
0.58
heavy organics deposition, is
Canada, Cold Lake
10.2
25.0
13.0
0.52
always preferred. Actually most
Mexico, Panucon
11.7
26.0
12.5
0.48
of the producing wells must be
completed dual commingled.
USA, MS, Baxterville
16.0
8.9
17.2
1.93
Production surveys would show
Russia, Kaluga
16.7
20.0
0.5
0.025
from which zone most of the oil
was being produced.
USA, TX, Hould
19.7
12.0
0.5
0.04
( E ) . M E C H A N I C A L
Brazil, Campos,
19.7
21.55
2.8
0.13
R
E
MOVAL TECHNIQUES
Atabasca
- In certain circumstances
USA, CA,
26.2
19.0
4.0
0.21
mechanical removal techniques,
Huntington Beach
especially wirelining may be
Canada, Alberta
29.0
8.5
5.3
0.62
effective means of combating
the heavy organics problems
India, Mangala crude
29.28
20-30
<0.50
<0.02
[49]. An economical study may
USA, LA, Brookhaven
30.6
4.6
1.65
0.36
indicate whether mechanical
Russia, Balachany
31.7
6.0
0.5
0.08
removal methods of cleaning
is preferred over cleaning by
Russia, Bibi-Eibat
32.1
9.0
0.3
0.03
using solvents. For example
Russia, Dossor
32.6
2.5
0.0
0.00
at the Hassi Messaoud field,
Algeria, necessitated frequent
Russia, Surachany
35.0
4.0
0.0
0.00
tubing scrapings and washings
USA, TX, Mexia
36.0
5.0
1.3
0.26
to maintain production [50, 51].
Cutting the deposits from the
Iraq, Kirkuk
36.1
15.5
1.3
0.08
tubing by wireline method was
Azeri BTC
36.1
0.03
too time-consuming and some
Mexico, Tecoaminocan
36.7
8.8
1.5
0.17
times impractical, so a program of
washing the tubing with a solvent
Mexico, Isthmus
37.8
8.1
1.3
0.16
was established.
USA, OK, Ok. City
38.0
5.0
0.1
0.02
(F). Solvent treatment - Solvent
treatment
of the oil is considered
USA, OK, Tonkawa
40.8
2.5
0.2
0.08
to be beneficial in some cases
France, Lagrave
43.0
7.5
4.0
0.53
because it dilutes the crude oil
USA, LA, Rodessa
43.8
3.5
0.0
0.00
and reduces the tendency of the
heavy organics to precipitate.
USA, PA
44.3
1.5
0.0
0.00
Solvent treatments may not be
Algeria,
very successful largely because
45.0
3.3
0.15
0.05
Hassi Messaoud
the solvents which can be used
USA, OK, Davenport
46.3
1.3
0
0
are limited to aromatic solvents
(fig.15). Xylene is generally
especially where asphaltenic crudes are present [49]. It is the most common solvent selected to be used in well
possible to perform certain experimental measurements stimulations, workovers, and heavy organics inhibition
to produce rather simple phase envelops like figure 25 and cleaning. In some cases xylene injection through
through which one can define the composition regions the non-producing string (inner tubings shown in
of the heavy organics separation at certain temperature fig.24) actually may help to minimize the heavy organic
and pressures.
deposition problem. In oil fields with frequent need for
Such experimental compatibility tests may be costly if aromatic wash it may be necessary to design an aromatic
one needs to study all the possible regions of composition solvent with stronger wash power and better economy
and pressure. However, static and dynamic compatibility for the particular deposit in mind [52].
modeling using the advanced statistical and fluid
Laboratory tests (fig.28) may be necessary to blend
dynamic techniques can be quite efficient and economical an appropriate aromatic solvent and/or dispersant for a
Asphaltene
Resin
Asphaltene, wt%
Resin, wt%
o
Reservoir and petroleum engineering
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suspended without deposition. Considering such severe
exceptions to the rule one should not consider this
ratio to be the only factor in evaluating the deposition
potential of a crude oil. Other factors including the nature
of hydrocarbons in the crude, the polydispersivities
and polarities of asphaltene and resin, the presence of
such compounds as paraffin /wax, organometallics and
diamondoids, the nature of conduit, hydrodynamics
and electrokinetics have also roles in the deposition.
In order to quantify all these factors one has to use a
comprehensive predictive model in which all these
effects are incorporated [41].
Reservoir and petroleum engineering
Conclusions
Figure 28. A laboratory model to test various
solvents for heavy organics remediation [52]
given oil field from the points of view of effectiveness,
economy, and environmental concerns. Then special
formulas may be blended to achieve the goal of preventing
or cleaning the heavy organics deposits which can be
used by the field engineers.
[G). HOT OIL TREATMENT - Circulation with hot
oil may be used to avoid or reduce the heavy organics
deposition problem. A combination of solvent treatment
and reverse and normal circulation with hot oil have
been tried in the past in some oil wells with mixed
results [49, 3, 4].
(H). DISPERSANT USE - Injection of dispersants or
antifoulants may be effective in certain crude oils where
the ratio of resin to asphaltene is not high enough to
prevent asphaltene flocculation and as a result heavy
organics deposition. One thing which appears to have
universal acceptance is that resins in the crude act as
the peptizing agents of the asphaltene particles. It is
generally a good practice to analyze a crude oil for its
asphaltene and resin content and ratio. In Table 1 such
data for a number of crude oils are reported versus their
API gravity. Crude oils with higher asphaltene to resin
ratios are more prone to heavy organics deposition. Of
course there are exception to this rule mostly due to the
possibility or presence of high amounts of aromatics
in the crude, variations in the molecular structures of
asphaltenes and resins, and the polydispersivity effects.
For example, Boscan crude, which is second from the top
of the list in Table 1, has had no deposition problem, while
Tecoaminocan crude, which is close to the bottom of the
list, is a crude oil with frequent deposition problems.
Actually in Boscan crude, in addition to having a low
asphaltene/resin ratio of 0.58 it has also a low saturates/
aromatics ratio of 0.71.
High amounts of resins and aromaticity helps the
asphaltene in this crude to stay in the solution and/or
20
Insofar as finding a rigorous universal solution to the
heavy organics deposition problem is concerned there
is still a long way to go. Asphaltene flocculation can be
controlled through better knowledge of the mechanisms
that cause its flocculation in the first place. Processes can
be changed to minimize the asphaltene flocculation and
chemical applications can be used effectively to control
depositions when process changes are not cost effective.
Since heavy organics deposition takes place during
primary, secondary, and tertiary oil recovery, injection
of peptizing agents (i.e.: resins) in proper amounts
and places may prevent, or at least control, the heavy
organics deposition problem. Furthermore, experiments
could be performed (i.e.: of the coreflood type) where
peptizing agents are injected to study their effect on
inhibition of heavy organics deposition or permeability
reductions. However, use of such additives to crude oil
is economically quite prohibitive.
One interesting question posed by previous
researchers [53, 50] is why there was asphaltic bitumen
deposited at the bottom of the well considering that no
phase change or any substantial temperature or pressure
changes had taken place. The conclusion was that the
question could only be answered after considerable
light was thrown upon the nature of the asphaltic
bitumen prior to its separation from the crude oil in the
well. There were a few efforts to try to determine the
size and nature of asphaltene particles while they still
are in the original oil [53, 54].
Establishing the state of the asphaltene particles in the
original crude oil seems to be a basic building block in
the scientific quest to find a solution to many irreversible
heavy organics deposition problems. Experimental and
theoretical modeling work towards this end has been
performed [55, 9], but more is needed. More experiments
need to be done to duplicate Witherspoon et al.s’
ultracentrifuge work for different oils and possibly utilize
other contemporary experimental techniques to establish
the state of asphaltenes in crude oils. Meanwhile, it
appears that any modeling effort that describes the phase
behavior of asphaltenes in oil should take into account the
lack of positive information on the structure of asphaltenes
in the original oil and their molecular characteristics. This
has been the philosophy followed in modeling activity [56,
38, 23, 12] proposed for predicting the deposition behavior
of heavy organics in petroleum fluids.
Acknowledgements: The author appreciated the
contributions of Dr. J.H.P. Sanchez in the initial stage
of this research. This research was supported in part by
PEMEX, IMP and Petrobras.
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04.2010
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Удаление асфальтенов и других тяжёлых органических
отложений из нефтяных скважин и трубопроводов
Реферат
В статье представлены методы и анализ удаления тяжёлых органических веществ в добыче,
транспорте и переработке нефти. Прежде всего идентифицируются тяжёлые органические вещества, которые отлагаются из нефтяных жидкостей, и отмечается, что более сложными элементами
этих соединений являются асфальтены. Представлены шесть различных групп методов локального удаления: (i) изменение схемы добычи; (ii) химическая обработка; (iii) воздействие внешних
сил; (iv) механическая обработка; (v) термическая обработка; (vi) биологическая обработка. Также
представлены восемь этапов, которые оказываются необходимыми и эффективными при предотвращении, снижении интенсивности и удалении отложений: (a) прогнозное моделирование и
анализ; (b) заканчивание нефтяных скважин в двух горизонтах; (c) испытания на совместимость
закачиваемых жидкостей перед применением; (d) анализ состава тяжёлых органических веществ
в пласте при разработке схемы добычи; (e) применение методов механического удаления отложений; (f) применение растворителей для удаления отложений; (g) обработка горячей нефтью;
(h) использование дисперсантов для предотвращения отложений тяжёлых органических веществ,
особенно асфальтенов. В целом, правильный путь борьбы - это анализ сочетания прогнозного
моделирования, экспериментирования и удаления отложений.
Reservoir and petroleum engineering
Г.Али Мансури
(Университет Иллинойса)
Neft quyuları və kəmərlərində ağır üzvi çöküntü və asfaltenlərin təmizlənməsi
G.Ali Mansuri
(İllinoys Universiteti)
Xülasə
Məqalədə neftin çıxarılması, nəqli və emalı proseslərində ağır üzvi birləşmələrin təmizlənməsi
üsullarının təhlili təqdim edilir. İlk olaraq neft məhsulundan çökən ağır üzvi birləşmələr müəyyən
edilir və qeyd edilir ki, bu tərkiblərin ən mürəkkəb komponentləri asfaltenlərdir. Lokal təmizlənmənin
altı müxtəlif üsullar qrupu təqdim olunur: (i) neftçıxarma sxeminin dəyişməsi; (ii) kimyəvi emal; (iii)
xarici qüvvənin təsiri; (iv) mexaniki emal; (v) istilik emalı; (vi) bioloji emal. Həmçinin çöküntülərinin
qarşısının alınması, intensivliyinin azaldılması və təmizlənməsində zəruri və səmərəli ola bilən səkkiz
mərhələ təqdim edilir: (a) qabaqcadan proqnozlaşdırma və təhlil; (b) quyunun iki məhsuldar layda
tamamlanması; (c) tətbiq etməzdən əvvəl vurulan mayelərin uyğunluq testi; (d) neftçıxarma sxeminin
işlənməsində laydakı ağır üzvi birləşmələrin tərkibinin nəzərə alınması; (e) çöküntülərin mexaniki
təmizlənmə üsullarının tədbiqi; (f) çöküntülərin həll olunması üçün həlledicilərinin tətbiq edilməsi;
(g) isti neft emalı üsulları; (h) ağır üzvi birləşmələrin, xüsusilə asfalten çöküntülərinin qabağını
almag üçün dispersantların istifadəsi. Ümumiyyətlə mübarizənin düzqün yolu - proqnozlaşdırılma
modelləşdirilməsinin, eksperimentlərin və ləğv edilmə üsullarının birləşilməsinin təhlilindədir.
23