A brief review of Paraffin and asphaltene deposition mechanisms, problems and suitable treatments.

1. Asphaltenes & Wax
deposition in production
system & remedial
measures.
Faculty Mentor: Prof. SSP Singh
Presented by- Lijo P. Lalu
Chirag Vanecha

2. Introduction
• Paraffin or asphaltene problem-
organic deposits hampering production
• Loss of production depends on amount
and location of the deposition
• Paraffins as major organic deposits, asphaltene deposits prominent in
low API gravity crude
• Paraffin characteristics and asphaltene content vary from reservoir to
reservoir – Wax removal treatment also varies

3. • Single chain or branched n-alkanes (CnH2n+2).
• High-molecular-components as major solid precipitates.
• Deposits contain alkanes varying from C-20 to C-60.
• Melting point range: 98 F to 215 F.
• Cloud point or Wax Appearance Temperature & pour point
determination by ASTM D 2500-66 & ASTM D 97-66.
• Deposits burn rapidly over a narrow temperature range with little
residue.
Paraffin-Wax

4. Factors for Paraffin Deposition
• Temperature differential – crude oil temperature
& cooling rate pipe wall temperature
ambient temperature

5. Factors for Paraffin Deposition
• Flow rate - deposits more in laminar flow then turbulent
- deposition reduces with increase in flow rate
• Pressure
- wax solubility reduces as reduction in pressure
- Gas expansion and production reduce pressure
• Crude oil Composition
- based on paraffin, asphaltenes variation with crude
• Pipe surface properties
- deposition  contact area, roughness

6. Removal of Wax deposits
• Deposits vary from reservoir to reservoir also from well to well of
same reservoir
• Four Methods for Removal of wax: 1) Mechanical
2) Heat (Thermal)
3) Solvents
4) Dispersants
Preventing Wax deposition
• Crystal Modifiers
• Plastic pipelines & plastic coatings
• Surfactants as deposition inhibitors
• Downhole Heaters

7. Mechanical
• Scraper or Cutter –
attached at the end
of sucker rods
• Wireline-scraping
tool – Gas lift & Self
flowing well

8. Heat (Thermal)
• Hot oiling – HOC- paraffin is dissolved and melted
• Normally pumped down the casing and up the tubing
• Can be pumped in reversed manner in case of self flowing well
or when lift equipments permit.
• Gas lift – with Coil Tubing Unit
• Circulate with temperature > Formation temperature
• Chances of formation plugging
• Hot water/ steam can be used
in low temperature reservoirs
• Effective removal is difficult-
in case of large accumulations

9. Solvents
• Use of Paraffin solvents- Carbon tetrachloride & Carbon disulfide
• Condensate, kerosene and Diesel oil – Asphaltene content low as
they are not soluble in straight chain HCs.
• Xylene and Toluene - for Asphaltenes and Paraffins both
+ moderate heating will fasten the removal
• Additives: ACI, PPD, surfactants
• Circulation of solvents down the annulus and back from the
tubing
• If formation is plugged with wax, then squeeze solvents and
surfactants - soaking for 24 to 72 hours
• Solvents soften the deposits – facilitates sucker rod pulling

10. Dispersants
• Water soluble dispersants
• Halliburton’s Paraperse – with 2% to 10% concentrations
• It can 50 times more paraffin as the best solvent.
• In case of Hard and dense paraffin - soaking for 2-4 hours is
more effective.
• Surface lines can also be cleaned

11. Preventing or decreasing wax deposition
• Crystal modifiers
• Paraffin comes out as single crystal and tend to agglomerate
around nucleus
• Removing nucleating agent- asphaltenes
• Halliburton’s Paracheck as crystal modifiers
• Modifies crystal growth and agglomeration

13. Preventing or Decreasing wax deposition
• Plastic pipe & coatings
-deposition much slower on plastic surface than steel
-pressure & Temperature ratings for PVC pipe.
-Phenolic/ Epoxy-resin coated
• Surfactants as deposition Inhibitors
-To keep pipe-surface water-wet as barrier for wax deposit
-when water-oil ration is high- pipe surface is water-wet
-sometimes as solvent for nucleating agent
• Downhole Heaters

14. Asphaltene Deposition and Remedial Measure
• OUTLINE
 BASIC UNDERSTANDING OF ASPHALTENE
HOW ASPHALTENE DEPOSITION TAKES PLACE?
 FACTORS AFFECTING ASPHALTENE DEPOSITION
WHERE ASPHALTENE DEPOSITION PROBLEM GENERALLY ARISES?
ASPHALTENE DEPOSITION ENVELOPE
DIAGNOSIS, PREVENTIVE ACTIONS AND CORRECTIVE MEASURES

15. What asphaltenes basically is?

16. Asphaltene
• Asphaltenes are a compound class,
not a single compound, concentrated
in the high-temperature distillation
residue of petroleum (> 530°C).
• Other components are:
Heavy oils
Resins
High-molecular-weight waxes
Solubility sequence used to define asphaltenes
Source- Petrowiki

17. Asphaltene
• In chemistry, asphaltenes are
defined as a solubility class. They
do not dissolve in gases or in
alkane liquids such as n-
heptane[C7 H16], but they do
dissolve in aromatic hydrocarbons
such as toluene or xylene.
Hypothetical/generic structure of an asphaltene
Source- Petrowiki

18. Resin
• Petroleum resins are nominally C30
compounds and are different from
nonpetroleum resins, which tend to
be a 3- to 5-membered condensed
aliphatic ring structure.
• The aliphatic side chains are the
nonpolar groups
• The condensed aromatic rings are
the polar group
Hypothetical/generic structure of Resin
Source- Petrowiki

19. SARA

20. SARA effect on the stability of several crude oils regarding asphaltene precipitation.
(Source- Petrowiki)

21. How Asphaltene Deposition take place?
•When bonding chemistry between asphaltene aggregates
and the solvating entities in the crude oil is disrupted, the
aggregates come out of solution and flocculate to form larger
particles.
•These flocs are the source of the operational problems. Only
after flocculation occurs does deposition occur.
•The sequence of forms for the asphaltene during oil
production is soluble → colloidal particles → flocculated →
deposit.
•Shear effects and electrokinetic effects during flow have
been claimed as additional mechanisms for asphaltene
precipitation.

22. Factors affecting Asphaltene deposition?
•Asphaltene precipitation is caused by a number of factors
including changes in pressure, temperature, and composition.
• The two most prevalent causes of Asphaltene precipitation
in the reservoir are decreasing pressure and mixing of oil
with injected solvent in improved oil recovery (IOR)
processes.
•Drilling, completion, acid stimulation, and hydraulic
fracturing activities can also induce precipitation in the near-
wellbore region.

23. Where Asphaltene deposition generally arises?
• During Primary Depletion
 In normal pressure depletion, reservoirs that experience
asphaltene precipitation usually have the following
characteristics.
oFluid in place is light to medium oil with small asphaltene
content.
oInitial reservoir pressure is much larger than the saturation
pressure. That is, the fluid is highly undersaturated.
oMaximum precipitation occurs around the saturation pressure.
oHeavier crudes that contain a larger amount of asphaltene have
very few asphaltene precipitation problems because they can
dissolve more asphaltene.

24. Where Asphaltene deposition generally arises?
• The injection of hydrocarbon gases or carbon dioxide (CO2)
for IOR promotes asphaltene precipitation.
• Asphaltene precipitation also may occur during solvent
injection into heavy oil reservoirs. VAPEX process uses two
horizontal wells (one injector and one producer). The
injection of solvent (e.g., propane) creates a solvent
chamber in which oil is mobilized and drained toward the
producer.
• In addition to the mobilization process, the solvent may
induce asphaltene precipitation, which provides an in-situ
upgrading of the oil.

25. Where Asphaltene deposition generally arises?
• Mixing of incompatible crude oil at flowline level,
production tubing level or in any other facilities can also
lead to asphaltene precipitation.

26. Asphaltene Deposition Envelope
Pressure dependence of asphaltene
precipitation (cumulative) at
constant temperature, 100oC
Source- Petrowiki

27. Asphaltene Deposition Envelope
A pressure/temperature phase
diagram for the stability of
asphaltenes in a crude oil
Source- Petrowiki

28. Asphaltene Deposition Envelope: Measuring Techniques
• Gravimetric Technique
• Light Scattering Technique
• Filtration Technique
• Electrical Conductance Technique
• Viscometric Technique

29. A Typical Graph generated after Gravimetric Technique
Gravimetric Technique
(Source: Petrowiki)

30. Diagnosis of Asphaltene Precipitation
STEP 1:
DETAILED ANALYSIS OF
RESERVOIR FLUID

31. Diagnosis of Asphaltene Precipitation
STEP 2:
DETERMINATION OF PRESSURE
PROFILE
Determination of Pressure
Profile will enable to select the
optimum choke size to displace
the zone of maximum
occurence of precipitation to
near well surface.

32. Diagnosis of Asphaltene Precipitation
STEP 3: THRESHOLD OF
FLOCCULATION AND ZONE OF
MAXIMUM PRECIPITATION
Influence of Temperature on
Asphaltene Precipitation is
Neglected

33. Diagnosis of Asphaltene Precipitation
STEP 4:PHASE ENVELOP
PHASE ENVELOP IS A
POWERFUL TOOL TO PREDICT
ASPHALTENE PRECIPITATION

34. Diagnosis of Asphaltene Precipitation
STEP 5: EVALUATION OF
STATBILTY LEVEL AND
COMPATIBILITY OF OIL
Purpose is to establish possibilty
of mixing fluids proceeding from
different lens and programming
segregation of oils at manifold
level

35. Diagnosis of Asphaltene Precipitation
STEP 6: CHARECTERIZATION OF
DEPOSITS
Purpose is to know the
composition of deposits in
production tubing and surface
installations.

36. Preventive Action for Asphaltene Precipitation
STEP 1:CONTINUOUS CHEMICAL
INJECTION
It minimizes the probability of
asphaltene precipitation in
production tubing and surface
facilities.
If zone of precipitation is near
perforation, go for hydraulic
fracturing.

37. Preventive Action for Asphaltene Precipitation
STEP 2: INJECTION OF
DISPERSANT IN THE RESERVOIR
When zone of precipitation is in the
vicinity of perforation, preventive
measure will be to inject
dispersant into the reservoir.
In principle, it is possible that it
could also cause formation damage
by altering the wetting properties
of the rock. It is obviously prudent
to evaluate this possibility on core
samples before treatment.

38. Corrective Measure for Asphaltene Precipitation
STEP 1:COIL TUBING/ SNUBBING
UNIT AND/OR USE OF AROMATIC
SOLVENT
If deposits are in production
tubing, coil tubing operation or
snubbing unit is used with or
without aromatic solvent.
If it occurs at choke level or at any
other surface facilities,
Solvents such as toluene and
xylene are used.
In extreme cases, scrappers are
used or pipes are cut.

39. Corrective Measure for Asphaltene Precipitation
STEP 2: HYDRAULIC FRACTURE
TREATMENT
If zone of maximum deposition is in
production tubing or at sand
surface, hydraulic fracturing is
done to reduce pressure
differential and to displace the
zone nearer the wellhead where
dispersant injection can handle it.

40. Corrective Measure for Asphaltene Precipitation
STEP 3:PERFORATION
If zone of maximum deposition is in
perforation, re- perforation should
be considered as an ideal solution.
Greater the charge density,
penetration of perforation and
angle of phase, lower will be
apparent damage to perforation.
Proper kick-off pressure should be
applied for tunnel cleaning, else
obstruction material will be a good
nucleation site for Asphaltene
precipitation

41. Recommended Practise
• Chemical treatment to dissolve asphaltene should have minimum
70% xylene and maximum 30% gas-oil.
• Use dry gas for gas-lift system and reservoir gas injection and
rich gas should strictly be not used.
• Analyis of Crude oil compatibilty should be made
• A monthly analysis of asphaltene content should be made for well

42. Recommended Practise
• Analysis of fluids for hydraulic fracturing and completion should be
checked if it is compatible with produced oil.
• Acid stimulation should not be done without previous analysis