This presentation gives a description on wax dispersant, wax modifier and wax dissolver used in crude oil fields.

1. Wax Dispersant, Wax crystal
Modifier and Wax Dissolver
Review: Theory and Application
Chandran Udumbasseri

2. Wax deposition problem
• At lower temperature crystallization of waxes
creates problem in crude oil pipeline.
• The waxes generally crystallize as an interlocking
network of fine sheets,
• They trap the oil in cage like structure and cause the
blockage of pipeline.
• To overcome such problems crude oils have been
widely treated with chemical additives (flow
improvers/pour point depressants) to improve their
flow properties at low temperature

3. Wax dispersant-function
• Wax dispersants modify the size and shape of
wax crystals.
• These chemicals are capable of growing in to wax
crystals and alter their growth and surface
properties
• They reduce affinity of crystals to interlock and
form their dimensional network thereby lower
pour point and viscosity
• These chemicals solve wax deposition problem
during transportation

4. Wax dispersant- characteristics
• A linear polymer or copolymer with pendant alkyl
side chains of specific length and nature is one of the
general characteristic of flow improvers for waxy
crude oil
• They often possess highly polar functional groups.
• This polarity is similar to a surfactant character. This
is considered as the basic prerequisite for the
dispersant
• Polar nitrogen containing polymers can function as
wax dispersant and flow improver.

5. Paraffin wax in crude oil
• Crude oil wax contains linear carbon chain with C18 to
C75+ carbon atoms. These are macro crystalline wax
causing deposition during production and
transportation.
• Naphthalene wax having carbons C18 to C36 is called
micro crystalline wax which causes deposition in tank
bottom sludge
• Some crude oil shows n-paraffin/iso-paraffin ratio in
the range of 1.28 to 0.23.

6. Structure of paraffin waxes

7. Wax Deposition Process
• Wax deposition is a 2 step process, nucleation and
crystal growth.
• Wax deposition in production is through asphaltene
and inorganic solids which act as nucleation agents.
• The deposit is soft to hard in behavior and brittle.
• The deposit may contain, asphaltene, resin, gum,
fine sand, salt, clay, soil, water, etc..

8. Wax modifiers
• Wax modifiers co-crystallize with paraffin wax
and thus disturb crystal growth
• Wax modifiers: maleic acid esters, polymeric
acrylate and methacrylate esters, ethylene
vinyl acetate polymers and co polymers.
•

9. Additives to prevent wax crystallization
• Wax dispersants are surfactants that help wax crystals
dispersed within the oil
• Wax crystal modifiers reduce the tendency of wax molecules
to network and form lattice structure within the oil. They also
reduce viscosity and wax gel strength
• (Cold) Flow improvers work by modifying the growth of
crystallizing wax particles. As crystals form, flow improvers
act as nucleators and co-crystallize with the saturated
hydrocarbon chains, modifying the wax crystal size and
shapes from plate-like to needle-like
• Pour point depressants are components that prevent wax
fraction in the oil from forming large crystal network.
• So all additives are to stop crystal growth below wax
appearance temperature (WAT or cloud point)

10. Wax dispersants- requisites
• The additives reduce the possible hydrogen bonding between asphaltene
and resin.
• The pendant alkyl chain present in the additive should match with wax
crystals present in the crude oil.
• The additive make stronger bonds with asphaltene and resin
• The efficiency of additives depend on total wax content, length and type
(aliphatic, aromatic, branched) of pendant groups, and type of wax
• The more similar the polymer structure to wax components the better the
performance
• Performance of an additive is determined by its ability to keep the wax
components in solution its ability to attach the wax components and
create a barrier for networking or coalescence of the wax particles
• The oil soluble additive with long chain alkyl group and polar structure
moiety in the molecule causes insertion of long chain to wax crystal in the
crude oil and the polar portion remains on the crystal surface. This
reduces the chances to form crystal lattice and thereby inhibit crystal
growth.
• Nitrogen based polymer shows both wax dispersant and flow improver.
The dispersing effect is mainly due to nitrogen/oxygen containing group in
the polymer.

11. Wax Crystal Modifier
• Wax crystal modifiers are having similar structure as wax that
is precipitating
• Modifiers are polymeric compounds with wax like structure
having one or more hydrocarbon chains and a polar portion
• The modifier, co-precipitate or co-crystallize with wax thus
occupy the position of wax molecule within crystal lattice
through hydrocarbon chains
• It causes steric hindrance on the crystal there by interfere
crystal growth.

12. Crystal modifiers-Chemistry
• Ethylene vinyl acetate (EVA)
• Polyethylene-poly(ethylene-propylene) (PE-PEP)
• Poly (ethylene-Butene) (PEB)
• Poly (maleic anhydride-co -α-olefien) (PMAC)
• Polyoctadecyl methacrylate (ODMA)
• Poly [N N’ diallyl-N- octadecyl amine-alt-maleic acid)
• Poly amino amide (PAA)
• Maleic anhydride-vinyl acetate (MAVA)
• Octadecyl methacrylate - maleic anhydride-styrene (OMS)

13. EVA: Polyethylene vinyl acetate
• EVA is most extensively used
• Linear chain with polyethylene portion of varying length based
on vinyl acetate monomer.
• The produced wax crystals are small in size
• EVA 30 (%) is good PPD
• For high carbon number waxes EVA(32%) is more effective
• Structure

14. Polyethylene-Poly(ethylene-
propylene) – PE-PEP
• PE-PEP can function as nucleators for wax
crystal size control in middle distillate fuels.
• It has plate structure giving chance for wax
crystal nucleation platform for long chain
paraffins

15. Poly (ethylene – butene)
• Co crystallizes with wax forming rod like or
shuttle like structure causing low yield stress

16. Poly(maleic anhydride amide co-α-olefin) (MAC)
• The presence of flocculated
asphaltene in crude oil generates
crystallization sites, which increase
the cloud point of the crude oil and
interfere with the crystal inhibition
of MAC
• Largest alteration in crystal
structure.
• MAC polymers either self-assemble
to nucleate the crystallization of
paraffins or co-crystallize with them
to inhibit wax crystal growth.

17. ODMA
• Wax deposition inhibition 50%
• Does not alter wax
crystallization, but avoid wax
agglomeration
• Modified polymer (poly (NN’
diallyl N octadecyl amine -alt-
maleic acid) shows efficiency
as flow improver and wax
inhibitor

18. Poly[N,N-diallyl-N-octadecylamine-alt-(maleic acid)]
• This polymer is efficient
flow improver and wax
inhibitor for waxy crude
oil
• The efficiency of
polymer results from the
presence of hydrophobic
chains and streongly
interacting zwiterionic
moities

19. Maleic acid based copolymers

20. Maleic acid based copolymers
• The above shown polymers are maleic acid based
copolymers
• These products satisfied most of the requirements
for flowability improvement and wax inhibition
• b and c showed wax inhibition of 63-67%
• The performance improvement is due to the
presence of hydrocarbon chain, double bonds and
aromatic parts.
• Maximum efficiency was obtained for samples
having longest branch chains (C18 left; C22 right)

21. Wax dispersants-Polymer structure
• Courtesy : Wax dispersant additive for improving low temperature flow behavior of waxy
crude oil: S. Deshmukh & D.P.Barambe; Energy Sources, Vol 34, 12, 2012

22. Polymer structure

23. Polymer structure

24. Polymer structure

25. WAX DISSOLVER
Chandran Udumbasseri

26. Methods of Wax Dissolution
• Inorganic aqueous solution
• Organic acid – base reaction
• Organic surfactants and light organic solvents

27. Wax deposition and removal
• Crude oil produced from oil and gas wells will frequently contain normally
solid paraffinic hydro carbons which tend to accumulate in the well bore
and in the equipment utilized for producing the crude oil
• Solid paraffin frequently tend to accumulate in transportation lines,
storage vessels, and other equipment wherein the crude oil is processed.
• Deposition of paraffin interferes with the production, transportation,
storage, processing, etc. of the crude oil containing this material
• Old method of cleaning the well was mechanically scrapping
• It has been a practice to use chemicals to clean. Chemical solvents clean
only paraffin, and other hydrocarbons soluble in the solvents
• When used in wells even though the paraffin was dissolved other mud
and sludge make the slurry to an impossible state to remove from well
• Acid base reaction was used to generate heat. Controlling the heat was a
difficult task. This heating damaged the equipments

28. Wax dissolving process – 1-
Inorganic solution
• The present method is to provide a process
without disassembly of equipments and pipe
lines.
• The process is not using any costly solvent
• The process is easy to handle
• The process is capable of cleaning wells,
pipelines without re-deposition of paraffin

29. Method of Treatment
• The process consists of two solution, solution A and
solution B
• The addition of these solutions is in the ratio 3-5: 1
(for every 3-5 parts of A add 1 part of B)
• The solutions are introduced directly (pumping well,
producing well, gas lift well, flow line, transmission
line, storage tank, etc)
• A flow line having paraffin deposition can be cleaned
by introducing solution A followed by solution B
• Further washing with water completely cleanse the
flow line.

30. Composition
• Ingredient A: this material wets out each particle
(wax and other slits) and cause them to repel each
other and remain in suspension. This is also good
heat transfer agent
• Ingredient B: liberate heat through mild acid-base
reaction
• Ingredient C: non ionic surfactant
• Wetting agent: penetrate the wax
• Dispersant: keeps wetted particles in suspension

31. Characteristics of wax deposition-Method 2
• The wax deposited in crude oil pipe lines are not pure wax
only.
• Normally it contains 30-50% oil in volume.
• So the deposits are porous in nature. The oil can be drained
out from deposits. So the deposits are permeable.
• The space in between can be replaced by other fluids.
• Light oils mixed with surfactants can penetrate the wax and
displace oil and break the wax deposits
• Broken fragments can be displaced from pipe lines in the
form of slurry by the light hydrocarbon.
• The wax fragments of size 3/16th
inch was found in the slurry.
• The cleaning solution can be used further in the subsequent
pipelines.

32. Ingredients of the cleaning solution
• Apart from light oil (45-50 degree API,
viscosity at 10o
C, 0.5-1cSt), the solution
contains:
• 1. Surfactant
• 2. Stabilizer
• 3. Descaler
• 4. Rust remover
• 5. Emulsion breaker

33. Method of Treatment
• Flush the line at high velocity to remove freed
solids of wax
• Flushing can be with crude oil
• Emulsified crude oil gives better flushing
• Oil with surfactant may be kept in contact
with wax from 1 to 12 hrs

34. Wax melting by heat generation-3
• Heat generated by acid base reaction is used to melt the wax
deposits
• Organic salts of the neutralization reaction acts as dispersant
and disperses the fragments of wax
• Inorganic acids: H2SO4, H3PO4, HCl
• Organic acids: alkyl aryl sulfonic acid, linear or branched
dodecyl benzene sulfonic acid, dinonyl/isopropyl naphthalene
sulfonic acid
• Inorganic base: NaOH, MgO, Na2CO3, MgCO3,
• Organic bases: alkylamines, polyamines

35. Method of Treatment
• More hydrophilic salts and solvents are effective for
emulsified waxes when more produced water is present
• Lipophilic salts and solvents are effective for more oily waxes
when produced water is less.
• The organic component can be added directly to oil or in a
solvent
• Crude oil, kerosene, toluene, etc can be used for pumping
directly to the deposit
• Both base and acid component can be mixed and added to
the point where the wax deposit is present

36. END