PHYSICAL APPROACHES TO CONTROL SOLID WAX AND ASPHALTENE DEPOSITION

1
PHYSICAL APPROACHES TO CONTROL SOLID (WAX AND
ASPHALTENE) DEPOSITION

• ABDUL AZIZ ABDUL KADIR
• SAIFUL AZUAN MOHD. RAMLY
• DEPT. OF PETROLEUM ENG.
• UNIVERSITY OF TECHNOLOGY MALAYSIA.

2
CONTENTS

• Problem Statements
• Introduction of Physical Approaches
• Ultrasonic Cavitation as Removal Method
• Electromagnetic as Inhibition Method
• Design Criteria
• Field Application

3
1.0 Problem Statements

• Crude oil is an example of supersaturated fluid
  of which can exists in three different phases
  gas, liquid and solid, depending on temperature,
  pressure and chemical incompatibility.
• Stability of supersaturated fluid approaching the
  saturation point is a main concern during the
  production oil and gas.
• Two major types of solids known as Paraffin Wax
  and Asphaltene. Their present usually cause
  various related problem in a petroluem production
  field particularly during delivery and separation.

4

• Waxes are higher molecular weight saturated
  carbons (gtC18) mainly from normal paraffins plus
  minor isoparaffins, naphthenes and appreciable
  aromatic content. It precipitates as crystalline
  waxy solids.
• Asphaltenes mostly high molecular weight
  aromatics. It precipitates as amorphous solids.
  Asphaltene deposition is considered to be a major
  cause of wettability reversal inside an oil
  reservoir. Wettability alteration can result in
  either decrease or increase in oil recovery
  efficiency.
• Both solids also cause the formation of stable
  emulsion and special formulated emulsion breaker
  is required to expedite oil-water separation.

5

• Figure 1.0 shows the mechanism of wax is
  deposited on the pipe wall.
• The flocculation or formation of wax crystal
  occur as the oil reach the saturation point
  called wax appearance temperature (WAT). This
  point can be determined by various method.
  Amongst popular method are polarised microscope
  and differential scanning calorimetry.
• Similarly, asphaltene deposit is formed due to
  the present of asphaltene flocculant.
• In this presentation, we will discuss only on the
  possible physical technique to remove and control
  paraffin wax formation.

6
MECHANISMS OF LATERAL TRANSPORT
Eff. Dia.
Paraffin Wax Deposit
7
2.0 Introduction to Physical Approaches

• There are two approaches will be discussed here
• Application of Ultrasonic Cavitations.
• Inducing Electromagnetic Force.
• Why we called Physical Approaches.
• There are not an ordinary mechanical, chemical
  nor thermal methods used to remove or inhibit
  deposition.
• No chemical change in the fluid.
• Change the kinetic of crystallization process.
  
• Use high frequency external force to break the
  deposition.

8
3.0 Ultrasonic Cavitations

• What is "Ultrasonics?"Ultrasonics is the
  science of sound waves above the limits of human
  audibility. Ultrasound is a sound with a pitch so
  high that it can not be heard by the human ear.
  Frequencies above 18 Kilohertz - Ultrasonic.
  Ranging from 20,000 cycles per second or
  kilohertz (KHz) to over 100,000 KHz.
• Commonly used frequencies between 20 KHz and
  50KHz.

9
Principal

• If increased sound amplitude is applied to
  nonelastic media such as water or other
  liquids, the liquid tends to fracture because
  of the negative pressure, causing a phenomenon
  known as cavitation.
• As the wave fronts pass, the cavitation
  "bubbles" oscillate and grow to an unstable
  size. Finally, the violent collapse of the
  cavitation "bubbles" results in implosions,
  which cause shock waves to be radiated from the
  sites of the collapse

10
Figure 2.0 (a) Cavitation and (b) Figure of
Cleaning Surface
(b) Cleaning Surface
(a) Cavitation and Implosion
11
Figure 3.0 Wax removed versus power intensity of
ultrasonic, at 25 KHz (Re 85 and Re 55) for
30 minutes exposure period
Full Wave at Re85
Full Wave at Re55
12
Figure 4.0 Wax removed versus power intensity of
ultrasonic, at 25 KHz (Re 85 and Re 55) for
60 minutes exposure period
Full Wave at Re85
Full Wave at Re55
13

• This photo was taken before exposing to
  ultrasonic cavitation and flow. The pipe section
  was poured with waxy crude and chilled at the
  temperature about 5oC

14

• This photo was taken after exposing to ultrasonic
  cavitation and flow. The pressure drop across the
  deposition section was monitored until reduced to
  a constant value

15
4.0 Magnetic and Electromagnetic Force

• Magnetism is the property of a bulk material or
  molecule to be attracted or repelled by a
  magnetic field.

Vacuum (original condition)
Paramagnetic
Diagmagnetic
16

• The degree to which a material can be magnetized
  in an external field is called Magnetic
  Succeptibility.
• It is expressed per unit volume, as volume
  succeptibility,
• ? M/H
• Where M is the volume magnetization induced in
  a material of succeptibility ? by the applied
  external field H. The value depends on the
  measurement system used.
• ? (SI) 4 ?? (cgs) 4 ? G Oe-1
• Where G and Oe-1 are abbreviations for Gauss
  and Orstedt. Mass Magnetic Succeptibility also
  can be expressed as
• ? ???

17

• Magnetic succeptibility is used as a proxy
  indicator for inhibiting the paraffin wax in
  conduit or pipe. Crude oil has a negative value
  of succeptibility and therefore is classified as
  diagmagnetic fluid.
• When a crude oil is exposed to the magnetic
  field, the electrons of HC are circulated about
  the axis of the applied field. And this
  circulating electrons induce another magnetic
  field.

Example of electrons circulation for Benzene
18

• There are two principals of magnetic treatment
  for the paraffin wax inhibition and removal.
• By using a strong permanent magnet
• By using an electromagnet devices
• The permanent magnet concept claimed that the
  device reduces the kinetic of wax crystallization
  process and the surface tension, so that
  eliminate the mechanical adhesion of the sticky
  paraffins to one another by keeping these
  paraffins in solution.
• However, another finding had claimed that the
  magnetic treatment operates primarily on the
  zero charged suspended molecule clusters after
  the oil drops them out of suspension.

19
Oil Flow
Schematic Diagram of Permanent Magnet Type
Invasive requires pipe
cutting. Non-Invasive External Installation
Oil Flow
20

• Introducing of electromagnetic principal to
  eliminate of deposition and inhibit wax
  crystallization are more convincing and
  acceptable.
• Paraffin molecules are polarized as dipoles when
  flow thru the magnetic field. Each south and
  north poles are attached to opposite poles of
  another molecules. With a long chain of paraffin
  wax molecules holding hand, they are unable to
  attach themselves to the wall of pipe.
• The present of magnetic flux through out the body
  of pipe (ferromagnet) provides a Lorentzs force
  that keeps the suspended waxes at the axis of the
  flow.

21
Non-Permanent Magnet Devices
Oil Flow
Electrostatic, where an electric field is imposed
on the oil flow, which serves to attract or repel
the ions and, in addition, generates a magnetic
field.
Oil Flow