Quick introduction to Low Shear. A quick dive into the meaning of Low shear and Low shear technology.

1. Low shear basics
LOW SHEAR TECHNOLOGY BASICS
FOR PETROLEUM INDUSTRY

2. Low shear basics
Challenges caused by shear forces in petroleum industry
Effect on Separation
Oil in separated
water
Water in
separated oil
Effect on
Transportation
Tighter
emulsion
Increased
drag
Effect on Injection
Broken
chemicals
Loss of
viscosity
Intense Turbulence Causes Fluid Shearing

3. Low shear basics
• There are more than 900,000 oil producing wells in the world. (Oil & Gas
Journal 2010)
• During the life of a well, 4-5 barrels of water are produced for
every barrel of oil. (Collins, A.G. 1987. Properties of Produced Waters. In Petroleum EngineeringHandbook, H.B. Bradley ed, Ch 24. Richardson, Texas: SPE)
• Daily worldwide oil production is around 97 million barrels per
day; while water production is roughly three times more, and
increasing (International Energy Agency)
• Water handling costs are in range from 5 to more than 50 cents
per barrel of water, i.e., for a oil producing well with 80% water
cut, the cost of handling water is up to 4$ per barrel of oil
produced. (Baily, B. et.al. 2000. Water Control. Oilfield review (Schlumberger))
• Polymer flooding is the most important chemical EOR method
used in sandstone reservoirs. The sweeping of oil by polymer
flooding may enhance the oil recovery by 5 – 11 %. (De Bons, F.E. and Braun, R.W. 1995. Polymer
Flooding: StillViable IOR Technique. European IOR Symposium)
Some Statistics in Petroleum Industry

4. Low shear basics
Fluid Flow in Oil Production
Nearly all macroscopic flows in engineering
practice in general and in oil industry in particular
have turbulent nature.
Turbulence is a dissipative flow state
characterized by nonlinear fluctuating three-
dimensional vorticity.
Oil, water and gas are flowing together from the
reservoir in a common stream. The dynamics of
several phases is called multiphase flow.
At low velocities the different fluids are separated
as in stratified flow. At high velocities fluids
become mixed. Slug flow is an example of a flow
regime in between, representing both separation
and mixing.

5. Low shear basics
Shear Forces in Turbulent Flow
Shear forces are normally present in the fluid flow because adjacent layers of the fluid move with
different velocities compared to each other.
In turbulent flow there are no well-defined layers. Instead, eddies (vortexes) of many sizes appear
and interact with each other.
The eddies introduce velocity fluctuations and create shear forces, which cause the bigger droplets
and bubbles of the dispersed phase to deform and possibly break-up, and smaller droplets to
collide and possibly coalesce.
The kinetic energy cascades from large scale eddies to smaller ones, eventually reaching smallest
structures where it dissipates in the form of heat.
The intermediate scale eddies between the largest and the smallest scale eddies have direct impact
on the bubbles and droplets in the flow as they have similar sizes as average droplets and bubbles.

6. Low shear basics
Considerable shear forces acting on the fluids passing
through the valves and pumps cause emulsification
and droplet break-up which have a detrimental impact
on downstream separator efficiency.
Even a moderate or low pressure differential over a
choke valve can cause strong emulsification of the
petroleum fluids.
Conventional centrifugal pumps tend to shear process
fluids significantly. Some rotary positive displacement
pumps, though, have good low shear performance.
Small droplets of dispersed phase are subject to the
competing processes of break-up and coalescence.
Moderate amounts of shear and mixing might be
beneficial for droplet growth.
Shear Forces in Process Equipment

7. Low shear basics
• Simultaneous flow of water and oil in turbulent regime leads to fluid mixing and shearing.
• In every process plant there are sources of unwanted turbulence.
• Shear forces acting in oil-water flow cause fluid emulsification.
• Strong emulsification results in:
– Reduced efficiency of separation equipment
as the small droplets are harder to separate.
– Need for additional use of chemicals and/or
heat treatment to achieve the desired levels
of separation.
– Water treatment systems may become the
bottleneck for overall process plant operation.
Effect on Separation
Shear in Separation Process

8. Low shear basics
Stokes’ Law describes the maximum vertical
velocity for a droplet or particle in a fluid. The
equation can be used to determine the time
required for separation.
The diameter of the droplet has the largest impact
on the rising velocity.
Hinze described the maximum stable droplet size
dmax that can exist in turbulent flow regime. Wcrit, ρ,
and σ are dependent on the fluid properties, and
can be regarded as constant. In order to increase
dmax, energy dissipation rate, ε, has to be decreased.
For the flow through a valve ε can be defined as:
Effect on SeparationEffect on Separation
Separation Theory

9. Low shear basics
The maximum droplet diameter dmax can be plotted as a function of the
turbulent energy dissipation rate according to the equation. Three values of
interfacial tension are considered (1, 5 and 30 mN/m), where the larger
interfacial tension is shown as the solid line. [1]
The graph shows the range of
turbulent energy dissipation
rate associated with straight pipe,
high-shear centrifugal pumps,
and control valves.
[1]. Walsh, J. The effect of Shear on Produced Water Treatment.
The savvy separator series: Part 5.
Effect on Separation Droplet Development

10. Low shear basics
• Water and oil flow in turbulent regime during the pipe transport.
• Turbulence and shear forces in valves cause fluid emulsification.
• Tight emulsions in a pipe results in:
– Increased apparent viscosity of the
mixture compared to the viscosities
of separate fluids.
– Increased viscosity lead to higher
friction around the pipe walls.
– Increased friction lead to higher
pressure losses during the fluid
transport.
Effect on
Transportation Shear During Transportation

11. Low shear basics
The pressure gradient dP/dx in pipe flow depends on: Pipe diameter, D, fluid viscosity, μ,
fluid density, ρ, and flow velocity, U. In addition, wall roughness and pipe inclination are
important.
Total pressure gradient in the pipe is composed of three different terms:
Shear forces and emulsification in the multiphase flow affect fluid viscosity, μ. Frictional
pressure gradient accounts the pressure losses due to fluid friction at the pipe wall.
Effect on
Transportation Pressure Loss in Pipes

12. Low shear basics
Effect on
Transportation
Emulsion viscosity can be substantially greater
than the viscosity of either component. The
apparent viscosity of very tight oil-water
emulsion is shown as a function of water cut
and shear rate:
(viscosity of oil alone is 20cp, viscosity of water <1cp)

13. Low shear basics
• When added to water, either as a solution or as powder, polymers increase the water
viscosity.
• During polymer flooding more oil will be pushed out and recovered from the reservoir
compared to only water flooding alone due to higher viscosity of the polymer solution.
• Polymer solutions are shear sensitive.
• High shear forces during polymer injection
results in:
– Polymer degradation.
– Loss of solution viscosity.
Effect on Injection
Shear in Polymer Injection

14. Low shear basics
Polymer flooding involves injection of polymer over an extended period of time,
until 1/3 – 1/2 of the reservoir pore volume has been injected.
The most used polymer for polymer flooding is hydrolyzed polyacrylamide (HPAM).
Polymers are very sensitive to mechanical degradation.
Shear degradation breaks the polymer macromolecular chain which induces strong reduction in
macromolecular size and solution viscosity.
Polymer such as HPAM is especially susceptible to degradation at high fluxes and flow through
valves, orifices, and in low permeability formations.
Effect on Injection
Polymer Flooding

15. Low shear basics
When polymers are subjected to high shear, they may readily be broken down. It is only when the
polymer is dissolved that the shear forces are harmful and degradation of the polymer occur.
The potential shear locations are:
- The polymer dissolution facilities: static mixers and pumps
- The injection lines: well head chokes and downhole valves
- The well bore entry: perforations and sandface.
At low shear rate, γ, the viscosity, η, is almost constant (A).
The point at which the polymer starts to degrade is called
critical shear rate. When shear rate increases, the viscosity
is reduced due to shear degradation (B).
Effect on Injection Mechanical Degradation

16. Low shear basics
Low Shear Technology – Control Valves
Control valves are designed to regulate process
specific parameters, such as flow rate, pressure drop,
temperature and liquid level. Control valves resemble
an orifice of some sort, which can change the
opening depending on a signal from a controller.
In a conventional control valve, the highest fluid
velocity gradients occur right after the restriction. It is
where intense turbulence is generated and energy is
dissipated.
The effective way to reduce shear forces, and hence,
the energy dissipation rate in a control valve is to
increase the volume Vdis involved in the energy
dissipation.

17. Low shear basics
In order to increase the volume over which the velocity gradients are developed, Typhonix’ low
shear valve technology (Typhoon® System) utilizes the hydrocyclone principle of the swirl
motion of the fluids.
The swirl motion in the Typhoon® System
leads to maintaining the higher fluid
velocities created by the flow through the
orifices.
In addition, conical shape of valve’s
downstream volume accelerates the fluids
further in spiral direction, thereby utilizing
this volume for the pressure decrease across
the valve.
Overall pressure reduction happens over a
larger volume, thus reducing the shear forces
developed in the fluid flow.
Low Shear Technology – Control Valves

18. Low shear basics
Typhoon® System performance in simulated and live field conditions has demonstrated that
separation efficiency of downstream separators can be improved tremendously. Results show
that a 50 to 90% improvement of the oil-in-water (OiW) quality downstream a gravity based
separator is possible when replacing a conventional choke valve with the low shear alternative.
The graph below shows the water quality as a function of water cut for both the Typhoon ®
System and a conventional control valve.
Low Shear Technology – Control Valves

19. Low shear basics
The low shear pump technology is highly relevant in produced water applications. High shear
pumps may break down oil droplets in produced water, thereby increasing the difficulty of
separating these droplets from the water.
Following guidelines are usually followed when selecting a low shear pump:
- Reciprocating pumps can be low shear, if they are
equipped with low shear check valves.
- Progressive cavity pumps are usually low shear,
but may require high maintenance.
- Centrifugal pumps tend to break droplets, but is often
considered due to simplicity and low cost.
Typhonix has developed a multistage centrifugal pump with
specially designed impellers and diffusers. This pump exhibits
low shear characteristics and is even capable to increase
average droplet size in a typical produced water application.
Low Shear Technology – Pumps

20. Low shear basics
When fluids move from high to low intensity turbulence regions, the energy dissipation rate
becomes more favorable for droplet-droplet coalescence and respectively - droplet growth.
Physics of the droplet size development inside a pump are complex, and require extensive
numerical analyses to be predicted. The general observation is that both mechanisms of droplet
break-up and droplet coalescence can take place inside the pump housing.
The coalescence process in a turbulent flow consists of two sub-processes: collision of droplets
and drainage of the fluid film between them.
The equation of collision frequency, ωcol , for equally sized droplets is:
This equation determines how often two droplets collide. The collision frequency increases if the
number of droplets, n, the size of droplets, d, or the energy dissipation rate, ε, increases.
Low Shear Technology – Pumps

21. Low shear basics
Pump test results for oil-water mixtures show that the Typhonix multistage centrifugal pump
consistently increases the average droplet size (Dv(50)out) for various process conditions. Additional
conclusions are that the coalescing effect of this pump is increased when the dispersed phase
concentration is increased and the average inlet droplet size is reduced. The coalescing effect is more
pronounced for lighter oils as well.
Low Shear Technology – Pumps

22. Low shear basics
Low shear technologies aim to reduce level of emulsification
in petroleum flows. Less emulsified fluids lead to:
 More effective separation process
 Reduced need for additional amount of chemicals and
heat treatment
 Cleaner oil production
 Increased flexibility in design of produced water
treatment systems
 Reduced problems with recycling of water streams
 Increased field’s lifetime due to reduced OPEX
Benefits of Low Shear Technologies

23. Low shear basics
Low Shear Technologies can
be used in the following
areas in petroleum
production industry:
 Choke valves
 Level control valves
 Produced water
treatment, reject,
drain/slop
 MEG/TEG regeneration
Potential Areas of Application

24. Low shear basics
Thank you for your attention!