This document discusses factors that affect vertical lift performance (VLP) in oil and gas wells. It explains that VLP is determined by calculating pressure losses versus production rate. The main factors that influence VLP are choke size, gas-liquid ratio, and tubing diameter. Changing the choke opening affects wellhead pressure and shifts the VLP curve. Increasing the gas-liquid ratio can initially improve VLP up to a point, by reducing density. Larger tubing diameters also initially increase flow rates and VLP, but beyond a critical size, pressure losses from friction and acceleration dominate.

1. Determination of VLP by choke and
bottom hole parameters
DEPARTMENT OF PETROLEUM AND NATURAL GAS
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Presenter: Jaleel Ahmed K14PG48
Assigned by: Engr Sohail Ahmed Shaikh
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2. Vertical lift performance
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The pressure drop experienced in lifting reservoir fluids to the surface is one
of the main factors affecting well deliverability.
As much as 80% of the total pressure loss in a flowing well may occur in lifting
the reservoir fluid to the surface.
Wellbore flow performance relates to estimating the pressure-rate
relationship in the wellbore as the reservoir fluids move to the surface
through the tubulars.

3. Vertical Lift Performance (VLP)
It is a plot of the pressure losses vs. production rate in the system.
Tubing performance is the term used to describe Outflow performance. It is
also called Vertical Lift Performance.
Tubing Performance looks at optimizing/minimizing pressure losses at lowest
life cycle cost.
By minimizing pressure drop, we maximize production.
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4. Theory Of Vertical Lift
In order to flow from the bottom of the well to
surface, fluid needs to overcome several
pressure drops.
1. Hydrostatic losses- Due to the density of the
fluid column
2. Frictional losses- Due to the viscous drag
3. Kinetic losses- Due to the expansion and
contraction of the fluid and the change in the
cross-sectional area, which leads to
acceleration and deceleration of the fluid
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5. Procedure:
We either fix the wellhead or bottom hole flowing pressure at a given rate.
The pressure drop along the tubing can be calculated by charts or correlations.
The resulting flowing pressure at the other end of the tubing can then be determined.
The resulting relationship between bottom hole flowing pressure and production rate is
called Tubing Performance Relationship (TPR), and it is valid only for the specified wellhead
pressure.
Other names include:
 Vertical Lift Performance
 Wellbore Flow Performance
 Outflow Performance Relation
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6. Factors Affecting the VLP
Choke
Gas liquid ratio
Tubing size or diameter
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7. choke
The choke creates the flow restriction by offering a restricted flow path for
the fluid to pass through.
Generally installed adjacent to x-mass tree on the surface.
Chokes hold a backpressure on a flowing well to make The back-pressure
(caused by the chokes or other restrictions in the flow line) increases the
bottom hole flowing pressure.
Increasing the bottom-hole flowing pressure decreases the pressure drop
from the reservoir to the wellbore (pressure drawdown). Thus, increasing
the back-pressure in the wellbore decreases the flow rate from the reservoir.
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8. Effect On TPR
Decreasing the well head pressure by increasing choke opening will usually shift TPR curve
downward to lower intake pressure.
If the well head pressure is reduced to minimum then the well produce at its maximum.
Increasing well head pressure by decreasing choke opening will shift the TPR curve upward
resulting decrease in rate
If the well head pressure increase beyond the limit then well will stop producing
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10. Gas/liquid ratio
The effect of changing gas liquid ratio is not as straightforward as case of changing well head
pressure.
It has different effects on two components pressure loss in tubing-fraction and hydrostatic.
Increase in gas liquid ratio lightens the mixture density and there fore reduces the pressure due
to hydrostatic pressure.
Larger quantities of gas will however result in larger pressure losses due to fraction.
An increase in gas liquid ratio tend to shift TPR curve to upward and right, the result is increase in
natural flow and optimized vertical lift performance.
The trend continues up to a certain gas liquid ratio, where the trend is reversed
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12. Tubing size or diameter
The effect of tubing diameter on vertical lift performance or natural flow is similar
to the effect of gas liquid ratio.
Generally increase in tubing diameter increase the rate of flow, hence improve lift
performance.
Flow rate increase until a critical a critical diameter is reached.
For higher diameters rate will decrease, this is due to change of dominance in
pressure loss from fraction to gravity and holdup forces that increase with
increasing pipe diameter.
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13. Tubing diameter
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