gas field engineering - gas well performance
TRANSCRIPT
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GAS FIELD ENGINEERING
Gas Well Performance
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CONTENTS
6.1 Gas Well Performance
6.2 Static Bottom-hole Pressure(static BHP)
6.3 Flowing Bottom-hole Pressure(flowing BHP)
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LESSON LEARNING OUTCOME
At the end of the session, students should be able to:
Determine static bottom-hole pressure(static BHP) usingdifferent methods
Determine flowing bottom-hole pressure(flowing BHP) using
different methods
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Gas Well Performance
Figure (6.1) Gas Production Schematic
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Gas Well Performance
Deliverability
Theability of reservoirto deliver a certain quantity
of gasdependsupon:
1.inflow performance relationship(IPR)
2. flowing bottom-hole pressure(FBHP)
Well & Facilities Performance
Flowing bottom-hole pressuredependsupon:
1. Separator pressure
2. Configuration of the piping system
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Gas Well Performance
These conditions can be expressed as:
(8.1)
(8.2)
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Thebottom hole pressure (BHP) must be known in order to
predictthe productivity or absolute open flow potential(AOF)of
gas wells.
Preferred method is aBHP gauge(down-hole pressure gauge).
However,BHPcan be estimated if following is known: well head pressure,
well head temperature,
formation temperature,
well depth
gas specific gravity
Bottom-Hole Pressures (BHP)
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Basic Energy Equation when no flow
For a static gas column, the basic energy balance is:
Further assume that the local g equals
the g constant (g = gc) and re-arrange:
OR
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Static BHP for Slanted Wells
For slanted wells as shown below, total
length L and depth Z are related:
Relates Inclination to
Pipe Length & angle
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BHP for slanted wells
In differential form:
Where dZ is the change in the elevation in the upward
direction and dL is positive upwards.
-- Assuming a single-phase fluid that obeys the real gas
equation of state (EOS), gas density can be expressed as a
function of pressure:
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BHP for slanted wells
Combining the equations yields:
Combine with: AND
To get:
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Root of all methods for BHSP calc.
Relates the change in wellbore pressure
as a function of depth and gas density.
Derived from Energy Balance
Assumed static conditions (no kinetic
energy, friction loss or work done)
Replaced density with EOS (equation of
state)
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Average Temp. & z-Factor Method
Both gas density & z factor are p & T
dependent and change with well depth
Solving the root equation is thus difficult
If T & z-factor are assumed constant then
a solution can be obtained as follows:
whose solution is
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Solution Technique
Because depends on p which is unknown,
solution requires an iterative process.
1. Assume a value of BHSP, , A good
guess can be obtained from:
2. Compute avg pressure & temperature & use it
to find avg z-factor
3. Calculate with the earlier equation.
4. Iterate on steps 2 through 4 until converges.
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Example for Class Participation
Since depends on p which is unknown,
solution requires an iterative process.
1. Assume a value of BHSP, . A good
guess can be obtained from:
2. Compute avg pressure & temperature
& use it to find avg z-factor
3. Calculate with the earlier equation.
4. Iterate on steps 2 to 4 until converges.
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Example Solution
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Example Solution
Because of the simplifying assumptions made in its
development, this method is not accurate for deeper
wells and alternate methods should be used.
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Q & A
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Thank You