OG 334 Petroleum Production
Well Deliverability
Lecture 7
23/01/2020
Fulmence Kaborogo CME
1
Well Deliverability
▪ Refers to rate of stable flow that can be
expected from a particular well at specified
bottom-hole flowing pressure and well head
pressure, sometimes called equilibrium rate
▪ It is determined by the combining the well
inflow performance relationship (available
pressure curve) and tubing performance
relationship (required pressure curve)
▪ Equilibrium flow rate is obtained at the point
to which the TPR and IPR curves intersect.
23/01/2020
Fulmence Kaborogo CME
2
Well Deliverability
▪ When oil flows to the surface without artificial
assistance this is known as natural flow
▪ The intersection of TPR and IPR curves for
such flow is called natural flow point.
▪ The equilibrium rate at natural flow is called
natural flow rate
▪ The intersection point for IPR and TPR could
be determined analytically using the graphs
or by trial and error through nodal analysis
techniques
23/01/2020
Fulmence Kaborogo CME
3
Well Deliverability
Intersection point defines the operating flowing
bottom hole pressure and expected production
rate
23/01/2020
Fulmence Kaborogo CME
4
Well Deliverability
For multiphase flow, there may be two points of
intersection stable flow point (right) and unstable flow
point (left)
23/01/2020
Fulmence Kaborogo CME
5
Well Deliverability
▪ If the target rate is less than an equilibrium rate, a
choke has to be installed and a pump is required if
the target rate is higher than an equilibrium
rate(artificial lift)
Pwf
Pwf
Pump
choke
qtarget
23/01/2020
qeq
Fulmence Kaborogo CME
qtarget
6
Well Deliverability
▪ The equilibrium point could change with changes
in reservoir depletion depending on variation of
IPR and TPR resulting from changes in reservoir
pressure and flow characteristics
▪ IPR declines with time as the result of reservoir
depletion.
▪ Other sources may be due to near the wellbore
damage,
reduced
permeability
due
to
multiphase and or fines migration
▪ It could, well pumping (pump lift) and changes of
well conditions can be improved by stimulations
such as acidizing and fracturing
23/01/2020
Fulmence Kaborogo CME
7
Effect of Changing IPR
▪ The equilibrium rate decreases with decline in IPR
23/01/2020
Fulmence Kaborogo CME
8
Effect of Changing Pwh on TPR
▪ TPR curve would be affected by changing well
head pressure (Pwh) through choke opening
manipulation thus affecting the equilibrium rate
▪ Increasing the choke opening results to reduction
in wellhead pressure leading to increase natural
flow rate (TPR curve shifts down ward)
▪ Maximum equilibrium rate is obtained at
wellhead pressure equal the atmospheric
pressure
▪ Reducing the choke opening shifts the TPR curve
upwards resulting to decrease in equilibrium rate
23/01/2020
Fulmence Kaborogo CME
9
Effect of Changing Pwh on TPR
▪ The equilibrium rate decreases with increase in
wellhead pressure
23/01/2020
Fulmence Kaborogo CME
10
Effect of GLR on TPR
▪ Changes of gas liquid ratio, affects the the
frictional and hydrostatic pressure losses
components in the tubing.
▪ It could be achieved by injecting gas from the
surface to lower sections of the tubing (gas lift)
▪ Increasing GRL lightens the mixture density and
therefore less pressure drop due to hydrostatic
thus shifting the TPR curve upward and to the
right leading to increase natural flow rate
▪ Larger quantities of gas would result in large
pressure losses due to friction
23/01/2020
Fulmence Kaborogo CME
11
Effect of GRL on TPR
▪ With continued gas injection reaches a maximum
GRL (critical gas liquid ratio) at which the trend
becomes reversed (natural flow rate decreases)
▪ Thus an optimal gas injection rate is required.
23/01/2020
Fulmence Kaborogo CME
12
Effect of Tubing Diameter on TPR
▪ Increasing tubing dimeter increases the rate of
natural until a critical diameter is reached
▪ For higher diameters, the rate will decrease due
change of pressure loss dominance from
frictional to gravity and to hold up forces that
occur with increasing pipe dimeter
▪ Natural flow is the primary criterion for used to
choose the tubing size, however price,
availability, mechanical considerations and future
production characteristics have to be considered
as well (optimization)
23/01/2020
Fulmence Kaborogo CME
13
Effect of Tubing Diameter on TPR
▪Natural flow rate increase with increasing dimeter
until a critical diameter is reached
23/01/2020
Fulmence Kaborogo CME
14
IPR and VLP for Two phase
▪ For two phases reservoirs both IPR and
VLP changes with time as the reservoir pressure
decline since GRL will be varying as well.
▪ The composite effect is that the decline in the
well producing rate will be slower that for single
phase as the VLP curve will shift downwards due
to increased GRL at new depletion (P2).
▪ At later times, with depletion the GRL becomes
higher the process will be reversed
▪ Ultimately, the gap between the corresponding
VLP curves is reduced and they are likely to
overlap.
23/01/2020
Fulmence Kaborogo CME
15
IPR and VLP for Two phase
Variation of IPR and VLP wit depletion for two phase
reservoirs
23/01/2020
Fulmence Kaborogo CME
16
Class example
A decision has to be made whether to use 3 in or 4 in Internal
diameter tubing for a well with the flowing conditions;
• Steady state flow
• Initial pressure
2500 psi
• PI
2.0 STB/psi
• Bubble point pressure 1500 psi
• Depth (TVD)
5000 ft
• Required THP
300 psi
• GOR
200 SCF/bbl
i.
Calculate the flow capacity of the well for 3 in. and 4 in. ID
tubing using the attached gradient curves(1000,2000 and
3000 bbls/day)
ii. Comment on the general sizing of the available tubing
strings
23/01/2020
Fulmence Kaborogo CME
17
23/01/2020
Fulmence Kaborogo CME
18
23/01/2020
Fulmence Kaborogo CME
19
23/01/2020
Fulmence Kaborogo CME
20
23/01/2020
Fulmence Kaborogo CME
21
23/01/2020
Fulmence Kaborogo CME
22
Solution
23/01/2020
Fulmence Kaborogo CME
23
Solution
23/01/2020
Fulmence Kaborogo CME
24
5000 ft
23/01/2020
Fulmence Kaborogo CME
25
Solution
23/01/2020
Fulmence Kaborogo CME
26
Solution
• Summary;
• Tubing size (in.)
3
4
Production rate (b/d)
1500
1700
• Because, 4 in pipe gives higher rate has to be
selected.
✓ What is the additional cost of the 4 in diameter as
compared to 3 in pipe?
✓ what is the extra income earnt by installing 4 in
compared to 3 in pipe? Is it enough to cover the
additional cots ?
23/01/2020
Fulmence Kaborogo CME
27
23/01/2020
Fulmence Kaborogo CME
28