Application of Energy Equation to Optimize ROP and
Reduce Formation Damage
By
Eng.\ Mohamed Hosin Mohamed El-Neiri
A Thesis Submitted to the Faculty of Engineering Cairo University
In The Partial Fulfillment of the Requirements for the Degree of
MASTER OF SCIENCE
IN
PETROLEUM ENGINEERING
Faculty of Engineering, Cairo University,
Giza, Egypt.
2014
I
Application of Energy Equation to Optimize ROP and
Reduce Formation Damage
By
Eng.\ Mohamed Hosin Mohamed El-Neiri
A Thesis Submitted to the Faculty of Engineering Cairo University
In The Partial Fulfillment of the Requirements for the Degree of
MASTER OF SCIENCE
IN
PETROLEUM ENGINEERING
Under the Supervision of
Prof. Dr. Abdel Sattar Abdel Hamid
Dahab
DR. Abdel Aziz Mohamed Ali Abdel
Aziz
Professor of Petroleum Engineering
Assist. Professor of Petroleum Engineering
Cairo University.
Cairo University.
Faculty of Engineering, Cairo University,
Giza, Egypt.
2014
II
Application of Energy Equation to Optimize ROP and
Reduce Formation Damage
By
Eng.\ Mohamed Hosin Mohamed El-Neiri
A Thesis Submitted to the Faculty of Engineering Cairo University
In The Partial Fulfillment of the Requirements for the Degree of
MASTER OF SCIENCE
IN
PETROLEUM ENGINEERING
Approved by the Examining Committee:
____________________________________________________________________________
Prof. Dr. Abdel Sattar Abdel Hamid Dahab, Advisor
______________________________________________________________________________
Dr. Abdel Aziz Mohamed Abdel Aziz, Advisor
______________________________________________________________________________
Prof. Dr. Mohamed Rshad Taha, Member
______________________________________________________________________________
Eng. Hisham Mohamed Bhaa El-Din Al Attar, Member
Faculty of Engineering, Cairo University,
Giza, Egypt.
2014
III
Engineer:
Date of Birth:
Nationality:
E-mail:
Phone:
Address:
Registration Date:
Awarding Date:
Degree:
Department:
Engineering
Mohamed Hosin Mohamed El Neiri
3/ 5 / 1988
Egyptian
moh_eln@yahoo.com
01112271003
202- Mubarak project – 3rd Settlement
1 / 10 / 2011
/ /4102
Master of Science
Mining, Petroleum, and Metallurgy
Supervisors:
Prof. Dr. Abdel Sattar Abdel Hameed Dahab.
Dr.
Abdel Aziz M. Ali Abdel Aziz
Examiners:
Prof. Dr. Abdel Sattar Abdel Hameed Dahab.
Prof. Dr. Mohamed Rshad Taha
Eng. Hisham Mohamed Bhaa El-Din Al Attar
(Chairman of Mansoura Petroleum Company)
Title of Thesis:
Application of Energy Equation to Optimize ROP and Reduce Formation Damage
Key Words:
Under balanced drilling, Increasing ROP, Reducing formation damage
Summary:
Underbalanced drilling has many advantages such as high ROP (may reach up to ten times), early
information about reservoir, eliminating or minimizing the risk of differential stuck and loss of circulation
and avoiding formation damage. However, UBD is expensive and complicated. It isn’t applicable in certain
cases such as pressurized shale. On the other hand, over balanced Drilling is cheaper with good control
over formation fluids but with lower ROP, Losses, differential stuck possibilities and formation damage.
A new technique can combine some advantages of UBD while keeping OB by using the general energy
equation. By using modified Bernoulli equation, an under balanced zone below the bit by could be created
by setting the proper nozzle orientation and size. This is simply done by keeping the drilling fluid velocity
as high as calculated and predetermined to create the pressure drop required. This drop in pressure is
controlled by Nozzles Orientation, Nozzle Size and Mud flow rate. The whole well except the zone at the
bit will be OB. The pressure drop made is by mud velocity and this velocity will drop as the mud enters the
wider annular space above the bit. This velocity drop will result in increased pressure to the OB values.
The suggested method or technique is made to drill at the UBD ROP while the well is overbalanced. Thus a
controlled degree of UB and high ROP of UBD could be achieved. This technique enables us to keep full
control on formation fluid. Formation fluids are controlled by the ordinary mud in the well. The only UB
zone is that below the bit while drilling. If circulation is stopped or the bit is off bottom the whole well is
OB. The new technique also enables us to determine the reservoir fluid types and the reservoir permeability
while drilling. By varying the degree of UB we achieve various values of Draw Down and record the
corresponding value of gain of each fluid with time. Then determining permeability and other information
is available.
Formation damage is reduced considerably in this technique. Faster ROP means lowering Open Hole Time
and this will lead to lower formation damage. In addition, this technique is the most economic way to get
all these benefits of UBD and OBD.
Acknowledgement
Thank ALLAH, The Almighty, for giving me the ability and power to complete
this study.
I greatly appreciate all those who have helped me accomplishing it, the
Supervisors; Prof. Dr. Abdel Sattar Abdel Hamid Dahab and Dr. Abdel Aziz
Mohamed Ali Abdel Aziz, staff of Petroleum Engineering, Faculty of
Engineering for their Supervision during the various phases of this study.
Deep thanks are due to Eng. Hisham Mohamed Bhaa El-Din Al Attar (chairman
of Mansoura Petroleum Company) and Eng. Mohamed El Naggar (Operation
general manager, Mansoura Petroleum Company) for their continuous support
that helps completing this thesis.
I would like to thank everyone whom I learned from at anytime and
anywhere for his/her efforts which I will always be unable to thank for.
Last but not least, thanks go for my parents and my wife for their fruitful
assistance during this work.
IV
Table of Contents
Page
Acknowledgement…………….………………………………………..
Table of Contents……………………………..…...…………………..
List of Tables……………………...…………..…………………..…..
List of Figures…………………………………………………………
List of Symbols………………………………………………………..
Abstract………………………………………………………………..
Chapter 1: Introduction………………………………………………..
Chapter 2: Literature Review……………………………….…………
2. The principles governing fluids in motion……………..………..………..
2.1. Acceleration of a Fluid Particle…………………....……………….
2.2. The Continuity equation…………………...….……………............
2.3. Bernoulli’s equation………………..……………..………………...
2.4. General Energy Equation for Steady Flow of any Fluid……………
2.5. The momentum equation for Steady Flow …………………………
2.6. Applications of the Bernoulli Equation…………..…………………
Chapter 3: Introduction to UBD technique…………….……..……………
3.1. Advantages and Disadvantages of UBD………………………........
3.1.1. Advantages………..…………..………...………………….
3.1.2. Disadvantages………………...…………………………….
3.2. Barriers to UB……………………………………......……………..
3.3. Good UBD candidates ………….………………….………….…...
3.4. UBD Fluid Types……………………………………..…………….
3.4.1. Liquid Drilling Fluids…………………………………...….
3.4.2. Gaseous Drilling Fluids……………….…………………....
3.4.3. Mist Drilling………………………………………………..
3.4.4. Foam Drilling…………………………...………………….
3.4.5. Aerated Fluid Drilling……………………………………...
3.5. Special surface equipment …..………..……………………………
3.6. Downhole Equipment……….………………..…………………….
A. Bits…………………….……………………………….
B. Downhole Motors………………………….…………..
C. MWD’s…………………….……...……………………
D. Float Valves……………………………………………
3.7. Drilling Engineering…………………..…….………….…………..
3.7.1. Fluid mechanics…………………….…………….………..
3.7.2. Hole Cleaning………….…………….……………………..
3.7.3. Torque & Drag…………………………..………..………..
3.7.4. Hole Stability………………….….……….………………..
III
IV
VI
VII
XI
XII
1
5
5
5
7
9
11
13
14
18
19
19
19
20
20
21
21
21
24
24
24
25
26
26
26
26
26
27
27
28
29
29
Chapter 4: Failure mechanisms and factors affecting rate of
penetration (ROP)……………………………………………………………… 31
4.1. Failure mechanisms of rocks……………………………………….. 31
V
4.2. Factors affecting ROP………………………………………………
4.2.1. Properties of drilling fluid…………………………………..
4.2.2. Formation characteristics…………………………………...
4.2.3. Type of bit…………………………………………………..
4.2.4. Tooth wear………………………………………………….
4.2.5. Operating conditions (WOB and RPM)……………………
4.2.6. Hydraulics…………………………………………………..
Chapter 5: The proposed technique ………………………………………....
5.1. Introduction…………..……………….…………………………….
5.2. The new technique….………………………………………………
5.2.1. Nozzle orientation…………….…………………...………..
5.5.1.1. Ordinary nozzles orientation………………….....
5.5.1.2. Required nozzles orientation……………….…..
5.5.1.3 Examples of required nozzle orientation…………
5.2.2. Losses calculations…………………….……………...……
5.2.2.1. Pressure drop across the bit……………………....
5.2.3. Hole cleaning…………..….….………….…………………
23.3.1. Slip velocity……………………………………….
5.2.4. Permeability and formation fluids………………………….
5.5.4.1. Permeability (absolute, effective and relative) ….
5.5.4.2. What is the new method? ……………………….
5.2.5. Well control considerations…………………..…………….
5.2.6. Effects on some troublesome zones………………………..
5.2.7. Factors affecting pressure drop……..………………………
5.2.7.1. Effect of mud density……………………………
5.2.7.2. Effect of surface pressure………………………..
5.2.7.3. Effect of nozzle velocity…………………………
5.2.7.4. Effect of nozzle size variation…………………...
5.2.8. Multiple of ROP achieved due to pressure drop……………
5.2.9. Economics……………….……………….………...………
4.2.10. Comparison of over balanced drilling (OBD), under
balanced drilling (UBD) and the proposed new technique …….....
Conclusion…………………………………………………………….
References……………………………………………………………………….
Appendix A……………………………………………………………
VI
34
34
39
39
39
40
41
43
43
45
53
53
55
57
60
63
64
64
68
68
75
79
80
81
81
82
83
84
86
92
144
147
148
150
List of Tables
No.
5.1
5.2
5.3
5.4
5.5
5.6
5.7
5.8
5.9
5.10
5.11
5.12
5.13
5.14
5.15
5.16
5.17
5.18
5.19
5.20
5.21
Title
Effect of mud density………………………………….………....
Effect of surface pressure……………………………...………...
Effect of nozzle velocity………………………………………....
Effect of nozzle size variation……………………………………
Typical items used in drilling cost/day ..………………………...
Cost of a drilling day with mud motor …………………………..
Cost of drilling day with Autotrack or Geopilot……....................
Well 1 data (days and costs vs depth) …………………………..
Days saved with various ROP multiples that may be achieved for
well 1……………………………………………………………..
Costs saved with various ROP multiples that may be achieved
for well 1…………………………………………………………
Well 2 data ………………………………………………………
Days saved with various ROP multiples that may be achieved for
well 2……………………………………………………………..
Costs saved with various ROP multiples that may be achieved
for well 2…………………………………………………………
Well 3 data ………………………………………………………
Days saved with various ROP multiples that may be achieved for
well 3……………………………………………………………..
Costs saved with various ROP multiples that may be achieved
for well 3…………………………………………………………
Well 4 data ………………………………………………………
Days saved with various ROP multiples that may be achieved for
well 4……………………………………………………………..
Costs saved with various ROP multiples that may be achieved
for well 4…………………………………………………………
Total days, savings and % savings (total and dry hole) for the
four wells…………………………………………………………
Total costs, savings and % savings (total and dry hole) for the
four wells …………………………………………...……………
VII
Page
81
83
84
85
92
93
93
95
98
100
106
109
111
116
119
121
126
129
131
136
137
List of Figures
No.
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
2.10
Title
Mass flow rate into a control volume...……………………
Stream filament……………...…………………………….
Fluid element chosen………………………………………
Energy transformation for an incompressible fluid………..
Forces on air plane wing and on a bird……………………
Pressure variation above and below the wing……………..
Race car spoiler………...………………………………….
Air blown between two pieces of paper…………………...
stagnation point……………………………………………
Streamlines around a blunt body…………………………..
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
3.10
Drilling window…………………………………………...
Fluid density ranges…………..…………………………..
Air drilling (Dusting). …………………………………….
Flow Regimes……………………………………………..
Burnt pipes due to downhole fire ..………………………..
4.1
The apparatus used to study penetration of bit tooth under
various conditions…………………………………………
Crater mechanism………………………………………….
Force required for cuttings displacement for various
differential pressures………………………………………
Effect of overbalance on ROP for Brea sandstone
(clay/water mud, 1.25” rolling cutter bit)………………….
Effect of overbalance on ROP for Indiana limestone
(clay/water mud, 1.25” rolling cutter bit)………………….
Relation between effective overbalance and rock
permeability at 32 rpm…………………………………….
Effect of overbalance on ROP for various bit types……….
4.2
4.3
4.4
4.5
4.6
4.7
Page
7
7
9
12
14
15
15
15
16
16
18
21
22
22
23
The flammable zone for Methane-Oxygen-Nitrogen mixture…. 23
Foam and Mist…………………………………………… 24
Float Valves………………………………………………. 27
Hole cleaning curve……………………………………….. 28
Hydrostatic head and related problems…………………… 30
VIII
32
33
34
36
36
36
37
4.8
4.9
4.10
4.11
4.12
4.13
4.14
4.15
5.1
5.2
5.3
5.4
5.5
5.6
5.7
5.8
5.9
5.10
5.11
5.12
5.13
5.14
5.15
5.16
5.17
5.18
5.19
5.20
5.21
5.22
5.23
ROP as a function of overbalance (Colton sandstone)…….
Effect of overbalance on ROP for shale (field
measurement)……………………………………………...
Relation between ROP and log(R/R0)……………………..
Relation between ROB and WOB…………………………
Relation between ROB and rotary speed………………….
Relationship between required level of hydraulics and
ROP………………………………………………………..
Experimental data for the effect of bit Reynolds number
on ROP (for various WOB)………………………………..
Effect of hydraulics on ROP (Mancos shale under bottom
hole conditions)……………………………………………
37
Pressure drops as velocity increases………………………
Velocity variation with cross-sectional area………………
Tank discharging into a tapered pipe line…………………
Conventional nozzle orientation…………………………..
Mudpick I nozzle orientation……………………………...
Mudpick II nozzle orientation……………………………..
Nozzle orientations………………………………………..
Venturi and Pitot effects…………………………………..
Example of required flow direction……………………….
Conventional PDC profiles………………………………..
Example 1 of extended bit nozzle required direction of
flow………………………………………………………...
Example 2 of extended bit nozzle fluid required flow
direction……………………………………………………
Intersection of system requirements and pump output is
the operating point…………………………………………
Pump characteristic curve…………………………………
Pump efficiencies at various outputs………………………
Various types of fluids…………………………………….
Schematic diagram of circulating system…………………
A solid ball falling in a liquid……………………………...
Fluid flow through a porous media………………………..
Pressure distribution in reservoir…………………………..
Radial flow model…………………………………………
Relative permeability curve (function of saturation)……...
Summation of relative permeabilities is smaller than one
due to mutual friction between the fluids…………………
44
45
45
53
54
54
55
56
57
58
IX
38
38
40
40
41
41
42
58
59
60
60
61
61
62
65
68
70
70
72
73
5.24
5.25
5.26
5.27
5.28
5.29
5.30
5.31
5.32
5.33
5.34
5.35
5.36
5.37
5.38
5.39
5.40
5.41
5.42
5.43
5.44
5.45
5.46
5.47
5.48
5.49
5.50
5.51
5.52
5.53
5.54
5.55
5.56
5.57
Permeability isn’t equal in drainage and imbibition due to
differences in wetability of fluids entering and exiting……
h depends on bit profile……………………………………
Effect of mud density……………………………………...
Effect of surface pressure………………………………….
Effect of nozzle velocity…………………………………..
Effect of nozzle size variation…………………………….
Effect of differential pressure on ROP…………………….
Depth vs. Days for well 1………………..…….………….
Depth vs. Cost for well 1…………….…………………….
Depth vs. Days for various ROP multiples for well 1…….
Depth vs. Cost for various ROP multiples for well 1……..
Total days for various ROPs for well 1…………………....
Total costs for various ROPs for well 1…………………...
Total days saved & % of time saved for various ROPs for
well 1………………………………………………………
Dry hole time savings &% of time savings for various
ROPs for well 1……………………………………………
Total cost savings & savings % for various ROPs for well 1..
Dry hole cost savings & savings % for various ROPs for
well 1
Depth vs. Days for well 2………………..…….………….
Depth vs. Cost for well 2…………….…………………….
Depth vs. Days for various ROP multiples for well 2…….
Depth vs. Cost for various ROP multiples for well 2……..
Total days for various ROPs for well 2…………………....
Total costs for various ROPs for well 2…………………...
Total days saved & % of time saved for various ROPs for
well 2………………………………………………………
Dry hole time savings &% of time savings for various
ROPs for well 2……………………………………………
Total cost savings & savings % for various ROPs for well 2..
Dry hole cost savings & savings % for various ROPs for
well 2………………………………………………………
Depth vs. Days for well 3………………..…….………….
Depth vs. Cost for well 3…………….…………………….
Depth vs. Days for various ROP multiples for well 3…….
Depth vs. Cost for various ROP multiples for well 3……..
Total days for various ROPs for well 3…………………....
Total costs for various ROPs for well 3…………………...
Total days saved & % of time saved for various ROPs for
X
73
77
82
83
84
85
88
96
97
99
101
102
102
103
104
104
105
107
108
110
112
113
113
114
114
115
115
117
118
120
122
123
123
124
5.58
5.59
5.60
5.61
5.62
5.63
5.64
5.65
5.66
5.67
5.68
5.69
5.70
5.71
5.72
5.73
5.74
5.75
5.76
5.77
5.78
5.79
5.80
well 3………………………………………………………
Dry hole time savings &% of time savings for various
ROPs for well 3……………………………………………
Total cost savings & savings % for various ROPs for well 3..
Dry hole cost savings & savings % for various ROPs for
well 3………………………………………………………
Depth vs. Days for well 4………………..…….………….
Depth vs. Cost for well 4…………….…………………….
Depth vs. Days for various ROP multiples for well 4…….
Depth vs. Cost for various ROP multiples for well 4……..
Total days for various ROPs for well 4…………………....
Total costs for various ROPs for well 4…………………...
Total days saved & % of time saved for various ROPs for
well 4………………………………………………………
Dry hole time savings &% of time savings for various
ROPs for well 4……………………………………………
Total cost savings & savings % for various ROPs for well 4..
Dry hole cost savings & savings % for various ROPs for
well 4………………………………………………………
Total days for the four wells………………………………
Total saved days for the four wells………………………..
Percentage of total days saved for the four wells………….
Dry hole days saved for the four wells…………………….
Percentage of dry hole days saved for the four wells……...
Total costs for the four wells………………………………
Total costs saved for the four wells………………………..
Percentage of total costs saved for the four wells…………
Dry hole costs saved for the four wells……………………
Percentage of dry hole costs saved for the four wells……..
XI
124
125
125
127
128
130
132
133
133
134
134
135
135
138
138
139
139
140
140
141
141
142
142
List of Symbols
ρ:
A:
v:
v:
Q:
P:
W:
Θ:
g:
z:
t:
s:
ΔQ:
ΔE:
ΔW:
hf :
H:
D:
F:
Pe:
Pwf:
re:
rw:
µ:
h:
m:
γ:
V:
K:
OBD :
UBD :
ROP :
Density
Cross-sectional area
Velocity
Mean velocity
Volumetric flow rate
Pressure
Weight
Angle to horizontal plane
Gravitational acceleration
Elevation to reference plane
Time
Distance
Heat added to the system
The system internal energy
Work done by the system
Friction head loss
Height or Depth
Diameter
Force
Mass flow rate
Pressure at reservoir boundary
Bottom hole pressure
Drainage radius
Well radius
Viscosity
Thickness
Line slope
Specific gravity (=ρ*g)
Volume
Permeability
Overbalanced drilling
Underbalanced drilling
Rate of penetration
XII
Abstract
Underbalanced drilling has many advantages such as high ROP (may reach up to ten
times), early information about reservoir, eliminating or minimizing the risk of
differential stuck and loss of circulation and avoiding formation damage. However,
UBD is expensive and complicated. It isn’t applicable in certain cases such as
pressurized shale. On the other hand, over balanced Drilling is cheaper with good
control over formation fluids but with lower ROP, Losses, differential stuck
possibilities and formation damage.
A new technique can combine some advantages of UBD while keeping OB by using the
general energy equation. By using modified Bernoulli equation, an under balanced zone
below the bit by could be created by setting the proper nozzle orientation and size. This
is simply done by keeping the drilling fluid velocity as high as calculated and
predetermined to create the pressure drop required. This drop in pressure is controlled
by Nozzles Orientation, Nozzle Size and Mud flow rate. The whole well except the
zone at the bit will be OB. The pressure drop made is by mud velocity and this velocity
will drop as the mud enters the wider annular space above the bit. This velocity drop
will result in increased pressure to the OB values.
The suggested method or technique is made to drill at the UBD ROP while the well is
overbalanced. Thus a controlled degree of UB and high ROP of UBD could be
achieved. This technique enables us to keep full control on formation fluid. Formation
fluids are controlled by the ordinary mud in the well. The only UB zone is that below
the bit while drilling. If circulation is stopped or the bit is off bottom the whole well is
OB. The new technique also enables us to determine the reservoir fluid types and the
reservoir permeability while drilling. By varying the degree of UB we achieve various
values of Draw Down and record the corresponding value of gain of each fluid with
time. Then determining permeability and other information is available.
Formation damage is reduced considerably in this technique. Faster ROP means
lowering Open Hole Time and this will lead to lower formation damage. In addition,
this technique is the most economic way to get all these benefits of UBD and OBD.
XIII
Chapter 1
Introduction
Underbalanced drilling has great advantages including high rate of penetration
(ROP), minimal formation damage and provide early information about the
reservoir. However it requires expensive tools, expert personnel and is generally
complicated processes. Furthermore, it is not always applicable for all reservoir
conditions such as pressurized shale formations.
On the other hand, overbalanced drilling is cheaper, simpler and enables good
control over formation fluids. Hole stability problems are easily solved in
overbalanced drilling, but formation damage and lower rate of penetration are the
main disadvantages in overbalanced drilling.
In this thesis we introduce a new technique to combine the advantages of both
underbalanced drilling and over balanced drilling techniques. In the new
technique presented in this thesis underbalanced zone is created just below and
around the bit while the rest of the hole is overbalanced. These conditions can be
achieved by drilling fluid velocity as discussed in details in the present research
work.
Using the basic laws of mass and energy conservation we can achieve an
underbalanced zone below the bit while the rest of well falls within over balanced
conditions. Thus higher rate of penetration at low cost can be achieved. Reservoir
fluid sampling may be achieved easily at low cost while drilling. Extended bit life
is also an expected profit of this technique. More measurements to determine the
permeability and reservoir pressure may be done while drilling. Formation
damage will be reduced by this technique because the open hole time is reduced
due to higher ROP. Even during the following over balanced stage the formation
damage is expected to be reduced by this technique because of the open hole time
is significantly decreased by the higher ROP.
1