IADC/SPE-178842
Pore Pressure Estimation
Using Mechanical Specific Energy (MSE) and Drilling Efficiency
Reza Majidi, Martin Albertin, Nigel Last, BP plc.
Pore Pressure
•
Lower bound of Drilling Window
•
Collapse Pressure (wellbore stability)
•
Fracture Gradient
Pore Pressure Estimation
•
Direct Measurements (permeable formations)
 FPWD, MDT, DST,..
 Kicks, influx and gas data…
•
Indirect estimates (for shales)
 Logs (Sonic, Resistivity, GR,…)
 Drilling Mechanics data (ROP, RPM, WOB, Torque..)
Slide 3
OUTLINE
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Pore pressure and drilling mechanics data
d-exponent method
Mechanical Specific Energy (MSE)
MSE and pore pressure
Drilling Efficiency and Pore pressure Workflow
Field Example
MSE-based Pore Pre. vs dx-base Pore Pressure
Downhole vs. Surface data
Torque @ bit measurement & MSE
IADC/SPE-178842 • Method for Pore Pressure Estimation Using Mechanical Specific Energy and Drilling Efficiency • Reza Majidi
Slide 4
Pore Pressure & Drilling Performance
EFFECT OF DIFFERENTIAL PRESSURE ON DRILLINC RATE,
INDIANA LIMESTONE.
HUGHES TOOL CO.
SPE,AIME 1094-G, 1959
IADC/SPE-178842 • Method for Pore Pressure Estimation Using Mechanical Specific Energy and Drilling Efficiency • Reza Majidi
Slide 5
d-Exponent Method
Bingham drilling model, 1965
Jorden and Shirley in 1966
 ROP

log 

 60 RPM 
dX =
 12 WOB 
log 

d bit


Rehm and McClendon,1971 (corrected for Mud Weight used)
dXc =
p =
ρn
dX
ρw
dXc , n
pn
dXc
IADC/SPE-178842 • Method for Pore Pressure Estimation Using Mechanical Specific Energy and Drilling Efficiency • Reza Majidi
Slide 6
Mechanical Specific Energy (MSE)
Energy required to destroy a unit volume of rock.
MSE =
T
WOB
ROP
RPM
dbit
MSE
480 × T × RPM
d
2
bit
× ROP
+
4 × WOB
πd
Teale (1965)
WOB
2
T
bit
Torque, ft.lb
weight on bit, lbf
rate of penetration, ft/hr
revolutions per minute, min-1
Bit diameter, in
mechanical specific energy,
psi
IADC/SPE-178842 • Method for Pore Pressure Estimation Using Mechanical Specific Energy and Drilling Efficiency • Reza Majidi
Slide 7
Pore Pressure & MSE: Experimental Work
University of Tulsa
Rafatian 2009 & Akbari 2014
IADC/SPE-178842 • Method for Pore Pressure Estimation Using Mechanical Specific Energy and Drilling Efficiency • Reza Majidi
Slide 8
Pore Pressure from MSE (previous work)
J. Cardona et al. (2011)
Texas A&M University (BP sponsored)
IADC/SPE-178842 • Method for Pore Pressure Estimation Using Mechanical Specific Energy and Drilling Efficiency • Reza Majidi
Slide 9
Borehole Environment
Confined Compressive Strength (CCS)
 1 + sin θ 
CCS = UCS + ∆p 

 1 − sin θ 
UCS
θ
∆p
CCS
Unconfined Compressive Strength, psi
angle of Internal friction, Rock property
Confining Pressure, psi
Confined Compressive Strength, psi
Drilling Efficiency:
DE =
Rock Strength (insitu)
Energy required to break
=
CCS
MSE
∆ p = ECD − PP
IADC/SPE-178842 • Method for Pore Pressure Estimation Using Mechanical Specific Energy and Drilling Efficiency • Reza Majidi
Slide 10
Drilling Efficiency (DE) and Pore Pressure
DE =
Rock Strength (insitu)
Energy required to break
DE
DE
p
=
trend
CCS
=
CCS
MSE
p
MSE
∆DE = DEp − DEtrend
= a ϕ nb
Normal compaction porosity trendline
 1 − sin θ 
p = ECD − (DEtrend × MSE − UCS ) × 

 1 + sin θ 
 1 − sin θ 
p = p n + ∆DE × MSE × 

 1 + sin θ 
IADC/SPE-178842 • Method for Pore Pressure Estimation Using Mechanical Specific Energy and Drilling Efficiency • Reza Majidi
Pore Pressure from MSE Work-Flow
Slide 11
IADC/SPE-178842 • Method for Pore Pressure Estimation Using Mechanical Specific Energy and Drilling Efficiency • Reza Majidi
Slide 12
Field Example: Deepwater Gulf of Mexico
Drilling Data
MSE & CCS
Drilling
Efficiency
Pore Pressure data
IADC/SPE-178842 • Method for Pore Pressure Estimation Using Mechanical Specific Energy and Drilling Efficiency • Reza Majidi
Slide 13
Downhole vs. Surface Data
IADC/SPE-178842 • Method for Pore Pressure Estimation Using Mechanical Specific Energy and Drilling Efficiency • Reza Majidi
Slide 14
Torque vs. WOB
× T × RPM
480
d
2
× ROP
+
4 × WOB
πd
2
= MSE
IADC/SPE-178842 • Method for Pore Pressure Estimation Using Mechanical Specific Energy and Drilling Efficiency • Reza Majidi
Slide 15
d-exponent vs. MSE based Pore Pressure
Sonic-based
dXc-based
Sonic-based
MSE-based
IADC/SPE-178842 • Method for Pore Pressure Estimation Using Mechanical Specific Energy and Drilling Efficiency • Reza Majidi
Final Remarks
Slide 16
• The proposed energy based approach (MSE-based) provides new insight into
pore pressure estimation from drilling mechanics data (real-time pp detection @
bit).
• Insitu rock strength was considered in order to obtain pore pressure from MSE
and drilling mechanics data (=>drilling efficiency).
• Downhole data are recommended to be used for pore pressure estimations.
Surface data could be misleading for pore p. estimation.
• Since Torque @ bit dominates the MSE, PP estimation is much more sensitive
to the Torque @ bit rather than WOB.
• The MSE-based Pore Pressure approach has great advantages over the dXc in
terms of reduced subjectivity in the trend line and capturing the physics of
cutting action by taking into account torque and in-situ rock strength.
IADC/SPE-178842 • Method for Pore Pressure Estimation Using Mechanical Specific Energy and Drilling Efficiency • Reza Majidi
Slide 17
Thank You
Questions?