Production Logging Kappa
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© KAPPA 2011
1
Production Logging
1. Introduction
© KAPPA 2011
2
Introduction
•
What is Production Logging (PL) ?
•
PL applications
•
The typical well
•
The typical PL tool string
•
The PL operation
•
The PL job
•
Factors affecting well production
© KAPPA 2011
3
What is PL?
Production logging encompasses a number of well logging techniques run on completed injection or production wells, with the goal being to evaluate the well itself or the reservoir performance. SPE Monograph 14, “Production Logging”, Hill A.D.
The purpose of production logging is to provide the most detailed knowledge possible of the nature and behavior of the fluids in the well during production or injection” Production Log Interpretation, Schlumberger
© KAPPA 2011
4
What is PL?
•
Series of measurements that (hopefully…) will allow the determination of the fluid type and rate in the wellbore as a function of depth
•
Downhole and (mostly) continuous
•
Steady state
•
Under dynamic conditions
© KAPPA 2011
5
PL history
• Temperature logs (1930s) • Flowmeters (1940s) • Fluid-density and capacitance logs (1950s)
• Fluid velocities (1980’s) • Array probe measurements (1980’s...)
© KAPPA 2011
6
PL applications Production logs are now run for the purpose of: • Monitoring & controlling the reservoir • Analyzing dynamic well performance • Assessing productivity or injectivity of different zones • Diagnosing problem wells • Monitoring the results of a stimulation or completion The term is sometimes extended to include logs run to measure the physical condition of the well, completion and reservoir properties: • Cement bond • Pulse neutron logs • Corrosion logs • Radioactive tracer logs • Noise logs PL can be used in all stages through the life of a well
© KAPPA 2011
7
The typical well Tubing
Casing
Packer (seal)
Cement
© KAPPA 2011
8
Normal well flow
What? Where?
© KAPPA 2011
9
Typical PL toolstring
Sondex MPLT
Schlumberger PSP
© KAPPA 2011
10
PL operations – Surface readout
Risers
Grease seal Electric line
BOP
Logging unit
PL sensor data recorded in the surface computer Depth and cable speed recorded by surface computer Power sent down the cable to the tool
Sensor signals sent up the cable continuously
© KAPPA 2011
11
PL operations – Memory
Risers
Grease seal Single-strand cable
BOP
Slickline unit
Depth vs Time
Data vs Depth Reconstruction
Battery pack Memory section PL sensors
Data vs Time
© KAPPA 2011
12
Depth measurements
Courtesy : NOV ELMAR
Spring-loaded measure wheels measure the amount of wireline cable passing through
© KAPPA 2011
13
PL operations - others
Highly deviated / horizontal
Coiled tubing
Tractors
© KAPPA 2011
14
Coiled tubing
Power pack & control cabin Injector head Tool container Coil tubing reel
© KAPPA 2011
15
Tractors
Sondex MDT
Schlumberger MAXTRAC
Welltec
© KAPPA 2011
16
PL job Production rate
Up Passes
Down Passes
Full flow
Zero flow
© KAPPA 2011
17
Logging sequence Record Base Shut in Survey Well shut in for extended period
Record Post Flowing Shut in Survey (calibration, baseline)
Pressure
Time Lapse passes through shut in period
Record Flowing Survey - Well stabilized
Time
*Note: Various constraints may limit the recording or extent of some of the surveys above
© KAPPA 2011
18
Multi-rate PL (MRPL)
Shut in Pressure
Shut in Q 1/3 Q 2/3 Qmax
Time • The sequence of rates can be adjusted to suit operational & reservoir requirements • Often Qmax first, to ensure best clean out of well, and best chance of clean stable flow
© KAPPA 2011
19
PL data Depth ft
8200
8300
8400
-10
SPIN rps
CS 22 -200 ft/ min
200 0
DRHO g/ cc
1.2 0
GR GAPI
100 2820
PPRE psia 2960 500
T ENS T EMP lb 1000 244 °F 256
© KAPPA 2011
20
PL data interpreted Depth
ft
8200
8300
8400
Z
Interpretation # 1 Density matc h 246 TEMP P1,I1 [°F] 256 0 DRHO P1,I1 [g/ cc] 1.2 PPRE P1,I1 [psia] ... DRHO P1,I1 [g/ c c ]
Veloc ity matc h VAPP P1,I1 [ft/ min] ...
QZ T
-1000
B/ D
QZ I
10000 -500
B/ D
7500
© KAPPA 2011
21
PL interpretation
Proper diagnosis will rely on the interpretation of the recorded data.
Production logging is NOT flow rate measurement. Flow rates are accessed through a (complex) INTERPRETATION process
-
Complex in the understanding of the completion, the reservoir, and its history and behavior. Complex in mathematical analysis (iterations, models, correlations)
© KAPPA 2011
22
Factors affecting production
© KAPPA 2011
23
Some factors affecting production Reservoir •
Layer kh contrasts, damage
•
Fluids
•
Contacts and capillary pressures
•
Fractures (carbonates)
Wellbore •
Cement
•
Leaks due to corrosion
•
Perforations off depth, ineffective, plugged
Relevance of additional information
© KAPPA 2011
The well and permeability
CAP ROCK
Original GOC SAND B
Khorizontal & Kvertical •
Cores
•
Formation tests
•
Open hole logs
•
Well tests
Original OWC
SAND A
© KAPPA 2011
The well damage
CAP ROCK
Original GOC SAND B Damaged Zone
Skin -ve skin.. Good performance +ve skin.. Under performing
Damaged Zone
Original OWC
SAND A
© KAPPA 2011
26
Reservoir contacts
GOC OWC
Sandstone Shale Carbonate
The location of the contacts in the reservoir is used to assist us in understanding our observations in the wellbore
© KAPPA 2011
The Well fluids
Gas - Bg, Viscosity Original
CAP ROCK
density
GOC SAND B
PVT used in:
Rs GOR, density Oil - Bo, viscosity,
1. Downhole rate calculations 2. Conversion of downhole rates to standard conditions
Rs GOR, density
Original
Oil - Bo, viscosity, SAND A
OWC Water - salinity, density
© KAPPA 2011
Perforations
CAP ROCK
Original GOC SAND B
Original OWC
SAND A
© KAPPA 2011
29
Perforation guns The perforating gun comes in a number of formats, density, phase The common items are the detonator, prima cord and the shaped charge. The gun used depends on the situation/local preferences.
15 million Psi!!!
© KAPPA 2011
30
Perforation and PL Perforating parameters are important in PL Interpretation. Need to know: •
Perforation intervals
Nice to know: • • • • •
Shot density & phasing Charge type - big hole/deep penetrating Gun type – casing gun, through tubing gun Perforation performed overbalanced or under balanced Perforation history - timeline
Need to discover: • •
Which perforations are producing Are the perforations on depth, or are they even there at all?
© KAPPA 2011
Crossflow • Three layers were initially perforated
P1
P1>BHFP BHFP
P2
P3
P2
• Layer 2 pressure has somehow dropped. Possibly due to high permeability, therefore experiencing preferential production, and depleted faster. Or maybe it was just a smaller reservoir which has depleted prematurely. • A point was reached where the pressure in layer 2 is lower than the BHFP • The Crossflow behavior into layer 2 should increase during shut in
P3>BHFP
Solutions: • Flow well at higher flowrate – lower BHFP • Reperforate only layers 1 and 3 • Recomplete layer 3 through a different tubing than layer 2 • Close off layer 2
© KAPPA 2011
32
Crossflow
© KAPPA 2011
Crossflow SHUT IN
FLOWING
© KAPPA 2011
Zoned flow
Top Zone - zones of widely differing Top Zone perforated but no flow
perforated
permeability,
but some
high permeability will flow
Perforations
preferentially,
not flowing
low perm zones may not flow at all
- perforations plugged, debris from the perforation gun, mud entering while perforating overbalanced, crushed rock in the perforation tunnel
Bottom Zone perforated
but some perforations not flowing
© KAPPA 2011
35
Fracture Production
Fractures
Some perforations are crossing fractures These give high flow rates, and often strong jetting effects The remaining perforations may produce nothing
Fractures
© KAPPA 2011
36
Fracture Topography
•
Fractures occur primarily in carbonates
•
They are in a consistent direction
•
They may appear at random in the well
•
They are the major flow paths for the reservoir
•
They may connect with the gas above or the water below the oil zone and create unwanted fluid entries
© KAPPA 2011
37
Fracture Evaluation
There are a number of methods of fractures detection: •
Resistivity imaging
•
Core sample analysis
•
Well test interpretation will be affected by the presence of fractures.
•
Drilling records e.g. losses
© KAPPA 2011
38
Early gas breakthrough
OG contact
High kh layer
© KAPPA 2011
39
Early water breakthrough
High kh layer
OW contact
© KAPPA 2011
40
Channeling Bad Cement
The obvious reason for a channel is a poor primary cement job
Original GOC Unwanted channeled
This is repaired by a squeeze if the channel is identified in time (before running the completion and/or perforating)
gas flow behind casing
Channels identified during production logging are difficult to repair, though modern cementing technology can help. Original
Unwanted channeled
OWC
water flow behind casing
Bad Cement
© KAPPA 2011
41
Cementing Cementing is affected by many parameters • • • • • •
Bottom hole temperature Pressures Formation stability Fluids present, especially gas Casing centralization Well deviation The most common cause of a poor cement job is poor centralization of the casing.
© KAPPA 2011
42
Cement Evaluation There are a number of tools capable of measuring the cement quality: • Cement Bond Logging – Acoustic - transmitter & receiver - looks at the average bond around the pipe (CBL) - only tool to “see” the formation - cement bond (VDL) • Radial Cement Bond Logging – Acoustic - as above but radially distributed transmitters/receivers • Pulse Echo Logging – Ultrasonic (CAST, USI) - uses casing resonance in its thickness mode - images all around the casing - has a corrosion measurement as well
© KAPPA 2011
43
Cone Down Gas "pulled" down near wellbore
Original GOC Unwanted Fluid flow
Choking back the well may reduce this coning effect
© KAPPA 2011
44
Cone Up
Choking back the well will probably not reduce this coning The effect of the coned water is to “wet” the formation
Unwanted Fluid flow
Original OWC
Water "pulled" up near wellbore
© KAPPA 2011
45
Casing Leak Leaks occur because of corrosion in the casing or tubing Original GOC
This can happen at any time in the life of the well Logs are used to identify corroded pipe
Original OWC No Perforations
Unwanted fluid Flow from leak (+ cement)
© KAPPA 2011
46
Corrosion
stress
• Mechanical (stress, sand) • Chemical • Electrochemical H2 S
Several tools to measure corrosion: Corrosive formation fluids
CO2 bimetallism
Stagnant fluids
Mechanical calipers internal corrosion only Imaging tools - ultrasonic internal and external Electromagnetic internal and external multiple strings
1
Production Logging
1. Introduction
© KAPPA 2011
2
Introduction
•
What is Production Logging (PL) ?
•
PL applications
•
The typical well
•
The typical PL tool string
•
The PL operation
•
The PL job
•
Factors affecting well production
© KAPPA 2011
3
What is PL?
Production logging encompasses a number of well logging techniques run on completed injection or production wells, with the goal being to evaluate the well itself or the reservoir performance. SPE Monograph 14, “Production Logging”, Hill A.D.
The purpose of production logging is to provide the most detailed knowledge possible of the nature and behavior of the fluids in the well during production or injection” Production Log Interpretation, Schlumberger
© KAPPA 2011
4
What is PL?
•
Series of measurements that (hopefully…) will allow the determination of the fluid type and rate in the wellbore as a function of depth
•
Downhole and (mostly) continuous
•
Steady state
•
Under dynamic conditions
© KAPPA 2011
5
PL history
• Temperature logs (1930s) • Flowmeters (1940s) • Fluid-density and capacitance logs (1950s)
• Fluid velocities (1980’s) • Array probe measurements (1980’s...)
© KAPPA 2011
6
PL applications Production logs are now run for the purpose of: • Monitoring & controlling the reservoir • Analyzing dynamic well performance • Assessing productivity or injectivity of different zones • Diagnosing problem wells • Monitoring the results of a stimulation or completion The term is sometimes extended to include logs run to measure the physical condition of the well, completion and reservoir properties: • Cement bond • Pulse neutron logs • Corrosion logs • Radioactive tracer logs • Noise logs PL can be used in all stages through the life of a well
© KAPPA 2011
7
The typical well Tubing
Casing
Packer (seal)
Cement
© KAPPA 2011
8
Normal well flow
What? Where?
© KAPPA 2011
9
Typical PL toolstring
Sondex MPLT
Schlumberger PSP
© KAPPA 2011
10
PL operations – Surface readout
Risers
Grease seal Electric line
BOP
Logging unit
PL sensor data recorded in the surface computer Depth and cable speed recorded by surface computer Power sent down the cable to the tool
Sensor signals sent up the cable continuously
© KAPPA 2011
11
PL operations – Memory
Risers
Grease seal Single-strand cable
BOP
Slickline unit
Depth vs Time
Data vs Depth Reconstruction
Battery pack Memory section PL sensors
Data vs Time
© KAPPA 2011
12
Depth measurements
Courtesy : NOV ELMAR
Spring-loaded measure wheels measure the amount of wireline cable passing through
© KAPPA 2011
13
PL operations - others
Highly deviated / horizontal
Coiled tubing
Tractors
© KAPPA 2011
14
Coiled tubing
Power pack & control cabin Injector head Tool container Coil tubing reel
© KAPPA 2011
15
Tractors
Sondex MDT
Schlumberger MAXTRAC
Welltec
© KAPPA 2011
16
PL job Production rate
Up Passes
Down Passes
Full flow
Zero flow
© KAPPA 2011
17
Logging sequence Record Base Shut in Survey Well shut in for extended period
Record Post Flowing Shut in Survey (calibration, baseline)
Pressure
Time Lapse passes through shut in period
Record Flowing Survey - Well stabilized
Time
*Note: Various constraints may limit the recording or extent of some of the surveys above
© KAPPA 2011
18
Multi-rate PL (MRPL)
Shut in Pressure
Shut in Q 1/3 Q 2/3 Qmax
Time • The sequence of rates can be adjusted to suit operational & reservoir requirements • Often Qmax first, to ensure best clean out of well, and best chance of clean stable flow
© KAPPA 2011
19
PL data Depth ft
8200
8300
8400
-10
SPIN rps
CS 22 -200 ft/ min
200 0
DRHO g/ cc
1.2 0
GR GAPI
100 2820
PPRE psia 2960 500
T ENS T EMP lb 1000 244 °F 256
© KAPPA 2011
20
PL data interpreted Depth
ft
8200
8300
8400
Z
Interpretation # 1 Density matc h 246 TEMP P1,I1 [°F] 256 0 DRHO P1,I1 [g/ cc] 1.2 PPRE P1,I1 [psia] ... DRHO P1,I1 [g/ c c ]
Veloc ity matc h VAPP P1,I1 [ft/ min] ...
QZ T
-1000
B/ D
QZ I
10000 -500
B/ D
7500
© KAPPA 2011
21
PL interpretation
Proper diagnosis will rely on the interpretation of the recorded data.
Production logging is NOT flow rate measurement. Flow rates are accessed through a (complex) INTERPRETATION process
-
Complex in the understanding of the completion, the reservoir, and its history and behavior. Complex in mathematical analysis (iterations, models, correlations)
© KAPPA 2011
22
Factors affecting production
© KAPPA 2011
23
Some factors affecting production Reservoir •
Layer kh contrasts, damage
•
Fluids
•
Contacts and capillary pressures
•
Fractures (carbonates)
Wellbore •
Cement
•
Leaks due to corrosion
•
Perforations off depth, ineffective, plugged
Relevance of additional information
© KAPPA 2011
The well and permeability
CAP ROCK
Original GOC SAND B
Khorizontal & Kvertical •
Cores
•
Formation tests
•
Open hole logs
•
Well tests
Original OWC
SAND A
© KAPPA 2011
The well damage
CAP ROCK
Original GOC SAND B Damaged Zone
Skin -ve skin.. Good performance +ve skin.. Under performing
Damaged Zone
Original OWC
SAND A
© KAPPA 2011
26
Reservoir contacts
GOC OWC
Sandstone Shale Carbonate
The location of the contacts in the reservoir is used to assist us in understanding our observations in the wellbore
© KAPPA 2011
The Well fluids
Gas - Bg, Viscosity Original
CAP ROCK
density
GOC SAND B
PVT used in:
Rs GOR, density Oil - Bo, viscosity,
1. Downhole rate calculations 2. Conversion of downhole rates to standard conditions
Rs GOR, density
Original
Oil - Bo, viscosity, SAND A
OWC Water - salinity, density
© KAPPA 2011
Perforations
CAP ROCK
Original GOC SAND B
Original OWC
SAND A
© KAPPA 2011
29
Perforation guns The perforating gun comes in a number of formats, density, phase The common items are the detonator, prima cord and the shaped charge. The gun used depends on the situation/local preferences.
15 million Psi!!!
© KAPPA 2011
30
Perforation and PL Perforating parameters are important in PL Interpretation. Need to know: •
Perforation intervals
Nice to know: • • • • •
Shot density & phasing Charge type - big hole/deep penetrating Gun type – casing gun, through tubing gun Perforation performed overbalanced or under balanced Perforation history - timeline
Need to discover: • •
Which perforations are producing Are the perforations on depth, or are they even there at all?
© KAPPA 2011
Crossflow • Three layers were initially perforated
P1
P1>BHFP BHFP
P2
P3
P2
• Layer 2 pressure has somehow dropped. Possibly due to high permeability, therefore experiencing preferential production, and depleted faster. Or maybe it was just a smaller reservoir which has depleted prematurely. • A point was reached where the pressure in layer 2 is lower than the BHFP • The Crossflow behavior into layer 2 should increase during shut in
P3>BHFP
Solutions: • Flow well at higher flowrate – lower BHFP • Reperforate only layers 1 and 3 • Recomplete layer 3 through a different tubing than layer 2 • Close off layer 2
© KAPPA 2011
32
Crossflow
© KAPPA 2011
Crossflow SHUT IN
FLOWING
© KAPPA 2011
Zoned flow
Top Zone - zones of widely differing Top Zone perforated but no flow
perforated
permeability,
but some
high permeability will flow
Perforations
preferentially,
not flowing
low perm zones may not flow at all
- perforations plugged, debris from the perforation gun, mud entering while perforating overbalanced, crushed rock in the perforation tunnel
Bottom Zone perforated
but some perforations not flowing
© KAPPA 2011
35
Fracture Production
Fractures
Some perforations are crossing fractures These give high flow rates, and often strong jetting effects The remaining perforations may produce nothing
Fractures
© KAPPA 2011
36
Fracture Topography
•
Fractures occur primarily in carbonates
•
They are in a consistent direction
•
They may appear at random in the well
•
They are the major flow paths for the reservoir
•
They may connect with the gas above or the water below the oil zone and create unwanted fluid entries
© KAPPA 2011
37
Fracture Evaluation
There are a number of methods of fractures detection: •
Resistivity imaging
•
Core sample analysis
•
Well test interpretation will be affected by the presence of fractures.
•
Drilling records e.g. losses
© KAPPA 2011
38
Early gas breakthrough
OG contact
High kh layer
© KAPPA 2011
39
Early water breakthrough
High kh layer
OW contact
© KAPPA 2011
40
Channeling Bad Cement
The obvious reason for a channel is a poor primary cement job
Original GOC Unwanted channeled
This is repaired by a squeeze if the channel is identified in time (before running the completion and/or perforating)
gas flow behind casing
Channels identified during production logging are difficult to repair, though modern cementing technology can help. Original
Unwanted channeled
OWC
water flow behind casing
Bad Cement
© KAPPA 2011
41
Cementing Cementing is affected by many parameters • • • • • •
Bottom hole temperature Pressures Formation stability Fluids present, especially gas Casing centralization Well deviation The most common cause of a poor cement job is poor centralization of the casing.
© KAPPA 2011
42
Cement Evaluation There are a number of tools capable of measuring the cement quality: • Cement Bond Logging – Acoustic - transmitter & receiver - looks at the average bond around the pipe (CBL) - only tool to “see” the formation - cement bond (VDL) • Radial Cement Bond Logging – Acoustic - as above but radially distributed transmitters/receivers • Pulse Echo Logging – Ultrasonic (CAST, USI) - uses casing resonance in its thickness mode - images all around the casing - has a corrosion measurement as well
© KAPPA 2011
43
Cone Down Gas "pulled" down near wellbore
Original GOC Unwanted Fluid flow
Choking back the well may reduce this coning effect
© KAPPA 2011
44
Cone Up
Choking back the well will probably not reduce this coning The effect of the coned water is to “wet” the formation
Unwanted Fluid flow
Original OWC
Water "pulled" up near wellbore
© KAPPA 2011
45
Casing Leak Leaks occur because of corrosion in the casing or tubing Original GOC
This can happen at any time in the life of the well Logs are used to identify corroded pipe
Original OWC No Perforations
Unwanted fluid Flow from leak (+ cement)
© KAPPA 2011
46
Corrosion
stress
• Mechanical (stress, sand) • Chemical • Electrochemical H2 S
Several tools to measure corrosion: Corrosive formation fluids
CO2 bimetallism
Stagnant fluids
Mechanical calipers internal corrosion only Imaging tools - ultrasonic internal and external Electromagnetic internal and external multiple strings
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