Eval-Module 4 Flashcards
What do GR/CCL logs do?
Correlate open-hole logs to markers in/behind the casing
What do CBL/VDL log asses?
Hole intergrity (casing-cement-formation)
TDT logs/Sonic logs/Neutron-density logs/resistivity logs monitor/improve production by?
- evaluating the formation for Sw
- determining down=hole flow rates and the type of production
What are the 2 major areas of cased hole logging?
Production logging
Reservoir monitoring
Define production logging
to obtain production injection profiles over a completed interval
Define Reservoir monitoring
To obtain real time information about changes in hydrocarbon saturation
what does CCL stand for?
Casing Collar Location Tool
What does CBL stand for?
Cement bond log
What is the most effective correlation log and what does it measure and how?
Gamma Ray
- the radiation is measurable through casing
- depth measurements are precise and easy to compare with open-hole gamma ray logs as perforation must run exactly where they should be.
What are some challenges of GR in cased holes?
- Fragile
- must be run slowly
What do CCL tool’s correlate?
Open-hole logs to markers in the casing
What dies the CCL tool consist of?
permanent magnet
electrical coils
What does the CCL tool run in conjunction with?
runs with GR log (known as GR/CCL tool) to easily and quickly relate open-hole logs to this detectable casing feature.
What does the CCL tool reveal?
The exact depths f the zones to be perforated.
What are 4 problems related to a poor cement job?
- affect hydraulic isolation of zones
- reduce productivity through mingling fluids
- Expose pipe to corrosion
- allow saline water to contaminate fresh water
What does the CBL asses?
The quality of bonding between casing/cement/borehole
How do CBL work?
- Applies sonic waves and records their transit time using 1 transmitter and 2 receivers
- Emits pulses of sound energy that travel in all directions
What do the upper and lower receiver record in a CBL?
UPPER- records acoustic energy returned from cement-casing contact (CBL)
LOWER- records cement bond to formation (VDL)
What does VDL stand for?
Variable density log
What are some formation related problems shale can cause?
Geo pressure shale Reactive shale (swelling)
What are the top 6 sources of downhole problems and which are geology related?
Equipment failure Cement problems Stuck pipe lost circulation wellbore stability well control (last 4 geology related)
What are the 5 typical logs on a CBL presentation?
Transit time Gamma Ray CCL Amplitude VDL
What does CBL measure?
the amplitude (mV) transit time (delta t)
Define attenuation of the signals
as sound travels fastest through the steel casing, the receiver signals are affected by the % of casing bonded to the cement (aka-BI)
Whats considered a good BI and bad BI?
good >.80
bad<.80
are CBL good in oils and water zones or good in gas zones?
good-oil/water zones
poor- gas zones
Which way to signals peak in CBL’s and what do they mean?
Highest amplitude- signals peak to the right (max attenuation)= FREE PIPE
Lower amplitude- signals peak to the left (min attenuation)=
BETTER BOND BETWEEN CASING AND CEMENT
What do VDL’s measure?
The bond between formation and the cement
What 3 recordings do VDL logs consist of?
- Arrival time from casing
- Arrival time from formation and cement
- Arrival time from mud
What 4 logs are used to monitor/improve production by evaluating sw of the formations?
TDT logs
Sonic Logs
Neutron-Density logs
Resistivity logs
What 4 logs are used to monitor/improve production by determining down hole flow rates/production?
Flowmeter logs
Radioactive tracer logs
temperature logs
noise logs
What is a TDT log?
What odes it capture?
Thermal Decay Time Log
is a pulsed neutron tool to determine sw behind casing
It captures sigma, cross section
When does channeling occur?
when a vertical portion of the pipe is NOT bonded over a significant distance
When does a microannulus occur?
when small gaps are formed between casing and cement in an otherwise well-cemented casing
What 3 things does sigma in a reservoir rock depend on?
- porosity
- salinity
- qty & type of HC
What 5 things do you need to know in a TDT log?
- porosity
- water salinity
- lithology
- shaliness
- type of HC
What casing logs are used primarily to determine Sw?
- Sonic
- CNL (neutron porosity)
- density
- Resistivity
How does a radioactive tracer log work?
a radioactive fluid is injected along with injection water to determine if the perforation are isolated or if leakage has occurred.
What is noise logging primarily used for?
Channel detection
Measure flow rate
What is a noise log?
What does high and low amplitude indicate?
a records of the sound measured at different position in the borehole
HIGH- greater turbulence such as leaks, channels
LOW- low turbulence, no channeling
What are different frequency ranged tied to in noise logs?
to different sources of noise or different flow regimes
What does a temperature log determine?
fluid entries-especially gas
eg. when gas flows through perforation, pressure decreases and temperature decreases.
What is one way to determine flow behind casing with a temperature log?
shut in well for several days so temperature can stabilize.
