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Mudlogging Services
Mohamed Bekhit
14 February 2010
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Mud Logging: An Overview
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What Is Mud Logging?
Mud logging is the process of continuously collecting,recording and analyzing the meaningful solids, fluids,
and gasses brought to the surface by mud.
Provide comprehensive drilling data parameterrecording, monitoring and analysis.
Real-time information service.
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Mudlogging Operations Connection
Adding fresh length (joint
or stand) of pipe so that
the bit can drill deeper.
While connection check
the pit system level and
check gas trap level and
shakers.
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Mudlogging Operations Connection
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Withdrawing the drillstring isknown as (tripping out) and the
whole operation of extraction
and re-insertion (tripping in) of
the drillstring is a round trip.
POOH (pull out of hole) is
another expression for tripping
out.
RIH (run in hole) is another
expression for tripping in
Mudlogging Operations Tripping
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Mudlogging Operations POOH
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Mudlogging Operations RIH
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Mudlogging Operations
Back-reaming
Continuous rotation of the Drillstring as it is being
pulled out of the hole in order to keep the hole cleanand maintain the wellbore in gauge
Wiper Trip
To prevent cuttings build up, esp. in deviated wells
POOH to last casing shoe or to pull out a few stands
(10-30 stands)
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1. Suction Pit2. Mud Pump
3. Standpipe
4. Swivel
5. Kelly
6. Drillstring and Bit
7. Annulus
8. Return Flowline /Shakers
9. Suction Pit
Drilling Fluid Circulating System
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Circulating System Shale Shaker
Shale shaker
Flowline
Possum belly
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Lag Time Determination
What is Lag Time
What are the factors affecting Lag Time
How is Lag Time measured
How is Lag Time checked
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Lag time is the definite time interval required forpumping drilled cuttings from a particular depth to the
surface where they can be collected
Lag Time Definition
Always exists
Changes continuously as the hole deepens
Must be frequently checked and corrected
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Lag Time
Factors Affecting Lag Time Volume of the mud in the Annulus
Mud flow rate
Annulus
It is the space around a pipe in the wellbore, the outer
wall being the wall of either the hole or casing
Sometimes called annular space
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Volume of Mud in the Hole As hole gets deeper, mud volume increases,
therefore, lag time increases
As the annular diameter gets larger due to hole
washouts the mud volume increases, the lag timeincreases
Mud Flow Rate
The faster the mud is pumped the quicker it returns to
the surface and hence the lag time is reduced
Lag Time
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Lag Time Measured Using Velocity Method
Annular velocityann. sec
(ft/min) = 24.51 x Q / (D2 d2)
Where,
Q = flow rate (gpm), D = hole or casing ID (ins.), d =
DP/DC OD (ins.)
Lag time ann. sec (mins) = Length of annular section / Annular
velocity of annular section
Lag time (mins) = Lag time ann. sec
Lag time (strokes) = Lag time (mins) x spm
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Lag Time Measured Using Volume Method
Annular volume = (D2 d2) x 0.000971 x Length of annular
section
or
Annular volume = ((D2 d2) / 1029.4) x Length of annular
section
Lag time ann. sec (mins) = Annular volume (bbls) / flow rate
(bbls/min)
Lag time (mins) = Lag time ann. sec
Disadvantage: affected by flow rate changes
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Lag Time Measured Using Volume Method
Annular volume = (D2 d2) x 0.000971 x Length of annular
section or
Annular volume = ((D2 d2) / 1029.4) x Length of annular
section
Pump Output (bbls/stroke) = Pump output (gpm) / (spm x42)
Lag time ann. sec (strokes) = Annular volume (bbls) / Pump
Output (bbls/stroke)
Advantage: not affected by changes in flow rate
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Well Profile
Depth: 7750 ft
Hole size: 8.5
Pump Output: 425 gpm at 100 spm
Casing:
shoe at 6000 ft
9 5/8 OD; 9 ID
DP:
6350 ft.
5 OD; 4.276 ID
DC:
1400 ft.
7 OD; 3.5 ID
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Example #1 (Velocity Method)
Section 1: 24.51 x 425 / (92 - 52)
Annular Velocity = 186 ft/min
Annular Section = 6000 feet
Lag Time for Section = 32.26 minutes
Section 2: 24.51 x 425 / (8.52 - 52)
Annular Velocity = 220.46 ft/min
Annular Section = 350 feet
Lag Time for Section = 1.59 minutes
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Example #1 (Velocity Method)
Section 3: 24.51 x 425 / (8.52 - 72)
Annular Velocity = 448 ft/min
Annular Section = 1400 feet
Lag Time for Section = 3.13 minutes
Total Lag Time = 32.26 + 1.59 + 3.13 = 36.98 minutes
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Example #2 (Volume Method)
Section 1: (92 - 52) x 0.000971 x 6000
Annular volume = 326.25 bbls
Section 2: (8.52
- 52
) x 0.000971 x 350
Annular volume = 16.05 bbls
Section 3: (8.52 - 72 ) x 0.000971 x 1400
Annular volume = 31.60 bbls
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Example #2 (Volume Method)
Pump output (bbls/min) = 425 gpm/42 = 10.12 bbls/min
Pumps are pumping at 100 spm -> Pump output
(bbls/stroke)= 10.12/100 = 0.1012 bbls/stroke
Total Lag Time (strokes)
= (326.25 + 16.05 + 31.6) / 0.1012
= 374.15 / 0.1012 = 3697 strokes
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Lag Time Check
Under normal circumstances a check should be made
every twenty-four hours or 400 ft , wh ichever comes
f i rs t. However, if carbide information is required due to
suspicions of incorrect lag or washout, then carbides
should be run as required
A traceris used to obtain an accurate measurement of
lag time
Common tracers used are:
Calcium carbide (most common)
Rice, lentil, cellophane
Carbide + water -> acetylene
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Example
Example:
Actual strokes from carbide = 5128 strokes
Calculations:
Down strokes are 1278 strokes.
Lag strokes are 3697 strokes
Pump output is 0.1012 bbls/stroke
Calculate carbide check?
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Collecting a Sample
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Paleontological Analysis Geochemical Analysis
Oil Company Partners
Governmental Requirements
Future Reference / Library Samples
Reasons For Sample Collection
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Sample Intervals
Set by the client
Common intervals: 5 feet to 30 feet
Regardless of the sampling interval, under no circumstances
should the Mudloggers neglect their other responsibilities
Other times that the sample interval should be shortened: During coring 1 ft or 0.5 meter intervals
Areas of geological interest
Changes in drilling parameters (drill breaks / reverse drill breaks,
torque changes) Changes in mud properties (viscosity, cut MW, chlorides, etc)
Changes in gas content
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Sample Types
Unwashed Samples
Washed and Dried Samples
Geochemical Samples
Paleontological Samples
Metal Shavings
Mud Samples
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Sample Collection
Install a sample collection board at the base of the shaker
Try to collect from the shaker with the smallest mesh size
Samples are taken at regular intervals specified by the
client
Samples should be taken when changes in ROP,
background gas or any other parameter is noticed
When sampling in smaller intervals than required, the
sample bags should be progressively filled up
Clean the sample board after a sample is taken
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Sample Catching Board
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Sample Preparation
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Cuttings Examination
Samples are examined under the microscope for:
Lithology
Oil staining
Porosity
Objective:
To depict changes of lithology and appearance of
new formations
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Cuttings Examination
Sources of Sample Contamination
Cavings
Recycled Cuttings
Mud Chemicals
Cement
Metal
Unrepresentative Samples
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Sample Description
Allows others to understand the components and
structure of the rock and to draw conclusions as to the
source, depositional environment and subsequenthistory of the formation
Allows others to recognize the rock whenever it is
seen again
Major Functions of Sample Description
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Porosi tyis a measure of the volume of void space inthe rock. It determines the amount of fluid that is
present in a rock.
Permeabil i tyis a measure of the capacity of a rock
for transmitting fluid and it is dependent on effectiveporosity and the mean size of the individual pore
spaces. It has a direct bearing on the amount of fluid
that can be recovered.
Porosity and Permeability
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Sample Description Format
Rock type / Classification
Color
Texture: Cuttings shape and parting (calcareous and
argillaceous lithologies), Grain size, Grain shape or
roundness, Sorting, Hardness or induration, Luster / Slaking /
Swelling
Cementation or matrix
Fossils and accessories
Visual structures Visual porosity
Oil show descriptions
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Particle Shape: Roundness vs. Sphericity
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Sorting
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Solid Hydrocarbons and Dead Oil
Oil show description
Hydrocarbon Odor
Oil Staining
Natural Fluorescence
Solvent Cut Fluorescence
Other Tests
Oil Show Evaluation
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Take a mud sample, aside from the regular sampleor bottoms up sample, when there are significant
gas shows. If a significant gas peak arrives in
between sampling intervals, a spot sample is
caught along with a mud sample. Pour mud sample into a shallow dish and observe
under UV light. If nothing is seen, water is added to
the mud and the mixture is stirred. Again the
sample is observed under UV light.
Sample Examination Procedure For HC Shows
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Sample Examination Procedure For HC Shows
The unwashed sample is also observed under UVlight.
For the lithological samples, smell the sample firstbefore observing it under the microscope. Observe
sample under microscope for staining / bleeding.
Place some oil-stained cuttings, if any, into some ofthe depressions on the spot plate. Observe undermicroscope.
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Sample Examination Procedure For HC Shows
Observe sample tray under UV light. Separatesome fluorescing grains and place them in the spot
plate.
Observe the grains that have been selected in Step
6 under the microscope for stains/bleeding.
Use the Solvent Cut Test on the samples in the
spot plate. Observe under UV light.
Observe cutting samples in plain light.
Observe the residue.
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Observing a Sample Under the UV Box
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Free oil in mud: amount, intensity and color Petroliferous odor: type and strength
Visible oil staining/bleeding: distribution, intensity and
color
Sample Fluorescence: percentage, intensity, color
Solvent cut: speed, character, intensity and color
Cut color and intensity
Cut residue (intensity and color)
Order of Oil Show Description
Bl di C S l
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Bleeding Core Sample
Fl I di ti f API G it
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Gravity (API) Color at 3600A
< 15 Brown
15 - 25 Orange
25 - 35 Yellow to Green
35 - 45 White
> 45 Blue White to Violet
Fluorescence: Indication of API Gravity
Mi l Fl
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Rock Type Fluorescence Color
Dolomite, Sandy Limestone yellow, yellowish brown
Some Limestones (magnesian) brown
Chalk, chalky limestones purple
Paper Shale yellow to coffee brown, greyish
Fossils yellow-white to yellow-brown
Marl, Clay Marl yellowish to brownish grey
Anhydrite grey brown, greyish, blue
Mineral Fluorescence
S l t C t W t C t T t
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The speed in which the solvent cut occurs yieldsuseful info
If the suspected cutting will not initially cut, the test
can be repeated. Samples can be dried, crushed or
have diluted HCl applied to it
The residue oil that remains in the spot plate is the
oils natural color
Be careful not to get the cutting agent into the rubberof the dropper as it might contaminate the solvent by
giving it a pale yellowish fluorescence
Solvent Cut or Wet Cut Test
H T D A S l t C t T t
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Place a few drops of solvent, enough to immerse
the sample, on the sample in the depression in the
spot plate or the test tube.
Observe the following:
Cut speed
Cut nature
Cut color fluorescence and intensity
Cut color intensity
Residue color and intensity
How To Do A Solvent Cut Test
S
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Lack of visible stain is not conclusive proof of theabsence of hydrocarbons
Lack of fluorescence is not conclusive proof of the
absence of hydrocarbons
Hydrocarbon shows will usually give a positive cut
fluorescence (wet cut). High gravity hydrocarbons will
often give a positive cut fluorescence and/or a
residual cut, but will give negative results with all other
hydrocarbon detection methods. Minerals whichfluoresce will not yield a cut.
Summary
R ibiliti f M d L
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To collect and record all the engineering andgeological data obtained while drilling
To interpret the acquired data
To inform the client of significant changes in the well
Maintain good relations with the client and other
personnel on the rig
Ensure that the unit and equipment are properly
maintained and in good working order
To perform all duties in a safe manner
Responsibilities of a Mud Logger
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THE END