Mudlogging Operations

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Mudlogging Services

Mohamed Bekhit

14 February 2010


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2007 Weatherford. All rights reserved.1

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




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Example #1 (Velocity Method)

Section 3: 24.51 x 425 / (8.52 - 72)

Annular Velocity = 448 ft/min



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


Section 3: (8.52 - 72 ) x 0.000971 x 1400



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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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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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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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