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Mud Engineering

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Content

Mud Engineering
Important Notes

Basics
Mud
Mud Engineering
Engineering
MUD
MUD

RIG
RIG

Parameters
Parameters && Tests
Tests

Calculations
Calculations

Products
Products

Drilling
Drilling Problems
Problems

Clay
Clay Chemistry
Chemistry

Drill
Drill String
String

Contaminates
Contaminates
Mud
Mud Types
Types

Mud Parameters & Tests
1)
2)
3)
4)
5)
6)
7)
8)
9)
10)

Viscosity
Density
Fluid Loss
pH
Solids
Chlorides
Calcium & Hardness
MBT
Pf , Mf and Pm
Lime Content

1) Viscosity






Meaning: The fluid resistance to flow, and is a
relation between shear stress and shear rate.
Measured: by Funnel Viscosity (sec./quad).
Viscosifiers:
1)Bentonite: Used in spud mud at surface holes
after dispersion and prehydrated .Lime is added
for flocculation. (SG: 2.6)
2)Polymers: (ex: XC Polymer, HEC, PAC).
Mainly XC-Polymer is used as it gives PV, YP and
gel strength, HEC and PAC are mainly used as
fluid loss reducers they don’t give good rheology.

Plastic Viscosity


Meaning:

Is the part of resistance to flow
caused by mechanical friction.



Affected by:

Solids conc., shape and size.
Presence of long chain

polymers.


Measured:

Using V-G meter
R600-R300



Chemicals used: Bentonite( if it can be used)
Polymers

Yield Point


Meaning: Measure of attractive forces in the mud,
responsible for suspension of cuttings in dynamic
conditions (carrying capacity).



Affected by: Surface properties of the fluid.
Solids Concentration.
Electrical environment of these fluids.
Measured: Using V-G meter
R300- PV
Chemicals used: Bentonite( if it can be used)
Polymers





Gel Strength


Meaning: Is the attractive force between
particles of the solution, responsible for the
suspension of cuttings in static conditions
(carrying capacity).



Affected by: Anything promoting or
preventing the linkage of particles.



Measured:



Using V-G meter
R3 (10 sec.)/ R3 (10 min.)
Chemicals used: Bentonite( if it can be used)
Polymers

2) Density


Meaning: mud weight (Lb/ft3)



Affected by: Amount of solids in the mud.



Measured by: Mud balance



Chemicals used:
Barite(BaSo4)
max. 152 (Lb/ft3)
SG:4.2
Marble Fine(CaCo3) max. 86 (Lb/ft3)
SG:2.8
Calcium Chloride
max. 88.3 (Lb/ft3)
Sodium Chloride
max. 74.9 (Lb/ft3)
Potassium Chloride max. 73.3 (Lb/ft3)

3) Fluid Loss


Meaning: Amount of fluid forced into permeable
formation by differential pressure, after the
deposition of thin, low permeable filter cake to
seal permeability



Affected by: Time, Pressure, viscosity, Filter
cake permeability and solids orientation and
composition.



Measured by: API Fluid loss



Chemicals used: PAC (polyanionic cellulose).
STARCH
HEC (hydroxyethyl cellulose).

4) pH


Measured: 1) pH meter 2) pH strip



Chemicals: Caustic Soda
Potash
Lime
Soda Ash

5) Solids


Measured: Retort Analysis



Effect: Increases Mud Weight and
Plastic Viscosity.
Type: High Gravity Solids (SG>
4.2)
Low Gravity Solids (SG < 3 )



6) Chloride Content





1 ml filtrate + few drops Potassium
Chromate.
Titrate with Silver Nitrate
Multiply the volume of Silver Nitrate
needed to change the color from
yellow to orange red and persists
for 30 second by Silver Nitrate
concentration (1,000 or 10,000).

7) Calcium Content





1 ml filtrate + few drops NaOH +
Caliver II Indicator
Titrate with EDTA solution
Multiply the volume of EDTA
needed to change the color from
wine red to blue with no traces of
under tint red remaining by EDTA
concentration (200 or 400).

Hardness (Ca++ & Mg+)





1 ml filtrate + few drops Ammonia +
Caliver II Indicator
Titrate with EDTA solution
Multiply the volume of EDTA needed
to change the color from wine red to
blue by EDTA concentration (200 or
400).

8) MBT










1 ml mud + 10 ml water + 15 ml (3% H2O2)
+ 0.5 (5N Sulfuric Acid)
Boil Gently for 10 min.
Dilute to about 50 ml with water.
Add 0.5 ml Methylene blue solution and shake
for 30 sec. then take a drop on a filter paper.
The end point is reached when a blue sun shine
ring appears around the dyed solution.
Measure the amount of drops and multiply by 5.

9) Pf
1.
2.

3.

4.

5.

1 ml filtrate + 5 ml deionized water
Add few drops Phenol Phethylene
indicator.
If the color turns pink titrate by N/50
Sulfuric Acid.
The end point is reached when the pink
color disappears.
Pf is the number of ml of Acid per ml
filtrate required to reach the end point.

Mf
6. To the same sample used for measuring
Pf, add 3 to 4 drops of methyl orange
cresol green indicator; a green color will
develop.
7. Titrate with N/50 acid until the color
changes to yellow. This will occur at pH
of 4.3.
8. The Mf is reported as the total ml of
acid used for Pf plus this last titration.

Pm
1. Measure 1 ml of mud + 25 ml distilled water
+ add 5 drops phenolphthalein indicator
2. Titrate quickly with N/50 acid or 0.1 N acid
until the pink color disappears.
3. Report the phenolphthalein alkalinity of the
mud, Pm, as the number of ml of (N/50) acid
required per ml of mud. If 0.1 N acid is used,
Pm = 5 x ml of 0.1 N acid per ml mud.

10) Lime Content
1.
2.

3.

Determine the Pf and Pm.
Determine the volume fraction of water
in the mud, Fw (decimal fraction of
water), using the value from the retort
test.
Report the lime content of the mud in
lb/bbl calculated from the following
equation:
Lime (lb/bbl) = 0.26 x (Pm - FwPf).

Products
1) Weighting Materials 8) Emulsifiers
2) Viscosifiers
9) Thinners
3) L C M
10) Commercial
Chemicals
4) Filtration Control
11) H2S Scavengers
5) Shale Stabilizers
6) Lubricants
7) Torque Reducers

12) O2 Scavengers
13) Bacteriocids
14) Defoamers

1) Weighting Materials


Barite(BaSo4)

max. 152 (Lb/ft3)



Marble Fine(CaCo3) max. 86 (Lb/ft3)



Calcium Chloride

max. 88.3 (Lb/ft3)



Sodium Chloride

max. 74.9 (Lb/ft3)



Potassium Chloride max. 73.3 (Lb/ft3)

Barite


Barite can be used to increase the density of any
mud system. Mud weights up to 150 pcf can be
achieved in most drilling fluids while still
maintaining good flow properties. Barite is also
excellent in formulating special kill fluids and barite
plugs that often reach 165 pcf for well control
procedures.



An increase in volume of approximately 1.4
bbl/ton can be expected from Barite additions.
Density increases may require water or base liquid
dilution sufficient to wet the surfaces of the added
barite adequately.

Barite Mass Increase


How many Lbs of bentonite is added to
change the weight from W1 to W2? (2 Ways)

Lb/bbl needed= 1471 x (W1-W2)
35-W2
Specific gravity of bentonite =4.2
,
Density of water=8.3 Lb/gal
4.2 x 8.3 =35 Lb/gal
, 35 Lb/gal x 42 gal= 1471
Lb/bbl

Lb/bbl needed= 10 Lb x (W1-W2) x Vw
5500 Lb
Vw= Volume of water needed for the mix

Marble Mass Increase


How many Lbs of Marble fine is added to
change the weight from W1 to W2?

Lb/bbl needed= 945x(W1-W2)
22.5-W2
Specific gravity of bentonite =2.7
Density of water=8.3 Lb/gal
2.7 x 8.3 =22.5 Lb/gal
22.5 Lb/gal x 42 gal= 945 Lb/bbl

2) Viscosifiers
Bentonite
XC - Polymer

Bentonite






Bentonite is used to increase viscosity and reduce fluid
loss in water-base drilling fluids. It is a cost-effective
means of achieving viscosity, fluid loss control and filter
cake quality in freshwater and seawater muds.
Typical concentrations for Bentonite range from 5 to 35
lb/bbl. As with all Bentonite products, the yield
decreases as water salinity increases. In muds
containing more than 10,000 mg/l chlorides, the
performance of Bentonite is significantly reduced unless
prehydrated in fresh water before adding to the mud
system.
Performance reduced in salty (>5,000 mg/l Cl-) or
hard (>240 mg/l Ca++) waters due to decreased
hydration

XC Polymer






The primary function of XC Polymer is to increase viscosity
for cuttings transport and suspension. XC Polymer will
perform effectively in all waterbase fluids, from highly
weighted to low-solids systems.
The amount of XC Polymer required will depend upon the
desired viscosity. Normal concentrations range from 0.25 to
2 lb/bbl for most mud systems. Special fluids and difficult
hole-cleaning conditions may require higher concentrations
up to 4 lb/bbl. The addition of salt, an antioxidantand
thermal stabilizers will improve temperature stability in
fluids from 250° to >280°F .Specially formulated systems
have been used at temperatures of 400°F. XC Polymer is
subject to bacterial degradation, and treatments with a
biocide are recommended to prevent fermentation.
Not tolerant of high pH or high calcium ion conditions

3) Loss Circulation
Materials
1.

MICA “Coarse” and MICA “Fine”

2.

Walnut Shell

3.

Cotton Seed

4.

Marble Medium and Marble Coarse

4) Filtration Control
Starch
PAC
Antisol

PAC










Description : PolyAnionic Cellulose, provides filtration
control in most water-based drilling fluids.
Applications/Functions :
Control filtration rates without significantly increasing
fluid viscosity (Unless using PAC-R).
Encapsulate shale to prevent swelling and
disintegration
Advantages : Is stable at temperatures up to 300 F.
Effective in moderate to high pH systems.
Does not require a bacteriacide.
Typical Properties : Bulk density, pcf 40-55
pH (1% aqueous solution) 7.75
Recommended Treatment :
Add (0.5-3.0 lb/bbl) of PAC-L slowly through the hopper.

5) Shale Stabilizers
1.

Soltex

2.

BlackNite

3.

KCl (Shale Inhibitor)

6) Lubricants (Stuck pipe)



EZ Spot
Pipe Lax

7) Torque Reducers


Lube 167

8) Emulsifiers
Enables water to be mixed with Diesel
 Safe Surf
 Surfak
 LoSurf

9) Thinners


ThermaThin

10) Commercial Products
Caustic Soda
Soda Ash
Sodium Bicarbonate
Lime

Caustic Soda “ NaOH “
CAUSTIC SODA is used to maintain or increase pH.
Increasing pH with CAUSTIC SODA will precipitate (Mg2+)
and suppress (Ca2+) in high hardness waters such as
seawater, reduce corrosion, and neutralize acid gases
such as (CO2) and (H2S).

When using CAUSTIC SODA to reduce hardness:
CAUSTIC SODA (lb/bbl) =
[Mg (mg/l) x 0.00115 x Fw] +[Ca (mg/l) x 0.0007 x Fw]

In high hardness brines such as CaCl2, CAUSTIC SODA
cannot be used to effectively to raise the pH due to
the high level of cations which combine with hydroxyl ions
to precipitate hydroxides such as Ca(OH)2 and Mg(OH)2.


Soda Ash “ Na2CO3 “












SODA ASH is primarily used to reduce soluble calcium in
water-base drilling muds and makeup waters. Other uses
include increasing pH and flocculating spud muds.
Calcium is present in many makeup waters and formations.
It can cause flocculation of the mud resulting in increased
rheology, gel strengths and fluid loss.
The calcium precipitation chemical reaction is described as:
Ca2+ + Na2CO3
CaCO3 + 2Na+
(9.7 < pH < 11.7)
When using SODA ASH to reduce hardness:
SODA ASH (lb/bbl) = Ca (mg/l) x 0.00093 x Fw
In pure water, SODA ASH forms highly buffered solutions
which range between a pH of 10.9 to 11.6
Should not be used to treat cement contamination or
higher pH fluids; is less soluble at high pH.
Over treatment results in carbonate contamination;
even minor amounts of excess carbonate ions can cause
large increases in yield point, gel strengths and fluid loss.

Sodium Bicarbonate
“NaHCO3”


Cement contains calcium hydroxide (lime) and
related compounds which increase pH and
calcium concentration. These changes
flocculate bentonite based muds, resulting in
increased rheology and fluid loss. Sodium
Bicarbonate is an economical and effective
treatment for cement contamination. It
precipitates calcium, reduces pH and
deflocculates cement contaminated fluids.



A simplification of the chemical reactions for
precipitating lime with Sodium Bicarbonate is:
Ca(OH)2 + NaHCO3 CaCO3 + NaOH + H2O

Sodium Bicarbonate
Cont’d








When using Sodium Bicarbonate to treat cement
contamination: Sodium Bicarbonate (lb/bbl) =
Excess lime (lb/bbl) x 1.135 x Fw
Unless a low pH is desired, Sodium Bicarbonate
should not be used to treat soluble calcium in
water-base muds and makeup waters; soda ash
should be used to reduce calcium and soften makeup
water.
When treating severe cement contamination, Sodium
Bicarbonate will not reduce pH by itself; an acid
or other pH-reducing additive should be used with
Sodium Bicarbonate for these situations.
Over treatment results in bicarbonate, or
carbonate, contamination. Even minor amounts of
excess carbonate and bicarbonate ions can cause large
increases in yield point, gel strengths and fluid loss.

Lime “ Ca(OH)2 “










LIME is used as an economical source of calcium for
flocculating bentonite slurries (spud mud) for
improved hole cleaning.
Excess LIME buffers pH; provides a reserve quantity
of calcium to precipitate soluble carbonates; and
activates fatty-acid, oil-base additives.
The solubility of LIME increases with increased
salinity, but decreases with increased calcium,
increased pH and increased temperature.
LIME should be added slowly to the mud system
through a properly designed mud hopper. Do not mix
LIME with other chemicals or through the chemical
barrel (due to its limited solubility, it will settle).
Excess Lime (lb/bbl) = 0.26 x (Pm - FwPf).

11) H2S Inhibitors



Zinc Oxide (ZnO)
SOURSCAV

12) Oxygen Scavenger


Sodium Sulfite

13) Bactericide


Bactron

14) Defoamers


Bara Defoamer

Clay Chemistry
Introduction
Types of Clay
Composition of Clay Mud
Cation Exchange Capacity (CEC)
Hydration of Clay
Clay particles Linking Process

Introduction






Clay may be added intentionally, such as
Bentonite, or it may enter the mud as a major
contaminant through dispersion of drill solids.
Clay minerals are fine-grained aluminum
silicate minerals having well-defined
microstructures.
A typical layered silicate mineral, for example,
is mica or vermiculite, which can be split into
thin layers along the cleavage planes.

Types of Clays

A.
B.

C.


1.

2.

3.

Categorization of Clay
Depending on the repeating units of the structure.
The ratio of silica to alumina layers such as 1:1,
2:1.
Whether they are layered or needle-shaped clay
There are a large number of clay minerals, but
those with which we are concerned in drilling fluids
can be categorized into three types.
Attapulgiteor, Sepiolite (Salt gels) ”Needle
Shaped”
Illite, Chlorite and Kaolinite (Non swelling or low
swelling) “Plate Like”
Montmorillonites (High swelling) “Plate Like”

Composition of Clay water
Mud
1.

2.

3.

Water Phase is the continuous phase of the mud it is common to
use a variety of brine solutions from salty to saturated as the base
liquid.
Reactive solids phase is composed of commercial clays ,
hydratable clays & shale from formation that are held in suspension
in fluid phase, these solids are treated chemically to control
properties of drilling fluid.
Inert solids refer to those solids in suspension that are chemically
inactive, these may be inert drill solids such as lime stone, dolomite,
sand and barite.

Cation Exchange Capacity


The compensating cations that are adsorbed on the unitlayer surface may be exchanged for other cations and
are called the exchangeable cations of the clay.



The Methylene Blue Test
(MBT) is an indicator of
the apparent CEC of a
clay.
When this test is run on a
mud, the total
methyleneblue exchange
capacity of all the clay
minerals present in the
mud is measured.



Cation Exchange Capacity
Cont’d




It is important to note that the test does
not directly indicate the amount of
bentonite present.
However, an estimate of the amount of
bentonite and solids in the mud can be
calculated if one considers that the
average drill solids have about 1/9 the
CEC of bentonite, and if the amount of
drill solids present in the mud is
calculated from a retort analysis.

Hydration of Clays




Bentonite crystals consists of 3 layers ( Si – Al - Si),
clay platelets are (-ve) charged and has a cloud of
cations associated with it, if these cations are sodium
the clay is called sodium montmorillonite and id
calcium it is called calcium montmorillonite.
When dry clay contacts fresh water, interlayer spacing
expand, and swell to the point where the forces
holding them together becomes weakened and
individual layers can be separated from the pack,
separating these packs into multiple layers is known as
dispersion this phenomena allow the clay to generate
viscosity. Sodium bentonite expands 4 times calcium
bentonite therefore will generate 4 times the viscosity.

Hydration of Clays Cont’d






The thickness of adsorbed water film is controlled
by the type and amount of cations associated with
the clay. Divalent cations (Ca2+ & Mg2+) increase
the attractive force between platelets decreasing
the amount of water that can be adsorbed, while
monovalent cations like Na+ generates less
attractive force allowing more water to penetrate
between platelets (Sodium bentonite swells 4
times Calcium bentonite).
Chemical reaction between clay & (K 3+ ) ions is
unique compared to other ions. There are 2 ways
that K can become associated with clay minerals
(Ion Exchange & Ion Fixation).
Ion fixation will occur in clays with high layer
charge, this increases the selectivity of the clay to
the K ion by order of magnitude.

Clay Particles Linking
Process
1.

2.

Aggregation: Leads to the formation of thicker plates
or packets this decreases the number of particles and
causes a decrease in P.V. It can be caused by the
introduction of divalent cations to the drilling fluid
such as Ca2+ either by addition (lime or gypsum) or
contamination (anhydrite or cement) viscosity will
initially increase then decrease by time and temp.
Dispersion: Leads to a greater number of particles
and to increase P.V , clay particles( platelets) are
normally aggregated before they are hydrated. Degree
off dispersion depends on high electrolyte content,
time, temp. & exchangeable cations and low salinity
and hardness.

Clay Particles linking Process
Cont’d
3.

4.

Flocculation: Leading to the formation of a house of
cards structure, this causes increase in viscosity,
gelation and fluid loss. Anything that increases the
repelling forces between particles or shrinks the
adsorbed water film, such as the addition of divalent
cation or increasing the temp. promotes flocculation.
Deflocculation: Is the dissociation of flocculated
particles the addition of certain chemicals to the mud
neutralizes the electrochemical charges on the clay, this
removes the attraction forces that results in bonding
between clay particles. Since deflocculation results in a
reduction in viscosity deflocculating chemicals are
usually referred to as mud thinners. Deflocculation also
aids in allowing the clay particles to lay flat in the filter
cake to reduce fluid loss.

Mud Contaminants
1.
2.
3.
4.
5.
6.

Low Gravity Solids (LGS)
Salts (CaCl2, MgCl2, NaCl)
Cement & Lime
Anhydrite & Gypsum
Carbonates & Bicarbonates
Hydrogen Sulfide Gas

1) Low Gravity Solids


Effect: Thicker and softer filter cake.
Increase in the overall reology (PV,YP and Gel
strength)



Particle Classification:
1) According to SG

A) High Density Solids >4.2
example: Hematite=5

Barite= 4.2

B) low Density Solids (1.6 – 2.9)
example: Bentonite = (2.3-2.7)
Limestone = (2.7-2.9)
Diesel = 0.85
Sand = (2.6-2.7)

Low gravity Solids Cont’d


2) According to Particle Size

Particle Size (micron)
Classification
Mesh
Screen
>2000
Coarse
10
2000-250
Intermediate
60
250-74
Medium
200
74-44
Fine
325
44-2
Ultra Fine
2-0
Colloidal
Note:
1)The Smaller the particle, the more effect it has on the fluid.
2)The smaller the particle the more difficult it is to remove or
control its effect. Colloidal particles dramatically effect the
fluid.

Low Gravity Solids Cont’d

2) Salts






Influence: Chloride ions increases the salinity,
causing an increase in mud weight.
Indication: Chloride ion test.
Calcium, Potassium & Hardness test.
Fluid Loss increase.
pH may decrease.
Foams may appear on the surface.
Treatment: Dilution to decrease chloride, and
precipitate the cation.
Mg : Increase pH over 9.
Na : Replace by Ca.
Ca : Add Soda ash.

3) Cement & Lime






Influence: Large increase in pH.
Polymer will burn resulting in a large
decrease in AV, PV, YP and gel strength.
Indication: pH meter.
Ca test.
API fluid loss decrease.
V-G meter parameters drop.
Solution: Dilution to decrease pH.
Add Soda ash or Sodium bicarbonate.
Regain all lost parameters.

4) Anhydrite& Gypsum
(CaSo4)






Influence: Gel strength will increase
pH will fall
Fluid loss may decrease
Calcium will increase
Indication: pH meter.
Ca test.
API fluid loss test.
V-G meter parameters drop.
Solution: Add soda ash.

5) Carbonates &
Bicarbonates


Influence: Decrease Ca content.
Increase in YP and 10min Gel
strength.



Indication: Ca test.
V-G meter parameters.
Pm, Pf and Mf tests..



Treatment:

Add calcium hydroxide (lime).

6) Hydrogen Sulfide


Influence:



Indication:



Solution:

Mud Types

Water Based Mud (WBM)
Oil Based Mud (OBM)

Water Based Mud (WBM)
1.
2.
3.

4.
5.
6.

Spud Mud
Emulsion Mud
Low Solid Non Dispersed Mud
(LSND)
KCl Polymer Mud
Heavy Weighted Mud
K- Formate Mud

1) Spud Mud
For 100 bbls
1 Sac Soda Ash (Ca+ ppt, and flocculation).
1 Big bag Bentonite.
1.5 Sac Lime (add when drilling start).
5-6 Sacs Starch (if necessary)


Density: 63 pcf
Viscosity: 60-80 sec.
pH : 9 – 10
API: 10 - 12

Gel Slips
For 100 bbls
1 Sac Soda Ash.
1.5 Big bag Bentonite.
2 Sac Lime.
0.5 XC Polymer


Density: 63 pcf
Viscosity : 100 – 150 sec.
pH : 10 - 11

2) Emulsion Mud
For 1 bbl
Water
0.53 bbl
Starch
2 Lb
Diesel
0.45 bbl
SafeSurf 0.84 gal
Lime
0.5 Lb
Barite
(as desired)


PV = 12
YP = 16
GS = 2/6
API = 6-8
pH = 9-10

3) Low Solid Non Dispersed
Mud
For 1 bbl
Water
Bentonite
Emfloc
XC-Polymer
12
Lime


0.95 bbl
5 Lb/bbl
6 Lb/bbl
0.75- 1 Lb/bbl
0.5 Lb/bbl

PV=18 - 24
YP=24 - 26
GEL sec=2-4
GEL min=6API = 6

4) KCL Polymer Mud
For 1 bbl
Water
0.79 bbl PV = 24
XC Polymer
0.5-1 Lb YP = 22-25
Starch
4–6 Lb GS = 6/12
PAC-LV
0.5-1 Lb API = 3-5
KCl
35 Lb HPHT =14
KOH
0.25 Lb Ph = 9-10
Lime
0.25 Lb MBT = 6
Barite
(as needed) Cl = 57,000
Sodium Sulfite 0.25–0.3 Lb
Soltex
2–4 Lb


5) Heavy Weighted Mud










For mixing 200 bbls of heavy weight mud
Add 160 bbls water
2 Soda Ash
¼ Bentonite
½ XC-Polymer
1 Lime (check viscosity over 40 before
barite)
15 Emfloc
Barite = (needed weight-63) x 10 Lb/bbl x 160
bbl

5000 Lb

6) K- Formate Mud








Usually used in Pay Zones, no Barite
added.
1 IBC weights 97.
1 IBC contain approximately 6.3 bbls.
Monitor the pH carefully to minimize
corrosion risk.
Order Densometer for CaCO3 test.

K-Formate Mud Cont’d



Use Mudware to mix the desired weight.
Recipe per 100 bbl
2 PAC UL
2 PAC R or ANTISOL
1 XC Polymer till Viscosity reach 40-45
1 Soda Ash
1 Sodium Bi-Carbonate
1500 lb Marble “F”

CaCO3 Content











Add 1 ml of mud+9 ml of (2N) HCl “shake”
+90 ml deionized water in a 100 ml beaker
Take 10 ml sample+0.5 ml (8N) NaOH.
pH should be 14, else add more NaOH.
Add Caliver 2 indicator and titrate with
EDTA (0.1M) or (0.01M).
CaCO3(g/l) = ml EDTA ( 0.1M ) x 100
ml EDTA ( 0.01M ) x 10
CaCO3 % = CaCO3(g/l) / 27
CaCO3(ppb) = CaCO3(g/l) x 0.35

Low Gravity Solids Content


L.G.S %= Mud SG – Filtrate SG x 100
CaCo3 SG – Filtrate SG
-Mud SG= Mud Density (pcf) / 62.3
-Filtrate SG= Densometer readings
-CaCo3 SG= 2.7



L.G.S (g/l)= L.G.S % x 27



L.G.S (ppb)= L.G.S (g/l) x 0.35

Drilled Solids Content


D.S (g/l) = L.G.S (g/l) – CaCO3 (g/l)



D.S (ppb) = D.S (g/l) x 0.35



D.S % = D.S (g/l) / 27



Brine Content = 100 – L.G.S %

Spacers
BJ Spacer
ARAMCO Spacer

BJ Spacer








Water
Caustic (pH=9 at least)
Lb/bbl
XC polymer (1hr/sac)
Defoamer(FP-9L or Fp-12I)
Barite

0.4 bbls
0.1

S-301

1 gal/bbl

0.75 Lb/bbl
0.1 gal
as needed

ARAMCO Spacer






The normal mud used, except that
a higher weight is required.
So add barite till reaching the
desired weight as per game plan.
If used for Cement job make sure
no salts are present as salts helps
Cement to shock faster.

Calculations


Volume



Time



Velocity
Pressure



Active/ Inactive Tanks Volume
Hole Volumes with/without D.S
Total Circulating Volume
Total Mud Volume
Circulation Time
Bottoms Up
Annular
Hydrostatic Pressure
Equivalent circulating Density

Volumes


Hole Volume (bbl):
(IDx2 x Lx)+(IDy2 x Ly)/1029.4



Active Pits:
Vol.suc1,2,3 + Vol. intermediate + Vol.
Inactive Pits:
Vol.slug+Vol.res1,2,3,4
Total Circulating Volume:
Hole Volume+ Active Pits
Total Mud Volume:







settling

Total circulating Vol.+ Inactive Pits+ (Vol.Mixed+ Vol.Dilution)
–(left in hole+ Dumped+ Down hole losses+ S.C.E.
loss).

Time


Circulation Time (min): Volume system (bbl)
Pump o/p (bbl/min)



Bottoms up (min) : Volume annulus (bbl)
Pump o/p (bbl/min)

Velocity


Annular Volume (bbl): IDCSG2 – ODDS2 x L
1029.4



Annular Velocity: Pump o/p (bbl/min)
Annular Volume

Pressure


Hydrostatic Pressure (psi):
Mud weight (Lb/Gal) x TVD (ft) x 0.052



Equivalent circulating density (ECD):
Annular Pressure (psi)
0.052 x TVD (ft)

Main Conversions







42 gallons = 1 barrel
5.615 ft3
= 1 barrel
1
ft3
= 7.48 gallons
8.345 Lb/gal = 1 SG (specific
gravity)
62.5 pcf
= 1 SG (specific
gravity)

Drilling Problems
1.

Lost Circulation

2.

Stuck Pipe

3.

Formation Damage

4.

Corrosion

1) Loss Circulation
Type
Cause
Effect
Treatment
Special Pills

Loss Circulation
Types: Partial or Complete
Cause: Due to Permeable, porous or Fractured formations
(natural or caused by excessive mud pressure).

Effect: When it takes place and not treated may induce
formation fluids from other zones previously controlled
by drilling fluid to flow into the wellbore resulting in a
kick or blowout and may induce previously stable
formations to collapse into the wellbore.

Treatment: Maintain minimum equivalent circulating
density.
Avoid pressure surges.
Use LCM.

Loss Circulation Pills


LCM Pills



X- Link



Barite Plug



Marble Pill



Gunk Squeeze



FUSE IT

LCM Pill










Water + Viscosifier or active mud
For example if 200 Lb/bbl LCM is needed
75 Lb Mica Coarse
25 Lb Mica Fine
50 Lb Wallnut shell
50 Lb Cotton seed
Then multiply by volume required “number of sacs”.
Then divide by Sacs/Pallet “number of pallets”.
Notes:
LCM material added from above, add have the mud
then the remaining half after mixing LCM materials.

X-Link Pill









Add 100 bbls of water
3 sacs Soda Ash
1 Drum Defoamer
26 X-link RTR cans
60 sac X-link
Barite till weight reached
60 sacs X-link
Notes:
-Clogging of the hopper line is usual, try adding
the X-link sacks slowly to delay or prevent this
problem.

Barite Plug











Mixed in cement tanks
Approximately 200 bbl are needed.
Pilot test should be made to test Barite
settling.
Mix in this sequence, formulation / barrel
0.54 bbl of water
1 Lb Caustic soda
8 Lbs lignosulfonate (Spersene or R-8)
Lots of Defoamer
690 Lbs Barite

Marble Pill








Water
XC-Polymer (0.75-1.25)Lb/bbl
Marble Chips 70Lb/bbl
Marble Coarse 70Lb/bbl
Marble Medium 60Lb/bbl
Notes:
-Should be mixed then contained in the batch

mixer “cement tanks”.
-Viscosity should be high to be able to suspend
the marble chips (3 Lb/bbl).

Gunk Squeeze




Mud weight
59 pcf
73 pcf
90
pcf
Water (bbl)
0.660
0.628
0.582
Spersene (lb)
3.5
3.5
3.5
Caustic soda (lb)
1.5
1.5
1.5
Geltone (lb)
220
150
100
Barite (lb)

175
370
Notes:
-If too much foams appeared add half Geltone II then half
barite then remaining Geltone II then remaining barite,
add defoamer ”no problem”.
-This pill is more effective when diesel is added than oil.

FUSE IT










Water
Ca++ Treated Mud
Spacer BDF 384
FUSE IT
Pill
Spacer BDF 384
Water

25 bbl
15-20 bbl
6.5 bbl + Barite Volume
6.5 bbl + Barite Volume
200 bbl
6.5 bbl + Barite Volume
50 bbl

Ca++ Treated Mud to chase Pill

Cont’d FUSE IT








Pill:
40 Lb/bbl Steel Seal (resiliency graphite material)
100 Lb/bbl BDF 392 (resiliency graphite material)
60 Lb/bbl Marble Chips
Spacer:
if FUSE IT unweighted, use unweighted spacer.
if FUSE IT is weighted, add Geltone II then add Barite.
FUSE IT:
S.G =1.2, density=56pcf, can be weighted to 112pcf
Treated Mud:
Soluble calcium less than 200 mg/l, treat if more.

2) Stuck Pipe
Causes
Treatment

Causes
a)
b)
c)
d)
e)
f)

Poor Hole Cleaning
Sloughing Shale
Differential Pressure
Key Seating
Packing off
Under Gauge Hole

a) Poor Hole Cleaning/ b) Sloughing
Shale








The key to a muds lifting capacity is indicated
by the appearance of formation solids coming
over the shale shaker.
Rounded edges on large cuttings show that
these pieces have been tumbling in the hole
for a long time and are not being lifted out
effectively
An unusually large amount of shale indicates
that the hole is washing out.
Long splinters or fissured shale may indicate
that the shale is "popping" into the wellbore,
indicative of over pressured shale.

Poor Hole Cleaning Results
in




Large pieces of rock, which are not
removed from the hole often, become
lodged between stabilizers or reamers
and the hole. If this occurs while drilling,
the torque required to rotate the drill string
will increase rapidly.
If pieces of rock become lodged while
making a connection or during a trip, the
additional pull of the hook will appear as a
drag. A sudden increase in pump pressure
can sometimes be observed, as bridges
form and restrict mud flow up the annulus

Methods of Prevention







Increase the viscosity and particularly the Yield
Point of the mud. There is no exact yield value that
can be specified, as every situation is unique, but
generally an upper Yield Point of ±30 lb/100ft 2 should
clean most cuttings from the wellbore.
Use viscous pills to sweep the hole when drilling.
Increasing the mud density may be beneficial in
some cases to balance the pore pressure of the
shale, and to help hold formations in place to
stabilize the wellbore.
Reducing the water loss may help to minimize
the hydration of shales and wetting along bedding
planes which could disperse and slough into the
wellbore.

c) Differential Pressure








The force that holds the pipe against the wall of the
borehole due to the differential pressure between
the hydrostatic pressure of the mud column and
the formation pressure.
The pressure differential acts in the direction of the
lower pressure in the formation.
This pressure pushes the pipe toward the
permeable formation. As the pressure differential
gets larger, the force exerted on the pipe gets
larger.
Differential stuck pipe occurs most often at a point
next to the drill collars. This is due to the drill
collars being larger; hence more surface area is in
contact with the side of the wellbore.

Prevention








The mud density should be maintained as low as
practical, taking into consideration wellbore
stability and potential well control problems
Maintain a low fluid loss and pay particular
attention to the filter cake; i.e.: it should be thin,
tough and resilient.
In areas where differential sticking is prevalent,
the high temperature / high pressure fluid loss
should be maintained below 20 ml.
Adding 2-8% lubricant to the mud system gives
preferential oil wetting to the drill string, thereby
allowing better lubricity and minimizing the
possibility of stuck pipe.

Action (Freeing the Stuck
Pipe)


When the drill string become stuck, it is
imperative to act quickly as the sticking
coefficient increases with time.



A grease pill is the most effective solution.



Generally enough pill is mixed up to cover the
entire length of the drill collars, plus an excess of
(1.5 bbls) to be left on top of the collars, and
another (20 bbls) to be left inside the drill collars.

Grease Pill Recipe

d) Key Seating


Keyseating is a situation
frequently encountered
in deviated or crooked
holes when the drillpipe
wears into the wall. The
normal drilling rotation
of the drillstring cuts
into the formation wall
in deviated areas where
the drillpipe tension
creates pressure against
the sides of the hole.

Action




Once a keyseat is
formed, the best solution
is to ream out the smalldiameter portions of the
hole with reaming tools.
This action will solve the
immediate stuck-pipe
problem, but the keyseat
can be formed again
unless preventive steps
are taken.

e) Packing Off




1.
2.
3.

Drilling-fluid systems with poor
suspension characteristics exhibit
strong packing-off tendencies
Factors that can lead to caving of the
formation include:
Pressure imbalance
Shale hydration
Bottom hole assembly striking the wall

Action


The Solution is to
increase the
suspension
characteristics of the
mud (YP and gel
strength).

f) Under Gauge Hole




1.
2.

3.

Under gauge hole is a condition where the
borehole is smaller than the bit diameter
used to drill the section.
Under gauge hole can result from any of
the following causes:
Plastic flowing formations
Wall-cake buildup in a permeable
formation
Swelling shales

Plastic Flowing Formations








Under gauge hole is a common
problem when drilling a thick salt
section with an oil mud.
The salt can flow into the borehole and
make the section under gauge.
When plastic salt formations exist, they
are usually below 5,000 feet.
Spotting fresh water is the best way to
free the pipe from a plastic salt formation.

Wall cake Build Up




1.
2.

Wall cake buildup occurs when the
drilling fluid has poor filtration control
across a permeable zone.
Excessive wall-cake buildup can also
be caused by:
High percentage of low-gravity solids
High differential pressures (excessive
mud weights)

Summary of Stuck Pipe
Cause
1. Poor Hole Cleaning
2. Sloughing Shale
3. Differential sticking
4. Keyseating
5. Packing Off

6. Under gauge hole

Steps to free
Increase YP
Use High Vis Pills
Increase Mud Weight
Decrease Fluid Loss
Reduce mud weight.
Use spotting fluid.
Ream the keyseat.
Increase YP
Increase mud weight
Back off and wash over
Increase mud weight
Ream and clean

3) Formation Damage
Common Mechanism
Drill In Fluids

Formation Damage
Common Mechanisms










Mud or drill solids invading the formation matrix,
plugging pores.
Swelling of formation clays within the reservoir,
reducing permeability.
Precipitation of solids as a result of mud filtrate
and formation fluids being incompatible.
Precipitation of solids from the mud filtrate with
other fluids, such as brines or acids, during
completion or stimulation procedures.
Mud filtrate and formation fluids forming an
emulsion, restricting permeability.

Prevention
Using a Drill In fluid

1) Drill In Fluids should contain nondamaging polymers, bridging agent.
2) Should have superior regain
permeability.
3) May have shale or clay inhibitors.
4) Should be easy to clean up.

4) Corrosion
Definition
Causes Affecting Corrosion
Types of Corrosion
Corrosive Agents

Corrosion








Corrosion is the destruction of metal
through electrochemical action between
metal and its environment.
Corrosion can be costly in terms of
damage to pipe and well parts and can
even result in the loss of an entire well.
About 75 to 85 percent of drillpipe loss
can be attributed to corrosion.
Other areas affected by corrosion
include pump parts, bits, and casing.

Factors Affecting Corrosion










Temperature. Generally, corrosion rates
double with every 55°F increase in
temperature.
Velocity. The higher the mud velocity, the
higher the rate of corrosion due to film erosion
(oxide, oil, amine, etc.).
Solids. Abrasive solids remove protective films
and cause increased corrosive attack.
Metallurgical factors. Mill scale and heat
treatment of pipe can cause localized
corrosion.
Corrosive agents. Corrosive agents such as
oxygen, carbon dioxide, and hydrogen sulfide
can increase corrosion and lead to pipe failure.

Types of Corrosion
1.

Uniform corrosion
Even corrosion pattern over surfaces

2.

Localized corrosion
like corrosion pattern over surfaces

3.

Pitting
Highly localized corrosion that results in the
deep penetration of surfaces

Corrosive Agents







Oxygen
Hydrogen sulfide
Carbon dioxide
Bacteria
Dissolved salts
Mineral scale

Oxygen




Oxygen acts by removing protective films;
this action causes accelerated corrosion
and increased pitting under deposits.
The four primary sources of oxygen are:
–Water additions
–Actions of mixing and solids-control equipment
–Aerated drilling fluids
–The atmosphere



Treated by adding an oxygen scavenger.

Hydrogen Sulfide


Hydrogen sulfide can enter the mud
system from:
–Formation fluids containing hydrogen
sulfide
–Bacterial action on sulfur-containing
compounds in drilling mud
–Thermal degradation of sulfur-containing
drilling fluid additives
–Chemical reactions with tool-joint thread
lubricants containing sulfur

Hydrogen Sulfide Cont’d









Hydrogen sulfide is soluble in water.
Dissolved hydrogen sulfide behaves as a
weak acid and causes pitting.
Hydrogen ions at the cathodicareas may
enter the steel instead of evolving from the
surface as a gas.
This process can result in hydrogen
blistering in low-strength steels or hydrogen
embitterment in high-strength steels.
Both the hydrogen and sulfide components
of hydrogen sulfide can contribute to
drillstring failures.

Treatment
Hydrogen sulfide corrosion is mitigated by
increasing the pH to above 9.5 and by using
sulfide scavengers and film-forming
inhibitors.




Sulfide scavengers include Zinc Carbonate,
Zinc Oxide and other specialty chemical
products
Most film forming inhibitors are amine
inhibitors, many are available

Carbon Dioxide










Carbon dioxide is found in natural gas in
varying quantities.
When combined with water, carbon dioxide
forms carbonic acid and decreases the water's
pH, which increases the water's corrosivity.
While carbon dioxide is not as corrosive as
oxygen, it can cause pitting.
Maintaining the correct pH is the primary
treatment for carbon dioxide contamination.
Either lime or caustic soda can be used to
maintain pH.

Bacteria








Microorganisms can cause fermentation
of organic mud additives, changing
viscosity and lowering pH.
A sour odor and gas are other indicators
that bacteria are present.
Degradation of mud additives can result
in increased maintenance cost.
Microbiocidesare used to control
bacteria in drilling environments.

Dissolved Salts






Dissolved salts increase corrosion by
decreasing the electrical resistance of
drilling fluids and increasing the
solubility of corrosion by-products.
Some of these byproducts can cause a
scale or film to form on the surface of
the metal.
Amine filming agents added to the
metal will aid in reducing corrosion due
to dissolved salts.

Drill String
Drill Pipes
HWDP
Drill Collars
Stabilizers
Bits

Formations

Section 1
Surface Holes

Surface Holes






Drill this section with Spud Mud
(Fresh Water + Prehydrated Bentonite
+ Lime)
HEC may be added to develop
additional viscosity.
Prepare the spud mud in advance to
allow enough time for the mud to
develop adequate gel and viscosity.

Surface Holes






Before mixing the spud mud make sure
that the chloride conc. is less than 10,000
mg/l.
If water is sweet, mix 15 Lb/bbl of
bentonite other wise viscosity will be to
much. At The same time mix one tank with
25 Lb/bbl just in case.
Lime can be added from the hopper with
no fear on the spud mud, but if using a
polymer mud (upcoming sections.), lime is
poured slowly from a barrel so as not to
burn the polymer.

Surface Holes




Add water to the shaker pit to
accelerate settling of fine solids in the
sand trap.
Always have your Hi- Vis ready, with
adequate volumes, especially if drilling
in a loss circulation formation.

Section 2
Loss Circulation Formations

Loss Circulation
Formations


If loss of circulation occurs, switch
from spud mud to water and
gelslips (heavy weighted spud
mud) “Hi- Vis pills” pumped at
intervals to clean the hole and
pump mud caps from the annulus
every interval.

Section 3
Shale Formations

Shale Formations






At this section do not use spud mud and use
any polymer mud (ex: KCl polymer mud), as
bentonite has a very high fluid loss
increasing possibility of shale sloughing and
makes a thick filter cake.
Add Black Nite and Soltex for pore paving
and Glycol for dehydration and KCL to
prevent bentonite in the formation from
swelling.
Add 15Lb/bbl Wall nut shell to the Hi- Vis to
minimize chances of bit balling.

General Notes
About Cementing and
Handling

General Notes on Casing







After casing and cement, clean trip tank,
prepare short system to drill water.
When running a cement job always check
barrels of cement pumped and displaced.
Check salinity of water before cementing.
Salts helps cement to shock rapidly, only
added in top jobs. It is prohibited to use it
in spacer.

General Notes on Handling






For preparing a new section, always assume
you will mix 5000 bbls of mud incase of
losses.
Be careful, check with derrikman when to fill
the trip tank for the driller to pump mud cap.
Always use a lesser amount of chemicals than
calculated then add gradually to control
properties, also putting in mind that we
sometimes use more than calculated because
of lack of purity in chemical products.

General Notes on Handling

1.


1.

2.
3.

Gain in pressure means:
Blocking (either by shale, or drilled
solids or formation collapse).
Loss in pressure means:
One or more nozzle fell (pressure drop
is stable doesn’t increase or decrease).
Circulation loss (no return on shaker).
Drill pipe cracked (pressure drop will
increase gradually).

Terminology








Atomic Number= number of electrons orbiting
the nucleus.
Atomic Weight= sum of protons + neutrons in
the nucleus.
Isotopes= Same element having different
number of neutrons, therefore possessing
different atomic weight.
Valence Number= If an element has 1 e’ to
give, it valence of +1, if an element has 1 e’ to
gain, it valence is -1. The sum of all valence
numbers of all the elements in a compound must
be equal to zero.

Cont’d








Radical= Combination of elements that
behaves as if it were a single element. Ex:
CO3--,HCO3-, OH-, SO4--, NO3-.
Formula weight= sum of all atomic weights
present in a compound.
Mole= quantity of a compound equal to its
formula weight as expressed in grams.
Equivalent weight= is equal to the formula
weight of that compound divided by its net
positive valence expressed in grams.

Densities









mg/l = 0.001 grams of a substance in one liter
of solution.
mM/l= moles of solute/ liter of solution = mg/l
ppm= 1 gram of solute in 1,000,000 ml = mg/l
This assumption holds true for most mud
engineering purposes, except in high chloride
concentrations, ppm= mg/l + SG of solution.
epm= 1 equivalent dissolved in 1,000,000 ml
of sol.
Normality= number of equivalents of solute /
liter of solution.
1 N of sulfuric acid = 49 grams in 1 liter.

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