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Drilling Fluids Familiarisation

A Half-Day Seminar on M-I SWACO

Drilling Fluid Systems and Products

for the National Iranian Drilling Company

Thursday 8th December 2005

Presented by

Mark Sanders

UK Technical Services

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Classification of Drilling Fluids Air / Mist /Foam Water-based fluids

– ‘Spud Muds’– Bentonite Fluids (including DRILPLEX)– Polymer Fluids– Glycol Fluids (GLYDRIL and ULTRADRIL)– Silicate fluids (SILDRIL)– High Temperature Fluids

Oil-based fluids– Invert Emulsion Fluids (VERSACLEAN)– ‘All Oil’ fluids (TRUDRIL)– High Temperature Fluids (VERSATHERM)

Synthetic-based fluids– Ester – IO (NOVAPLUS)– LAO (NOVAPRO, NOVATEC and RHELIANT)– Paraffin (PARADRIL, PARALAND)– High Temperature Fluids (PARATHERM)

Brines

• Reservoir Drilling Fluids FLOPRO NT DI-PRO FAZEPRO

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Oil-Based Drilling Fluids Oil Phase

– Diesel – low-toxicity mineral oil - paraffin - ester - olefins Brine Phase

– CaCl2 or NaCl Emulsifiers / Wetting agents

– fatty acids - amidoamines– Imidazolines

Density – Barite - Calcium Carbonate– Hematite - Ilmenite

Viscosity – Organoclays– Rheological modifiers

Fluid Loss FL 170, Synthetic Polymers

Alkalinity – Lime

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OBM Tests and Properties Density and Viscosity

– As per WBM but always measure viscosity at constant temp (usually 500C)

Oil / Water ratio– Ratio of volume of oil phase to water expressed as % e.g., 70/30– Data taken from the retort

Electrical stability (Es)– Voltage required to pass a current through the mud– Measured at 500C. Typical values 300-1000V.– Guide only. Trends are important. Value depends mainly on O/W ratio

Water phase salinity (WPS)– Grams chloride per litre water– % w/w is preferred

HPHT Fluid Loss Alkalinity

– Measurement of Lime content by titration on whole mud

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Water Phase SalinityWater Activity ConceptAw is relative vapour pressure

Not enough saltCuttings soft and mushy

Possibly water-wet

Tight hole on trips

Too much saltCuttings hard, brittle and splintery.

Cavings

Coffee grounds-dry rounded cuttings reground in the annulus

Care - don’t jump to conclusions

0.95

0.90

0.85

0.80

0.75

0.70

1000 2000 3000 4000 5000 8000 10000

A f

DEPTH ( FT )

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Water Activity

Small scale strain test with Pierre 1 shale

-0.1

-0.05

0

0.05

0.1

0.15

0 200 400 600 800 1000 1200

Time (mins)

% L

inea

r ex

pan

sio

n

0.95 Aw

0.85 Aw

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OBM - HSE Considerations

1. All oils are potentially harmful and skin contact should be avoided

2. Emulsifiers are powerful surfactants that can defat the skin. Most are irritants. Handle with care.

3. Calcium chloride and lime are eye and skin irritants.

4. Contaminated overalls should always be changed.

5. Wear gloves or use barrier creams to protect the skin (but do not use barrier cream and gloves).

6. Ventilation is important to reduce oil mist/vapour. If possible chose a base fluid with a flash point well above the maximum anticipated flow line temperature.

7. No-smoking and hot work permit regulations must be observed.

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OBM - Engineering

Emulsion and oil-wettingEs, water in filtrate

Drilling sand and shale

Drilling salt

Solids control equipment

Rig preparation

Need to minimise surface losses and transfer losses

Displacements

Barite sag

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Water-based Fluids Water

– Freshwater - seawater - KCl - Saturated NaCl Density

– Barite - Calcium Carbonate -Iron Carbonate - Hematite - Ilmenite Viscosity

– Biopolymers - CMC - PAC - Guar - Bentonite (or other clays) - synthetic polymers Dispersants

– modified polyacrylates - lignosulphonates - Fluid Loss

– synthetic polymers - carboxymethyl celulluse - polyanionic cellulose - starch - bentonite - modified lignites (HT) -asphalt (HT) - resins (HT)

Inhibition– Glycols - silicate - KCl - Gypsum – Ultracap - Ultrahib - and other

pH Control– NaOH – MgO - Ca(OH)2 - Citric acid - NaHCO3

Other– Bactericides - lubricants - LCM - polymer temperature stabilisers - corrosion

control (oxygen scavengers, filming agents)

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OBM vs WBM

Lubricity

Tolerance to Contaminants

Environmental Footprint

Drilling Performance

Corrosion Inhibition

Thermal Stability

Shale Inhibition

Formation Protection

Oil Based MudEster Based SOBMLAO SOBMKCl/PHPAWBM Glycol System

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GLYDRILGLYDRIL

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GLYDRILGLYDRIL

STANDARD MUD SYSTEMSTANDARD MUD SYSTEM

KCl/Glycol/Polymer systems used as standard WBM for bothexploration and production drilling.

High success rate with few wellbore problems. Low fluid costs associated with high mud re-use.

Adaptable fluid formulations to meet drilling and environmental demands

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Glycol - Shale Inhibition MechanismGlycol - Shale Inhibition Mechanism

Mechanism for shale inhibition not well understood

Glycols are strongly adsorbed by clay

Pore plugging from clouding effect

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• >400 Wells Drilled>400 Wells Drilled• Highest Temperature - 412°FHighest Temperature - 412°F• Longest Horizontal - 6567 ftLongest Horizontal - 6567 ft• Longest step out - 7827ft 17 1/2” hole at 50Longest step out - 7827ft 17 1/2” hole at 50oo

• Fastest ROP - 4785 ft 12 1/4” hole in 24 hrsFastest ROP - 4785 ft 12 1/4” hole in 24 hrs• Highest Overbalance - 4500 psiHighest Overbalance - 4500 psi• Drilled - Reactive Clays, Shale, Sandstone, Drilled - Reactive Clays, Shale, Sandstone,

Field Use of Glycol Fluids

Siltstone,Limestone, Carbonates, Salt, Anhydrite, Siltstone,Limestone, Carbonates, Salt, Anhydrite,

Zechstein, CoalsZechstein, Coals• Must be matched by good solids-controlMust be matched by good solids-control

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NaCl or KCl Brine DUOVIS PAC R and/or UL Starch HIBTROL Glycol @ 3 – 5 % v/v pH Control Weighting Agent

GLYDRIL System Composition

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Benefits Environmentally acceptable Safe Handling for Rig Crews Good Shale inhibition Good wellbore stability Good Lubricity Lower Cost per Ft

GLYDRIL

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SILDRILSILDRIL

SILDRIL –Inhibitive WBMSILDRIL –Inhibitive WBM

Silicate-based Fluids– essentially a polymer-

based system– utilizes silicate

chemistry for inhibition– Used primarily for

drilling troublesome shale sections

SILDRIL - Inhibitive WBMSILDRIL - Inhibitive WBM

BEFORE

AFTER

Strongly minimises shale hydration and improves formation integrity

In some applications, these systems can be used as

an economic and environmental replacement for oil-base muds

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Soluble Silicates Soluble Silicates are the

metal salts of Silica Acid that exist in multiple polymeric forms in solution. Amorphous solids and powders are also manufactured.

All silicates contain three basic components:– Silica -- SiO2 (Sand)– Alkali -- Na2O or K2O (Soda

Ash or Pot Carb)– Water -- H2O

OSi

OSi

OSi

O

O

O

O

O

O

O

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pH/Alkalinity

Silicates are alkaline materials (ie. pH range from 11.0 to 13.5)

Silicate species need a pH >10.7 to remain soluble in solution

pH of silicate solutions is maintained until almost complete neutralization

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Mechanisms for Shale Stabilization

Polymerization in the shale pores

Precipitation– Soluble Silicates can react with all multivalent cationic metal ions to

form the corresponding insoluble metal silicate, depending on reaction conditions

Direct bonding of shale substrate

There are many theories as to the actual mechanisms at work

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Mechanisms for Shale Stabilization

The glassy nature of silicates imparts strong and rigid physical coating to surfaces

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0

10

20

30

40

50

60

70

80

90

100

% R

EC

OV

ER

Y

FW /

PO

LYP

LUS

KC

l / P

OLY

PLU

S

CA

LDR

IL

GLY

DR

IL

GLY

DR

IL P

LUS

SIL

DR

IL

SIL

DR

IL /

GLY

DR

IL

SIL

DR

IL /

SIL

-LU

BE

INV

ER

T E

MU

LSIO

NFL

UID

REACTIVE SHALES (High Smectite Content)

HIGHLY DISPERSIVE SHALES

SILDRIL Inhibition

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Silicate-base fluids were used decades ago. Now, proper formulation and engineering design allow their successful use.

SILDRIL Composition

• Silicate - primary shale inhibitor (provides water barrier)• Potassium - secondary shale inhibitor (reduces swelling)• Biopolymer - rheology control• PAC / Starch - provides fluid loss control• Compatible with conventional anionic and non-ionic fluid

additives• Used with mono-valent salts (KCl & NaCl)

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Rheology Xanthan for 6/3 RPM readings

Fluid Loss ±3.0 ppb PAC U/L & Reg (9 – 6 cc)

Silicate 5 - 8% by vol.

KCl 25 - 35 ppb

MBT Generally low (highly inhibitive)

pH 11 - 12 (natural level)

Hardness Zero (positive Silicate)

Corrosion Inhibitors not necessary

SILDRIL™ Engineering Guidelines

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SILDRIL Experience

0 20 40 60 80 100 120 140 160

AlgeriaAustralia

AustriaCanada

DenmarkEgypt

GermanyIndia

IndonesiaIreland

IsraelMalaysia

New ZealandNigeria

NorwayOman

PakistanQatar

RussiaSyriaUAE

UKUS

Viet Nam

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SILDRIL - Experience

Minimum down-time attributed to formation chemical instability Minimal “bit balling” problems In-gauge wellbore for optimum cement jobs Excellent cuttings integrity for geology interpretation and for

effective removal by the solids control equipment High solids removal efficiency, comparable to invert emulsion

fluids Minimal environmental impact: uses all “environmentally friendly”

products Minimal environmental impact: reduced discharges. Low dilution rates, which are also beneficial with regard to waste

control and management. Ease of formation identification.