6.1 Drilling Fluids Part I

Quartz School for Well Site Supervisors Module – 6 Drilling Fluids & SCE

Section – 1 Water Base Muds

Introduction to Drilling Fluids Technology Contents: • Overview of Water & Oil Base Fluid Technology • Drilling Technology & Drilling Fluid Selection • Drilling Fluid Related Problems • Understanding/Using the Mud Report • Introduction to Solids Management & Waste Management

Introduction to Drilling Fluids Technology Your Objectives……………….

• At the end of this course,YOU will be able to: • Define Fluid Functions • Understand Basic Fluid Composition • Correlate Fluid Design and Drilling Objectives • Recognize Fluid-Related Problems • Use a Daily Mud Report to Determine Drilling & Fluid Performance and Recognize Problems • Understand the Basics of Fluids and Solids Management

History 1900

Water and Clays No control of properties

Weighting Agent (‘40’s) Controlled Filtrate(‘50/’60’s) Polymers ( 70 ’s) • Mineral oils(‘80’s) • Synthétics (‘90’s)

Water base muds Cellulosic polymers PHPA systems Formation compatibilty Environmental

Functions of Drilling Fluids Drilling fluid is the lifeblood of drilling operations:

Drilling fluid technology is dominated by three factors : Technical Requirements Economics Environmental Concerns

Functions of Drilling Fluids Drilling Fluid Technology The principal task of the drilling fluid is • To achieve the well objectives effectively & efficiently

Drilling Fluid Design must focus on • Formation Geology • Primary Interval Drilling Objectives • Potential Problems

Drilling Fluids Functions Multi -Functional Chemistry and Engineering Drilling Fluid Criteria
DENSITY REQUIREMENT TECHNICAL
CUTTINGS TRANSPORT
VISCOSITY
FILTRATION CONTROL
HOLE STABILIZATION
CHEMISTRY
ECONOMICS
ENVIRONMENTAL CONSIDERATIONS
WELL CONTROL
DRILLING PERFORMANCE
FORMATION EVALUATION
LUBRICATION
HYDRAULICS
CUTTINGS REMOVAL
WASTE CONTROL

ECONOMICAL TARGET

ENVIRONMENTAL

Drilling Fluids The Key to Successful Drilling Operations

Drilling Fluids Utilizing all Aspects of Chemistry and Engineering CLAY CHEMISTRY

ORGANIC

ANALYTICAL

CORROSION

DRILLING FLUID

INORGANIC

POLYMER

SURF & COLLOID

PHYSICAL

Developing Fluid Technology to Improve Drilling Performance 60 d e g re e s C 120

% Glycol s e p ar ation

100

3% 208

80

10% 208 3% 101 60

10% 101 6% 202

40

20

Wellbore

0 0

5

10

15

20

25

30

35

K C l c o n c e n t r a t io n ( % w t )

Filter Cake Formation

Wellbore Stability - Gauge Hole Low Dilution Rates - Less Waste Reduced Bit Balling - Less Time Thin, low COF cakes - Less Torque

% A ccretion

Understanding Chemical Effects on Drilling Problems

Accretion of cuttings on the BHA

80 70 60 50 40 30 20 10 0

No electrolyte 30ppb NaCl 60ppb NaCl 30ppb TKPP 30ppb CaCl2 30ppb ammonium citrate 30ppb tri-sodium citrate 6ppb gypsum 30ppb KCl

Effect of Electrolyte type and Concentration on Shale accretion

Understanding and Improving Chemical Shale Interactions

Fresh Water

30ppb KCl brine

Fresh Water / STAPLEX* 750 @ 5%

Applying Chemical Shale Inhibition using Silicates

AFTER

BEFORE

Transferring Drilling Fluid Technology to Tunneling

14.50 m 47 ft

Soft clay problems encountered in tunnelling solved by use of drilling fluid chemistry e.g. use of Silicate inhibition

Multiple Drivers for Fluids Research and Development

ENVIRONMENTAL LEADERSHIP

DRILL TO RESERVOIR

RESERVOIR CONNECTIVITY

Lower cost / higher efficiency - shale control - stuck pipe/lubricity - real time measurement

Better productivity - formation damage - effective completions - reservoir imaging

• List the FUNCTIONS of a Drilling Fluid • Which functions are important for Well Control? • What is the primary fluid design parameter when drilling the reservoir? • What are the two primary types of drilling fluids?

How do we determine fluid performance?

Mud Weight Rheology Filtration Control Chemistry Composition

Water Base Fluids Water Base Fluid • Spud mud (Gel mud) • Gel/Polymer Fluid • Lignosulfonate mud • Calcium Base Fluids • Salt-Saturated Muds • KCl Polymer Fluids • Glycol mud • Silicate Mud

Increasingly Inhibitive

Water Based Muds

Water Based Muds • In the early days of the drilling business, freshwater and produced water were used as drilling fluids. • Low annular velocities hindered cuttings from being properly removed from wells - causing drilling problems • In places where hydratable clays were present (termed “mud making” shales) these tended to viscosify the water which improved hole cleaning. • Commercially produced clays - Wyoming Bentonite were added to drilling muds to improve viscosity and fluid loss • Present technology has pushed the performance envelope of drilling fluids by utilizing water soluble polymers and specialty additives to assist the drilling process

• Basic systems are usually converted to more complex systems as a well is deepened, as wellbore temperatures and/or pressures increase and formations dictate • More than one fluid system is typically used when drilling the same well

Increasing Temperature and Pressure

• Many types of waterbased mud systems

Mud System becoming increasingly complex

Water Based Muds Spud Mud Dispersed Systems

Inhibitive Polymer Muds High Temperature Polymer Muds Non-Damaging Drill in Fluids

Benefits

Spud Muds

• Usually simple systems (unweighted) • Cheap • Can be prepared quickly • High viscosity to clean large diameter holes • Viscosity usually easily measured as Funnel Viscosity ( seconds/quart or litre)

Freshwater

+

Bentonite 15-20 ppb

+

Limitations

• Minimal Fluid loss control • Can’t be weighted-up too much • Not suitable for high temperatures • Susceptible to contamination from cement, acid gas and hardness

Caustic Soda 0.5 ppb

=

Spud Mud (Pre-Hydrated Bentonite)

CLAY CHEMISTRY AND CLAYS IN DRILLING FLUIDS

Why Are Clays Important ? • The elements that go to make up clay minerals make up 80% of the mass of the earth (Al 8.1%, Si 27.7%, O 46.6%) • Clays in Rocks : • In shales / mud rocks / clays causing possible drilling problems • In reservoirs giving possible formation damage

• Clays in the Fluid : • Bentonite (gel, sodium montmorillonite) for viscosity and fluid loss control in some WBM • Organophilic bentonite for viscosity and fluid loss control in OBM • Attapulgite for viscosity in salt & very high temperature WBM • Drilled solids help with fluid loss control but can give unwanted viscosity

Chemical Composition of Clays • Physical Properties (structural details) • Fine size • Large surface area • Chemical reactivity of the surface

Building Blocks • There are two basic building units from which all the different clay minerals are constructed : • The Octahedral Layer &Tetrahedral Layers

Clay Structures KEY:

SILICATE SHEET (T)

ALUMINA SHEET (O)

KAOLINITE MONTMORILLONITE AND MICA (INCLUDE ILLITE)

CHLORITE

ATTAPULGITE/SEPIOLITE:

TO or 1:1

+

+

+

TOT or 2:1

TOT : 0 : TOT or 2:1:1

TOT or 2:1

Comparison of Structures Property

Kaolin

Mica

Mont

Attap

Chlorite

Layer type

1:1

2:1

2:1

2:1

2:1:1

Crystal Structure

Sheet

Sheet

Sheet

Sheet

Sheet

Particle Shape

Hexagonal Plate

Extensive Plates

Flakes

Needles

Plates

Particle Size (µ)

0.5 - 5

0.5 - Large Sheets

0.1 - 2

0.1 - 1

0.1 - 5

Surface Area BET-N2-m2/g BET-H2O-m2/g

15 - 20 -

50 - 110 -

30 - 80 200 - 800

200 -

140 -

CEC-meq/100g

3 - 15

10 - 40

80 - 150

15 - 25

10 - 40

Viscosity in Water

Low

Low

High

High

Low

Effects of Salts

Flocculates

Flocculates

Flocculates

Little or none

Flocculates

Charges on Clay Particles • Charges on clays are important as they determine properties such as : • Ion Exchange • Swelling Behavior • Viscosity of Muds • Charges can arise from : • Broken edges on clay particles • Substitution of Ions in the clay structure

Ion Exchange Properties of Clays • The negative charge generated by Isomorphous substitution is balanced by cations held near the clay surface. + +

+ +

• Common charge - balancing cations are Na, K, Ca, Mg; these cations are readily exchangeable in montmorillonite e.g.. KCl solution

+

Na+ Na+

K+

Na+ Na+

K+

K+ K+

• Cation exchange capacity of clay can be measured by methylene blue test (MBT) or chemical analysis of displaced cations

Cation Exchange • Different cations have different attractions for the exchange sites • Assuming all the cation concentrations are the same, the order of increasing replacing power of cations is generally :

Li+ < Na+ < K+ < Mg2+ < Ca2+ < H+ • e.g. : At equal concentrations potassium will displace more sodium than sodium will displace potassium.

• Increasing the concentration of any given cation will increase the probability that it will displace another cation. • e.g. : It is possible for high concentrations of potassium to displace calcium

Hydration of Cations • The properties of the exchange cations have an important influence on clay properties. • Hydration of cations depends on their charge and size. • High charge & small diameter cations are usually most highly hydrated • Low charge & large diameter cations are usually least hydrated

Clay Hydration • The important diameter is the hydrated ionic diameter: H

H δ

-

CATION

δH

H

δ

H

H

Hydrated Ionic Diameter

Dehydrated Ion Diameter A° Na - Sodium K - Potassium Cs - Cesium Mg - Magnesium Ca - Calcium

1.90 2.66 3.34 1.30 1.90

Hydrated Ion Diameter A° 11.2 7.6 7.6 21.6 19.0

Potassium Inhibition

• Potassium Ion Contribution to the Inhibition Process • Charge deficiency is balanced by potassium ions • The Potassium fits neatly in the hexagonal holes made by the silica tetrahedral and securely binds the separate layers together.

Clay Swelling • The most common swelling clay mineral is montmorillonite. • Montmorillonite (bentonite) is used in some drilling fluids to give viscosity and fluid loss control. • Montmorillonite is found in many reactive shales. • Montmorillonite is found in some sandstone (including reservoir sands). • The amount of water taken up by a montmorillonite (& hence the degree of swelling) depends on : • Layer charge of the clay / Ion exchange • Nature of the exchangeable cation • Nature of the external solution

Clay Platelet

Diam eter: < 2 m icrons 1 1, 000 , 000 m . Thickness: ~ 10 Angstrom 10 10 , 000 , 000 , 000 m . Surface Area: ~ 80 m 2 g ~ 18 football fields / kg ~ 19 acres / kg

HYDRATION OF SODIUM MONTMORILLONITE Na+ Na+

±

BROKEN BOND VALENCE

9.8A°

Na+

+ H2O

-

Na+

12.5A°

±

+

A) DRY AIR (Sheet spacing 9.8 A°) B) MOIST AIR (Sheet spacing to 12.5 A°) HYDRATION WATER ALL SHEETS

Na+

FREE SHEETS FROM HYDRATION OR SHEAR

+ H2 O

Na+

Na+

±

Na+

± -

+

Na+

Na+ Na+

17A° 40A°

Na+

C) AQUEOUS SUSPENSION (Sheet spacing 17 A°to 40 A°, Na+ loose sheets from hydration or shear)

±

Clay Swelling : Nature of Exchangeable Cation • Swelling promoted by highly hydrated, low charge exchangeable cations e.g.. Li+ , Na+ • Swelling reduced by high charge, less hydrated cations e.g.. Al3+ • K+ reduces swelling because poorly hydrated even though low charge. • Ca2+, Mg2+ reduces swelling because high charge, though highly hydrated.

Clay Swelling High Salinity Solutions Reduce Clay Swelling relative distribution of particles with a given spacing, % 100

relative distribution of particles with a given spacing, % 100

K+ 78

K+

78

Ca2+

Ca2+

60

Na+

60

25

Na+

25

0

0 0

10

20

30

40

50

space between sheets A

Effect of Low Salt Concentration on space between sheets

0

10

20

30

40

50

space between sheets A Effect of High Salt Concentration on space between sheets

Clay Dispersion / Deflocculation • Clay particles in a fluid can be : • Deflocculated • Flocculated • Aggregated • Dispersed • Degree of dispersion / deflocculation of clays will affect viscosity, fluid loss control and shale inhibition.

Clay Dispersion / Deflocculation There are four basic colloidal states of clay particles in a fluid : Deflocculated. There is an overall repulsive force between the particles. This is done by ensuring all the particles have the same charge. (The particles may be aggregates) Flocculated. There are net attractive forces for the particles and they can associate with each other to form a loose structure. Aggregated. The clay sheets are still attached to each other and hydration has not occurred, or the hydration process has been reversed. Dispersed. This is where the aggregates have all been broken down. The dispersed clays may be flocculated or deflocculated.

Colloidal states

Dispersed and deflocculated

Aggregated but deflocculated

Edge to face flocculated but dispersed

Edge to edge flocculated but dispersed

Edge to face flocculated and aggregated

Edge to edge flocculated and aggregated

Clay Dispersion • Mechanical energy causes DISPERSION of aggregates

MECHANICAL ENERGY

• Leads to increased surface area of solids

MECHANICAL ENERGY

Clay Deflocculation 1. Change pH + -

+

-

-

-

-

-

+

+

+

+

+ - - - +

-

-

+ -

-

-

-

+ +

+

-

-

-

-

-

-

-

-

-

add alkali (OH-) -

add acid (H+)

-

-

-

+

-

-

+ -

-

-

-

< ~ pH 6.5 FLOCCULATED 2. Add chemical deflocculants +

-

-

-

-

-

> ~ pH 8 DEFLOCCULATED

add deflocculant -

-

-

-

-

-

-

-

-

-

-

-

+

+ - - - +

-

-

-

-

-

Clay Deflocculation Chemical energy is used to deflocculate clays

Mechanical Energy

FLOCCULATED

DEFLOCCULATED

The state of deflocculation is determined by surface charges and electrical double layers surrounding particles in suspension

Clay Flocculation

• High Salt Concentration • Polyvalent Cations • Polymeric Flocculants • Low pH

Effect of Clay Dispersion/Deflocculation on Suspension Viscosity To increase viscosity • Increase level of solids • Add high molecular weight viscosifying polymer • Flocculate with calcium or other polyvalent cation • Flocculate with salts • Flocculate with low pH conditions To decrease viscosity • Dilute with water • Disperse with low molecular weight polymers • Remove calcium by chemical treatment • Disperse with higher pH conditions

Clays in Drilling Fluids Clays are added to some water based muds to give : Viscosity : Bentonite / Sepiolite / Attapulgite Fluid loss control : Bentonite Organophilic bentonite added to oil based muds to give viscosity and fluid loss control. Clays entrained in mud as drilled solids. These give viscosity and fluid loss control.

Grades of Bentonite API Non-Treated bentonite Pure sodium montmorillonite. This is the best grade of bentonite API Treated bentonite Is montmorillonite that reaches certain standards on viscosity and filtration control as set out by API. It may be treated with polymers and/or soda ash to attain the API grade. OCMA Bentonite Treated Calcium montmorillonite, commonly used in Europe

Problems Associated with Clay Systems • Calcium ions (from anhydrite/gypsum or cement) will flocculate the system. A deflocculant may be needed, also remove the calcium ion with soda ash or bicarbonate. • Any increase or decrease in the chloride concentration (whether by formation fluids or from drilling salt deposits) will flocculate the system. (This will increase the viscosity and fluid loss. Increase additions of CMC or PAC to deflocculate.) • Viscosity may be reduced with a thinner prior to casing runs the reduce surge pressures. • High viscosities and gel strengths are usually an indication of excessive solids. Reduce solids conc.. by solids removal eqpt. or dilutions. • Prior to drilling out any cement the system should be pretreated with 1/2 ppb sodium bicarbonate. • Note : flocculation due to polymers increases the fluid loss control • Note : flocculation due to higher chlorides or multivalent cations reduces the fluid loss control

CEC - {Cation Exchange Capacity} • Procedure: • 2 - cc’s Mud • 15 - cc’s Hydrogen Peroxide (3%) • 10 - cc’s Distilled Water • 0.5 - cc’s 5N H2SO4 • Boil Gently for 10 minutes. • Dilute to 50 cc’s with distilled water. • Add Methylene blue 1 cc at a time. • (Total cc’s Methylene Blue) X (5) (2 cc’s Mud) = Equivalent Pounds Per Barrel of Bentonite.

CEC - {Cation Exchange Capacity}

CEC - {Cation Exchange Capacity}

Spud Muds • • • • •

Properties

Usually un-weighted (8.34 to 10.5 ppg) Viscosity ( Funnel) usually in the range of 50-100 s/Quart pH 9.0-11.0 Fluid Loss - not controlled PV/YP/ 6 rpm and Gels – not usually measured unless a full circulating system is established for hydrostatic control purposes • Cost - Generally in the range of $2.00-5.00/ bbl

Dispersed Muds Benefits

Limitations

• Relatively simple systems inexpensive • Can convert from Bentonite muds • Slightly higher temperature and density range (Usually weighted with Barite) • Less susceptible to contamination • Improved Fluid Loss Characteristics

Caustic Soda

Freshwater or Seawater

1.0-2.0 ppb

+

(Pre-Hydrated Bentonite)

+

• Generally upper temperature range of 250ºF (although can be extended for HPHT work) • Generally not very inhibitive • pH and Hardness (Ca 2+ and Mg 2+) sensitive • Very sensitive to contamination from cement and electrolytes

Barite as Required For Density

Lignosulphonate PAC or CMC 5.0-8.0 ppb

4.0-6.0 ppb

=

Dispersed Bentonite Mud

Dispersed Muds

Properties

• Can be un-weighted (9.0 ppg) up to 21.0 ppg • Viscosity measured using 6- speed viscometer and Funnel Vis. (for rig trends only) • pH 9.0-11.0 • Fluid Loss controlled with Bentonite, PAC or CMC at low temperatures and thermally stable resins at elevated temperatures • PV – keep as low as possible by controlling low gravity drilled solids (LGS) • YP and 6 RPM reading - used to determine cuttings carrying capacity – see hole cleaning • Cost - Generally in the range of $5.00-15.00/ bbl can be much higher if higher density (barite) is required or at higher temperature because of HT fluid loss requirements

Polymers in Drilling Fluids • Polymers are used in all types of drilling fluids to control fluid properties : • Viscosity • Fluid Loss Control • Flocculation • Deflocculation (Thinning) • Shale Inhibition • Lubricity

• The shape of the polymer will depend on : • What it is sourced from natural products or synthesized from hydrocarbons • Most natural polymers such as starch and cellulose have a saccharide backbone which is bio-degradable – although they have temperature limitations of around 250 degrees F • Synthetic polymers such as PHPA and SPA tend to have a carbon chain backbone which is less biodegradable and more thermally stable

Polymer Shape

Branched

Linear

Crossed linked

Relationship between Function and Structure F u n c t io n

M a in C h a r a c t e r is t ic s

V is c o s it y

H ig h m o le c u la r w e ig h t.

V is c o s it y & G e lla t io n

H ig h m o le c u la r w e ig h t a n d h ig h ly b r a n c h e d s tr u c tu r e o r c r o s s lin k in g a g e n t. H ig h m o le c u la r w e ig h t a n d n o n io n ic o r h ig h ly s u b s titu te d io n ic ty p e . L o w m o le c u la r w e ig h t n e g a tiv e ly c h a r g e d a t a lk a lin e p H le v e ls . H ig h m o le c u la r w e ig h t w ith c h a r g e d g r o u p s to a d s o r b o n to c la y s . H y d r o p h o b ic g r o u p a n d h y d r o p h ilic g r o u p o n s a m e m o le c u le . F o r m c o llo id a l p a r tic le s .

V is c o s it y in s a lt s o lu t io n s

D e f lo c c u la t io n , d is p e r s io n , o r t h in n in g a c t io n F lo c c u la n t

S u rfa c ta n t

F lu id lo s s a d d it iv e

Viscosifying Polymers High molecular weight

solution viscosity

Low molecular weight

polymer concentration

PAC – Poly Anionic Cellulose PAC's are essentially the same as CMC's (carboxy methyl cellulose) except they have a higher degree of substitution (D.S.) • The tolerance for hardness (Ca and Mg) is much higher • Greater solubility in high chloride muds • These variable sized molecular weight polymers therefore can be used as fluid loss reducing agents in a wide variety of aqueous mediums I.e. Freshwater/ Brackish water/ Seawater HiVis,R…….LoVis, LV, UL, SL………..ELV, ESL

Starch • For the starch to exhibit fluid loss control the amylopectin outer shell has to be ruptured in a process known as pre-gelatinization, which releases the water-swellable amylose. This is then further modified to decrease the viscosity and crosslink to increase temperature stability. • The properties may vary with the source of the crude starch eg., potato, corn or tapioca. • The colloidal water-swellable particles will seal pores in the filter cake • A slight increase in viscosity may be noted with starch additions • Starch is biodegradable; a biocide needs to be added when it is used • Starch is effective in saline solutions

Xanthan Gum  Produced by single cell bacteria (Xanthomonas campestris) from sugar fermentation  The gum is extracted, dried and milled. The final mud polymer is usually referred to as XC Polymer  Molecular weight of XC is greater than 1 million  It forms viscous solutions that are highly shear-thinning. This is due to branched rod-like structures that physically interact at low shear rates. Additions of XC increase yield point and gel strength  The polymer is not affected by salt or hardness and is not subject to bacterial degradation

Polymer Muds Freshwater or Seawater/ Brine

XC Polymer 1.0 – 2.0 ppb

Final Polymer Mud

Starch 4.0-6.0 ppb PAC or CMC and/or

+

4.0-6.0 ppb

+

Barite or Calcium Carbonate as Required For Density

=

 In addition to the above additives, which make up the basis of the polymer mud system, it is possible because of its tolerance to contaminants to add a wide variety of other chemicals to perform a vairety of duties. For example  Inhibition – KCl, NaCl, CaCl2,CaSO4 (Gypsum) K2CO3, Glycols, polyamines, and Silicates  Lubricity - Esters, Polyols, Glycerols, surfactants, etc

These addition of these can significantly increase the cost per barrel!

Polymer Muds Advantages Shear thinning, low viscosities at the bit Good hole cleaning Not subject to flocculation Decreased storage space and transport costs Can be used in saline muds Maximum horsepower at bit Can stabilize hydratable shales May be used for high densities Lower solids content Aids in solids control Decreased ECD reduces risk of formation fracture Relatively simple mud system

Polymer Muds Disadvantages Bacterial degradation Temperature limitations Cost, especially if solids control equipment is poor Sensitive to divalent cations Corrosive, oxygen easily entrained Polymers can be depleted by adsorption on drilled solids

Polymer Muds Polymer muds may be made with just polymers and weighting material, or may also have some prehydrated bentonite is added for the following reasons: • Achieving some viscosity and gel strengths, this may be cheaper than deriving all the viscosity from polymers

Engineering Polymer Muds To increase viscosity • Add XC, prehydrated gel or Hi Vis PAC’s, CMC’s and PHPA. (Viscosity from PAC’s , CMC’s and PHPA may be short lived due to removal with solids). • Starch additions will also increase the viscosity slightly

To reduce viscosity: • Reduce solids content by dumping mud and adding new mud. • Reduce solids with solids control equipment. • If viscosity is due to flocculation (indicated by high YP’s, low PV’s and high F/L) add a deflocculant e.g. CMC Lo vis or PAC Lo vis. • A dispersant can be added, but this should be avoided as it may promote formation hydration. It maybe acceptable prior to running the casing.

Improving Fluid Loss • Add PAC lo vis or CMC if viscosity is normal • Add PAC hi vis or CMC hi vis if viscosity is low. • Add Starch if more cost effective than the above. • PHPA has a secondary fluid loss property. It also should be added if increased inhibition is also required.

Solids • Polymer requirements will increase considerably with the volume of drilled solids. the smaller the size of the solids, the greater the surface area, the greater the polymer requirement. • The low gravity solids content should be maintained around 5% by volume, with 6% as a maximum figure. • At elevated temperatures polymers will degrade leading to a loss in functionality and therefore loss of properties. Check the fluid loss of bottoms up samples after trips. This will be a good indication of whether polymer degradation is taking place.

Water Base Fluids Water Base Fluid classification

Inhibitive muds Reduce the chemical interaction between the fluid and the water sensitive formations Use diverse inhibitors to minimize hydration and swelling with reactive clays

Are a combination of polymers - salts glycols - silicates

Increasing inhibition

K+

+

PHPA GLYCOL Silicate Organic Cations Encapsulating Amines

Water Base Fluids Inhibition

Na+ Na+

Ion Exchange Limit Hydration

Na+

Water Na+ Na+ Na +

K+ K+ K+

Water + KCl

Water Base Fluids Polymer mud • Polymers, natural & synthetic are routinely used for: • Viscosity • Filtration control • Shale inhibition • Flocculation

Polymers

• De-flocculation • Lubricity

Shale

Water

Water Base Fluids Polymers • Polymers, natural & synthetic are routinely used for: • Viscosity • Filtration control,

Polymers

• Shale inhibition

Bonding effect

Shale

Water

Water Base Fluids Schematic of Cloud point Mud pits Glycol in solution

Downhole Glycol forms droplets that may block the pores

Temperature decreasing

Cloud Point versus Depth Cloud Point, oC

Clouding out

Depth

Shale Protection Mechanisms Silicate Drilling Fluids Pore network blockage • silica hydrogels / Ca2+ silicate hydrogels completely block shale pores, leading to Pore Pressure Isolation • (and thus wellbore strengthening)

Hydrous Mixed Metal Silicates

SILICATE INTERACTION WITH FORMATION AND DRILL SOLID SURFACES . . . . .. . . . . . . . . . . . . .

FILTER CA KE .DEPOSITION . . . PHYSICAL & CHEMICAL BARRIER TO INVASION

. .. . . .. . .

. .

Si H

o o

H

Si CLAY PLATELETS

NON-CLAY PARTICLES

.

Chemical Shale Inhibition K Silicate Polymer Fluid

Polymer Base Fluid

Cuttings samples: Norske Shell well 3/7 - 6

Silicate Mud performance - Inhibition

WATER BASE MUD

WATER TESTING BASE MUD TESTING

TEMPERATURE

• WATER BASE MUDS

• OIL BASE MUDS

• • • •

• Flowline

Flowline Pits Rheology Fluid loss • API • HTHP

(120oF)

• Pits • Rheology (150oF) • Fluid loss • HTHP

• Electrical Stability

MUD WEIGHT / DENSITY • lbs / gal - Pounds per Gallon. • SG - Specific gravity. • lbs / ft3 - Pounds per Cubic Foot. • psi / 1000 ft - Pounds per Square Inch PER 1000 ft. (Vertical Depth) (a hydrostatic pressure gradient)

VISCOSITY: Internal Resistance to Flow. The Ratio of Shear Stress to Shear Rate. Most Drilling Fluid Viscosity Varies With Shear Rate.

• Funnel Viscosity - Seconds per Quart. Water = 26 seconds +/- ½second

• Plastic Viscosity - Centipoise. (one gram /cm-sec) PV = Φ600 - Φ300

• Apparent Viscosity - Centipoise. (Φ600÷2) • Effective Viscosity - The Measured or Calculated Viscosity at a Given Shear Rate.

• Low Shear Rate Viscosity - Centipoise.

Funnel Viscosity • The timed rate of flow in seconds per quart or seconds per liter. • Begin with 1500 cc’s of mud poured thru a 12 mesh screen. • Time the first 946 cc’s thru a 3/16” opening. • Calibrate The Funnel with water: 26 Seconds per Quart

Funnel Viscosity

RHEOLOGY FANN Model 35 VISCOMETER (6 - Speed VG-Meter) • • • • • •

θ 600 θ 300 θ 200 θ 100 θ6 θ3

θ 600 - θ 300 PV θ 300 - PV YP

API FILTER PRESS CC’S OF FILTRATE COLLECTED: (STATIC) @ • 100 psi • 30 MINUTES • 7.5 in2 # 50 Whatman Paper • Ambient Temperature

FILTER CAKE

FLUID LOSS * API - HTHP • CC’s of FILTRATE collected X 2 (static) • • • •

30 minutes 300°F 3.75 sq. in. #50 Whatman paper 500 psi - Differential Pressure • 600 psi - TOP • 100 psi - BOTTOM (back pressure)

FLUID LOSS * API - HTHP • This is one of several types of units. Good For 300oF on a regular basis. • For higher temperatures a different type unit must be used, and higher pressures (top and bottom) should be used. (Differential pressure should still be 500 psi)

FLUID LOSS * API - HTHP

• This type of unit is used for temperatures above 300oF. • Usually employs Nitrogen pressurization from a big cylinder.

RETORT • % SOLIDS •

Calculated

• % OIL •

Measured

• % WATER •

Measured

SAND CONTENT % By Volume Sand

CEC - {Cation Exchange Capacity} Procedure: • 2 - cc’s Mud • 15 - cc’s Hydrogen Peroxide (3%) • 10 - cc’s Distilled Water • 0.5 - cc’s 5N H2SO4 • Boil Gently for 10 minutes. • Dilute to 50 cc’s with distilled water. • Add Methylene blue 1 cc at a time. • (Total cc’s Methylene Blue) X (5) (2 cc’s Mud) • = Equivalent Pounds Per Barrel of Bentonite.

CEC - {Cation Exchange Capacity} CEC - {Cation Exchange Capacity}

pH • METER (Preferred Method) • STRIPS (General Range)

Pm

Pf

Mf

Cl-

TOTAL HARDNESS ( Ca2+ & Mg2+ )

Calcium (Ca2+)