6.2 Drilling Fluids Part Ii.pdf

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

Section – 2 Oil Base Muds

Oil Base Mud Systems

Invert Emulsion Fluids

Invert Emulsion Fluids Oil Base drilling fluids (OBM) = Invert Emulsion Fluids • Highly inhibitive • Resistant to contaminations (up to a certain level) • Stable at high temperatures and pressures • Provide good lubricity • Non-corrosive and non-toxic using mineral oils (LTOM)

Invert Fluid Applications Development Wells Shale Inhibition HTHP Lubricity Deviated Wells Contaminates, Evaporites, and Acid Gases Spotting Fluids Deepwater

OBM PDC Cuttings

HISTORY of OBM 1920’s - Origin of non-aqueous drilling fluids 1940’s – Diesel Base muds Early 1980’s - Environmental concerns lead to the use of Mineral Oil Fluids Mid 1980’s – Development of low, toxicity, low viscosity oil base systems LVT 1990’s – Development of Synthetic Fluid Technology to meet discharge restrictions Mid 1990’s – Selection of base oils and development of additives to meet HSE and discharge requirements New Millennia Invert Fluid Technology –

Invert Fluid Limitations/Considerations Environmental Discharge Restrictions HSE Requirements Data Interpretation Costs Hydraulics Determinations Increased Risk of Lost Circulation Gas Solubility Logistics

Invert Emulsion Fluid THREE-PHASE SYSTEM - Two immiscible fluids and the solids phase ORGANIC FLUID PHASE - continuous - external phase, base oil with lipophilic liquid product additives WATER - emulsified droplets as internal phase with a salt – typically CaCl2, soluble lime SOLIDS - barite, organophilic clays, drill solids, insoluble additives - fluid loss control products, LCM, etc. (soluble additives)

Invert Emulsion Fluids Continuous Oil Phase A wide variety of oils have been developed to reduce environmental problems • Low Toxic Mineral Oils • Synthetic Oils

CONTINUOUS PHASE OIL BASE SYSTEMS • DIESEL - VERSADRIL • MINERAL - VERSACLEAN • ENHANCED MINERAL OIL (EMO) - VERSAVERT, VERSATHERM, VERSAPRO

SYNTHETIC BASE SYSTEMS • • • • • • •

PAO - NOVADRIL IO - NOVAPLUS LAO – NOVATEC, NOVAPRO ESTER - ECOGREEN PARAFFIN – PARALAND, PARADRIL, PARATHERM, EMS-4000 ETHER, LAB, etc.

Synthetic Drilling Fluid

Definition: …An emulsion drilling fluid with the synthetic fluid as the external (continuous) phase Synthetic base oils are manufactured from materials having a specifically defined composition when compared with mineral oils which are directly derived from petroleum hydrocarbons.

Synthetic Drilling Fluid Factors influencing choice of a synthetic fluid: Toxicity Biodegradation Bioaccumulation Sea Bed Study Performance Health and Safety Drilling Performance

INVERT SYSTEMS – Base Oil Comparisons Sipdrill 2/0: Linear Paraffin SG: 0.7605 cP: 1.76 EDC 95/11:

Mineral Base Oil SG: 0.814 cP: 3.50

EDC 99:

Low Viscosity Mineral Base Oil SG: 0.8114 cP: 2.28

Oil & Synthetic Base Fluids Specific Viscosity, Flash Gravity CST @104 Point F 0.85 3-4 150 Diesel Oil Base Fluid

Pour Aniline Point Point F F 14 149

LTMO

0.80

2-3

212

-0.4

169

ESTER

0.85

5-7

354

-22

77

PAO

0.80

5 -6

302

-76

225

ETHER

0.83

5-6

330

14

104

LAO

0.78

2-3

230

10

~156

IO

0.78

2.9--3.2 2.9

266

-4

~178

LP

0.77

1.76

>212

14

>200

Synthetic Fluid Relative Costs Esters Ethers Olefins:  PAO  LAO  IO Linear Paraffin's

100% 95% 90% 60% 70% 50%

Food grade paraffins are highly refined oils,not synthetics

Synthetic Base Fluids Viscosity Profile vs. Temperature

Apparent Viscosity, cps

25

Ester PAO A 75/25 Ester/IO PAO B 50/50 Ester/IO IO C16C18 LAO C14C16

20

15

10

5

0 40

50

60

70

80

90

100

110 120

T emperature, °F

130

140 150

160

WATER PHASE - Emulsion Droplets BRINE: • CaCl2 - Reduces the activity (Aw) of the water phase Fresh Water NaCl CaCl2

Aw = 1.0

Aw = 1.0 - 0.75 (26% = saturation) Aw = 1.0 - 0.39 (40% = saturation)

• 20-30 %w/w CaCl2 (Common range for oil muds) Aw = 0.836 - 0.641

EMULSIONS Inverse

Direct

Oil Phase

Water Phase

Water

Oil

Oil External Phase

Water External Phase

Oil-wet solids & surfaces

Water-wet solids & surfaces

Desirable for Drilling

Cementing / Stimulation

SOLIDS PHASE Weight Material Barite, Fer-Ox, CaCO3, Ilmenite, Micromax

Organophilic clays Drill Solids Insoluble Additives FLC & LCM Products

Soluble Additives CaCl2, Lime,

CONTINUOUS PHASE - Oil Soluble Lipophilic Liquid Additives: Emulsifiers Wetting Agents Polymer Viscosifiers Organic Thinners

OIL BASE MUD SYSTEMS

OIL BASE MUD PRODUCTS

SURFACTANTS - Surface Active Agents. • Act by Reducing the Interfacial Tension Between Two Liquids or Between a Liquid and a Solid.

Emulsifiers Soaps Wetting Agents The Main Difference Is: The Surfaces They Are Designed To Act Upon And Their HLB Number.

OIL BASE MUD PRODUCTS SURFACTANTS - Surface Active Agents Have a hydrophilic polar head and an organophilic non-polar tail. HYDROPHILIC HEAD (WATER LOVING)

C LOVING) C (OIL C

C C

C C

O

C C

C OH

ORGANOPHILIC TAIL

PRODUCTS SURFACTANTS - Surface Active Agents

HLB Range, function and Products WaterWater-in -oil

Wetting

Emulsifiers

Agents

Detergents OilOil-inin-Water Emulsifiers

Lipophilic 0

3

Hydrophilic 6

9

12

15

18

SURFACTANTS - Surface Active Agents

WATER DROPLET

OIL

SURFACTANTS - Surface Active Agents

INSUFFICIENT EMULSIFIER CONCENTRATION WATER

WATER

DROPLET

DROPLET

COALESCING OF DROPLETS

Wor st

e s a C

SURFACTANTS - Surface Active Agents

- Designed to Oil Wet solids

SOLID’S SURFACE

SURFACTANTS - Surface Active Agents

Contact Angle and Wettability Non-Wetting Liquid

θo > 90º

Contact Angle Oil

Wetting Liquid

θw < 90º

Water SOLID “WATER WET”

Case 1: Solid is preferentially water wet

SURFACTANTS - Surface Active Agents Contact Angle and Wettability Non-Wetting Liquid

θw > 90º

Wetting Liquid

θo < 90º Oil

Water

SOLID “ OIL WET”

Case 2: Solid is preferentially oil wet

OIL BASE MUD PRODUCTS

VISCOSIFIERS: Organophilic Clays Organic Polymers

OIL BASE MUD PRODUCTS

THINNERS: • BASE OIL • VERSATHIN - (Physical deflocculant) • Temporary fix for high viscosity due to solids • WILL NOT THIN VERSA-HRP • WILL THIN VERSAMOD • For overtreatment use clay viscosifier • VERSAWET • VERSACOAT • NOVATHIN

OIL BASE MUD PRODUCTS HTHP - FLUID LOSS REDUCERS: Gilsonite base Polymer Amine treated lignite Oleic Acid Dimer/trimer blend - oleic acid Gilsonite

OIL BASE MUD PRODUCTS Additional Invert Additives: LIME - Ca(OH)2 HOT LIME / QUICK LIME - CaO CALCIUM CHLORIDE - CaCl2

Optional Internal Phase – Water Activity Other Salts:

Calcium Chloride - CaCl2 Sodium Chloride - NaCl Calcium Bromide - CaBr2 Sodium Formate - NaCOOH Potassium Formate - KCOOH Cesium Formate – CsCOOH Organic:

Glycol

%w/w vs Density 2.50

DENSITY

2.00

1.50

1.00

Sodium Formate Potassium Formate Cesium Formate

0.50

Sodium Chloride Potassium Chloride Calcium Chloride

0.00 0%

10 %

20 %

30 %

40 %

50 %

%w/w SALT

60 %

70 %

80 %

90 %

Brine Activity - Aw The following equations can be used to calculate Brine Activity:

CaCl2:

Aw = 1 + 0.001264834 (%CaCl2) – 0.0006366891 (%CaCl2)2 + 5.877758 x 10-6 (%CaCl2)3

NaCl: Aw = 1 + 0.004767582 (%NaCl) – 0.0001694205 (%NaCl)2

MgCl2:

Aw = 1 + 0.002444242 (%MgCl2) – 0.0004608654 (% MgCl2)2

KCl: Aw = 1 + 0.003973135 (%KCl) – 0.0000747175 (% KCl)2

1 0.9 0.8

Water Activity

0.7 0.6 0.5 0.4 Sodium Formate 0.3

Potassium Formate Sodium Chloride

0.2

Potassium Chloride Calcium Chloride

0.1 0

0%

10 %

20 %

30 %

40 % %w/w SALT

50 %

60 %

70 %

80 %

SHALE STABILIZATION OF OIL BASE MUDS

Shale Stabilization Mechanism: Oil-Wetting of the Formation Osmotic Stabilization

Osmosis: The movement of water molecules from an area of high concentration to an area of low concentration. Cell membranes are completely permeable to water, therefore, the environment the cell is exposed to can have a dramatic effect on the cell.

Osmosis Hypertonic Solutions: contain a high concentration of solute relative to another solution (e.g. the cell's cytoplasm). When a cell is placed in a hypertonic solution, the water diffuses out of the cell, causing the cell to shrivel.

Hypotonic Solutions: contain a low concentration of solute relative to another solution (e.g. the cell's cytoplasm). When a cell is placed in a hypotonic solution, the water diffuses into the cell, causing the cell to swell and possibly explode.

Isotonic Solutions: contain the same concentration of solute as an another solution (e.g. the cell's cytoplasm). When a cell is placed in an isotonic solution, the water diffuses into and out of the cell at the same rate. The fluid that surrounds the body cells is isotonic.

Shale Stabilization

PROPERTIES & TESTING OF OIL BASE MUDS

Standard API Tests for Inverts • • • • • •

Mud weight (lb/gal - kg/m3) Funnel Viscosity (sec/liter) or (sec/quart) Rheology @ 50oC, “65oC”, 80oC HTHP @ 150°C or bottom hole temperature Retort (% oil/synthetic, %water, %solids) Pom, Psm (total cc’s of .1N H2SO4 three titrations) • Excess lime Pom (cc’s) x 3.7 = kg/m3 • Chlorides (whole mud) mg/l • Electrical Stability (ES) @ 50oC

Mud Weight

Mud Rheology

Rheology of Invert Emulsions Test at 120°, 150°, and 180oF or as operator requests Run VG meter at 300 rpm while heating sample After completing Rheology, check the heat cup for barite settling

HTHP of Invert Emulsions HTHP reported as 2 X filtrate cc’s/30 minutes) Run at 300oF (150oC) unless otherwise instructed Filtrate of conventional formulations should not contain water Filtrates of new muds may contain a small amount of water until they have been sheared through the bit Check filter cake for barite settling

HTHP of Invert Emulsions

Retort Analysis of Inverts

Retort Analysis of Inverts Accuracy! Retort allows us to determine: • • • •

% Solids % Oil or Synthetic fluid % Water Salt content

Watch for trends and major changes

Titrations for Invert Emulsion Standard titrations: Alkalinity - Pom, Psm Chlorides – Cl - (whole mud) Must use whole mud - (2 cc’s) (filtrate is Oil / Synthetic fluid) Mix mud with solvent to break the emulsion Dilute sample with distilled water and add indicator

Titrations for Invert Emulsion

Electrical Stability of Inverts

Electrical Stability of Inverts • Electrical stability is a relative value! • Electrical stability related to emulsion stability, %water, water droplet size, temperature... • Electrical stability of new muds will be low until sheared through the bit. • Check at 50oC/120ºF • Meters • Operator ramped - (old style) (reading is doubled) • Self ramping digital - (read directly) - API APPROVED

Water Activity 1

Invert Mud System

0.9 0.8

Water Activity

0.7 0.6 0.5 0.4 Sodium Formate 0.3

Potassium Formate Sodium Chloride

0.2

Potassium Chloride Calcium Chloride

0.1 0

0%

10 %

20 %

30 %

40 % %w/w SALT

Shale

50 %

60 %

70 %

80 %

Water Activity

Gas Solubility

DISPLACEMENTS Meet, communicate, organize Condition displaced mud to lowest rheology and displacing fluid with higher rheology Do not begin until all displacing fluid is on location. Spacer to cover 500’ to 1,000’ of annulus Pump at a rate approaching turbulence Do Not Stop circulating once displacement has started Rotate / Reciprocate Pipe

DISPLACEMENTS (Cont.) Place bit near bottom as oil mud clears. Change screens. Add Wetting agent. Monitor with Stability meter.

Invert Systems – Solids Management

Rig Preparation Solids Removal Equipment Disposal

Shaker Performance

”OLD GENERATION”

”NEW GENERATION”

SHAKER TECHNOLOGY

SHAKER TECHNOLOGY

PROBLEMS WITH OIL BASE MUD

Problems: Oil / Synthetics • • • • • • • • • •

Insufficient Viscosity Excessive Viscosity Solids Contamination Salt Water Flows Water Wet Solids Carbon Dioxide - CO2 Hydrogen Sulfide - H2S Massive Salts and Salt Stringers Barite Sag / Settling Lost Circulation

Insufficient Viscosity Barite Settling Inadequate Hole Cleaning Treatment: • Add Viscosifiers - Clay, Polymer, Rheology Modifier • Add Water (Brine) • Shear Mud

Excessive Viscosity Solids - High, Fines, Water-Wet High Water Content High Temperature Instability Acid Gases Water-Wet Solids Over-Treatment with Viscosifiers Treatment: • Remove / Dilute - Solids, Water Content. • Add - Emulsifier, Wetting Agent,Versathin, Lime, Increase mud weight

Solids Contamination High Viscosity Thick Filter Cake Treatment: • Finer mesh shaker screen • Tandem centrifuges • Dilute with base fluids and add emulsifier • Wetting agent

Salt Water Flows Increased %water Decreased oil:water ratio High viscosity Water wet solids Lower Electrical Stability Water in HTHP filtrate Treatment: • Add Oil to restore OWR • Emulsifier and lime • Wetting agent for weight up or water wet solids • Barite to adjust weight and stop influx

Water Wet Solids Increased viscosity Decreased Electrical Stability Grainy appearance Settling Shale shaker screen blinding Test Treatment: • If brine phase salt saturated with divalent salt, add fresh water • Wetting agent

Carbon Dioxide CO2 Decrease in POM Decrease in lime content Decrease in Electrical Stability Treatment: • Add lime to maintain an excess, use caution to control excess lime in ester based fluids • Increase mud weight to control influx

Hydrogen Sulfide, H2S Sulfides detected with Garrett Gas Train Decrease in POM Decrease in lime content Decrease in Electrical Stability Mud may turn black Treatment: • Inorganic zinc scavenger (ZnO, Ironite Sponge, SafeScav HS) • Maintain excess lime content • Increase mud weight to control influx

Massive Salts & Salt Stringers Salts are insoluble, may become a low gravity solids problem Formation CaCl2 and MgCl2 may cause water wetting of solids Sticking from plastic flow (not differential) • Displace annulus from bit to free point with fresh water spot

Barite Sag / Settling Sag, uneven mud weights on bottoms up after trips Treatment: • • • •

Increase Low Shear Rate Viscosity with clay Settling, static conditions and pits Normal, increase Low Shear Rate Viscosity Excess wetting agent (hard pack), add organophilic clay and polymer. Do not add wetting agent. • Water wet barite indicated by tests - add wetting agent

Barite Precipitation – SAG

Variation Variation in in mud mud density density ... ...

Invert Emulsion Fluid Mud Weight Out (lb/gal) 19 Mud Weight In = 17 lb/gal Samples from Shaker Underflow 18.5 18 Pressurized Balance

17.5 17

Baseline Weight

16.5 16 15.5

0

25

50

75 100 125 Circulating Time (min)

150

175

M-I/Mobil Study (1990) - Barite Sag Primarily a dynamic settling problem Minimized by elevating LSRV and gels Affected by annular velocity and pipe movement Requires proper mud treatment and operational procedures

M-I/Mobil Study (1990) - Barite Sag Can lead to common drilling, cementing, logging problems Can occur in directional wells in all types of weighted muds Must be systematically checked on trip reports

Boycott Settling

Clarified Fluid Suspension Zone Sag (Sedim ent) Bed Slum p

Sag Chronology Mud sags under dynamic conditions Sag slumps under any flow conditions Mud sags and slumps faster at intermediate angles Sag slumps faster while pumping slowly or tripping Circulate low MW, then high MW, then regular MW

Lost Circulation Compressibility increases density at depth and the likelihood of fracturing formation LCM such as Cellophane and cane fiber can break emulsion Treatment: • VERSAPAC • Mica, MIX-II, nut hulls • Reverse gunk squeeze (organophilic clay in water - No Cement) • FORM-A-SET • FORM-A-PLUG

Invert Emulsion Fluids Key Hydraulics Issues • Lost Circulation • Downhole Hydrostatic Pressure • Rheology and Pressure Loss under Temperature and Pressure • Pump-Pressure Variation • Temperature Profile • Surge/Swab Pressure • Hole Cleaning

Basic Concepts  Virtual Rheology • best available rheological data for this drilling fluid  Virtual Hydraulics • analysis by finite difference (variable downhole properties)  Visual Rheology and Visual Hydraulics • “real-time”, downhole predictions and display

Virtual Rheology Fann 34

HTHP Field

Viscometers

Conventional

Fann 35A

Rig

Virtual

Data

Hydraulics

Rheology Fann 50

Fann 75 HTHP Lab

Huxley-Bertram

Viscometers

Virtual Hydraulics Equivalent Static Density • PVT (Pressure, Volume, Temperature) Data • Mud Composition, Base Fluid • Temperature Profile, Well Profile

Equivalent Circulating Density • Mud Rheology under Temperature and Pressure • Temperature Profile • Well Profile, Well Geometry, Eccentricity

Pump Pressure • Mud Rheology under Temperature and Pressure • Laminar/Turbulent Friction Factors • Well Profile, Well Geometry

Fann 75

Virtual Rotary Drilling Hydraulics

Virtual Rotary Drilling Hydraulics SPECIAL EXPL & PROD CO

Snapshot

MD

PROPOSED S.T. 63 SOUTH TIMBALIER BLK 63

16025 ft

TVD

15224 ft

Date

09-19-1995

Virtual Hydraulics

OFFSHORE, LOUISIANA Depth (ft)

Equiv Mud Wt (lb/gal) 10.2

10.4

PV and YP 10.6

10.8

0

10

20

Temp (°F) 30

40

50

0

200

Velocity (ft/min) 400

0

200

400 DRILLING FLUID

1000

2000

Mud Type

NOVAPLUS

Mud Weight

10.2 lb/gal

Test Temp

120 °F SYSTEM DATA

3000 Flow Rate

430 gal/min

4000

Nozzles

5000

Drill String

2894

Bit

751

Annulus

284

Surface Equip

55

10.05 4600

14-12-12-12

PRESSURE LOSSES (psi)

6000

7000

Total System

3985 ECD's (lb/gal)

8000

9000

Casing Shoe

10.63

Total Depth

10.64

VRDH - Version 1.00

10000

11000

12000

Pressure Loss (%) 0

25

13000

9.875 16025

14000

Drill String

15000

Bit

16000 Annulus

15224 17000

ECD

PV

ESD

YP

50

75

100

Virtual Hydraulics Summary

Features • Uses best available data for THIS mud to determine variable downhole rheological properties • Considers effects of temperature and pressure on downhole density

Benefits • Accurately predicts pump pressures, ESD, and ECD for synthetic-base muds • Minimizes potential for drilling problems • Increases confidence when planning and running syntheticbased muds

INVERT EMULSION FLUIDS

SUMMARY

Summary Fluids Systems Products and Functions Formulations Properties Testing Problems

OBM Applications OBM/SBM are used in almost every continent with excellent success Best available drilling fluid for shale inhibition and shale stabilization OBM/SBM are used for high temperature / high pressure wells, due to excellent temperature stability and solids tolerance (400+ oF and 21 lb/gal)

• What is an Emulsion and why is it important for in formulating a drilling fluid? • What is the role of Salinity in an OBM? • Describe the effect of Pressure & Temperature on the density of an OBM. • What is the role of the Wetting Agent? • Name 3 primary applications for an invert emulsion fluid.

• List the 5 primary measurements which characterize a drilling fluid. • What differences exist between a WBM and an OBM?? Advantages? Disadvantages? …of each?

Invert Fluid Advantages Wellbore Stabilization (Shales & Salts) Lubrication Properties Temperature Stability Tolerance to Contaminants Economics – Re-Usable Corrosion Control Drillability

Selection Criteria Invert Emulsion Fluids Long Reactive Shale Sections Highly Deviated Wells High Temperature Environments Salt Sections Contamination

Invert Emulsion Fluids ...set the Industry Performance Standards for.. Optimum Wellbore Stability Fast Drilling Rates High Return on Investment Long Lasting Environmental Impact Poor Health and Handling

Problems Invert Fluids Rheology & Density Control Barite Sag Lost Circulation Environmental Compliance (disposal) HES (handling) concerns Economics Well Control (Gas Solubility) Elastomer Compatability